]> git.sesse.net Git - bcachefs-tools-debian/blobdiff - libbcachefs/io.c
cmd_set_passphrase: revoke the invalidated key
[bcachefs-tools-debian] / libbcachefs / io.c
index 7cc26af16a1bd1aec717c54d88c287f9b7ae1402..3c614c864b6eef698c9dac8ebc1884d7f4a61bed 100644 (file)
@@ -7,14 +7,16 @@
  */
 
 #include "bcachefs.h"
+#include "alloc_background.h"
 #include "alloc_foreground.h"
-#include "bkey_on_stack.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 "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)
 {
@@ -46,7 +60,9 @@ static bool bch2_target_congested(struct bch_fs *c, u16 target)
                return false;
 
        rcu_read_lock();
-       devs = bch2_target_to_mask(c, target);
+       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)
@@ -109,7 +125,7 @@ void bch2_latency_acct(struct bch_dev *ca, u64 submit_time, int rw)
                 * the time:
                 */
                if (abs((int) (old - io_latency)) < (old >> 1) &&
-                   now & ~(~0 << 5))
+                   now & ~(~0U << 5))
                        break;
 
                new = ewma_add(old, io_latency, 5);
@@ -120,6 +136,15 @@ void bch2_latency_acct(struct bch_dev *ca, u64 submit_time, int rw)
        __bch2_time_stats_update(&ca->io_latency[rw], submit_time, now);
 }
 
+#else
+
+static bool bch2_target_congested(struct bch_fs *c, u16 target)
+{
+       return false;
+}
+
+#endif
+
 /* Allocate, free from mempool: */
 
 void bch2_bio_free_pages_pool(struct bch_fs *c, struct bio *bio)
@@ -138,7 +163,7 @@ static struct page *__bio_alloc_page_pool(struct bch_fs *c, bool *using_mempool)
        struct page *page;
 
        if (likely(!*using_mempool)) {
-               page = alloc_page(GFP_NOIO);
+               page = alloc_page(GFP_NOFS);
                if (unlikely(!page)) {
                        mutex_lock(&c->bio_bounce_pages_lock);
                        *using_mempool = true;
@@ -147,7 +172,7 @@ static struct page *__bio_alloc_page_pool(struct bch_fs *c, bool *using_mempool)
                }
        } else {
 pool_alloc:
-               page = mempool_alloc(&c->bio_bounce_pages, GFP_NOIO);
+               page = mempool_alloc(&c->bio_bounce_pages, GFP_NOFS);
        }
 
        return page;
@@ -160,7 +185,7 @@ void bch2_bio_alloc_pages_pool(struct bch_fs *c, struct bio *bio,
 
        while (size) {
                struct page *page = __bio_alloc_page_pool(c, &using_mempool);
-               unsigned len = min(PAGE_SIZE, size);
+               unsigned len = min_t(size_t, PAGE_SIZE, size);
 
                BUG_ON(!bio_add_page(bio, page, len, 0));
                size -= len;
@@ -172,255 +197,432 @@ void bch2_bio_alloc_pages_pool(struct bch_fs *c, struct bio *bio,
 
 /* Extent update path: */
 
-static int sum_sector_overwrites(struct btree_trans *trans,
-                                struct btree_iter *extent_iter,
-                                struct bkey_i *new,
-                                bool may_allocate,
-                                bool *maybe_extending,
-                                s64 *delta)
+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 btree_iter *iter;
+       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;
 
-       *maybe_extending = true;
-       *delta = 0;
+       *usage_increasing       = false;
+       *i_sectors_delta        = 0;
+       *disk_sectors_delta     = 0;
 
-       iter = bch2_trans_copy_iter(trans, extent_iter);
-       if (IS_ERR(iter))
-               return PTR_ERR(iter);
+       bch2_trans_copy_iter(&iter, extent_iter);
 
-       for_each_btree_key_continue(iter, BTREE_ITER_SLOTS, old, ret) {
-               if (!may_allocate &&
-                   bch2_bkey_nr_ptrs_fully_allocated(old) <
-                   bch2_bkey_nr_ptrs_allocated(bkey_i_to_s_c(new))) {
-                       ret = -ENOSPC;
-                       break;
-               }
+       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));
 
-               *delta += (min(new->k.p.offset,
-                             old.k->p.offset) -
-                         max(bkey_start_offset(&new->k),
-                             bkey_start_offset(old.k))) *
+               *i_sectors_delta += sectors *
                        (bkey_extent_is_allocation(&new->k) -
                         bkey_extent_is_allocation(old.k));
 
-               if (bkey_cmp(old.k->p, new->k.p) >= 0) {
-                       /*
-                        * Check if there's already data above where we're
-                        * going to be writing to - this means we're definitely
-                        * not extending the file:
-                        *
-                        * Note that it's not sufficient to check if there's
-                        * data up to the sector offset we're going to be
-                        * writing to, because i_size could be up to one block
-                        * less:
-                        */
-                       if (!bkey_cmp(old.k->p, new->k.p))
-                               old = bch2_btree_iter_next(iter);
+               *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;
 
-                       if (old.k && !bkey_err(old) &&
-                           old.k->p.inode == extent_iter->pos.inode &&
-                           bkey_extent_is_data(old.k))
-                               *maybe_extending = false;
+               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 (bkey_ge(old.k->p, new->k.p))
                        break;
-               }
        }
 
-       bch2_trans_iter_put(trans, iter);
+       bch2_trans_iter_exit(trans, &iter);
+       return ret;
+}
+
+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 btree_iter iter;
+       struct bkey_i *k;
+       struct bkey_i_inode_v3 *inode;
+       unsigned inode_update_flags = BTREE_UPDATE_NOJOURNAL;
+       int ret;
+
+       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;
+       }
+
+       inode = bkey_i_to_inode_v3(k);
+
+       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;
+       }
+
+       if (i_sectors_delta) {
+               le64_add_cpu(&inode->v.bi_sectors, i_sectors_delta);
+               inode_update_flags = 0;
+       }
+
+       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;
 }
 
 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 *journal_seq,
                       u64 new_i_size,
-                      s64 *i_sectors_delta)
+                      s64 *i_sectors_delta_total,
+                      bool check_enospc)
 {
-       /* this must live until after bch2_trans_commit(): */
-       struct bkey_inode_buf inode_p;
-       bool extending = false;
-       s64 delta = 0;
+       struct bpos next_pos;
+       bool usage_increasing;
+       s64 i_sectors_delta = 0, disk_sectors_delta = 0;
        int ret;
 
-       ret = bch2_extent_trim_atomic(k, 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 = sum_sector_overwrites(trans, iter, k,
-                       disk_res && disk_res->sectors != 0,
-                       &extending, &delta);
+       ret = bch2_extent_trim_atomic(trans, iter, k);
        if (ret)
                return ret;
 
-       new_i_size = extending
-               ? min(k->k.p.offset << 9, new_i_size)
-               : 0;
+       next_pos = k->k.p;
 
-       if (delta || new_i_size) {
-               struct btree_iter *inode_iter;
-               struct bch_inode_unpacked inode_u;
+       ret = bch2_sum_sector_overwrites(trans, iter, k,
+                       &usage_increasing,
+                       &i_sectors_delta,
+                       &disk_sectors_delta);
+       if (ret)
+               return ret;
 
-               inode_iter = bch2_inode_peek(trans, &inode_u,
-                               k->k.p.inode, BTREE_ITER_INTENT);
-               if (IS_ERR(inode_iter))
-                       return PTR_ERR(inode_iter);
+       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;
+       }
+
+       /*
+        * 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;
+}
+
+/* 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_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;
+
+       bch2_bkey_buf_init(&old);
+       bch2_bkey_buf_init(&new);
+       closure_init_stack(&cl);
+
+       k = bch2_btree_iter_peek_slot(iter);
+       ret = bkey_err(k);
+       if (ret)
+               return ret;
+
+       sectors = min_t(u64, sectors, k.k->p.offset - iter->pos.offset);
+
+       if (!have_reservation) {
+               unsigned new_replicas =
+                       max(0, (int) opts.data_replicas -
+                           (int) bch2_bkey_nr_ptrs_fully_allocated(k));
                /*
-                * XXX:
-                * writeback can race a bit with truncate, because truncate
-                * first updates the inode then truncates the pagecache. This is
-                * ugly, but lets us preserve the invariant that the in memory
-                * i_size is always >= the on disk i_size.
-                *
-               BUG_ON(new_i_size > inode_u.bi_size &&
-                      (inode_u.bi_flags & BCH_INODE_I_SIZE_DIRTY));
+                * Get a disk reservation before (in the nocow case) calling
+                * into the allocator:
                 */
-               BUG_ON(new_i_size > inode_u.bi_size && !extending);
+               ret = bch2_disk_reservation_get(c, &disk_res, sectors, new_replicas, 0);
+               if (unlikely(ret))
+                       goto err;
 
