xfs: fetch dquots directly during quotacheck

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>
Reviewed-by: Christoph Hellwig <hch@lst.de>

fs/xfs/xfs_qm.c

@@ -1056,16 +1056,17 @@ 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(ip, type, true, &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.
@@ -1138,13 +1139,10 @@ 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;
@@ -1179,33 +1177,31 @@ 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;