bcachefs: check_inode_dirent_inode()

check that if an inode has a backpointer, the dirent it points to points
back to it.

We do this in check_dirent_inode_dirent(), but only for inodes that have
dirents that point to them - we also have to do the check starting from
the inode to catch inodes that don't have dirents that point to them.

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

diff --git a/fs/bcachefs/fsck.c b/fs/bcachefs/fsck.c
index 120be62331c94e57bb22f41e335bae370125618f..830b06d1038c2814630ccfa5271a951ca07b901f 100644 (file)
--- a/fs/bcachefs/fsck.c
+++ b/fs/bcachefs/fsck.c
@@ -767,6 +767,43 @@ fsck_err:
        goto out;
 }
 
+static struct bkey_s_c_dirent dirent_get_by_pos(struct btree_trans *trans,
+                                               struct btree_iter *iter,
+                                               struct bpos pos)
+{
+       return bch2_bkey_get_iter_typed(trans, iter, BTREE_ID_dirents, pos, 0, dirent);
+}
+
+static struct bkey_s_c_dirent inode_get_dirent(struct btree_trans *trans,
+                                              struct btree_iter *iter,
+                                              struct bch_inode_unpacked *inode,
+                                              u32 *snapshot)
+{
+       if (inode->bi_subvol) {
+               u64 inum;
+               int ret = subvol_lookup(trans, inode->bi_parent_subvol, snapshot, &inum);
+               if (ret)
+                       return ((struct bkey_s_c_dirent) { .k = ERR_PTR(ret) });
+       }
+
+       return dirent_get_by_pos(trans, iter, SPOS(inode->bi_dir, inode->bi_dir_offset, *snapshot));
+}
+
+static bool inode_points_to_dirent(struct bch_inode_unpacked *inode,
+                                  struct bkey_s_c_dirent d)
+{
+       return  inode->bi_dir           == d.k->p.inode &&
+               inode->bi_dir_offset    == d.k->p.offset;
+}
+
+static bool dirent_points_to_inode(struct bkey_s_c_dirent d,
+                                  struct bch_inode_unpacked *inode)
+{
+       return d.v->d_type == DT_SUBVOL
+               ? le32_to_cpu(d.v->d_child_subvol)      == inode->bi_subvol
+               : le64_to_cpu(d.v->d_inum)              == inode->bi_inum;
+}
+
 static int check_inode_deleted_list(struct btree_trans *trans, struct bpos p)
 {
        struct btree_iter iter;
@@ -776,6 +813,49 @@ static int check_inode_deleted_list(struct btree_trans *trans, struct bpos p)
        return ret;
 }
 
+static int check_inode_dirent_inode(struct btree_trans *trans, struct bkey_s_c inode_k,
+                                   struct bch_inode_unpacked *inode,
+                                   u32 inode_snapshot, bool *write_inode)
+{
+       struct bch_fs *c = trans->c;
+       struct printbuf buf = PRINTBUF;
+
+       struct btree_iter dirent_iter = {};
+       struct bkey_s_c_dirent d = inode_get_dirent(trans, &dirent_iter, inode, &inode_snapshot);
+       int ret = bkey_err(d);
+       if (ret && !bch2_err_matches(ret, ENOENT))
+               return ret;
+
+       if (fsck_err_on(ret,
+                       c, inode_points_to_missing_dirent,
+                       "inode points to missing dirent\n%s",
+                       (bch2_bkey_val_to_text(&buf, c, inode_k), buf.buf)) ||
+           fsck_err_on(!ret && !dirent_points_to_inode(d, inode),
+                       c, inode_points_to_wrong_dirent,
+                       "inode points to dirent that does not point back:\n%s",
+                       (bch2_bkey_val_to_text(&buf, c, inode_k),
+                        prt_newline(&buf),
+                        bch2_bkey_val_to_text(&buf, c, d.s_c), buf.buf))) {
+               /*
+                * We just clear the backpointer fields for now. If we find a
+                * dirent that points to this inode in check_dirents(), we'll
+                * update it then; then when we get to check_path() if the
+                * backpointer is still 0 we'll reattach it.
+                */
+               inode->bi_dir = 0;
+               inode->bi_dir_offset = 0;
+               inode->bi_flags &= ~BCH_INODE_backptr_untrusted;
+               *write_inode = true;
+       }
+
+       ret = 0;
+fsck_err:
+       bch2_trans_iter_exit(trans, &dirent_iter);
+       printbuf_exit(&buf);
+       bch_err_fn(c, ret);
+       return ret;
+}
+
 static int check_inode(struct btree_trans *trans,
                       struct btree_iter *iter,
                       struct bkey_s_c k,
@@ -920,6 +1000,12 @@ static int check_inode(struct btree_trans *trans,
                do_update = true;
        }
 
+       if (u.bi_dir || u.bi_dir_offset) {
+               ret = check_inode_dirent_inode(trans, k, &u, k.k->p.snapshot, &do_update);
+               if (ret)
+                       goto err;
+       }
+
        if (u.bi_subvol) {
                struct bch_subvolume s;
 
@@ -977,28 +1063,6 @@ int bch2_check_inodes(struct bch_fs *c)
        return ret;
 }
 
-static struct bkey_s_c_dirent dirent_get_by_pos(struct btree_trans *trans,
-                                               struct btree_iter *iter,
-                                               struct bpos pos)
-{
-       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,
-                                  struct bkey_s_c_dirent d)
-{
-       return  inode->bi_dir           == d.k->p.inode &&
-               inode->bi_dir_offset    == d.k->p.offset;
-}
-
-static bool dirent_points_to_inode(struct bkey_s_c_dirent d,
-                                  struct bch_inode_unpacked *inode)
-{
-       return d.v->d_type == DT_SUBVOL
-               ? le32_to_cpu(d.v->d_child_subvol)      == inode->bi_subvol
-               : le64_to_cpu(d.v->d_inum)              == inode->bi_inum;
-}
-
 static int check_i_sectors(struct btree_trans *trans, struct inode_walker *w)
 {
        struct bch_fs *c = trans->c;
@@ -1486,7 +1550,7 @@ fsck_err:
        return ret ?: trans_was_restarted(trans, restart_count);
 }
 
-static int check_inode_backpointer(struct btree_trans *trans,
+static int check_dirent_inode_dirent(struct btree_trans *trans,
                                   struct btree_iter *iter,
                                   struct bkey_s_c_dirent d,
                                   struct bch_inode_unpacked *target,
@@ -1585,7 +1649,7 @@ static int check_dirent_target(struct btree_trans *trans,
        struct printbuf buf = PRINTBUF;
        int ret = 0;
 
-       ret = check_inode_backpointer(trans, iter, d, target, target_snapshot);
+       ret = check_dirent_inode_dirent(trans, iter, d, target, target_snapshot);
        if (ret)
                goto err;
 
@@ -2011,18 +2075,7 @@ static int check_path(struct btree_trans *trans,
                struct bkey_s_c_dirent d;
                u32 parent_snapshot = snapshot;
 
-               if (inode->bi_subvol) {
-                       u64 inum;
-
-                       ret = subvol_lookup(trans, inode->bi_parent_subvol,
-                                           &parent_snapshot, &inum);
-                       if (ret)
-                               break;
-               }
-
-               d = dirent_get_by_pos(trans, &dirent_iter,
-                                     SPOS(inode->bi_dir, inode->bi_dir_offset,
-                                          parent_snapshot));
+               d = inode_get_dirent(trans, &dirent_iter, inode, &parent_snapshot);
                ret = bkey_err(d.s_c);
                if (ret && !bch2_err_matches(ret, ENOENT))
                        break;