]> git.sesse.net Git - bcachefs-tools-debian/blobdiff - libbcachefs/io.c
Update bcachefs sources to a8115093df bcachefs: Fix divide by zero in rebalance_work()
[bcachefs-tools-debian] / libbcachefs / io.c
index 039dd044153ecf36123ad571a0baafb36eb0e6c4..3c614c864b6eef698c9dac8ebc1884d7f4a61bed 100644 (file)
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0
 /*
  * Some low level IO code, and hacks for various block layer limitations
  *
  */
 
 #include "bcachefs.h"
-#include "alloc.h"
+#include "alloc_background.h"
+#include "alloc_foreground.h"
+#include "bkey_buf.h"
 #include "bset.h"
 #include "btree_update.h"
 #include "buckets.h"
 #include "checksum.h"
 #include "compress.h"
 #include "clock.h"
+#include "data_update.h"
 #include "debug.h"
+#include "disk_groups.h"
+#include "ec.h"
 #include "error.h"
-#include "extents.h"
+#include "extent_update.h"
+#include "inode.h"
 #include "io.h"
 #include "journal.h"
 #include "keylist.h"
 #include "move.h"
+#include "nocow_locking.h"
+#include "rebalance.h"
+#include "subvolume.h"
+#include "super.h"
 #include "super-io.h"
+#include "trace.h"
 
 #include <linux/blkdev.h>
+#include <linux/prefetch.h>
 #include <linux/random.h>
+#include <linux/sched/mm.h>
 
-#include <trace/events/bcachefs.h>
+const char *bch2_blk_status_to_str(blk_status_t status)
+{
+       if (status == BLK_STS_REMOVED)
+               return "device removed";
+       return blk_status_to_str(status);
+}
+
+#ifndef CONFIG_BCACHEFS_NO_LATENCY_ACCT
+
+static bool bch2_target_congested(struct bch_fs *c, u16 target)
+{
+       const struct bch_devs_mask *devs;
+       unsigned d, nr = 0, total = 0;
+       u64 now = local_clock(), last;
+       s64 congested;
+       struct bch_dev *ca;
+
+       if (!target)
+               return false;
+
+       rcu_read_lock();
+       devs = bch2_target_to_mask(c, target) ?:
+               &c->rw_devs[BCH_DATA_user];
+
+       for_each_set_bit(d, devs->d, BCH_SB_MEMBERS_MAX) {
+               ca = rcu_dereference(c->devs[d]);
+               if (!ca)
+                       continue;
+
+               congested = atomic_read(&ca->congested);
+               last = READ_ONCE(ca->congested_last);
+               if (time_after64(now, last))
+                       congested -= (now - last) >> 12;
+
+               total += max(congested, 0LL);
+               nr++;
+       }
+       rcu_read_unlock();
+
+       return bch2_rand_range(nr * CONGESTED_MAX) < total;
+}
+
+static inline void bch2_congested_acct(struct bch_dev *ca, u64 io_latency,
+                                      u64 now, int rw)
+{
+       u64 latency_capable =
+               ca->io_latency[rw].quantiles.entries[QUANTILE_IDX(1)].m;
+       /* ideally we'd be taking into account the device's variance here: */
+       u64 latency_threshold = latency_capable << (rw == READ ? 2 : 3);
+       s64 latency_over = io_latency - latency_threshold;
+
+       if (latency_threshold && latency_over > 0) {
+               /*
+                * bump up congested by approximately latency_over * 4 /
+                * latency_threshold - we don't need much accuracy here so don't
+                * bother with the divide:
+                */
+               if (atomic_read(&ca->congested) < CONGESTED_MAX)
+                       atomic_add(latency_over >>
+                                  max_t(int, ilog2(latency_threshold) - 2, 0),
+                                  &ca->congested);
+
+               ca->congested_last = now;
+       } else if (atomic_read(&ca->congested) > 0) {
+               atomic_dec(&ca->congested);
+       }
+}
+
+void bch2_latency_acct(struct bch_dev *ca, u64 submit_time, int rw)
+{
+       atomic64_t *latency = &ca->cur_latency[rw];
+       u64 now = local_clock();
+       u64 io_latency = time_after64(now, submit_time)
+               ? now - submit_time
+               : 0;
+       u64 old, new, v = atomic64_read(latency);
+
+       do {
+               old = v;
+
+               /*
+                * If the io latency was reasonably close to the current
+                * latency, skip doing the update and atomic operation - most of
+                * the time:
+                */
+               if (abs((int) (old - io_latency)) < (old >> 1) &&
+                   now & ~(~0U << 5))
+                       break;
+
+               new = ewma_add(old, io_latency, 5);
+       } while ((v = atomic64_cmpxchg(latency, old, new)) != old);
 
-static inline void __bio_inc_remaining(struct bio *bio)
+       bch2_congested_acct(ca, io_latency, now, rw);
+
+       __bch2_time_stats_update(&ca->io_latency[rw], submit_time, now);
+}
+
+#else
+
+static bool bch2_target_congested(struct bch_fs *c, u16 target)
 {
-       bio_set_flag(bio, BIO_CHAIN);
-       smp_mb__before_atomic();
-       atomic_inc(&bio->__bi_remaining);
+       return false;
 }
 
+#endif
+
 /* Allocate, free from mempool: */
 
 void bch2_bio_free_pages_pool(struct bch_fs *c, struct bio *bio)
 {
+       struct bvec_iter_all iter;
        struct bio_vec *bv;
-       unsigned i;
 
-       bio_for_each_segment_all(bv, bio, i)
+       bio_for_each_segment_all(bv, bio, iter)
                if (bv->bv_page != ZERO_PAGE(0))
                        mempool_free(bv->bv_page, &c->bio_bounce_pages);
        bio->bi_vcnt = 0;
 }
 
-static void bch2_bio_alloc_page_pool(struct bch_fs *c, struct bio *bio,
-                                   bool *using_mempool)
+static struct page *__bio_alloc_page_pool(struct bch_fs *c, bool *using_mempool)
 {
-       struct bio_vec *bv = &bio->bi_io_vec[bio->bi_vcnt++];
+       struct page *page;
 
        if (likely(!*using_mempool)) {
-               bv->bv_page = alloc_page(GFP_NOIO);
-               if (unlikely(!bv->bv_page)) {
+               page = alloc_page(GFP_NOFS);
+               if (unlikely(!page)) {
                        mutex_lock(&c->bio_bounce_pages_lock);
                        *using_mempool = true;
                        goto pool_alloc;
@@ -62,630 +172,1629 @@ static void bch2_bio_alloc_page_pool(struct bch_fs *c, struct bio *bio,
                }
        } else {
 pool_alloc:
-               bv->bv_page = mempool_alloc(&c->bio_bounce_pages, GFP_NOIO);
+               page = mempool_alloc(&c->bio_bounce_pages, GFP_NOFS);
        }
 
-       bv->bv_len = PAGE_SIZE;
-       bv->bv_offset = 0;
+       return page;
 }
 
 void bch2_bio_alloc_pages_pool(struct bch_fs *c, struct bio *bio,
-                             size_t bytes)
+                              size_t size)
 {
        bool using_mempool = false;
 
-       bio->bi_iter.bi_size = bytes;
+       while (size) {
+               struct page *page = __bio_alloc_page_pool(c, &using_mempool);
+               unsigned len = min_t(size_t, PAGE_SIZE, size);
 
-       while (bio->bi_vcnt < DIV_ROUND_UP(bytes, PAGE_SIZE))
-               bch2_bio_alloc_page_pool(c, bio, &using_mempool);
+               BUG_ON(!bio_add_page(bio, page, len, 0));
+               size -= len;
+       }
 
        if (using_mempool)
                mutex_unlock(&c->bio_bounce_pages_lock);
 }
 
-/* Bios with headers */
+/* Extent update path: */
 
-void bch2_submit_wbio_replicas(struct bch_write_bio *wbio, struct bch_fs *c,
-                              const struct bkey_i *k)
+int bch2_sum_sector_overwrites(struct btree_trans *trans,
+                              struct btree_iter *extent_iter,
+                              struct bkey_i *new,
+                              bool *usage_increasing,
+                              s64 *i_sectors_delta,
+                              s64 *disk_sectors_delta)
 {
-       struct bkey_s_c_extent e = bkey_i_to_s_c_extent(k);
-       const struct bch_extent_ptr *ptr;
-       struct bch_write_bio *n;
-       struct bch_dev *ca;
-
-       BUG_ON(c->opts.nochanges);
+       struct bch_fs *c = trans->c;
+       struct btree_iter iter;
+       struct bkey_s_c old;
+       unsigned new_replicas = bch2_bkey_replicas(c, bkey_i_to_s_c(new));
+       bool new_compressed = bch2_bkey_sectors_compressed(bkey_i_to_s_c(new));
+       int ret = 0;
 
-       wbio->split = false;
-       wbio->c = c;
+       *usage_increasing       = false;
+       *i_sectors_delta        = 0;
+       *disk_sectors_delta     = 0;
 
-       extent_for_each_ptr(e, ptr) {
-               ca = c->devs[ptr->dev];
+       bch2_trans_copy_iter(&iter, extent_iter);
 
-               if (ptr + 1 < &extent_entry_last(e)->ptr) {
-                       n = to_wbio(bio_clone_fast(&wbio->bio, GFP_NOIO,
-                                                  &ca->replica_set));
+       for_each_btree_key_upto_continue_norestart(iter,
+                               new->k.p, BTREE_ITER_SLOTS, old, ret) {
+               s64 sectors = min(new->k.p.offset, old.k->p.offset) -
+                       max(bkey_start_offset(&new->k),
+                           bkey_start_offset(old.k));
 
-                       n->bio.bi_end_io        = wbio->bio.bi_end_io;
-                       n->bio.bi_private       = wbio->bio.bi_private;
-                       n->c                    = c;
-                       n->orig                 = &wbio->bio;
-                       n->bounce               = false;
-                       n->split                = true;
-                       n->put_bio              = true;
-                       n->bio.bi_opf           = wbio->bio.bi_opf;
-                       __bio_inc_remaining(n->orig);
-               } else {
-                       n = wbio;
-               }
+               *i_sectors_delta += sectors *
+                       (bkey_extent_is_allocation(&new->k) -
+                        bkey_extent_is_allocation(old.k));
 
-               if (!journal_flushes_device(ca))
-                       n->bio.bi_opf |= REQ_FUA;
+               *disk_sectors_delta += sectors * bch2_bkey_nr_ptrs_allocated(bkey_i_to_s_c(new));
+               *disk_sectors_delta -= new->k.p.snapshot == old.k->p.snapshot
+                       ? sectors * bch2_bkey_nr_ptrs_fully_allocated(old)
+                       : 0;
 
-               n->ca                   = ca;
-               n->submit_time_us       = local_clock_us();
-               n->bio.bi_iter.bi_sector = ptr->offset;
+               if (!*usage_increasing &&
+                   (new->k.p.snapshot != old.k->p.snapshot ||
+                    new_replicas > bch2_bkey_replicas(c, old) ||
+                    (!new_compressed && bch2_bkey_sectors_compressed(old))))
+                       *usage_increasing = true;
 
-               if (likely(percpu_ref_tryget(&ca->io_ref))) {
-                       n->have_io_ref          = true;
-                       n->bio.bi_bdev          = ca->disk_sb.bdev;
-                       generic_make_request(&n->bio);
-               } else {
-                       n->have_io_ref          = false;
-                       bcache_io_error(c, &n->bio, "device has been removed");
-                       bio_endio(&n->bio);
-               }
+               if (bkey_ge(old.k->p, new->k.p))
+                       break;
        }
-}
-
-/* IO errors */
-
-/* Writes */
 
-static struct workqueue_struct *index_update_wq(struct bch_write_op *op)
-{
-       return op->alloc_reserve == RESERVE_MOVINGGC
-               ? op->c->copygc_wq
-               : op->c->wq;
+       bch2_trans_iter_exit(trans, &iter);
+       return ret;
 }
 
-static void __bch2_write(struct closure *);
-
-static void bch2_write_done(struct closure *cl)
+static inline int bch2_extent_update_i_size_sectors(struct btree_trans *trans,
+                                                   struct btree_iter *extent_iter,
+                                                   u64 new_i_size,
+                                                   s64 i_sectors_delta)
 {
-       struct bch_write_op *op = container_of(cl, struct bch_write_op, cl);
+       struct btree_iter iter;
+       struct bkey_i *k;
+       struct bkey_i_inode_v3 *inode;
+       unsigned inode_update_flags = BTREE_UPDATE_NOJOURNAL;
+       int ret;
 
-       BUG_ON(!(op->flags & BCH_WRITE_DONE));
+       k = bch2_bkey_get_mut_noupdate(trans, &iter, BTREE_ID_inodes,
+                             SPOS(0,
+                                  extent_iter->pos.inode,
+                                  extent_iter->snapshot),
+                             BTREE_ITER_CACHED);
+       ret = PTR_ERR_OR_ZERO(k);
+       if (unlikely(ret))
+               return ret;
+
+       if (unlikely(k->k.type != KEY_TYPE_inode_v3)) {
+               k = bch2_inode_to_v3(trans, k);
+               ret = PTR_ERR_OR_ZERO(k);
+               if (unlikely(ret))
+                       goto err;
+       }
 
-       if (!op->error && (op->flags & BCH_WRITE_FLUSH))
-               op->error = bch2_journal_error(&op->c->journal);
+       inode = bkey_i_to_inode_v3(k);
 
-       bch2_disk_reservation_put(op->c, &op->res);
-       percpu_ref_put(&op->c->writes);
-       bch2_keylist_free(&op->insert_keys, op->inline_keys);
-       closure_return(cl);
-}
+       if (!(le64_to_cpu(inode->v.bi_flags) & BCH_INODE_I_SIZE_DIRTY) &&
+           new_i_size > le64_to_cpu(inode->v.bi_size)) {
+               inode->v.bi_size = cpu_to_le64(new_i_size);
+               inode_update_flags = 0;
+       }
 
-static u64 keylist_sectors(struct keylist *keys)
-{
-       struct bkey_i *k;
-       u64 ret = 0;
+       if (i_sectors_delta) {
+               le64_add_cpu(&inode->v.bi_sectors, i_sectors_delta);
+               inode_update_flags = 0;
+       }
 
-       for_each_keylist_key(keys, k)
-               ret += k->k.size;
+       if (inode->k.p.snapshot != iter.snapshot) {
+               inode->k.p.snapshot = iter.snapshot;
+               inode_update_flags = 0;
+       }
 
+       ret = bch2_trans_update(trans, &iter, &inode->k_i,
+                               BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE|
+                               inode_update_flags);
+err:
+       bch2_trans_iter_exit(trans, &iter);
        return ret;
 }
 
-static int bch2_write_index_default(struct bch_write_op *op)
+int bch2_extent_update(struct btree_trans *trans,
+                      subvol_inum inum,
+                      struct btree_iter *iter,
+                      struct bkey_i *k,
+                      struct disk_reservation *disk_res,
+                      u64 new_i_size,
+                      s64 *i_sectors_delta_total,
+                      bool check_enospc)
 {
-       struct keylist *keys = &op->insert_keys;
-       struct btree_iter iter;
+       struct bpos next_pos;
+       bool usage_increasing;
+       s64 i_sectors_delta = 0, disk_sectors_delta = 0;
        int ret;
 
-       bch2_btree_iter_init_intent(&iter, op->c, BTREE_ID_EXTENTS,
-               bkey_start_pos(&bch2_keylist_front(keys)->k));
-
-       ret = bch2_btree_insert_list_at(&iter, keys, &op->res,
-                                      NULL, op_journal_seq(op),
-                                      BTREE_INSERT_NOFAIL);
-       bch2_btree_iter_unlock(&iter);
+       /*
+        * This traverses us the iterator without changing iter->path->pos to
+        * search_key() (which is pos + 1 for extents): we want there to be a
+        * path already traversed at iter->pos because
+        * bch2_trans_extent_update() will use it to attempt extent merging
+        */
+       ret = __bch2_btree_iter_traverse(iter);
+       if (ret)
+               return ret;
+
+       ret = bch2_extent_trim_atomic(trans, iter, k);
+       if (ret)
+               return ret;
+
+       next_pos = k->k.p;
+
+       ret = bch2_sum_sector_overwrites(trans, iter, k,
+                       &usage_increasing,
+                       &i_sectors_delta,
+                       &disk_sectors_delta);
+       if (ret)
+               return ret;
+
+       if (disk_res &&
+           disk_sectors_delta > (s64) disk_res->sectors) {
+               ret = bch2_disk_reservation_add(trans->c, disk_res,
+                                       disk_sectors_delta - disk_res->sectors,
+                                       !check_enospc || !usage_increasing
+                                       ? BCH_DISK_RESERVATION_NOFAIL : 0);
+               if (ret)
+                       return ret;
+       }
 
-       return ret;
+       /*
+        * Note:
+        * We always have to do an inode update - even when i_size/i_sectors
+        * aren't changing - for fsync to work properly; fsync relies on
+        * inode->bi_journal_seq which is updated by the trigger code:
+        */
+       ret =   bch2_extent_update_i_size_sectors(trans, iter,
+                                                 min(k->k.p.offset << 9, new_i_size),
+                                                 i_sectors_delta) ?:
+               bch2_trans_update(trans, iter, k, 0) ?:
+               bch2_trans_commit(trans, disk_res, NULL,
+                               BTREE_INSERT_NOCHECK_RW|
+                               BTREE_INSERT_NOFAIL);
+       if (unlikely(ret))
+               return ret;
+
+       if (i_sectors_delta_total)
+               *i_sectors_delta_total += i_sectors_delta;
+       bch2_btree_iter_set_pos(iter, next_pos);
+       return 0;
 }
 
-/**
- * bch_write_index - after a write, update index to point to new data
- */
-static void bch2_write_index(struct closure *cl)
+/* Overwrites whatever was present with zeroes: */
+int bch2_extent_fallocate(struct btree_trans *trans,
+                         subvol_inum inum,
+                         struct btree_iter *iter,
+                         unsigned sectors,
+                         struct bch_io_opts opts,
+                         s64 *i_sectors_delta,
+                         struct write_point_specifier write_point)
 {
-       struct bch_write_op *op = container_of(cl, struct bch_write_op, cl);
-       struct bch_fs *c = op->c;
-       struct keylist *keys = &op->insert_keys;
-       unsigned i;
+       struct bch_fs *c = trans->c;
+       struct disk_reservation disk_res = { 0 };
+       struct closure cl;
+       struct open_buckets open_buckets = { 0 };
+       struct bkey_s_c k;
+       struct bkey_buf old, new;
+       unsigned sectors_allocated = 0;
+       bool have_reservation = false;
+       bool unwritten = opts.nocow &&
+           c->sb.version >= bcachefs_metadata_version_unwritten_extents;
+       int ret;
 
-       op->flags |= BCH_WRITE_LOOPED;
+       bch2_bkey_buf_init(&old);
+       bch2_bkey_buf_init(&new);
+       closure_init_stack(&cl);
 
-       if (!bch2_keylist_empty(keys)) {
-               u64 sectors_start = keylist_sectors(keys);
-               int ret = op->index_update_fn(op);
+       k = bch2_btree_iter_peek_slot(iter);
+       ret = bkey_err(k);
+       if (ret)
+               return ret;
 
