xfs: kill xfs_qmops

Kill the quota ops function vector and replace it with direct calls or
stubs in the CONFIG_XFS_QUOTA=n case.

Make sure we check XFS_IS_QUOTA_RUNNING in the right spots.  We can remove
the number of those checks because the XFS_TRANS_DQ_DIRTY flag can't be set
otherwise.

This brings us back closer to the way this code worked in IRIX and earlier
Linux versions, but we keep a lot of the more useful factoring of common
code.

Eventually we should also kill xfs_qm_bhv.c, but that's left for a later
patch.

Reduces the size of the source code by about 250 lines and the size of
XFS module by about 1.5 kilobytes with quotas enabled:

   text	   data	    bss	    dec	    hex	filename
 615957	   2960	   3848	 622765	  980ad	fs/xfs/xfs.o
 617231	   3152	   3848	 624231	  98667	fs/xfs/xfs.o.old

Fallout:

 - xfs_qm_dqattach is split into xfs_qm_dqattach_locked which expects
   the inode locked and xfs_qm_dqattach which does the locking around it,
   thus removing XFS_QMOPT_ILOCKED.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Eric Sandeen <sandeen@sandeen.net>

fs/xfs/xfs_attr.c

@@ -249,8 +249,9 @@ xfs_attr_set_int(xfs_inode_t *dp, struct xfs_name *name,
 	/*
 	 * Attach the dquots to the inode.
 	 */
-	if ((error = XFS_QM_DQATTACH(mp, dp, 0)))
-		return (error);
+	error = xfs_qm_dqattach(dp, 0);
+	if (error)
+		return error;
 
 	/*
 	 * If the inode doesn't have an attribute fork, add one.
@@ -311,7 +312,7 @@ xfs_attr_set_int(xfs_inode_t *dp, struct xfs_name *name,
 	}
 	xfs_ilock(dp, XFS_ILOCK_EXCL);
 
-	error = XFS_TRANS_RESERVE_QUOTA_NBLKS(mp, args.trans, dp, args.total, 0,
+	error = xfs_trans_reserve_quota_nblks(args.trans, dp, args.total, 0,
 				rsvd ? XFS_QMOPT_RES_REGBLKS | XFS_QMOPT_FORCE_RES :
 				       XFS_QMOPT_RES_REGBLKS);
 	if (error) {
@@ -501,8 +502,9 @@ xfs_attr_remove_int(xfs_inode_t *dp, struct xfs_name *name, int flags)
 	/*
 	 * Attach the dquots to the inode.
 	 */
-	if ((error = XFS_QM_DQATTACH(mp, dp, 0)))
-		return (error);
+	error = xfs_qm_dqattach(dp, 0);
+	if (error)
+		return error;
 
 	/*
 	 * Start our first transaction of the day.