]> git.sesse.net Git - bcachefs-tools-debian/blobdiff - c_src/libbcachefs/btree_io.c
move Rust sources to top level, C sources into c_src
[bcachefs-tools-debian] / c_src / libbcachefs / btree_io.c
diff --git a/c_src/libbcachefs/btree_io.c b/c_src/libbcachefs/btree_io.c
new file mode 100644 (file)
index 0000000..33db48e
--- /dev/null
@@ -0,0 +1,2349 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include "bcachefs.h"
+#include "bkey_methods.h"
+#include "bkey_sort.h"
+#include "btree_cache.h"
+#include "btree_io.h"
+#include "btree_iter.h"
+#include "btree_locking.h"
+#include "btree_update.h"
+#include "btree_update_interior.h"
+#include "buckets.h"
+#include "checksum.h"
+#include "debug.h"
+#include "error.h"
+#include "extents.h"
+#include "io_write.h"
+#include "journal_reclaim.h"
+#include "journal_seq_blacklist.h"
+#include "recovery.h"
+#include "super-io.h"
+#include "trace.h"
+
+#include <linux/sched/mm.h>
+
+void bch2_btree_node_io_unlock(struct btree *b)
+{
+       EBUG_ON(!btree_node_write_in_flight(b));
+
+       clear_btree_node_write_in_flight_inner(b);
+       clear_btree_node_write_in_flight(b);
+       wake_up_bit(&b->flags, BTREE_NODE_write_in_flight);
+}
+
+void bch2_btree_node_io_lock(struct btree *b)
+{
+       bch2_assert_btree_nodes_not_locked();
+
+       wait_on_bit_lock_io(&b->flags, BTREE_NODE_write_in_flight,
+                           TASK_UNINTERRUPTIBLE);
+}
+
+void __bch2_btree_node_wait_on_read(struct btree *b)
+{
+       wait_on_bit_io(&b->flags, BTREE_NODE_read_in_flight,
+                      TASK_UNINTERRUPTIBLE);
+}
+
+void __bch2_btree_node_wait_on_write(struct btree *b)
+{
+       wait_on_bit_io(&b->flags, BTREE_NODE_write_in_flight,
+                      TASK_UNINTERRUPTIBLE);
+}
+
+void bch2_btree_node_wait_on_read(struct btree *b)
+{
+       bch2_assert_btree_nodes_not_locked();
+
+       wait_on_bit_io(&b->flags, BTREE_NODE_read_in_flight,
+                      TASK_UNINTERRUPTIBLE);
+}
+
+void bch2_btree_node_wait_on_write(struct btree *b)
+{
+       bch2_assert_btree_nodes_not_locked();
+
+       wait_on_bit_io(&b->flags, BTREE_NODE_write_in_flight,
+                      TASK_UNINTERRUPTIBLE);
+}
+
+static void verify_no_dups(struct btree *b,
+                          struct bkey_packed *start,
+                          struct bkey_packed *end)
+{
+#ifdef CONFIG_BCACHEFS_DEBUG
+       struct bkey_packed *k, *p;
+
+       if (start == end)
+               return;
+
+       for (p = start, k = bkey_p_next(start);
+            k != end;
+            p = k, k = bkey_p_next(k)) {
+               struct bkey l = bkey_unpack_key(b, p);
+               struct bkey r = bkey_unpack_key(b, k);
+
+               BUG_ON(bpos_ge(l.p, bkey_start_pos(&r)));
+       }
+#endif
+}
+
+static void set_needs_whiteout(struct bset *i, int v)
+{
+       struct bkey_packed *k;
+
+       for (k = i->start; k != vstruct_last(i); k = bkey_p_next(k))
+               k->needs_whiteout = v;
+}
+
+static void btree_bounce_free(struct bch_fs *c, size_t size,
+                             bool used_mempool, void *p)
+{
+       if (used_mempool)
+               mempool_free(p, &c->btree_bounce_pool);
+       else
+               vpfree(p, size);
+}
+
+static void *btree_bounce_alloc(struct bch_fs *c, size_t size,
+                               bool *used_mempool)
+{
+       unsigned flags = memalloc_nofs_save();
+       void *p;
+
+       BUG_ON(size > btree_bytes(c));
+
+       *used_mempool = false;
+       p = vpmalloc(size, __GFP_NOWARN|GFP_NOWAIT);
+       if (!p) {
+               *used_mempool = true;
+               p = mempool_alloc(&c->btree_bounce_pool, GFP_NOFS);
+       }
+       memalloc_nofs_restore(flags);
+       return p;
+}
+
+static void sort_bkey_ptrs(const struct btree *bt,
+                          struct bkey_packed **ptrs, unsigned nr)
+{
+       unsigned n = nr, a = nr / 2, b, c, d;
+
+       if (!a)
+               return;
+
+       /* Heap sort: see lib/sort.c: */
+       while (1) {
+               if (a)
+                       a--;
+               else if (--n)
+                       swap(ptrs[0], ptrs[n]);
+               else
+                       break;
+
+               for (b = a; c = 2 * b + 1, (d = c + 1) < n;)
+                       b = bch2_bkey_cmp_packed(bt,
+                                           ptrs[c],
+                                           ptrs[d]) >= 0 ? c : d;
+               if (d == n)
+                       b = c;
+
+               while (b != a &&
+                      bch2_bkey_cmp_packed(bt,
+                                      ptrs[a],
+                                      ptrs[b]) >= 0)
+                       b = (b - 1) / 2;
+               c = b;
+               while (b != a) {
+                       b = (b - 1) / 2;
+                       swap(ptrs[b], ptrs[c]);
+               }
+       }
+}
+
+static void bch2_sort_whiteouts(struct bch_fs *c, struct btree *b)
+{
+       struct bkey_packed *new_whiteouts, **ptrs, **ptrs_end, *k;
+       bool used_mempool = false;
+       size_t bytes = b->whiteout_u64s * sizeof(u64);
+
+       if (!b->whiteout_u64s)
+               return;
+
+       new_whiteouts = btree_bounce_alloc(c, bytes, &used_mempool);
+
+       ptrs = ptrs_end = ((void *) new_whiteouts + bytes);
+
+       for (k = unwritten_whiteouts_start(c, b);
+            k != unwritten_whiteouts_end(c, b);
+            k = bkey_p_next(k))
+               *--ptrs = k;
+
+       sort_bkey_ptrs(b, ptrs, ptrs_end - ptrs);
+
+       k = new_whiteouts;
+
+       while (ptrs != ptrs_end) {
+               bkey_p_copy(k, *ptrs);
+               k = bkey_p_next(k);
+               ptrs++;
+       }
+
+       verify_no_dups(b, new_whiteouts,
+                      (void *) ((u64 *) new_whiteouts + b->whiteout_u64s));
+
+       memcpy_u64s(unwritten_whiteouts_start(c, b),
+                   new_whiteouts, b->whiteout_u64s);
+
+       btree_bounce_free(c, bytes, used_mempool, new_whiteouts);
+}
+
+static bool should_compact_bset(struct btree *b, struct bset_tree *t,
+                               bool compacting, enum compact_mode mode)
+{
+       if (!bset_dead_u64s(b, t))
+               return false;
+
+       switch (mode) {
+       case COMPACT_LAZY:
+               return should_compact_bset_lazy(b, t) ||
+                       (compacting && !bset_written(b, bset(b, t)));
+       case COMPACT_ALL:
+               return true;
+       default:
+               BUG();
+       }
+}
+
+static bool bch2_drop_whiteouts(struct btree *b, enum compact_mode mode)
+{
+       struct bset_tree *t;
+       bool ret = false;
+
+       for_each_bset(b, t) {
+               struct bset *i = bset(b, t);
+               struct bkey_packed *k, *n, *out, *start, *end;
+               struct btree_node_entry *src = NULL, *dst = NULL;
+
+               if (t != b->set && !bset_written(b, i)) {
+                       src = container_of(i, struct btree_node_entry, keys);
+                       dst = max(write_block(b),
+                                 (void *) btree_bkey_last(b, t - 1));
+               }
+
+               if (src != dst)
+                       ret = true;
+
+               if (!should_compact_bset(b, t, ret, mode)) {
+                       if (src != dst) {
+                               memmove(dst, src, sizeof(*src) +
+                                       le16_to_cpu(src->keys.u64s) *
+                                       sizeof(u64));
+                               i = &dst->keys;
+                               set_btree_bset(b, t, i);
+                       }
+                       continue;
+               }
+
+               start   = btree_bkey_first(b, t);
+               end     = btree_bkey_last(b, t);
+
+               if (src != dst) {
+                       memmove(dst, src, sizeof(*src));
+                       i = &dst->keys;
+                       set_btree_bset(b, t, i);
+               }
+
+               out = i->start;
+
+               for (k = start; k != end; k = n) {
+                       n = bkey_p_next(k);
+
+                       if (!bkey_deleted(k)) {
+                               bkey_p_copy(out, k);
+                               out = bkey_p_next(out);
+                       } else {
+                               BUG_ON(k->needs_whiteout);
+                       }
+               }
+
+               i->u64s = cpu_to_le16((u64 *) out - i->_data);
+               set_btree_bset_end(b, t);
+               bch2_bset_set_no_aux_tree(b, t);
+               ret = true;
+       }
+
+       bch2_verify_btree_nr_keys(b);
+
+       bch2_btree_build_aux_trees(b);
+
+       return ret;
+}
+
+bool bch2_compact_whiteouts(struct bch_fs *c, struct btree *b,
+                           enum compact_mode mode)
+{
+       return bch2_drop_whiteouts(b, mode);
+}
+
+static void btree_node_sort(struct bch_fs *c, struct btree *b,
+                           unsigned start_idx,
+                           unsigned end_idx,
+                           bool filter_whiteouts)
+{
+       struct btree_node *out;
+       struct sort_iter_stack sort_iter;
+       struct bset_tree *t;
+       struct bset *start_bset = bset(b, &b->set[start_idx]);
+       bool used_mempool = false;
+       u64 start_time, seq = 0;
+       unsigned i, u64s = 0, bytes, shift = end_idx - start_idx - 1;
+       bool sorting_entire_node = start_idx == 0 &&
+               end_idx == b->nsets;
+
+       sort_iter_stack_init(&sort_iter, b);
+
+       for (t = b->set + start_idx;
+            t < b->set + end_idx;
+            t++) {
+               u64s += le16_to_cpu(bset(b, t)->u64s);
+               sort_iter_add(&sort_iter.iter,
+                             btree_bkey_first(b, t),
+                             btree_bkey_last(b, t));
+       }
+
+       bytes = sorting_entire_node
+               ? btree_bytes(c)
+               : __vstruct_bytes(struct btree_node, u64s);
+
+       out = btree_bounce_alloc(c, bytes, &used_mempool);
+
+       start_time = local_clock();
+
+       u64s = bch2_sort_keys(out->keys.start, &sort_iter.iter, filter_whiteouts);
+
+       out->keys.u64s = cpu_to_le16(u64s);
+
+       BUG_ON(vstruct_end(&out->keys) > (void *) out + bytes);
+
+       if (sorting_entire_node)
+               bch2_time_stats_update(&c->times[BCH_TIME_btree_node_sort],
+                                      start_time);
+
+       /* Make sure we preserve bset journal_seq: */
+       for (t = b->set + start_idx; t < b->set + end_idx; t++)
+               seq = max(seq, le64_to_cpu(bset(b, t)->journal_seq));
+       start_bset->journal_seq = cpu_to_le64(seq);
+
+       if (sorting_entire_node) {
+               u64s = le16_to_cpu(out->keys.u64s);
+
+               BUG_ON(bytes != btree_bytes(c));
+
+               /*
+                * Our temporary buffer is the same size as the btree node's
+                * buffer, we can just swap buffers instead of doing a big
