Re: [PATCH 3/3] xfs: only do dqget or dqhold for the specified dquots

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

On Tue, Sep 22, 2020 at 05:04:02PM +0800, xiakaixu1987@gmail.com wrote:
> From: Kaixu Xia <kaixuxia@tencent.com>
> 
> We attach the dquot(s) to the given inode and return udquot, gdquot
> or pdquot with references taken by dqget or dqhold in xfs_qm_vop_dqalloc()
> funciton. Actually, we only need to do dqget or dqhold for the specified
> dquots, it is unnecessary if the passed-in O_{u,g,p}dqpp value is NULL.

When would a caller pass in (for example) XFS_QMOPT_UQUOTA, a different
uid than the one currently associated with the inode, but a null
O_udqpp?  It doesn't make sense to say "Prepare to change this file's
uid, but don't give me the dquot of the new uid."

None of the callers do that today, so I don't see the point of this
patch.  Perhaps the function could ASSERT the arguments a little more
closely?

--D

> Signed-off-by: Kaixu Xia <kaixuxia@tencent.com>
> ---
>  fs/xfs/xfs_qm.c | 13 ++++---------
>  1 file changed, 4 insertions(+), 9 deletions(-)
> 
> diff --git a/fs/xfs/xfs_qm.c b/fs/xfs/xfs_qm.c
> index 44509decb4cd..38380fc29b4d 100644
> --- a/fs/xfs/xfs_qm.c
> +++ b/fs/xfs/xfs_qm.c
> @@ -1661,7 +1661,7 @@ xfs_qm_vop_dqalloc(
>  		}
>  	}
>  
> -	if ((flags & XFS_QMOPT_UQUOTA) && XFS_IS_UQUOTA_ON(mp)) {
> +	if ((flags & XFS_QMOPT_UQUOTA) && XFS_IS_UQUOTA_ON(mp) && O_udqpp) {
>  		if (!uid_eq(inode->i_uid, uid)) {
>  			/*
>  			 * What we need is the dquot that has this uid, and
> @@ -1694,7 +1694,7 @@ xfs_qm_vop_dqalloc(
>  			uq = xfs_qm_dqhold(ip->i_udquot);
>  		}
>  	}
> -	if ((flags & XFS_QMOPT_GQUOTA) && XFS_IS_GQUOTA_ON(mp)) {
> +	if ((flags & XFS_QMOPT_GQUOTA) && XFS_IS_GQUOTA_ON(mp) && O_gdqpp) {
>  		if (!gid_eq(inode->i_gid, gid)) {
>  			xfs_iunlock(ip, lockflags);
>  			error = xfs_qm_dqget(mp, from_kgid(user_ns, gid),
> @@ -1711,7 +1711,7 @@ xfs_qm_vop_dqalloc(
>  			gq = xfs_qm_dqhold(ip->i_gdquot);
>  		}
>  	}
> -	if ((flags & XFS_QMOPT_PQUOTA) && XFS_IS_PQUOTA_ON(mp)) {
> +	if ((flags & XFS_QMOPT_PQUOTA) && XFS_IS_PQUOTA_ON(mp) && O_pdqpp) {
>  		if (ip->i_d.di_projid != prid) {
>  			xfs_iunlock(ip, lockflags);
>  			error = xfs_qm_dqget(mp, prid,
> @@ -1733,16 +1733,11 @@ xfs_qm_vop_dqalloc(
>  	xfs_iunlock(ip, lockflags);
>  	if (O_udqpp)
>  		*O_udqpp = uq;
> -	else
> -		xfs_qm_dqrele(uq);
>  	if (O_gdqpp)
>  		*O_gdqpp = gq;
> -	else
> -		xfs_qm_dqrele(gq);
>  	if (O_pdqpp)
>  		*O_pdqpp = pq;
> -	else
> -		xfs_qm_dqrele(pq);
> +
>  	return 0;
>  
>  error_rele:
> -- 
> 2.20.0
>