bcachefs: check dirent->d_parent_subvol

Check that d_parent_subvol makes sense - the dirent's snapshot must be
visible in d_parent_subvol (i.e. an ancestor of d_parent_subvol's
snapshot) in order to be visible.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

diff --git a/fs/bcachefs/fsck.c b/fs/bcachefs/fsck.c
index fafce6bffff234967ebd0b1f34934e885f05601c..ff7347cc395fd8d8a8bd3da5cb480761c4afef04 100644 (file)
--- a/fs/bcachefs/fsck.c
+++ b/fs/bcachefs/fsck.c
@@ -1692,6 +1692,31 @@ fsck_err:
        return ret;
 }
 
+/* find a subvolume that's a descendent of @snapshot: */
+static int find_snapshot_subvol(struct btree_trans *trans, u32 snapshot, u32 *subvolid)
+{
+       struct btree_iter iter;
+       struct bkey_s_c k;
+       int ret;
+
+       for_each_btree_key_norestart(trans, iter, BTREE_ID_subvolumes, POS_MIN, 0, k, ret) {
+               if (k.k->type != KEY_TYPE_subvolume)
+                       continue;
+
+               struct bkey_s_c_subvolume s = bkey_s_c_to_subvolume(k);
+               if (bch2_snapshot_is_ancestor(trans->c, le32_to_cpu(s.v->snapshot), snapshot)) {
+                       bch2_trans_iter_exit(trans, &iter);
+                       *subvolid = k.k->p.offset;
+                       goto found;
+               }
+       }
+       if (!ret)
+               ret = -ENOENT;
+found:
+       bch2_trans_iter_exit(trans, &iter);
+       return ret;
+}
+
 static int check_dirent_to_subvol(struct btree_trans *trans, struct btree_iter *iter,
                                  struct bkey_s_c_dirent d)
 {
@@ -1699,18 +1724,44 @@ static int check_dirent_to_subvol(struct btree_trans *trans, struct btree_iter *
        struct bch_inode_unpacked subvol_root;
        u32 parent_subvol = le32_to_cpu(d.v->d_parent_subvol);
        u32 target_subvol = le32_to_cpu(d.v->d_child_subvol);
-       u32 target_snapshot;
-       u64 target_inum;
+       u32 target_snapshot, parent_snapshot;
+       u64 target_inum, parent_inum;
+       struct printbuf buf = PRINTBUF;
        int ret = 0;
 
+       ret = subvol_lookup(trans, parent_subvol, &parent_snapshot, &parent_inum);
+       if (ret && !bch2_err_matches(ret, ENOENT))
+               return ret;
+
+       if (fsck_err_on(ret, c, dirent_to_missing_parent_subvol,
+                       "dirent parent_subvol points to missing subvolume\n%s",
+                       (bch2_bkey_val_to_text(&buf, c, d.s_c), buf.buf)) ||
+           fsck_err_on(!ret && !bch2_snapshot_is_ancestor(c, parent_snapshot, d.k->p.snapshot),
+                       c, dirent_not_visible_in_parent_subvol,
+                       "dirent not visible in parent_subvol (not an ancestor of subvol snap %u)\n%s",
+                       parent_snapshot,
+                       (bch2_bkey_val_to_text(&buf, c, d.s_c), buf.buf))) {
+               u32 new_parent_subvol;
+               ret = find_snapshot_subvol(trans, d.k->p.snapshot, &new_parent_subvol);
+               if (ret)
+                       goto err;
+
+               struct bkey_i_dirent *new_dirent = bch2_bkey_make_mut_typed(trans, iter, &d.s_c, 0, dirent);
+               ret = PTR_ERR_OR_ZERO(new_dirent);
+               if (ret)
+                       goto err;
+
+               new_dirent->v.d_parent_subvol = cpu_to_le32(new_parent_subvol);
+       }
+
        ret = subvol_lookup(trans, target_subvol,
                            &target_snapshot, &target_inum);
        if (ret && !bch2_err_matches(ret, ENOENT))
                return ret;
 
        if (fsck_err_on(ret, c, dirent_to_missing_subvol,
-                       "dirent points to missing subvolume %u",
-                       le32_to_cpu(d.v->d_child_subvol)))
+                       "dirent points to missing subvolume\n%s",
+                       (bch2_bkey_val_to_text(&buf, c, d.s_c), buf.buf)))
                return __remove_dirent(trans, d.k->p);
 
        ret = lookup_inode(trans, target_inum,
@@ -1733,7 +1784,9 @@ static int check_dirent_to_subvol(struct btree_trans *trans, struct btree_iter *
                                  target_snapshot);
        if (ret)
                return ret;
+err:
 fsck_err:
+       printbuf_exit(&buf);
        return ret;
 }