]> git.sesse.net Git - bcachefs-tools-debian/blobdiff - libbcachefs/fsck.c
Update bcachefs sources to bed61fae3b bcachefs: Delete a faulty assertion
[bcachefs-tools-debian] / libbcachefs / fsck.c
index 12f2ef4417cb31255a405d5517ee727922ff5623..960280b706e382c75d630fd62724e11ebb209e46 100644 (file)
@@ -3,6 +3,7 @@
 #include "bcachefs.h"
 #include "bkey_buf.h"
 #include "btree_update.h"
+#include "buckets.h"
 #include "darray.h"
 #include "dirent.h"
 #include "error.h"
@@ -10,7 +11,8 @@
 #include "fsck.h"
 #include "inode.h"
 #include "keylist.h"
-#include "subvolume.h"
+#include "recovery.h"
+#include "snapshot.h"
 #include "super.h"
 #include "xattr.h"
 
@@ -31,14 +33,12 @@ static s64 bch2_count_inode_sectors(struct btree_trans *trans, u64 inum,
        u64 sectors = 0;
        int ret;
 
-       for_each_btree_key(trans, iter, BTREE_ID_extents,
-                          SPOS(inum, 0, snapshot), 0, k, ret) {
-               if (k.k->p.inode != inum)
-                       break;
-
+       for_each_btree_key_upto(trans, iter, BTREE_ID_extents,
+                               SPOS(inum, 0, snapshot),
+                               POS(inum, U64_MAX),
+                               0, k, ret)
                if (bkey_extent_is_allocation(k.k))
                        sectors += k.k->size;
-       }
 
        bch2_trans_iter_exit(trans, &iter);
 
@@ -54,11 +54,10 @@ static s64 bch2_count_subdirs(struct btree_trans *trans, u64 inum,
        u64 subdirs = 0;
        int ret;
 
-       for_each_btree_key(trans, iter, BTREE_ID_dirents,
-                          SPOS(inum, 0, snapshot), 0, k, ret) {
-               if (k.k->p.inode != inum)
-                       break;
-
+       for_each_btree_key_upto(trans, iter, BTREE_ID_dirents,
+                               SPOS(inum, 0, snapshot),
+                               POS(inum, U64_MAX),
+                               0, k, ret) {
                if (k.k->type != KEY_TYPE_dirent)
                        continue;
 
@@ -66,7 +65,6 @@ static s64 bch2_count_subdirs(struct btree_trans *trans, u64 inum,
                if (d.v->d_type == DT_DIR)
                        subdirs++;
        }
-
        bch2_trans_iter_exit(trans, &iter);
 
        return ret ?: subdirs;
@@ -75,26 +73,14 @@ static s64 bch2_count_subdirs(struct btree_trans *trans, u64 inum,
 static int __snapshot_lookup_subvol(struct btree_trans *trans, u32 snapshot,
                                    u32 *subvol)
 {
-       struct btree_iter iter;
-       struct bkey_s_c k;
-       int ret;
-
-       bch2_trans_iter_init(trans, &iter, BTREE_ID_snapshots,
-                            POS(0, snapshot), 0);
-       k = bch2_btree_iter_peek_slot(&iter);
-       ret = bkey_err(k);
-       if (ret)
-               goto err;
-
-       if (k.k->type != KEY_TYPE_snapshot) {
+       struct bch_snapshot s;
+       int ret = bch2_bkey_get_val_typed(trans, BTREE_ID_snapshots,
+                                         POS(0, snapshot), 0,
+                                         snapshot, &s);
+       if (!ret)
+               *subvol = le32_to_cpu(s.subvol);
+       else if (bch2_err_matches(ret, ENOENT))
                bch_err(trans->c, "snapshot %u not fonud", snapshot);
-               ret = -ENOENT;
-               goto err;
-       }
-
-       *subvol = le32_to_cpu(bkey_s_c_to_snapshot(k).v->subvol);
-err:
-       bch2_trans_iter_exit(trans, &iter);
        return ret;
 
 }
@@ -133,8 +119,8 @@ static int lookup_first_inode(struct btree_trans *trans, u64 inode_nr,
        if (ret)
                goto err;
 
-       if (!k.k || bkey_cmp(k.k->p, POS(0, inode_nr))) {
-               ret = -ENOENT;
+       if (!k.k || !bkey_eq(k.k->p, POS(0, inode_nr))) {
+               ret = -BCH_ERR_ENOENT_inode;
                goto err;
        }
 
@@ -155,16 +141,15 @@ static int __lookup_inode(struct btree_trans *trans, u64 inode_nr,
        struct bkey_s_c k;
        int ret;
 
-       bch2_trans_iter_init(trans, &iter, BTREE_ID_inodes,
-                            SPOS(0, inode_nr, *snapshot), 0);
-       k = bch2_btree_iter_peek_slot(&iter);
+       k = bch2_bkey_get_iter(trans, &iter, BTREE_ID_inodes,
+                              SPOS(0, inode_nr, *snapshot), 0);
        ret = bkey_err(k);
        if (ret)
                goto err;
 
        ret = bkey_is_inode(k.k)
                ? bch2_inode_unpack(k, inode)
-               : -ENOENT;
+               : -BCH_ERR_ENOENT_inode;
        if (!ret)
                *snapshot = iter.pos.snapshot;
 err:
@@ -207,17 +192,18 @@ static int __write_inode(struct btree_trans *trans,
                         struct bch_inode_unpacked *inode,
                         u32 snapshot)
 {
-       struct btree_iter iter;
-       int ret;
+       struct bkey_inode_buf *inode_p =
+               bch2_trans_kmalloc(trans, sizeof(*inode_p));
 
-       bch2_trans_iter_init(trans, &iter, BTREE_ID_inodes,
-                           SPOS(0, inode->bi_inum, snapshot),
-                           BTREE_ITER_INTENT);
+       if (IS_ERR(inode_p))
+               return PTR_ERR(inode_p);
 
-       ret   = bch2_btree_iter_traverse(&iter) ?:
-               bch2_inode_write(trans, &iter, inode);
-       bch2_trans_iter_exit(trans, &iter);
-       return ret;
+       bch2_inode_pack(inode_p, inode);
+       inode_p->inode.k.p.snapshot = snapshot;
+
+       return bch2_btree_insert_nonextent(trans, BTREE_ID_inodes,
+                               &inode_p->inode.k_i,
+                               BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE);
 }
 
 static int write_inode(struct btree_trans *trans,
@@ -234,71 +220,6 @@ static int write_inode(struct btree_trans *trans,
        return ret;
 }
 
-static int fsck_inode_rm(struct btree_trans *trans, u64 inum, u32 snapshot)
-{
-       struct bch_fs *c = trans->c;
-       struct btree_iter iter = { NULL };
-       struct bkey_i_inode_generation delete;
-       struct bch_inode_unpacked inode_u;
-       struct bkey_s_c k;
-       int ret;
-
-       do {
-               ret   = bch2_btree_delete_range_trans(trans, BTREE_ID_extents,
-                                                     SPOS(inum, 0, snapshot),
-                                                     SPOS(inum, U64_MAX, snapshot),
-                                                     0, NULL) ?:
-                       bch2_btree_delete_range_trans(trans, BTREE_ID_dirents,
-                                                     SPOS(inum, 0, snapshot),
-                                                     SPOS(inum, U64_MAX, snapshot),
-                                                     0, NULL) ?:
-                       bch2_btree_delete_range_trans(trans, BTREE_ID_xattrs,
-                                                     SPOS(inum, 0, snapshot),
-                                                     SPOS(inum, U64_MAX, snapshot),
-                                                     0, NULL);
-       } while (ret == -BCH_ERR_transaction_restart_nested);
-       if (ret)
-               goto err;
-retry:
-       bch2_trans_begin(trans);
-
-       bch2_trans_iter_init(trans, &iter, BTREE_ID_inodes,
-                            SPOS(0, inum, snapshot), BTREE_ITER_INTENT);
-       k = bch2_btree_iter_peek_slot(&iter);
-
-       ret = bkey_err(k);
-       if (ret)
-               goto err;
-
-       if (!bkey_is_inode(k.k)) {
-               bch2_fs_inconsistent(c,
-                                    "inode %llu:%u not found when deleting",
-                                    inum, snapshot);
-               ret = -EIO;
-               goto err;
-       }
-
-       bch2_inode_unpack(k, &inode_u);
-
-       /* Subvolume root? */
-       if (inode_u.bi_subvol)
-               bch_warn(c, "deleting inode %llu marked as unlinked, but also a subvolume root!?", inode_u.bi_inum);
-
-       bkey_inode_generation_init(&delete.k_i);
-       delete.k.p = iter.pos;
-       delete.v.bi_generation = cpu_to_le32(inode_u.bi_generation + 1);
-
-       ret   = bch2_trans_update(trans, &iter, &delete.k_i, 0) ?:
-               bch2_trans_commit(trans, NULL, NULL,
-                               BTREE_INSERT_NOFAIL);
-err:
-       bch2_trans_iter_exit(trans, &iter);
-       if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
-               goto retry;
-
-       return ret ?: -BCH_ERR_transaction_restart_nested;
-}
-
 static int __remove_dirent(struct btree_trans *trans, struct bpos pos)
 {
        struct bch_fs *c = trans->c;
@@ -321,7 +242,7 @@ static int __remove_dirent(struct btree_trans *trans, struct bpos pos)
        bch2_trans_iter_exit(trans, &iter);
 err:
        if (ret && !bch2_err_matches(ret, BCH_ERR_transaction_restart))
-               bch_err(c, "error from __remove_dirent(): %s", bch2_err_str(ret));
+               bch_err_fn(c, ret);
        return ret;
 }
 