-               BUG_ON(keylist_sectors(keys) && !ret);
+       sectors = min_t(u64, sectors, k.k->p.offset - iter->pos.offset);
 
-               op->written += sectors_start - keylist_sectors(keys);
+       if (!have_reservation) {
+               unsigned new_replicas =
+                       max(0, (int) opts.data_replicas -
+                           (int) bch2_bkey_nr_ptrs_fully_allocated(k));
+               /*
+                * Get a disk reservation before (in the nocow case) calling
+                * into the allocator:
+                */
+               ret = bch2_disk_reservation_get(c, &disk_res, sectors, new_replicas, 0);
+               if (unlikely(ret))
+                       goto err;
 
-               if (ret) {
-                       __bcache_io_error(c, "btree IO error %i", ret);
-                       op->error = ret;
-               }
+               bch2_bkey_buf_reassemble(&old, c, k);
        }
 
-       for (i = 0; i < ARRAY_SIZE(op->open_buckets); i++)
-               if (op->open_buckets[i]) {
-                       bch2_open_bucket_put(c,
-                                            c->open_buckets +
-                                            op->open_buckets[i]);
-                       op->open_buckets[i] = 0;
-               }
+       if (have_reservation) {
+               if (!bch2_extents_match(k, bkey_i_to_s_c(old.k)))
+                       goto err;
 
-       if (!(op->flags & BCH_WRITE_DONE))
-               continue_at(cl, __bch2_write, op->io_wq);
+               bch2_key_resize(&new.k->k, sectors);
+       } else if (!unwritten) {
+               struct bkey_i_reservation *reservation;
 
-       if (!op->error && (op->flags & BCH_WRITE_FLUSH)) {
-               bch2_journal_flush_seq_async(&c->journal,
-                                            *op_journal_seq(op),
-                                            cl);
-               continue_at(cl, bch2_write_done, index_update_wq(op));
+               bch2_bkey_buf_realloc(&new, c, sizeof(*reservation) / sizeof(u64));
+               reservation = bkey_reservation_init(new.k);
+               reservation->k.p = iter->pos;
+               bch2_key_resize(&reservation->k, sectors);
+               reservation->v.nr_replicas = opts.data_replicas;
        } else {
-               continue_at_nobarrier(cl, bch2_write_done, NULL);
+               struct bkey_i_extent *e;
+               struct bch_devs_list devs_have;
+               struct write_point *wp;
+               struct bch_extent_ptr *ptr;
+
+               devs_have.nr = 0;
+
+               bch2_bkey_buf_realloc(&new, c, BKEY_EXTENT_U64s_MAX);
+
+               e = bkey_extent_init(new.k);
+               e->k.p = iter->pos;
+
+               ret = bch2_alloc_sectors_start_trans(trans,
+                               opts.foreground_target,
+                               false,
+                               write_point,
+                               &devs_have,
+                               opts.data_replicas,
+                               opts.data_replicas,
+                               BCH_WATERMARK_normal, 0, &cl, &wp);
+               if (bch2_err_matches(ret, BCH_ERR_operation_blocked))
+                       ret = -BCH_ERR_transaction_restart_nested;
+               if (ret)
+                       goto err;
+
+               sectors = min(sectors, wp->sectors_free);
+               sectors_allocated = sectors;
+
+               bch2_key_resize(&e->k, sectors);
+
+               bch2_open_bucket_get(c, wp, &open_buckets);
+               bch2_alloc_sectors_append_ptrs(c, wp, &e->k_i, sectors, false);
+               bch2_alloc_sectors_done(c, wp);
+
+               extent_for_each_ptr(extent_i_to_s(e), ptr)
+                       ptr->unwritten = true;
        }
-}
 
-/**
- * bch_write_discard - discard range of keys
- *
- * Used to implement discard, and to handle when writethrough write hits
- * a write error on the cache device.
- */
-static void bch2_write_discard(struct closure *cl)
-{
-       struct bch_write_op *op = container_of(cl, struct bch_write_op, cl);
-       struct bio *bio = &op->bio->bio;
-       struct bpos end = op->pos;
+       have_reservation = true;
 
-       end.offset += bio_sectors(bio);
+       ret = bch2_extent_update(trans, inum, iter, new.k, &disk_res,
+                                0, i_sectors_delta, true);
+err:
+       if (!ret && sectors_allocated)
+               bch2_increment_clock(c, sectors_allocated, WRITE);
+
+       bch2_open_buckets_put(c, &open_buckets);
+       bch2_disk_reservation_put(c, &disk_res);
+       bch2_bkey_buf_exit(&new, c);
+       bch2_bkey_buf_exit(&old, c);
+
+       if (closure_nr_remaining(&cl) != 1) {
+               bch2_trans_unlock(trans);
+               closure_sync(&cl);
+       }
 
-       op->error = bch2_discard(op->c, op->pos, end, op->version,
-                               &op->res, NULL, NULL);
+       return ret;
 }
 
 /*
- * Convert extents to be inserted to discards after an error:
+ * Returns -BCH_ERR_transacton_restart if we had to drop locks:
  */
-static void bch2_write_io_error(struct closure *cl)
+int bch2_fpunch_at(struct btree_trans *trans, struct btree_iter *iter,
+                  subvol_inum inum, u64 end,
+                  s64 *i_sectors_delta)
 {
-       struct bch_write_op *op = container_of(cl, struct bch_write_op, cl);
+       struct bch_fs *c        = trans->c;
+       unsigned max_sectors    = KEY_SIZE_MAX & (~0 << c->block_bits);
+       struct bpos end_pos = POS(inum.inum, end);
+       struct bkey_s_c k;
+       int ret = 0, ret2 = 0;
+       u32 snapshot;
+
+       while (!ret ||
+              bch2_err_matches(ret, BCH_ERR_transaction_restart)) {
+               struct disk_reservation disk_res =
+                       bch2_disk_reservation_init(c, 0);
+               struct bkey_i delete;
 
-       if (op->flags & BCH_WRITE_DISCARD_ON_ERROR) {
-               struct bkey_i *src = bch2_keylist_front(&op->insert_keys);
-               struct bkey_i *dst = bch2_keylist_front(&op->insert_keys);
+               if (ret)
+                       ret2 = ret;
+
+               bch2_trans_begin(trans);
+
+               ret = bch2_subvolume_get_snapshot(trans, inum.subvol, &snapshot);
+               if (ret)
+                       continue;
+
+               bch2_btree_iter_set_snapshot(iter, snapshot);
 
                /*
-                * Our data write just errored, which means we've got a bunch
-                * of keys to insert that point to data that wasn't
-                * successfully written.
-                *
-                * We don't have to insert those keys but we still have to
-                * invalidate that region of the cache - so, if we just strip
-                * off all the pointers from the keys we'll accomplish just
-                * that.
+                * peek_upto() doesn't have ideal semantics for extents:
                 */
+               k = bch2_btree_iter_peek_upto(iter, end_pos);
+               if (!k.k)
+                       break;
 
-               while (src != op->insert_keys.top) {
-                       struct bkey_i *n = bkey_next(src);
-
-                       set_bkey_val_u64s(&src->k, 0);
-                       src->k.type = KEY_TYPE_DISCARD;
-                       bkey_copy(dst, src);
+               ret = bkey_err(k);
+               if (ret)
+                       continue;
 
-                       dst = bkey_next(dst);
-                       src = n;
-               }
+               bkey_init(&delete.k);
+               delete.k.p = iter->pos;
 
-               op->insert_keys.top = dst;
-               op->flags |= BCH_WRITE_DISCARD;
-       } else {
-               /* TODO: We could try to recover from this. */
-               while (!bch2_keylist_empty(&op->insert_keys))
-                       bch2_keylist_pop_front(&op->insert_keys);
+               /* create the biggest key we can */
+               bch2_key_resize(&delete.k, max_sectors);
+               bch2_cut_back(end_pos, &delete);
 
-               op->error = -EIO;
-               op->flags |= BCH_WRITE_DONE;
+               ret = bch2_extent_update(trans, inum, iter, &delete,
+                               &disk_res, 0, i_sectors_delta, false);
+               bch2_disk_reservation_put(c, &disk_res);
        }
 
-       bch2_write_index(cl);
+       return ret ?: ret2;
 }
 
-static void bch2_write_endio(struct bio *bio)
+int bch2_fpunch(struct bch_fs *c, subvol_inum inum, u64 start, u64 end,
+               s64 *i_sectors_delta)
 {
-       struct closure *cl = bio->bi_private;
-       struct bch_write_op *op = container_of(cl, struct bch_write_op, cl);
-       struct bch_write_bio *wbio = to_wbio(bio);
-       struct bch_fs *c = wbio->c;
-       struct bio *orig = wbio->orig;
-       struct bch_dev *ca = wbio->ca;
-
-       if (bch2_dev_nonfatal_io_err_on(bio->bi_error, ca,
-                                      "data write"))
-               set_closure_fn(cl, bch2_write_io_error, index_update_wq(op));
-
-       if (wbio->have_io_ref)
-               percpu_ref_put(&ca->io_ref);
-
-       if (bio->bi_error && orig)
-               orig->bi_error = bio->bi_error;
+       struct btree_trans trans;
+       struct btree_iter iter;
+       int ret;
 
-       if (wbio->bounce)
-               bch2_bio_free_pages_pool(c, bio);
+       bch2_trans_init(&trans, c, BTREE_ITER_MAX, 1024);
+       bch2_trans_iter_init(&trans, &iter, BTREE_ID_extents,
+                            POS(inum.inum, start),
+                            BTREE_ITER_INTENT);
 
-       if (wbio->put_bio)
-               bio_put(bio);
+       ret = bch2_fpunch_at(&trans, &iter, inum, end, i_sectors_delta);
 
-       if (orig)
-               bio_endio(orig);
-       else
-               closure_put(cl);
-}
+       bch2_trans_iter_exit(&trans, &iter);
+       bch2_trans_exit(&trans);
 
-static struct nonce extent_nonce(struct bversion version,
-                                unsigned nonce,
-                                unsigned uncompressed_size,
-                                unsigned compression_type)
-{
-       return (struct nonce) {{
-               [0] = cpu_to_le32((nonce                << 12) |
-                                 (uncompressed_size    << 22)),
-               [1] = cpu_to_le32(version.lo),
-               [2] = cpu_to_le32(version.lo >> 32),
-               [3] = cpu_to_le32(version.hi|
-                                 (compression_type << 24))^BCH_NONCE_EXTENT,
-       }};
-}
+       if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
+               ret = 0;
 
-static void init_append_extent(struct bch_write_op *op,
-                              unsigned compressed_size,
-                              unsigned uncompressed_size,
-                              unsigned compression_type,
-                              unsigned nonce,
-                              struct bch_csum csum, unsigned csum_type,
-                              struct open_bucket *ob)
-{
-       struct bkey_i_extent *e = bkey_extent_init(op->insert_keys.top);
-
-       op->pos.offset += uncompressed_size;
-       e->k.p = op->pos;
-       e->k.size = uncompressed_size;
-       e->k.version = op->version;
-       bkey_extent_set_cached(&e->k, op->flags & BCH_WRITE_CACHED);
-
-       bch2_extent_crc_append(e, compressed_size,
-                             uncompressed_size,
-                             compression_type,
-                             nonce, csum, csum_type);
-
-       bch2_alloc_sectors_append_ptrs(op->c, e, op->nr_replicas,
-                                     ob, compressed_size);
-
-       bkey_extent_set_cached(&e->k, (op->flags & BCH_WRITE_CACHED));
-       bch2_keylist_push(&op->insert_keys);
+       return ret;
 }
 
-static int bch2_write_extent(struct bch_write_op *op,
-                           struct open_bucket *ob,
-                           struct bio *orig)
+static int bch2_write_index_default(struct bch_write_op *op)
 {
        struct bch_fs *c = op->c;
-       struct bio *bio;
-       struct bch_write_bio *wbio;
-       unsigned key_to_write_offset = op->insert_keys.top_p -
-               op->insert_keys.keys_p;
-       struct bkey_i *key_to_write;
-       unsigned csum_type = op->csum_type;
-       unsigned compression_type = op->compression_type;
+       struct bkey_buf sk;
+       struct keylist *keys = &op->insert_keys;
+       struct bkey_i *k = bch2_keylist_front(keys);
+       struct btree_trans trans;
+       struct btree_iter iter;
+       subvol_inum inum = {
+               .subvol = op->subvol,
+               .inum   = k->k.p.inode,
+       };
        int ret;
 
-       /* don't refetch csum type/compression type */
-       barrier();
+       BUG_ON(!inum.subvol);
 
-       /* Need to decompress data? */
-       if ((op->flags & BCH_WRITE_DATA_COMPRESSED) &&
-           (crc_uncompressed_size(NULL, &op->crc) != op->size ||
-            crc_compressed_size(NULL, &op->crc) > ob->sectors_free)) {
-               int ret;
+       bch2_bkey_buf_init(&sk);
+       bch2_trans_init(&trans, c, BTREE_ITER_MAX, 1024);
+
+       do {
+               bch2_trans_begin(&trans);
+
+               k = bch2_keylist_front(keys);
+               bch2_bkey_buf_copy(&sk, c, k);
 
-               ret = bch2_bio_uncompress_inplace(c, orig, op->size, op->crc);
+               ret = bch2_subvolume_get_snapshot(&trans, inum.subvol,
+                                                 &sk.k->k.p.snapshot);
+               if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
+                       continue;
                if (ret)
-                       return ret;
+                       break;
 
-               op->flags &= ~BCH_WRITE_DATA_COMPRESSED;
-       }
-
-       if (op->flags & BCH_WRITE_DATA_COMPRESSED) {
-               init_append_extent(op,
-                                  crc_compressed_size(NULL, &op->crc),
-                                  crc_uncompressed_size(NULL, &op->crc),
-                                  op->crc.compression_type,
-                                  op->crc.nonce,
-                                  op->crc.csum,
-                                  op->crc.csum_type,
-                                  ob);
-
-               bio                     = orig;
-               wbio                    = to_wbio(bio);
-               wbio->orig              = NULL;
-               wbio->bounce            = false;
-               wbio->put_bio           = false;
-               ret                     = 0;
-       } else if (csum_type != BCH_CSUM_NONE ||
-                  compression_type != BCH_COMPRESSION_NONE) {
-               /* all units here in bytes */
-               unsigned total_output = 0, output_available =
-                       min(ob->sectors_free << 9, orig->bi_iter.bi_size);
-               unsigned crc_nonce = bch2_csum_type_is_encryption(csum_type)
-                       ? op->nonce : 0;
-               struct bch_csum csum;
-               struct nonce nonce;
+               bch2_trans_iter_init(&trans, &iter, BTREE_ID_extents,
+                                    bkey_start_pos(&sk.k->k),
+                                    BTREE_ITER_SLOTS|BTREE_ITER_INTENT);
 
-               bio = bio_alloc_bioset(GFP_NOIO,
-                                      DIV_ROUND_UP(output_available, PAGE_SIZE),
-                                      &c->bio_write);
-               /*
-                * XXX: can't use mempool for more than
-                * BCH_COMPRESSED_EXTENT_MAX worth of pages
-                */
-               bch2_bio_alloc_pages_pool(c, bio, output_available);
+               ret = bch2_extent_update(&trans, inum, &iter, sk.k,
+                                        &op->res,
+                                        op->new_i_size, &op->i_sectors_delta,
+                                        op->flags & BCH_WRITE_CHECK_ENOSPC);
+               bch2_trans_iter_exit(&trans, &iter);
 
-               /* copy WRITE_SYNC flag */
-               bio->bi_opf             = orig->bi_opf;
-               wbio                    = to_wbio(bio);
-               wbio->orig              = NULL;
-               wbio->bounce            = true;
-               wbio->put_bio           = true;
-
-               do {
-                       unsigned fragment_compression_type = compression_type;
-                       size_t dst_len, src_len;
-
-                       bch2_bio_compress(c, bio, &dst_len,
-                                        orig, &src_len,
-                                        &fragment_compression_type);
-
-                       BUG_ON(!dst_len || dst_len > bio->bi_iter.bi_size);
-                       BUG_ON(!src_len || src_len > orig->bi_iter.bi_size);
-                       BUG_ON(dst_len & (block_bytes(c) - 1));
-                       BUG_ON(src_len & (block_bytes(c) - 1));
-
-                       swap(bio->bi_iter.bi_size, dst_len);
-                       nonce = extent_nonce(op->version,
-                                            crc_nonce,
-                                            src_len >> 9,
-                                            fragment_compression_type),
-
-                       bch2_encrypt_bio(c, csum_type, nonce, bio);
-
-                       csum = bch2_checksum_bio(c, csum_type, nonce, bio);
-                       swap(bio->bi_iter.bi_size, dst_len);
-
-                       init_append_extent(op,
-                                          dst_len >> 9, src_len >> 9,
-                                          fragment_compression_type,
-                                          crc_nonce, csum, csum_type, ob);
-
-                       total_output += dst_len;
-                       bio_advance(bio, dst_len);
-                       bio_advance(orig, src_len);
-               } while (bio->bi_iter.bi_size &&
-                        orig->bi_iter.bi_size &&
-                        !bch2_keylist_realloc(&op->insert_keys,
-                                             op->inline_keys,
-                                             ARRAY_SIZE(op->inline_keys),
-                                             BKEY_EXTENT_U64s_MAX));
-
-               BUG_ON(total_output > output_available);
-
-               memset(&bio->bi_iter, 0, sizeof(bio->bi_iter));
-               bio->bi_iter.bi_size = total_output;
+               if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
+                       continue;
+               if (ret)
+                       break;
 
-               /*
-                * Free unneeded pages after compressing:
-                */
-               while (bio->bi_vcnt * PAGE_SIZE >
-                      round_up(bio->bi_iter.bi_size, PAGE_SIZE))
-                       mempool_free(bio->bi_io_vec[--bio->bi_vcnt].bv_page,
-                                    &c->bio_bounce_pages);
+               if (bkey_ge(iter.pos, k->k.p))
+                       bch2_keylist_pop_front(&op->insert_keys);
+               else
+                       bch2_cut_front(iter.pos, k);
+       } while (!bch2_keylist_empty(keys));
 
-               ret = orig->bi_iter.bi_size != 0;
-       } else {
-               bio = bio_next_split(orig, ob->sectors_free, GFP_NOIO,
-                                    &c->bio_write);
+       bch2_trans_exit(&trans);
+       bch2_bkey_buf_exit(&sk, c);
 
-               wbio                    = to_wbio(bio);
-               wbio->orig              = NULL;
-               wbio->bounce            = false;
-               wbio->put_bio           = bio != orig;
+       return ret;
+}
 
-               init_append_extent(op, bio_sectors(bio), bio_sectors(bio),
-                                  compression_type, 0,
-                                  (struct bch_csum) { 0 }, csum_type, ob);
+/* Writes */
 
-               ret = bio != orig;
-       }
+void bch2_submit_wbio_replicas(struct bch_write_bio *wbio, struct bch_fs *c,
+                              enum bch_data_type type,
+                              const struct bkey_i *k,
+                              bool nocow)
+{
+       struct bkey_ptrs_c ptrs = bch2_bkey_ptrs_c(bkey_i_to_s_c(k));
+       const struct bch_extent_ptr *ptr;
+       struct bch_write_bio *n;
+       struct bch_dev *ca;
+
+       BUG_ON(c->opts.nochanges);
+
+       bkey_for_each_ptr(ptrs, ptr) {
+               BUG_ON(ptr->dev >= BCH_SB_MEMBERS_MAX ||
+                      !c->devs[ptr->dev]);
+
+               ca = bch_dev_bkey_exists(c, ptr->dev);
 
