[PATCH] md: dm-writeback: add __noreturn to BUG-ging function

[Randy Dunlap]

Building on arch/s390/ flags this as an error, so add the
__noreturn attribute modifier to prevent the build error.

cc1: some warnings being treated as errors
../drivers/md/dm-writecache.c: In function 'persistent_memory_claim':
../drivers/md/dm-writecache.c:323:1: error: no return statement in function returning non-void [-Werror=return-type]

Fixes: 48debafe4f2f ("dm: add writecache target")
Signed-off-by: Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
Cc: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Cc: Alasdair Kergon <agk@xxxxxxxxxx>
Cc: Mike Snitzer <snitzer@xxxxxxxxxx>
Cc: dm-devel@xxxxxxxxxx
Cc: Heiko Carstens <hca@xxxxxxxxxxxxx>
Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx>
Cc: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Cc: linux-s390@xxxxxxxxxxxxxxx
---
 drivers/md/dm-writecache.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- linux-next-20201113.orig/drivers/md/dm-writecache.c
+++ linux-next-20201113/drivers/md/dm-writecache.c
@@ -317,7 +317,7 @@ err1:
 	return r;
 }
 #else
-static int persistent_memory_claim(struct dm_writecache *wc)
+static int __noreturn persistent_memory_claim(struct dm_writecache *wc)
 {
 	BUG();
 }