+                * memcpy()
+                */
+               *out = *b->data;
+               out->keys.u64s = cpu_to_le16(u64s);
+               swap(out, b->data);
+               set_btree_bset(b, b->set, &b->data->keys);
+       } else {
+               start_bset->u64s = out->keys.u64s;
+               memcpy_u64s(start_bset->start,
+                           out->keys.start,
+                           le16_to_cpu(out->keys.u64s));
+       }
+
+       for (i = start_idx + 1; i < end_idx; i++)
+               b->nr.bset_u64s[start_idx] +=
+                       b->nr.bset_u64s[i];
+
+       b->nsets -= shift;
+
+       for (i = start_idx + 1; i < b->nsets; i++) {
+               b->nr.bset_u64s[i]      = b->nr.bset_u64s[i + shift];
+               b->set[i]               = b->set[i + shift];
+       }
+
+       for (i = b->nsets; i < MAX_BSETS; i++)
+               b->nr.bset_u64s[i] = 0;
+
+       set_btree_bset_end(b, &b->set[start_idx]);
+       bch2_bset_set_no_aux_tree(b, &b->set[start_idx]);
+
+       btree_bounce_free(c, bytes, used_mempool, out);
+
+       bch2_verify_btree_nr_keys(b);
+}
+
+void bch2_btree_sort_into(struct bch_fs *c,
+                        struct btree *dst,
+                        struct btree *src)
+{
+       struct btree_nr_keys nr;
+       struct btree_node_iter src_iter;
+       u64 start_time = local_clock();
+
+       BUG_ON(dst->nsets != 1);
+
+       bch2_bset_set_no_aux_tree(dst, dst->set);
+
+       bch2_btree_node_iter_init_from_start(&src_iter, src);
+
+       nr = bch2_sort_repack(btree_bset_first(dst),
+                       src, &src_iter,
+                       &dst->format,
+                       true);
+
+       bch2_time_stats_update(&c->times[BCH_TIME_btree_node_sort],
+                              start_time);
+
+       set_btree_bset_end(dst, dst->set);
+
+       dst->nr.live_u64s       += nr.live_u64s;
+       dst->nr.bset_u64s[0]    += nr.bset_u64s[0];
+       dst->nr.packed_keys     += nr.packed_keys;
+       dst->nr.unpacked_keys   += nr.unpacked_keys;
+
+       bch2_verify_btree_nr_keys(dst);
+}
+
+/*
+ * We're about to add another bset to the btree node, so if there's currently
+ * too many bsets - sort some of them together:
+ */
+static bool btree_node_compact(struct bch_fs *c, struct btree *b)
+{
+       unsigned unwritten_idx;
+       bool ret = false;
+
+       for (unwritten_idx = 0;
+            unwritten_idx < b->nsets;
+            unwritten_idx++)
+               if (!bset_written(b, bset(b, &b->set[unwritten_idx])))
+                       break;
+
+       if (b->nsets - unwritten_idx > 1) {
+               btree_node_sort(c, b, unwritten_idx,
+                               b->nsets, false);
+               ret = true;
+       }
+
+       if (unwritten_idx > 1) {
+               btree_node_sort(c, b, 0, unwritten_idx, false);
+               ret = true;
+       }
+
+       return ret;
+}
+
+void bch2_btree_build_aux_trees(struct btree *b)
+{
+       struct bset_tree *t;
+
+       for_each_bset(b, t)
+               bch2_bset_build_aux_tree(b, t,
+                               !bset_written(b, bset(b, t)) &&
+                               t == bset_tree_last(b));
+}
+
+/*
+ * If we have MAX_BSETS (3) bsets, should we sort them all down to just one?
+ *
+ * The first bset is going to be of similar order to the size of the node, the
+ * last bset is bounded by btree_write_set_buffer(), which is set to keep the
+ * memmove on insert from being too expensive: the middle bset should, ideally,
+ * be the geometric mean of the first and the last.
+ *
+ * Returns true if the middle bset is greater than that geometric mean:
+ */
+static inline bool should_compact_all(struct bch_fs *c, struct btree *b)
+{
+       unsigned mid_u64s_bits =
+               (ilog2(btree_max_u64s(c)) + BTREE_WRITE_SET_U64s_BITS) / 2;
+
+       return bset_u64s(&b->set[1]) > 1U << mid_u64s_bits;
+}
+
+/*
+ * @bch_btree_init_next - initialize a new (unwritten) bset that can then be
+ * inserted into
+ *
+ * Safe to call if there already is an unwritten bset - will only add a new bset
+ * if @b doesn't already have one.
+ *
+ * Returns true if we sorted (i.e. invalidated iterators
+ */
+void bch2_btree_init_next(struct btree_trans *trans, struct btree *b)
+{
+       struct bch_fs *c = trans->c;
+       struct btree_node_entry *bne;
+       bool reinit_iter = false;
+
+       EBUG_ON(!six_lock_counts(&b->c.lock).n[SIX_LOCK_write]);
+       BUG_ON(bset_written(b, bset(b, &b->set[1])));
+       BUG_ON(btree_node_just_written(b));
+
+       if (b->nsets == MAX_BSETS &&
+           !btree_node_write_in_flight(b) &&
+           should_compact_all(c, b)) {
+               bch2_btree_node_write(c, b, SIX_LOCK_write,
+                                     BTREE_WRITE_init_next_bset);
+               reinit_iter = true;
+       }
+
+       if (b->nsets == MAX_BSETS &&
+           btree_node_compact(c, b))
+               reinit_iter = true;
+
+       BUG_ON(b->nsets >= MAX_BSETS);
+
+       bne = want_new_bset(c, b);
+       if (bne)
+               bch2_bset_init_next(c, b, bne);
+
+       bch2_btree_build_aux_trees(b);
+
+       if (reinit_iter)
+               bch2_trans_node_reinit_iter(trans, b);
+}
+
+static void btree_err_msg(struct printbuf *out, struct bch_fs *c,
+                         struct bch_dev *ca,
+                         struct btree *b, struct bset *i,
+                         unsigned offset, int write)
+{
+       prt_printf(out, bch2_log_msg(c, "%s"),
+                  write == READ
+                  ? "error validating btree node "
+                  : "corrupt btree node before write ");
+       if (ca)
+               prt_printf(out, "on %s ", ca->name);
+       prt_printf(out, "at btree ");
+       bch2_btree_pos_to_text(out, c, b);
+
+       prt_printf(out, "\n  node offset %u/%u",
+                  b->written, btree_ptr_sectors_written(&b->key));
+       if (i)
+               prt_printf(out, " bset u64s %u", le16_to_cpu(i->u64s));
+       prt_str(out, ": ");
+}
+
+__printf(9, 10)
+static int __btree_err(int ret,
+                      struct bch_fs *c,
+                      struct bch_dev *ca,
+                      struct btree *b,
+                      struct bset *i,
+                      int write,
+                      bool have_retry,
+                      enum bch_sb_error_id err_type,
+                      const char *fmt, ...)
+{
+       struct printbuf out = PRINTBUF;
+       va_list args;
+
+       btree_err_msg(&out, c, ca, b, i, b->written, write);
+
+       va_start(args, fmt);
+       prt_vprintf(&out, fmt, args);
+       va_end(args);
+
+       if (write == WRITE) {
+               bch2_print_string_as_lines(KERN_ERR, out.buf);
+               ret = c->opts.errors == BCH_ON_ERROR_continue
+                       ? 0
+                       : -BCH_ERR_fsck_errors_not_fixed;
+               goto out;
+       }
+
+       if (!have_retry && ret == -BCH_ERR_btree_node_read_err_want_retry)
+               ret = -BCH_ERR_btree_node_read_err_fixable;
+       if (!have_retry && ret == -BCH_ERR_btree_node_read_err_must_retry)
+               ret = -BCH_ERR_btree_node_read_err_bad_node;
+
+       if (ret != -BCH_ERR_btree_node_read_err_fixable)
+               bch2_sb_error_count(c, err_type);
+
+       switch (ret) {
+       case -BCH_ERR_btree_node_read_err_fixable:
+               ret = bch2_fsck_err(c, FSCK_CAN_FIX, err_type, "%s", out.buf);
+               if (ret != -BCH_ERR_fsck_fix &&
+                   ret != -BCH_ERR_fsck_ignore)
+                       goto fsck_err;
+               ret = -BCH_ERR_fsck_fix;
+               break;
+       case -BCH_ERR_btree_node_read_err_want_retry:
+       case -BCH_ERR_btree_node_read_err_must_retry:
+               bch2_print_string_as_lines(KERN_ERR, out.buf);
+               break;
+       case -BCH_ERR_btree_node_read_err_bad_node:
+               bch2_print_string_as_lines(KERN_ERR, out.buf);
+               bch2_topology_error(c);
+               ret = bch2_run_explicit_recovery_pass(c, BCH_RECOVERY_PASS_check_topology) ?: -EIO;
+               break;
+       case -BCH_ERR_btree_node_read_err_incompatible:
+               bch2_print_string_as_lines(KERN_ERR, out.buf);
+               ret = -BCH_ERR_fsck_errors_not_fixed;
+               break;
+       default:
+               BUG();
+       }
+out:
+fsck_err:
+       printbuf_exit(&out);
+       return ret;
+}
+
+#define btree_err(type, c, ca, b, i, _err_type, msg, ...)              \
+({                                                                     \
+       int _ret = __btree_err(type, c, ca, b, i, write, have_retry,    \
+                              BCH_FSCK_ERR_##_err_type,                \
+                              msg, ##__VA_ARGS__);                     \
+                                                                       \
+       if (_ret != -BCH_ERR_fsck_fix) {                                \
+               ret = _ret;                                             \
+               goto fsck_err;                                          \
+       }                                                               \
+                                                                       \
+       *saw_error = true;                                              \
+})
+
+#define btree_err_on(cond, ...)        ((cond) ? btree_err(__VA_ARGS__) : false)
+
+/*
+ * When btree topology repair changes the start or end of a node, that might
+ * mean we have to drop keys that are no longer inside the node:
+ */
+__cold
+void bch2_btree_node_drop_keys_outside_node(struct btree *b)
+{
+       struct bset_tree *t;
+
+       for_each_bset(b, t) {
+               struct bset *i = bset(b, t);
+               struct bkey_packed *k;
+
+               for (k = i->start; k != vstruct_last(i); k = bkey_p_next(k))
+                       if (bkey_cmp_left_packed(b, k, &b->data->min_key) >= 0)
+                               break;
+
+               if (k != i->start) {
+                       unsigned shift = (u64 *) k - (u64 *) i->start;
+
+                       memmove_u64s_down(i->start, k,
+                                         (u64 *) vstruct_end(i) - (u64 *) k);
+                       i->u64s = cpu_to_le16(le16_to_cpu(i->u64s) - shift);
+                       set_btree_bset_end(b, t);
+               }
+
+               for (k = i->start; k != vstruct_last(i); k = bkey_p_next(k))
+                       if (bkey_cmp_left_packed(b, k, &b->data->max_key) > 0)
+                               break;
+
+               if (k != vstruct_last(i)) {
+                       i->u64s = cpu_to_le16((u64 *) k - (u64 *) i->start);
+                       set_btree_bset_end(b, t);
+               }
+       }
+
+       /*
+        * Always rebuild search trees: eytzinger search tree nodes directly
