[dm-devel] queue limits and blk_queue_bounce

[Christophe Saout]

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.