-               if (!(inode_u.bi_flags & BCH_INODE_I_SIZE_DIRTY) &&
-                   new_i_size > inode_u.bi_size)
-                       inode_u.bi_size = new_i_size;
-               else
-                       new_i_size = 0;
+               bch2_bkey_buf_reassemble(&old, c, k);
+       }
 
-               inode_u.bi_sectors += delta;
+       if (have_reservation) {
+               if (!bch2_extents_match(k, bkey_i_to_s_c(old.k)))
+                       goto err;
 
-               if (delta || new_i_size) {
-                       bch2_inode_pack(&inode_p, &inode_u);
-                       bch2_trans_update(trans, inode_iter,
-                                         &inode_p.inode.k_i, 0);
-               }
+               bch2_key_resize(&new.k->k, sectors);
+       } else if (!unwritten) {
+               struct bkey_i_reservation *reservation;
+
+               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 {
+               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_trans_iter_put(trans, inode_iter);
+               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;
        }
 
-       bch2_trans_update(trans, iter, k, 0);
+       have_reservation = true;
 
-       ret = bch2_trans_commit(trans, disk_res, journal_seq,
-                               BTREE_INSERT_NOCHECK_RW|
-                               BTREE_INSERT_NOFAIL|
-                               BTREE_INSERT_USE_RESERVE);
-       if (!ret && i_sectors_delta)
-               *i_sectors_delta += delta;
+       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);
+       }
 
        return ret;
 }
 
+/*
+ * Returns -BCH_ERR_transacton_restart if we had to drop locks:
+ */
 int bch2_fpunch_at(struct btree_trans *trans, struct btree_iter *iter,
-                  struct bpos end, u64 *journal_seq,
+                  subvol_inum inum, u64 end,
                   s64 *i_sectors_delta)
 {
        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 ((k = bch2_btree_iter_peek(iter)).k &&
-              bkey_cmp(iter->pos, end) < 0) {
+       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 (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);
+
+               /*
+                * peek_upto() doesn't have ideal semantics for extents:
+                */
+               k = bch2_btree_iter_peek_upto(iter, end_pos);
+               if (!k.k)
+                       break;
+
                ret = bkey_err(k);
                if (ret)
-                       goto btree_err;
+                       continue;
 
                bkey_init(&delete.k);
                delete.k.p = iter->pos;
 
                /* create the biggest key we can */
                bch2_key_resize(&delete.k, max_sectors);
-               bch2_cut_back(end, &delete);
+               bch2_cut_back(end_pos, &delete);
 
-               ret = bch2_extent_update(trans, iter, &delete,
-                               &disk_res, journal_seq,
-                               0, i_sectors_delta);
+               ret = bch2_extent_update(trans, inum, iter, &delete,
+                               &disk_res, 0, i_sectors_delta, false);
                bch2_disk_reservation_put(c, &disk_res);
-btree_err:
-               if (ret == -EINTR) {
-                       ret2 = ret;
-                       ret = 0;
-               }
-               if (ret)
-                       break;
-       }
-
-       if (bkey_cmp(iter->pos, end) > 0) {
-               bch2_btree_iter_set_pos(iter, end);
-               ret = bch2_btree_iter_traverse(iter);
        }
 
        return ret ?: ret2;
 }
 
-int bch2_fpunch(struct bch_fs *c, u64 inum, u64 start, u64 end,
-               u64 *journal_seq, s64 *i_sectors_delta)
+int bch2_fpunch(struct bch_fs *c, subvol_inum inum, u64 start, u64 end,
+               s64 *i_sectors_delta)
 {
        struct btree_trans trans;
-       struct btree_iter *iter;
-       int ret = 0;
+       struct btree_iter iter;
+       int ret;
 
        bch2_trans_init(&trans, c, BTREE_ITER_MAX, 1024);
-       iter = bch2_trans_get_iter(&trans, BTREE_ID_EXTENTS,
-                                  POS(inum, start),
-                                  BTREE_ITER_INTENT);
+       bch2_trans_iter_init(&trans, &iter, BTREE_ID_extents,
+                            POS(inum.inum, start),
+                            BTREE_ITER_INTENT);
 
-       ret = bch2_fpunch_at(&trans, iter, POS(inum, end),
-                            journal_seq, i_sectors_delta);
+       ret = bch2_fpunch_at(&trans, &iter, inum, end, i_sectors_delta);
+
+       bch2_trans_iter_exit(&trans, &iter);
        bch2_trans_exit(&trans);
 
-       if (ret == -EINTR)
+       if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
                ret = 0;
 
        return ret;
 }
 
-int bch2_write_index_default(struct bch_write_op *op)
+static int bch2_write_index_default(struct bch_write_op *op)
 {
        struct bch_fs *c = op->c;
-       struct bkey_on_stack sk;
+       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;
+       struct btree_iter iter;
+       subvol_inum inum = {
+               .subvol = op->subvol,
+               .inum   = k->k.p.inode,
+       };
        int ret;
 
-       bkey_on_stack_init(&sk);
-       bch2_trans_init(&trans, c, BTREE_ITER_MAX, 1024);
+       BUG_ON(!inum.subvol);
 
-       iter = bch2_trans_get_iter(&trans, BTREE_ID_EXTENTS,
-                                  bkey_start_pos(&k->k),
-                                  BTREE_ITER_SLOTS|BTREE_ITER_INTENT);
+       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_subvolume_get_snapshot(&trans, inum.subvol,
+                                                 &sk.k->k.p.snapshot);
+               if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
+                       continue;
+               if (ret)
+                       break;
 
-               bkey_on_stack_realloc(&sk, c, k->k.u64s);
-               bkey_copy(sk.k, k);
-               bch2_cut_front(iter->pos, sk.k);
+               bch2_trans_iter_init(&trans, &iter, BTREE_ID_extents,
+                                    bkey_start_pos(&sk.k->k),
+                                    BTREE_ITER_SLOTS|BTREE_ITER_INTENT);
 
-               ret = bch2_extent_update(&trans, iter, sk.k,
-                                        &op->res, op_journal_seq(op),
-                                        op->new_i_size, &op->i_sectors_delta);
-               if (ret == -EINTR)
+               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);
+
+               if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
                        continue;
                if (ret)
                        break;
 
-               if (bkey_cmp(iter->pos, k->k.p) >= 0)
-                       bch2_keylist_pop_front(keys);
+               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));
 
        bch2_trans_exit(&trans);
-       bkey_on_stack_exit(&sk, c);
+       bch2_bkey_buf_exit(&sk, c);
 
        return ret;
 }
@@ -429,7 +631,8 @@ int bch2_write_index_default(struct bch_write_op *op)
 
 void bch2_submit_wbio_replicas(struct bch_write_bio *wbio, struct bch_fs *c,
                               enum bch_data_type type,
-                              const struct bkey_i *k)
+                              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;
@@ -445,8 +648,8 @@ void bch2_submit_wbio_replicas(struct bch_write_bio *wbio, struct bch_fs *c,
                ca = bch_dev_bkey_exists(c, ptr->dev);
 
                if (to_entry(ptr + 1) < ptrs.end) {
-                       n = to_wbio(bio_clone_fast(&wbio->bio, GFP_NOIO,
-                                                  &ca->replica_set));
+                       n = to_wbio(bio_alloc_clone(NULL, &wbio->bio,
+                                               GFP_NOFS, &ca->replica_set));
 
                        n->bio.bi_end_io        = wbio->bio.bi_end_io;
                        n->bio.bi_private       = wbio->bio.bi_private;
@@ -463,18 +666,24 @@ void bch2_submit_wbio_replicas(struct bch_write_bio *wbio, struct bch_fs *c,
 
                n->c                    = c;
                n->dev                  = ptr->dev;
-               n->have_ioref           = bch2_dev_get_ioref(ca, WRITE);
+               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;
 
-               if (!journal_flushes_device(ca))
-                       n->bio.bi_opf |= REQ_FUA;
-
                if (likely(n->have_ioref)) {
                        this_cpu_add(ca->io_done->sectors[WRITE][type],
                                     bio_sectors(&n->bio));
 
                        bio_set_dev(&n->bio, ca->disk_sb.bdev);
+
+                       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;
@@ -483,43 +692,33 @@ void bch2_submit_wbio_replicas(struct bch_write_bio *wbio, struct bch_fs *c,
        }
 }
 
-static void __bch2_write(struct closure *);
+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;
 