@@ -351,7 +272,7 @@ static int lookup_lostfound(struct btree_trans *trans, u32 subvol,
 
        ret = __lookup_dirent(trans, root_hash_info, root_inum,
                            &lostfound_str, &inum, &d_type);
-       if (ret == -ENOENT) {
+       if (bch2_err_matches(ret, ENOENT)) {
                bch_notice(c, "creating lost+found");
                goto create_lostfound;
        }
@@ -367,7 +288,7 @@ static int lookup_lostfound(struct btree_trans *trans, u32 subvol,
        }
 
        /*
-        * The check_dirents pass has already run, dangling dirents
+        * The bch2_check_dirents pass has already run, dangling dirents
         * shouldn't exist here:
         */
        return __lookup_inode(trans, inum, lostfound, &snapshot);
@@ -456,22 +377,14 @@ static int remove_backpointer(struct btree_trans *trans,
                              struct bch_inode_unpacked *inode)
 {
        struct btree_iter iter;
-       struct bkey_s_c k;
+       struct bkey_s_c_dirent d;
        int ret;
 
-       bch2_trans_iter_init(trans, &iter, BTREE_ID_dirents,
-                            POS(inode->bi_dir, inode->bi_dir_offset), 0);
-       k = bch2_btree_iter_peek_slot(&iter);
-       ret = bkey_err(k);
-       if (ret)
-               goto out;
-       if (k.k->type != KEY_TYPE_dirent) {
-               ret = -ENOENT;
-               goto out;
-       }
-
-       ret = __remove_dirent(trans, k.k->p);
-out:
+       d = bch2_bkey_get_iter_typed(trans, &iter, BTREE_ID_dirents,
+                                    POS(inode->bi_dir, inode->bi_dir_offset), 0,
+                                    dirent);
+       ret =   bkey_err(d) ?:
+               __remove_dirent(trans, d.k->p);
        bch2_trans_iter_exit(trans, &iter);
        return ret;
 }
@@ -496,19 +409,19 @@ static inline void snapshots_seen_init(struct snapshots_seen *s)
        memset(s, 0, sizeof(*s));
 }
 
-static int snapshots_seen_add(struct bch_fs *c, struct snapshots_seen *s, u32 id)
+static int snapshots_seen_add_inorder(struct bch_fs *c, struct snapshots_seen *s, u32 id)
 {
-       struct snapshots_seen_entry *i, n = { id, id };
-       int ret;
+       struct snapshots_seen_entry *i, n = {
+               .id     = id,
+               .equiv  = bch2_snapshot_equiv(c, id),
+       };
+       int ret = 0;
 
        darray_for_each(s->ids, i) {
-               if (n.equiv < i->equiv)
+               if (i->id == id)
+                       return 0;
+               if (i->id > id)
                        break;
-
-               if (i->equiv == n.equiv) {
-                       bch_err(c, "adding duplicate snapshot in snapshots_seen_add()");
-                       return -EINVAL;
-               }
        }
 
        ret = darray_insert_item(&s->ids, i - s->ids.data, n);
@@ -527,30 +440,34 @@ static int snapshots_seen_update(struct bch_fs *c, struct snapshots_seen *s,
        };
        int ret = 0;
 
-       if (bkey_cmp(s->pos, pos))
+       if (!bkey_eq(s->pos, pos))
                s->ids.nr = 0;
 
-       pos.snapshot = n.equiv;
        s->pos = pos;
+       s->pos.snapshot = n.equiv;
 
-       darray_for_each(s->ids, i)
-               if (i->equiv == n.equiv) {
-                       if (fsck_err_on(i->id != n.id, c,
-                                       "snapshot deletion did not run correctly:\n"
-                                       "  duplicate keys in btree %s at %llu:%llu snapshots %u, %u (equiv %u)\n",
-                                       bch2_btree_ids[btree_id],
-                                       pos.inode, pos.offset,
-                                       i->id, n.id, n.equiv))
-                               return -BCH_ERR_need_snapshot_cleanup;
-
+       darray_for_each(s->ids, i) {
+               if (i->id == n.id)
                        return 0;
+
+               /*
+                * We currently don't rigorously track for snapshot cleanup
+                * needing to be run, so it shouldn't be a fsck error yet:
+                */
+               if (i->equiv == n.equiv) {
+                       bch_err(c, "snapshot deletion did not finish:\n"
+                               "  duplicate keys in btree %s at %llu:%llu snapshots %u, %u (equiv %u)\n",
+                               bch2_btree_ids[btree_id],
+                               pos.inode, pos.offset,
+                               i->id, n.id, n.equiv);
+                       return bch2_run_explicit_recovery_pass(c, BCH_RECOVERY_PASS_delete_dead_snapshots);
                }
+       }
 
        ret = darray_push(&s->ids, n);
        if (ret)
                bch_err(c, "error reallocating snapshots_seen table (size %zu)",
                        s->ids.size);
-fsck_err:
        return ret;
 }
 
@@ -564,15 +481,14 @@ static bool key_visible_in_snapshot(struct bch_fs *c, struct snapshots_seen *see
                                    u32 id, u32 ancestor)
 {
        ssize_t i;
-       u32 top = seen->ids.nr ? seen->ids.data[seen->ids.nr - 1].equiv : 0;
 
-       BUG_ON(id > ancestor);
-       BUG_ON(!bch2_snapshot_is_equiv(c, id));
-       BUG_ON(!bch2_snapshot_is_equiv(c, ancestor));
+       EBUG_ON(id > ancestor);
+       EBUG_ON(!bch2_snapshot_is_equiv(c, id));
+       EBUG_ON(!bch2_snapshot_is_equiv(c, ancestor));
 
        /* @ancestor should be the snapshot most recently added to @seen */
-       BUG_ON(ancestor != seen->pos.snapshot);
-       BUG_ON(ancestor != top);
+       EBUG_ON(ancestor != seen->pos.snapshot);
+       EBUG_ON(ancestor != seen->ids.data[seen->ids.nr - 1].equiv);
 
        if (id == ancestor)
                return true;
@@ -580,11 +496,20 @@ static bool key_visible_in_snapshot(struct bch_fs *c, struct snapshots_seen *see
        if (!bch2_snapshot_is_ancestor(c, id, ancestor))
                return false;
 
+       /*
+        * We know that @id is a descendant of @ancestor, we're checking if
+        * we've seen a key that overwrote @ancestor - i.e. also a descendent of
+        * @ascestor and with @id as a descendent.
+        *
+        * But we already know that we're scanning IDs between @id and @ancestor
+        * numerically, since snapshot ID lists are kept sorted, so if we find
+        * an id that's an ancestor of @id we're done:
+        */
+
        for (i = seen->ids.nr - 2;
             i >= 0 && seen->ids.data[i].equiv >= id;
             --i)
-               if (bch2_snapshot_is_ancestor(c, id, seen->ids.data[i].equiv) &&
-                   bch2_snapshot_is_ancestor(c, seen->ids.data[i].equiv, ancestor))
+               if (bch2_snapshot_is_ancestor(c, id, seen->ids.data[i].equiv))
                        return false;
 
        return true;
@@ -609,6 +534,20 @@ static int ref_visible(struct bch_fs *c, struct snapshots_seen *s,
                : bch2_snapshot_is_ancestor(c, src, dst);
 }
 