+        * depend on the values of min/max key:
+        */
+       bch2_bset_set_no_aux_tree(b, b->set);
+       bch2_btree_build_aux_trees(b);
+
+       struct bkey_s_c k;
+       struct bkey unpacked;
+       struct btree_node_iter iter;
+       for_each_btree_node_key_unpack(b, k, &iter, &unpacked) {
+               BUG_ON(bpos_lt(k.k->p, b->data->min_key));
+               BUG_ON(bpos_gt(k.k->p, b->data->max_key));
+       }
+}
+
+static int validate_bset(struct bch_fs *c, struct bch_dev *ca,
+                        struct btree *b, struct bset *i,
+                        unsigned offset, unsigned sectors,
+                        int write, bool have_retry, bool *saw_error)
+{
+       unsigned version = le16_to_cpu(i->version);
+       struct printbuf buf1 = PRINTBUF;
+       struct printbuf buf2 = PRINTBUF;
+       int ret = 0;
+
+       btree_err_on(!bch2_version_compatible(version),
+                    -BCH_ERR_btree_node_read_err_incompatible,
+                    c, ca, b, i,
+                    btree_node_unsupported_version,
+                    "unsupported bset version %u.%u",
+                    BCH_VERSION_MAJOR(version),
+                    BCH_VERSION_MINOR(version));
+
+       if (btree_err_on(version < c->sb.version_min,
+                        -BCH_ERR_btree_node_read_err_fixable,
+                        c, NULL, b, i,
+                        btree_node_bset_older_than_sb_min,
+                        "bset version %u older than superblock version_min %u",
+                        version, c->sb.version_min)) {
+               mutex_lock(&c->sb_lock);
+               c->disk_sb.sb->version_min = cpu_to_le16(version);
+               bch2_write_super(c);
+               mutex_unlock(&c->sb_lock);
+       }
+
+       if (btree_err_on(BCH_VERSION_MAJOR(version) >
+                        BCH_VERSION_MAJOR(c->sb.version),
+                        -BCH_ERR_btree_node_read_err_fixable,
+                        c, NULL, b, i,
+                        btree_node_bset_newer_than_sb,
+                        "bset version %u newer than superblock version %u",
+                        version, c->sb.version)) {
+               mutex_lock(&c->sb_lock);
+               c->disk_sb.sb->version = cpu_to_le16(version);
+               bch2_write_super(c);
+               mutex_unlock(&c->sb_lock);
+       }
+
+       btree_err_on(BSET_SEPARATE_WHITEOUTS(i),
+                    -BCH_ERR_btree_node_read_err_incompatible,
+                    c, ca, b, i,
+                    btree_node_unsupported_version,
+                    "BSET_SEPARATE_WHITEOUTS no longer supported");
+
+       if (btree_err_on(offset + sectors > btree_sectors(c),
+                        -BCH_ERR_btree_node_read_err_fixable,
+                        c, ca, b, i,
+                        bset_past_end_of_btree_node,
+                        "bset past end of btree node")) {
+               i->u64s = 0;
+               ret = 0;
+               goto out;
+       }
+
+       btree_err_on(offset && !i->u64s,
+                    -BCH_ERR_btree_node_read_err_fixable,
+                    c, ca, b, i,
+                    bset_empty,
+                    "empty bset");
+
+       btree_err_on(BSET_OFFSET(i) && BSET_OFFSET(i) != offset,
+                    -BCH_ERR_btree_node_read_err_want_retry,
+                    c, ca, b, i,
+                    bset_wrong_sector_offset,
+                    "bset at wrong sector offset");
+
+       if (!offset) {
+               struct btree_node *bn =
+                       container_of(i, struct btree_node, keys);
+               /* These indicate that we read the wrong btree node: */
+
+               if (b->key.k.type == KEY_TYPE_btree_ptr_v2) {
+                       struct bch_btree_ptr_v2 *bp =
+                               &bkey_i_to_btree_ptr_v2(&b->key)->v;
+
+                       /* XXX endianness */
+                       btree_err_on(bp->seq != bn->keys.seq,
+                                    -BCH_ERR_btree_node_read_err_must_retry,
+                                    c, ca, b, NULL,
+                                    bset_bad_seq,
+                                    "incorrect sequence number (wrong btree node)");
+               }
+
+               btree_err_on(BTREE_NODE_ID(bn) != b->c.btree_id,
+                            -BCH_ERR_btree_node_read_err_must_retry,
+                            c, ca, b, i,
+                            btree_node_bad_btree,
+                            "incorrect btree id");
+
+               btree_err_on(BTREE_NODE_LEVEL(bn) != b->c.level,
+                            -BCH_ERR_btree_node_read_err_must_retry,
+                            c, ca, b, i,
+                            btree_node_bad_level,
+                            "incorrect level");
+
+               if (!write)
+                       compat_btree_node(b->c.level, b->c.btree_id, version,
+                                         BSET_BIG_ENDIAN(i), write, bn);
+
+               if (b->key.k.type == KEY_TYPE_btree_ptr_v2) {
+                       struct bch_btree_ptr_v2 *bp =
+                               &bkey_i_to_btree_ptr_v2(&b->key)->v;
+
+                       if (BTREE_PTR_RANGE_UPDATED(bp)) {
+                               b->data->min_key = bp->min_key;
+                               b->data->max_key = b->key.k.p;
+                       }
+
+                       btree_err_on(!bpos_eq(b->data->min_key, bp->min_key),
+                                    -BCH_ERR_btree_node_read_err_must_retry,
+                                    c, ca, b, NULL,
+                                    btree_node_bad_min_key,
+                                    "incorrect min_key: got %s should be %s",
+                                    (printbuf_reset(&buf1),
+                                     bch2_bpos_to_text(&buf1, bn->min_key), buf1.buf),
+                                    (printbuf_reset(&buf2),
+                                     bch2_bpos_to_text(&buf2, bp->min_key), buf2.buf));
+               }
+
+               btree_err_on(!bpos_eq(bn->max_key, b->key.k.p),
+                            -BCH_ERR_btree_node_read_err_must_retry,
+                            c, ca, b, i,
+                            btree_node_bad_max_key,
+                            "incorrect max key %s",
+                            (printbuf_reset(&buf1),
+                             bch2_bpos_to_text(&buf1, bn->max_key), buf1.buf));
+
+               if (write)
+                       compat_btree_node(b->c.level, b->c.btree_id, version,
+                                         BSET_BIG_ENDIAN(i), write, bn);
+
+               btree_err_on(bch2_bkey_format_invalid(c, &bn->format, write, &buf1),
+                            -BCH_ERR_btree_node_read_err_bad_node,
+                            c, ca, b, i,
+                            btree_node_bad_format,
+                            "invalid bkey format: %s\n  %s", buf1.buf,
+                            (printbuf_reset(&buf2),
+                             bch2_bkey_format_to_text(&buf2, &bn->format), buf2.buf));
+               printbuf_reset(&buf1);
+
+               compat_bformat(b->c.level, b->c.btree_id, version,
+                              BSET_BIG_ENDIAN(i), write,
+                              &bn->format);
+       }
+out:
+fsck_err:
+       printbuf_exit(&buf2);
+       printbuf_exit(&buf1);
+       return ret;
+}
+
+static int bset_key_invalid(struct bch_fs *c, struct btree *b,
+                           struct bkey_s_c k,
+                           bool updated_range, int rw,
+                           struct printbuf *err)
+{
+       return __bch2_bkey_invalid(c, k, btree_node_type(b), READ, err) ?:
+               (!updated_range ? bch2_bkey_in_btree_node(c, b, k, err) : 0) ?:
+               (rw == WRITE ? bch2_bkey_val_invalid(c, k, READ, err) : 0);
+}
+
+static bool __bkey_valid(struct bch_fs *c, struct btree *b,
+                        struct bset *i, struct bkey_packed *k)
+{
+       if (bkey_p_next(k) > vstruct_last(i))
+               return false;
+
+       if (k->format > KEY_FORMAT_CURRENT)
+               return false;
+
+       struct printbuf buf = PRINTBUF;
+       struct bkey tmp;
+       struct bkey_s u = __bkey_disassemble(b, k, &tmp);
+       bool ret = __bch2_bkey_invalid(c, u.s_c, btree_node_type(b), READ, &buf);
+       printbuf_exit(&buf);
+       return ret;
+}
+
+static int validate_bset_keys(struct bch_fs *c, struct btree *b,
+                        struct bset *i, int write,
+                        bool have_retry, bool *saw_error)
+{
+       unsigned version = le16_to_cpu(i->version);
+       struct bkey_packed *k, *prev = NULL;
+       struct printbuf buf = PRINTBUF;
+       bool updated_range = b->key.k.type == KEY_TYPE_btree_ptr_v2 &&
+               BTREE_PTR_RANGE_UPDATED(&bkey_i_to_btree_ptr_v2(&b->key)->v);
+       int ret = 0;
+
+       for (k = i->start;
+            k != vstruct_last(i);) {
+               struct bkey_s u;
+               struct bkey tmp;
+               unsigned next_good_key;
+
+               if (btree_err_on(bkey_p_next(k) > vstruct_last(i),
+                                -BCH_ERR_btree_node_read_err_fixable,
+                                c, NULL, b, i,
+                                btree_node_bkey_past_bset_end,
+                                "key extends past end of bset")) {
+                       i->u64s = cpu_to_le16((u64 *) k - i->_data);
+                       break;
+               }
+
+               if (btree_err_on(k->format > KEY_FORMAT_CURRENT,
+                                -BCH_ERR_btree_node_read_err_fixable,
+                                c, NULL, b, i,
+                                btree_node_bkey_bad_format,
+                                "invalid bkey format %u", k->format))
+                       goto drop_this_key;
+
+               /* XXX: validate k->u64s */
+               if (!write)
+                       bch2_bkey_compat(b->c.level, b->c.btree_id, version,
+                                   BSET_BIG_ENDIAN(i), write,
+                                   &b->format, k);
+
+               u = __bkey_disassemble(b, k, &tmp);
+
+               printbuf_reset(&buf);
+               if (bset_key_invalid(c, b, u.s_c, updated_range, write, &buf)) {
+                       printbuf_reset(&buf);
+                       bset_key_invalid(c, b, u.s_c, updated_range, write, &buf);
+                       prt_printf(&buf, "\n  ");
+                       bch2_bkey_val_to_text(&buf, c, u.s_c);
+
+                       btree_err(-BCH_ERR_btree_node_read_err_fixable,
+                                 c, NULL, b, i,
+                                 btree_node_bad_bkey,
+                                 "invalid bkey: %s", buf.buf);
+                       goto drop_this_key;
+               }
+
+               if (write)
