md faulty: use disk_stack_limits()

in:
fe86cdce block: do not artificially constrain max_sectors for stacking drivers

max_sectors defaults to UINT_MAX.  md faulty wasn't using
disk_stack_limits(), so inherited this large value as well.
This triggered a bug in XFS when stressed over md_faulty, when
a very large bio_alloc() failed.

That was on an older kernel, and I can't reproduce exactly the
same thing upstream, but I think the fix is appropriate in any
case.

Thanks to Mike Snitzer for pointing out the problem.
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: NeilBrown <neilb@suse.de>

drivers/md/faulty.c

@@ -315,8 +315,11 @@ static int run(struct mddev *mddev)
 	}
 	conf->nfaults = 0;
 
-	rdev_for_each(rdev, mddev)
+	rdev_for_each(rdev, mddev) {
 		conf->rdev = rdev;
+		disk_stack_limits(mddev->gendisk, rdev->bdev,
+				  rdev->data_offset << 9);
+	}
 
 	md_set_array_sectors(mddev, faulty_size(mddev, 0, 0));
 	mddev->private = conf;