[dm-devel] [dm-6.4 PATCH v3 10/20] dm bufio: use waitqueue_active in __free_buffer_wake

Mike Snitzer
2023-03-27T20:13:47Z

From: Mikulas Patocka <mpatocka@redhat.com>

Save one spinlock by using waitqueue_active. We hold the bufio lock at
this place, so no one can add entries to the waitqueue at this point.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
---
drivers/md/dm-bufio.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/md/dm-bufio.c b/drivers/md/dm-bufio.c
index e5459741335d..cca43ed13fd1 100644
--- a/drivers/md/dm-bufio.c
+++ b/drivers/md/dm-bufio.c
@@ -1665,7 +1665,12 @@ static void __free_buffer_wake(struct dm_buffer *b)
c->need_reserved_buffers--;
}

- wake_up(&c->free_buffer_wait);
+ /*
+ * We hold the bufio lock here, so no one can add entries to the
+ * wait queue anyway.
+ */
+ if (unlikely(waitqueue_active(&c->free_buffer_wait)))
+ wake_up(&c->free_buffer_wait);
}

static enum evict_result cleaned(struct dm_buffer *b, void *context)