+                       bch2_bkey_compat(b->c.level, b->c.btree_id, version,
+                                   BSET_BIG_ENDIAN(i), write,
+                                   &b->format, k);
+
+               if (prev && bkey_iter_cmp(b, prev, k) > 0) {
+                       struct bkey up = bkey_unpack_key(b, prev);
+
+                       printbuf_reset(&buf);
+                       prt_printf(&buf, "keys out of order: ");
+                       bch2_bkey_to_text(&buf, &up);
+                       prt_printf(&buf, " > ");
+                       bch2_bkey_to_text(&buf, u.k);
+
+                       if (btree_err(-BCH_ERR_btree_node_read_err_fixable,
+                                     c, NULL, b, i,
+                                     btree_node_bkey_out_of_order,
+                                     "%s", buf.buf))
+                               goto drop_this_key;
+               }
+
+               prev = k;
+               k = bkey_p_next(k);
+               continue;
+drop_this_key:
+               next_good_key = k->u64s;
+
+               if (!next_good_key ||
+                   (BSET_BIG_ENDIAN(i) == CPU_BIG_ENDIAN &&
+                    version >= bcachefs_metadata_version_snapshot)) {
+                       /*
+                        * only do scanning if bch2_bkey_compat() has nothing to
+                        * do
+                        */
+
+                       if (!__bkey_valid(c, b, i, (void *) ((u64 *) k + next_good_key))) {
+                               for (next_good_key = 1;
+                                    next_good_key < (u64 *) vstruct_last(i) - (u64 *) k;
+                                    next_good_key++)
+                                       if (__bkey_valid(c, b, i, (void *) ((u64 *) k + next_good_key)))
+                                               goto got_good_key;
+
+                       }
+
+                       /*
+                        * didn't find a good key, have to truncate the rest of
+                        * the bset
+                        */
+                       next_good_key = (u64 *) vstruct_last(i) - (u64 *) k;
+               }
+got_good_key:
+               le16_add_cpu(&i->u64s, -next_good_key);
+               memmove_u64s_down(k, bkey_p_next(k), (u64 *) vstruct_end(i) - (u64 *) k);
+       }
+fsck_err:
+       printbuf_exit(&buf);
+       return ret;
+}
+
+int bch2_btree_node_read_done(struct bch_fs *c, struct bch_dev *ca,
+                             struct btree *b, bool have_retry, bool *saw_error)
+{
+       struct btree_node_entry *bne;
+       struct sort_iter *iter;
+       struct btree_node *sorted;
+       struct bkey_packed *k;
+       struct bset *i;
+       bool used_mempool, blacklisted;
+       bool updated_range = b->key.k.type == KEY_TYPE_btree_ptr_v2 &&
+               BTREE_PTR_RANGE_UPDATED(&bkey_i_to_btree_ptr_v2(&b->key)->v);
+       unsigned u64s;
+       unsigned ptr_written = btree_ptr_sectors_written(&b->key);
+       struct printbuf buf = PRINTBUF;
+       int ret = 0, retry_read = 0, write = READ;
+       u64 start_time = local_clock();
+
+       b->version_ondisk = U16_MAX;
+       /* We might get called multiple times on read retry: */
+       b->written = 0;
+
+       iter = mempool_alloc(&c->fill_iter, GFP_NOFS);
+       sort_iter_init(iter, b, (btree_blocks(c) + 1) * 2);
+
+       if (bch2_meta_read_fault("btree"))
+               btree_err(-BCH_ERR_btree_node_read_err_must_retry,
+                         c, ca, b, NULL,
+                         btree_node_fault_injected,
+                         "dynamic fault");
+
+       btree_err_on(le64_to_cpu(b->data->magic) != bset_magic(c),
+                    -BCH_ERR_btree_node_read_err_must_retry,
+                    c, ca, b, NULL,
+                    btree_node_bad_magic,
+                    "bad magic: want %llx, got %llx",
+                    bset_magic(c), le64_to_cpu(b->data->magic));
+
+       if (b->key.k.type == KEY_TYPE_btree_ptr_v2) {
+               struct bch_btree_ptr_v2 *bp =
+                       &bkey_i_to_btree_ptr_v2(&b->key)->v;
+
+               bch2_bpos_to_text(&buf, b->data->min_key);
+               prt_str(&buf, "-");
+               bch2_bpos_to_text(&buf, b->data->max_key);
+
+               btree_err_on(b->data->keys.seq != bp->seq,
+                            -BCH_ERR_btree_node_read_err_must_retry,
+                            c, ca, b, NULL,
+                            btree_node_bad_seq,
+                            "got wrong btree node (want %llx got %llx)\n"
+                            "got btree %s level %llu pos %s",
+                            bp->seq, b->data->keys.seq,
+                            bch2_btree_id_str(BTREE_NODE_ID(b->data)),
+                            BTREE_NODE_LEVEL(b->data),
+                            buf.buf);
+       } else {
+               btree_err_on(!b->data->keys.seq,
+                            -BCH_ERR_btree_node_read_err_must_retry,
+                            c, ca, b, NULL,
+                            btree_node_bad_seq,
+                            "bad btree header: seq 0");
+       }
+
+       while (b->written < (ptr_written ?: btree_sectors(c))) {
+               unsigned sectors;
+               struct nonce nonce;
+               bool first = !b->written;
+               bool csum_bad;
+
+               if (!b->written) {
+                       i = &b->data->keys;
+
+                       btree_err_on(!bch2_checksum_type_valid(c, BSET_CSUM_TYPE(i)),
+                                    -BCH_ERR_btree_node_read_err_want_retry,
+                                    c, ca, b, i,
+                                    bset_unknown_csum,
+                                    "unknown checksum type %llu", BSET_CSUM_TYPE(i));
+
+                       nonce = btree_nonce(i, b->written << 9);
+
+                       struct bch_csum csum = csum_vstruct(c, BSET_CSUM_TYPE(i), nonce, b->data);
+                       csum_bad = bch2_crc_cmp(b->data->csum, csum);
+                       if (csum_bad)
+                               bch2_io_error(ca, BCH_MEMBER_ERROR_checksum);
+
+                       btree_err_on(csum_bad,
+                                    -BCH_ERR_btree_node_read_err_want_retry,
+                                    c, ca, b, i,
+                                    bset_bad_csum,
+                                    "%s",
+                                    (printbuf_reset(&buf),
+                                     bch2_csum_err_msg(&buf, BSET_CSUM_TYPE(i), b->data->csum, csum),
+                                     buf.buf));
+
+                       ret = bset_encrypt(c, i, b->written << 9);
+                       if (bch2_fs_fatal_err_on(ret, c,
+                                       "error decrypting btree node: %i", ret))
+                               goto fsck_err;
+
+                       btree_err_on(btree_node_type_is_extents(btree_node_type(b)) &&
+                                    !BTREE_NODE_NEW_EXTENT_OVERWRITE(b->data),
+                                    -BCH_ERR_btree_node_read_err_incompatible,
+                                    c, NULL, b, NULL,
+                                    btree_node_unsupported_version,
+                                    "btree node does not have NEW_EXTENT_OVERWRITE set");
+
+                       sectors = vstruct_sectors(b->data, c->block_bits);
+               } else {
+                       bne = write_block(b);
+                       i = &bne->keys;
+
+                       if (i->seq != b->data->keys.seq)
+                               break;
+
+                       btree_err_on(!bch2_checksum_type_valid(c, BSET_CSUM_TYPE(i)),
+                                    -BCH_ERR_btree_node_read_err_want_retry,
+                                    c, ca, b, i,
+                                    bset_unknown_csum,
+                                    "unknown checksum type %llu", BSET_CSUM_TYPE(i));
+
+                       nonce = btree_nonce(i, b->written << 9);
+                       struct bch_csum csum = csum_vstruct(c, BSET_CSUM_TYPE(i), nonce, bne);
+                       csum_bad = bch2_crc_cmp(bne->csum, csum);
+                       if (csum_bad)
+                               bch2_io_error(ca, BCH_MEMBER_ERROR_checksum);
+
+                       btree_err_on(csum_bad,
+                                    -BCH_ERR_btree_node_read_err_want_retry,
+                                    c, ca, b, i,
+                                    bset_bad_csum,
+                                    "%s",
+                                    (printbuf_reset(&buf),
+                                     bch2_csum_err_msg(&buf, BSET_CSUM_TYPE(i), bne->csum, csum),
+                                     buf.buf));
+
+                       ret = bset_encrypt(c, i, b->written << 9);
+                       if (bch2_fs_fatal_err_on(ret, c,
+                                       "error decrypting btree node: %i\n", ret))
+                               goto fsck_err;
+
+                       sectors = vstruct_sectors(bne, c->block_bits);
+               }
+
+               b->version_ondisk = min(b->version_ondisk,
+                                       le16_to_cpu(i->version));
+
+               ret = validate_bset(c, ca, b, i, b->written, sectors,
+                                   READ, have_retry, saw_error);
+               if (ret)
+                       goto fsck_err;
+
+               if (!b->written)
+                       btree_node_set_format(b, b->data->format);
+
+               ret = validate_bset_keys(c, b, i, READ, have_retry, saw_error);
+               if (ret)
+                       goto fsck_err;
+
+               SET_BSET_BIG_ENDIAN(i, CPU_BIG_ENDIAN);
+
+               blacklisted = bch2_journal_seq_is_blacklisted(c,
+                                       le64_to_cpu(i->journal_seq),
+                                       true);
+
+               btree_err_on(blacklisted && first,
+                            -BCH_ERR_btree_node_read_err_fixable,
+                            c, ca, b, i,
+                            bset_blacklisted_journal_seq,
+                            "first btree node bset has blacklisted journal seq (%llu)",
+                            le64_to_cpu(i->journal_seq));
+
+               btree_err_on(blacklisted && ptr_written,
+                            -BCH_ERR_btree_node_read_err_fixable,
+                            c, ca, b, i,
+                            first_bset_blacklisted_journal_seq,
+                            "found blacklisted bset (journal seq %llu) in btree node at offset %u-%u/%u",
+                            le64_to_cpu(i->journal_seq),
+                            b->written, b->written + sectors, ptr_written);
+
+               b->written += sectors;
+
+               if (blacklisted && !first)
+                       continue;
+
