4.19-stable review patch. If anyone has any objections, please let me know.
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From: Josef Bacik josef@toxicpanda.com
[ 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@toxicpanda.com Reviewed-by: David Sterba dsterba@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Sasha Levin sashal@kernel.org --- 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;