+static int ref_visible2(struct bch_fs *c,
+                       u32 src, struct snapshots_seen *src_seen,
+                       u32 dst, struct snapshots_seen *dst_seen)
+{
+       src = bch2_snapshot_equiv(c, src);
+       dst = bch2_snapshot_equiv(c, dst);
+
+       if (dst > src) {
+               swap(dst, src);
+               swap(dst_seen, src_seen);
+       }
+       return key_visible_in_snapshot(c, src_seen, dst, src);
+}
+
 #define for_each_visible_inode(_c, _s, _w, _snapshot, _i)                              \
        for (_i = (_w)->inodes.data; _i < (_w)->inodes.data + (_w)->inodes.nr &&        \
             (_i)->snapshot <= (_snapshot); _i++)                                       \
@@ -617,12 +556,14 @@ static int ref_visible(struct bch_fs *c, struct snapshots_seen *s,
 struct inode_walker_entry {
        struct bch_inode_unpacked inode;
        u32                     snapshot;
+       bool                    seen_this_pos;
        u64                     count;
 };
 
 struct inode_walker {
        bool                            first_this_inode;
-       u64                             cur_inum;
+       bool                            recalculate_sums;
+       struct bpos                     last_pos;
 
        DARRAY(struct inode_walker_entry) inodes;
 };
@@ -650,28 +591,21 @@ static int add_inode(struct bch_fs *c, struct inode_walker *w,
        }));
 }
 
-static int __walk_inode(struct btree_trans *trans,
-                       struct inode_walker *w, struct bpos pos)
+static int get_inodes_all_snapshots(struct btree_trans *trans,
+                                   struct inode_walker *w, u64 inum)
 {
        struct bch_fs *c = trans->c;
        struct btree_iter iter;
        struct bkey_s_c k;
        u32 restart_count = trans->restart_count;
-       unsigned i;
        int ret;
 
-       pos.snapshot = bch2_snapshot_equiv(c, pos.snapshot);
-
-       if (pos.inode == w->cur_inum) {
-               w->first_this_inode = false;
-               goto lookup_snapshot;
-       }
-
+       w->recalculate_sums = false;
        w->inodes.nr = 0;
 
-       for_each_btree_key(trans, iter, BTREE_ID_inodes, POS(0, pos.inode),
+       for_each_btree_key(trans, iter, BTREE_ID_inodes, POS(0, inum),
                           BTREE_ITER_ALL_SNAPSHOTS, k, ret) {
-               if (k.k->p.offset != pos.inode)
+               if (k.k->p.offset != inum)
                        break;
 
                if (bkey_is_inode(k.k))
@@ -682,40 +616,76 @@ static int __walk_inode(struct btree_trans *trans,
        if (ret)
                return ret;
 
-       w->cur_inum             = pos.inode;
-       w->first_this_inode     = true;
+       w->first_this_inode = true;
 
        if (trans_was_restarted(trans, restart_count))
                return -BCH_ERR_transaction_restart_nested;
 
-lookup_snapshot:
-       for (i = 0; i < w->inodes.nr; i++)
-               if (bch2_snapshot_is_ancestor(c, pos.snapshot, w->inodes.data[i].snapshot))
+       return 0;
+}
+
+static struct inode_walker_entry *
+lookup_inode_for_snapshot(struct bch_fs *c, struct inode_walker *w,
+                         u32 snapshot, bool is_whiteout)
+{
+       struct inode_walker_entry *i;
+
+       snapshot = bch2_snapshot_equiv(c, snapshot);
+
+       darray_for_each(w->inodes, i)
+               if (bch2_snapshot_is_ancestor(c, snapshot, i->snapshot))
                        goto found;
-       return INT_MAX;
+
+       return NULL;
 found:
-       BUG_ON(pos.snapshot > w->inodes.data[i].snapshot);
+       BUG_ON(snapshot > i->snapshot);
 
-       if (pos.snapshot != w->inodes.data[i].snapshot) {
-               struct inode_walker_entry e = w->inodes.data[i];
+       if (snapshot != i->snapshot && !is_whiteout) {
+               struct inode_walker_entry new = *i;
+               size_t pos;
+               int ret;
 
-               e.snapshot = pos.snapshot;
-               e.count = 0;
+               new.snapshot = snapshot;
+               new.count = 0;
 
                bch_info(c, "have key for inode %llu:%u but have inode in ancestor snapshot %u",
-                        pos.inode, pos.snapshot, w->inodes.data[i].snapshot);
+                        w->last_pos.inode, snapshot, i->snapshot);
 
-               while (i && w->inodes.data[i - 1].snapshot > pos.snapshot)
+               while (i > w->inodes.data && i[-1].snapshot > snapshot)
                        --i;
 
-               ret = darray_insert_item(&w->inodes, i, e);
+               pos = i - w->inodes.data;
+               ret = darray_insert_item(&w->inodes, pos, new);
                if (ret)
-                       return ret;
+                       return ERR_PTR(ret);
+
+               i = w->inodes.data + pos;
        }
 
        return i;
 }
 
+static struct inode_walker_entry *walk_inode(struct btree_trans *trans,
+                                            struct inode_walker *w, struct bpos pos,
+                                            bool is_whiteout)
+{
+       if (w->last_pos.inode != pos.inode) {
+               int ret = get_inodes_all_snapshots(trans, w, pos.inode);
+               if (ret)
+                       return ERR_PTR(ret);
+       } else if (bkey_cmp(w->last_pos, pos)) {
+               struct inode_walker_entry *i;
+
+               darray_for_each(w->inodes, i)
+                       i->seen_this_pos = false;
+
+       }
+
+       w->last_pos = pos;
+
+       return lookup_inode_for_snapshot(trans->c, w, pos.snapshot, is_whiteout);
+}
+
 static int __get_visible_inodes(struct btree_trans *trans,
                                struct inode_walker *w,
                                struct snapshots_seen *s,
@@ -779,12 +749,10 @@ static int hash_redo_key(struct btree_trans *trans,
        if (IS_ERR(delete))
                return PTR_ERR(delete);
 
-       tmp = bch2_trans_kmalloc(trans, bkey_bytes(k.k));
+       tmp = bch2_bkey_make_mut_noupdate(trans, k);
        if (IS_ERR(tmp))
                return PTR_ERR(tmp);
 
-       bkey_reassemble(tmp, k);
-
        bkey_init(&delete->k);
        delete->k.p = k_iter->pos;
        return  bch2_btree_iter_traverse(k_iter) ?:
@@ -823,9 +791,9 @@ static int hash_check_key(struct btree_trans *trans,
                goto bad_hash;
 
        for_each_btree_key_norestart(trans, iter, desc.btree_id,
-                                    POS(hash_k.k->p.inode, hash),
+                                    SPOS(hash_k.k->p.inode, hash, hash_k.k->p.snapshot),
                                     BTREE_ITER_SLOTS, k, ret) {
-               if (!bkey_cmp(k.k->p, hash_k.k->p))
+               if (bkey_eq(k.k->p, hash_k.k->p))
                        break;
 
                if (fsck_err_on(k.k->type == desc.key_type &&
@@ -848,16 +816,15 @@ out:
        printbuf_exit(&buf);
        return ret;
 bad_hash:
-       if (fsck_err(c, "hash table key at wrong offset: btree %s inode %llu offset %llu, "
-                    "hashed to %llu\n%s",
+       if (fsck_err(c, "hash table key at wrong offset: btree %s inode %llu offset %llu, hashed to %llu\n%s",
                     bch2_btree_ids[desc.btree_id], hash_k.k->p.inode, hash_k.k->p.offset, hash,
                     (printbuf_reset(&buf),
                      bch2_bkey_val_to_text(&buf, c, hash_k), buf.buf))) {
                ret = hash_redo_key(trans, desc, hash_info, k_iter, hash_k);
-               if (ret) {
+               if (ret && !bch2_err_matches(ret, BCH_ERR_transaction_restart))
                        bch_err(c, "hash_redo_key err %s", bch2_err_str(ret));
+               if (ret)
                        return ret;
-               }
                ret = -BCH_ERR_transaction_restart_nested;
        }
 fsck_err:
@@ -891,7 +858,7 @@ static int check_inode(struct btree_trans *trans,
         * particular is not atomic, so on the internal snapshot nodes
         * we can see inodes marked for deletion after a clean shutdown
         */
-       if (bch2_snapshot_internal_node(c, k.k->p.snapshot))
+       if (bch2_snapshot_is_internal_node(c, k.k->p.snapshot))
                return 0;
 
        if (!bkey_is_inode(k.k))
@@ -922,7 +889,7 @@ static int check_inode(struct btree_trans *trans,
                bch2_trans_unlock(trans);
                bch2_fs_lazy_rw(c);
 
-               ret = fsck_inode_rm(trans, u.bi_inum, iter->pos.snapshot);
+               ret = bch2_inode_rm_snapshot(trans, u.bi_inum, iter->pos.snapshot);
                if (ret && !bch2_err_matches(ret, BCH_ERR_transaction_restart))
                        bch_err(c, "error in fsck: error while deleting inode: %s",
                                bch2_err_str(ret));
@@ -947,11 +914,11 @@ static int check_inode(struct btree_trans *trans,
                                     iter->pos.snapshot),
                                POS(u.bi_inum, U64_MAX),
                                0, NULL);
-               if (ret) {
+               if (ret && !bch2_err_matches(ret, BCH_ERR_transaction_restart))
                        bch_err(c, "error in fsck: error truncating inode: %s",
                                bch2_err_str(ret));
+               if (ret)
                        return ret;
-               }
 
