[PATCH 1/2] fs: buffer: use clear_and_wake_up_bit() in unlock_buffer()

Use `clear_and_wake_up_bit()` in `unlock_buffer()`, since the helper was
introduced in 'commit 8236b0ae31c83 ("bdi: wake up concurrent
wb_shutdown() callers.")' as a generic way of doing the same sequence of
operations:
       	clear_bit_unlock();
	smp_mb__after_atomic();
	wake_up_bit();

The helper was implemented to avoid bugs caused by forgetting to call
`wake_up_bit()` after `clear_bit_unlock()`.

Since `unlock_buffer()` predates git and was last modified in
'commit 4e857c58efeb9 ("arch: Mass conversion of smp_mb__*()")', years
before `clear_and_wake_up_bit()`, it still uses the open-coded sequence.

Replace the open-coded sequence with the helper to avoid duplicate code
and reduce code paths to maintain.

Suggested-by: shuo chen <[email protected]>
Link: https://lore.kernel.org/kernelnewbies/agzoqV835-co4kAN@guidai/T/#t
Signed-off-by: Agatha Isabelle Moreira <[email protected]>
---
 fs/buffer.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index b0b3792b1496..4348b240bd97 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -74,9 +74,7 @@ EXPORT_SYMBOL(__lock_buffer);
 
 void unlock_buffer(struct buffer_head *bh)
 {
-	clear_bit_unlock(BH_Lock, &bh->b_state);
-	smp_mb__after_atomic();
-	wake_up_bit(&bh->b_state, BH_Lock);
+	clear_and_wake_up_bit(BH_Lock, &bh->b_state);
 }
 EXPORT_SYMBOL(unlock_buffer);
 
-- 
2.53.0