-       bio->bi_end_io  = bch2_write_endio;
-       bio->bi_private = &op->cl;
-       bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
+               if (to_entry(ptr + 1) < ptrs.end) {
+                       n = to_wbio(bio_alloc_clone(NULL, &wbio->bio,
+                                               GFP_NOFS, &ca->replica_set));
 
-       closure_get(bio->bi_private);
+                       n->bio.bi_end_io        = wbio->bio.bi_end_io;
+                       n->bio.bi_private       = wbio->bio.bi_private;
+                       n->parent               = wbio;
+                       n->split                = true;
+                       n->bounce               = false;
+                       n->put_bio              = true;
+                       n->bio.bi_opf           = wbio->bio.bi_opf;
+                       bio_inc_remaining(&wbio->bio);
+               } else {
+                       n = wbio;
+                       n->split                = false;
+               }
 
-       /* might have done a realloc... */
+               n->c                    = c;
+               n->dev                  = ptr->dev;
+               n->have_ioref           = nocow || bch2_dev_get_ioref(ca,
+                                       type == BCH_DATA_btree ? READ : WRITE);
+               n->nocow                = nocow;
+               n->submit_time          = local_clock();
+               n->inode_offset         = bkey_start_offset(&k->k);
+               n->bio.bi_iter.bi_sector = ptr->offset;
 
-       key_to_write = (void *) (op->insert_keys.keys_p + key_to_write_offset);
+               if (likely(n->have_ioref)) {
+                       this_cpu_add(ca->io_done->sectors[WRITE][type],
+                                    bio_sectors(&n->bio));
 
-       bch2_check_mark_super(c, key_to_write, false);
+                       bio_set_dev(&n->bio, ca->disk_sb.bdev);
 
-       bch2_submit_wbio_replicas(to_wbio(bio), c, key_to_write);
-       return ret;
+                       if (type != BCH_DATA_btree && unlikely(c->opts.no_data_io)) {
+                               bio_endio(&n->bio);
+                               continue;
+                       }
+
+                       submit_bio(&n->bio);
+               } else {
+                       n->bio.bi_status        = BLK_STS_REMOVED;
+                       bio_endio(&n->bio);
+               }
+       }
 }
 
-static void __bch2_write(struct closure *cl)
+static void __bch2_write(struct bch_write_op *);
+
+static void bch2_write_done(struct closure *cl)
 {
        struct bch_write_op *op = container_of(cl, struct bch_write_op, cl);
        struct bch_fs *c = op->c;
-       struct bio *bio = &op->bio->bio;
-       unsigned open_bucket_nr = 0;
-       struct open_bucket *b;
-       int ret;
 
-       memset(op->open_buckets, 0, sizeof(op->open_buckets));
-
-       if (op->flags & BCH_WRITE_DISCARD) {
-               op->flags |= BCH_WRITE_DONE;
-               bch2_write_discard(cl);
-               bio_put(bio);
-               continue_at(cl, bch2_write_done, index_update_wq(op));
-       }
+       EBUG_ON(op->open_buckets.nr);
 
-       /*
-        * Journal writes are marked REQ_PREFLUSH; if the original write was a
-        * flush, it'll wait on the journal write.
-        */
-       bio->bi_opf &= ~(REQ_PREFLUSH|REQ_FUA);
+       bch2_time_stats_update(&c->times[BCH_TIME_data_write], op->start_time);
+       bch2_disk_reservation_put(c, &op->res);
 
-       do {
-               EBUG_ON(bio->bi_iter.bi_sector != op->pos.offset);
-               EBUG_ON(!bio_sectors(bio));
+       if (!(op->flags & BCH_WRITE_MOVE))
+               bch2_write_ref_put(c, BCH_WRITE_REF_write);
+       bch2_keylist_free(&op->insert_keys, op->inline_keys);
 
-               if (open_bucket_nr == ARRAY_SIZE(op->open_buckets))
-                       continue_at(cl, bch2_write_index, index_update_wq(op));
+       EBUG_ON(cl->parent);
+       closure_debug_destroy(cl);
+       if (op->end_io)
+               op->end_io(op);
+}
 
-               /* for the device pointers and 1 for the chksum */
-               if (bch2_keylist_realloc(&op->insert_keys,
-                                       op->inline_keys,
-                                       ARRAY_SIZE(op->inline_keys),
-                                       BKEY_EXTENT_U64s_MAX))
-                       continue_at(cl, bch2_write_index, index_update_wq(op));
-
-               b = bch2_alloc_sectors_start(c, op->wp,
-                       op->nr_replicas,
-                       c->opts.data_replicas_required,
-                       op->alloc_reserve,
-                       (op->flags & BCH_WRITE_ALLOC_NOWAIT) ? NULL : cl);
-               EBUG_ON(!b);
-
-               if (unlikely(IS_ERR(b))) {
-                       if (unlikely(PTR_ERR(b) != -EAGAIN)) {
-                               ret = PTR_ERR(b);
-                               goto err;
-                       }
+static noinline int bch2_write_drop_io_error_ptrs(struct bch_write_op *op)
+{
+       struct keylist *keys = &op->insert_keys;
+       struct bch_extent_ptr *ptr;
+       struct bkey_i *src, *dst = keys->keys, *n;
 
-                       /*
-                        * If we already have some keys, must insert them first
-                        * before allocating another open bucket. We only hit
-                        * this case if open_bucket_nr > 1.
-                        */
-                       if (!bch2_keylist_empty(&op->insert_keys))
-                               continue_at(cl, bch2_write_index,
-                                           index_update_wq(op));
+       for (src = keys->keys; src != keys->top; src = n) {
+               n = bkey_next(src);
 
-                       /*
-                        * If we've looped, we're running out of a workqueue -
-                        * not the bch2_write() caller's context - and we don't
-                        * want to block the workqueue:
-                        */
-                       if (op->flags & BCH_WRITE_LOOPED)
-                               continue_at(cl, __bch2_write, op->io_wq);
+               if (bkey_extent_is_direct_data(&src->k)) {
+                       bch2_bkey_drop_ptrs(bkey_i_to_s(src), ptr,
+                                           test_bit(ptr->dev, op->failed.d));
 
-                       /*
-                        * Otherwise, we do want to block the caller on alloc
-                        * failure instead of letting it queue up more and more
-                        * writes:
-                        * XXX: this technically needs a try_to_freeze() -
-                        * except that that's not safe because caller may have
-                        * issued other IO... hmm..
-                        */
-                       closure_sync(cl);
-                       continue;
+                       if (!bch2_bkey_nr_ptrs(bkey_i_to_s_c(src)))
+                               return -EIO;
                }
 
-               BUG_ON(b - c->open_buckets == 0 ||
-                      b - c->open_buckets > U8_MAX);
-               op->open_buckets[open_bucket_nr++] = b - c->open_buckets;
-
-               ret = bch2_write_extent(op, b, bio);
+               if (dst != src)
+                       memmove_u64s_down(dst, src, src->k.u64s);
+               dst = bkey_next(dst);
+       }
 
-               bch2_alloc_sectors_done(c, op->wp, b);
+       keys->top = dst;
+       return 0;
+}
 
-               if (ret < 0)
-                       goto err;
-       } while (ret);
+/**
+ * bch_write_index - after a write, update index to point to new data
+ */
+static void __bch2_write_index(struct bch_write_op *op)
+{
+       struct bch_fs *c = op->c;
+       struct keylist *keys = &op->insert_keys;
+       struct bkey_i *k;
+       unsigned dev;
+       int ret = 0;
+
+       if (unlikely(op->flags & BCH_WRITE_IO_ERROR)) {
+               ret = bch2_write_drop_io_error_ptrs(op);
+               if (ret)
+                       goto err;
+       }
+
+       /*
+        * probably not the ideal place to hook this in, but I don't
+        * particularly want to plumb io_opts all the way through the btree
+        * update stack right now
+        */
+       for_each_keylist_key(keys, k)
+               bch2_rebalance_add_key(c, bkey_i_to_s_c(k), &op->opts);
+
+       if (!bch2_keylist_empty(keys)) {
+               u64 sectors_start = keylist_sectors(keys);
+
+               ret = !(op->flags & BCH_WRITE_MOVE)
+                       ? bch2_write_index_default(op)
+                       : bch2_data_update_index_update(op);
+
+               BUG_ON(bch2_err_matches(ret, BCH_ERR_transaction_restart));
+               BUG_ON(keylist_sectors(keys) && !ret);
+
+               op->written += sectors_start - keylist_sectors(keys);
+
+               if (ret && !bch2_err_matches(ret, EROFS)) {
+                       struct bkey_i *k = bch2_keylist_front(&op->insert_keys);
+
+                       bch_err_inum_offset_ratelimited(c,
+                               k->k.p.inode, k->k.p.offset << 9,
+                               "write error while doing btree update: %s",
+                               bch2_err_str(ret));
+               }
 
+               if (ret)
+                       goto err;
+       }
+out:
+       /* If some a bucket wasn't written, we can't erasure code it: */
+       for_each_set_bit(dev, op->failed.d, BCH_SB_MEMBERS_MAX)
+               bch2_open_bucket_write_error(c, &op->open_buckets, dev);
+
+       bch2_open_buckets_put(c, &op->open_buckets);
+       return;
+err:
+       keys->top = keys->keys;
+       op->error = ret;
        op->flags |= BCH_WRITE_DONE;
-       continue_at(cl, bch2_write_index, index_update_wq(op));
+       goto out;
+}
+
+static inline void __wp_update_state(struct write_point *wp, enum write_point_state state)
+{
+       if (state != wp->state) {
+               u64 now = ktime_get_ns();
+
+               if (wp->last_state_change &&
+                   time_after64(now, wp->last_state_change))
+                       wp->time[wp->state] += now - wp->last_state_change;
+               wp->state = state;
+               wp->last_state_change = now;
+       }
+}
+
+static inline void wp_update_state(struct write_point *wp, bool running)
+{
+       enum write_point_state state;
+
+       state = running                  ? WRITE_POINT_running :
+               !list_empty(&wp->writes) ? WRITE_POINT_waiting_io
+                                        : WRITE_POINT_stopped;
+
+       __wp_update_state(wp, state);
+}
+
+static void bch2_write_index(struct closure *cl)
+{
+       struct bch_write_op *op = container_of(cl, struct bch_write_op, cl);
+       struct write_point *wp = op->wp;
+       struct workqueue_struct *wq = index_update_wq(op);
+       unsigned long flags;
+
+       if ((op->flags & BCH_WRITE_DONE) &&
+           (op->flags & BCH_WRITE_MOVE))
+               bch2_bio_free_pages_pool(op->c, &op->wbio.bio);
+
+       spin_lock_irqsave(&wp->writes_lock, flags);
+       if (wp->state == WRITE_POINT_waiting_io)
+               __wp_update_state(wp, WRITE_POINT_waiting_work);
+       list_add_tail(&op->wp_list, &wp->writes);
+       spin_unlock_irqrestore (&wp->writes_lock, flags);
+
+       queue_work(wq, &wp->index_update_work);
+}
+
+static inline void bch2_write_queue(struct bch_write_op *op, struct write_point *wp)
+{
+       op->wp = wp;
+
+       if (wp->state == WRITE_POINT_stopped) {
+               spin_lock_irq(&wp->writes_lock);
+               __wp_update_state(wp, WRITE_POINT_waiting_io);
+               spin_unlock_irq(&wp->writes_lock);
+       }
+}
+
+void bch2_write_point_do_index_updates(struct work_struct *work)
+{
+       struct write_point *wp =
+               container_of(work, struct write_point, index_update_work);
+       struct bch_write_op *op;
+
+       while (1) {
+               spin_lock_irq(&wp->writes_lock);
+               op = list_first_entry_or_null(&wp->writes, struct bch_write_op, wp_list);
+               if (op)
+                       list_del(&op->wp_list);
+               wp_update_state(wp, op != NULL);
+               spin_unlock_irq(&wp->writes_lock);
+
+               if (!op)
+                       break;
+
+               op->flags |= BCH_WRITE_IN_WORKER;
+
+               __bch2_write_index(op);
+
+               if (!(op->flags & BCH_WRITE_DONE))
+                       __bch2_write(op);
+               else
+                       bch2_write_done(&op->cl);
+       }
+}
+
+static void bch2_write_endio(struct bio *bio)
+{
+       struct closure *cl              = bio->bi_private;
+       struct bch_write_op *op         = container_of(cl, struct bch_write_op, cl);
+       struct bch_write_bio *wbio      = to_wbio(bio);
+       struct bch_write_bio *parent    = wbio->split ? wbio->parent : NULL;
+       struct bch_fs *c                = wbio->c;
+       struct bch_dev *ca              = bch_dev_bkey_exists(c, wbio->dev);
+
+       if (bch2_dev_inum_io_err_on(bio->bi_status, ca,
+                                   op->pos.inode,
+                                   wbio->inode_offset << 9,
+                                   "data write error: %s",
+                                   bch2_blk_status_to_str(bio->bi_status))) {
+               set_bit(wbio->dev, op->failed.d);
+               op->flags |= BCH_WRITE_IO_ERROR;
+       }
+
+       if (wbio->nocow)
+               set_bit(wbio->dev, op->devs_need_flush->d);
+
+       if (wbio->have_ioref) {
+               bch2_latency_acct(ca, wbio->submit_time, WRITE);
+               percpu_ref_put(&ca->io_ref);
+       }
+
+       if (wbio->bounce)
+               bch2_bio_free_pages_pool(c, bio);
+
+       if (wbio->put_bio)
+               bio_put(bio);
+
+       if (parent)
+               bio_endio(&parent->bio);
+       else
+               closure_put(cl);
+}
+
+static void init_append_extent(struct bch_write_op *op,
+                              struct write_point *wp,
+                              struct bversion version,
+                              struct bch_extent_crc_unpacked crc)
+{
+       struct bkey_i_extent *e;
+
+       op->pos.offset += crc.uncompressed_size;
+
+       e = bkey_extent_init(op->insert_keys.top);
+       e->k.p          = op->pos;
+       e->k.size       = crc.uncompressed_size;
+       e->k.version    = version;
+
+       if (crc.csum_type ||
+           crc.compression_type ||
+           crc.nonce)
+               bch2_extent_crc_append(&e->k_i, crc);
+
+       bch2_alloc_sectors_append_ptrs_inlined(op->c, wp, &e->k_i, crc.compressed_size,
+                                      op->flags & BCH_WRITE_CACHED);
+
+       bch2_keylist_push(&op->insert_keys);
+}
+
+static struct bio *bch2_write_bio_alloc(struct bch_fs *c,
+                                       struct write_point *wp,
+                                       struct bio *src,
+                                       bool *page_alloc_failed,
+                                       void *buf)
+{
+       struct bch_write_bio *wbio;
+       struct bio *bio;
+       unsigned output_available =
+               min(wp->sectors_free << 9, src->bi_iter.bi_size);
+       unsigned pages = DIV_ROUND_UP(output_available +
+                                     (buf
+                                      ? ((unsigned long) buf & (PAGE_SIZE - 1))
+                                      : 0), PAGE_SIZE);
+
+       pages = min(pages, BIO_MAX_VECS);
+
+       bio = bio_alloc_bioset(NULL, pages, 0,
+                              GFP_NOFS, &c->bio_write);
+       wbio                    = wbio_init(bio);
+       wbio->put_bio           = true;
+       /* copy WRITE_SYNC flag */
+       wbio->bio.bi_opf        = src->bi_opf;
+
+       if (buf) {
+               bch2_bio_map(bio, buf, output_available);
+               return bio;
+       }
+
+       wbio->bounce            = true;
+
+       /*
+        * We can't use mempool for more than c->sb.encoded_extent_max
+        * worth of pages, but we'd like to allocate more if we can:
+        */
+       bch2_bio_alloc_pages_pool(c, bio,
+                                 min_t(unsigned, output_available,
+                                       c->opts.encoded_extent_max));
+
+       if (bio->bi_iter.bi_size < output_available)
+               *page_alloc_failed =
+                       bch2_bio_alloc_pages(bio,
+                                            output_available -
+                                            bio->bi_iter.bi_size,
+                                            GFP_NOFS) != 0;
+
+       return bio;
+}
+
+static int bch2_write_rechecksum(struct bch_fs *c,
+                                struct bch_write_op *op,
+                                unsigned new_csum_type)
+{
+       struct bio *bio = &op->wbio.bio;
+       struct bch_extent_crc_unpacked new_crc;
+       int ret;
+
+       /* bch2_rechecksum_bio() can't encrypt or decrypt data: */
+
+       if (bch2_csum_type_is_encryption(op->crc.csum_type) !=
+           bch2_csum_type_is_encryption(new_csum_type))
+               new_csum_type = op->crc.csum_type;
+
+       ret = bch2_rechecksum_bio(c, bio, op->version, op->crc,
+                                 NULL, &new_crc,
+                                 op->crc.offset, op->crc.live_size,
+                                 new_csum_type);
+       if (ret)
+               return ret;
+
+       bio_advance(bio, op->crc.offset << 9);
+       bio->bi_iter.bi_size = op->crc.live_size << 9;
+       op->crc = new_crc;
+       return 0;
+}
+
+static int bch2_write_decrypt(struct bch_write_op *op)
+{
+       struct bch_fs *c = op->c;
+       struct nonce nonce = extent_nonce(op->version, op->crc);
+       struct bch_csum csum;
+       int ret;
+
+       if (!bch2_csum_type_is_encryption(op->crc.csum_type))
+               return 0;
+
+       /*
+        * If we need to decrypt data in the write path, we'll no longer be able
+        * to verify the existing checksum (poly1305 mac, in this case) after
+        * it's decrypted - this is the last point we'll be able to reverify the
+        * checksum:
+        */
+       csum = bch2_checksum_bio(c, op->crc.csum_type, nonce, &op->wbio.bio);
+       if (bch2_crc_cmp(op->crc.csum, csum))
+               return -EIO;
+
+       ret = bch2_encrypt_bio(c, op->crc.csum_type, nonce, &op->wbio.bio);
+       op->crc.csum_type = 0;
+       op->crc.csum = (struct bch_csum) { 0, 0 };
+       return ret;
+}
+
+static enum prep_encoded_ret {
+       PREP_ENCODED_OK,
+       PREP_ENCODED_ERR,
+       PREP_ENCODED_CHECKSUM_ERR,
+       PREP_ENCODED_DO_WRITE,
+} bch2_write_prep_encoded_data(struct bch_write_op *op, struct write_point *wp)
+{
+       struct bch_fs *c = op->c;
+       struct bio *bio = &op->wbio.bio;
+
+       if (!(op->flags & BCH_WRITE_DATA_ENCODED))
+               return PREP_ENCODED_OK;
+
+       BUG_ON(bio_sectors(bio) != op->crc.compressed_size);
+
+       /* Can we just write the entire extent as is? */
+       if (op->crc.uncompressed_size == op->crc.live_size &&
+           op->crc.compressed_size <= wp->sectors_free &&
+           (op->crc.compression_type == bch2_compression_opt_to_type(op->compression_opt) ||
+            op->incompressible)) {
+               if (!crc_is_compressed(op->crc) &&
+                   op->csum_type != op->crc.csum_type &&
+                   bch2_write_rechecksum(c, op, op->csum_type) &&
+                   !c->opts.no_data_io)
+                       return PREP_ENCODED_CHECKSUM_ERR;
+
+               return PREP_ENCODED_DO_WRITE;
+       }
+
+       /*
+        * If the data is compressed and we couldn't write the entire extent as
+        * is, we have to decompress it:
+        */
+       if (crc_is_compressed(op->crc)) {
+               struct bch_csum csum;
+
+               if (bch2_write_decrypt(op))
+                       return PREP_ENCODED_CHECKSUM_ERR;
+
+               /* Last point we can still verify checksum: */
+               csum = bch2_checksum_bio(c, op->crc.csum_type,
+                                        extent_nonce(op->version, op->crc),
+                                        bio);
+               if (bch2_crc_cmp(op->crc.csum, csum) && !c->opts.no_data_io)
+                       return PREP_ENCODED_CHECKSUM_ERR;
+
+               if (bch2_bio_uncompress_inplace(c, bio, &op->crc))
+                       return PREP_ENCODED_ERR;
+       }
+
+       /*
+        * No longer have compressed data after this point - data might be
+        * encrypted:
+        */
+
+       /*
+        * If the data is checksummed and we're only writing a subset,
+        * rechecksum and adjust bio to point to currently live data:
+        */
+       if ((op->crc.live_size != op->crc.uncompressed_size ||
+            op->crc.csum_type != op->csum_type) &&
+           bch2_write_rechecksum(c, op, op->csum_type) &&
+           !c->opts.no_data_io)
+               return PREP_ENCODED_CHECKSUM_ERR;
+
+       /*
+        * If we want to compress the data, it has to be decrypted:
+        */
+       if ((op->compression_opt ||
+            bch2_csum_type_is_encryption(op->crc.csum_type) !=
+            bch2_csum_type_is_encryption(op->csum_type)) &&
+           bch2_write_decrypt(op))
+               return PREP_ENCODED_CHECKSUM_ERR;
+
+       return PREP_ENCODED_OK;
+}
+
+static int bch2_write_extent(struct bch_write_op *op, struct write_point *wp,
+                            struct bio **_dst)
+{
+       struct bch_fs *c = op->c;
+       struct bio *src = &op->wbio.bio, *dst = src;
+       struct bvec_iter saved_iter;
+       void *ec_buf;
+       unsigned total_output = 0, total_input = 0;
+       bool bounce = false;
+       bool page_alloc_failed = false;
+       int ret, more = 0;
+
+       BUG_ON(!bio_sectors(src));
+
+       ec_buf = bch2_writepoint_ec_buf(c, wp);
+
+       switch (bch2_write_prep_encoded_data(op, wp)) {
+       case PREP_ENCODED_OK:
+               break;
+       case PREP_ENCODED_ERR:
+               ret = -EIO;
+               goto err;
+       case PREP_ENCODED_CHECKSUM_ERR:
+               goto csum_err;
+       case PREP_ENCODED_DO_WRITE:
+               /* XXX look for bug here */
+               if (ec_buf) {
+                       dst = bch2_write_bio_alloc(c, wp, src,
+                                                  &page_alloc_failed,
+                                                  ec_buf);
+                       bio_copy_data(dst, src);
+                       bounce = true;
+               }
+               init_append_extent(op, wp, op->version, op->crc);
+               goto do_write;
+       }
+
+       if (ec_buf ||
+           op->compression_opt ||
+           (op->csum_type &&
+            !(op->flags & BCH_WRITE_PAGES_STABLE)) ||
+           (bch2_csum_type_is_encryption(op->csum_type) &&
+            !(op->flags & BCH_WRITE_PAGES_OWNED))) {
+               dst = bch2_write_bio_alloc(c, wp, src,
+                                          &page_alloc_failed,
+                                          ec_buf);
+               bounce = true;
+       }
+
+       saved_iter = dst->bi_iter;
+
+       do {
+               struct bch_extent_crc_unpacked crc = { 0 };
+               struct bversion version = op->version;
+               size_t dst_len, src_len;
+
+               if (page_alloc_failed &&
+                   dst->bi_iter.bi_size  < (wp->sectors_free << 9) &&
+                   dst->bi_iter.bi_size < c->opts.encoded_extent_max)
+                       break;
+
+               BUG_ON(op->compression_opt &&
+                      (op->flags & BCH_WRITE_DATA_ENCODED) &&
+                      bch2_csum_type_is_encryption(op->crc.csum_type));
+               BUG_ON(op->compression_opt && !bounce);
+
+               crc.compression_type = op->incompressible
+                       ? BCH_COMPRESSION_TYPE_incompressible
+                       : op->compression_opt
+                       ? bch2_bio_compress(c, dst, &dst_len, src, &src_len,
+                                           op->compression_opt)
+                       : 0;
+               if (!crc_is_compressed(crc)) {
+                       dst_len = min(dst->bi_iter.bi_size, src->bi_iter.bi_size);
+                       dst_len = min_t(unsigned, dst_len, wp->sectors_free << 9);
+
+                       if (op->csum_type)
+                               dst_len = min_t(unsigned, dst_len,
+                                               c->opts.encoded_extent_max);
+
+                       if (bounce) {
+                               swap(dst->bi_iter.bi_size, dst_len);
+                               bio_copy_data(dst, src);
+                               swap(dst->bi_iter.bi_size, dst_len);
+                       }
+
+                       src_len = dst_len;
+               }
+
+               BUG_ON(!src_len || !dst_len);
+
+               if (bch2_csum_type_is_encryption(op->csum_type)) {
+                       if (bversion_zero(version)) {
+                               version.lo = atomic64_inc_return(&c->key_version);
+                       } else {
+                               crc.nonce = op->nonce;
+                               op->nonce += src_len >> 9;
+                       }
+               }
+
+               if ((op->flags & BCH_WRITE_DATA_ENCODED) &&
+                   !crc_is_compressed(crc) &&
+                   bch2_csum_type_is_encryption(op->crc.csum_type) ==
+                   bch2_csum_type_is_encryption(op->csum_type)) {
+                       u8 compression_type = crc.compression_type;
+                       u16 nonce = crc.nonce;
+                       /*
+                        * Note: when we're using rechecksum(), we need to be
+                        * checksumming @src because it has all the data our
+                        * existing checksum covers - if we bounced (because we
+                        * were trying to compress), @dst will only have the
+                        * part of the data the new checksum will cover.
+                        *
+                        * But normally we want to be checksumming post bounce,
+                        * because part of the reason for bouncing is so the
+                        * data can't be modified (by userspace) while it's in
+                        * flight.
+                        */
+                       if (bch2_rechecksum_bio(c, src, version, op->crc,
+                                       &crc, &op->crc,
+                                       src_len >> 9,
+                                       bio_sectors(src) - (src_len >> 9),
+                                       op->csum_type))
+                               goto csum_err;
+                       /*
+                        * rchecksum_bio sets compression_type on crc from op->crc,
+                        * this isn't always correct as sometimes we're changing
+                        * an extent from uncompressed to incompressible.
+                        */
+                       crc.compression_type = compression_type;
+                       crc.nonce = nonce;
+               } else {
+                       if ((op->flags & BCH_WRITE_DATA_ENCODED) &&
+                           bch2_rechecksum_bio(c, src, version, op->crc,
+                                       NULL, &op->crc,
+                                       src_len >> 9,
+                                       bio_sectors(src) - (src_len >> 9),
+                                       op->crc.csum_type))
+                               goto csum_err;
+
+                       crc.compressed_size     = dst_len >> 9;
+                       crc.uncompressed_size   = src_len >> 9;
+                       crc.live_size           = src_len >> 9;
+
+                       swap(dst->bi_iter.bi_size, dst_len);
+                       ret = bch2_encrypt_bio(c, op->csum_type,
+                                              extent_nonce(version, crc), dst);
+                       if (ret)
+                               goto err;
+
+                       crc.csum = bch2_checksum_bio(c, op->csum_type,
+                                        extent_nonce(version, crc), dst);
+                       crc.csum_type = op->csum_type;
+                       swap(dst->bi_iter.bi_size, dst_len);
+               }
+
+               init_append_extent(op, wp, version, crc);
+
+               if (dst != src)
+                       bio_advance(dst, dst_len);
+               bio_advance(src, src_len);
+               total_output    += dst_len;
+               total_input     += src_len;
+       } while (dst->bi_iter.bi_size &&
+                src->bi_iter.bi_size &&
+                wp->sectors_free &&
+                !bch2_keylist_realloc(&op->insert_keys,
+                                     op->inline_keys,
+                                     ARRAY_SIZE(op->inline_keys),
+                                     BKEY_EXTENT_U64s_MAX));
+
+       more = src->bi_iter.bi_size != 0;
+
+       dst->bi_iter = saved_iter;
+
+       if (dst == src && more) {
+               BUG_ON(total_output != total_input);
+
+               dst = bio_split(src, total_input >> 9,
+                               GFP_NOFS, &c->bio_write);
+               wbio_init(dst)->put_bio = true;
+               /* copy WRITE_SYNC flag */
+               dst->bi_opf             = src->bi_opf;
+       }
+
+       dst->bi_iter.bi_size = total_output;
+do_write:
+       *_dst = dst;
+       return more;
+csum_err:
+       bch_err(c, "error verifying existing checksum while rewriting existing data (memory corruption?)");
+       ret = -EIO;
 err:
-       if (op->flags & BCH_WRITE_DISCARD_ON_ERROR) {
-               /*
-                * If we were writing cached data, not doing the write is fine
-                * so long as we discard whatever would have been overwritten -
-                * then it's equivalent to doing the write and immediately
-                * reclaiming it.
-                */
+       if (to_wbio(dst)->bounce)
+               bch2_bio_free_pages_pool(c, dst);
+       if (to_wbio(dst)->put_bio)
+               bio_put(dst);
 
