]> git.sesse.net Git - bcachefs-tools-debian/blobdiff - libbcachefs/backpointers.c
Disable pristine-tar option in gbp.conf, since there is no pristine-tar branch.
[bcachefs-tools-debian] / libbcachefs / backpointers.c
index e001f41916713d44df03e944c1dc0ab23e4d2ed5..23fe9378fb40aa76d39d58e176614de50bd078e1 100644 (file)
@@ -3,8 +3,10 @@
 #include "bbpos.h"
 #include "alloc_background.h"
 #include "backpointers.h"
+#include "bkey_buf.h"
 #include "btree_cache.h"
 #include "btree_update.h"
+#include "btree_update_interior.h"
 #include "btree_write_buffer.h"
 #include "error.h"
 
@@ -37,29 +39,26 @@ static bool extent_matches_bp(struct bch_fs *c,
        return false;
 }
 
-int bch2_backpointer_invalid(const struct bch_fs *c, struct bkey_s_c k,
-                            unsigned flags, struct printbuf *err)
+int bch2_backpointer_invalid(struct bch_fs *c, struct bkey_s_c k,
+                            enum bkey_invalid_flags flags,
+                            struct printbuf *err)
 {
        struct bkey_s_c_backpointer bp = bkey_s_c_to_backpointer(k);
        struct bpos bucket = bp_pos_to_bucket(c, bp.k->p);
+       int ret = 0;
 
-       if (bkey_val_bytes(bp.k) < sizeof(*bp.v)) {
-               prt_str(err, "incorrect value size");
-               return -BCH_ERR_invalid_bkey;
-       }
-
-       if (!bpos_eq(bp.k->p, bucket_pos_to_bp(c, bucket, bp.v->bucket_offset))) {
-               prt_str(err, "backpointer at wrong pos");
-               return -BCH_ERR_invalid_bkey;
-       }
-
-       return 0;
+       bkey_fsck_err_on(!bpos_eq(bp.k->p, bucket_pos_to_bp(c, bucket, bp.v->bucket_offset)),
+                        c, err,
+                        backpointer_pos_wrong,
+                        "backpointer at wrong pos");
+fsck_err:
+       return ret;
 }
 
 void bch2_backpointer_to_text(struct printbuf *out, const struct bch_backpointer *bp)
 {
        prt_printf(out, "btree=%s l=%u offset=%llu:%u len=%u pos=",
-              bch2_btree_ids[bp->btree_id],
+              bch2_btree_id_str(bp->btree_id),
               bp->level,
               (u64) (bp->bucket_offset >> MAX_EXTENT_COMPRESS_RATIO_SHIFT),
               (u32) bp->bucket_offset & ~(~0U << MAX_EXTENT_COMPRESS_RATIO_SHIFT),
@@ -69,6 +68,10 @@ void bch2_backpointer_to_text(struct printbuf *out, const struct bch_backpointer
 
 void bch2_backpointer_k_to_text(struct printbuf *out, struct bch_fs *c, struct bkey_s_c k)
 {
+       prt_str(out, "bucket=");
+       bch2_bpos_to_text(out, bp_pos_to_bucket(c, k.k->p));
+       prt_str(out, " ");
+
        bch2_backpointer_to_text(out, bkey_s_c_to_backpointer(k).v);
 }
 
@@ -76,122 +79,11 @@ void bch2_backpointer_swab(struct bkey_s k)
 {
        struct bkey_s_backpointer bp = bkey_s_to_backpointer(k);
 
-       bp.v->bucket_offset     = swab32(bp.v->bucket_offset);
+       bp.v->bucket_offset     = swab40(bp.v->bucket_offset);
        bp.v->bucket_len        = swab32(bp.v->bucket_len);
        bch2_bpos_swab(&bp.v->pos);
 }
 
-#define BACKPOINTER_OFFSET_MAX ((1ULL << 40) - 1)
-
-static inline int backpointer_cmp(struct bch_backpointer l, struct bch_backpointer r)
-{
-       return cmp_int(l.bucket_offset, r.bucket_offset);
-}
-
-static int bch2_backpointer_del_by_offset(struct btree_trans *trans,
-                                         struct bpos bucket,
-                                         u64 bp_offset,
-                                         struct bch_backpointer bp)
-{
-       struct bch_fs *c = trans->c;
-       struct btree_iter iter;
-       struct bkey_s_c k;
-       int ret;
-
-       if (bp_offset < BACKPOINTER_OFFSET_MAX) {
-               struct bch_backpointer *bps;
-               struct bkey_i_alloc_v4 *a;
-               unsigned i, nr;
-
-               bch2_trans_iter_init(trans, &iter, BTREE_ID_alloc,
-                                    bucket,
-                                    BTREE_ITER_INTENT|
-                                    BTREE_ITER_SLOTS|
-                                    BTREE_ITER_WITH_UPDATES);
-               k = bch2_btree_iter_peek_slot(&iter);
-               ret = bkey_err(k);
-               if (ret)
-                       goto err;
-
-               if (k.k->type != KEY_TYPE_alloc_v4) {
-                       ret = -ENOENT;
-                       goto err;
-               }
-
-               a = bch2_alloc_to_v4_mut(trans, k);
-               ret = PTR_ERR_OR_ZERO(a);
-               if (ret)
-                       goto err;
-               bps = alloc_v4_backpointers(&a->v);
-               nr = BCH_ALLOC_V4_NR_BACKPOINTERS(&a->v);
-
-               for (i = 0; i < nr; i++) {
-                       if (bps[i].bucket_offset == bp_offset)
-                               goto found;
-                       if (bps[i].bucket_offset > bp_offset)
-                               break;
-               }
-
-               ret = -ENOENT;
-               goto err;
-found:
-               if (memcmp(&bps[i], &bp, sizeof(bp))) {
-                       ret = -ENOENT;
-                       goto err;
-               }
-               array_remove_item(bps, nr, i);
-               SET_BCH_ALLOC_V4_NR_BACKPOINTERS(&a->v, nr);
-               set_alloc_v4_u64s(a);
-               ret = bch2_trans_update(trans, &iter, &a->k_i, 0);
-       } else {
-               bp_offset -= BACKPOINTER_OFFSET_MAX;
-
-               bch2_trans_iter_init(trans, &iter, BTREE_ID_backpointers,
-                                    bucket_pos_to_bp(c, bucket, bp_offset),
-                                    BTREE_ITER_INTENT|
-                                    BTREE_ITER_SLOTS|
-                                    BTREE_ITER_WITH_UPDATES);
-               k = bch2_btree_iter_peek_slot(&iter);
-               ret = bkey_err(k);
-               if (ret)
-                       goto err;
-
-               if (k.k->type != KEY_TYPE_backpointer ||
-                   memcmp(bkey_s_c_to_backpointer(k).v, &bp, sizeof(bp))) {
-                       ret = -ENOENT;
-                       goto err;
-               }
-
-               ret = bch2_btree_delete_at(trans, &iter, 0);
-       }
-err:
-       bch2_trans_iter_exit(trans, &iter);
-       return ret;
-}
-
-bool bch2_bucket_backpointer_del(struct btree_trans *trans,
-                                struct bkey_i_alloc_v4 *a,
-                                struct bch_backpointer bp)
-{
-       struct bch_backpointer *bps = alloc_v4_backpointers(&a->v);
-       unsigned i, nr = BCH_ALLOC_V4_NR_BACKPOINTERS(&a->v);
-
-       for (i = 0; i < nr; i++) {
-               int cmp = backpointer_cmp(bps[i], bp) ?:
-                       memcmp(&bps[i], &bp, sizeof(bp));
-               if (!cmp) {
-                       array_remove_item(bps, nr, i);
-                       SET_BCH_ALLOC_V4_NR_BACKPOINTERS(&a->v, nr);
-                       set_alloc_v4_u64s(a);
-                       return true;
-               }
-               if (cmp >= 0)
-                       break;
-       }
-
-       return false;
-}
-
 static noinline int backpointer_mod_err(struct btree_trans *trans,
                                        struct bch_backpointer bp,
                                        struct bkey_s_c bp_k,
@@ -215,7 +107,7 @@ static noinline int backpointer_mod_err(struct btree_trans *trans,
                bch2_bkey_val_to_text(&buf, c, orig_k);
 