+               sort_iter_add(iter,
+                             vstruct_idx(i, 0),
+                             vstruct_last(i));
+       }
+
+       if (ptr_written) {
+               btree_err_on(b->written < ptr_written,
+                            -BCH_ERR_btree_node_read_err_want_retry,
+                            c, ca, b, NULL,
+                            btree_node_data_missing,
+                            "btree node data missing: expected %u sectors, found %u",
+                            ptr_written, b->written);
+       } else {
+               for (bne = write_block(b);
+                    bset_byte_offset(b, bne) < btree_bytes(c);
+                    bne = (void *) bne + block_bytes(c))
+                       btree_err_on(bne->keys.seq == b->data->keys.seq &&
+                                    !bch2_journal_seq_is_blacklisted(c,
+                                                                     le64_to_cpu(bne->keys.journal_seq),
+                                                                     true),
+                                    -BCH_ERR_btree_node_read_err_want_retry,
+                                    c, ca, b, NULL,
+                                    btree_node_bset_after_end,
+                                    "found bset signature after last bset");
+       }
+
+       sorted = btree_bounce_alloc(c, btree_bytes(c), &used_mempool);
+       sorted->keys.u64s = 0;
+
+       set_btree_bset(b, b->set, &b->data->keys);
+
+       b->nr = bch2_key_sort_fix_overlapping(c, &sorted->keys, iter);
+
+       u64s = le16_to_cpu(sorted->keys.u64s);
+       *sorted = *b->data;
+       sorted->keys.u64s = cpu_to_le16(u64s);
+       swap(sorted, b->data);
+       set_btree_bset(b, b->set, &b->data->keys);
+       b->nsets = 1;
+
+       BUG_ON(b->nr.live_u64s != u64s);
+
+       btree_bounce_free(c, btree_bytes(c), used_mempool, sorted);
+
+       if (updated_range)
+               bch2_btree_node_drop_keys_outside_node(b);
+
+       i = &b->data->keys;
+       for (k = i->start; k != vstruct_last(i);) {
+               struct bkey tmp;
+               struct bkey_s u = __bkey_disassemble(b, k, &tmp);
+
+               printbuf_reset(&buf);
+
+               if (bch2_bkey_val_invalid(c, u.s_c, READ, &buf) ||
+                   (bch2_inject_invalid_keys &&
+                    !bversion_cmp(u.k->version, MAX_VERSION))) {
+                       printbuf_reset(&buf);
+
+                       prt_printf(&buf, "invalid bkey: ");
+                       bch2_bkey_val_invalid(c, u.s_c, READ, &buf);
+                       prt_printf(&buf, "\n  ");
+                       bch2_bkey_val_to_text(&buf, c, u.s_c);
+
+                       btree_err(-BCH_ERR_btree_node_read_err_fixable,
+                                 c, NULL, b, i,
+                                 btree_node_bad_bkey,
+                                 "%s", buf.buf);
+
+                       btree_keys_account_key_drop(&b->nr, 0, k);
+
+                       i->u64s = cpu_to_le16(le16_to_cpu(i->u64s) - k->u64s);
+                       memmove_u64s_down(k, bkey_p_next(k),
+                                         (u64 *) vstruct_end(i) - (u64 *) k);
+                       set_btree_bset_end(b, b->set);
+                       continue;
+               }
+
+               if (u.k->type == KEY_TYPE_btree_ptr_v2) {
+                       struct bkey_s_btree_ptr_v2 bp = bkey_s_to_btree_ptr_v2(u);
+
+                       bp.v->mem_ptr = 0;
+               }
+
+               k = bkey_p_next(k);
+       }
+
+       bch2_bset_build_aux_tree(b, b->set, false);
+
+       set_needs_whiteout(btree_bset_first(b), true);
+
+       btree_node_reset_sib_u64s(b);
+
+       bkey_for_each_ptr(bch2_bkey_ptrs(bkey_i_to_s(&b->key)), ptr) {
+               struct bch_dev *ca2 = bch_dev_bkey_exists(c, ptr->dev);
+
+               if (ca2->mi.state != BCH_MEMBER_STATE_rw)
+                       set_btree_node_need_rewrite(b);
+       }
+
+       if (!ptr_written)
+               set_btree_node_need_rewrite(b);
+out:
+       mempool_free(iter, &c->fill_iter);
+       printbuf_exit(&buf);
+       bch2_time_stats_update(&c->times[BCH_TIME_btree_node_read_done], start_time);
+       return retry_read;
+fsck_err:
+       if (ret == -BCH_ERR_btree_node_read_err_want_retry ||
+           ret == -BCH_ERR_btree_node_read_err_must_retry)
+               retry_read = 1;
+       else
+               set_btree_node_read_error(b);
+       goto out;
+}
+
+static void btree_node_read_work(struct work_struct *work)
+{
+       struct btree_read_bio *rb =
+               container_of(work, struct btree_read_bio, work);
+       struct bch_fs *c        = rb->c;
+       struct btree *b         = rb->b;
+       struct bch_dev *ca      = bch_dev_bkey_exists(c, rb->pick.ptr.dev);
+       struct bio *bio         = &rb->bio;
+       struct bch_io_failures failed = { .nr = 0 };
+       struct printbuf buf = PRINTBUF;
+       bool saw_error = false;
+       bool retry = false;
+       bool can_retry;
+
+       goto start;
+       while (1) {
+               retry = true;
+               bch_info(c, "retrying read");
+               ca = bch_dev_bkey_exists(c, rb->pick.ptr.dev);
+               rb->have_ioref          = bch2_dev_get_ioref(ca, READ);
+               bio_reset(bio, NULL, REQ_OP_READ|REQ_SYNC|REQ_META);
+               bio->bi_iter.bi_sector  = rb->pick.ptr.offset;
+               bio->bi_iter.bi_size    = btree_bytes(c);
+
+               if (rb->have_ioref) {
+                       bio_set_dev(bio, ca->disk_sb.bdev);
+                       submit_bio_wait(bio);
+               } else {
+                       bio->bi_status = BLK_STS_REMOVED;
+               }
+start:
+               printbuf_reset(&buf);
+               bch2_btree_pos_to_text(&buf, c, b);
+               bch2_dev_io_err_on(bio->bi_status, ca, BCH_MEMBER_ERROR_read,
+                                  "btree read error %s for %s",
+                                  bch2_blk_status_to_str(bio->bi_status), buf.buf);
+               if (rb->have_ioref)
+                       percpu_ref_put(&ca->io_ref);
+               rb->have_ioref = false;
+
+               bch2_mark_io_failure(&failed, &rb->pick);
+
+               can_retry = bch2_bkey_pick_read_device(c,
+                               bkey_i_to_s_c(&b->key),
+                               &failed, &rb->pick) > 0;
+
+               if (!bio->bi_status &&
+                   !bch2_btree_node_read_done(c, ca, b, can_retry, &saw_error)) {
+                       if (retry)
+                               bch_info(c, "retry success");
+                       break;
+               }
+
+               saw_error = true;
+
+               if (!can_retry) {
+                       set_btree_node_read_error(b);
+                       break;
+               }
+       }
+
+       bch2_time_stats_update(&c->times[BCH_TIME_btree_node_read],
+                              rb->start_time);
+       bio_put(&rb->bio);
+
+       if (saw_error && !btree_node_read_error(b)) {
+               printbuf_reset(&buf);
+               bch2_bpos_to_text(&buf, b->key.k.p);
+               bch_info(c, "%s: rewriting btree node at btree=%s level=%u %s due to error",
+                        __func__, bch2_btree_id_str(b->c.btree_id), b->c.level, buf.buf);
+
+               bch2_btree_node_rewrite_async(c, b);
+       }
+
+       printbuf_exit(&buf);
+       clear_btree_node_read_in_flight(b);
+       wake_up_bit(&b->flags, BTREE_NODE_read_in_flight);
+}
+
+static void btree_node_read_endio(struct bio *bio)
+{
+       struct btree_read_bio *rb =
+               container_of(bio, struct btree_read_bio, bio);
+       struct bch_fs *c        = rb->c;
+
+       if (rb->have_ioref) {
+               struct bch_dev *ca = bch_dev_bkey_exists(c, rb->pick.ptr.dev);
+
+               bch2_latency_acct(ca, rb->start_time, READ);
+       }
+
+       queue_work(c->io_complete_wq, &rb->work);
+}
+
+struct btree_node_read_all {
+       struct closure          cl;
+       struct bch_fs           *c;
+       struct btree            *b;
+       unsigned                nr;
+       void                    *buf[BCH_REPLICAS_MAX];
+       struct bio              *bio[BCH_REPLICAS_MAX];
+       blk_status_t            err[BCH_REPLICAS_MAX];
+};
+
+static unsigned btree_node_sectors_written(struct bch_fs *c, void *data)
+{
+       struct btree_node *bn = data;
+       struct btree_node_entry *bne;
+       unsigned offset = 0;
+
+       if (le64_to_cpu(bn->magic) !=  bset_magic(c))
+               return 0;
+
+       while (offset < btree_sectors(c)) {
+               if (!offset) {
+                       offset += vstruct_sectors(bn, c->block_bits);
+               } else {
+                       bne = data + (offset << 9);
+                       if (bne->keys.seq != bn->keys.seq)
+                               break;
+                       offset += vstruct_sectors(bne, c->block_bits);
+               }
+       }
+
+       return offset;
+}
+
+static bool btree_node_has_extra_bsets(struct bch_fs *c, unsigned offset, void *data)
+{
+       struct btree_node *bn = data;
+       struct btree_node_entry *bne;
+
+       if (!offset)
+               return false;
+
+       while (offset < btree_sectors(c)) {
+               bne = data + (offset << 9);
+               if (bne->keys.seq == bn->keys.seq)
+                       return true;
+               offset++;
+       }
+
+       return false;
+       return offset;
+}
+
+static CLOSURE_CALLBACK(btree_node_read_all_replicas_done)
+{
+       closure_type(ra, struct btree_node_read_all, cl);
+       struct bch_fs *c = ra->c;
+       struct btree *b = ra->b;
+       struct printbuf buf = PRINTBUF;
+       bool dump_bset_maps = false;
+       bool have_retry = false;
+       int ret = 0, best = -1, write = READ;
+       unsigned i, written = 0, written2 = 0;
+       __le64 seq = b->key.k.type == KEY_TYPE_btree_ptr_v2
+               ? bkey_i_to_btree_ptr_v2(&b->key)->v.seq : 0;
+       bool _saw_error = false, *saw_error = &_saw_error;
+
+       for (i = 0; i < ra->nr; i++) {
+               struct btree_node *bn = ra->buf[i];
+
+               if (ra->err[i])
+                       continue;
+
+               if (le64_to_cpu(bn->magic) != bset_magic(c) ||
+                   (seq && seq != bn->keys.seq))
+                       continue;
+
+               if (best < 0) {
+                       best = i;
+                       written = btree_node_sectors_written(c, bn);
+                       continue;
+               }
+
+               written2 = btree_node_sectors_written(c, ra->buf[i]);
+               if (btree_err_on(written2 != written, -BCH_ERR_btree_node_read_err_fixable,
+                                c, NULL, b, NULL,
+                                btree_node_replicas_sectors_written_mismatch,
+                                "btree node sectors written mismatch: %u != %u",
