Hi, I'm just checking dm-crypt with highmem and found that dm doesn't call blk_queue_bounce_limit. That means the queue will use BLK_BOUNCE_HIGH by default. That means that all BIOs will be unnecessarily bounced to lowmem before the upcall to dm even if the underlying queue supports highmem pages. We could either call blk_queue_bounce_limit(q, BLK_BOUNCE_ANY) which will bounce the queue when DM calls generic_make_request or combine q->bounce_pfn high.