                bch_err(c, "%s", buf.buf);
-       } else if (test_bit(BCH_FS_CHECK_BACKPOINTERS_DONE, &c->flags)) {
+       } else if (c->curr_recovery_pass > BCH_RECOVERY_PASS_check_extents_to_backpointers) {
                prt_printf(&buf, "backpointer not found when deleting");
                prt_newline(&buf);
                printbuf_indent_add(&buf, 2);
@@ -236,24 +128,22 @@ static noinline int backpointer_mod_err(struct btree_trans *trans,
 
        printbuf_exit(&buf);
 
-       if (test_bit(BCH_FS_CHECK_BACKPOINTERS_DONE, &c->flags)) {
-               bch2_inconsistent_error(c);
-               return -EIO;
+       if (c->curr_recovery_pass > BCH_RECOVERY_PASS_check_extents_to_backpointers) {
+               return bch2_inconsistent_error(c) ? BCH_ERR_erofs_unfixed_errors : 0;
        } else {
                return 0;
        }
 }
 
 int bch2_bucket_backpointer_mod_nowritebuffer(struct btree_trans *trans,
-                               struct bkey_i_alloc_v4 *a,
+                               struct bpos bucket,
                                struct bch_backpointer bp,
                                struct bkey_s_c orig_k,
                                bool insert)
 {
-       struct bch_fs *c = trans->c;
-       struct bkey_i_backpointer *bp_k;
        struct btree_iter bp_iter;
        struct bkey_s_c k;
+       struct bkey_i_backpointer *bp_k;
        int ret;
 
        bp_k = bch2_trans_kmalloc_nomemzero(trans, sizeof(struct bkey_i_backpointer));
@@ -262,7 +152,7 @@ int bch2_bucket_backpointer_mod_nowritebuffer(struct btree_trans *trans,
                return ret;
 
        bkey_backpointer_init(&bp_k->k_i);
-       bp_k->k.p = bucket_pos_to_bp(c, a->k.p, bp.bucket_offset);
+       bp_k->k.p = bucket_pos_to_bp(trans->c, bucket, bp.bucket_offset);
        bp_k->v = bp;
 
        if (!insert) {
@@ -270,12 +160,11 @@ int bch2_bucket_backpointer_mod_nowritebuffer(struct btree_trans *trans,
                set_bkey_val_u64s(&bp_k->k, 0);
        }
 
-       bch2_trans_iter_init(trans, &bp_iter, BTREE_ID_backpointers,
-                            bucket_pos_to_bp(c, a->k.p, bp.bucket_offset),
-                            BTREE_ITER_INTENT|
-                            BTREE_ITER_SLOTS|
-                            BTREE_ITER_WITH_UPDATES);
-       k = bch2_btree_iter_peek_slot(&bp_iter);
+       k = bch2_bkey_get_iter(trans, &bp_iter, BTREE_ID_backpointers,
+                              bp_k->k.p,
+                              BTREE_ITER_INTENT|
+                              BTREE_ITER_SLOTS|
+                              BTREE_ITER_WITH_UPDATES);
        ret = bkey_err(k);
        if (ret)
                goto err;
@@ -300,62 +189,44 @@ err:
  */
 int bch2_get_next_backpointer(struct btree_trans *trans,
                              struct bpos bucket, int gen,
-                             u64 *bp_offset,
-                             struct bch_backpointer *dst,
+                             struct bpos *bp_pos,
+                             struct bch_backpointer *bp,
                              unsigned iter_flags)
 {
        struct bch_fs *c = trans->c;
-       struct bpos bp_pos, bp_end_pos;
-       struct btree_iter alloc_iter, bp_iter = { NULL };
+       struct bpos bp_end_pos = bucket_pos_to_bp(c, bpos_nosnap_successor(bucket), 0);
+       struct btree_iter alloc_iter = { NULL }, bp_iter = { NULL };
        struct bkey_s_c k;
-       struct bkey_s_c_alloc_v4 a;
-       size_t i;
-       int ret;
-
-       if (*bp_offset == U64_MAX)
-               return 0;
-
-       bp_pos = bucket_pos_to_bp(c, bucket,
-                                 max(*bp_offset, BACKPOINTER_OFFSET_MAX) - BACKPOINTER_OFFSET_MAX);
-       bp_end_pos = bucket_pos_to_bp(c, bpos_nosnap_successor(bucket), 0);
-
-       bch2_trans_iter_init(trans, &alloc_iter, BTREE_ID_alloc,
-                            bucket, BTREE_ITER_CACHED);
-       k = bch2_btree_iter_peek_slot(&alloc_iter);
-       ret = bkey_err(k);
-       if (ret)
-               goto out;
-
-       if (k.k->type != KEY_TYPE_alloc_v4)
-               goto done;
+       int ret = 0;
 
-       a = bkey_s_c_to_alloc_v4(k);
-       if (gen >= 0 && a.v->gen != gen)
+       if (bpos_ge(*bp_pos, bp_end_pos))
                goto done;
 