-       if (!op->error && (op->flags & BCH_WRITE_FLUSH))
-               op->error = bch2_journal_error(&c->journal);
-
-       if (!(op->flags & BCH_WRITE_NOPUT_RESERVATION))
-               bch2_disk_reservation_put(c, &op->res);
-       percpu_ref_put(&c->writes);
-       bch2_keylist_free(&op->insert_keys, op->inline_keys);
+       EBUG_ON(op->open_buckets.nr);
 
        bch2_time_stats_update(&c->times[BCH_TIME_data_write], op->start_time);
+       bch2_disk_reservation_put(c, &op->res);
+
+       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 (op->end_io) {
-               EBUG_ON(cl->parent);
-               closure_debug_destroy(cl);
+       EBUG_ON(cl->parent);
+       closure_debug_destroy(cl);
+       if (op->end_io)
                op->end_io(op);
-       } else {
-               closure_return(cl);
-       }
 }
 
-/**
- * bch_write_index - after a write, update index to point to new data
- */
-static void __bch2_write_index(struct bch_write_op *op)
+static noinline int bch2_write_drop_io_error_ptrs(struct bch_write_op *op)
 {
-       struct bch_fs *c = op->c;
        struct keylist *keys = &op->insert_keys;
        struct bch_extent_ptr *ptr;
-       struct bkey_i *src, *dst = keys->keys, *n, *k;
-       unsigned dev;
-       int ret;
+       struct bkey_i *src, *dst = keys->keys, *n;
 
        for (src = keys->keys; src != keys->top; src = n) {
                n = bkey_next(src);
@@ -528,45 +727,67 @@ static void __bch2_write_index(struct bch_write_op *op)
                        bch2_bkey_drop_ptrs(bkey_i_to_s(src), ptr,
                                            test_bit(ptr->dev, op->failed.d));
 
-                       if (!bch2_bkey_nr_ptrs(bkey_i_to_s_c(src))) {
-                               ret = -EIO;
-                               goto err;
-                       }
+                       if (!bch2_bkey_nr_ptrs(bkey_i_to_s_c(src)))
+                               return -EIO;
                }
 
                if (dst != src)
-                       memmove_u64s_down(dst, src, src->u64s);
+                       memmove_u64s_down(dst, src, src->k.u64s);
                dst = bkey_next(dst);
        }
 
        keys->top = dst;
+       return 0;
+}
+
+/**
+ * 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) {
+       for_each_keylist_key(keys, k)
                bch2_rebalance_add_key(c, bkey_i_to_s_c(k), &op->opts);
 
-               if (bch2_bkey_is_incompressible(bkey_i_to_s_c(k)))
-                       bch2_check_set_feature(op->c, BCH_FEATURE_incompressible);
-
-       }
-
        if (!bch2_keylist_empty(keys)) {
                u64 sectors_start = keylist_sectors(keys);
-               int ret = op->index_update_fn(op);
 
-               BUG_ON(ret == -EINTR);
+               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) {
-                       __bcache_io_error(c, "btree IO error %i", ret);
-                       op->error = ret;
+               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: */
@@ -578,23 +799,90 @@ out:
 err:
        keys->top = keys->keys;
        op->error = ret;
+       op->flags |= BCH_WRITE_DONE;
        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 bch_fs *c = op->c;
+       struct write_point *wp = op->wp;
+       struct workqueue_struct *wq = index_update_wq(op);
+       unsigned long flags;
 
-       __bch2_write_index(op);
+       if ((op->flags & BCH_WRITE_DONE) &&
+           (op->flags & BCH_WRITE_MOVE))
+               bch2_bio_free_pages_pool(op->c, &op->wbio.bio);
 
-       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));
-       } else {
-               continue_at_nobarrier(cl, bch2_write_done, NULL);
+       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);
        }
 }
 
@@ -607,8 +895,17 @@ static void bch2_write_endio(struct bio *bio)
        struct bch_fs *c                = wbio->c;
        struct bch_dev *ca              = bch_dev_bkey_exists(c, wbio->dev);
 
-       if (bch2_dev_io_err_on(bio->bi_status, ca, "data write"))
+       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);
@@ -623,10 +920,8 @@ static void bch2_write_endio(struct bio *bio)
 
        if (parent)
                bio_endio(&parent->bio);
-       else if (!(op->flags & BCH_WRITE_SKIP_CLOSURE_PUT))
-               closure_put(cl);
        else
-               continue_at_nobarrier(cl, bch2_write_index, index_update_wq(op));
+               closure_put(cl);
 }
 
 static void init_append_extent(struct bch_write_op *op,
@@ -634,13 +929,8 @@ static void init_append_extent(struct bch_write_op *op,
                               struct bversion version,
                               struct bch_extent_crc_unpacked crc)
 {
-       struct bch_fs *c = op->c;
        struct bkey_i_extent *e;
-       struct open_bucket *ob;
-       unsigned i;
 
-       BUG_ON(crc.compressed_size > wp->sectors_free);
-       wp->sectors_free -= crc.compressed_size;
        op->pos.offset += crc.uncompressed_size;
 
        e = bkey_extent_init(op->insert_keys.top);
@@ -653,22 +943,8 @@ static void init_append_extent(struct bch_write_op *op,
            crc.nonce)
                bch2_extent_crc_append(&e->k_i, crc);
 
-       open_bucket_for_each(c, &wp->ptrs, ob, i) {
-               struct bch_dev *ca = bch_dev_bkey_exists(c, ob->ptr.dev);
-               union bch_extent_entry *end =
-                       bkey_val_end(bkey_i_to_s(&e->k_i));
-
-               end->ptr = ob->ptr;
-               end->ptr.type = 1 << BCH_EXTENT_ENTRY_ptr;
-               end->ptr.cached = !ca->mi.durability ||
-                       (op->flags & BCH_WRITE_CACHED) != 0;
-               end->ptr.offset += ca->mi.bucket_size - ob->sectors_free;
-
-               e->k.u64s++;
-
-               BUG_ON(crc.compressed_size > ob->sectors_free);
-               ob->sectors_free -= crc.compressed_size;
-       }
+       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);
 }
@@ -688,7 +964,10 @@ static struct bio *bch2_write_bio_alloc(struct bch_fs *c,
                                       ? ((unsigned long) buf & (PAGE_SIZE - 1))
                                       : 0), PAGE_SIZE);
 
-       bio = bio_alloc_bioset(GFP_NOIO, pages, &c->bio_write);
+       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 */
@@ -707,7 +986,7 @@ static struct bio *bch2_write_bio_alloc(struct bch_fs *c,
         */
        bch2_bio_alloc_pages_pool(c, bio,
                                  min_t(unsigned, output_available,
-                                       c->sb.encoded_extent_max << 9));
+                                       c->opts.encoded_extent_max));
 
        if (bio->bi_iter.bi_size < output_available)
                *page_alloc_failed =
@@ -751,6 +1030,7 @@ 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;
@@ -765,10 +1045,10 @@ static int bch2_write_decrypt(struct bch_write_op *op)
        if (bch2_crc_cmp(op->crc.csum, csum))
                return -EIO;
 
-       bch2_encrypt_bio(c, op->crc.csum_type, nonce, &op->wbio.bio);
+       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 0;
+       return ret;
 }
 
 static enum prep_encoded_ret {
@@ -789,11 +1069,12 @@ static enum prep_encoded_ret {
        /* 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 == op->compression_type ||
+           (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))
+                   bch2_write_rechecksum(c, op, op->csum_type) &&
+                   !c->opts.no_data_io)
                        return PREP_ENCODED_CHECKSUM_ERR;
 
                return PREP_ENCODED_DO_WRITE;
@@ -813,7 +1094,7 @@ static enum prep_encoded_ret {
                csum = bch2_checksum_bio(c, op->crc.csum_type,
                                         extent_nonce(op->version, op->crc),
                                         bio);
-               if (bch2_crc_cmp(op->crc.csum, csum))
+               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))
@@ -831,13 +1112,14 @@ static enum prep_encoded_ret {
         */
        if ((op->crc.live_size != op->crc.uncompressed_size ||
             op->crc.csum_type != op->csum_type) &&
-           bch2_write_rechecksum(c, op, 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_type ||
+       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))
@@ -853,7 +1135,6 @@ static int bch2_write_extent(struct bch_write_op *op, struct write_point *wp,
        struct bio *src = &op->wbio.bio, *dst = src;
        struct bvec_iter saved_iter;
        void *ec_buf;
-       struct bpos ec_pos = op->pos;
        unsigned total_output = 0, total_input = 0;
        bool bounce = false;
        bool page_alloc_failed = false;
@@ -870,7 +1151,6 @@ static int bch2_write_extent(struct bch_write_op *op, struct write_point *wp,
                ret = -EIO;
                goto err;
        case PREP_ENCODED_CHECKSUM_ERR:
-               BUG();
                goto csum_err;
        case PREP_ENCODED_DO_WRITE:
                /* XXX look for bug here */
@@ -886,7 +1166,7 @@ static int bch2_write_extent(struct bch_write_op *op, struct write_point *wp,
        }
 