                /*
                 * We truncated without our normal sector accounting hook, just
@@ -1000,13 +967,14 @@ static int check_inode(struct btree_trans *trans,
 err:
 fsck_err:
        if (ret)
-               bch_err(c, "error from check_inode(): %s", bch2_err_str(ret));
+               bch_err_fn(c, ret);
        return ret;
 }
 
 noinline_for_stack
-static int check_inodes(struct bch_fs *c, bool full)
+int bch2_check_inodes(struct bch_fs *c)
 {
+       bool full = c->opts.fsck;
        struct btree_trans trans;
        struct btree_iter iter;
        struct bch_inode_unpacked prev = { 0 };
@@ -1026,69 +994,15 @@ static int check_inodes(struct bch_fs *c, bool full)
        bch2_trans_exit(&trans);
        snapshots_seen_exit(&s);
        if (ret)
-               bch_err(c, "error from check_inodes(): %s", bch2_err_str(ret));
-       return ret;
-}
-
-/*
- * Checking for overlapping extents needs to be reimplemented
- */
-#if 0
-static int fix_overlapping_extent(struct btree_trans *trans,
-                                      struct bkey_s_c k, struct bpos cut_at)
-{
-       struct btree_iter iter;
-       struct bkey_i *u;
-       int ret;
-
-       u = bch2_trans_kmalloc(trans, bkey_bytes(k.k));
-       ret = PTR_ERR_OR_ZERO(u);
-       if (ret)
-               return ret;
-
-       bkey_reassemble(u, k);
-       bch2_cut_front(cut_at, u);
-
-
-       /*
-        * We don't want to go through the extent_handle_overwrites path:
-        *
-        * XXX: this is going to screw up disk accounting, extent triggers
-        * assume things about extent overwrites - we should be running the
-        * triggers manually here
-        */
-       bch2_trans_iter_init(trans, &iter, BTREE_ID_extents, u->k.p,
-                            BTREE_ITER_INTENT|BTREE_ITER_NOT_EXTENTS);
-
-       BUG_ON(iter.flags & BTREE_ITER_IS_EXTENTS);
-       ret   = bch2_btree_iter_traverse(&iter) ?:
-               bch2_trans_update(trans, &iter, u, BTREE_TRIGGER_NORUN) ?:
-               bch2_trans_commit(trans, NULL, NULL,
-                                 BTREE_INSERT_NOFAIL|
-                                 BTREE_INSERT_LAZY_RW);
-       bch2_trans_iter_exit(trans, &iter);
+               bch_err_fn(c, ret);
        return ret;
 }
-#endif
 
 static struct bkey_s_c_dirent dirent_get_by_pos(struct btree_trans *trans,
                                                struct btree_iter *iter,
                                                struct bpos pos)
 {
-       struct bkey_s_c k;
-       int ret;
-
-       bch2_trans_iter_init(trans, iter, BTREE_ID_dirents, pos, 0);
-       k = bch2_btree_iter_peek_slot(iter);
-       ret = bkey_err(k);
-       if (!ret && k.k->type != KEY_TYPE_dirent)
-               ret = -ENOENT;
-       if (ret) {
-               bch2_trans_iter_exit(trans, iter);
-               return (struct bkey_s_c_dirent) { .k = ERR_PTR(ret) };
-       }
-
-       return bkey_s_c_to_dirent(k);
+       return bch2_bkey_get_iter_typed(trans, iter, BTREE_ID_dirents, pos, 0, dirent);
 }
 
 static bool inode_points_to_dirent(struct bch_inode_unpacked *inode,
@@ -1116,9 +1030,9 @@ static int inode_backpointer_exists(struct btree_trans *trans,
 
        d = dirent_get_by_pos(trans, &iter,
                        SPOS(inode->bi_dir, inode->bi_dir_offset, snapshot));
-       ret = bkey_err(d.s_c);
+       ret = bkey_err(d);
        if (ret)
-               return ret == -ENOENT ? 0 : ret;
+               return bch2_err_matches(ret, ENOENT) ? 0 : ret;
 
        ret = dirent_points_to_inode(d, inode);
        bch2_trans_iter_exit(trans, &iter);
@@ -1137,19 +1051,20 @@ static int check_i_sectors(struct btree_trans *trans, struct inode_walker *w)
                if (i->inode.bi_sectors == i->count)
                        continue;
 
-               count2 = bch2_count_inode_sectors(trans, w->cur_inum, i->snapshot);
+               count2 = bch2_count_inode_sectors(trans, w->last_pos.inode, i->snapshot);
 
-               if (i->count != count2) {
-                       bch_err(c, "fsck counted i_sectors wrong: got %llu should be %llu",
-                               i->count, count2);
+               if (w->recalculate_sums)
                        i->count = count2;
-                       if (i->inode.bi_sectors == i->count)
-                               continue;
+
+               if (i->count != count2) {
+                       bch_err(c, "fsck counted i_sectors wrong for inode %llu:%u: got %llu should be %llu",
+                               w->last_pos.inode, i->snapshot, i->count, count2);
+                       return -BCH_ERR_internal_fsck_err;
                }
 
                if (fsck_err_on(!(i->inode.bi_flags & BCH_INODE_I_SECTORS_DIRTY), c,
                            "inode %llu:%u has incorrect i_sectors: got %llu, should be %llu",
-                           w->cur_inum, i->snapshot,
+                           w->last_pos.inode, i->snapshot,
                            i->inode.bi_sectors, i->count)) {
                        i->inode.bi_sectors = i->count;
                        ret = write_inode(trans, &i->inode, i->snapshot);
@@ -1159,185 +1074,388 @@ static int check_i_sectors(struct btree_trans *trans, struct inode_walker *w)
        }
 fsck_err:
        if (ret)
-               bch_err(c, "error from check_i_sectors(): %s", bch2_err_str(ret));
+               bch_err_fn(c, ret);
        if (!ret && trans_was_restarted(trans, restart_count))
                ret = -BCH_ERR_transaction_restart_nested;
        return ret;
 }
 
-static int check_extent(struct btree_trans *trans, struct btree_iter *iter,
-                       struct bkey_s_c k,
-                       struct inode_walker *inode,
-                       struct snapshots_seen *s)
+struct extent_end {
+       u32                     snapshot;
+       u64                     offset;
+       struct snapshots_seen   seen;
+};
+
+struct extent_ends {
+       struct bpos                     last_pos;
+       DARRAY(struct extent_end)       e;
+};
+
+static void extent_ends_reset(struct extent_ends *extent_ends)
 {
-       struct bch_fs *c = trans->c;
-       struct inode_walker_entry *i;
-       struct printbuf buf = PRINTBUF;
-       struct bpos equiv;
-       int ret = 0;
+       struct extent_end *i;
 
-       ret = check_key_has_snapshot(trans, iter, k);
-       if (ret) {
-               ret = ret < 0 ? ret : 0;
-               goto out;
+       darray_for_each(extent_ends->e, i)
+               snapshots_seen_exit(&i->seen);
+
+       extent_ends->e.nr = 0;
+}
+
+static void extent_ends_exit(struct extent_ends *extent_ends)
+{
+       extent_ends_reset(extent_ends);
+       darray_exit(&extent_ends->e);
+}
+
+static void extent_ends_init(struct extent_ends *extent_ends)
+{
+       memset(extent_ends, 0, sizeof(*extent_ends));
+}
+
+static int extent_ends_at(struct bch_fs *c,
+                         struct extent_ends *extent_ends,
+                         struct snapshots_seen *seen,
+                         struct bkey_s_c k)
+{
+       struct extent_end *i, n = (struct extent_end) {
+               .offset         = k.k->p.offset,
+               .snapshot       = k.k->p.snapshot,
+               .seen           = *seen,
+       };
+
+       n.seen.ids.data = kmemdup(seen->ids.data,
+                             sizeof(seen->ids.data[0]) * seen->ids.size,
+                             GFP_KERNEL);
+       if (!n.seen.ids.data)
+               return -BCH_ERR_ENOMEM_fsck_extent_ends_at;
+
+       darray_for_each(extent_ends->e, i) {
+               if (i->snapshot == k.k->p.snapshot) {
+                       snapshots_seen_exit(&i->seen);
+                       *i = n;
+                       return 0;
+               }
+
+               if (i->snapshot >= k.k->p.snapshot)
+                       break;
        }
 
-       equiv = k.k->p;
-       equiv.snapshot = bch2_snapshot_equiv(c, k.k->p.snapshot);
+       return darray_insert_item(&extent_ends->e, i - extent_ends->e.data, n);
+}
 