+                                written, written2) ||
+                   btree_err_on(btree_node_has_extra_bsets(c, written2, ra->buf[i]),
+                                -BCH_ERR_btree_node_read_err_fixable,
+                                c, NULL, b, NULL,
+                                btree_node_bset_after_end,
+                                "found bset signature after last bset") ||
+                   btree_err_on(memcmp(ra->buf[best], ra->buf[i], written << 9),
+                                -BCH_ERR_btree_node_read_err_fixable,
+                                c, NULL, b, NULL,
+                                btree_node_replicas_data_mismatch,
+                                "btree node replicas content mismatch"))
+                       dump_bset_maps = true;
+
+               if (written2 > written) {
+                       written = written2;
+                       best = i;
+               }
+       }
+fsck_err:
+       if (dump_bset_maps) {
+               for (i = 0; i < ra->nr; i++) {
+                       struct btree_node *bn = ra->buf[i];
+                       struct btree_node_entry *bne = NULL;
+                       unsigned offset = 0, sectors;
+                       bool gap = false;
+
+                       if (ra->err[i])
+                               continue;
+
+                       printbuf_reset(&buf);
+
+                       while (offset < btree_sectors(c)) {
+                               if (!offset) {
+                                       sectors = vstruct_sectors(bn, c->block_bits);
+                               } else {
+                                       bne = ra->buf[i] + (offset << 9);
+                                       if (bne->keys.seq != bn->keys.seq)
+                                               break;
+                                       sectors = vstruct_sectors(bne, c->block_bits);
+                               }
+
+                               prt_printf(&buf, " %u-%u", offset, offset + sectors);
+                               if (bne && bch2_journal_seq_is_blacklisted(c,
+                                                       le64_to_cpu(bne->keys.journal_seq), false))
+                                       prt_printf(&buf, "*");
+                               offset += sectors;
+                       }
+
+                       while (offset < btree_sectors(c)) {
+                               bne = ra->buf[i] + (offset << 9);
+                               if (bne->keys.seq == bn->keys.seq) {
+                                       if (!gap)
+                                               prt_printf(&buf, " GAP");
+                                       gap = true;
+
+                                       sectors = vstruct_sectors(bne, c->block_bits);
+                                       prt_printf(&buf, " %u-%u", offset, offset + sectors);
+                                       if (bch2_journal_seq_is_blacklisted(c,
+                                                       le64_to_cpu(bne->keys.journal_seq), false))
+                                               prt_printf(&buf, "*");
+                               }
+                               offset++;
+                       }
+
+                       bch_err(c, "replica %u:%s", i, buf.buf);
+               }
+       }
+
+       if (best >= 0) {
+               memcpy(b->data, ra->buf[best], btree_bytes(c));
+               ret = bch2_btree_node_read_done(c, NULL, b, false, saw_error);
+       } else {
+               ret = -1;
+       }
+
+       if (ret)
+               set_btree_node_read_error(b);
+       else if (*saw_error)
+               bch2_btree_node_rewrite_async(c, b);
+
+       for (i = 0; i < ra->nr; i++) {
+               mempool_free(ra->buf[i], &c->btree_bounce_pool);
+               bio_put(ra->bio[i]);
+       }
+
+       closure_debug_destroy(&ra->cl);
+       kfree(ra);
+       printbuf_exit(&buf);
+
+       clear_btree_node_read_in_flight(b);
+       wake_up_bit(&b->flags, BTREE_NODE_read_in_flight);
+}
+
+static void btree_node_read_all_replicas_endio(struct bio *bio)
+{
+       struct btree_read_bio *rb =
+               container_of(bio, struct btree_read_bio, bio);
+       struct bch_fs *c        = rb->c;
+       struct btree_node_read_all *ra = rb->ra;
+
+       if (rb->have_ioref) {
+               struct bch_dev *ca = bch_dev_bkey_exists(c, rb->pick.ptr.dev);
+
+               bch2_latency_acct(ca, rb->start_time, READ);
+       }
+
+       ra->err[rb->idx] = bio->bi_status;
+       closure_put(&ra->cl);
+}
+
+/*
+ * XXX This allocates multiple times from the same mempools, and can deadlock
+ * under sufficient memory pressure (but is only a debug path)
+ */
+static int btree_node_read_all_replicas(struct bch_fs *c, struct btree *b, bool sync)
+{
+       struct bkey_s_c k = bkey_i_to_s_c(&b->key);
+       struct bkey_ptrs_c ptrs = bch2_bkey_ptrs_c(k);
+       const union bch_extent_entry *entry;
+       struct extent_ptr_decoded pick;
+       struct btree_node_read_all *ra;
+       unsigned i;
+
+       ra = kzalloc(sizeof(*ra), GFP_NOFS);
+       if (!ra)
+               return -BCH_ERR_ENOMEM_btree_node_read_all_replicas;
+
+       closure_init(&ra->cl, NULL);
+       ra->c   = c;
+       ra->b   = b;
+       ra->nr  = bch2_bkey_nr_ptrs(k);
+
+       for (i = 0; i < ra->nr; i++) {
+               ra->buf[i] = mempool_alloc(&c->btree_bounce_pool, GFP_NOFS);
+               ra->bio[i] = bio_alloc_bioset(NULL,
+                                             buf_pages(ra->buf[i], btree_bytes(c)),
+                                             REQ_OP_READ|REQ_SYNC|REQ_META,
+                                             GFP_NOFS,
+                                             &c->btree_bio);
+       }
+
+       i = 0;
+       bkey_for_each_ptr_decode(k.k, ptrs, pick, entry) {
+               struct bch_dev *ca = bch_dev_bkey_exists(c, pick.ptr.dev);
+               struct btree_read_bio *rb =
+                       container_of(ra->bio[i], struct btree_read_bio, bio);
+               rb->c                   = c;
+               rb->b                   = b;
+               rb->ra                  = ra;
+               rb->start_time          = local_clock();
+               rb->have_ioref          = bch2_dev_get_ioref(ca, READ);
+               rb->idx                 = i;
+               rb->pick                = pick;
+               rb->bio.bi_iter.bi_sector = pick.ptr.offset;
+               rb->bio.bi_end_io       = btree_node_read_all_replicas_endio;
+               bch2_bio_map(&rb->bio, ra->buf[i], btree_bytes(c));
+
+               if (rb->have_ioref) {
+                       this_cpu_add(ca->io_done->sectors[READ][BCH_DATA_btree],
+                                    bio_sectors(&rb->bio));
+                       bio_set_dev(&rb->bio, ca->disk_sb.bdev);
+
+                       closure_get(&ra->cl);
+                       submit_bio(&rb->bio);
+               } else {
+                       ra->err[i] = BLK_STS_REMOVED;
+               }
+
+               i++;
+       }
+
+       if (sync) {
+               closure_sync(&ra->cl);
+               btree_node_read_all_replicas_done(&ra->cl.work);
+       } else {
+               continue_at(&ra->cl, btree_node_read_all_replicas_done,
+                           c->io_complete_wq);
+       }
+
+       return 0;
+}
+
+void bch2_btree_node_read(struct btree_trans *trans, struct btree *b,
+                         bool sync)
+{
+       struct bch_fs *c = trans->c;
+       struct extent_ptr_decoded pick;
+       struct btree_read_bio *rb;
+       struct bch_dev *ca;
+       struct bio *bio;
+       int ret;
+
+       trace_and_count(c, btree_node_read, trans, b);
+
+       if (bch2_verify_all_btree_replicas &&
+           !btree_node_read_all_replicas(c, b, sync))
+               return;
+
+       ret = bch2_bkey_pick_read_device(c, bkey_i_to_s_c(&b->key),
+                                        NULL, &pick);
+
+       if (ret <= 0) {
+               struct printbuf buf = PRINTBUF;
+
+               prt_str(&buf, "btree node read error: no device to read from\n at ");
+               bch2_btree_pos_to_text(&buf, c, b);
+               bch_err(c, "%s", buf.buf);
+
+               if (c->recovery_passes_explicit & BIT_ULL(BCH_RECOVERY_PASS_check_topology) &&
+                   c->curr_recovery_pass > BCH_RECOVERY_PASS_check_topology)
+                       bch2_fatal_error(c);
+
+               set_btree_node_read_error(b);
+               clear_btree_node_read_in_flight(b);
+               wake_up_bit(&b->flags, BTREE_NODE_read_in_flight);
+               printbuf_exit(&buf);
+               return;
+       }
+
+       ca = bch_dev_bkey_exists(c, pick.ptr.dev);
+
+       bio = bio_alloc_bioset(NULL,
+                              buf_pages(b->data, btree_bytes(c)),
+                              REQ_OP_READ|REQ_SYNC|REQ_META,
+                              GFP_NOFS,
+                              &c->btree_bio);
+       rb = container_of(bio, struct btree_read_bio, bio);
+       rb->c                   = c;
+       rb->b                   = b;
+       rb->ra                  = NULL;
+       rb->start_time          = local_clock();
+       rb->have_ioref          = bch2_dev_get_ioref(ca, READ);
+       rb->pick                = pick;
+       INIT_WORK(&rb->work, btree_node_read_work);
+       bio->bi_iter.bi_sector  = pick.ptr.offset;
+       bio->bi_end_io          = btree_node_read_endio;
+       bch2_bio_map(bio, b->data, btree_bytes(c));
+
+       if (rb->have_ioref) {
+               this_cpu_add(ca->io_done->sectors[READ][BCH_DATA_btree],
+                            bio_sectors(bio));
+               bio_set_dev(bio, ca->disk_sb.bdev);
+
+               if (sync) {
+                       submit_bio_wait(bio);
+                       bch2_latency_acct(ca, rb->start_time, READ);
+                       btree_node_read_work(&rb->work);
+               } else {
+                       submit_bio(bio);
+               }
+       } else {
+               bio->bi_status = BLK_STS_REMOVED;
+
+               if (sync)
+                       btree_node_read_work(&rb->work);
+               else
+                       queue_work(c->io_complete_wq, &rb->work);
+       }
+}
+
+static int __bch2_btree_root_read(struct btree_trans *trans, enum btree_id id,
+                                 const struct bkey_i *k, unsigned level)
+{
+       struct bch_fs *c = trans->c;
+       struct closure cl;
+       struct btree *b;
+       int ret;
+
+       closure_init_stack(&cl);
+
+       do {
+               ret = bch2_btree_cache_cannibalize_lock(trans, &cl);
+               closure_sync(&cl);
+       } while (ret);
+
+       b = bch2_btree_node_mem_alloc(trans, level != 0);
+       bch2_btree_cache_cannibalize_unlock(trans);
+
+       BUG_ON(IS_ERR(b));
