xfs: call xfs_buf_delwri_queue directly

Unify the ways we add buffers to the delwri queue by always calling
xfs_buf_delwri_queue directly.  The xfs_bdwrite functions is removed and
opencoded in its callers, and the two places setting XBF_DELWRI while a
buffer is locked and expecting xfs_buf_unlock to pick it up are converted
to call xfs_buf_delwri_queue directly, too.  Also replace the
XFS_BUF_UNDELAYWRITE macro with direct calls to xfs_buf_delwri_dequeue
to make the explicit queuing/dequeuing more obvious.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Alex Elder <aelder@sgi.com>

fs/xfs/xfs_dquot.c

@@ -1243,8 +1243,10 @@ xfs_qm_dqflush(
 
 	if (flags & SYNC_WAIT)
 		error = xfs_bwrite(mp, bp);
-	else
-		xfs_bdwrite(mp, bp);
+	else {
+		xfs_buf_delwri_queue(bp);
+		xfs_buf_relse(bp);
+	}
 
 	trace_xfs_dqflush_done(dqp);