-               bch2_write_discard(cl);
-       } else {
-               /*
-                * Right now we can only error here if we went RO - the
-                * allocation failed, but we already checked for -ENOSPC when we
-                * got our reservation.
-                *
-                * XXX capacity might have changed, but we don't check for that
-                * yet:
-                */
-               op->error = ret;
+       return ret;
+}
+
+static bool bch2_extent_is_writeable(struct bch_write_op *op,
+                                    struct bkey_s_c k)
+{
+       struct bch_fs *c = op->c;
+       struct bkey_s_c_extent e;
+       struct extent_ptr_decoded p;
+       const union bch_extent_entry *entry;
+       unsigned replicas = 0;
+
+       if (k.k->type != KEY_TYPE_extent)
+               return false;
+
+       e = bkey_s_c_to_extent(k);
+       extent_for_each_ptr_decode(e, p, entry) {
+               if (p.crc.csum_type ||
+                   crc_is_compressed(p.crc) ||
+                   p.has_ec)
+                       return false;
+
+               replicas += bch2_extent_ptr_durability(c, &p);
        }
 
-       op->flags |= BCH_WRITE_DONE;
+       return replicas >= op->opts.data_replicas;
+}
+
+static inline void bch2_nocow_write_unlock(struct bch_write_op *op)
+{
+       struct bch_fs *c = op->c;
+       const struct bch_extent_ptr *ptr;
+       struct bkey_i *k;
+
+       for_each_keylist_key(&op->insert_keys, k) {
+               struct bkey_ptrs_c ptrs = bch2_bkey_ptrs_c(bkey_i_to_s_c(k));
+
+               bkey_for_each_ptr(ptrs, ptr)
+                       bch2_bucket_nocow_unlock(&c->nocow_locks,
+                                              PTR_BUCKET_POS(c, ptr),
+                                              BUCKET_NOCOW_LOCK_UPDATE);
+       }
+}
+
+static int bch2_nocow_write_convert_one_unwritten(struct btree_trans *trans,
+                                                 struct btree_iter *iter,
+                                                 struct bkey_i *orig,
+                                                 struct bkey_s_c k,
+                                                 u64 new_i_size)
+{
+       struct bkey_i *new;
+       struct bkey_ptrs ptrs;
+       struct bch_extent_ptr *ptr;
+       int ret;
+
+       if (!bch2_extents_match(bkey_i_to_s_c(orig), k)) {
+               /* trace this */
+               return 0;
+       }
+
+       new = bch2_bkey_make_mut_noupdate(trans, k);
+       ret = PTR_ERR_OR_ZERO(new);
+       if (ret)
+               return ret;
+
+       bch2_cut_front(bkey_start_pos(&orig->k), new);
+       bch2_cut_back(orig->k.p, new);
+
+       ptrs = bch2_bkey_ptrs(bkey_i_to_s(new));
+       bkey_for_each_ptr(ptrs, ptr)
+               ptr->unwritten = 0;
 
        /*
-        * No reason not to insert keys for whatever data was successfully
-        * written (especially for a cmpxchg operation that's moving data
-        * around)
+        * Note that we're not calling bch2_subvol_get_snapshot() in this path -
+        * that was done when we kicked off the write, and here it's important
+        * that we update the extent that we wrote to - even if a snapshot has
+        * since been created. The write is still outstanding, so we're ok
+        * w.r.t. snapshot atomicity:
         */
-       continue_at(cl, !bch2_keylist_empty(&op->insert_keys)
-                   ? bch2_write_index
-                   : bch2_write_done, index_update_wq(op));
+       return  bch2_extent_update_i_size_sectors(trans, iter,
+                                       min(new->k.p.offset << 9, new_i_size), 0) ?:
+               bch2_trans_update(trans, iter, new,
+                                 BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE);
 }
 
-void bch2_wake_delayed_writes(unsigned long data)
+static void bch2_nocow_write_convert_unwritten(struct bch_write_op *op)
 {
-       struct bch_fs *c = (void *) data;
-       struct bch_write_op *op;
-       unsigned long flags;
+       struct bch_fs *c = op->c;
+       struct btree_trans trans;
+       struct btree_iter iter;
+       struct bkey_i *orig;
+       struct bkey_s_c k;
+       int ret;
+
+       bch2_trans_init(&trans, c, 0, 0);
+
+       for_each_keylist_key(&op->insert_keys, orig) {
+               ret = for_each_btree_key_upto_commit(&trans, iter, BTREE_ID_extents,
+                                    bkey_start_pos(&orig->k), orig->k.p,
+                                    BTREE_ITER_INTENT, k,
+                                    NULL, NULL, BTREE_INSERT_NOFAIL, ({
+                       bch2_nocow_write_convert_one_unwritten(&trans, &iter, orig, k, op->new_i_size);
+               }));
+
+               if (ret && !bch2_err_matches(ret, EROFS)) {
+                       struct bkey_i *k = bch2_keylist_front(&op->insert_keys);
+
+                       bch_err_inum_offset_ratelimited(c,
+                               k->k.p.inode, k->k.p.offset << 9,
+                               "write error while doing btree update: %s",
+                               bch2_err_str(ret));
+               }
+
+               if (ret) {
+                       op->error = ret;
+                       break;
+               }
+       }
+
+       bch2_trans_exit(&trans);
+}
+
+static void __bch2_nocow_write_done(struct bch_write_op *op)
+{
+       bch2_nocow_write_unlock(op);
+
+       if (unlikely(op->flags & BCH_WRITE_IO_ERROR)) {
+               op->error = -EIO;
+       } else if (unlikely(op->flags & BCH_WRITE_CONVERT_UNWRITTEN))
+               bch2_nocow_write_convert_unwritten(op);
+}
+
+static void bch2_nocow_write_done(struct closure *cl)
+{
+       struct bch_write_op *op = container_of(cl, struct bch_write_op, cl);
+
+       __bch2_nocow_write_done(op);
+       bch2_write_done(cl);
+}
+
+static void bch2_nocow_write(struct bch_write_op *op)
+{
+       struct bch_fs *c = op->c;
+       struct btree_trans trans;
+       struct btree_iter iter;
+       struct bkey_s_c k;
+       struct bkey_ptrs_c ptrs;
+       const struct bch_extent_ptr *ptr;
+       struct {
+               struct bpos     b;
+               unsigned        gen;
+               struct nocow_lock_bucket *l;
+       } buckets[BCH_REPLICAS_MAX];
+       unsigned nr_buckets = 0;
+       u32 snapshot;
+       int ret, i;
+
+       if (op->flags & BCH_WRITE_MOVE)
+               return;
 
-       spin_lock_irqsave(&c->foreground_write_pd_lock, flags);
+       bch2_trans_init(&trans, c, 0, 0);
+retry:
+       bch2_trans_begin(&trans);
 
-       while ((op = c->write_wait_head)) {
-               if (time_after(op->expires, jiffies)) {
-                       mod_timer(&c->foreground_write_wakeup, op->expires);
+       ret = bch2_subvolume_get_snapshot(&trans, op->subvol, &snapshot);
+       if (unlikely(ret))
+               goto err;
+
+       bch2_trans_iter_init(&trans, &iter, BTREE_ID_extents,
+                            SPOS(op->pos.inode, op->pos.offset, snapshot),
+                            BTREE_ITER_SLOTS);
+       while (1) {
+               struct bio *bio = &op->wbio.bio;
+
+               nr_buckets = 0;
+
+               k = bch2_btree_iter_peek_slot(&iter);
+               ret = bkey_err(k);
+               if (ret)
+                       break;
+
+               /* fall back to normal cow write path? */
+               if (unlikely(k.k->p.snapshot != snapshot ||
+                            !bch2_extent_is_writeable(op, k)))
                        break;
+
+               if (bch2_keylist_realloc(&op->insert_keys,
+                                       op->inline_keys,
+                                       ARRAY_SIZE(op->inline_keys),
+                                       k.k->u64s))
+                       break;
+
+               /* Get iorefs before dropping btree locks: */
+               ptrs = bch2_bkey_ptrs_c(k);
+               bkey_for_each_ptr(ptrs, ptr) {
+                       buckets[nr_buckets].b = PTR_BUCKET_POS(c, ptr);
+                       buckets[nr_buckets].gen = ptr->gen;
+                       buckets[nr_buckets].l =
+                               bucket_nocow_lock(&c->nocow_locks,
+                                                 bucket_to_u64(buckets[nr_buckets].b));
+
+                       prefetch(buckets[nr_buckets].l);
+
+                       if (unlikely(!bch2_dev_get_ioref(bch_dev_bkey_exists(c, ptr->dev), WRITE)))
+                               goto err_get_ioref;
+
+                       nr_buckets++;
+
+                       if (ptr->unwritten)
+                               op->flags |= BCH_WRITE_CONVERT_UNWRITTEN;
+               }
+
+               /* Unlock before taking nocow locks, doing IO: */
+               bkey_reassemble(op->insert_keys.top, k);
+               bch2_trans_unlock(&trans);
+
+               bch2_cut_front(op->pos, op->insert_keys.top);
+               if (op->flags & BCH_WRITE_CONVERT_UNWRITTEN)
+                       bch2_cut_back(POS(op->pos.inode, op->pos.offset + bio_sectors(bio)), op->insert_keys.top);
+
+               for (i = 0; i < nr_buckets; i++) {
+                       struct bch_dev *ca = bch_dev_bkey_exists(c, buckets[i].b.inode);
+                       struct nocow_lock_bucket *l = buckets[i].l;
+                       bool stale;
+
+                       __bch2_bucket_nocow_lock(&c->nocow_locks, l,
+                                                bucket_to_u64(buckets[i].b),
+                                                BUCKET_NOCOW_LOCK_UPDATE);
+
+                       rcu_read_lock();
+                       stale = gen_after(*bucket_gen(ca, buckets[i].b.offset), buckets[i].gen);
+                       rcu_read_unlock();
+
+                       if (unlikely(stale))
+                               goto err_bucket_stale;
                }
 