-       for (i = 0; i < BCH_ALLOC_V4_NR_BACKPOINTERS(a.v); i++) {
-               if (alloc_v4_backpointers_c(a.v)[i].bucket_offset < *bp_offset)
-                       continue;
+       if (gen >= 0) {
+               k = bch2_bkey_get_iter(trans, &alloc_iter, BTREE_ID_alloc,
+                                      bucket, BTREE_ITER_CACHED|iter_flags);
+               ret = bkey_err(k);
+               if (ret)
+                       goto out;
 
-               *dst = alloc_v4_backpointers_c(a.v)[i];
-               *bp_offset = dst->bucket_offset;
-               goto out;
+               if (k.k->type != KEY_TYPE_alloc_v4 ||
+                   bkey_s_c_to_alloc_v4(k).v->gen != gen)
+                       goto done;
        }
 
+       *bp_pos = bpos_max(*bp_pos, bucket_pos_to_bp(c, bucket, 0));
+
        for_each_btree_key_norestart(trans, bp_iter, BTREE_ID_backpointers,
-                                    bp_pos, 0, k, ret) {
+                                    *bp_pos, iter_flags, k, ret) {
                if (bpos_ge(k.k->p, bp_end_pos))
                        break;
 
-               if (k.k->type != KEY_TYPE_backpointer)
-                       continue;
-
-               *dst = *bkey_s_c_to_backpointer(k).v;
-               *bp_offset = dst->bucket_offset + BACKPOINTER_OFFSET_MAX;
+               *bp_pos = k.k->p;
+               *bp = *bkey_s_c_to_backpointer(k).v;
                goto out;
        }
 done:
-       *bp_offset = U64_MAX;
+       *bp_pos = SPOS_MAX;
 out:
        bch2_trans_iter_exit(trans, &bp_iter);
        bch2_trans_iter_exit(trans, &alloc_iter);
@@ -363,37 +234,36 @@ out:
 }
 
 static void backpointer_not_found(struct btree_trans *trans,
-                                 struct bpos bucket,
-                                 u64 bp_offset,
+                                 struct bpos bp_pos,
                                  struct bch_backpointer bp,
-                                 struct bkey_s_c k,
-                                 const char *thing_it_points_to)
+                                 struct bkey_s_c k)
 {
        struct bch_fs *c = trans->c;
        struct printbuf buf = PRINTBUF;
+       struct bpos bucket = bp_pos_to_bucket(c, bp_pos);
 
+       /*
+        * If we're using the btree write buffer, the backpointer we were
+        * looking at may have already been deleted - failure to find what it
+        * pointed to is not an error:
+        */
        if (likely(!bch2_backpointers_no_use_write_buffer))
                return;
 
        prt_printf(&buf, "backpointer doesn't match %s it points to:\n  ",
-                  thing_it_points_to);
+                  bp.level ? "btree node" : "extent");
        prt_printf(&buf, "bucket: ");
        bch2_bpos_to_text(&buf, bucket);
        prt_printf(&buf, "\n  ");
 
-       if (bp_offset >= BACKPOINTER_OFFSET_MAX) {
-               struct bpos bp_pos =
-                       bucket_pos_to_bp(c, bucket,
-                                       bp_offset - BACKPOINTER_OFFSET_MAX);
-               prt_printf(&buf, "backpointer pos: ");
-               bch2_bpos_to_text(&buf, bp_pos);
-               prt_printf(&buf, "\n  ");
-       }
+       prt_printf(&buf, "backpointer pos: ");
+       bch2_bpos_to_text(&buf, bp_pos);
+       prt_printf(&buf, "\n  ");
 
        bch2_backpointer_to_text(&buf, &bp);
        prt_printf(&buf, "\n  ");
        bch2_bkey_val_to_text(&buf, c, k);
-       if (!test_bit(BCH_FS_CHECK_BACKPOINTERS_DONE, &c->flags))
+       if (c->curr_recovery_pass >= BCH_RECOVERY_PASS_check_extents_to_backpointers)
                bch_err_ratelimited(c, "%s", buf.buf);
        else
                bch2_trans_inconsistent(trans, "%s", buf.buf);
@@ -403,67 +273,50 @@ static void backpointer_not_found(struct btree_trans *trans,
 
 struct bkey_s_c bch2_backpointer_get_key(struct btree_trans *trans,
                                         struct btree_iter *iter,
-                                        struct bpos bucket,
-                                        u64 bp_offset,
-                                        struct bch_backpointer bp)
+                                        struct bpos bp_pos,
+                                        struct bch_backpointer bp,
+                                        unsigned iter_flags)
 {
-       struct bch_fs *c = trans->c;
-       struct bkey_s_c k;
-
-       bch2_trans_node_iter_init(trans, iter,
-                                 bp.btree_id,
-                                 bp.pos,
-                                 0,
-                                 min(bp.level, c->btree_roots[bp.btree_id].level),
-                                 0);
-       k = bch2_btree_iter_peek_slot(iter);
-       if (bkey_err(k)) {
-               bch2_trans_iter_exit(trans, iter);
-               return k;
-       }
-
-       if (bp.level == c->btree_roots[bp.btree_id].level + 1)
-               k = bkey_i_to_s_c(&c->btree_roots[bp.btree_id].key);
-
-       if (k.k && extent_matches_bp(c, bp.btree_id, bp.level, k, bucket, bp))
-               return k;
-
-       bch2_trans_iter_exit(trans, iter);
+       if (likely(!bp.level)) {
+               struct bch_fs *c = trans->c;
+               struct bpos bucket = bp_pos_to_bucket(c, bp_pos);
+               struct bkey_s_c k;
+
+               bch2_trans_node_iter_init(trans, iter,
+                                         bp.btree_id,
+                                         bp.pos,
+                                         0, 0,
+                                         iter_flags);
+               k = bch2_btree_iter_peek_slot(iter);
+               if (bkey_err(k)) {
+                       bch2_trans_iter_exit(trans, iter);
+                       return k;
+               }
 
-       if (unlikely(bch2_backpointers_no_use_write_buffer)) {
-               if (bp.level) {
-                       struct btree *b;
+               if (k.k && extent_matches_bp(c, bp.btree_id, bp.level, k, bucket, bp))
+                       return k;
 
-                       /*
-                        * If a backpointer for a btree node wasn't found, it may be
-                        * because it was overwritten by a new btree node that hasn't
-                        * been written out yet - backpointer_get_node() checks for
-                        * this:
-                        */
-                       b = bch2_backpointer_get_node(trans, iter, bucket, bp_offset, bp);
-                       if (!IS_ERR_OR_NULL(b))
-                               return bkey_i_to_s_c(&b->key);
+               bch2_trans_iter_exit(trans, iter);
+               backpointer_not_found(trans, bp_pos, bp, k);
+               return bkey_s_c_null;
+       } else {
+               struct btree *b = bch2_backpointer_get_node(trans, iter, bp_pos, bp);
 