+
+       bkey_copy(&b->key, k);
+       BUG_ON(bch2_btree_node_hash_insert(&c->btree_cache, b, level, id));
+
+       set_btree_node_read_in_flight(b);
+
+       bch2_btree_node_read(trans, b, true);
+
+       if (btree_node_read_error(b)) {
+               bch2_btree_node_hash_remove(&c->btree_cache, b);
+
+               mutex_lock(&c->btree_cache.lock);
+               list_move(&b->list, &c->btree_cache.freeable);
+               mutex_unlock(&c->btree_cache.lock);
+
+               ret = -EIO;
+               goto err;
+       }
+
+       bch2_btree_set_root_for_read(c, b);
+err:
+       six_unlock_write(&b->c.lock);
+       six_unlock_intent(&b->c.lock);
+
+       return ret;
+}
+
+int bch2_btree_root_read(struct bch_fs *c, enum btree_id id,
+                       const struct bkey_i *k, unsigned level)
+{
+       return bch2_trans_run(c, __bch2_btree_root_read(trans, id, k, level));
+}
+
+static void bch2_btree_complete_write(struct bch_fs *c, struct btree *b,
+                                     struct btree_write *w)
+{
+       unsigned long old, new, v = READ_ONCE(b->will_make_reachable);
+
+       do {
+               old = new = v;
+               if (!(old & 1))
+                       break;
+
+               new &= ~1UL;
+       } while ((v = cmpxchg(&b->will_make_reachable, old, new)) != old);
+
+       if (old & 1)
+               closure_put(&((struct btree_update *) new)->cl);
+
+       bch2_journal_pin_drop(&c->journal, &w->journal);
+}
+
+static void __btree_node_write_done(struct bch_fs *c, struct btree *b)
+{
+       struct btree_write *w = btree_prev_write(b);
+       unsigned long old, new, v;
+       unsigned type = 0;
+
+       bch2_btree_complete_write(c, b, w);
+
+       v = READ_ONCE(b->flags);
+       do {
+               old = new = v;
+
+               if ((old & (1U << BTREE_NODE_dirty)) &&
+                   (old & (1U << BTREE_NODE_need_write)) &&
+                   !(old & (1U << BTREE_NODE_never_write)) &&
+                   !(old & (1U << BTREE_NODE_write_blocked)) &&
+                   !(old & (1U << BTREE_NODE_will_make_reachable))) {
+                       new &= ~(1U << BTREE_NODE_dirty);
+                       new &= ~(1U << BTREE_NODE_need_write);
+                       new |=  (1U << BTREE_NODE_write_in_flight);
+                       new |=  (1U << BTREE_NODE_write_in_flight_inner);
+                       new |=  (1U << BTREE_NODE_just_written);
+                       new ^=  (1U << BTREE_NODE_write_idx);
+
+                       type = new & BTREE_WRITE_TYPE_MASK;
+                       new &= ~BTREE_WRITE_TYPE_MASK;
+               } else {
+                       new &= ~(1U << BTREE_NODE_write_in_flight);
+                       new &= ~(1U << BTREE_NODE_write_in_flight_inner);
+               }
+       } while ((v = cmpxchg(&b->flags, old, new)) != old);
+
+       if (new & (1U << BTREE_NODE_write_in_flight))
+               __bch2_btree_node_write(c, b, BTREE_WRITE_ALREADY_STARTED|type);
+       else
+               wake_up_bit(&b->flags, BTREE_NODE_write_in_flight);
+}
+
+static void btree_node_write_done(struct bch_fs *c, struct btree *b)
+{
+       struct btree_trans *trans = bch2_trans_get(c);
+
+       btree_node_lock_nopath_nofail(trans, &b->c, SIX_LOCK_read);
+       __btree_node_write_done(c, b);
+       six_unlock_read(&b->c.lock);
+
+       bch2_trans_put(trans);
+}
+
+static void btree_node_write_work(struct work_struct *work)
+{
+       struct btree_write_bio *wbio =
+               container_of(work, struct btree_write_bio, work);
+       struct bch_fs *c        = wbio->wbio.c;
+       struct btree *b         = wbio->wbio.bio.bi_private;
+       struct bch_extent_ptr *ptr;
+       int ret = 0;
+
+       btree_bounce_free(c,
+               wbio->data_bytes,
+               wbio->wbio.used_mempool,
+               wbio->data);
+
+       bch2_bkey_drop_ptrs(bkey_i_to_s(&wbio->key), ptr,
+               bch2_dev_list_has_dev(wbio->wbio.failed, ptr->dev));
+
+       if (!bch2_bkey_nr_ptrs(bkey_i_to_s_c(&wbio->key))) {
+               ret = -BCH_ERR_btree_write_all_failed;
+               goto err;
+       }
+
+       if (wbio->wbio.first_btree_write) {
+               if (wbio->wbio.failed.nr) {
+
+               }
+       } else {
+               ret = bch2_trans_do(c, NULL, NULL, 0,
+                       bch2_btree_node_update_key_get_iter(trans, b, &wbio->key,
+                                       BCH_WATERMARK_reclaim|
+                                       BCH_TRANS_COMMIT_journal_reclaim|
+                                       BCH_TRANS_COMMIT_no_enospc|
+                                       BCH_TRANS_COMMIT_no_check_rw,
+                                       !wbio->wbio.failed.nr));
+               if (ret)
+                       goto err;
+       }
+out:
+       bio_put(&wbio->wbio.bio);
+       btree_node_write_done(c, b);
+       return;
+err:
+       set_btree_node_noevict(b);
+       if (!bch2_err_matches(ret, EROFS))
+               bch2_fs_fatal_error(c, "fatal error writing btree node: %s", bch2_err_str(ret));
+       goto out;
+}
+
+static void btree_node_write_endio(struct bio *bio)
+{
+       struct bch_write_bio *wbio      = to_wbio(bio);
+       struct bch_write_bio *parent    = wbio->split ? wbio->parent : NULL;
+       struct bch_write_bio *orig      = parent ?: wbio;
+       struct btree_write_bio *wb      = container_of(orig, struct btree_write_bio, wbio);
+       struct bch_fs *c                = wbio->c;
+       struct btree *b                 = wbio->bio.bi_private;
+       struct bch_dev *ca              = bch_dev_bkey_exists(c, wbio->dev);
+       unsigned long flags;
+
+       if (wbio->have_ioref)
+               bch2_latency_acct(ca, wbio->submit_time, WRITE);
+
+       if (bch2_dev_io_err_on(bio->bi_status, ca, BCH_MEMBER_ERROR_write,
+                              "btree write error: %s",
+                              bch2_blk_status_to_str(bio->bi_status)) ||
+           bch2_meta_write_fault("btree")) {
+               spin_lock_irqsave(&c->btree_write_error_lock, flags);
+               bch2_dev_list_add_dev(&orig->failed, wbio->dev);
+               spin_unlock_irqrestore(&c->btree_write_error_lock, flags);
+       }
+
+       if (wbio->have_ioref)
+               percpu_ref_put(&ca->io_ref);
+
+       if (parent) {
+               bio_put(bio);
+               bio_endio(&parent->bio);
+               return;
+       }
+
+       clear_btree_node_write_in_flight_inner(b);
+       wake_up_bit(&b->flags, BTREE_NODE_write_in_flight_inner);
+       INIT_WORK(&wb->work, btree_node_write_work);
+       queue_work(c->btree_io_complete_wq, &wb->work);
+}
+
+static int validate_bset_for_write(struct bch_fs *c, struct btree *b,
+                                  struct bset *i, unsigned sectors)
+{
+       struct printbuf buf = PRINTBUF;
+       bool saw_error;
+       int ret;
+
+       ret = bch2_bkey_invalid(c, bkey_i_to_s_c(&b->key),
+                               BKEY_TYPE_btree, WRITE, &buf);
+
+       if (ret)
+               bch2_fs_inconsistent(c, "invalid btree node key before write: %s", buf.buf);
+       printbuf_exit(&buf);
+       if (ret)
+               return ret;
+
+       ret = validate_bset_keys(c, b, i, WRITE, false, &saw_error) ?:
+               validate_bset(c, NULL, b, i, b->written, sectors, WRITE, false, &saw_error);
+       if (ret) {
+               bch2_inconsistent_error(c);
+               dump_stack();
+       }
+
+       return ret;
+}
+
+static void btree_write_submit(struct work_struct *work)
+{
+       struct btree_write_bio *wbio = container_of(work, struct btree_write_bio, work);
+       BKEY_PADDED_ONSTACK(k, BKEY_BTREE_PTR_VAL_U64s_MAX) tmp;
+
+       bkey_copy(&tmp.k, &wbio->key);
+
+       bkey_for_each_ptr(bch2_bkey_ptrs(bkey_i_to_s(&tmp.k)), ptr)
+               ptr->offset += wbio->sector_offset;
+
+       bch2_submit_wbio_replicas(&wbio->wbio, wbio->wbio.c, BCH_DATA_btree,
+                                 &tmp.k, false);
+}
+
+void __bch2_btree_node_write(struct bch_fs *c, struct btree *b, unsigned flags)
+{
+       struct btree_write_bio *wbio;
+       struct bset_tree *t;
+       struct bset *i;
+       struct btree_node *bn = NULL;
+       struct btree_node_entry *bne = NULL;
+       struct sort_iter_stack sort_iter;
+       struct nonce nonce;
+       unsigned bytes_to_write, sectors_to_write, bytes, u64s;
+       u64 seq = 0;
+       bool used_mempool;
+       unsigned long old, new;
+       bool validate_before_checksum = false;
+       enum btree_write_type type = flags & BTREE_WRITE_TYPE_MASK;
+       void *data;
+       int ret;
+
+       if (flags & BTREE_WRITE_ALREADY_STARTED)
+               goto do_write;
+
+       /*
+        * We may only have a read lock on the btree node - the dirty bit is our
+        * "lock" against racing with other threads that may be trying to start
+        * a write, we do a write iff we clear the dirty bit. Since setting the
+        * dirty bit requires a write lock, we can't race with other threads
+        * redirtying it:
+        */
+       do {
+               old = new = READ_ONCE(b->flags);
+
+               if (!(old & (1 << BTREE_NODE_dirty)))
+                       return;
+
+               if ((flags & BTREE_WRITE_ONLY_IF_NEED) &&
+                   !(old & (1 << BTREE_NODE_need_write)))
+                       return;
+
+               if (old &
+                   ((1 << BTREE_NODE_never_write)|
+                    (1 << BTREE_NODE_write_blocked)))
+                       return;
+
+               if (b->written &&
+                   (old & (1 << BTREE_NODE_will_make_reachable)))
+                       return;
+
+               if (old & (1 << BTREE_NODE_write_in_flight))
+                       return;
+
+               if (flags & BTREE_WRITE_ONLY_IF_NEED)
+                       type = new & BTREE_WRITE_TYPE_MASK;
+               new &= ~BTREE_WRITE_TYPE_MASK;
+
+               new &= ~(1 << BTREE_NODE_dirty);
+               new &= ~(1 << BTREE_NODE_need_write);
+               new |=  (1 << BTREE_NODE_write_in_flight);
+               new |=  (1 << BTREE_NODE_write_in_flight_inner);
+               new |=  (1 << BTREE_NODE_just_written);
+               new ^=  (1 << BTREE_NODE_write_idx);
+       } while (cmpxchg_acquire(&b->flags, old, new) != old);
+
+       if (new & (1U << BTREE_NODE_need_write))
+               return;
+do_write:
+       BUG_ON((type == BTREE_WRITE_initial) != (b->written == 0));
+
+       atomic_dec(&c->btree_cache.dirty);
+
+       BUG_ON(btree_node_fake(b));
+       BUG_ON((b->will_make_reachable != 0) != !b->written);
+
+       BUG_ON(b->written >= btree_sectors(c));
+       BUG_ON(b->written & (block_sectors(c) - 1));
+       BUG_ON(bset_written(b, btree_bset_last(b)));
+       BUG_ON(le64_to_cpu(b->data->magic) != bset_magic(c));
+       BUG_ON(memcmp(&b->data->format, &b->format, sizeof(b->format)));