-       ret = snapshots_seen_update(c, s, iter->btree_id, k.k->p);
+static int overlapping_extents_found(struct btree_trans *trans,
+                                    enum btree_id btree,
+                                    struct bpos pos1, struct snapshots_seen *pos1_seen,
+                                    struct bkey pos2,
+                                    bool *fixed,
+                                    struct extent_end *extent_end)
+{
+       struct bch_fs *c = trans->c;
+       struct printbuf buf = PRINTBUF;
+       struct btree_iter iter1, iter2 = { NULL };
+       struct bkey_s_c k1, k2;
+       int ret;
+
+       BUG_ON(bkey_le(pos1, bkey_start_pos(&pos2)));
+
+       bch2_trans_iter_init(trans, &iter1, btree, pos1,
+                            BTREE_ITER_ALL_SNAPSHOTS|
+                            BTREE_ITER_NOT_EXTENTS);
+       k1 = bch2_btree_iter_peek_upto(&iter1, POS(pos1.inode, U64_MAX));
+       ret = bkey_err(k1);
        if (ret)
                goto err;
 
-       if (k.k->type == KEY_TYPE_whiteout)
-               goto out;
+       prt_str(&buf, "\n  ");
+       bch2_bkey_val_to_text(&buf, c, k1);
 
-       if (inode->cur_inum != k.k->p.inode) {
-               ret = check_i_sectors(trans, inode);
+       if (!bpos_eq(pos1, k1.k->p)) {
+               prt_str(&buf, "\n  wanted\n  ");
+               bch2_bpos_to_text(&buf, pos1);
+               prt_str(&buf, "\n  ");
+               bch2_bkey_to_text(&buf, &pos2);
+
+               bch_err(c, "%s: error finding first overlapping extent when repairing, got%s",
+                       __func__, buf.buf);
+               ret = -BCH_ERR_internal_fsck_err;
+               goto err;
+       }
+
+       bch2_trans_copy_iter(&iter2, &iter1);
+
+       while (1) {
+               bch2_btree_iter_advance(&iter2);
+
+               k2 = bch2_btree_iter_peek_upto(&iter2, POS(pos1.inode, U64_MAX));
+               ret = bkey_err(k2);
                if (ret)
                        goto err;
+
+               if (bpos_ge(k2.k->p, pos2.p))
+                       break;
        }
 
-       BUG_ON(!iter->path->should_be_locked);
-#if 0
-       if (bkey_cmp(prev.k->k.p, bkey_start_pos(k.k)) > 0) {
-               char buf1[200];
-               char buf2[200];
+       prt_str(&buf, "\n  ");
+       bch2_bkey_val_to_text(&buf, c, k2);
+
+       if (bpos_gt(k2.k->p, pos2.p) ||
+           pos2.size != k2.k->size) {
+               bch_err(c, "%s: error finding seconding overlapping extent when repairing%s",
+                       __func__, buf.buf);
+               ret = -BCH_ERR_internal_fsck_err;
+               goto err;
+       }
 
-               bch2_bkey_val_to_text(&PBUF(buf1), c, bkey_i_to_s_c(prev.k));
-               bch2_bkey_val_to_text(&PBUF(buf2), c, k);
+       prt_printf(&buf, "\n  overwriting %s extent",
+                  pos1.snapshot >= pos2.p.snapshot ? "first" : "second");
 
-               if (fsck_err(c, "overlapping extents:\n%s\n%s", buf1, buf2)) {
-                       ret = fix_overlapping_extent(trans, k, prev.k->k.p)
-                               ?: -BCH_ERR_transaction_restart_nested;
-                       goto out;
+       if (fsck_err(c, "overlapping extents%s", buf.buf)) {
+               struct btree_iter *old_iter = &iter1;
+               struct disk_reservation res = { 0 };
+
+               if (pos1.snapshot < pos2.p.snapshot) {
+                       old_iter = &iter2;
+                       swap(k1, k2);
+               }
+
+               trans->extra_journal_res += bch2_bkey_sectors_compressed(k2);
+
+               ret =   bch2_trans_update_extent_overwrite(trans, old_iter,
+                               BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE,
+                               k1, k2) ?:
+                       bch2_trans_commit(trans, &res, NULL,
+                               BTREE_INSERT_LAZY_RW|BTREE_INSERT_NOFAIL);
+               bch2_disk_reservation_put(c, &res);
+
+               if (ret)
+                       goto err;
+
+               *fixed = true;
+
+               if (pos1.snapshot == pos2.p.snapshot) {
+                       /*
+                        * We overwrote the first extent, and did the overwrite
+                        * in the same snapshot:
+                        */
+                       extent_end->offset = bkey_start_offset(&pos2);
+               } else if (pos1.snapshot > pos2.p.snapshot) {
+                       /*
+                        * We overwrote the first extent in pos2's snapshot:
+                        */
+                       ret = snapshots_seen_add_inorder(c, pos1_seen, pos2.p.snapshot);
+               } else {
+                       /*
+                        * We overwrote the second extent - restart
+                        * check_extent() from the top:
+                        */
+                       ret = -BCH_ERR_transaction_restart_nested;
                }
        }
-#endif
-       ret = __walk_inode(trans, inode, equiv);
-       if (ret < 0)
+fsck_err:
+err:
+       bch2_trans_iter_exit(trans, &iter2);
+       bch2_trans_iter_exit(trans, &iter1);
+       printbuf_exit(&buf);
+       return ret;
+}
+
+static int check_overlapping_extents(struct btree_trans *trans,
+                             struct snapshots_seen *seen,
+                             struct extent_ends *extent_ends,
+                             struct bkey_s_c k,
+                             u32 equiv,
+                             struct btree_iter *iter,
+                             bool *fixed)
+{
+       struct bch_fs *c = trans->c;
+       struct extent_end *i;
+       int ret = 0;
+
+       /* transaction restart, running again */
+       if (bpos_eq(extent_ends->last_pos, k.k->p))
+               return 0;
+
+       if (extent_ends->last_pos.inode != k.k->p.inode)
+               extent_ends_reset(extent_ends);
+
+       darray_for_each(extent_ends->e, i) {
+               if (i->offset <= bkey_start_offset(k.k))
+                       continue;
+
+               if (!ref_visible2(c,
+                                 k.k->p.snapshot, seen,
+                                 i->snapshot, &i->seen))
+                       continue;
+
+               ret = overlapping_extents_found(trans, iter->btree_id,
+                                               SPOS(iter->pos.inode,
+                                                    i->offset,
+                                                    i->snapshot),
+                                               &i->seen,
+                                               *k.k, fixed, i);
+               if (ret)
+                       goto err;
+       }
+
+       ret = extent_ends_at(c, extent_ends, seen, k);
+       if (ret)
                goto err;
 
-       if (fsck_err_on(ret == INT_MAX, c,
-                       "extent in missing inode:\n  %s",
-                       (printbuf_reset(&buf),
-                        bch2_bkey_val_to_text(&buf, c, k), buf.buf))) {
-               ret = bch2_btree_delete_at(trans, iter,
-                                           BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE);
+       extent_ends->last_pos = k.k->p;
+err:
+       return ret;
+}
+
+static int check_extent(struct btree_trans *trans, struct btree_iter *iter,
+                       struct bkey_s_c k,
+                       struct inode_walker *inode,
+                       struct snapshots_seen *s,
+                       struct extent_ends *extent_ends)
+{
+       struct bch_fs *c = trans->c;
+       struct inode_walker_entry *i;
+       struct printbuf buf = PRINTBUF;
+       struct bpos equiv = k.k->p;
+       int ret = 0;
+
+       equiv.snapshot = bch2_snapshot_equiv(c, k.k->p.snapshot);
+
+       ret = check_key_has_snapshot(trans, iter, k);
+       if (ret) {
+               ret = ret < 0 ? ret : 0;
                goto out;
        }
 
-       if (ret == INT_MAX) {
-               ret = 0;
-               goto out;
+       if (inode->last_pos.inode != k.k->p.inode) {
+               ret = check_i_sectors(trans, inode);
+               if (ret)
+                       goto err;
        }
 
-       i = inode->inodes.data + ret;
-       ret = 0;
+       i = walk_inode(trans, inode, equiv, k.k->type == KEY_TYPE_whiteout);
+       ret = PTR_ERR_OR_ZERO(i);
+       if (ret)
+               goto err;
 