        if (ec_buf ||
-           op->compression_type ||
+           op->compression_opt ||
            (op->csum_type &&
             !(op->flags & BCH_WRITE_PAGES_STABLE)) ||
            (bch2_csum_type_is_encryption(op->csum_type) &&
@@ -900,26 +1180,25 @@ static int bch2_write_extent(struct bch_write_op *op, struct write_point *wp,
        saved_iter = dst->bi_iter;
 
        do {
-               struct bch_extent_crc_unpacked crc =
-                       (struct bch_extent_crc_unpacked) { 0 };
+               struct bch_extent_crc_unpacked crc = { 0 };
                struct bversion version = op->version;
                size_t dst_len, src_len;
 
                if (page_alloc_failed &&
-                   bio_sectors(dst) < wp->sectors_free &&
-                   bio_sectors(dst) < c->sb.encoded_extent_max)
+                   dst->bi_iter.bi_size  < (wp->sectors_free << 9) &&
+                   dst->bi_iter.bi_size < c->opts.encoded_extent_max)
                        break;
 
-               BUG_ON(op->compression_type &&
+               BUG_ON(op->compression_opt &&
                       (op->flags & BCH_WRITE_DATA_ENCODED) &&
                       bch2_csum_type_is_encryption(op->crc.csum_type));
-               BUG_ON(op->compression_type && !bounce);
+               BUG_ON(op->compression_opt && !bounce);
 
                crc.compression_type = op->incompressible
                        ? BCH_COMPRESSION_TYPE_incompressible
-                       : op->compression_type
+                       : op->compression_opt
                        ? bch2_bio_compress(c, dst, &dst_len, src, &src_len,
-                                           op->compression_type)
+                                           op->compression_opt)
                        : 0;
                if (!crc_is_compressed(crc)) {
                        dst_len = min(dst->bi_iter.bi_size, src->bi_iter.bi_size);
@@ -927,7 +1206,7 @@ static int bch2_write_extent(struct bch_write_op *op, struct write_point *wp,
 
                        if (op->csum_type)
                                dst_len = min_t(unsigned, dst_len,
-                                               c->sb.encoded_extent_max << 9);
+                                               c->opts.encoded_extent_max);
 
                        if (bounce) {
                                swap(dst->bi_iter.bi_size, dst_len);
@@ -953,6 +1232,8 @@ static int bch2_write_extent(struct bch_write_op *op, struct write_point *wp,
                    !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
@@ -971,6 +1252,13 @@ static int bch2_write_extent(struct bch_write_op *op, struct write_point *wp,
                                        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,
@@ -985,8 +1273,11 @@ static int bch2_write_extent(struct bch_write_op *op, struct write_point *wp,
                        crc.live_size           = src_len >> 9;
 
                        swap(dst->bi_iter.bi_size, dst_len);
-                       bch2_encrypt_bio(c, op->csum_type,
-                                        extent_nonce(version, crc), dst);
+                       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;
@@ -1016,7 +1307,7 @@ static int bch2_write_extent(struct bch_write_op *op, struct write_point *wp,
                BUG_ON(total_output != total_input);
 
                dst = bio_split(src, total_input >> 9,
-                               GFP_NOIO, &c->bio_write);
+                               GFP_NOFS, &c->bio_write);
                wbio_init(dst)->put_bio = true;
                /* copy WRITE_SYNC flag */
                dst->bi_opf             = src->bi_opf;
@@ -1024,14 +1315,10 @@ static int bch2_write_extent(struct bch_write_op *op, struct write_point *wp,
 
        dst->bi_iter.bi_size = total_output;
 do_write:
-       /* might have done a realloc... */
-       bch2_ec_add_backpointer(c, wp, ec_pos, total_input >> 9);
-
        *_dst = dst;
        return more;
 csum_err:
-       bch_err(c, "error verifying existing checksum while "
-               "rewriting existing data (memory corruption?)");
+       bch_err(c, "error verifying existing checksum while rewriting existing data (memory corruption?)");
        ret = -EIO;
 err:
        if (to_wbio(dst)->bounce)
@@ -1039,17 +1326,337 @@ err:
        if (to_wbio(dst)->put_bio)
                bio_put(dst);
 
-       return 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);
+       }
+
+       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;
+
+       /*
+        * 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:
+        */
+       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);
+}
+
+static void bch2_nocow_write_convert_unwritten(struct bch_write_op *op)
+{
+       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;
+
+       bch2_trans_init(&trans, c, 0, 0);
+retry:
+       bch2_trans_begin(&trans);
+
+       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;
+               }
+
+               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);
+
+               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;
+       }
+
+       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 closure *cl)
+static void __bch2_write(struct bch_write_op *op)
 {
-       struct bch_write_op *op = container_of(cl, struct bch_write_op, cl);
        struct bch_fs *c = op->c;
-       struct write_point *wp;
-       struct bio *bio;
-       bool skip_put = true;
+       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));
 
@@ -1061,93 +1668,103 @@ again:
                /* +1 for possible cache device: */
                if (op->open_buckets.nr + op->nr_replicas + 1 >
                    ARRAY_SIZE(op->open_buckets.v))
-                       goto flush_io;
+                       break;
 
                if (bch2_keylist_realloc(&op->insert_keys,
                                        op->inline_keys,
                                        ARRAY_SIZE(op->inline_keys),
                                        BKEY_EXTENT_U64s_MAX))
-                       goto flush_io;
-
-               wp = bch2_alloc_sectors_start(c,
-                       op->target,
-                       op->opts.erasure_code,
-                       op->write_point,
-                       &op->devs_have,
-                       op->nr_replicas,
-                       op->nr_replicas_required,
-                       op->alloc_reserve,
-                       op->flags,
-                       (op->flags & BCH_WRITE_ALLOC_NOWAIT) ? NULL : cl);
-               EBUG_ON(!wp);
+                       break;
 
-               if (unlikely(IS_ERR(wp))) {
-                       if (unlikely(PTR_ERR(wp) != -EAGAIN)) {
-                               ret = PTR_ERR(wp);
-                               goto err;
-                       }
+               /*
+                * 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 flush_io;
+                       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(c, wp);
 
-               if (ret < 0)
-                       goto err;
+               bch2_alloc_sectors_done_inlined(c, wp);
+err:
+               if (ret <= 0) {
+                       op->flags |= BCH_WRITE_DONE;
 
-               if (ret)
-                       skip_put = false;
+                       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;
 
-               if (!skip_put)
-                       closure_get(bio->bi_private);
-               else
-                       op->flags |= BCH_WRITE_SKIP_CLOSURE_PUT;
+               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);
+               bch2_submit_wbio_replicas(to_wbio(bio), c, BCH_DATA_user,
+                                         key_to_write, false);
        } while (ret);
 
-       if (!skip_put)
-               continue_at(cl, bch2_write_index, index_update_wq(op));
-       return;
-err:
-       op->error = ret;
-
-       continue_at(cl, bch2_write_index, index_update_wq(op));
-       return;
-flush_io:
-       closure_sync(cl);
-
-       if (!bch2_keylist_empty(&op->insert_keys)) {
+       /*
+        * 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->error) {
-                       continue_at_nobarrier(cl, bch2_write_done, NULL);
-                       return;
-               }
+               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);
        }
-
-       goto again;
+out_nofs_restore:
+       memalloc_nofs_restore(nofs_flags);
 }
 
 static void bch2_write_data_inline(struct bch_write_op *op, unsigned data_len)
 {
-       struct closure *cl = &op->cl;
        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,
@@ -1175,9 +1792,7 @@ static void bch2_write_data_inline(struct bch_write_op *op, unsigned data_len)
        set_bkey_val_bytes(&id->k, data_len);
        bch2_keylist_push(&op->insert_keys);
 
-       op->flags |= BCH_WRITE_WROTE_DATA_INLINE;
-       continue_at_nobarrier(cl, bch2_write_index, NULL);
-       return;
+       __bch2_write_index(op);
 err:
        bch2_write_done(&op->cl);
 }
@@ -1205,27 +1820,36 @@ void bch2_write(struct closure *cl)
        struct bch_fs *c = op->c;
        unsigned data_len;
 