+
+       bch2_sort_whiteouts(c, b);
+
+       sort_iter_stack_init(&sort_iter, b);
+
+       bytes = !b->written
+               ? sizeof(struct btree_node)
+               : sizeof(struct btree_node_entry);
+
+       bytes += b->whiteout_u64s * sizeof(u64);
+
+       for_each_bset(b, t) {
+               i = bset(b, t);
+
+               if (bset_written(b, i))
+                       continue;
+
+               bytes += le16_to_cpu(i->u64s) * sizeof(u64);
+               sort_iter_add(&sort_iter.iter,
+                             btree_bkey_first(b, t),
+                             btree_bkey_last(b, t));
+               seq = max(seq, le64_to_cpu(i->journal_seq));
+       }
+
+       BUG_ON(b->written && !seq);
+
+       /* bch2_varint_decode may read up to 7 bytes past the end of the buffer: */
+       bytes += 8;
+
+       /* buffer must be a multiple of the block size */
+       bytes = round_up(bytes, block_bytes(c));
+
+       data = btree_bounce_alloc(c, bytes, &used_mempool);
+
+       if (!b->written) {
+               bn = data;
+               *bn = *b->data;
+               i = &bn->keys;
+       } else {
+               bne = data;
+               bne->keys = b->data->keys;
+               i = &bne->keys;
+       }
+
+       i->journal_seq  = cpu_to_le64(seq);
+       i->u64s         = 0;
+
+       sort_iter_add(&sort_iter.iter,
+                     unwritten_whiteouts_start(c, b),
+                     unwritten_whiteouts_end(c, b));
+       SET_BSET_SEPARATE_WHITEOUTS(i, false);
+
+       b->whiteout_u64s = 0;
+
+       u64s = bch2_sort_keys(i->start, &sort_iter.iter, false);
+       le16_add_cpu(&i->u64s, u64s);
+
+       BUG_ON(!b->written && i->u64s != b->data->keys.u64s);
+
+       set_needs_whiteout(i, false);
+
+       /* do we have data to write? */
+       if (b->written && !i->u64s)
+               goto nowrite;
+
+       bytes_to_write = vstruct_end(i) - data;
+       sectors_to_write = round_up(bytes_to_write, block_bytes(c)) >> 9;
+
+       if (!b->written &&
+           b->key.k.type == KEY_TYPE_btree_ptr_v2)
+               BUG_ON(btree_ptr_sectors_written(&b->key) != sectors_to_write);
+
+       memset(data + bytes_to_write, 0,
+              (sectors_to_write << 9) - bytes_to_write);
+
+       BUG_ON(b->written + sectors_to_write > btree_sectors(c));
+       BUG_ON(BSET_BIG_ENDIAN(i) != CPU_BIG_ENDIAN);
+       BUG_ON(i->seq != b->data->keys.seq);
+
+       i->version = cpu_to_le16(c->sb.version);
+       SET_BSET_OFFSET(i, b->written);
+       SET_BSET_CSUM_TYPE(i, bch2_meta_checksum_type(c));
+
+       if (bch2_csum_type_is_encryption(BSET_CSUM_TYPE(i)))
+               validate_before_checksum = true;
+
+       /* validate_bset will be modifying: */
+       if (le16_to_cpu(i->version) < bcachefs_metadata_version_current)
+               validate_before_checksum = true;
+
+       /* if we're going to be encrypting, check metadata validity first: */
+       if (validate_before_checksum &&
+           validate_bset_for_write(c, b, i, sectors_to_write))
+               goto err;
+
+       ret = bset_encrypt(c, i, b->written << 9);
+       if (bch2_fs_fatal_err_on(ret, c,
+                       "error encrypting btree node: %i\n", ret))
+               goto err;
+
+       nonce = btree_nonce(i, b->written << 9);
+
+       if (bn)
+               bn->csum = csum_vstruct(c, BSET_CSUM_TYPE(i), nonce, bn);
+       else
+               bne->csum = csum_vstruct(c, BSET_CSUM_TYPE(i), nonce, bne);
+
+       /* if we're not encrypting, check metadata after checksumming: */
+       if (!validate_before_checksum &&
+           validate_bset_for_write(c, b, i, sectors_to_write))
+               goto err;
+
+       /*
+        * We handle btree write errors by immediately halting the journal -
+        * after we've done that, we can't issue any subsequent btree writes
+        * because they might have pointers to new nodes that failed to write.
+        *
+        * Furthermore, there's no point in doing any more btree writes because
+        * with the journal stopped, we're never going to update the journal to
+        * reflect that those writes were done and the data flushed from the
+        * journal:
+        *
+        * Also on journal error, the pending write may have updates that were
+        * never journalled (interior nodes, see btree_update_nodes_written()) -
+        * it's critical that we don't do the write in that case otherwise we
+        * will have updates visible that weren't in the journal:
+        *
+        * Make sure to update b->written so bch2_btree_init_next() doesn't
+        * break:
+        */
+       if (bch2_journal_error(&c->journal) ||
+           c->opts.nochanges)
+               goto err;
+
+       trace_and_count(c, btree_node_write, b, bytes_to_write, sectors_to_write);
+
+       wbio = container_of(bio_alloc_bioset(NULL,
+                               buf_pages(data, sectors_to_write << 9),
+                               REQ_OP_WRITE|REQ_META,
+                               GFP_NOFS,
+                               &c->btree_bio),
+                           struct btree_write_bio, wbio.bio);
+       wbio_init(&wbio->wbio.bio);
+       wbio->data                      = data;
+       wbio->data_bytes                = bytes;
+       wbio->sector_offset             = b->written;
+       wbio->wbio.c                    = c;
+       wbio->wbio.used_mempool         = used_mempool;
+       wbio->wbio.first_btree_write    = !b->written;
+       wbio->wbio.bio.bi_end_io        = btree_node_write_endio;
+       wbio->wbio.bio.bi_private       = b;
+
+       bch2_bio_map(&wbio->wbio.bio, data, sectors_to_write << 9);
+
+       bkey_copy(&wbio->key, &b->key);
+
+       b->written += sectors_to_write;
+
+       if (wbio->key.k.type == KEY_TYPE_btree_ptr_v2)
+               bkey_i_to_btree_ptr_v2(&wbio->key)->v.sectors_written =
+                       cpu_to_le16(b->written);
+
+       atomic64_inc(&c->btree_write_stats[type].nr);
+       atomic64_add(bytes_to_write, &c->btree_write_stats[type].bytes);
+
+       INIT_WORK(&wbio->work, btree_write_submit);
+       queue_work(c->io_complete_wq, &wbio->work);
+       return;
+err:
+       set_btree_node_noevict(b);
+       b->written += sectors_to_write;
+nowrite:
+       btree_bounce_free(c, bytes, used_mempool, data);
+       __btree_node_write_done(c, b);
+}
+
+/*
+ * Work that must be done with write lock held:
+ */
+bool bch2_btree_post_write_cleanup(struct bch_fs *c, struct btree *b)
+{
+       bool invalidated_iter = false;
+       struct btree_node_entry *bne;
+       struct bset_tree *t;
+
+       if (!btree_node_just_written(b))
+               return false;
+
+       BUG_ON(b->whiteout_u64s);
+
+       clear_btree_node_just_written(b);
+
+       /*
+        * Note: immediately after write, bset_written() doesn't work - the
+        * amount of data we had to write after compaction might have been
+        * smaller than the offset of the last bset.
+        *
+        * However, we know that all bsets have been written here, as long as
+        * we're still holding the write lock:
+        */
+
+       /*
+        * XXX: decide if we really want to unconditionally sort down to a
+        * single bset:
+        */
+       if (b->nsets > 1) {
+               btree_node_sort(c, b, 0, b->nsets, true);
+               invalidated_iter = true;
+       } else {
+               invalidated_iter = bch2_drop_whiteouts(b, COMPACT_ALL);
+       }
+
+       for_each_bset(b, t)
+               set_needs_whiteout(bset(b, t), true);
+
+       bch2_btree_verify(c, b);
+
+       /*
+        * If later we don't unconditionally sort down to a single bset, we have
+        * to ensure this is still true:
+        */
+       BUG_ON((void *) btree_bkey_last(b, bset_tree_last(b)) > write_block(b));
+
+       bne = want_new_bset(c, b);
+       if (bne)
+               bch2_bset_init_next(c, b, bne);
+
+       bch2_btree_build_aux_trees(b);
+
+       return invalidated_iter;
+}
+
+/*
+ * Use this one if the node is intent locked:
+ */
+void bch2_btree_node_write(struct bch_fs *c, struct btree *b,
+                          enum six_lock_type lock_type_held,
+                          unsigned flags)
+{
+       if (lock_type_held == SIX_LOCK_intent ||
+           (lock_type_held == SIX_LOCK_read &&
+            six_lock_tryupgrade(&b->c.lock))) {
+               __bch2_btree_node_write(c, b, flags);
+
+               /* don't cycle lock unnecessarily: */
+               if (btree_node_just_written(b) &&
+                   six_trylock_write(&b->c.lock)) {
+                       bch2_btree_post_write_cleanup(c, b);
+                       six_unlock_write(&b->c.lock);
+               }
+
+               if (lock_type_held == SIX_LOCK_read)
+                       six_lock_downgrade(&b->c.lock);
+       } else {
+               __bch2_btree_node_write(c, b, flags);
+               if (lock_type_held == SIX_LOCK_write &&
+                   btree_node_just_written(b))
+                       bch2_btree_post_write_cleanup(c, b);
+       }
+}
+
+static bool __bch2_btree_flush_all(struct bch_fs *c, unsigned flag)
+{
+       struct bucket_table *tbl;
+       struct rhash_head *pos;
+       struct btree *b;
+       unsigned i;
+       bool ret = false;
+restart:
+       rcu_read_lock();
+       for_each_cached_btree(b, c, tbl, i, pos)
+               if (test_bit(flag, &b->flags)) {
+                       rcu_read_unlock();
+                       wait_on_bit_io(&b->flags, flag, TASK_UNINTERRUPTIBLE);
+                       ret = true;
+                       goto restart;
+               }
+       rcu_read_unlock();
+
+       return ret;
+}
+
+bool bch2_btree_flush_all_reads(struct bch_fs *c)
+{
+       return __bch2_btree_flush_all(c, BTREE_NODE_read_in_flight);
+}
+
+bool bch2_btree_flush_all_writes(struct bch_fs *c)
+{
+       return __bch2_btree_flush_all(c, BTREE_NODE_write_in_flight);
+}
+
+static const char * const bch2_btree_write_types[] = {
+#define x(t, n) [n] = #t,
+       BCH_BTREE_WRITE_TYPES()
+       NULL
+};
+
+void bch2_btree_write_stats_to_text(struct printbuf *out, struct bch_fs *c)
+{
+       printbuf_tabstop_push(out, 20);
+       printbuf_tabstop_push(out, 10);
+
+       prt_tab(out);
+       prt_str(out, "nr");
+       prt_tab(out);
+       prt_str(out, "size");
+       prt_newline(out);
+
+       for (unsigned i = 0; i < BTREE_WRITE_TYPE_NR; i++) {
+               u64 nr          = atomic64_read(&c->btree_write_stats[i].nr);
+               u64 bytes       = atomic64_read(&c->btree_write_stats[i].bytes);
+
+               prt_printf(out, "%s:", bch2_btree_write_types[i]);
+               prt_tab(out);
+               prt_u64(out, nr);
+               prt_tab(out);
+               prt_human_readable_u64(out, nr ? div64_u64(bytes, nr) : 0);
+               prt_newline(out);
+       }
+}