Re: [PATCH v3 5/5] xfs: directly return if the delta equal to zero

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Wed, Oct 07, 2020 at 10:51:12PM +0800, xiakaixu1987@gmail.com wrote:
> From: Kaixu Xia <kaixuxia@tencent.com>
> 
> The xfs_trans_mod_dquot() function will allocate new tp->t_dqinfo if it is
> NULL and make the changes in the tp->t_dqinfo->dqs[XFS_QM_TRANS_{USR,GRP,PRJ}].
> Nowadays seems none of the callers want to join the dquots to the
> transaction and push them to device when the delta is zero. Actually,
> most of time the caller would check the delta and go on only when the
> delta value is not zero, so we should bail out when it is zero.
> 
> Signed-off-by: Kaixu Xia <kaixuxia@tencent.com>

Looks decent now; as far as I can tell, nothing will trip over null
t_dqinfo if we're not actually changing the dquots...

Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

--D

> ---
>  fs/xfs/xfs_trans_dquot.c | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/xfs/xfs_trans_dquot.c b/fs/xfs/xfs_trans_dquot.c
> index 0ebfd7930382..3e37501791bf 100644
> --- a/fs/xfs/xfs_trans_dquot.c
> +++ b/fs/xfs/xfs_trans_dquot.c
> @@ -194,6 +194,9 @@ xfs_trans_mod_dquot(
>  	ASSERT(XFS_IS_QUOTA_RUNNING(tp->t_mountp));
>  	qtrx = NULL;
>  
> +	if (!delta)
> +		return;
> +
>  	if (tp->t_dqinfo == NULL)
>  		xfs_trans_alloc_dqinfo(tp);
>  	/*
> @@ -205,10 +208,8 @@ xfs_trans_mod_dquot(
>  	if (qtrx->qt_dquot == NULL)
>  		qtrx->qt_dquot = dqp;
>  
> -	if (delta) {
> -		trace_xfs_trans_mod_dquot_before(qtrx);
> -		trace_xfs_trans_mod_dquot(tp, dqp, field, delta);
> -	}
> +	trace_xfs_trans_mod_dquot_before(qtrx);
> +	trace_xfs_trans_mod_dquot(tp, dqp, field, delta);
>  
>  	switch (field) {
>  	/* regular disk blk reservation */
> @@ -261,8 +262,7 @@ xfs_trans_mod_dquot(
>  		ASSERT(0);
>  	}
>  
> -	if (delta)
> -		trace_xfs_trans_mod_dquot_after(qtrx);
> +	trace_xfs_trans_mod_dquot_after(qtrx);
>  }
>  
>  
> -- 
> 2.20.0
>