+       EBUG_ON(op->cl.parent);
        BUG_ON(!op->nr_replicas);
        BUG_ON(!op->write_point.v);
-       BUG_ON(!bkey_cmp(op->pos, POS_MAX));
+       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_sectors(bio) & (c->opts.block_size - 1)) {
-               __bcache_io_error(c, "misaligned write");
+       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;
+       if (c->opts.nochanges) {
+               op->error = -BCH_ERR_erofs_no_writes;
+               goto err;
+       }
+
+       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,
@@ -1237,32 +1861,54 @@ void bch2_write(struct closure *cl)
                return;
        }
 
-       continue_at_nobarrier(cl, __bch2_write, NULL);
+       __bch2_write(op);
        return;
 err:
-       if (!(op->flags & BCH_WRITE_NOPUT_RESERVATION))
-               bch2_disk_reservation_put(c, &op->res);
+       bch2_disk_reservation_put(c, &op->res);
 
-       if (op->end_io) {
-               EBUG_ON(cl->parent);
-               closure_debug_destroy(cl);
+       closure_debug_destroy(&op->cl);
+       if (op->end_io)
                op->end_io(op);
-       } else {
-               closure_return(cl);
-       }
+}
+
+static const char * const bch2_write_flags[] = {
+#define x(f)   #f,
+       BCH_WRITE_FLAGS()
+#undef x
+       NULL
+};
+
+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);
+
+       prt_str(out, "started: ");
+       bch2_pr_time_units(out, local_clock() - op->start_time);
+       prt_newline(out);
+
+       prt_str(out, "flags: ");
+       prt_bitflags(out, bch2_write_flags, op->flags);
+       prt_newline(out);
+
+       prt_printf(out, "ref: %u", closure_nr_remaining(&op->cl));
+       prt_newline(out);
+
+       printbuf_indent_sub(out, 2);
 }
 
 /* Cache promotion on read */
 
 struct promote_op {
-       struct closure          cl;
        struct rcu_head         rcu;
        u64                     start_time;
 
        struct rhash_head       hash;
        struct bpos             pos;
 
-       struct migrate_write    write;
+       struct data_update      write;
        struct bio_vec          bi_inline_vecs[0]; /* must be last */
 };
 
@@ -1286,6 +1932,9 @@ static inline bool should_promote(struct bch_fs *c, struct bkey_s_c k,
        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;
@@ -1302,33 +1951,31 @@ 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);
-       percpu_ref_put(&c->writes);
+       bch2_write_ref_put(c, BCH_WRITE_REF_promote);
        kfree_rcu(op, rcu);
 }
 
-static void promote_done(struct closure *cl)
+static void promote_done(struct bch_write_op *wop)
 {
        struct promote_op *op =
-               container_of(cl, struct promote_op, cl);
+               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);
-
-       bch2_bio_free_pages_pool(c, &op->write.op.wbio.bio);
        promote_free(c, op);
 }
 
 static void promote_start(struct promote_op *op, struct bch_read_bio *rbio)
 {
-       struct bch_fs *c = rbio->c;
-       struct closure *cl = &op->cl;
        struct bio *bio = &op->write.op.wbio.bio;
 
-       trace_promote(&rbio->bio);
+       trace_and_count(op->write.op.c, read_promote, &rbio->bio);
 
        /* we now own pages: */
        BUG_ON(!rbio->bounce);
@@ -1338,14 +1985,10 @@ static void promote_start(struct promote_op *op, struct bch_read_bio *rbio)
               sizeof(struct bio_vec) * rbio->bio.bi_vcnt);
        swap(bio->bi_vcnt, rbio->bio.bi_vcnt);
 
-       bch2_migrate_read_done(&op->write, rbio);
-
-       closure_init(cl, NULL);
-       closure_call(&op->write.op.cl, bch2_write, c->wq, cl);
-       closure_return_with_destructor(cl, promote_done);
+       bch2_data_update_read_done(&op->write, rbio->pick.crc);
 }
 
-static struct promote_op *__promote_alloc(struct bch_fs *c,
+static struct promote_op *__promote_alloc(struct btree_trans *trans,
                                          enum btree_id btree_id,
                                          struct bkey_s_c k,
                                          struct bpos pos,
@@ -1354,15 +1997,16 @@ static struct promote_op *__promote_alloc(struct bch_fs *c,
                                          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 (!percpu_ref_tryget(&c->writes))
+       if (!bch2_write_ref_tryget(c, BCH_WRITE_REF_promote))
                return NULL;
 
-       op = kzalloc(sizeof(*op) + sizeof(struct bio_vec) * pages, GFP_NOIO);
+       op = kzalloc(sizeof(*op) + sizeof(struct bio_vec) * pages, GFP_NOFS);
        if (!op)
                goto err;
 
@@ -1375,15 +2019,15 @@ static struct promote_op *__promote_alloc(struct bch_fs *c,
         */
        *rbio = kzalloc(sizeof(struct bch_read_bio) +
                        sizeof(struct bio_vec) * pages,
-                       GFP_NOIO);
+                       GFP_NOFS);
        if (!*rbio)
                goto err;
 
        rbio_init(&(*rbio)->bio, opts);
-       bio_init(&(*rbio)->bio, (*rbio)->bio.bi_inline_vecs, pages);
+       bio_init(&(*rbio)->bio, NULL, (*rbio)->bio.bi_inline_vecs, pages, 0);
 
        if (bch2_bio_alloc_pages(&(*rbio)->bio, sectors << 9,
-                                GFP_NOIO))
+                                GFP_NOFS))
                goto err;
 
        (*rbio)->bounce         = true;
@@ -1395,17 +2039,29 @@ static struct promote_op *__promote_alloc(struct bch_fs *c,
                goto err;
 
        bio = &op->write.op.wbio.bio;
-       bio_init(bio, bio->bi_inline_vecs, pages);
+       bio_init(bio, NULL, bio->bi_inline_vecs, pages, 0);
 
-       ret = bch2_migrate_write_init(c, &op->write,
+       ret = bch2_data_update_init(trans, NULL, &op->write,
                        writepoint_hashed((unsigned long) current),
                        opts,
-                       DATA_PROMOTE,
-                       (struct data_opts) {
-                               .target = opts.promote_target
+                       (struct data_update_opts) {
+                               .target         = opts.promote_target,
+                               .extra_replicas = 1,
+                               .write_flags    = BCH_WRITE_ALLOC_NOWAIT|BCH_WRITE_CACHED,
                        },
                        btree_id, k);
-       BUG_ON(ret);
+       /*
+        * 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:
@@ -1414,21 +2070,22 @@ err:
        kfree(*rbio);
        *rbio = NULL;
        kfree(op);
-       percpu_ref_put(&c->writes);
+       bch2_write_ref_put(c, BCH_WRITE_REF_promote);
        return NULL;
 }
 
 noinline
-static struct promote_op *promote_alloc(struct bch_fs *c,
-                                              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)
+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
@@ -1442,10 +2099,10 @@ static struct promote_op *promote_alloc(struct bch_fs *c,
        if (!should_promote(c, k, pos, opts, flags))
                return NULL;
 
-       promote = __promote_alloc(c,
+       promote = __promote_alloc(trans,
                                  k.k->type == KEY_TYPE_reflink_v
-                                 ? BTREE_ID_REFLINK
-                                 : BTREE_ID_EXTENTS,
+                                 ? BTREE_ID_reflink
+                                 : BTREE_ID_extents,
                                  k, pos, pick, opts, sectors, rbio);
        if (!promote)
                return NULL;
@@ -1525,133 +2182,63 @@ static void bch2_rbio_done(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, u64 inode,
+                                    struct bvec_iter bvec_iter,
                                     struct bch_io_failures *failed,
                                     unsigned flags)
 {
        struct btree_trans trans;
-       struct btree_iter *iter;
-       struct bkey_on_stack sk;
+       struct btree_iter iter;
+       struct bkey_buf sk;
        struct bkey_s_c k;
        int ret;
 
        flags &= ~BCH_READ_LAST_FRAGMENT;
        flags |= BCH_READ_MUST_CLONE;
 
-       bkey_on_stack_init(&sk);
+       bch2_bkey_buf_init(&sk);
        bch2_trans_init(&trans, c, 0, 0);
 
-       iter = bch2_trans_get_iter(&trans, BTREE_ID_EXTENTS,
-                                  rbio->pos, BTREE_ITER_SLOTS);
+       bch2_trans_iter_init(&trans, &iter, rbio->data_btree,
+                            rbio->read_pos, BTREE_ITER_SLOTS);
 retry:
        rbio->bio.bi_status = 0;
 
-       k = bch2_btree_iter_peek_slot(iter);
+       k = bch2_btree_iter_peek_slot(&iter);
        if (bkey_err(k))
                goto err;
 
