xfs: use ->t_dfops for attr set/remove operations

Attach the local dfops to the transaction allocated for xattr add
and remove operations. Add an earlier initialization in
xfs_attr_remove() to ensure the structure is valid if it remains
unused at transaction commit time.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

fs/xfs/libxfs/xfs_bmap.c

@@ -1057,6 +1057,8 @@ xfs_bmap_add_attrfork(
 			rsvd ? XFS_TRANS_RESERVE : 0, &tp);
 	if (error)
 		return error;
+	xfs_defer_init(&dfops, &firstblock);
+	tp->t_dfops = &dfops;
 
 	xfs_ilock(ip, XFS_ILOCK_EXCL);
 	error = xfs_trans_reserve_quota_nblks(tp, ip, blks, 0, rsvd ?
@@ -1104,7 +1106,6 @@ xfs_bmap_add_attrfork(
 	ip->i_afp = kmem_zone_zalloc(xfs_ifork_zone, KM_SLEEP);
 	ip->i_afp->if_flags = XFS_IFEXTENTS;
 	logflags = 0;
-	xfs_defer_init(&dfops, &firstblock);
 	switch (ip->i_d.di_format) {
 	case XFS_DINODE_FMT_LOCAL:
 		error = xfs_bmap_add_attrfork_local(tp, ip, &firstblock, &dfops,