xfs: ratelimit xfs_buf_ioerror_alert messages

Use printk_ratelimit() to limit the amount of messages printed from
xfs_buf_ioerror_alert.  Without that a failing device causes a large
number of errors that doesn't really help debugging the underling
issue.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

fs/xfs/xfs_buf.c

@@ -1239,7 +1239,7 @@ xfs_buf_ioerror_alert(
 	struct xfs_buf		*bp,
 	xfs_failaddr_t		func)
 {
-	xfs_alert(bp->b_mount,
+	xfs_alert_ratelimited(bp->b_mount,
 "metadata I/O error in \"%pS\" at daddr 0x%llx len %d error %d",
 			func, (uint64_t)XFS_BUF_ADDR(bp), bp->b_length,
 			-bp->b_error);