-               c->write_wait_head = op->next;
-               if (!c->write_wait_head)
-                       c->write_wait_tail = NULL;
+               bio = &op->wbio.bio;
+               if (k.k->p.offset < op->pos.offset + bio_sectors(bio)) {
+                       bio = bio_split(bio, k.k->p.offset - op->pos.offset,
+                                       GFP_KERNEL, &c->bio_write);
+                       wbio_init(bio)->put_bio = true;
+                       bio->bi_opf = op->wbio.bio.bi_opf;
+               } else {
+                       op->flags |= BCH_WRITE_DONE;
+               }
+
+               op->pos.offset += bio_sectors(bio);
+               op->written += bio_sectors(bio);
+
+               bio->bi_end_io  = bch2_write_endio;
+               bio->bi_private = &op->cl;
+               bio->bi_opf |= REQ_OP_WRITE;
+               closure_get(&op->cl);
+               bch2_submit_wbio_replicas(to_wbio(bio), c, BCH_DATA_user,
+                                         op->insert_keys.top, true);
 
-               closure_put(&op->cl);
+               bch2_keylist_push(&op->insert_keys);
+               if (op->flags & BCH_WRITE_DONE)
+                       break;
+               bch2_btree_iter_advance(&iter);
+       }
+out:
+       bch2_trans_iter_exit(&trans, &iter);
+err:
+       if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
+               goto retry;
+
+       if (ret) {
+               bch_err_inum_offset_ratelimited(c,
+                               op->pos.inode,
+                               op->pos.offset << 9,
+                               "%s: btree lookup error %s",
+                               __func__, bch2_err_str(ret));
+               op->error = ret;
+               op->flags |= BCH_WRITE_DONE;
        }
 
-       spin_unlock_irqrestore(&c->foreground_write_pd_lock, flags);
+       bch2_trans_exit(&trans);
+
+       /* fallback to cow write path? */
+       if (!(op->flags & BCH_WRITE_DONE)) {
+               closure_sync(&op->cl);
+               __bch2_nocow_write_done(op);
+               op->insert_keys.top = op->insert_keys.keys;
+       } else if (op->flags & BCH_WRITE_SYNC) {
+               closure_sync(&op->cl);
+               bch2_nocow_write_done(&op->cl);
+       } else {
+               /*
+                * XXX
+                * needs to run out of process context because ei_quota_lock is
+                * a mutex
+                */
+               continue_at(&op->cl, bch2_nocow_write_done, index_update_wq(op));
+       }
+       return;
+err_get_ioref:
+       for (i = 0; i < nr_buckets; i++)
+               percpu_ref_put(&bch_dev_bkey_exists(c, buckets[i].b.inode)->io_ref);
+
+       /* Fall back to COW path: */
+       goto out;
+err_bucket_stale:
+       while (--i >= 0)
+               bch2_bucket_nocow_unlock(&c->nocow_locks,
+                                        buckets[i].b,
+                                        BUCKET_NOCOW_LOCK_UPDATE);
+       for (i = 0; i < nr_buckets; i++)
+               percpu_ref_put(&bch_dev_bkey_exists(c, buckets[i].b.inode)->io_ref);
+
+       /* We can retry this: */
+       ret = -BCH_ERR_transaction_restart;
+       goto out;
+}
+
+static void __bch2_write(struct bch_write_op *op)
+{
+       struct bch_fs *c = op->c;
+       struct write_point *wp = NULL;
+       struct bio *bio = NULL;
+       unsigned nofs_flags;
+       int ret;
+
+       nofs_flags = memalloc_nofs_save();
+
+       if (unlikely(op->opts.nocow && c->opts.nocow_enabled)) {
+               bch2_nocow_write(op);
+               if (op->flags & BCH_WRITE_DONE)
+                       goto out_nofs_restore;
+       }
+again:
+       memset(&op->failed, 0, sizeof(op->failed));
+
+       do {
+               struct bkey_i *key_to_write;
+               unsigned key_to_write_offset = op->insert_keys.top_p -
+                       op->insert_keys.keys_p;
+
+               /* +1 for possible cache device: */
+               if (op->open_buckets.nr + op->nr_replicas + 1 >
+                   ARRAY_SIZE(op->open_buckets.v))
+                       break;
+
+               if (bch2_keylist_realloc(&op->insert_keys,
+                                       op->inline_keys,
+                                       ARRAY_SIZE(op->inline_keys),
+                                       BKEY_EXTENT_U64s_MAX))
+                       break;
+
+               /*
+                * The copygc thread is now global, which means it's no longer
+                * freeing up space on specific disks, which means that
+                * allocations for specific disks may hang arbitrarily long:
+                */
+               ret = bch2_trans_do(c, NULL, NULL, 0,
+                       bch2_alloc_sectors_start_trans(&trans,
+                               op->target,
+                               op->opts.erasure_code && !(op->flags & BCH_WRITE_CACHED),
+                               op->write_point,
+                               &op->devs_have,
+                               op->nr_replicas,
+                               op->nr_replicas_required,
+                               op->watermark,
+                               op->flags,
+                               (op->flags & (BCH_WRITE_ALLOC_NOWAIT|
+                                             BCH_WRITE_ONLY_SPECIFIED_DEVS))
+                               ? NULL : &op->cl, &wp));
+               if (unlikely(ret)) {
+                       if (bch2_err_matches(ret, BCH_ERR_operation_blocked))
+                               break;
+
+                       goto err;
+               }
+
+               EBUG_ON(!wp);
+
+               bch2_open_bucket_get(c, wp, &op->open_buckets);
+               ret = bch2_write_extent(op, wp, &bio);
+
+               bch2_alloc_sectors_done_inlined(c, wp);
+err:
+               if (ret <= 0) {
+                       op->flags |= BCH_WRITE_DONE;
+
+                       if (ret < 0) {
+                               op->error = ret;
+                               break;
+                       }
+               }
+
+               bio->bi_end_io  = bch2_write_endio;
+               bio->bi_private = &op->cl;
+               bio->bi_opf |= REQ_OP_WRITE;
+
+               closure_get(bio->bi_private);
+
+               key_to_write = (void *) (op->insert_keys.keys_p +
+                                        key_to_write_offset);
+
+               bch2_submit_wbio_replicas(to_wbio(bio), c, BCH_DATA_user,
+                                         key_to_write, false);
+       } while (ret);
+
+       /*
+        * Sync or no?
+        *
+        * If we're running asynchronously, wne may still want to block
+        * synchronously here if we weren't able to submit all of the IO at
+        * once, as that signals backpressure to the caller.
+        */
+       if ((op->flags & BCH_WRITE_SYNC) ||
+           (!(op->flags & BCH_WRITE_DONE) &&
+            !(op->flags & BCH_WRITE_IN_WORKER))) {
+               closure_sync(&op->cl);
+               __bch2_write_index(op);
+
+               if (!(op->flags & BCH_WRITE_DONE))
+                       goto again;
+               bch2_write_done(&op->cl);
+       } else {
+               bch2_write_queue(op, wp);
+               continue_at(&op->cl, bch2_write_index, NULL);
+       }
+out_nofs_restore:
+       memalloc_nofs_restore(nofs_flags);
+}
+
+static void bch2_write_data_inline(struct bch_write_op *op, unsigned data_len)
+{
+       struct bio *bio = &op->wbio.bio;
+       struct bvec_iter iter;
+       struct bkey_i_inline_data *id;
+       unsigned sectors;
+       int ret;
+
+       op->flags |= BCH_WRITE_WROTE_DATA_INLINE;
+       op->flags |= BCH_WRITE_DONE;
+
+       bch2_check_set_feature(op->c, BCH_FEATURE_inline_data);
+
+       ret = bch2_keylist_realloc(&op->insert_keys, op->inline_keys,
+                                  ARRAY_SIZE(op->inline_keys),
+                                  BKEY_U64s + DIV_ROUND_UP(data_len, 8));
+       if (ret) {
+               op->error = ret;
+               goto err;
+       }
+
+       sectors = bio_sectors(bio);
+       op->pos.offset += sectors;
+
+       id = bkey_inline_data_init(op->insert_keys.top);
+       id->k.p         = op->pos;
+       id->k.version   = op->version;
+       id->k.size      = sectors;
+
+       iter = bio->bi_iter;
+       iter.bi_size = data_len;
+       memcpy_from_bio(id->v.data, bio, iter);
+
+       while (data_len & 7)
+               id->v.data[data_len++] = '\0';
+       set_bkey_val_bytes(&id->k, data_len);
+       bch2_keylist_push(&op->insert_keys);
+
+       __bch2_write_index(op);
+err:
+       bch2_write_done(&op->cl);
 }
 
 /**
@@ -701,288 +1810,550 @@ void bch2_wake_delayed_writes(unsigned long data)
  * after the data is written it calls bch_journal, and after the keys have been
  * added to the next journal write they're inserted into the btree.
  *
- * It inserts the data in op->bio; bi_sector is used for the key offset, and
- * op->inode is used for the key inode.
- *
  * If op->discard is true, instead of inserting the data it invalidates the
  * region of the cache represented by op->bio and op->inode.
  */
 void bch2_write(struct closure *cl)
 {
        struct bch_write_op *op = container_of(cl, struct bch_write_op, cl);
-       struct bio *bio = &op->bio->bio;
+       struct bio *bio = &op->wbio.bio;
        struct bch_fs *c = op->c;
-       u64 inode = op->pos.inode;
+       unsigned data_len;
+
+       EBUG_ON(op->cl.parent);
+       BUG_ON(!op->nr_replicas);
+       BUG_ON(!op->write_point.v);
+       BUG_ON(bkey_eq(op->pos, POS_MAX));
+
+       op->start_time = local_clock();
+       bch2_keylist_init(&op->insert_keys, op->inline_keys);
+       wbio_init(bio)->put_bio = false;
+
+       if (bio->bi_iter.bi_size & (c->opts.block_size - 1)) {
+               bch_err_inum_offset_ratelimited(c,
+                       op->pos.inode,
+                       op->pos.offset << 9,
+                       "misaligned write");
+               op->error = -EIO;
+               goto err;
+       }
 
-       if (c->opts.nochanges ||
-           !percpu_ref_tryget(&c->writes)) {
-               __bcache_io_error(c, "read only");
-               op->error = -EROFS;
-               bch2_disk_reservation_put(c, &op->res);
-               closure_return(cl);
+       if (c->opts.nochanges) {
+               op->error = -BCH_ERR_erofs_no_writes;
+               goto err;
        }
 
-       if (bversion_zero(op->version) &&
-           bch2_csum_type_is_encryption(op->csum_type))
-               op->version.lo =
-                       atomic64_inc_return(&c->key_version) + 1;
+       if (!(op->flags & BCH_WRITE_MOVE) &&
+           !bch2_write_ref_tryget(c, BCH_WRITE_REF_write)) {
+               op->error = -BCH_ERR_erofs_no_writes;
+               goto err;
+       }
+
+       this_cpu_add(c->counters[BCH_COUNTER_io_write], bio_sectors(bio));
+       bch2_increment_clock(c, bio_sectors(bio), WRITE);
+
+       data_len = min_t(u64, bio->bi_iter.bi_size,
+                        op->new_i_size - (op->pos.offset << 9));
 
-       if (!(op->flags & BCH_WRITE_DISCARD))
-               bch2_increment_clock(c, bio_sectors(bio), WRITE);
+       if (c->opts.inline_data &&
+           data_len <= min(block_bytes(c) / 2, 1024U)) {
+               bch2_write_data_inline(op, data_len);
+               return;
+       }
 
-       /* Don't call bch2_next_delay() if rate is >= 1 GB/sec */
+       __bch2_write(op);
+       return;
+err:
+       bch2_disk_reservation_put(c, &op->res);
 
-       if (c->foreground_write_ratelimit_enabled &&
-           c->foreground_write_pd.rate.rate < (1 << 30) &&
-           !(op->flags & BCH_WRITE_DISCARD) && op->wp->throttle) {
-               unsigned long flags;
-               u64 delay;
+       closure_debug_destroy(&op->cl);
+       if (op->end_io)
+               op->end_io(op);
+}
 
-               spin_lock_irqsave(&c->foreground_write_pd_lock, flags);
-               bch2_ratelimit_increment(&c->foreground_write_pd.rate,
-                                       bio->bi_iter.bi_size);
+static const char * const bch2_write_flags[] = {
+#define x(f)   #f,
+       BCH_WRITE_FLAGS()
+#undef x
+       NULL
+};
 
-               delay = bch2_ratelimit_delay(&c->foreground_write_pd.rate);
+void bch2_write_op_to_text(struct printbuf *out, struct bch_write_op *op)
+{
+       prt_str(out, "pos: ");
+       bch2_bpos_to_text(out, op->pos);
+       prt_newline(out);
+       printbuf_indent_add(out, 2);
 
-               if (delay >= HZ / 100) {
-                       trace_write_throttle(c, inode, bio, delay);
+       prt_str(out, "started: ");
+       bch2_pr_time_units(out, local_clock() - op->start_time);
+       prt_newline(out);
 
-                       closure_get(&op->cl); /* list takes a ref */
+       prt_str(out, "flags: ");
+       prt_bitflags(out, bch2_write_flags, op->flags);
+       prt_newline(out);
 
-                       op->expires = jiffies + delay;
-                       op->next = NULL;
+       prt_printf(out, "ref: %u", closure_nr_remaining(&op->cl));
+       prt_newline(out);
 
-                       if (c->write_wait_tail)
-                               c->write_wait_tail->next = op;
-                       else
-                               c->write_wait_head = op;
-                       c->write_wait_tail = op;
+       printbuf_indent_sub(out, 2);
+}
+
+/* Cache promotion on read */
+
+struct promote_op {
+       struct rcu_head         rcu;
+       u64                     start_time;
+
+       struct rhash_head       hash;
+       struct bpos             pos;
+
+       struct data_update      write;
+       struct bio_vec          bi_inline_vecs[0]; /* must be last */
+};
+
+static const struct rhashtable_params bch_promote_params = {
+       .head_offset    = offsetof(struct promote_op, hash),
+       .key_offset     = offsetof(struct promote_op, pos),
+       .key_len        = sizeof(struct bpos),
+};
 
-                       if (!timer_pending(&c->foreground_write_wakeup))
-                               mod_timer(&c->foreground_write_wakeup,
-                                         op->expires);
+static inline bool should_promote(struct bch_fs *c, struct bkey_s_c k,
+                                 struct bpos pos,
+                                 struct bch_io_opts opts,
+                                 unsigned flags)
+{
+       if (!(flags & BCH_READ_MAY_PROMOTE))
+               return false;
+
+       if (!opts.promote_target)
+               return false;
+
+       if (bch2_bkey_has_target(c, k, opts.promote_target))
+               return false;
+
+       if (bkey_extent_is_unwritten(k))
+               return false;
+
+       if (bch2_target_congested(c, opts.promote_target)) {
+               /* XXX trace this */
+               return false;
+       }
+
+       if (rhashtable_lookup_fast(&c->promote_table, &pos,
+                                  bch_promote_params))
+               return false;
+
+       return true;
+}
+
+static void promote_free(struct bch_fs *c, struct promote_op *op)
+{
+       int ret;
+
+       bch2_data_update_exit(&op->write);
+
+       ret = rhashtable_remove_fast(&c->promote_table, &op->hash,
+                                    bch_promote_params);
+       BUG_ON(ret);
+       bch2_write_ref_put(c, BCH_WRITE_REF_promote);
+       kfree_rcu(op, rcu);
+}
+
+static void promote_done(struct bch_write_op *wop)
+{
+       struct promote_op *op =
+               container_of(wop, struct promote_op, write.op);
+       struct bch_fs *c = op->write.op.c;
+
+       bch2_time_stats_update(&c->times[BCH_TIME_data_promote],
+                              op->start_time);
+       promote_free(c, op);
+}
+
+static void promote_start(struct promote_op *op, struct bch_read_bio *rbio)
+{
+       struct bio *bio = &op->write.op.wbio.bio;
+
+       trace_and_count(op->write.op.c, read_promote, &rbio->bio);
+
+       /* we now own pages: */
+       BUG_ON(!rbio->bounce);
+       BUG_ON(rbio->bio.bi_vcnt > bio->bi_max_vecs);
+
+       memcpy(bio->bi_io_vec, rbio->bio.bi_io_vec,
+              sizeof(struct bio_vec) * rbio->bio.bi_vcnt);
+       swap(bio->bi_vcnt, rbio->bio.bi_vcnt);
+
+       bch2_data_update_read_done(&op->write, rbio->pick.crc);
+}
+
+static struct promote_op *__promote_alloc(struct btree_trans *trans,
+                                         enum btree_id btree_id,
+                                         struct bkey_s_c k,
+                                         struct bpos pos,
+                                         struct extent_ptr_decoded *pick,
+                                         struct bch_io_opts opts,
+                                         unsigned sectors,
+                                         struct bch_read_bio **rbio)
+{
+       struct bch_fs *c = trans->c;
+       struct promote_op *op = NULL;
+       struct bio *bio;
+       unsigned pages = DIV_ROUND_UP(sectors, PAGE_SECTORS);
+       int ret;
+
+       if (!bch2_write_ref_tryget(c, BCH_WRITE_REF_promote))
+               return NULL;
+
+       op = kzalloc(sizeof(*op) + sizeof(struct bio_vec) * pages, GFP_NOFS);
+       if (!op)
+               goto err;
+
+       op->start_time = local_clock();
+       op->pos = pos;
+
+       /*
+        * We don't use the mempool here because extents that aren't
+        * checksummed or compressed can be too big for the mempool:
+        */
+       *rbio = kzalloc(sizeof(struct bch_read_bio) +
+                       sizeof(struct bio_vec) * pages,
+                       GFP_NOFS);
+       if (!*rbio)
+               goto err;
+
+       rbio_init(&(*rbio)->bio, opts);
+       bio_init(&(*rbio)->bio, NULL, (*rbio)->bio.bi_inline_vecs, pages, 0);
+
+       if (bch2_bio_alloc_pages(&(*rbio)->bio, sectors << 9,
+                                GFP_NOFS))
+               goto err;
+
+       (*rbio)->bounce         = true;
+       (*rbio)->split          = true;
+       (*rbio)->kmalloc        = true;
+
+       if (rhashtable_lookup_insert_fast(&c->promote_table, &op->hash,
+                                         bch_promote_params))
+               goto err;
+
+       bio = &op->write.op.wbio.bio;
+       bio_init(bio, NULL, bio->bi_inline_vecs, pages, 0);
+
+       ret = bch2_data_update_init(trans, NULL, &op->write,
+                       writepoint_hashed((unsigned long) current),
+                       opts,
+                       (struct data_update_opts) {
+                               .target         = opts.promote_target,
+                               .extra_replicas = 1,
+                               .write_flags    = BCH_WRITE_ALLOC_NOWAIT|BCH_WRITE_CACHED,
+                       },
+                       btree_id, k);
+       /*
+        * possible errors: -BCH_ERR_nocow_lock_blocked,
+        * -BCH_ERR_ENOSPC_disk_reservation:
+        */
+       if (ret) {
+               ret = rhashtable_remove_fast(&c->promote_table, &op->hash,
+                                       bch_promote_params);
+               BUG_ON(ret);
+               goto err;
+       }
+
+       op->write.op.end_io = promote_done;
+
+       return op;
+err:
+       if (*rbio)
+               bio_free_pages(&(*rbio)->bio);
+       kfree(*rbio);
+       *rbio = NULL;
+       kfree(op);
+       bch2_write_ref_put(c, BCH_WRITE_REF_promote);
+       return NULL;
+}
+
+noinline
+static struct promote_op *promote_alloc(struct btree_trans *trans,
+                                       struct bvec_iter iter,
+                                       struct bkey_s_c k,
+                                       struct extent_ptr_decoded *pick,
+                                       struct bch_io_opts opts,
+                                       unsigned flags,
+                                       struct bch_read_bio **rbio,
+                                       bool *bounce,
+                                       bool *read_full)
+{
+       struct bch_fs *c = trans->c;
+       bool promote_full = *read_full || READ_ONCE(c->promote_whole_extents);
+       /* data might have to be decompressed in the write path: */
+       unsigned sectors = promote_full
+               ? max(pick->crc.compressed_size, pick->crc.live_size)
+               : bvec_iter_sectors(iter);
+       struct bpos pos = promote_full
+               ? bkey_start_pos(k.k)
+               : POS(k.k->p.inode, iter.bi_sector);
+       struct promote_op *promote;
+
+       if (!should_promote(c, k, pos, opts, flags))
+               return NULL;
+
+       promote = __promote_alloc(trans,
+                                 k.k->type == KEY_TYPE_reflink_v
+                                 ? BTREE_ID_reflink
+                                 : BTREE_ID_extents,
+                                 k, pos, pick, opts, sectors, rbio);
+       if (!promote)
+               return NULL;
+
+       *bounce         = true;
+       *read_full      = promote_full;
+       return promote;
+}
+
+/* Read */
+
+#define READ_RETRY_AVOID       1
+#define READ_RETRY             2
+#define READ_ERR               3
+
+enum rbio_context {
+       RBIO_CONTEXT_NULL,
+       RBIO_CONTEXT_HIGHPRI,
+       RBIO_CONTEXT_UNBOUND,
+};
 
