Re: [PATCH v3 2/2] fscache: Use clear_and_wake_up_bit() in fscache_create_volume_work()

[Jeff Layton <jlayton@kernel.org>]

On Fri, 2023-01-13 at 19:52 +0800, Hou Tao wrote:
> From: Hou Tao <houtao1@huawei.com>
> 
> 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>
> ---
>  fs/fscache/volume.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/fs/fscache/volume.c b/fs/fscache/volume.c
> index 903af9d85f8b..cdf991bdd9de 100644
> --- 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);
>  }
>  

Reviewed-by: Jeff Layton <jlayton@kernel.org>