bcachefs: Allow for unknown key types in backpointers fsck

We can't assume that btrees only contain keys of a given type - even if
they only have a single key type listed in the allowed key types for
that btree; this is a forwards compatibility issue.

Reported-by: syzbot+a27c3aaa3640dd3e1dfb@syzkaller.appspotmail.com
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

diff --git a/fs/bcachefs/backpointers.c b/fs/bcachefs/backpointers.c
index ed344400c8bdcf8355ea2d5b6b98392fd84b7cab..654a58132a4db675bbcb2b19d592ca9010e05c7f 100644 (file)
--- a/fs/bcachefs/backpointers.c
+++ b/fs/bcachefs/backpointers.c
@@ -952,9 +952,13 @@ int bch2_check_extents_to_backpointers(struct bch_fs *c)
 static int check_one_backpointer(struct btree_trans *trans,
                                 struct bbpos start,
                                 struct bbpos end,
-                                struct bkey_s_c_backpointer bp,
+                                struct bkey_s_c bp_k,
                                 struct bkey_buf *last_flushed)
 {
+       if (bp_k.k->type != KEY_TYPE_backpointer)
+               return 0;
+
+       struct bkey_s_c_backpointer bp = bkey_s_c_to_backpointer(bp_k);
        struct bch_fs *c = trans->c;
        struct btree_iter iter;
        struct bbpos pos = bp_to_bbpos(*bp.v);
@@ -1009,9 +1013,7 @@ static int bch2_check_backpointers_to_extents_pass(struct btree_trans *trans,
                                  POS_MIN, BTREE_ITER_prefetch, k,
                                  NULL, NULL, BCH_TRANS_COMMIT_no_enospc, ({
                        progress_update_iter(trans, &progress, &iter, "backpointers_to_extents");
-                       check_one_backpointer(trans, start, end,
-                                             bkey_s_c_to_backpointer(k),
-                                             &last_flushed);
+                       check_one_backpointer(trans, start, end, k, &last_flushed);
        }));
 
        bch2_bkey_buf_exit(&last_flushed, c);