-                       spin_unlock_irqrestore(&c->foreground_write_pd_lock,
-                                              flags);
-                       continue_at(cl, __bch2_write, index_update_wq(op));
-               }
+static inline struct bch_read_bio *
+bch2_rbio_parent(struct bch_read_bio *rbio)
+{
+       return rbio->split ? rbio->parent : rbio;
+}
 
-               spin_unlock_irqrestore(&c->foreground_write_pd_lock, flags);
+__always_inline
+static void bch2_rbio_punt(struct bch_read_bio *rbio, work_func_t fn,
+                          enum rbio_context context,
+                          struct workqueue_struct *wq)
+{
+       if (context <= rbio->context) {
+               fn(&rbio->work);
+       } else {
+               rbio->work.func         = fn;
+               rbio->context           = context;
+               queue_work(wq, &rbio->work);
        }
-
-       continue_at_nobarrier(cl, __bch2_write, NULL);
 }
 
-void bch2_write_op_init(struct bch_write_op *op, struct bch_fs *c,
-                      struct bch_write_bio *bio, struct disk_reservation res,
-                      struct write_point *wp, struct bpos pos,
-                      u64 *journal_seq, unsigned flags)
+static inline struct bch_read_bio *bch2_rbio_free(struct bch_read_bio *rbio)
 {
-       EBUG_ON(res.sectors && !res.nr_replicas);
+       BUG_ON(rbio->bounce && !rbio->split);
 
-       op->c           = c;
-       op->io_wq       = index_update_wq(op);
-       op->bio         = bio;
-       op->written     = 0;
-       op->error       = 0;
-       op->flags       = flags;
-       op->csum_type   = bch2_data_checksum_type(c);
-       op->compression_type = c->opts.compression;
-       op->nr_replicas = res.nr_replicas;
-       op->alloc_reserve = RESERVE_NONE;
-       op->nonce       = 0;
-       op->pos         = pos;
-       op->version     = ZERO_VERSION;
-       op->res         = res;
-       op->wp          = wp;
+       if (rbio->promote)
+               promote_free(rbio->c, rbio->promote);
+       rbio->promote = NULL;
 
-       if (journal_seq) {
-               op->journal_seq_p = journal_seq;
-               op->flags |= BCH_WRITE_JOURNAL_SEQ_PTR;
-       } else {
-               op->journal_seq = 0;
-       }
+       if (rbio->bounce)
+               bch2_bio_free_pages_pool(rbio->c, &rbio->bio);
+
+       if (rbio->split) {
+               struct bch_read_bio *parent = rbio->parent;
 
-       op->index_update_fn = bch2_write_index_default;
+               if (rbio->kmalloc)
+                       kfree(rbio);
+               else
+                       bio_put(&rbio->bio);
 
-       bch2_keylist_init(&op->insert_keys,
-                         op->inline_keys,
-                         ARRAY_SIZE(op->inline_keys));
+               rbio = parent;
+       }
 
-       if (version_stress_test(c))
-               get_random_bytes(&op->version, sizeof(op->version));
+       return rbio;
 }
 
-/* Discard */
-
-/* bch_discard - discard a range of keys from start_key to end_key.
- * @c          filesystem
- * @start_key  pointer to start location
- *             NOTE: discard starts at bkey_start_offset(start_key)
- * @end_key    pointer to end location
- *             NOTE: discard ends at KEY_OFFSET(end_key)
- * @version    version of discard (0ULL if none)
- *
- * Returns:
- *      0 on success
- *     <0 on error
- *
- * XXX: this needs to be refactored with inode_truncate, or more
- *     appropriately inode_truncate should call this
+/*
+ * Only called on a top level bch_read_bio to complete an entire read request,
+ * not a split:
  */
-int bch2_discard(struct bch_fs *c, struct bpos start,
-                struct bpos end, struct bversion version,
-                struct disk_reservation *disk_res,
-                struct extent_insert_hook *hook,
-                u64 *journal_seq)
+static void bch2_rbio_done(struct bch_read_bio *rbio)
 {
-       return bch2_btree_delete_range(c, BTREE_ID_EXTENTS, start, end, version,
-                                     disk_res, hook, journal_seq);
+       if (rbio->start_time)
+               bch2_time_stats_update(&rbio->c->times[BCH_TIME_data_read],
+                                      rbio->start_time);
+       bio_endio(&rbio->bio);
 }
 
-/* Cache promotion on read */
-
-struct cache_promote_op {
-       struct closure          cl;
-       struct migrate_write    write;
-       struct bio_vec          bi_inline_vecs[0]; /* must be last */
-};
-
-/* Read */
-
-static int bio_checksum_uncompress(struct bch_fs *c,
-                                  struct bch_read_bio *rbio)
+static void bch2_read_retry_nodecode(struct bch_fs *c, struct bch_read_bio *rbio,
+                                    struct bvec_iter bvec_iter,
+                                    struct bch_io_failures *failed,
+                                    unsigned flags)
 {
-       struct bio *src = &rbio->bio;
-       struct bio *dst = &bch2_rbio_parent(rbio)->bio;
-       struct bvec_iter dst_iter = rbio->parent_iter;
-       struct nonce nonce = extent_nonce(rbio->version,
-                               rbio->crc.nonce,
-                               crc_uncompressed_size(NULL, &rbio->crc),
-                               rbio->crc.compression_type);
-       struct bch_csum csum;
-       int ret = 0;
-
-       /*
-        * reset iterator for checksumming and copying bounced data: here we've
-        * set rbio->compressed_size to the amount of data we actually read,
-        * which was not necessarily the full extent if we were only bouncing
-        * in order to promote
-        */
-       if (rbio->bounce) {
-               src->bi_iter.bi_size    = crc_compressed_size(NULL, &rbio->crc) << 9;
-               src->bi_iter.bi_idx     = 0;
-               src->bi_iter.bi_bvec_done = 0;
-       } else {
-               src->bi_iter = rbio->parent_iter;
-       }
+       struct btree_trans trans;
+       struct btree_iter iter;
+       struct bkey_buf sk;
+       struct bkey_s_c k;
+       int ret;
 
-       csum = bch2_checksum_bio(c, rbio->crc.csum_type, nonce, src);
-       if (bch2_dev_nonfatal_io_err_on(bch2_crc_cmp(rbio->crc.csum, csum),
-                                       rbio->ca,
-                       "data checksum error, inode %llu offset %llu: expected %0llx%0llx got %0llx%0llx (type %u)",
-                       rbio->inode, (u64) rbio->parent_iter.bi_sector << 9,
-                       rbio->crc.csum.hi, rbio->crc.csum.lo, csum.hi, csum.lo,
-                       rbio->crc.csum_type))
-               ret = -EIO;
+       flags &= ~BCH_READ_LAST_FRAGMENT;
+       flags |= BCH_READ_MUST_CLONE;
 
-       /*
-        * If there was a checksum error, still copy the data back - unless it
-        * was compressed, we don't want to decompress bad data:
-        */
-       if (rbio->crc.compression_type != BCH_COMPRESSION_NONE) {
-               if (!ret) {
-                       bch2_encrypt_bio(c, rbio->crc.csum_type, nonce, src);
-                       ret = bch2_bio_uncompress(c, src, dst,
-                                                dst_iter, rbio->crc);
-                       if (ret)
-                               __bcache_io_error(c, "decompression error");
-               }
-       } else if (rbio->bounce) {
-               bio_advance(src, rbio->crc.offset << 9);
+       bch2_bkey_buf_init(&sk);
+       bch2_trans_init(&trans, c, 0, 0);
 
-               /* don't need to decrypt the entire bio: */
-               BUG_ON(src->bi_iter.bi_size < dst_iter.bi_size);
-               src->bi_iter.bi_size = dst_iter.bi_size;
+       bch2_trans_iter_init(&trans, &iter, rbio->data_btree,
+                            rbio->read_pos, BTREE_ITER_SLOTS);
+retry:
+       rbio->bio.bi_status = 0;
 
-               nonce = nonce_add(nonce, rbio->crc.offset << 9);
+       k = bch2_btree_iter_peek_slot(&iter);
+       if (bkey_err(k))
+               goto err;
 
-               bch2_encrypt_bio(c, rbio->crc.csum_type,
-                               nonce, src);
+       bch2_bkey_buf_reassemble(&sk, c, k);
+       k = bkey_i_to_s_c(sk.k);
+       bch2_trans_unlock(&trans);
 
-               bio_copy_data_iter(dst, dst_iter,
-                                  src, src->bi_iter);
-       } else {
-               bch2_encrypt_bio(c, rbio->crc.csum_type, nonce, src);
+       if (!bch2_bkey_matches_ptr(c, k,
+                                  rbio->pick.ptr,
+                                  rbio->data_pos.offset -
+                                  rbio->pick.crc.offset)) {
+               /* extent we wanted to read no longer exists: */
+               rbio->hole = true;
+               goto out;
        }
 
-       return ret;
+       ret = __bch2_read_extent(&trans, rbio, bvec_iter,
+                                rbio->read_pos,
+                                rbio->data_btree,
+                                k, 0, failed, flags);
+       if (ret == READ_RETRY)
+               goto retry;
+       if (ret)
+               goto err;
+out:
+       bch2_rbio_done(rbio);
+       bch2_trans_iter_exit(&trans, &iter);
+       bch2_trans_exit(&trans);
+       bch2_bkey_buf_exit(&sk, c);
+       return;
+err:
+       rbio->bio.bi_status = BLK_STS_IOERR;
+       goto out;
 }
 
-static void bch2_rbio_free(struct bch_read_bio *rbio)
+static void bch2_rbio_retry(struct work_struct *work)
 {
-       struct bch_fs *c = rbio->c;
-       struct bio *bio = &rbio->bio;
-
-       BUG_ON(rbio->ca);
-       BUG_ON(!rbio->split);
+       struct bch_read_bio *rbio =
+               container_of(work, struct bch_read_bio, work);
+       struct bch_fs *c        = rbio->c;
+       struct bvec_iter iter   = rbio->bvec_iter;
+       unsigned flags          = rbio->flags;
+       subvol_inum inum = {
+               .subvol = rbio->subvol,
+               .inum   = rbio->read_pos.inode,
+       };
+       struct bch_io_failures failed = { .nr = 0 };
 
-       if (rbio->promote)
-               kfree(rbio->promote);
-       if (rbio->bounce)
-               bch2_bio_free_pages_pool(c, bio);
+       trace_and_count(c, read_retry, &rbio->bio);
 
-       bio_put(bio);
-}
+       if (rbio->retry == READ_RETRY_AVOID)
+               bch2_mark_io_failure(&failed, &rbio->pick);
 
-static void bch2_rbio_done(struct bch_read_bio *rbio)
-{
-       struct bio *orig = &bch2_rbio_parent(rbio)->bio;
+       rbio->bio.bi_status = 0;
 
-       percpu_ref_put(&rbio->ca->io_ref);
-       rbio->ca = NULL;
+       rbio = bch2_rbio_free(rbio);
 
-       if (rbio->split) {
-               if (rbio->bio.bi_error)
-                       orig->bi_error = rbio->bio.bi_error;
+       flags |= BCH_READ_IN_RETRY;
+       flags &= ~BCH_READ_MAY_PROMOTE;
 
-               bio_endio(orig);
-               bch2_rbio_free(rbio);
+       if (flags & BCH_READ_NODECODE) {
+               bch2_read_retry_nodecode(c, rbio, iter, &failed, flags);
        } else {
-               if (rbio->promote)
-                       kfree(rbio->promote);
+               flags &= ~BCH_READ_LAST_FRAGMENT;
+               flags |= BCH_READ_MUST_CLONE;
 
-               orig->bi_end_io = rbio->orig_bi_end_io;
-               bio_endio_nodec(orig);
+               __bch2_read(c, rbio, iter, inum, &failed, flags);
        }
 }
 
-static void bch2_rbio_error(struct bch_read_bio *rbio, int error)
+static void bch2_rbio_error(struct bch_read_bio *rbio, int retry,
+                           blk_status_t error)
 {
-       bch2_rbio_parent(rbio)->bio.bi_error = error;
-       bch2_rbio_done(rbio);
+       rbio->retry = retry;
+
+       if (rbio->flags & BCH_READ_IN_RETRY)
+               return;
+
+       if (retry == READ_ERR) {
+               rbio = bch2_rbio_free(rbio);
+
+               rbio->bio.bi_status = error;
+               bch2_rbio_done(rbio);
+       } else {
+               bch2_rbio_punt(rbio, bch2_rbio_retry,
+                              RBIO_CONTEXT_UNBOUND, system_unbound_wq);
+       }
 }
 
-static void bch2_rbio_retry(struct bch_fs *c, struct bch_read_bio *rbio)
+static int __bch2_rbio_narrow_crcs(struct btree_trans *trans,
+                                  struct bch_read_bio *rbio)
 {
-       unsigned long flags;
+       struct bch_fs *c = rbio->c;
+       u64 data_offset = rbio->data_pos.offset - rbio->pick.crc.offset;
+       struct bch_extent_crc_unpacked new_crc;
+       struct btree_iter iter;
+       struct bkey_i *new;
+       struct bkey_s_c k;
+       int ret = 0;
+
+       if (crc_is_compressed(rbio->pick.crc))
+               return 0;
+
+       k = bch2_bkey_get_iter(trans, &iter, rbio->data_btree, rbio->data_pos,
+                              BTREE_ITER_SLOTS|BTREE_ITER_INTENT);
+       if ((ret = bkey_err(k)))
+               goto out;
+
+       if (bversion_cmp(k.k->version, rbio->version) ||
+           !bch2_bkey_matches_ptr(c, k, rbio->pick.ptr, data_offset))
+               goto out;
+
+       /* Extent was merged? */
+       if (bkey_start_offset(k.k) < data_offset ||
+           k.k->p.offset > data_offset + rbio->pick.crc.uncompressed_size)
+               goto out;
+
+       if (bch2_rechecksum_bio(c, &rbio->bio, rbio->version,
+                       rbio->pick.crc, NULL, &new_crc,
+                       bkey_start_offset(k.k) - data_offset, k.k->size,
+                       rbio->pick.crc.csum_type)) {
+               bch_err(c, "error verifying existing checksum while narrowing checksum (memory corruption?)");
+               ret = 0;
+               goto out;
+       }
+
+       /*
+        * going to be temporarily appending another checksum entry:
+        */
+       new = bch2_trans_kmalloc(trans, bkey_bytes(k.k) +
+                                sizeof(struct bch_extent_crc128));
+       if ((ret = PTR_ERR_OR_ZERO(new)))
+               goto out;
 
-       percpu_ref_put(&rbio->ca->io_ref);
-       rbio->ca = NULL;
+       bkey_reassemble(new, k);
 
-       spin_lock_irqsave(&c->read_retry_lock, flags);
-       bio_list_add(&c->read_retry_list, &rbio->bio);
-       spin_unlock_irqrestore(&c->read_retry_lock, flags);
-       queue_work(c->wq, &c->read_retry_work);
+       if (!bch2_bkey_narrow_crcs(new, new_crc))
+               goto out;
+
+       ret = bch2_trans_update(trans, &iter, new,
+                               BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE);
+out:
+       bch2_trans_iter_exit(trans, &iter);
+       return ret;
 }
 
-static void cache_promote_done(struct closure *cl)
+static noinline void bch2_rbio_narrow_crcs(struct bch_read_bio *rbio)
 {
-       struct cache_promote_op *op =
-               container_of(cl, struct cache_promote_op, cl);
-
-       bch2_bio_free_pages_pool(op->write.op.c, &op->write.wbio.bio);
-       kfree(op);
+       bch2_trans_do(rbio->c, NULL, NULL, BTREE_INSERT_NOFAIL,
+                     __bch2_rbio_narrow_crcs(&trans, rbio));
 }
 
 /* Inner part that may run in process context */
@@ -990,164 +2361,397 @@ static void __bch2_read_endio(struct work_struct *work)
 {
        struct bch_read_bio *rbio =
                container_of(work, struct bch_read_bio, work);
-       struct bch_fs *c = rbio->c;
+       struct bch_fs *c        = rbio->c;
+       struct bch_dev *ca      = bch_dev_bkey_exists(c, rbio->pick.ptr.dev);
+       struct bio *src         = &rbio->bio;
+       struct bio *dst         = &bch2_rbio_parent(rbio)->bio;
+       struct bvec_iter dst_iter = rbio->bvec_iter;
+       struct bch_extent_crc_unpacked crc = rbio->pick.crc;
+       struct nonce nonce = extent_nonce(rbio->version, crc);
+       unsigned nofs_flags;
+       struct bch_csum csum;
        int ret;
 
-       ret = bio_checksum_uncompress(c, rbio);
-       if (ret) {
-               /*
-                * Checksum error: if the bio wasn't bounced, we may have been
-                * reading into buffers owned by userspace (that userspace can
-                * scribble over) - retry the read, bouncing it this time:
-                */
-               if (!rbio->bounce && (rbio->flags & BCH_READ_USER_MAPPED)) {
-                       rbio->flags |= BCH_READ_FORCE_BOUNCE;
-                       bch2_rbio_retry(c, rbio);
-               } else {
-                       bch2_rbio_error(rbio, -EIO);
-               }
-               return;
+       nofs_flags = memalloc_nofs_save();
+
+       /* Reset iterator for checksumming and copying bounced data: */
+       if (rbio->bounce) {
+               src->bi_iter.bi_size            = crc.compressed_size << 9;
+               src->bi_iter.bi_idx             = 0;
+               src->bi_iter.bi_bvec_done       = 0;
+       } else {
+               src->bi_iter                    = rbio->bvec_iter;
        }
 
