blk_queue_bounce_limit — set bounce buffer limit for queue
void blk_queue_bounce_limit (request_queue_t * q, u64 dma_addr);
Different hardware can have different requirements as to what pages
it can do I/O directly to. A low level driver can call
blk_queue_bounce_limit to have lower memory pages allocated as bounce
buffers for doing I/O to pages residing above page. By default
the block layer sets this to the highest numbered “low” memory page.