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 <[e-mail]>
Signed-off-by: Hou Tao <[e-mail]>
Signed-off-by: David Howells <[e-mail]>
Reviewed-by: Jeff Layton <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]/ # v3

fs/fscache/volume.c

···
 	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);
 }