-       if (rbio->promote) {
-               struct cache_promote_op *promote = rbio->promote;
-               struct closure *cl = &promote->cl;
+       csum = bch2_checksum_bio(c, crc.csum_type, nonce, src);
+       if (bch2_crc_cmp(csum, rbio->pick.crc.csum) && !c->opts.no_data_io)
+               goto csum_err;
 
-               BUG_ON(!rbio->split || !rbio->bounce);
+       /*
+        * XXX
+        * We need to rework the narrow_crcs path to deliver the read completion
+        * first, and then punt to a different workqueue, otherwise we're
+        * holding up reads while doing btree updates which is bad for memory
+        * reclaim.
+        */
+       if (unlikely(rbio->narrow_crcs))
+               bch2_rbio_narrow_crcs(rbio);
 
-               trace_promote(&rbio->bio);
+       if (rbio->flags & BCH_READ_NODECODE)
+               goto nodecode;
 
-               /* we now own pages: */
-               swap(promote->write.wbio.bio.bi_vcnt, rbio->bio.bi_vcnt);
-               rbio->promote = NULL;
+       /* Adjust crc to point to subset of data we want: */
+       crc.offset     += rbio->offset_into_extent;
+       crc.live_size   = bvec_iter_sectors(rbio->bvec_iter);
 
-               bch2_rbio_done(rbio);
+       if (crc_is_compressed(crc)) {
+               ret = bch2_encrypt_bio(c, crc.csum_type, nonce, src);
+               if (ret)
+                       goto decrypt_err;
 
-               closure_init(cl, &c->cl);
-               closure_call(&promote->write.op.cl, bch2_write, c->wq, cl);
-               closure_return_with_destructor(cl, cache_promote_done);
+               if (bch2_bio_uncompress(c, src, dst, dst_iter, crc) &&
+                   !c->opts.no_data_io)
+                       goto decompression_err;
        } else {
+               /* don't need to decrypt the entire bio: */
+               nonce = nonce_add(nonce, crc.offset << 9);
+               bio_advance(src, crc.offset << 9);
+
+               BUG_ON(src->bi_iter.bi_size < dst_iter.bi_size);
+               src->bi_iter.bi_size = dst_iter.bi_size;
+
+               ret = bch2_encrypt_bio(c, crc.csum_type, nonce, src);
+               if (ret)
+                       goto decrypt_err;
+
+               if (rbio->bounce) {
+                       struct bvec_iter src_iter = src->bi_iter;
+
+                       bio_copy_data_iter(dst, &dst_iter, src, &src_iter);
+               }
+       }
+
+       if (rbio->promote) {
+               /*
+                * Re encrypt data we decrypted, so it's consistent with
+                * rbio->crc:
+                */
+               ret = bch2_encrypt_bio(c, crc.csum_type, nonce, src);
+               if (ret)
+                       goto decrypt_err;
+
+               promote_start(rbio->promote, rbio);
+               rbio->promote = NULL;
+       }
+nodecode:
+       if (likely(!(rbio->flags & BCH_READ_IN_RETRY))) {
+               rbio = bch2_rbio_free(rbio);
                bch2_rbio_done(rbio);
        }
+out:
+       memalloc_nofs_restore(nofs_flags);
+       return;
+csum_err:
+       /*
+        * Checksum error: if the bio wasn't bounced, we may have been
+        * reading into buffers owned by userspace (that userspace can
+        * scribble over) - retry the read, bouncing it this time:
+        */
+       if (!rbio->bounce && (rbio->flags & BCH_READ_USER_MAPPED)) {
+               rbio->flags |= BCH_READ_MUST_BOUNCE;
+               bch2_rbio_error(rbio, READ_RETRY, BLK_STS_IOERR);
+               goto out;
+       }
+
+       bch_err_inum_offset_ratelimited(ca,
+               rbio->read_pos.inode,
+               rbio->read_pos.offset << 9,
+               "data checksum error: expected %0llx:%0llx got %0llx:%0llx (type %s)",
+               rbio->pick.crc.csum.hi, rbio->pick.crc.csum.lo,
+               csum.hi, csum.lo, bch2_csum_types[crc.csum_type]);
+       bch2_io_error(ca);
+       bch2_rbio_error(rbio, READ_RETRY_AVOID, BLK_STS_IOERR);
+       goto out;
+decompression_err:
+       bch_err_inum_offset_ratelimited(c, rbio->read_pos.inode,
+                                       rbio->read_pos.offset << 9,
+                                       "decompression error");
+       bch2_rbio_error(rbio, READ_ERR, BLK_STS_IOERR);
+       goto out;
+decrypt_err:
+       bch_err_inum_offset_ratelimited(c, rbio->read_pos.inode,
+                                       rbio->read_pos.offset << 9,
+                                       "decrypt error");
+       bch2_rbio_error(rbio, READ_ERR, BLK_STS_IOERR);
+       goto out;
 }
 
 static void bch2_read_endio(struct bio *bio)
 {
        struct bch_read_bio *rbio =
                container_of(bio, struct bch_read_bio, bio);
-       struct bch_fs *c = rbio->c;
+       struct bch_fs *c        = rbio->c;
+       struct bch_dev *ca      = bch_dev_bkey_exists(c, rbio->pick.ptr.dev);
+       struct workqueue_struct *wq = NULL;
+       enum rbio_context context = RBIO_CONTEXT_NULL;
+
+       if (rbio->have_ioref) {
+               bch2_latency_acct(ca, rbio->submit_time, READ);
+               percpu_ref_put(&ca->io_ref);
+       }
+
+       if (!rbio->split)
+               rbio->bio.bi_end_io = rbio->end_io;
 
-       if (bch2_dev_nonfatal_io_err_on(bio->bi_error, rbio->ca, "data read")) {
-               /* XXX: retry IO errors when we have another replica */
-               bch2_rbio_error(rbio, bio->bi_error);
+       if (bch2_dev_inum_io_err_on(bio->bi_status, ca,
+                                   rbio->read_pos.inode,
+                                   rbio->read_pos.offset,
+                                   "data read error: %s",
+                              bch2_blk_status_to_str(bio->bi_status))) {
+               bch2_rbio_error(rbio, READ_RETRY_AVOID, bio->bi_status);
                return;
        }
 
-       if (rbio->ptr.cached &&
-           (((rbio->flags & BCH_READ_RETRY_IF_STALE) && race_fault()) ||
-            ptr_stale(rbio->ca, &rbio->ptr))) {
-               atomic_long_inc(&c->read_realloc_races);
+       if (((rbio->flags & BCH_READ_RETRY_IF_STALE) && race_fault()) ||
+           ptr_stale(ca, &rbio->pick.ptr)) {
+               trace_and_count(c, read_reuse_race, &rbio->bio);
 
                if (rbio->flags & BCH_READ_RETRY_IF_STALE)
-                       bch2_rbio_retry(c, rbio);
+                       bch2_rbio_error(rbio, READ_RETRY, BLK_STS_AGAIN);
                else
-                       bch2_rbio_error(rbio, -EINTR);
+                       bch2_rbio_error(rbio, READ_ERR, BLK_STS_AGAIN);
                return;
        }
 
-       if (rbio->crc.compression_type ||
-           bch2_csum_type_is_encryption(rbio->crc.csum_type))
-               queue_work(system_unbound_wq, &rbio->work);
-       else if (rbio->crc.csum_type)
-               queue_work(system_highpri_wq, &rbio->work);
-       else
-               __bch2_read_endio(&rbio->work);
+       if (rbio->narrow_crcs ||
+           rbio->promote ||
+           crc_is_compressed(rbio->pick.crc) ||
+           bch2_csum_type_is_encryption(rbio->pick.crc.csum_type))
+               context = RBIO_CONTEXT_UNBOUND, wq = system_unbound_wq;
+       else if (rbio->pick.crc.csum_type)
+               context = RBIO_CONTEXT_HIGHPRI, wq = system_highpri_wq;
+
+       bch2_rbio_punt(rbio, __bch2_read_endio, context, wq);
 }
 
-static bool should_promote(struct bch_fs *c,
-                          struct extent_pick_ptr *pick, unsigned flags)
+int __bch2_read_indirect_extent(struct btree_trans *trans,
+                               unsigned *offset_into_extent,
+                               struct bkey_buf *orig_k)
 {
-       if (!(flags & BCH_READ_PROMOTE))
-               return false;
+       struct btree_iter iter;
+       struct bkey_s_c k;
+       u64 reflink_offset;
+       int ret;
 
-       if (percpu_ref_is_dying(&c->writes))
-               return false;
+       reflink_offset = le64_to_cpu(bkey_i_to_reflink_p(orig_k->k)->v.idx) +
+               *offset_into_extent;
+
+       k = bch2_bkey_get_iter(trans, &iter, BTREE_ID_reflink,
+                              POS(0, reflink_offset), 0);
+       ret = bkey_err(k);
+       if (ret)
+               goto err;
+
+       if (k.k->type != KEY_TYPE_reflink_v &&
+           k.k->type != KEY_TYPE_indirect_inline_data) {
+               bch_err_inum_offset_ratelimited(trans->c,
+                       orig_k->k->k.p.inode,
+                       orig_k->k->k.p.offset << 9,
+                       "%llu len %u points to nonexistent indirect extent %llu",
+                       orig_k->k->k.p.offset,
+                       orig_k->k->k.size,
+                       reflink_offset);
+               bch2_inconsistent_error(trans->c);
+               ret = -EIO;
+               goto err;
+       }
 
-       return c->fastest_tier &&
-               c->fastest_tier < c->tiers + pick->ca->mi.tier;
+       *offset_into_extent = iter.pos.offset - bkey_start_offset(k.k);
+       bch2_bkey_buf_reassemble(orig_k, trans->c, k);
+err:
+       bch2_trans_iter_exit(trans, &iter);
+       return ret;
 }
 
-void bch2_read_extent_iter(struct bch_fs *c, struct bch_read_bio *orig,
-                         struct bvec_iter iter, struct bkey_s_c k,
-                         struct extent_pick_ptr *pick, unsigned flags)
+static noinline void read_from_stale_dirty_pointer(struct btree_trans *trans,
+                                                  struct bkey_s_c k,
+                                                  struct bch_extent_ptr ptr)
 {
-       struct bch_read_bio *rbio;
-       struct cache_promote_op *promote_op = NULL;
-       unsigned skip = iter.bi_sector - bkey_start_offset(k.k);
-       bool bounce = false, split, read_full = false;
+       struct bch_fs *c = trans->c;
+       struct bch_dev *ca = bch_dev_bkey_exists(c, ptr.dev);
+       struct btree_iter iter;
+       struct printbuf buf = PRINTBUF;
+       int ret;
+
+       bch2_trans_iter_init(trans, &iter, BTREE_ID_alloc,
+                            PTR_BUCKET_POS(c, &ptr),
+                            BTREE_ITER_CACHED);
+
+       prt_printf(&buf, "Attempting to read from stale dirty pointer:");
+       printbuf_indent_add(&buf, 2);
+       prt_newline(&buf);
+
+       bch2_bkey_val_to_text(&buf, c, k);
+       prt_newline(&buf);
 
-       bch2_increment_clock(c, bio_sectors(&orig->bio), READ);
+       prt_printf(&buf, "memory gen: %u", *bucket_gen(ca, iter.pos.offset));
 
-       EBUG_ON(bkey_start_offset(k.k) > iter.bi_sector ||
-               k.k->p.offset < bvec_iter_end_sector(iter));
+       ret = lockrestart_do(trans, bkey_err(k = bch2_btree_iter_peek_slot(&iter)));
+       if (!ret) {
+               prt_newline(&buf);
+               bch2_bkey_val_to_text(&buf, c, k);
+       }
+
+       bch2_fs_inconsistent(c, "%s", buf.buf);
+
+       bch2_trans_iter_exit(trans, &iter);
+       printbuf_exit(&buf);
+}
+
+int __bch2_read_extent(struct btree_trans *trans, struct bch_read_bio *orig,
+                      struct bvec_iter iter, struct bpos read_pos,
+                      enum btree_id data_btree, struct bkey_s_c k,
+                      unsigned offset_into_extent,
+                      struct bch_io_failures *failed, unsigned flags)
+{
+       struct bch_fs *c = trans->c;
+       struct extent_ptr_decoded pick;
+       struct bch_read_bio *rbio = NULL;
+       struct bch_dev *ca = NULL;
+       struct promote_op *promote = NULL;
+       bool bounce = false, read_full = false, narrow_crcs = false;
+       struct bpos data_pos = bkey_start_pos(k.k);
+       int pick_ret;
+
+       if (bkey_extent_is_inline_data(k.k)) {
+               unsigned bytes = min_t(unsigned, iter.bi_size,
+                                      bkey_inline_data_bytes(k.k));
+
+               swap(iter.bi_size, bytes);
+               memcpy_to_bio(&orig->bio, iter, bkey_inline_data_p(k));
+               swap(iter.bi_size, bytes);
+               bio_advance_iter(&orig->bio, &iter, bytes);
+               zero_fill_bio_iter(&orig->bio, iter);
+               goto out_read_done;
+       }
+retry_pick:
+       pick_ret = bch2_bkey_pick_read_device(c, k, failed, &pick);
+
+       /* hole or reservation - just zero fill: */
+       if (!pick_ret)
+               goto hole;
+
+       if (pick_ret < 0) {
+               bch_err_inum_offset_ratelimited(c,
+                               read_pos.inode, read_pos.offset << 9,
+                               "no device to read from");
+               goto err;
+       }
 
-       /* only promote if we're not reading from the fastest tier: */
+       ca = bch_dev_bkey_exists(c, pick.ptr.dev);
 
        /*
-        * XXX: multiple promotes can race with each other, wastefully. Keep a
-        * list of outstanding promotes?
+        * Stale dirty pointers are treated as IO errors, but @failed isn't
+        * allocated unless we're in the retry path - so if we're not in the
+        * retry path, don't check here, it'll be caught in bch2_read_endio()
+        * and we'll end up in the retry path:
         */
-       if (should_promote(c, pick, flags)) {
-               /*
-                * biovec needs to be big enough to hold decompressed data, if
-                * the bch2_write_extent() has to decompress/recompress it:
-                */
-               unsigned sectors =
-                       max_t(unsigned, k.k->size,
-                             crc_uncompressed_size(NULL, &pick->crc));
-               unsigned pages = DIV_ROUND_UP(sectors, PAGE_SECTORS);
-
-               promote_op = kmalloc(sizeof(*promote_op) +
-                               sizeof(struct bio_vec) * pages, GFP_NOIO);
-               if (promote_op) {
-                       struct bio *promote_bio = &promote_op->write.wbio.bio;
-
-                       bio_init(promote_bio);
-                       promote_bio->bi_max_vecs = pages;
-                       promote_bio->bi_io_vec  = promote_bio->bi_inline_vecs;
-                       bounce = true;
-                       /* could also set read_full */
-               }
+       if ((flags & BCH_READ_IN_RETRY) &&
+           !pick.ptr.cached &&
+           unlikely(ptr_stale(ca, &pick.ptr))) {
+               read_from_stale_dirty_pointer(trans, k, pick.ptr);
+               bch2_mark_io_failure(failed, &pick);
+               goto retry_pick;
        }
 
        /*
-        * note: if compression_type and crc_type both == none, then
-        * compressed/uncompressed size is zero
+        * Unlock the iterator while the btree node's lock is still in
+        * cache, before doing the IO:
         */
-       if (pick->crc.compression_type != BCH_COMPRESSION_NONE ||
-           (pick->crc.csum_type != BCH_CSUM_NONE &&
-            (bvec_iter_sectors(iter) != crc_uncompressed_size(NULL, &pick->crc) ||
-             (bch2_csum_type_is_encryption(pick->crc.csum_type) &&
+       bch2_trans_unlock(trans);
+
+       if (flags & BCH_READ_NODECODE) {
+               /*
+                * can happen if we retry, and the extent we were going to read
+                * has been merged in the meantime:
+                */
+               if (pick.crc.compressed_size > orig->bio.bi_vcnt * PAGE_SECTORS)
+                       goto hole;
+
+               iter.bi_size    = pick.crc.compressed_size << 9;
+               goto get_bio;
+       }
+
+       if (!(flags & BCH_READ_LAST_FRAGMENT) ||
+           bio_flagged(&orig->bio, BIO_CHAIN))
+               flags |= BCH_READ_MUST_CLONE;
+
+       narrow_crcs = !(flags & BCH_READ_IN_RETRY) &&
+               bch2_can_narrow_extent_crcs(k, pick.crc);
+
+       if (narrow_crcs && (flags & BCH_READ_USER_MAPPED))
+               flags |= BCH_READ_MUST_BOUNCE;
+
+       EBUG_ON(offset_into_extent + bvec_iter_sectors(iter) > k.k->size);
+
+       if (crc_is_compressed(pick.crc) ||
+           (pick.crc.csum_type != BCH_CSUM_none &&
+            (bvec_iter_sectors(iter) != pick.crc.uncompressed_size ||
+             (bch2_csum_type_is_encryption(pick.crc.csum_type) &&
               (flags & BCH_READ_USER_MAPPED)) ||
-             (flags & BCH_READ_FORCE_BOUNCE)))) {
+             (flags & BCH_READ_MUST_BOUNCE)))) {
                read_full = true;
                bounce = true;
        }
 