-       bkey_on_stack_reassemble(&sk, c, k);
+       bch2_bkey_buf_reassemble(&sk, c, k);
        k = bkey_i_to_s_c(sk.k);
        bch2_trans_unlock(&trans);
 
        if (!bch2_bkey_matches_ptr(c, k,
                                   rbio->pick.ptr,
-                                  rbio->pos.offset -
+                                  rbio->data_pos.offset -
                                   rbio->pick.crc.offset)) {
                /* extent we wanted to read no longer exists: */
                rbio->hole = true;
                goto out;
        }
 
-       ret = __bch2_read_extent(c, rbio, bvec_iter, k, 0, failed, flags);
+       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);
-       bkey_on_stack_exit(&sk, c);
+       bch2_bkey_buf_exit(&sk, c);
        return;
 err:
        rbio->bio.bi_status = BLK_STS_IOERR;
        goto out;
 }
 
-static void bch2_read_retry(struct bch_fs *c, struct bch_read_bio *rbio,
-                           struct bvec_iter bvec_iter, u64 inode,
-                           struct bch_io_failures *failed, unsigned flags)
-{
-       struct btree_trans trans;
-       struct btree_iter *iter;
-       struct bkey_on_stack sk;
-       struct bkey_s_c k;
-       int ret;
-
-       flags &= ~BCH_READ_LAST_FRAGMENT;
-       flags |= BCH_READ_MUST_CLONE;
-
-       bkey_on_stack_init(&sk);
-       bch2_trans_init(&trans, c, 0, 0);
-retry:
-       bch2_trans_begin(&trans);
-
-       for_each_btree_key(&trans, iter, BTREE_ID_EXTENTS,
-                          POS(inode, bvec_iter.bi_sector),
-                          BTREE_ITER_SLOTS, k, ret) {
-               unsigned bytes, sectors, offset_into_extent;
-
-               bkey_on_stack_reassemble(&sk, c, k);
-               k = bkey_i_to_s_c(sk.k);
-
-               offset_into_extent = iter->pos.offset -
-                       bkey_start_offset(k.k);
-               sectors = k.k->size - offset_into_extent;
-
-               ret = bch2_read_indirect_extent(&trans,
-                                       &offset_into_extent, sk.k);
-               if (ret)
-                       break;
-
-               sectors = min(sectors, k.k->size - offset_into_extent);
-
-               bch2_trans_unlock(&trans);
-
-               bytes = min(sectors, bvec_iter_sectors(bvec_iter)) << 9;
-               swap(bvec_iter.bi_size, bytes);
-
-               ret = __bch2_read_extent(c, rbio, bvec_iter, k,
-                               offset_into_extent, failed, flags);
-               switch (ret) {
-               case READ_RETRY:
-                       goto retry;
-               case READ_ERR:
-                       goto err;
-               };
-
-               if (bytes == bvec_iter.bi_size)
-                       goto out;
-
-               swap(bvec_iter.bi_size, bytes);
-               bio_advance_iter(&rbio->bio, &bvec_iter, bytes);
-       }
-
-       if (ret == -EINTR)
-               goto retry;
-       /*
-        * If we get here, it better have been because there was an error
-        * reading a btree node
-        */
-       BUG_ON(!ret);
-       __bcache_io_error(c, "btree IO error: %i", ret);
-err:
-       rbio->bio.bi_status = BLK_STS_IOERR;
-out:
-       bch2_trans_exit(&trans);
-       bkey_on_stack_exit(&sk, c);
-       bch2_rbio_done(rbio);
-}
-
 static void bch2_rbio_retry(struct work_struct *work)
 {
        struct bch_read_bio *rbio =
@@ -1659,10 +2246,13 @@ static void bch2_rbio_retry(struct work_struct *work)
        struct bch_fs *c        = rbio->c;
        struct bvec_iter iter   = rbio->bvec_iter;
        unsigned flags          = rbio->flags;
-       u64 inode               = rbio->pos.inode;
+       subvol_inum inum = {
+               .subvol = rbio->subvol,
+               .inum   = rbio->read_pos.inode,
+       };
        struct bch_io_failures failed = { .nr = 0 };
 
-       trace_read_retry(&rbio->bio);
+       trace_and_count(c, read_retry, &rbio->bio);
 
        if (rbio->retry == READ_RETRY_AVOID)
                bch2_mark_io_failure(&failed, &rbio->pick);
@@ -1674,10 +2264,14 @@ static void bch2_rbio_retry(struct work_struct *work)
        flags |= BCH_READ_IN_RETRY;
        flags &= ~BCH_READ_MAY_PROMOTE;
 
-       if (flags & BCH_READ_NODECODE)
-               bch2_read_retry_nodecode(c, rbio, iter, inode, &failed, flags);
-       else
-               bch2_read_retry(c, rbio, iter, inode, &failed, flags);
+       if (flags & BCH_READ_NODECODE) {
+               bch2_read_retry_nodecode(c, rbio, iter, &failed, flags);
+       } else {
+               flags &= ~BCH_READ_LAST_FRAGMENT;
+               flags |= BCH_READ_MUST_CLONE;
+
+               __bch2_read(c, rbio, iter, inum, &failed, flags);
+       }
 }
 
 static void bch2_rbio_error(struct bch_read_bio *rbio, int retry,
@@ -1699,34 +2293,25 @@ static void bch2_rbio_error(struct bch_read_bio *rbio, int retry,
        }
 }
 
-static void bch2_rbio_narrow_crcs(struct bch_read_bio *rbio)
+static int __bch2_rbio_narrow_crcs(struct btree_trans *trans,
+                                  struct bch_read_bio *rbio)
 {
        struct bch_fs *c = rbio->c;
-       struct btree_trans trans;
-       struct btree_iter *iter;
-       struct bkey_s_c k;
-       struct bkey_on_stack new;
+       u64 data_offset = rbio->data_pos.offset - rbio->pick.crc.offset;
        struct bch_extent_crc_unpacked new_crc;
-       u64 data_offset = rbio->pos.offset - rbio->pick.crc.offset;
-       int ret;
+       struct btree_iter iter;
+       struct bkey_i *new;
+       struct bkey_s_c k;
+       int ret = 0;
 
        if (crc_is_compressed(rbio->pick.crc))
-               return;
-
-       bkey_on_stack_init(&new);
-       bch2_trans_init(&trans, c, 0, 0);
-retry:
-       bch2_trans_begin(&trans);
+               return 0;
 
-       iter = bch2_trans_get_iter(&trans, BTREE_ID_EXTENTS, rbio->pos,
-                                  BTREE_ITER_SLOTS|BTREE_ITER_INTENT);
-       k = bch2_btree_iter_peek_slot(iter);
-       if (IS_ERR_OR_NULL(k.k))
+       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;
 
-       bkey_on_stack_reassemble(&new, c, k);
-       k = bkey_i_to_s_c(new.k);
-
        if (bversion_cmp(k.k->version, rbio->version) ||
            !bch2_bkey_matches_ptr(c, k, rbio->pick.ptr, data_offset))
                goto out;
@@ -1741,21 +2326,34 @@ retry:
                        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;
        }
 
-       if (!bch2_bkey_narrow_crcs(new.k, new_crc))
+       /*
+        * 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;
 
-       bch2_trans_update(&trans, iter, new.k, 0);
-       ret = bch2_trans_commit(&trans, NULL, NULL,
-                               BTREE_INSERT_NOFAIL|
-                               BTREE_INSERT_NOWAIT);
-       if (ret == -EINTR)
-               goto retry;
+       bkey_reassemble(new, k);
+
+       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_exit(&trans);
-       bkey_on_stack_exit(&new, c);
+       bch2_trans_iter_exit(trans, &iter);
+       return ret;
+}
+
+static noinline void bch2_rbio_narrow_crcs(struct bch_read_bio *rbio)
+{
+       bch2_trans_do(rbio->c, NULL, NULL, BTREE_INSERT_NOFAIL,
+                     __bch2_rbio_narrow_crcs(&trans, rbio));
 }
 
 /* Inner part that may run in process context */
@@ -1770,7 +2368,11 @@ static void __bch2_read_endio(struct work_struct *work)
        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;
+
+       nofs_flags = memalloc_nofs_save();
 
        /* Reset iterator for checksumming and copying bounced data: */
        if (rbio->bounce) {
@@ -1782,9 +2384,16 @@ static void __bch2_read_endio(struct work_struct *work)
        }
 
        csum = bch2_checksum_bio(c, crc.csum_type, nonce, src);
-       if (bch2_crc_cmp(csum, rbio->pick.crc.csum))
+       if (bch2_crc_cmp(csum, rbio->pick.crc.csum) && !c->opts.no_data_io)
                goto csum_err;
 
