linux-kernel - Re: [PATCH 14/14] xfs: use atomic_dec_not

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Message-ID: <20170131003033.GD9134@birch.djwong.org>
Date:   Mon, 30 Jan 2017 16:30:33 -0800
From:   "Darrick J. Wong" <darrick.wong@...cle.com>
To:     Fabian Frederick <fabf@...net.be>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, linux-xfs@...r.kernel.org
Subject: Re: [PATCH 14/14] xfs: use atomic_dec_not_zero()

On Mon, Jan 30, 2017 at 07:48:44PM +0100, Fabian Frederick wrote:
> instead of atomic_add_unless(value, -1, 0)
> 
> Signed-off-by: Fabian Frederick <fabf@...net.be>
> ---
>  fs/xfs/xfs_buf.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
> index ac3b4db..51b2167 100644
> --- a/fs/xfs/xfs_buf.c
> +++ b/fs/xfs/xfs_buf.c
> @@ -1684,7 +1684,7 @@ xfs_buftarg_isolate(
>  	 * zero. If the value is already zero, we need to reclaim the
>  	 * buffer, otherwise it gets another trip through the LRU.
>  	 */
> -	if (!atomic_add_unless(&bp->b_lru_ref, -1, 0)) {
> +	if (!atomic_dec_not_zero(&bp->b_lru_ref)) {

Hard to tell if this is correct, since there's no atomic_dec_not_zero
defined in any of my kernel trees' include/ headers and I haven't seen a
patch adding such a symbol appear on this list.  Did you hoist the
lib/fault-inject.c definition or something?

--D

>  		spin_unlock(&bp->b_lock);
>  		return LRU_ROTATE;
>  	}
> -- 
> 2.9.3
> 
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