-       if (fsck_err_on(!S_ISREG(i->inode.bi_mode) &&
-                       !S_ISLNK(i->inode.bi_mode), c,
-                       "extent in non regular inode mode %o:\n  %s",
-                       i->inode.bi_mode,
-                       (printbuf_reset(&buf),
-                        bch2_bkey_val_to_text(&buf, c, k), buf.buf))) {
-               ret = bch2_btree_delete_at(trans, iter,
-                                           BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE);
-               goto out;
+       ret = snapshots_seen_update(c, s, iter->btree_id, k.k->p);
+       if (ret)
+               goto err;
+
+       if (k.k->type != KEY_TYPE_whiteout) {
+               if (fsck_err_on(!i, c,
+                               "extent in missing inode:\n  %s",
+                               (printbuf_reset(&buf),
+                                bch2_bkey_val_to_text(&buf, c, k), buf.buf)))
+                       goto delete;
+
+               if (fsck_err_on(i &&
+                               !S_ISREG(i->inode.bi_mode) &&
+                               !S_ISLNK(i->inode.bi_mode), c,
+                               "extent in non regular inode mode %o:\n  %s",
+                               i->inode.bi_mode,
+                               (printbuf_reset(&buf),
+                                bch2_bkey_val_to_text(&buf, c, k), buf.buf)))
+                       goto delete;
+
+               ret = check_overlapping_extents(trans, s, extent_ends, k,
+                                               equiv.snapshot, iter,
+                                               &inode->recalculate_sums);
+               if (ret)
+                       goto err;
        }
 
        /*
-        * Check inodes in reverse order, from oldest snapshots to newest, so
-        * that we emit the fewest number of whiteouts necessary:
+        * Check inodes in reverse order, from oldest snapshots to newest,
+        * starting from the inode that matches this extent's snapshot. If we
+        * didn't have one, iterate over all inodes:
         */
-       for (i = inode->inodes.data + inode->inodes.nr - 1;
-            i >= inode->inodes.data;
+       if (!i)
+               i = inode->inodes.data + inode->inodes.nr - 1;
+
+       for (;
+            inode->inodes.data && i >= inode->inodes.data;
             --i) {
                if (i->snapshot > equiv.snapshot ||
                    !key_visible_in_snapshot(c, s, i->snapshot, equiv.snapshot))
                        continue;
 
-               if (fsck_err_on(!(i->inode.bi_flags & BCH_INODE_I_SIZE_DIRTY) &&
-                               k.k->type != KEY_TYPE_reservation &&
-                               k.k->p.offset > round_up(i->inode.bi_size, block_bytes(c)) >> 9, c,
-                               "extent type past end of inode %llu:%u, i_size %llu\n  %s",
-                               i->inode.bi_inum, i->snapshot, i->inode.bi_size,
-                               (bch2_bkey_val_to_text(&buf, c, k), buf.buf))) {
-                       struct btree_iter iter2;
-
-                       bch2_trans_copy_iter(&iter2, iter);
-                       bch2_btree_iter_set_snapshot(&iter2, i->snapshot);
-                       ret =   bch2_btree_iter_traverse(&iter2) ?:
-                               bch2_btree_delete_at(trans, &iter2,
-                                       BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE);
-                       bch2_trans_iter_exit(trans, &iter2);
-                       if (ret)
-                               goto err;
-
-                       if (i->snapshot != equiv.snapshot) {
-                               ret = snapshots_seen_add(c, s, i->snapshot);
+               if (k.k->type != KEY_TYPE_whiteout) {
+                       if (fsck_err_on(!(i->inode.bi_flags & BCH_INODE_I_SIZE_DIRTY) &&
+                                       k.k->p.offset > round_up(i->inode.bi_size, block_bytes(c)) >> 9 &&
+                                       !bkey_extent_is_reservation(k), c,
+                                       "extent type past end of inode %llu:%u, i_size %llu\n  %s",
+                                       i->inode.bi_inum, i->snapshot, i->inode.bi_size,
+                                       (bch2_bkey_val_to_text(&buf, c, k), buf.buf))) {
+                               struct btree_iter iter2;
+
+                               bch2_trans_copy_iter(&iter2, iter);
+                               bch2_btree_iter_set_snapshot(&iter2, i->snapshot);
+                               ret =   bch2_btree_iter_traverse(&iter2) ?:
+                                       bch2_btree_delete_at(trans, &iter2,
+                                               BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE);
+                               bch2_trans_iter_exit(trans, &iter2);
                                if (ret)
                                        goto err;
+
+                               iter->k.type = KEY_TYPE_whiteout;
                        }
-               }
-       }
 
-       if (bkey_extent_is_allocation(k.k))
-               for_each_visible_inode(c, s, inode, equiv.snapshot, i)
-                       i->count += k.k->size;
-#if 0
-       bch2_bkey_buf_reassemble(&prev, c, k);
-#endif
+                       if (bkey_extent_is_allocation(k.k))
+                               i->count += k.k->size;
+               }
 
+               i->seen_this_pos = true;
+       }
 out:
 err:
 fsck_err:
        printbuf_exit(&buf);
 
        if (ret && !bch2_err_matches(ret, BCH_ERR_transaction_restart))
-               bch_err(c, "error from check_extent(): %s", bch2_err_str(ret));
+               bch_err_fn(c, ret);
        return ret;
+delete:
+       ret = bch2_btree_delete_at(trans, iter, BTREE_UPDATE_INTERNAL_SNAPSHOT_NODE);
+       goto out;
 }
 
 /*
  * Walk extents: verify that extents have a corresponding S_ISREG inode, and
  * that i_size an i_sectors are consistent
  */
-noinline_for_stack
-static int check_extents(struct bch_fs *c)
+int bch2_check_extents(struct bch_fs *c)
 {
        struct inode_walker w = inode_walker_init();
        struct snapshots_seen s;
        struct btree_trans trans;
        struct btree_iter iter;
        struct bkey_s_c k;
+       struct extent_ends extent_ends;
+       struct disk_reservation res = { 0 };
        int ret = 0;
 
-#if 0
-       struct bkey_buf prev;
-       bch2_bkey_buf_init(&prev);
-       prev.k->k = KEY(0, 0, 0);
-#endif
        snapshots_seen_init(&s);
-       bch2_trans_init(&trans, c, BTREE_ITER_MAX, 0);
-
-       bch_verbose(c, "checking extents");
+       extent_ends_init(&extent_ends);
+       bch2_trans_init(&trans, c, BTREE_ITER_MAX, 4096);
 
        ret = for_each_btree_key_commit(&trans, iter, BTREE_ID_extents,
                        POS(BCACHEFS_ROOT_INO, 0),
                        BTREE_ITER_PREFETCH|BTREE_ITER_ALL_SNAPSHOTS, k,
-                       NULL, NULL,
-                       BTREE_INSERT_LAZY_RW|BTREE_INSERT_NOFAIL,
-               check_extent(&trans, &iter, k, &w, &s));
-#if 0
-       bch2_bkey_buf_exit(&prev, c);
-#endif
+                       &res, NULL,
+                       BTREE_INSERT_LAZY_RW|BTREE_INSERT_NOFAIL, ({
+               bch2_disk_reservation_put(c, &res);
+               check_extent(&trans, &iter, k, &w, &s, &extent_ends);
+       })) ?:
+       check_i_sectors(&trans, &w);
+
+       bch2_disk_reservation_put(c, &res);
+       extent_ends_exit(&extent_ends);
        inode_walker_exit(&w);
        bch2_trans_exit(&trans);
        snapshots_seen_exit(&s);
 
        if (ret)
-               bch_err(c, "error from check_extents(): %s", bch2_err_str(ret));
+               bch_err_fn(c, ret);
        return ret;
 }
 
@@ -1353,7 +1471,7 @@ static int check_subdir_count(struct btree_trans *trans, struct inode_walker *w)
                if (i->inode.bi_nlink == i->count)
                        continue;
 
-               count2 = bch2_count_subdirs(trans, w->cur_inum, i->snapshot);
+               count2 = bch2_count_subdirs(trans, w->last_pos.inode, i->snapshot);
                if (count2 < 0)
                        return count2;
 
@@ -1367,7 +1485,7 @@ static int check_subdir_count(struct btree_trans *trans, struct inode_walker *w)
 
                if (fsck_err_on(i->inode.bi_nlink != i->count, c,
                                "directory %llu:%u with wrong i_nlink: got %u, should be %llu",
-                               w->cur_inum, i->snapshot, i->inode.bi_nlink, i->count)) {
+                               w->last_pos.inode, i->snapshot, i->inode.bi_nlink, i->count)) {
                        i->inode.bi_nlink = i->count;
                        ret = write_inode(trans, &i->inode, i->snapshot);
                        if (ret)
@@ -1376,7 +1494,7 @@ static int check_subdir_count(struct btree_trans *trans, struct inode_walker *w)
        }
 fsck_err:
        if (ret)
-               bch_err(c, "error from check_subdir_count(): %s", bch2_err_str(ret));
+               bch_err_fn(c, ret);
        if (!ret && trans_was_restarted(trans, restart_count))
                ret = -BCH_ERR_transaction_restart_nested;
        return ret;
@@ -1497,7 +1615,7 @@ fsck_err:
        printbuf_exit(&buf);
 
        if (ret && !bch2_err_matches(ret, BCH_ERR_transaction_restart))
-               bch_err(c, "error from check_target(): %s", bch2_err_str(ret));
+               bch_err_fn(c, ret);
        return ret;
 }
 