+               if (IS_ERR_OR_NULL(b)) {
                        bch2_trans_iter_exit(trans, iter);
-
-                       if (IS_ERR(b))
-                               return bkey_s_c_err(PTR_ERR(b));
-                       return bkey_s_c_null;
+                       return IS_ERR(b) ? bkey_s_c_err(PTR_ERR(b)) : bkey_s_c_null;
                }
-
-               backpointer_not_found(trans, bucket, bp_offset, bp, k, "extent");
+               return bkey_i_to_s_c(&b->key);
        }
-
-       return bkey_s_c_null;
 }
 
 struct btree *bch2_backpointer_get_node(struct btree_trans *trans,
                                        struct btree_iter *iter,
-                                       struct bpos bucket,
-                                       u64 bp_offset,
+                                       struct bpos bp_pos,
                                        struct bch_backpointer bp)
 {
        struct bch_fs *c = trans->c;
+       struct bpos bucket = bp_pos_to_bucket(c, bp_pos);
        struct btree *b;
 
        BUG_ON(!bp.level);
@@ -475,19 +328,20 @@ struct btree *bch2_backpointer_get_node(struct btree_trans *trans,
                                  bp.level - 1,
                                  0);
        b = bch2_btree_iter_peek_node(iter);
-       if (IS_ERR(b))
+       if (IS_ERR_OR_NULL(b))
                goto err;
 
-       if (b && extent_matches_bp(c, bp.btree_id, bp.level,
-                                  bkey_i_to_s_c(&b->key),
-                                  bucket, bp))
+       BUG_ON(b->c.level != bp.level - 1);
+
+       if (extent_matches_bp(c, bp.btree_id, bp.level,
+                             bkey_i_to_s_c(&b->key),
+                             bucket, bp))
                return b;
 
-       if (b && btree_node_will_make_reachable(b)) {
+       if (btree_node_will_make_reachable(b)) {
                b = ERR_PTR(-BCH_ERR_backpointer_to_overwritten_btree_node);
        } else {
-               backpointer_not_found(trans, bucket, bp_offset, bp,
-                                     bkey_i_to_s_c(&b->key), "btree node");
+               backpointer_not_found(trans, bp_pos, bp, bkey_i_to_s_c(&b->key));
                b = NULL;
        }
 err:
@@ -500,29 +354,26 @@ static int bch2_check_btree_backpointer(struct btree_trans *trans, struct btree_
 {
        struct bch_fs *c = trans->c;
        struct btree_iter alloc_iter = { NULL };
-       struct bch_dev *ca;
        struct bkey_s_c alloc_k;
        struct printbuf buf = PRINTBUF;
        int ret = 0;
 
        if (fsck_err_on(!bch2_dev_exists2(c, k.k->p.inode), c,
-                       "backpointer for mising device:\n%s",
+                       backpointer_to_missing_device,
+                       "backpointer for missing device:\n%s",
                        (bch2_bkey_val_to_text(&buf, c, k), buf.buf))) {
                ret = bch2_btree_delete_at(trans, bp_iter, 0);
                goto out;
        }
 
-       ca = bch_dev_bkey_exists(c, k.k->p.inode);
-
-       bch2_trans_iter_init(trans, &alloc_iter, BTREE_ID_alloc,
-                            bp_pos_to_bucket(c, k.k->p), 0);
-
-       alloc_k = bch2_btree_iter_peek_slot(&alloc_iter);
+       alloc_k = bch2_bkey_get_iter(trans, &alloc_iter, BTREE_ID_alloc,
+                                    bp_pos_to_bucket(c, k.k->p), 0);
        ret = bkey_err(alloc_k);
        if (ret)
                goto out;
 
        if (fsck_err_on(alloc_k.k->type != KEY_TYPE_alloc_v4, c,
+                       backpointer_to_missing_alloc,
                        "backpointer for nonexistent alloc key: %llu:%llu:0\n%s",
                        alloc_iter.pos.inode, alloc_iter.pos.offset,
                        (bch2_bkey_val_to_text(&buf, c, alloc_k), buf.buf))) {
@@ -539,71 +390,73 @@ fsck_err:
 /* verify that every backpointer has a corresponding alloc key */
 int bch2_check_btree_backpointers(struct bch_fs *c)
 {
-       struct btree_iter iter;
-       struct bkey_s_c k;
-
-       return bch2_trans_run(c,
-               for_each_btree_key_commit(&trans, iter,
+       int ret = bch2_trans_run(c,
+               for_each_btree_key_commit(trans, iter,
                        BTREE_ID_backpointers, POS_MIN, 0, k,
-                       NULL, NULL, BTREE_INSERT_LAZY_RW|BTREE_INSERT_NOFAIL,
-                 bch2_check_btree_backpointer(&trans, &iter, k)));
+                       NULL, NULL, BCH_TRANS_COMMIT_no_enospc,
+                 bch2_check_btree_backpointer(trans, &iter, k)));
+       bch_err_fn(c, ret);
+       return ret;
+}
+
+static inline bool bkey_and_val_eq(struct bkey_s_c l, struct bkey_s_c r)
+{
+       return bpos_eq(l.k->p, r.k->p) &&
+               bkey_bytes(l.k) == bkey_bytes(r.k) &&
+               !memcmp(l.v, r.v, bkey_val_bytes(l.k));
 }
 
+struct extents_to_bp_state {
+       struct bpos     bucket_start;
+       struct bpos     bucket_end;
+       struct bkey_buf last_flushed;
+};
+
 static int check_bp_exists(struct btree_trans *trans,
-                          struct bpos bucket_pos,
+                          struct extents_to_bp_state *s,
+                          struct bpos bucket,
                           struct bch_backpointer bp,
-                          struct bkey_s_c orig_k,
-                          struct bpos bucket_start,
-                          struct bpos bucket_end,
-                          struct bpos *last_flushed_pos)
+                          struct bkey_s_c orig_k)
 {
        struct bch_fs *c = trans->c;
-       struct btree_iter alloc_iter, bp_iter = { NULL };
+       struct btree_iter bp_iter = { NULL };
        struct printbuf buf = PRINTBUF;
-       struct bkey_s_c alloc_k, bp_k;
+       struct bkey_s_c bp_k;
+       struct bkey_buf tmp;
        int ret;
 
-       if (bpos_lt(bucket_pos, bucket_start) ||
-           bpos_gt(bucket_pos, bucket_end))
-               return 0;
+       bch2_bkey_buf_init(&tmp);
 