-       if (bounce) {
-               unsigned sectors = read_full
-                       ? (crc_compressed_size(NULL, &pick->crc) ?: k.k->size)
-                       : bvec_iter_sectors(iter);
-
-               rbio = container_of(bio_alloc_bioset(GFP_NOIO,
-                                       DIV_ROUND_UP(sectors, PAGE_SECTORS),
-                                       &c->bio_read_split),
-                                   struct bch_read_bio, bio);
+       if (orig->opts.promote_target)
+               promote = promote_alloc(trans, iter, k, &pick, orig->opts, flags,
+                                       &rbio, &bounce, &read_full);
+
+       if (!read_full) {
+               EBUG_ON(crc_is_compressed(pick.crc));
+               EBUG_ON(pick.crc.csum_type &&
+                       (bvec_iter_sectors(iter) != pick.crc.uncompressed_size ||
+                        bvec_iter_sectors(iter) != pick.crc.live_size ||
+                        pick.crc.offset ||
+                        offset_into_extent));
+
+               data_pos.offset += offset_into_extent;
+               pick.ptr.offset += pick.crc.offset +
+                       offset_into_extent;
+               offset_into_extent              = 0;
+               pick.crc.compressed_size        = bvec_iter_sectors(iter);
+               pick.crc.uncompressed_size      = bvec_iter_sectors(iter);
+               pick.crc.offset                 = 0;
+               pick.crc.live_size              = bvec_iter_sectors(iter);
+               offset_into_extent              = 0;
+       }
+get_bio:
+       if (rbio) {
+               /*
+                * promote already allocated bounce rbio:
+                * promote needs to allocate a bio big enough for uncompressing
+                * data in the write path, but we're not going to use it all
+                * here:
+                */
+               EBUG_ON(rbio->bio.bi_iter.bi_size <
+                      pick.crc.compressed_size << 9);
+               rbio->bio.bi_iter.bi_size =
+                       pick.crc.compressed_size << 9;
+       } else if (bounce) {
+               unsigned sectors = pick.crc.compressed_size;
+
+               rbio = rbio_init(bio_alloc_bioset(NULL,
+                                                 DIV_ROUND_UP(sectors, PAGE_SECTORS),
+                                                 0,
+                                                 GFP_NOFS,
+                                                 &c->bio_read_split),
+                                orig->opts);
 
                bch2_bio_alloc_pages_pool(c, &rbio->bio, sectors << 9);
-               split = true;
-       } else if (!(flags & BCH_READ_MAY_REUSE_BIO) ||
-                  !(flags & BCH_READ_IS_LAST)) {
+               rbio->bounce    = true;
+               rbio->split     = true;
+       } else if (flags & BCH_READ_MUST_CLONE) {
                /*
                 * Have to clone if there were any splits, due to error
                 * reporting issues (if a split errored, and retrying didn't
@@ -1156,225 +2760,292 @@ void bch2_read_extent_iter(struct bch_fs *c, struct bch_read_bio *orig,
                 * from the whole bio, in which case we don't want to retry and
                 * lose the error)
                 */
-               rbio = container_of(bio_clone_fast(&orig->bio,
-                                       GFP_NOIO, &c->bio_read_split),
-                                   struct bch_read_bio, bio);
+               rbio = rbio_init(bio_alloc_clone(NULL, &orig->bio, GFP_NOFS,
+                                                &c->bio_read_split),
+                                orig->opts);
                rbio->bio.bi_iter = iter;
-               split = true;
+               rbio->split     = true;
        } else {
                rbio = orig;
                rbio->bio.bi_iter = iter;
-               split = false;
-               BUG_ON(bio_flagged(&rbio->bio, BIO_CHAIN));
+               EBUG_ON(bio_flagged(&rbio->bio, BIO_CHAIN));
        }
 
-       if (!(flags & BCH_READ_IS_LAST))
-               __bio_inc_remaining(&orig->bio);
+       EBUG_ON(bio_sectors(&rbio->bio) != pick.crc.compressed_size);
 
-       if (split)
+       rbio->c                 = c;
+       rbio->submit_time       = local_clock();
+       if (rbio->split)
                rbio->parent    = orig;
        else
-               rbio->orig_bi_end_io = orig->bio.bi_end_io;
-       rbio->parent_iter       = iter;
-
+               rbio->end_io    = orig->bio.bi_end_io;
+       rbio->bvec_iter         = iter;
+       rbio->offset_into_extent= offset_into_extent;
        rbio->flags             = flags;
-       rbio->bounce            = bounce;
-       rbio->split             = split;
-       rbio->c                 = c;
-       rbio->ca                = pick->ca;
-       rbio->ptr               = pick->ptr;
-       rbio->crc               = pick->crc;
-       /*
-        * crc.compressed_size will be 0 if there wasn't any checksum
-        * information, also we need to stash the original size of the bio if we
-        * bounced (which isn't necessarily the original key size, if we bounced
-        * only for promoting)
-        */
-       rbio->crc._compressed_size = bio_sectors(&rbio->bio) - 1;
+       rbio->have_ioref        = pick_ret > 0 && bch2_dev_get_ioref(ca, READ);
+       rbio->narrow_crcs       = narrow_crcs;
+       rbio->hole              = 0;
+       rbio->retry             = 0;
+       rbio->context           = 0;
+       /* XXX: only initialize this if needed */
+       rbio->devs_have         = bch2_bkey_devs(k);
+       rbio->pick              = pick;
+       rbio->subvol            = orig->subvol;
+       rbio->read_pos          = read_pos;
+       rbio->data_btree        = data_btree;
+       rbio->data_pos          = data_pos;
        rbio->version           = k.k->version;
-       rbio->promote           = promote_op;
-       rbio->inode             = k.k->p.inode;
-       INIT_WORK(&rbio->work, __bch2_read_endio);
+       rbio->promote           = promote;
+       INIT_WORK(&rbio->work, NULL);
 
-       rbio->bio.bi_bdev       = pick->ca->disk_sb.bdev;
        rbio->bio.bi_opf        = orig->bio.bi_opf;
-       rbio->bio.bi_iter.bi_sector = pick->ptr.offset;
+       rbio->bio.bi_iter.bi_sector = pick.ptr.offset;
        rbio->bio.bi_end_io     = bch2_read_endio;
 
-       if (promote_op) {
-               struct bio *promote_bio = &promote_op->write.wbio.bio;
-
-               promote_bio->bi_iter = rbio->bio.bi_iter;
-               memcpy(promote_bio->bi_io_vec, rbio->bio.bi_io_vec,
-                      sizeof(struct bio_vec) * rbio->bio.bi_vcnt);
-
-               bch2_migrate_write_init(c, &promote_op->write,
-                                      &c->promote_write_point,
-                                      k, NULL,
-                                      BCH_WRITE_ALLOC_NOWAIT|
-                                      BCH_WRITE_CACHED);
-               promote_op->write.promote = true;
-
-               if (rbio->crc.compression_type) {
-                       promote_op->write.op.flags |= BCH_WRITE_DATA_COMPRESSED;
-                       promote_op->write.op.crc = rbio->crc;
-                       promote_op->write.op.size = k.k->size;
-               } else if (read_full) {
-                       /*
-                        * Adjust bio to correspond to _live_ portion of @k -
-                        * which might be less than what we're actually reading:
-                        */
-                       bio_advance(promote_bio, rbio->crc.offset << 9);
-                       BUG_ON(bio_sectors(promote_bio) < k.k->size);
-                       promote_bio->bi_iter.bi_size = k.k->size << 9;
+       if (rbio->bounce)
+               trace_and_count(c, read_bounce, &rbio->bio);
+
+       this_cpu_add(c->counters[BCH_COUNTER_io_read], bio_sectors(&rbio->bio));
+       bch2_increment_clock(c, bio_sectors(&rbio->bio), READ);
+
+       /*
+        * If it's being moved internally, we don't want to flag it as a cache
+        * hit:
+        */
+       if (pick.ptr.cached && !(flags & BCH_READ_NODECODE))
+               bch2_bucket_io_time_reset(trans, pick.ptr.dev,
+                       PTR_BUCKET_NR(ca, &pick.ptr), READ);
+
+       if (!(flags & (BCH_READ_IN_RETRY|BCH_READ_LAST_FRAGMENT))) {
+               bio_inc_remaining(&orig->bio);
+               trace_and_count(c, read_split, &orig->bio);
+       }
+
+       if (!rbio->pick.idx) {
+               if (!rbio->have_ioref) {
+                       bch_err_inum_offset_ratelimited(c,
+                                       read_pos.inode,
+                                       read_pos.offset << 9,
+                                       "no device to read from");
+                       bch2_rbio_error(rbio, READ_RETRY_AVOID, BLK_STS_IOERR);
+                       goto out;
+               }
+
+               this_cpu_add(ca->io_done->sectors[READ][BCH_DATA_user],
+                            bio_sectors(&rbio->bio));
+               bio_set_dev(&rbio->bio, ca->disk_sb.bdev);
+
+               if (unlikely(c->opts.no_data_io)) {
+                       if (likely(!(flags & BCH_READ_IN_RETRY)))
+                               bio_endio(&rbio->bio);
                } else {
-                       /*
-                        * Set insert pos to correspond to what we're actually
-                        * reading:
-                        */
-                       promote_op->write.op.pos.offset = iter.bi_sector;
+                       if (likely(!(flags & BCH_READ_IN_RETRY)))
+                               submit_bio(&rbio->bio);
+                       else
+                               submit_bio_wait(&rbio->bio);
                }
 
-               promote_bio->bi_iter.bi_sector =
-                       promote_op->write.op.pos.offset;
+               /*
+                * We just submitted IO which may block, we expect relock fail
+                * events and shouldn't count them:
+                */
+               trans->notrace_relock_fail = true;
+       } else {
+               /* Attempting reconstruct read: */
+               if (bch2_ec_read_extent(c, rbio)) {
+                       bch2_rbio_error(rbio, READ_RETRY_AVOID, BLK_STS_IOERR);
+                       goto out;
+               }
+
+               if (likely(!(flags & BCH_READ_IN_RETRY)))
+                       bio_endio(&rbio->bio);
        }
+out:
+       if (likely(!(flags & BCH_READ_IN_RETRY))) {
+               return 0;
+       } else {
+               int ret;
 
-       /* _after_ promete stuff has looked at rbio->crc.offset */
-       if (read_full)
-               rbio->crc.offset += skip;
-       else
-               rbio->bio.bi_iter.bi_sector += skip;
+               rbio->context = RBIO_CONTEXT_UNBOUND;
+               bch2_read_endio(&rbio->bio);
 
-       rbio->submit_time_us = local_clock_us();
+               ret = rbio->retry;
+               rbio = bch2_rbio_free(rbio);
 
-       if (bounce)
-               trace_read_bounce(&rbio->bio);
+               if (ret == READ_RETRY_AVOID) {
+                       bch2_mark_io_failure(failed, &pick);
+                       ret = READ_RETRY;
+               }
+
+               if (!ret)
+                       goto out_read_done;
+
+               return ret;
+       }
 
-       if (!(flags & BCH_READ_IS_LAST))
-               trace_read_split(&rbio->bio);
+err:
+       if (flags & BCH_READ_IN_RETRY)
+               return READ_ERR;
+
+       orig->bio.bi_status = BLK_STS_IOERR;
+       goto out_read_done;
 
-       generic_make_request(&rbio->bio);
+hole:
+       /*
+        * won't normally happen in the BCH_READ_NODECODE
+        * (bch2_move_extent()) path, but if we retry and the extent we wanted
+        * to read no longer exists we have to signal that:
+        */
+       if (flags & BCH_READ_NODECODE)
+               orig->hole = true;
+
+       zero_fill_bio_iter(&orig->bio, iter);
+out_read_done:
+       if (flags & BCH_READ_LAST_FRAGMENT)
+               bch2_rbio_done(orig);
+       return 0;
 }
 
-static void bch2_read_iter(struct bch_fs *c, struct bch_read_bio *rbio,
-                         struct bvec_iter bvec_iter, u64 inode,
-                         unsigned flags)
+void __bch2_read(struct bch_fs *c, struct bch_read_bio *rbio,
+                struct bvec_iter bvec_iter, subvol_inum inum,
+                struct bch_io_failures *failed, unsigned flags)
 {
-       struct bio *bio = &rbio->bio;
+       struct btree_trans trans;
        struct btree_iter iter;
+       struct bkey_buf sk;
        struct bkey_s_c k;
+       u32 snapshot;
        int ret;
 
-       for_each_btree_key_with_holes(&iter, c, BTREE_ID_EXTENTS,
-                                     POS(inode, bvec_iter.bi_sector), k) {
-               BKEY_PADDED(k) tmp;
-               struct extent_pick_ptr pick;
-               unsigned bytes, sectors;
-               bool is_last;
+       BUG_ON(flags & BCH_READ_NODECODE);
+
+       bch2_bkey_buf_init(&sk);
+       bch2_trans_init(&trans, c, 0, 0);
+retry:
+       bch2_trans_begin(&trans);
+       iter = (struct btree_iter) { NULL };
+
+       ret = bch2_subvolume_get_snapshot(&trans, inum.subvol, &snapshot);
+       if (ret)
+               goto err;
+
+       bch2_trans_iter_init(&trans, &iter, BTREE_ID_extents,
+                            SPOS(inum.inum, bvec_iter.bi_sector, snapshot),
+                            BTREE_ITER_SLOTS);
+       while (1) {
+               unsigned bytes, sectors, offset_into_extent;
+               enum btree_id data_btree = BTREE_ID_extents;
 
                /*
-                * Unlock the iterator while the btree node's lock is still in
-                * cache, before doing the IO:
+                * read_extent -> io_time_reset may cause a transaction restart
+                * without returning an error, we need to check for that here:
                 */
-               bkey_reassemble(&tmp.k, k);
-               k = bkey_i_to_s_c(&tmp.k);
-               bch2_btree_iter_unlock(&iter);
-
-               bch2_extent_pick_ptr(c, k, &pick);
-               if (IS_ERR(pick.ca)) {
-                       bcache_io_error(c, bio, "no device to read from");
-                       bio_endio(bio);
-                       return;
-               }
+               ret = bch2_trans_relock(&trans);
+               if (ret)
+                       break;
 
-               sectors = min_t(u64, k.k->p.offset,
-                               bvec_iter_end_sector(bvec_iter)) -
-                       bvec_iter.bi_sector;
-               bytes = sectors << 9;
-               is_last = bytes == bvec_iter.bi_size;
-               swap(bvec_iter.bi_size, bytes);
+               bch2_btree_iter_set_pos(&iter,
+                               POS(inum.inum, bvec_iter.bi_sector));
 
-               if (is_last)
-                       flags |= BCH_READ_IS_LAST;
+               k = bch2_btree_iter_peek_slot(&iter);
+               ret = bkey_err(k);
+               if (ret)
+                       break;
 
-               if (pick.ca) {
-                       PTR_BUCKET(pick.ca, &pick.ptr)->read_prio =
-                               c->prio_clock[READ].hand;
+               offset_into_extent = iter.pos.offset -
+                       bkey_start_offset(k.k);
+               sectors = k.k->size - offset_into_extent;
 
-                       bch2_read_extent_iter(c, rbio, bvec_iter,
-                                            k, &pick, flags);
+               bch2_bkey_buf_reassemble(&sk, c, k);
 
-                       flags &= ~BCH_READ_MAY_REUSE_BIO;
-               } else {
-                       zero_fill_bio_iter(bio, bvec_iter);
+               ret = bch2_read_indirect_extent(&trans, &data_btree,
+                                       &offset_into_extent, &sk);
+               if (ret)
+                       break;
 
-                       if (is_last)
-                               bio_endio(bio);
-               }
+               k = bkey_i_to_s_c(sk.k);
+
+               /*
+                * With indirect extents, the amount of data to read is the min
+                * of the original extent and the indirect extent:
+                */
+               sectors = min(sectors, k.k->size - offset_into_extent);
+
+               bytes = min(sectors, bvec_iter_sectors(bvec_iter)) << 9;
+               swap(bvec_iter.bi_size, bytes);
+
+               if (bvec_iter.bi_size == bytes)
+                       flags |= BCH_READ_LAST_FRAGMENT;
 
-               if (is_last)
-                       return;
+               ret = __bch2_read_extent(&trans, rbio, bvec_iter, iter.pos,
+                                        data_btree, k,
+                                        offset_into_extent, failed, flags);
+               if (ret)
+                       break;
+
+               if (flags & BCH_READ_LAST_FRAGMENT)
+                       break;
 
                swap(bvec_iter.bi_size, bytes);
-               bio_advance_iter(bio, &bvec_iter, bytes);
+               bio_advance_iter(&rbio->bio, &bvec_iter, bytes);
+
+               ret = btree_trans_too_many_iters(&trans);
+               if (ret)
+                       break;
        }
+err:
+       bch2_trans_iter_exit(&trans, &iter);
 
-       /*
-        * If we get here, it better have been because there was an error
-        * reading a btree node
-        */
-       ret = bch2_btree_iter_unlock(&iter);
-       BUG_ON(!ret);
-       bcache_io_error(c, bio, "btree IO error %i", ret);
-       bio_endio(bio);
+       if (bch2_err_matches(ret, BCH_ERR_transaction_restart) ||
+           ret == READ_RETRY ||
+           ret == READ_RETRY_AVOID)
+               goto retry;
+
+       bch2_trans_exit(&trans);
+       bch2_bkey_buf_exit(&sk, c);
+
+       if (ret) {
+               bch_err_inum_offset_ratelimited(c, inum.inum,
+                                               bvec_iter.bi_sector << 9,
+                                               "read error %i from btree lookup", ret);
+               rbio->bio.bi_status = BLK_STS_IOERR;
+               bch2_rbio_done(rbio);
+       }
 }
 
-void bch2_read(struct bch_fs *c, struct bch_read_bio *bio, u64 inode)
+void bch2_fs_io_exit(struct bch_fs *c)
 {
-       bch2_read_iter(c, bio, bio->bio.bi_iter, inode,
-                     BCH_READ_RETRY_IF_STALE|
-                     BCH_READ_PROMOTE|
-                     BCH_READ_MAY_REUSE_BIO|
-                     BCH_READ_USER_MAPPED);
+       if (c->promote_table.tbl)
+               rhashtable_destroy(&c->promote_table);
+       mempool_exit(&c->bio_bounce_pages);
+       bioset_exit(&c->bio_write);
+       bioset_exit(&c->bio_read_split);
+       bioset_exit(&c->bio_read);
 }
 
-/**
- * bch_read_retry - re-submit a bio originally from bch2_read()
- */
-static void bch2_read_retry(struct bch_fs *c, struct bch_read_bio *rbio)
+int bch2_fs_io_init(struct bch_fs *c)
 {
-       struct bch_read_bio *parent = bch2_rbio_parent(rbio);
-       struct bvec_iter iter = rbio->parent_iter;
-       unsigned flags = rbio->flags;
-       u64 inode = rbio->inode;
-
-       trace_read_retry(&rbio->bio);
-
-       if (rbio->split)
-               bch2_rbio_free(rbio);
-       else
-               rbio->bio.bi_end_io = rbio->orig_bi_end_io;
+       if (bioset_init(&c->bio_read, 1, offsetof(struct bch_read_bio, bio),
+                       BIOSET_NEED_BVECS))
+               return -BCH_ERR_ENOMEM_bio_read_init;
 
-       bch2_read_iter(c, parent, iter, inode, flags);
-}
+       if (bioset_init(&c->bio_read_split, 1, offsetof(struct bch_read_bio, bio),
+                       BIOSET_NEED_BVECS))
+               return -BCH_ERR_ENOMEM_bio_read_split_init;
 
-void bch2_read_retry_work(struct work_struct *work)
-{
-       struct bch_fs *c = container_of(work, struct bch_fs,
-                                          read_retry_work);
-       struct bch_read_bio *rbio;
-       struct bio *bio;
-       unsigned long flags;
+       if (bioset_init(&c->bio_write, 1, offsetof(struct bch_write_bio, bio),
+                       BIOSET_NEED_BVECS))
+               return -BCH_ERR_ENOMEM_bio_write_init;
 
-       while (1) {
-               spin_lock_irqsave(&c->read_retry_lock, flags);
-               bio = bio_list_pop(&c->read_retry_list);
-               spin_unlock_irqrestore(&c->read_retry_lock, flags);
+       if (mempool_init_page_pool(&c->bio_bounce_pages,
+                                  max_t(unsigned,
+                                        c->opts.btree_node_size,
+                                        c->opts.encoded_extent_max) /
+                                  PAGE_SIZE, 0))
+               return -BCH_ERR_ENOMEM_bio_bounce_pages_init;
 
-               if (!bio)
-                       break;
+       if (rhashtable_init(&c->promote_table, &bch_promote_params))
+               return -BCH_ERR_ENOMEM_promote_table_init;
 
-               rbio = container_of(bio, struct bch_read_bio, bio);
-               bch2_read_retry(c, rbio);
-       }
+       return 0;
 }