@@ -1531,7 +1649,7 @@ static int check_dirent(struct btree_trans *trans, struct btree_iter *iter,
        if (k.k->type == KEY_TYPE_whiteout)
                goto out;
 
-       if (dir->cur_inum != k.k->p.inode) {
+       if (dir->last_pos.inode != k.k->p.inode) {
                ret = check_subdir_count(trans, dir);
                if (ret)
                        goto err;
@@ -1539,11 +1657,16 @@ static int check_dirent(struct btree_trans *trans, struct btree_iter *iter,
 
        BUG_ON(!iter->path->should_be_locked);
 
-       ret = __walk_inode(trans, dir, equiv);
+       i = walk_inode(trans, dir, equiv, k.k->type == KEY_TYPE_whiteout);
+       ret = PTR_ERR_OR_ZERO(i);
        if (ret < 0)
                goto err;
 
-       if (fsck_err_on(ret == INT_MAX, c,
+       if (dir->first_this_inode && dir->inodes.nr)
+               *hash_info = bch2_hash_info_init(c, &dir->inodes.data[0].inode);
+       dir->first_this_inode = false;
+
+       if (fsck_err_on(!i, c,
                        "dirent in nonexisting directory:\n%s",
                        (printbuf_reset(&buf),
                         bch2_bkey_val_to_text(&buf, c, k), buf.buf))) {
@@ -1552,13 +1675,8 @@ static int check_dirent(struct btree_trans *trans, struct btree_iter *iter,
                goto out;
        }
 
-       if (ret == INT_MAX) {
-               ret = 0;
+       if (!i)
                goto out;
-       }
-
-       i = dir->inodes.data + ret;
-       ret = 0;
 
        if (fsck_err_on(!S_ISDIR(i->inode.bi_mode), c,
                        "dirent in non directory inode type %s:\n%s",
@@ -1569,11 +1687,7 @@ static int check_dirent(struct btree_trans *trans, struct btree_iter *iter,
                goto out;
        }
 
-       if (dir->first_this_inode)
-               *hash_info = bch2_hash_info_init(c, &dir->inodes.data[0].inode);
-
-       ret = hash_check_key(trans, bch2_dirent_hash_desc,
-                            hash_info, iter, k);
+       ret = hash_check_key(trans, bch2_dirent_hash_desc, hash_info, iter, k);
        if (ret < 0)
                goto err;
        if (ret) {
@@ -1595,19 +1709,19 @@ static int check_dirent(struct btree_trans *trans, struct btree_iter *iter,
 
                ret = __subvol_lookup(trans, target_subvol,
                                      &target_snapshot, &target_inum);
-               if (ret && ret != -ENOENT)
+               if (ret && !bch2_err_matches(ret, ENOENT))
                        goto err;
 
                if (fsck_err_on(ret, c,
-                               "dirent points to missing subvolume %llu",
-                               le64_to_cpu(d.v->d_child_subvol))) {
+                               "dirent points to missing subvolume %u",
+                               le32_to_cpu(d.v->d_child_subvol))) {
                        ret = __remove_dirent(trans, d.k->p);
                        goto err;
                }
 
                ret = __lookup_inode(trans, target_inum,
                                   &subvol_root, &target_snapshot);
-               if (ret && ret != -ENOENT)
+               if (ret && !bch2_err_matches(ret, ENOENT))
                        goto err;
 
                if (fsck_err_on(ret, c,
@@ -1667,7 +1781,7 @@ fsck_err:
        printbuf_exit(&buf);
 
        if (ret && !bch2_err_matches(ret, BCH_ERR_transaction_restart))
-               bch_err(c, "error from check_dirent(): %s", bch2_err_str(ret));
+               bch_err_fn(c, ret);
        return ret;
 }
 
@@ -1675,8 +1789,7 @@ fsck_err:
  * Walk dirents: verify that they all have a corresponding S_ISDIR inode,
  * validate d_type
  */
-noinline_for_stack
-static int check_dirents(struct bch_fs *c)
+int bch2_check_dirents(struct bch_fs *c)
 {
        struct inode_walker dir = inode_walker_init();
        struct inode_walker target = inode_walker_init();
@@ -1687,8 +1800,6 @@ static int check_dirents(struct bch_fs *c)
        struct bkey_s_c k;
        int ret = 0;
 
-       bch_verbose(c, "checking dirents");
-
        snapshots_seen_init(&s);
        bch2_trans_init(&trans, c, BTREE_ITER_MAX, 0);
 
@@ -1706,7 +1817,7 @@ static int check_dirents(struct bch_fs *c)
        inode_walker_exit(&target);
 
        if (ret)
-               bch_err(c, "error from check_dirents(): %s", bch2_err_str(ret));
+               bch_err_fn(c, ret);
        return ret;
 }
 
@@ -1716,41 +1827,41 @@ static int check_xattr(struct btree_trans *trans, struct btree_iter *iter,
                       struct inode_walker *inode)
 {
        struct bch_fs *c = trans->c;
+       struct inode_walker_entry *i;
        int ret;
 
        ret = check_key_has_snapshot(trans, iter, k);
        if (ret)
                return ret;
 
-       ret = __walk_inode(trans, inode, k.k->p);
-       if (ret < 0)
+       i = walk_inode(trans, inode, k.k->p, k.k->type == KEY_TYPE_whiteout);
+       ret = PTR_ERR_OR_ZERO(i);
+       if (ret)
                return ret;
 
-       if (fsck_err_on(ret == INT_MAX, c,
+       if (inode->first_this_inode && inode->inodes.nr)
+               *hash_info = bch2_hash_info_init(c, &inode->inodes.data[0].inode);
+       inode->first_this_inode = false;
+
+       if (fsck_err_on(!i, c,
                        "xattr for missing inode %llu",
                        k.k->p.inode))
                return bch2_btree_delete_at(trans, iter, 0);
 
-       if (ret == INT_MAX)
+       if (!i)
                return 0;
 
-       ret = 0;
-
-       if (inode->first_this_inode)
-               *hash_info = bch2_hash_info_init(c, &inode->inodes.data[0].inode);
-
        ret = hash_check_key(trans, bch2_xattr_hash_desc, hash_info, iter, k);
 fsck_err:
        if (ret && !bch2_err_matches(ret, BCH_ERR_transaction_restart))
-               bch_err(c, "error from check_xattr(): %s", bch2_err_str(ret));
+               bch_err_fn(c, ret);
        return ret;
 }
 
 /*
  * Walk xattrs: verify that they all have a corresponding inode
  */
-noinline_for_stack
-static int check_xattrs(struct bch_fs *c)
+int bch2_check_xattrs(struct bch_fs *c)
 {
        struct inode_walker inode = inode_walker_init();
        struct bch_hash_info hash_info;
@@ -1759,8 +1870,6 @@ static int check_xattrs(struct bch_fs *c)
        struct bkey_s_c k;
        int ret = 0;
 
-       bch_verbose(c, "checking xattrs");
-
        bch2_trans_init(&trans, c, BTREE_ITER_MAX, 0);
 
        ret = for_each_btree_key_commit(&trans, iter, BTREE_ID_xattrs,
@@ -1774,7 +1883,7 @@ static int check_xattrs(struct bch_fs *c)
        bch2_trans_exit(&trans);
 
        if (ret)
-               bch_err(c, "error from check_xattrs(): %s", bch2_err_str(ret));
+               bch_err_fn(c, ret);
        return ret;
 }
 
@@ -1787,7 +1896,7 @@ static int check_root_trans(struct btree_trans *trans)
        int ret;
 
        ret = __subvol_lookup(trans, BCACHEFS_ROOT_SUBVOL, &snapshot, &inum);
-       if (ret && ret != -ENOENT)
+       if (ret && !bch2_err_matches(ret, ENOENT))
                return ret;
 
        if (mustfix_fsck_err_on(ret, c, "root subvol missing")) {
@@ -1804,7 +1913,8 @@ static int check_root_trans(struct btree_trans *trans)
                ret = commit_do(trans, NULL, NULL,
                                      BTREE_INSERT_NOFAIL|
                                      BTREE_INSERT_LAZY_RW,
-                       __bch2_btree_insert(trans, BTREE_ID_subvolumes, &root_subvol.k_i));
+                       __bch2_btree_insert(trans, BTREE_ID_subvolumes,
+                                           &root_subvol.k_i, 0));
                if (ret) {
                        bch_err(c, "error writing root subvol: %s", bch2_err_str(ret));
                        goto err;
@@ -1813,7 +1923,7 @@ static int check_root_trans(struct btree_trans *trans)
        }
 
        ret = __lookup_inode(trans, BCACHEFS_ROOT_INO, &root_inode, &snapshot);
-       if (ret && ret != -ENOENT)
+       if (ret && !bch2_err_matches(ret, ENOENT))
                return ret;
 
        if (mustfix_fsck_err_on(ret, c, "root directory missing") ||
@@ -1833,15 +1943,18 @@ fsck_err:
 }
 