-       bch2_trans_iter_init(trans, &alloc_iter, BTREE_ID_alloc, bucket_pos, 0);
-       alloc_k = bch2_btree_iter_peek_slot(&alloc_iter);
-       ret = bkey_err(alloc_k);
-       if (ret)
-               goto err;
+       if (bpos_lt(bucket, s->bucket_start) ||
+           bpos_gt(bucket, s->bucket_end))
+               return 0;
 
-       if (alloc_k.k->type == KEY_TYPE_alloc_v4) {
-               struct bkey_s_c_alloc_v4 a = bkey_s_c_to_alloc_v4(alloc_k);
-               const struct bch_backpointer *bps = alloc_v4_backpointers_c(a.v);
-               unsigned i, nr = BCH_ALLOC_V4_NR_BACKPOINTERS(a.v);
-
-               for (i = 0; i < nr; i++) {
-                       int cmp = backpointer_cmp(bps[i], bp) ?:
-                               memcmp(&bps[i], &bp, sizeof(bp));
-                       if (!cmp)
-                               goto out;
-                       if (cmp >= 0)
-                               break;
-               }
-       } else {
+       if (!bch2_dev_bucket_exists(c, bucket))
                goto missing;
-       }
 
-       bch2_trans_iter_init(trans, &bp_iter, BTREE_ID_backpointers,
-                            bucket_pos_to_bp(c, bucket_pos, bp.bucket_offset),
-                            0);
-       bp_k = bch2_btree_iter_peek_slot(&bp_iter);
+       bp_k = bch2_bkey_get_iter(trans, &bp_iter, BTREE_ID_backpointers,
+                                 bucket_pos_to_bp(c, bucket, bp.bucket_offset),
+                                 0);
        ret = bkey_err(bp_k);
        if (ret)
                goto err;
 
        if (bp_k.k->type != KEY_TYPE_backpointer ||
            memcmp(bkey_s_c_to_backpointer(bp_k).v, &bp, sizeof(bp))) {
-               if (!bpos_eq(*last_flushed_pos, orig_k.k->p)) {
-                       *last_flushed_pos = orig_k.k->p;
-                       ret = bch2_btree_write_buffer_flush_sync(trans) ?:
-                               -BCH_ERR_transaction_restart_write_buffer_flush;
+               bch2_bkey_buf_reassemble(&tmp, c, orig_k);
+
+               if (!bkey_and_val_eq(orig_k, bkey_i_to_s_c(s->last_flushed.k))) {
+                       if (bp.level) {
+                               bch2_trans_unlock(trans);
+                               bch2_btree_interior_updates_flush(c);
+                       }
+
+                       ret = bch2_btree_write_buffer_flush_sync(trans);
+                       if (ret)
+                               goto err;
+
+                       bch2_bkey_buf_copy(&s->last_flushed, c, tmp.k);
+                       ret = -BCH_ERR_transaction_restart_write_buffer_flush;
                        goto out;
                }
                goto missing;
@@ -612,49 +465,34 @@ out:
 err:
 fsck_err:
        bch2_trans_iter_exit(trans, &bp_iter);
-       bch2_trans_iter_exit(trans, &alloc_iter);
+       bch2_bkey_buf_exit(&tmp, c);
        printbuf_exit(&buf);
        return ret;
 missing:
-
        prt_printf(&buf, "missing backpointer for btree=%s l=%u ",
-              bch2_btree_ids[bp.btree_id], bp.level);
+              bch2_btree_id_str(bp.btree_id), bp.level);
        bch2_bkey_val_to_text(&buf, c, orig_k);
        prt_printf(&buf, "\nbp pos ");
        bch2_bpos_to_text(&buf, bp_iter.pos);
 
-       if (c->sb.version < bcachefs_metadata_version_backpointers ||
-           c->opts.reconstruct_alloc ||
-           fsck_err(c, "%s", buf.buf)) {
-               struct bkey_i_alloc_v4 *a = bch2_alloc_to_v4_mut(trans, alloc_k);
-
-               ret   = PTR_ERR_OR_ZERO(a) ?:
-                       bch2_bucket_backpointer_mod(trans, a, bp, orig_k, true);
-       }
+       if (c->opts.reconstruct_alloc ||
+           fsck_err(c, ptr_to_missing_backpointer, "%s", buf.buf))
+               ret = bch2_bucket_backpointer_mod(trans, bucket, bp, orig_k, true);
 
        goto out;
 }
 
 static int check_extent_to_backpointers(struct btree_trans *trans,
-                                       struct btree_iter *iter,
-                                       struct bpos bucket_start,
-                                       struct bpos bucket_end,
-                                       struct bpos *last_flushed_pos)
+                                       struct extents_to_bp_state *s,
+                                       enum btree_id btree, unsigned level,
+                                       struct bkey_s_c k)
 {
        struct bch_fs *c = trans->c;
        struct bkey_ptrs_c ptrs;
        const union bch_extent_entry *entry;
        struct extent_ptr_decoded p;
-       struct bkey_s_c k;
        int ret;
 
-       k = bch2_btree_iter_peek_all_levels(iter);
-       ret = bkey_err(k);
-       if (ret)
-               return ret;
-       if (!k.k)
-               return 0;
-
        ptrs = bch2_bkey_ptrs_c(k);
        bkey_for_each_ptr_decode(k.k, ptrs, p, entry) {
                struct bpos bucket_pos;
@@ -663,12 +501,10 @@ static int check_extent_to_backpointers(struct btree_trans *trans,
                if (p.ptr.cached)
                        continue;
 
-               bch2_extent_ptr_to_bp(c, iter->btree_id, iter->path->level,
+               bch2_extent_ptr_to_bp(c, btree, level,
                                      k, p, &bucket_pos, &bp);
 
-               ret = check_bp_exists(trans, bucket_pos, bp, k,
-                                     bucket_start, bucket_end,
-                                     last_flushed_pos);
+               ret = check_bp_exists(trans, s, bucket_pos, bp, k);
                if (ret)
                        return ret;
        }
@@ -677,47 +513,32 @@ static int check_extent_to_backpointers(struct btree_trans *trans,
 }
 
 static int check_btree_root_to_backpointers(struct btree_trans *trans,
+                                           struct extents_to_bp_state *s,
                                            enum btree_id btree_id,
-                                           struct bpos bucket_start,
-                                           struct bpos bucket_end,
-                                           struct bpos *last_flushed_pos)
+                                           int *level)
 {
        struct bch_fs *c = trans->c;
        struct btree_iter iter;
        struct btree *b;
        struct bkey_s_c k;
-       struct bkey_ptrs_c ptrs;
-       struct extent_ptr_decoded p;
-       const union bch_extent_entry *entry;
        int ret;
-
-       bch2_trans_node_iter_init(trans, &iter, btree_id, POS_MIN, 0,
-                                 c->btree_roots[btree_id].level, 0);
+retry:
+       bch2_trans_node_iter_init(trans, &iter, btree_id, POS_MIN,
+                                 0, bch2_btree_id_root(c, btree_id)->b->c.level, 0);
        b = bch2_btree_iter_peek_node(&iter);
        ret = PTR_ERR_OR_ZERO(b);
        if (ret)
                goto err;
 
