dm crypt: Fix IO priority lost when queuing write bios

Since dm-crypt queues writes to a different kernel thread (workqueue),
the bios will dispatch from tasks with different io_context->ioprio
settings and blkcg than the submitting task, thus giving incorrect
ioprio to the io scheduler.

Get the original IO priority setting via struct dm_crypt_io::base_bio
and set this priority in the bio for write.

Link: https://lore.kernel.org/dm-devel/alpine.LRH.2.11.1612141049250.13402@mail.ewheeler.net

Signed-off-by: Hongyu Jin <hongyu.jin@unisoc.com>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

Author: Hongyu Jin

drivers/md/dm-crypt.c

@@ -1688,6 +1688,7 @@ static struct bio *crypt_alloc_buffer(struct dm_crypt_io *io, unsigned int size)
 				 GFP_NOIO, &cc->bs);
 	clone->bi_private = io;
 	clone->bi_end_io = crypt_endio;
+	clone->bi_ioprio = io->base_bio->bi_ioprio;
 
 	remaining_size = size;