Re: [PATCH 06/13] xfs: fetch dquots directly during quotacheck

[Brian Foster <bfoster@redhat.com>]

On Sun, Apr 22, 2018 at 08:06:30AM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> Quotacheck only runs during mount, which means that there are no other
> processes in the system that could be doing chown or chproj.  Therefore
> there's no potential for racing to attach dquots to the inode so we can
> drop all the ILOCK and race detection bits from quotacheck.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---

Reviewed-by: Brian Foster <bfoster@redhat.com>

>  fs/xfs/xfs_qm.c |   28 ++++++++++++----------------
>  1 file changed, 12 insertions(+), 16 deletions(-)
> 
> 
> diff --git a/fs/xfs/xfs_qm.c b/fs/xfs/xfs_qm.c
> index 385d315..123ea5f 100644
> --- a/fs/xfs/xfs_qm.c
> +++ b/fs/xfs/xfs_qm.c
> @@ -1065,16 +1065,17 @@ xfs_qm_dqiterate(
>  STATIC int
>  xfs_qm_quotacheck_dqadjust(
>  	struct xfs_inode	*ip,
> -	xfs_dqid_t		id,
>  	uint			type,
>  	xfs_qcnt_t		nblks,
>  	xfs_qcnt_t		rtblks)
>  {
>  	struct xfs_mount	*mp = ip->i_mount;
>  	struct xfs_dquot	*dqp;
> +	xfs_dqid_t		id;
>  	int			error;
>  
> -	error = xfs_qm_dqget_inode(mp, ip, type, XFS_QMOPT_DQALLOC, &dqp);
> +	id = xfs_qm_id_for_quotatype(ip, type);
> +	error = xfs_qm_dqget(mp, id, type, XFS_QMOPT_DQALLOC, &dqp);
>  	if (error) {
>  		/*
>  		 * Shouldn't be able to turn off quotas here.
> @@ -1147,13 +1148,10 @@ xfs_qm_dqusage_adjust(
>  	}
>  
>  	/*
> -	 * We don't _need_ to take the ilock EXCL. However, the xfs_qm_dqget
> -	 * interface expects the inode to be exclusively locked because that's
> -	 * the case in all other instances. It's OK that we do this because
> -	 * quotacheck is done only at mount time.
> +	 * We don't _need_ to take the ilock EXCL here because quotacheck runs
> +	 * at mount time and therefore nobody will be racing chown/chproj.
>  	 */
> -	error = xfs_iget(mp, NULL, ino, XFS_IGET_DONTCACHE, XFS_ILOCK_EXCL,
> -			 &ip);
> +	error = xfs_iget(mp, NULL, ino, XFS_IGET_DONTCACHE, 0, &ip);
>  	if (error) {
>  		*res = BULKSTAT_RV_NOTHING;
>  		return error;
> @@ -1188,33 +1186,31 @@ xfs_qm_dqusage_adjust(
>  	 * and quotaoffs don't race. (Quotachecks happen at mount time only).
>  	 */
>  	if (XFS_IS_UQUOTA_ON(mp)) {
> -		error = xfs_qm_quotacheck_dqadjust(ip, ip->i_d.di_uid,
> -						   XFS_DQ_USER, nblks, rtblks);
> +		error = xfs_qm_quotacheck_dqadjust(ip, XFS_DQ_USER, nblks,
> +				rtblks);
>  		if (error)
>  			goto error0;
>  	}
>  
>  	if (XFS_IS_GQUOTA_ON(mp)) {
> -		error = xfs_qm_quotacheck_dqadjust(ip, ip->i_d.di_gid,
> -						   XFS_DQ_GROUP, nblks, rtblks);
> +		error = xfs_qm_quotacheck_dqadjust(ip, XFS_DQ_GROUP, nblks,
> +				rtblks);
>  		if (error)
>  			goto error0;
>  	}
>  
>  	if (XFS_IS_PQUOTA_ON(mp)) {
> -		error = xfs_qm_quotacheck_dqadjust(ip, xfs_get_projid(ip),
> -						   XFS_DQ_PROJ, nblks, rtblks);
> +		error = xfs_qm_quotacheck_dqadjust(ip, XFS_DQ_PROJ, nblks,
> +				rtblks);
>  		if (error)
>  			goto error0;
>  	}
>  
> -	xfs_iunlock(ip, XFS_ILOCK_EXCL);
>  	IRELE(ip);
>  	*res = BULKSTAT_RV_DIDONE;
>  	return 0;
>  
>  error0:
> -	xfs_iunlock(ip, XFS_ILOCK_EXCL);
>  	IRELE(ip);
>  	*res = BULKSTAT_RV_GIVEUP;
>  	return error;
> 
> --
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