-       BUG_ON(b != btree_node_root(c, b));
-
-       k = bkey_i_to_s_c(&b->key);
-       ptrs = bch2_bkey_ptrs_c(k);
-       bkey_for_each_ptr_decode(k.k, ptrs, p, entry) {
-               struct bpos bucket_pos;
-               struct bch_backpointer bp;
-
-               if (p.ptr.cached)
-                       continue;
+       if (b != btree_node_root(c, b)) {
+               bch2_trans_iter_exit(trans, &iter);
+               goto retry;
+       }
 
-               bch2_extent_ptr_to_bp(c, iter.btree_id, iter.path->level + 1,
-                                     k, p, &bucket_pos, &bp);
+       *level = b->c.level;
 
-               ret = check_bp_exists(trans, bucket_pos, bp, k,
-                                     bucket_start, bucket_end,
-                                     last_flushed_pos);
-               if (ret)
-                       goto err;
-       }
+       k = bkey_i_to_s_c(&b->key);
+       ret = check_extent_to_backpointers(trans, s, btree_id, b->c.level + 1, k);
 err:
        bch2_trans_iter_exit(trans, &iter);
        return ret;
@@ -731,243 +552,214 @@ static inline struct bbpos bp_to_bbpos(struct bch_backpointer bp)
        };
 }
 
-static size_t btree_nodes_fit_in_ram(struct bch_fs *c)
+static u64 mem_may_pin_bytes(struct bch_fs *c)
 {
        struct sysinfo i;
-       u64 mem_bytes;
-
        si_meminfo(&i);
-       mem_bytes = i.totalram * i.mem_unit;
-       return div_u64(mem_bytes >> 1, btree_bytes(c));
+
+       u64 mem_bytes = i.totalram * i.mem_unit;
+       return div_u64(mem_bytes * c->opts.fsck_memory_usage_percent, 100);
 }
 
-int bch2_get_btree_in_memory_pos(struct btree_trans *trans,
-                                unsigned btree_leaf_mask,
-                                unsigned btree_interior_mask,
-                                struct bbpos start, struct bbpos *end)
+static size_t btree_nodes_fit_in_ram(struct bch_fs *c)
 {
-       struct btree_iter iter;
-       struct bkey_s_c k;
-       size_t btree_nodes = btree_nodes_fit_in_ram(trans->c);
-       enum btree_id btree;
+       return div_u64(mem_may_pin_bytes(c), c->opts.btree_node_size);
+}
+
+static int bch2_get_btree_in_memory_pos(struct btree_trans *trans,
+                                       u64 btree_leaf_mask,
+                                       u64 btree_interior_mask,
+                                       struct bbpos start, struct bbpos *end)
+{
+       struct bch_fs *c = trans->c;
+       s64 mem_may_pin = mem_may_pin_bytes(c);
        int ret = 0;
 
-       for (btree = start.btree; btree < BTREE_ID_NR && !ret; btree++) {
-               unsigned depth = ((1U << btree) & btree_leaf_mask) ? 1 : 2;
+       btree_interior_mask |= btree_leaf_mask;
+
+       c->btree_cache.pinned_nodes_leaf_mask           = btree_leaf_mask;
+       c->btree_cache.pinned_nodes_interior_mask       = btree_interior_mask;
+       c->btree_cache.pinned_nodes_start               = start;
+       c->btree_cache.pinned_nodes_end                 = *end = BBPOS_MAX;
+
+       for (enum btree_id btree = start.btree;
+            btree < BTREE_ID_NR && !ret;
+            btree++) {
+               unsigned depth = ((1U << btree) & btree_leaf_mask) ? 0 : 1;
+               struct btree_iter iter;
+               struct btree *b;
 
                if (!((1U << btree) & btree_leaf_mask) &&
                    !((1U << btree) & btree_interior_mask))
                        continue;
 
-               bch2_trans_node_iter_init(trans, &iter, btree,
-                                         btree == start.btree ? start.pos : POS_MIN,
-                                         0, depth, 0);
-               /*
-                * for_each_btree_key_contineu() doesn't check the return value
-                * from bch2_btree_iter_advance(), which is needed when
-                * iterating over interior nodes where we'll see keys at
-                * SPOS_MAX:
-                */
-               do {
-                       k = __bch2_btree_iter_peek_and_restart(trans, &iter, 0);
-                       ret = bkey_err(k);
-                       if (!k.k || ret)
-                               break;
-
-                       --btree_nodes;
-                       if (!btree_nodes) {
-                               *end = BBPOS(btree, k.k->p);
+               __for_each_btree_node(trans, iter, btree,
+                                     btree == start.btree ? start.pos : POS_MIN,
+                                     0, depth, BTREE_ITER_PREFETCH, b, ret) {
+                       mem_may_pin -= btree_buf_bytes(b);
+                       if (mem_may_pin <= 0) {
+                               c->btree_cache.pinned_nodes_end = *end =
+                                       BBPOS(btree, b->key.k.p);
                                bch2_trans_iter_exit(trans, &iter);
                                return 0;
                        }
-               } while (bch2_btree_iter_advance(&iter));
+               }
                bch2_trans_iter_exit(trans, &iter);
        }
 
-       *end = BBPOS_MAX;
        return ret;
 }
 
 static int bch2_check_extents_to_backpointers_pass(struct btree_trans *trans,
-                                                  struct bpos bucket_start,
-                                                  struct bpos bucket_end)
+                                                  struct extents_to_bp_state *s)
 {
-       struct btree_iter iter;
-       enum btree_id btree_id;
-       struct bpos last_flushed_pos = SPOS_MAX;
+       struct bch_fs *c = trans->c;
        int ret = 0;
 
