4.19-stable review patch. If anyone has any objections, please let me know.
------------------
From: Josef Bacik <josef@xxxxxxxxxxxxxx>
[ Upstream commit b8ccef048354074a548f108e51d0557d6adfd3a3 ]
In reada we BUG_ON(refs == 0), which could be unkind since we aren't
holding a lock on the extent leaf and thus could get a transient
incorrect answer. In walk_down_proc we also BUG_ON(refs == 0), which
could happen if we have extent tree corruption. Change that to return
-EUCLEAN. In do_walk_down() we catch this case and handle it correctly,
however we return -EIO, which -EUCLEAN is a more appropriate error code.
Finally in walk_up_proc we have the same BUG_ON(refs == 0), so convert
that to proper error handling. Also adjust the error message so we can
actually do something with the information.
Signed-off-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
Reviewed-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
fs/btrfs/extent-tree.c | 28 +++++++++++++++++++++++-----
1 file changed, 23 insertions(+), 5 deletions(-)
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 635d51c8098d..6b8ece5175ef 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -8409,7 +8409,15 @@ static noinline void reada_walk_down(struct btrfs_trans_handle *trans,
/* We don't care about errors in readahead. */
if (ret < 0)
continue;
- BUG_ON(refs == 0);
+
+ /*
+ * This could be racey, it's conceivable that we raced and end
+ * up with a bogus refs count, if that's the case just skip, if
+ * we are actually corrupt we will notice when we look up
+ * everything again with our locks.
+ */
+ if (refs == 0)
+ continue;
if (wc->stage == DROP_REFERENCE) {
if (refs == 1)
@@ -8476,7 +8484,11 @@ static noinline int walk_down_proc(struct btrfs_trans_handle *trans,
BUG_ON(ret == -ENOMEM);
if (ret)
return ret;
- BUG_ON(wc->refs[level] == 0);
+ if (unlikely(wc->refs[level] == 0)) {
+ btrfs_err(fs_info, "bytenr %llu has 0 references, expect > 0",
+ eb->start);
+ return -EUCLEAN;
+ }
}
if (wc->stage == DROP_REFERENCE) {
@@ -8584,8 +8596,9 @@ static noinline int do_walk_down(struct btrfs_trans_handle *trans,
goto out_unlock;
if (unlikely(wc->refs[level - 1] == 0)) {
- btrfs_err(fs_info, "Missing references.");
- ret = -EIO;
+ btrfs_err(fs_info, "bytenr %llu has 0 references, expect > 0",
+ bytenr);
+ ret = -EUCLEAN;
goto out_unlock;
}
*lookup_info = 0;
@@ -8753,7 +8766,12 @@ static noinline int walk_up_proc(struct btrfs_trans_handle *trans,
path->locks[level] = 0;
return ret;
}
- BUG_ON(wc->refs[level] == 0);
+ if (unlikely(wc->refs[level] == 0)) {
+ btrfs_tree_unlock_rw(eb, path->locks[level]);
+ btrfs_err(fs_info, "bytenr %llu has 0 references, expect > 0",
+ eb->start);
+ return -EUCLEAN;
+ }
if (wc->refs[level] == 1) {
btrfs_tree_unlock_rw(eb, path->locks[level]);
path->locks[level] = 0;
--
2.43.0
