bcachefs: Fix snapshot_skiplist_good()

We weren't correctly checking snapshot skiplist nodes - we were checking
if they were in the same tree, not if they were an actual ancestor.

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

diff --git a/fs/bcachefs/snapshot.c b/fs/bcachefs/snapshot.c
index 07e5c1b44b067bcac3d523950fa2ef29b5550fe3..9da09911466e8a5c9dd5c8529e2b066cd2a696e3 100644 (file)
--- a/fs/bcachefs/snapshot.c
+++ b/fs/bcachefs/snapshot.c
@@ -655,28 +655,18 @@ u32 bch2_snapshot_skiplist_get(struct bch_fs *c, u32 id)
        return id;
 }
 
-static int snapshot_skiplist_good(struct btree_trans *trans, struct bch_snapshot s)
+static int snapshot_skiplist_good(struct btree_trans *trans, u32 id, struct bch_snapshot s)
 {
-       struct bch_snapshot a;
        unsigned i;
-       int ret;
-
-       for (i = 0; i < 3; i++) {
-               if (!s.parent != !s.skip[i])
-                       return false;
-
-               if (!s.parent)
-                       continue;
 
-               ret = bch2_snapshot_lookup(trans, le32_to_cpu(s.skip[i]), &a);
-               if (bch2_err_matches(ret, ENOENT))
-                       return false;
-               if (ret)
-                       return ret;
-
-               if (a.tree != s.tree)
-                       return false;
-       }
+       for (i = 0; i < 3; i++)
+               if (!s.parent) {
+                       if (s.skip[i])
+                               return false;
+               } else {
+                       if (!bch2_snapshot_is_ancestor_early(trans->c, id, le32_to_cpu(s.skip[i])))
+                               return false;
+               }
 
        return true;
 }
@@ -856,7 +846,7 @@ static int check_snapshot(struct btree_trans *trans,
                s = u->v;
        }
 
-       ret = snapshot_skiplist_good(trans, s);
+       ret = snapshot_skiplist_good(trans, k.k->p.offset, s);
        if (ret < 0)
                goto err;