-       for (btree_id = 0; btree_id < BTREE_ID_NR; btree_id++) {
-               unsigned depth = btree_type_has_ptrs(btree_id) ? 0 : 1;
-
-               bch2_trans_node_iter_init(trans, &iter, btree_id, POS_MIN, 0,
-                                         depth,
-                                         BTREE_ITER_ALL_LEVELS|
-                                         BTREE_ITER_PREFETCH);
-
-               do {
-                       ret = commit_do(trans, NULL, NULL,
-                                       BTREE_INSERT_LAZY_RW|
-                                       BTREE_INSERT_NOFAIL,
-                                       check_extent_to_backpointers(trans, &iter,
-                                                               bucket_start, bucket_end,
-                                                               &last_flushed_pos));
-                       if (ret)
-                               break;
-               } while (!bch2_btree_iter_advance(&iter));
-
-               bch2_trans_iter_exit(trans, &iter);
-
-               if (ret)
-                       break;
+       for (enum btree_id btree_id = 0;
+            btree_id < btree_id_nr_alive(c);
+            btree_id++) {
+               int level, depth = btree_type_has_ptrs(btree_id) ? 0 : 1;
 
                ret = commit_do(trans, NULL, NULL,
-                               BTREE_INSERT_LAZY_RW|
-                               BTREE_INSERT_NOFAIL,
-                               check_btree_root_to_backpointers(trans, btree_id,
-                                                       bucket_start, bucket_end,
-                                                       &last_flushed_pos));
+                               BCH_TRANS_COMMIT_no_enospc,
+                               check_btree_root_to_backpointers(trans, s, btree_id, &level));
                if (ret)
-                       break;
-       }
-       return ret;
-}
-
-static struct bpos bucket_pos_to_bp_safe(const struct bch_fs *c,
-                                        struct bpos bucket)
-{
-       return bch2_dev_exists2(c, bucket.inode)
-               ? bucket_pos_to_bp(c, bucket, 0)
-               : bucket;
-}
-
-int bch2_get_alloc_in_memory_pos(struct btree_trans *trans,
-                                struct bpos start, struct bpos *end)
-{
-       struct btree_iter alloc_iter;
-       struct btree_iter bp_iter;
-       struct bkey_s_c alloc_k, bp_k;
-       size_t btree_nodes = btree_nodes_fit_in_ram(trans->c);
-       bool alloc_end = false, bp_end = false;
-       int ret = 0;
+                       return ret;
 
-       bch2_trans_node_iter_init(trans, &alloc_iter, BTREE_ID_alloc,
-                                 start, 0, 1, 0);
-       bch2_trans_node_iter_init(trans, &bp_iter, BTREE_ID_backpointers,
-                                 bucket_pos_to_bp_safe(trans->c, start), 0, 1, 0);
-       while (1) {
-               alloc_k = !alloc_end
-                       ? __bch2_btree_iter_peek_and_restart(trans, &alloc_iter, 0)
-                       : bkey_s_c_null;
-               bp_k = !bp_end
-                       ? __bch2_btree_iter_peek_and_restart(trans, &bp_iter, 0)
-                       : bkey_s_c_null;
-
-               ret = bkey_err(alloc_k) ?: bkey_err(bp_k);
-               if ((!alloc_k.k && !bp_k.k) || ret) {
-                       *end = SPOS_MAX;
-                       break;
-               }
+               while (level >= depth) {
+                       struct btree_iter iter;
+                       bch2_trans_node_iter_init(trans, &iter, btree_id, POS_MIN, 0,
+                                                 level,
+                                                 BTREE_ITER_PREFETCH);
+                       while (1) {
+                               bch2_trans_begin(trans);
+
+                               struct bkey_s_c k = bch2_btree_iter_peek(&iter);
+                               if (!k.k)
+                                       break;
+                               ret = bkey_err(k) ?:
+                                       check_extent_to_backpointers(trans, s, btree_id, level, k) ?:
+                                       bch2_trans_commit(trans, NULL, NULL,
+                                                         BCH_TRANS_COMMIT_no_enospc);
+                               if (bch2_err_matches(ret, BCH_ERR_transaction_restart)) {
+                                       ret = 0;
+                                       continue;
+                               }
+                               if (ret)
+                                       break;
+                               if (bpos_eq(iter.pos, SPOS_MAX))
+                                       break;
+                               bch2_btree_iter_advance(&iter);
+                       }
+                       bch2_trans_iter_exit(trans, &iter);
 
-               --btree_nodes;
-               if (!btree_nodes) {
-                       *end = alloc_k.k->p;
-                       break;
-               }
+                       if (ret)
+                               return ret;
 
-               if (bpos_lt(alloc_iter.pos, SPOS_MAX) &&
-                   bpos_lt(bucket_pos_to_bp_safe(trans->c, alloc_iter.pos), bp_iter.pos)) {
-                       if (!bch2_btree_iter_advance(&alloc_iter))
-                               alloc_end = true;
-               } else {
-                       if (!bch2_btree_iter_advance(&bp_iter))
-                               bp_end = true;
+                       --level;
                }
        }
-       bch2_trans_iter_exit(trans, &bp_iter);
-       bch2_trans_iter_exit(trans, &alloc_iter);
-       return ret;
+
+       return 0;
 }
 
 int bch2_check_extents_to_backpointers(struct bch_fs *c)
 {
-       struct btree_trans trans;
-       struct bpos start = POS_MIN, end;
+       struct btree_trans *trans = bch2_trans_get(c);
+       struct extents_to_bp_state s = { .bucket_start = POS_MIN };
        int ret;
 
-       bch2_trans_init(&trans, c, 0, 0);
+       bch2_bkey_buf_init(&s.last_flushed);
+       bkey_init(&s.last_flushed.k->k);
+
        while (1) {
-               ret = bch2_get_alloc_in_memory_pos(&trans, start, &end);
+               struct bbpos end;
+               ret = bch2_get_btree_in_memory_pos(trans,
+                               BIT_ULL(BTREE_ID_backpointers),
+                               BIT_ULL(BTREE_ID_backpointers),
+                               BBPOS(BTREE_ID_backpointers, s.bucket_start), &end);
                if (ret)
                        break;
 
-               if (bpos_eq(start, POS_MIN) && !bpos_eq(end, SPOS_MAX))
+               s.bucket_end = end.pos;
+
+               if ( bpos_eq(s.bucket_start, POS_MIN) &&
+                   !bpos_eq(s.bucket_end, SPOS_MAX))
                        bch_verbose(c, "%s(): alloc info does not fit in ram, running in multiple passes with %zu nodes per pass",
                                    __func__, btree_nodes_fit_in_ram(c));
 
-               if (!bpos_eq(start, POS_MIN) || !bpos_eq(end, SPOS_MAX)) {
+               if (!bpos_eq(s.bucket_start, POS_MIN) ||
+                   !bpos_eq(s.bucket_end, SPOS_MAX)) {
                        struct printbuf buf = PRINTBUF;
 
                        prt_str(&buf, "check_extents_to_backpointers(): ");
-                       bch2_bpos_to_text(&buf, start);
+                       bch2_bpos_to_text(&buf, s.bucket_start);
                        prt_str(&buf, "-");
-                       bch2_bpos_to_text(&buf, end);
+                       bch2_bpos_to_text(&buf, s.bucket_end);
 
