btrfs: add missing RCU unlock in error path in try_release_subpage_extent_buffer()

Call rcu_read_lock() before exiting the loop in
try_release_subpage_extent_buffer() because there is a rcu_read_unlock()
call past the loop.

This has been detected by the Clang thread-safety analyzer.

Fixes: ad580dfa388f ("btrfs: fix subpage deadlock in try_release_subpage_extent_buffer()")
CC: stable@vger.kernel.org # 6.18+
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Boris Burkov <boris@bur.io>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 3df399dc88567b1bc41cdcca5b812336ecb442d3..051309e900796497612f5e5842283d56db0aceba 100644 (file)
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -4494,6 +4494,7 @@ static int try_release_subpage_extent_buffer(struct folio *folio)
                 */
                if (!test_and_clear_bit(EXTENT_BUFFER_TREE_REF, &eb->bflags)) {
                        spin_unlock(&eb->refs_lock);
+                       rcu_read_lock();
                        break;
                }