+       /*
+        * 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);
 
@@ -1796,8 +2405,12 @@ static void __bch2_read_endio(struct work_struct *work)
        crc.live_size   = bvec_iter_sectors(rbio->bvec_iter);
 
        if (crc_is_compressed(crc)) {
-               bch2_encrypt_bio(c, crc.csum_type, nonce, src);
-               if (bch2_bio_uncompress(c, src, dst, dst_iter, crc))
+               ret = bch2_encrypt_bio(c, crc.csum_type, nonce, src);
+               if (ret)
+                       goto decrypt_err;
+
+               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: */
@@ -1807,10 +2420,13 @@ static void __bch2_read_endio(struct work_struct *work)
                BUG_ON(src->bi_iter.bi_size < dst_iter.bi_size);
                src->bi_iter.bi_size = dst_iter.bi_size;
 
-               bch2_encrypt_bio(c, crc.csum_type, nonce, src);
+               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);
                }
        }
@@ -1820,7 +2436,10 @@ static void __bch2_read_endio(struct work_struct *work)
                 * Re encrypt data we decrypted, so it's consistent with
                 * rbio->crc:
                 */
-               bch2_encrypt_bio(c, crc.csum_type, nonce, src);
+               ret = bch2_encrypt_bio(c, crc.csum_type, nonce, src);
+               if (ret)
+                       goto decrypt_err;
+
                promote_start(rbio->promote, rbio);
                rbio->promote = NULL;
        }
@@ -1829,6 +2448,8 @@ nodecode:
                rbio = bch2_rbio_free(rbio);
                bch2_rbio_done(rbio);
        }
+out:
+       memalloc_nofs_restore(nofs_flags);
        return;
 csum_err:
        /*
@@ -1839,22 +2460,30 @@ csum_err:
        if (!rbio->bounce && (rbio->flags & BCH_READ_USER_MAPPED)) {
                rbio->flags |= BCH_READ_MUST_BOUNCE;
                bch2_rbio_error(rbio, READ_RETRY, BLK_STS_IOERR);
-               return;
+               goto out;
        }
 
-       bch2_dev_io_error(ca,
-               "data checksum error, inode %llu offset %llu: expected %0llx:%0llx got %0llx:%0llx (type %u)",
-               rbio->pos.inode, (u64) rbio->bvec_iter.bi_sector,
+       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, crc.csum_type);
+               csum.hi, csum.lo, bch2_csum_types[crc.csum_type]);
+       bch2_io_error(ca);
        bch2_rbio_error(rbio, READ_RETRY_AVOID, BLK_STS_IOERR);
-       return;
+       goto out;
 decompression_err:
-       __bcache_io_error(c, "decompression error, inode %llu offset %llu",
-                         rbio->pos.inode,
-                         (u64) rbio->bvec_iter.bi_sector);
+       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);
-       return;
+       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)
@@ -1874,15 +2503,18 @@ static void bch2_read_endio(struct bio *bio)
        if (!rbio->split)
                rbio->bio.bi_end_io = rbio->end_io;
 
-       if (bch2_dev_io_err_on(bio->bi_status, ca, "data read")) {
+       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->pick.ptr.cached &&
-           (((rbio->flags & BCH_READ_RETRY_IF_STALE) && race_fault()) ||
-            ptr_stale(ca, &rbio->pick.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_error(rbio, READ_RETRY, BLK_STS_AGAIN);
@@ -1892,6 +2524,7 @@ static void bch2_read_endio(struct bio *bio)
        }
 
        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;
@@ -1903,68 +2536,105 @@ static void bch2_read_endio(struct bio *bio)
 
 int __bch2_read_indirect_extent(struct btree_trans *trans,
                                unsigned *offset_into_extent,
-                               struct bkey_i *orig_k)
+                               struct bkey_buf *orig_k)
 {
-       struct btree_iter *iter;
+       struct btree_iter iter;
        struct bkey_s_c k;
        u64 reflink_offset;
        int ret;
 
-       reflink_offset = le64_to_cpu(bkey_i_to_reflink_p(orig_k)->v.idx) +
+       reflink_offset = le64_to_cpu(bkey_i_to_reflink_p(orig_k->k)->v.idx) +
                *offset_into_extent;
 
-       iter = bch2_trans_get_iter(trans, BTREE_ID_REFLINK,
-                                  POS(0, reflink_offset),
-                                  BTREE_ITER_SLOTS);
-       ret = PTR_ERR_OR_ZERO(iter);
-       if (ret)
-               return ret;
-
-       k = bch2_btree_iter_peek_slot(iter);
+       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) {
-               __bcache_io_error(trans->c,
-                               "pointer to nonexistent indirect extent");
+       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;
        }
 
-       *offset_into_extent = iter->pos.offset - bkey_start_offset(k.k);
-       bkey_reassemble(orig_k, k);
+       *offset_into_extent = iter.pos.offset - bkey_start_offset(k.k);
+       bch2_bkey_buf_reassemble(orig_k, trans->c, k);
 err:
-       bch2_trans_iter_put(trans, iter);
+       bch2_trans_iter_exit(trans, &iter);
        return ret;
 }
 
-int __bch2_read_extent(struct bch_fs *c, struct bch_read_bio *orig,
-                      struct bvec_iter iter, struct bkey_s_c k,
+static noinline void read_from_stale_dirty_pointer(struct btree_trans *trans,
+                                                  struct bkey_s_c k,
+                                                  struct bch_extent_ptr ptr)
+{
+       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);
+
+       prt_printf(&buf, "memory gen: %u", *bucket_gen(ca, iter.pos.offset));
+
+       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;
+       struct bch_dev *ca = NULL;
        struct promote_op *promote = NULL;
        bool bounce = false, read_full = false, narrow_crcs = false;
-       struct bpos pos = bkey_start_pos(k.k);
+       struct bpos data_pos = bkey_start_pos(k.k);
        int pick_ret;
 
-       if (k.k->type == KEY_TYPE_inline_data) {
-               struct bkey_s_c_inline_data d = bkey_s_c_to_inline_data(k);
+       if (bkey_extent_is_inline_data(k.k)) {
                unsigned bytes = min_t(unsigned, iter.bi_size,
-                                      bkey_val_bytes(d.k));
+                                      bkey_inline_data_bytes(k.k));
 
                swap(iter.bi_size, bytes);
-               memcpy_to_bio(&orig->bio, iter, d.v->data);
+               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: */
@@ -1972,12 +2642,33 @@ int __bch2_read_extent(struct bch_fs *c, struct bch_read_bio *orig,
                goto hole;
 
        if (pick_ret < 0) {
-               __bcache_io_error(c, "no device to read from");
+               bch_err_inum_offset_ratelimited(c,
+                               read_pos.inode, read_pos.offset << 9,
+                               "no device to read from");
                goto err;
        }
 
-       if (pick_ret > 0)
-               ca = bch_dev_bkey_exists(c, pick.ptr.dev);
+       ca = bch_dev_bkey_exists(c, pick.ptr.dev);
+
+       /*
+        * 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 ((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;
+       }
+
+       /*
+        * Unlock the iterator while the btree node's lock is still in
+        * cache, before doing the IO:
+        */
+       bch2_trans_unlock(trans);
 
        if (flags & BCH_READ_NODECODE) {
                /*
@@ -2004,7 +2695,7 @@ int __bch2_read_extent(struct bch_fs *c, struct bch_read_bio *orig,
        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 &&
+           (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)) ||
@@ -2014,7 +2705,7 @@ int __bch2_read_extent(struct bch_fs *c, struct bch_read_bio *orig,
        }
 
        if (orig->opts.promote_target)
-               promote = promote_alloc(c, iter, k, &pick, orig->opts, flags,
+               promote = promote_alloc(trans, iter, k, &pick, orig->opts, flags,
                                        &rbio, &bounce, &read_full);
 
        if (!read_full) {
@@ -2025,7 +2716,7 @@ int __bch2_read_extent(struct bch_fs *c, struct bch_read_bio *orig,
                         pick.crc.offset ||
                         offset_into_extent));
 
-               pos.offset += offset_into_extent;
+               data_pos.offset += offset_into_extent;
                pick.ptr.offset += pick.crc.offset +
                        offset_into_extent;
                offset_into_extent              = 0;
@@ -2050,8 +2741,10 @@ get_bio:
        } else if (bounce) {
                unsigned sectors = pick.crc.compressed_size;
 
