dm-crypt: start allocating with MAX_ORDER

Commit 23baf83 ("mm, treewide: redefine MAX_ORDER sanely")
changed the meaning of MAX_ORDER from exclusive to inclusive. So, we
can allocate compound pages with up to 1 << MAX_ORDER pages.

Reflect this change in dm-crypt and start trying to allocate compound
pages with MAX_ORDER.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

Author: Mikulas Patocka

drivers/md/dm-crypt.c

@@ -1673,7 +1673,7 @@ static struct bio *crypt_alloc_buffer(struct dm_crypt_io *io, unsigned int size)
 	unsigned int nr_iovecs = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
 	gfp_t gfp_mask = GFP_NOWAIT | __GFP_HIGHMEM;
 	unsigned int remaining_size;
-	unsigned int order = MAX_ORDER - 1;
+	unsigned int order = MAX_ORDER;
 
 retry:
 	if (unlikely(gfp_mask & __GFP_DIRECT_RECLAIM))