 /* Get root directory, create if it doesn't exist: */
-noinline_for_stack
-static int check_root(struct bch_fs *c)
+int bch2_check_root(struct bch_fs *c)
 {
-       bch_verbose(c, "checking root directory");
+       int ret;
 
-       return bch2_trans_do(c, NULL, NULL,
+       ret = bch2_trans_do(c, NULL, NULL,
                             BTREE_INSERT_NOFAIL|
                             BTREE_INSERT_LAZY_RW,
                check_root_trans(&trans));
+
+       if (ret)
+               bch_err_fn(c, ret);
+       return ret;
 }
 
 struct pathbuf_entry {
@@ -1912,15 +2025,15 @@ static int check_path(struct btree_trans *trans,
                        PTR_ERR_OR_ZERO((d = dirent_get_by_pos(trans, &dirent_iter,
                                          SPOS(inode->bi_dir, inode->bi_dir_offset,
                                               parent_snapshot))).k));
-               if (ret && ret != -ENOENT)
+               if (ret && !bch2_err_matches(ret, ENOENT))
                        break;
 
                if (!ret && !dirent_points_to_inode(d, inode)) {
                        bch2_trans_iter_exit(trans, &dirent_iter);
-                       ret = -ENOENT;
+                       ret = -BCH_ERR_ENOENT_dirent_doesnt_match_inode;
                }
 
-               if (ret == -ENOENT) {
+               if (bch2_err_matches(ret, ENOENT)) {
                        if (fsck_err(c,  "unreachable inode %llu:%u, type %s nlink %u backptr %llu:%llu",
                                     inode->bi_inum, snapshot,
                                     bch2_d_type_str(inode_d_type(inode)),
@@ -1978,17 +2091,16 @@ static int check_path(struct btree_trans *trans,
        }
 fsck_err:
        if (ret)
-               bch_err(c, "%s: err %s", __func__, bch2_err_str(ret));
+               bch_err_fn(c, ret);
        return ret;
 }
 
 /*
  * Check for unreachable inodes, as well as loops in the directory structure:
- * After check_dirents(), if an inode backpointer doesn't exist that means it's
+ * After bch2_check_dirents(), if an inode backpointer doesn't exist that means it's
  * unreachable:
  */
-noinline_for_stack
-static int check_directory_structure(struct bch_fs *c)
+int bch2_check_directory_structure(struct bch_fs *c)
 {
        struct btree_trans trans;
        struct btree_iter iter;
@@ -2021,13 +2133,16 @@ static int check_directory_structure(struct bch_fs *c)
                        break;
        }
        bch2_trans_iter_exit(&trans, &iter);
-
+       bch2_trans_exit(&trans);
        darray_exit(&path);
 
-       bch2_trans_exit(&trans);
+       if (ret)
+               bch_err_fn(c, ret);
        return ret;
 }
 
+/* check_nlink pass: */
+
 struct nlink_table {
        size_t          nr;
        size_t          size;
@@ -2044,11 +2159,12 @@ static int add_nlink(struct bch_fs *c, struct nlink_table *t,
 {
        if (t->nr == t->size) {
                size_t new_size = max_t(size_t, 128UL, t->size * 2);
-               void *d = kvmalloc(new_size * sizeof(t->d[0]), GFP_KERNEL);
+               void *d = kvmalloc_array(new_size, sizeof(t->d[0]), GFP_KERNEL);
+
                if (!d) {
                        bch_err(c, "fsck: error allocating memory for nlink_table, size %zu",
                                new_size);
-                       return -ENOMEM;
+                       return -BCH_ERR_ENOMEM_fsck_add_nlink;
                }
 
                if (t->d)
@@ -2131,7 +2247,7 @@ static int check_nlinks_find_hardlinks(struct bch_fs *c,
                 * Backpointer and directory structure checks are sufficient for
                 * directories, since they can't have hardlinks:
                 */
-               if (S_ISDIR(le16_to_cpu(u.bi_mode)))
+               if (S_ISDIR(u.bi_mode))
                        continue;
 
                if (!u.bi_nlink)
@@ -2217,7 +2333,7 @@ static int check_nlinks_update_inode(struct btree_trans *trans, struct btree_ite
 
        BUG_ON(bch2_inode_unpack(k, &u));
 
-       if (S_ISDIR(le16_to_cpu(u.bi_mode)))
+       if (S_ISDIR(u.bi_mode))
                return 0;
 
        if (!u.bi_nlink)
@@ -2269,15 +2385,12 @@ static int check_nlinks_update_hardlinks(struct bch_fs *c,
        return 0;
 }
 
-noinline_for_stack
-static int check_nlinks(struct bch_fs *c)
+int bch2_check_nlinks(struct bch_fs *c)
 {
        struct nlink_table links = { 0 };
        u64 this_iter_range_start, next_iter_range_start = 0;
        int ret = 0;
 
-       bch_verbose(c, "checking inode nlinks");
-
        do {
                this_iter_range_start = next_iter_range_start;
                next_iter_range_start = U64_MAX;
@@ -2303,6 +2416,8 @@ static int check_nlinks(struct bch_fs *c)
 
        kvfree(links.d);
 
+       if (ret)
+               bch_err_fn(c, ret);
        return ret;
 }
 
@@ -2333,10 +2448,8 @@ static int fix_reflink_p_key(struct btree_trans *trans, struct btree_iter *iter,
        return bch2_trans_update(trans, iter, &u->k_i, BTREE_TRIGGER_NORUN);
 }
 
-noinline_for_stack
-static int fix_reflink_p(struct bch_fs *c)
+int bch2_fix_reflink_p(struct bch_fs *c)
 {
-       struct btree_trans trans;
        struct btree_iter iter;
        struct bkey_s_c k;
        int ret;
@@ -2344,52 +2457,15 @@ static int fix_reflink_p(struct bch_fs *c)
        if (c->sb.version >= bcachefs_metadata_version_reflink_p_fix)
                return 0;
 
-       bch_verbose(c, "fixing reflink_p keys");
-
-       bch2_trans_init(&trans, c, BTREE_ITER_MAX, 0);
-
-       ret = for_each_btree_key_commit(&trans, iter,
-                       BTREE_ID_extents, POS_MIN,
-                       BTREE_ITER_INTENT|BTREE_ITER_PREFETCH|BTREE_ITER_ALL_SNAPSHOTS, k,
-                       NULL, NULL, BTREE_INSERT_NOFAIL|BTREE_INSERT_LAZY_RW,
-               fix_reflink_p_key(&trans, &iter, k));
-
-       bch2_trans_exit(&trans);
-       return ret;
-}
-
-/*
- * Checks for inconsistencies that shouldn't happen, unless we have a bug.
- * Doesn't fix them yet, mainly because they haven't yet been observed:
- */
-int bch2_fsck_full(struct bch_fs *c)
-{
-       int ret;
-again:
-       ret =   bch2_fs_check_snapshots(c) ?:
-               bch2_fs_check_subvols(c) ?:
-               bch2_delete_dead_snapshots(c) ?:
-               check_inodes(c, true) ?:
-               check_extents(c) ?:
-               check_dirents(c) ?:
-               check_xattrs(c) ?:
-               check_root(c) ?:
-               check_directory_structure(c) ?:
-               check_nlinks(c) ?:
-               fix_reflink_p(c);
-
-       if (bch2_err_matches(ret, BCH_ERR_need_snapshot_cleanup)) {
-               set_bit(BCH_FS_HAVE_DELETED_SNAPSHOTS, &c->flags);
-               goto again;
-       }
+       ret = bch2_trans_run(c,
+               for_each_btree_key_commit(&trans, iter,
+                               BTREE_ID_extents, POS_MIN,
+                               BTREE_ITER_INTENT|BTREE_ITER_PREFETCH|
+                               BTREE_ITER_ALL_SNAPSHOTS, k,
+                               NULL, NULL, BTREE_INSERT_NOFAIL|BTREE_INSERT_LAZY_RW,
+                       fix_reflink_p_key(&trans, &iter, k)));
 
+       if (ret)
+               bch_err_fn(c, ret);
        return ret;
 }
-
-int bch2_fsck_walk_inodes_only(struct bch_fs *c)
-{
-       return  bch2_fs_check_snapshots(c) ?:
-               bch2_fs_check_subvols(c) ?:
-               bch2_delete_dead_snapshots(c) ?:
-               check_inodes(c, false);
-}