[PATCH 5.10 587/717] btrfs: do not shorten unpin len for caching block groups

Greg Kroah-Hartman
2020-12-28T14:28:01Z

From: Josef Bacik <josef@toxicpanda.com>

commit 9076dbd5ee837c3882fc42891c14cecd0354a849 upstream.

While fixing up our ->last_byte_to_unpin locking I noticed that we will
shorten len based on ->last_byte_to_unpin if we're caching when we're
adding back the free space. This is correct for the free space, as we
cannot unpin more than ->last_byte_to_unpin, however we use len to
adjust the ->bytes_pinned counters and such, which need to track the
actual pinned usage. This could result in
WARN_ON(space_info->bytes_pinned) triggering at unmount time.

Fix this by using a local variable for the amount to add to free space
cache, and leave len untouched in this case.

CC: stable@vger.kernel.org # 5.4+
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/btrfs/extent-tree.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -2816,10 +2816,10 @@ static int unpin_extent_range(struct btr
len = cache->start + cache->length - start;
len = min(len, end + 1 - start);

- if (start < cache->last_byte_to_unpin) {
- len = min(len, cache->last_byte_to_unpin - start);
- if (return_free_space)
- btrfs_add_free_space(cache, start, len);
+ if (start < cache->last_byte_to_unpin && return_free_space) {
+ u64 add_len = min(len, cache->last_byte_to_unpin - start);
+
+ btrfs_add_free_space(cache, start, add_len);
}

start += len;