-               rbio = rbio_init(bio_alloc_bioset(GFP_NOIO,
+               rbio = rbio_init(bio_alloc_bioset(NULL,
                                                  DIV_ROUND_UP(sectors, PAGE_SECTORS),
+                                                 0,
+                                                 GFP_NOFS,
                                                  &c->bio_read_split),
                                 orig->opts);
 
@@ -2067,8 +2760,8 @@ get_bio:
                 * from the whole bio, in which case we don't want to retry and
                 * lose the error)
                 */
-               rbio = rbio_init(bio_clone_fast(&orig->bio, GFP_NOIO,
-                                               &c->bio_read_split),
+               rbio = rbio_init(bio_alloc_clone(NULL, &orig->bio, GFP_NOFS,
+                                                &c->bio_read_split),
                                 orig->opts);
                rbio->bio.bi_iter = iter;
                rbio->split     = true;
@@ -2097,7 +2790,10 @@ get_bio:
        /* XXX: only initialize this if needed */
        rbio->devs_have         = bch2_bkey_devs(k);
        rbio->pick              = pick;
-       rbio->pos               = pos;
+       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;
        INIT_WORK(&rbio->work, NULL);
@@ -2107,34 +2803,53 @@ get_bio:
        rbio->bio.bi_end_io     = bch2_read_endio;
 
        if (rbio->bounce)
-               trace_read_bounce(&rbio->bio);
+               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);
 
-       rcu_read_lock();
-       bucket_io_clock_reset(c, ca, PTR_BUCKET_NR(ca, &pick.ptr), READ);
-       rcu_read_unlock();
+       /*
+        * 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_read_split(&orig->bio);
+               trace_and_count(c, read_split, &orig->bio);
        }
 
        if (!rbio->pick.idx) {
                if (!rbio->have_ioref) {
-                       __bcache_io_error(c, "no device to read from");
+                       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],
+               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 (likely(!(flags & BCH_READ_IN_RETRY)))
-                       submit_bio(&rbio->bio);
-               else
-                       submit_bio_wait(&rbio->bio);
+               if (unlikely(c->opts.no_data_io)) {
+                       if (likely(!(flags & BCH_READ_IN_RETRY)))
+                               bio_endio(&rbio->bio);
+               } else {
+                       if (likely(!(flags & BCH_READ_IN_RETRY)))
+                               submit_bio(&rbio->bio);
+                       else
+                               submit_bio_wait(&rbio->bio);
+               }
+
+               /*
+                * 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)) {
@@ -2162,6 +2877,9 @@ out:
                        ret = READ_RETRY;
                }
 
+               if (!ret)
+                       goto out_read_done;
+
                return ret;
        }
 
@@ -2188,54 +2906,64 @@ out_read_done:
        return 0;
 }
 
-void bch2_read(struct bch_fs *c, struct bch_read_bio *rbio, u64 inode)
+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 btree_trans trans;
-       struct btree_iter *iter;
-       struct bkey_on_stack sk;
+       struct btree_iter iter;
+       struct bkey_buf sk;
        struct bkey_s_c k;
-       unsigned flags = BCH_READ_RETRY_IF_STALE|
-               BCH_READ_MAY_PROMOTE|
-               BCH_READ_USER_MAPPED;
+       u32 snapshot;
        int ret;
 
-       BUG_ON(rbio->_state);
        BUG_ON(flags & BCH_READ_NODECODE);
-       BUG_ON(flags & BCH_READ_IN_RETRY);
 
-       rbio->c = c;
-       rbio->start_time = local_clock();
-
-       bkey_on_stack_init(&sk);
+       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;
 
-       iter = bch2_trans_get_iter(&trans, BTREE_ID_EXTENTS,
-                                  POS(inode, rbio->bio.bi_iter.bi_sector),
-                                  BTREE_ITER_SLOTS);
+       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;
 
-               bch2_btree_iter_set_pos(iter,
-                               POS(inode, rbio->bio.bi_iter.bi_sector));
+               /*
+                * read_extent -> io_time_reset may cause a transaction restart
+                * without returning an error, we need to check for that here:
+                */
+               ret = bch2_trans_relock(&trans);
+               if (ret)
+                       break;
 
-               k = bch2_btree_iter_peek_slot(iter);
+               bch2_btree_iter_set_pos(&iter,
+                               POS(inum.inum, bvec_iter.bi_sector));
+
+               k = bch2_btree_iter_peek_slot(&iter);
                ret = bkey_err(k);
                if (ret)
-                       goto err;
+                       break;
 
-               offset_into_extent = iter->pos.offset -
+               offset_into_extent = iter.pos.offset -
                        bkey_start_offset(k.k);
                sectors = k.k->size - offset_into_extent;
 
-               bkey_on_stack_reassemble(&sk, c, k);
-               k = bkey_i_to_s_c(sk.k);
+               bch2_bkey_buf_reassemble(&sk, c, k);
 
-               ret = bch2_read_indirect_extent(&trans,
-                                       &offset_into_extent, sk.k);
+               ret = bch2_read_indirect_extent(&trans, &data_btree,
+                                       &offset_into_extent, &sk);
                if (ret)
-                       goto err;
+                       break;
+
+               k = bkey_i_to_s_c(sk.k);
 
                /*
                 * With indirect extents, the amount of data to read is the min
@@ -2243,37 +2971,46 @@ retry:
                 */
                sectors = min(sectors, k.k->size - offset_into_extent);
 
-               /*
-                * Unlock the iterator while the btree node's lock is still in
-                * cache, before doing the IO:
-                */
-               bch2_trans_unlock(&trans);
-
-               bytes = min(sectors, bio_sectors(&rbio->bio)) << 9;
-               swap(rbio->bio.bi_iter.bi_size, bytes);
+               bytes = min(sectors, bvec_iter_sectors(bvec_iter)) << 9;
+               swap(bvec_iter.bi_size, bytes);
 
-               if (rbio->bio.bi_iter.bi_size == bytes)
+               if (bvec_iter.bi_size == bytes)
                        flags |= BCH_READ_LAST_FRAGMENT;
 
-               bch2_read_extent(c, rbio, k, offset_into_extent, flags);
+               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(rbio->bio.bi_iter.bi_size, bytes);
-               bio_advance(&rbio->bio, bytes);
+               swap(bvec_iter.bi_size, bytes);
+               bio_advance_iter(&rbio->bio, &bvec_iter, bytes);
+
+               ret = btree_trans_too_many_iters(&trans);
+               if (ret)
+                       break;
        }
-out:
-       bch2_trans_exit(&trans);
-       bkey_on_stack_exit(&sk, c);
-       return;
 err:
-       if (ret == -EINTR)
+       bch2_trans_iter_exit(&trans, &iter);
+
+       if (bch2_err_matches(ret, BCH_ERR_transaction_restart) ||
+           ret == READ_RETRY ||
+           ret == READ_RETRY_AVOID)
                goto retry;
 
-       bcache_io_error(c, &rbio->bio, "btree IO error: %i", ret);
-       bch2_rbio_done(rbio);
-       goto out;
+       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_fs_io_exit(struct bch_fs *c)
@@ -2289,18 +3026,26 @@ void bch2_fs_io_exit(struct bch_fs *c)
 int bch2_fs_io_init(struct bch_fs *c)
 {
        if (bioset_init(&c->bio_read, 1, offsetof(struct bch_read_bio, bio),
-                       BIOSET_NEED_BVECS) ||
-           bioset_init(&c->bio_read_split, 1, offsetof(struct bch_read_bio, bio),
-                       BIOSET_NEED_BVECS) ||
-           bioset_init(&c->bio_write, 1, offsetof(struct bch_write_bio, bio),
-                       BIOSET_NEED_BVECS) ||
-           mempool_init_page_pool(&c->bio_bounce_pages,
+                       BIOSET_NEED_BVECS))
+               return -BCH_ERR_ENOMEM_bio_read_init;
+
+       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;
+
+       if (bioset_init(&c->bio_write, 1, offsetof(struct bch_write_bio, bio),
+                       BIOSET_NEED_BVECS))
+               return -BCH_ERR_ENOMEM_bio_write_init;
+
+       if (mempool_init_page_pool(&c->bio_bounce_pages,
                                   max_t(unsigned,
                                         c->opts.btree_node_size,
-                                        c->sb.encoded_extent_max) /
-                                  PAGE_SECTORS, 0) ||
-           rhashtable_init(&c->promote_table, &bch_promote_params))
-               return -ENOMEM;
+                                        c->opts.encoded_extent_max) /
+                                  PAGE_SIZE, 0))
+               return -BCH_ERR_ENOMEM_bio_bounce_pages_init;
+
+       if (rhashtable_init(&c->promote_table, &bch_promote_params))
+               return -BCH_ERR_ENOMEM_promote_table_init;
 
        return 0;
 }