fscache: Use clear_and_wake_up_bit() in fscache_create_volume_work()

fscache_create_volume_work() uses wake_up_bit() to wake up the processes
which are waiting for the completion of volume creation. According to
comments in wake_up_bit() and waitqueue_active(), an extra smp_mb() is
needed to guarantee the memory order between FSCACHE_VOLUME_CREATING
flag and waitqueue_active() before invoking wake_up_bit().

Fixing it by using clear_and_wake_up_bit() to add the missing memory
barrier.

Reviewed-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Link: https://lore.kernel.org/r/20230113115211.2895845-3-houtao@huaweicloud.com/

diff --git a/fs/fscache/volume.c b/fs/fscache/volume.c
index 903af9d..cdf991b 100644 (file)
--- a/fs/fscache/volume.c
+++ b/fs/fscache/volume.c
@@ -280,8 +280,7 @@ static void fscache_create_volume_work(struct work_struct *work)
        fscache_end_cache_access(volume->cache,
                                 fscache_access_acquire_volume_end);
 
-       clear_bit_unlock(FSCACHE_VOLUME_CREATING, &volume->flags);
-       wake_up_bit(&volume->flags, FSCACHE_VOLUME_CREATING);
+       clear_and_wake_up_bit(FSCACHE_VOLUME_CREATING, &volume->flags);
        fscache_put_volume(volume, fscache_volume_put_create_work);
 }