                        bch_verbose(c, "%s", buf.buf);
                        printbuf_exit(&buf);
                }
 
-               ret = bch2_check_extents_to_backpointers_pass(&trans, start, end);
-               if (ret || bpos_eq(end, SPOS_MAX))
+               ret = bch2_check_extents_to_backpointers_pass(trans, &s);
+               if (ret || bpos_eq(s.bucket_end, SPOS_MAX))
                        break;
 
-               start = bpos_successor(end);
+               s.bucket_start = bpos_successor(s.bucket_end);
        }
-       bch2_trans_exit(&trans);
+       bch2_trans_put(trans);
+       bch2_bkey_buf_exit(&s.last_flushed, c);
 
+       c->btree_cache.pinned_nodes_leaf_mask = 0;
+       c->btree_cache.pinned_nodes_interior_mask = 0;
+
+       bch_err_fn(c, ret);
        return ret;
 }
 
 static int check_one_backpointer(struct btree_trans *trans,
-                                struct bpos bucket,
-                                u64 *bp_offset,
                                 struct bbpos start,
-                                struct bbpos end)
+                                struct bbpos end,
+                                struct bkey_s_c_backpointer bp,
+                                struct bpos *last_flushed_pos)
 {
+       struct bch_fs *c = trans->c;
        struct btree_iter iter;
-       struct bch_backpointer bp;
-       struct bbpos pos;
+       struct bbpos pos = bp_to_bbpos(*bp.v);
        struct bkey_s_c k;
        struct printbuf buf = PRINTBUF;
        int ret;
 
-       ret = bch2_get_next_backpointer(trans, bucket, -1, bp_offset, &bp, 0);
-       if (ret || *bp_offset == U64_MAX)
-               return ret;
-
-       pos = bp_to_bbpos(bp);
        if (bbpos_cmp(pos, start) < 0 ||
            bbpos_cmp(pos, end) > 0)
                return 0;
 
-       k = bch2_backpointer_get_key(trans, &iter, bucket, *bp_offset, bp);
+       k = bch2_backpointer_get_key(trans, &iter, bp.k->p, *bp.v, 0);
        ret = bkey_err(k);
        if (ret == -BCH_ERR_backpointer_to_overwritten_btree_node)
                return 0;
        if (ret)
                return ret;
 
-       if (fsck_err_on(!k.k, trans->c,
-                       "%s backpointer points to missing extent\n%s",
-                       *bp_offset < BACKPOINTER_OFFSET_MAX ? "alloc" : "btree",
-                       (bch2_backpointer_to_text(&buf, &bp), buf.buf))) {
-               ret = bch2_backpointer_del_by_offset(trans, bucket, *bp_offset, bp);
-               if (ret == -ENOENT)
-                       bch_err(trans->c, "backpointer at %llu not found", *bp_offset);
+       if (!k.k && !bpos_eq(*last_flushed_pos, bp.k->p)) {
+               *last_flushed_pos = bp.k->p;
+               ret = bch2_btree_write_buffer_flush_sync(trans) ?:
+                       -BCH_ERR_transaction_restart_write_buffer_flush;
+               goto out;
        }
 
-       bch2_trans_iter_exit(trans, &iter);
+       if (fsck_err_on(!k.k, c,
+                       backpointer_to_missing_ptr,
+                       "backpointer for missing %s\n  %s",
+                       bp.v->level ? "btree node" : "extent",
+                       (bch2_bkey_val_to_text(&buf, c, bp.s_c), buf.buf))) {
+               ret = bch2_btree_delete_at_buffered(trans, BTREE_ID_backpointers, bp.k->p);
+               goto out;
+       }
+out:
 fsck_err:
+       bch2_trans_iter_exit(trans, &iter);
        printbuf_exit(&buf);
        return ret;
 }
@@ -976,37 +768,24 @@ static int bch2_check_backpointers_to_extents_pass(struct btree_trans *trans,
                                                   struct bbpos start,
                                                   struct bbpos end)
 {
-       struct btree_iter iter;
-       struct bkey_s_c k;
-       int ret = 0;
-
-       for_each_btree_key(trans, iter, BTREE_ID_alloc, POS_MIN,
-                          BTREE_ITER_PREFETCH, k, ret) {
-               u64 bp_offset = 0;
-
-               while (!(ret = commit_do(trans, NULL, NULL,
-                                        BTREE_INSERT_LAZY_RW|
-                                        BTREE_INSERT_NOFAIL,
-                               check_one_backpointer(trans, iter.pos, &bp_offset, start, end))) &&
-                      bp_offset < U64_MAX)
-                       bp_offset++;
+       struct bpos last_flushed_pos = SPOS_MAX;
 
-               if (ret)
-                       break;
-       }
-       bch2_trans_iter_exit(trans, &iter);
-       return ret < 0 ? ret : 0;
+       return for_each_btree_key_commit(trans, iter, BTREE_ID_backpointers,
+                                 POS_MIN, BTREE_ITER_PREFETCH, k,
+                                 NULL, NULL, BCH_TRANS_COMMIT_no_enospc,
+               check_one_backpointer(trans, start, end,
+                                     bkey_s_c_to_backpointer(k),
+                                     &last_flushed_pos));
 }
 
 int bch2_check_backpointers_to_extents(struct bch_fs *c)
 {
-       struct btree_trans trans;
+       struct btree_trans *trans = bch2_trans_get(c);
        struct bbpos start = (struct bbpos) { .btree = 0, .pos = POS_MIN, }, end;
        int ret;
 
-       bch2_trans_init(&trans, c, 0, 0);
        while (1) {
-               ret = bch2_get_btree_in_memory_pos(&trans,
+               ret = bch2_get_btree_in_memory_pos(trans,
                                                   (1U << BTREE_ID_extents)|
                                                   (1U << BTREE_ID_reflink),
                                                   ~0,
@@ -1032,13 +811,17 @@ int bch2_check_backpointers_to_extents(struct bch_fs *c)
                        printbuf_exit(&buf);
                }
 
-               ret = bch2_check_backpointers_to_extents_pass(&trans, start, end);
+               ret = bch2_check_backpointers_to_extents_pass(trans, start, end);
                if (ret || !bbpos_cmp(end, BBPOS_MAX))
                        break;
 
                start = bbpos_successor(end);
        }
-       bch2_trans_exit(&trans);
+       bch2_trans_put(trans);
+
+       c->btree_cache.pinned_nodes_leaf_mask = 0;
+       c->btree_cache.pinned_nodes_interior_mask = 0;
 
+       bch_err_fn(c, ret);
        return ret;
 }