dm-verity: fix unreliable memory allocation

GFP_NOWAIT allocation may fail anytime. It needs to be changed to
GFP_NOIO. There's no need to handle an error because mempool_alloc with
GFP_NOIO can't fail.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: stable@vger.kernel.org
Reviewed-by: Eric Biggers <ebiggers@kernel.org>

Author: Mikulas Patocka

drivers/md/dm-verity-fec.c

@@ -320,11 +320,7 @@ static int fec_alloc_bufs(struct dm_verity *v, struct dm_verity_fec_io *fio)
 		if (fio->bufs[n])
 			continue;
 
-		fio->bufs[n] = mempool_alloc(&v->fec->prealloc_pool, GFP_NOWAIT);
-		if (unlikely(!fio->bufs[n])) {
-			DMERR("failed to allocate FEC buffer");
-			return -ENOMEM;
-		}
+		fio->bufs[n] = mempool_alloc(&v->fec->prealloc_pool, GFP_NOIO);
 	}
 
 	/* try to allocate the maximum number of buffers */