/**
* blk_bio_map_sg - map a bio to a scatterlist
* @q: request_queue in question
* @bio: bio being mapped
* @sglist: scatterlist being mapped
*
* Note:
* Caller must make sure sg can hold bio->bi_phys_segments entries
*
* Will return the number of sg entries setup
*/
int blk_bio_map_sg(struct request_queue *q, struct bio *bio,
struct scatterlist *sglist)
{
struct scatterlist *sg = NULL;
int nsegs;
struct bio *next = bio->bi_next;
bio->bi_next = NULL;
nsegs = __blk_bios_map_sg(q, bio, sglist, &sg);
bio->bi_next = next;
if (sg)
sg_mark_end(sg);
BUG_ON(bio->bi_phys_segments && nsegs > bio->bi_phys_segments);
return nsegs;
}
/*
* map a request to scatterlist, return number of sg entries setup. Caller
* must make sure sg can hold rq->nr_phys_segments entries
*/
int blk_rq_map_sg(struct request_queue *q, struct request *rq,
struct scatterlist *sglist)
{
struct scatterlist *sg = NULL;
int nsegs = 0;
if (rq->bio)
nsegs = __blk_bios_map_sg(q, rq->bio, sglist, &sg);
if (unlikely(rq->cmd_flags & REQ_COPY_USER) &&
(blk_rq_bytes(rq) & q->dma_pad_mask)) {
unsigned int pad_len =
(q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1;
sg->length += pad_len;
rq->extra_len += pad_len;
}
if (q->dma_drain_size && q->dma_drain_needed(rq)) {
if (rq->cmd_flags & REQ_WRITE)
memset(q->dma_drain_buffer, 0, q->dma_drain_size);
sg->page_link &= ~0x02;
sg = sg_next(sg);
sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
q->dma_drain_size,
((unsigned long)q->dma_drain_buffer) &
(PAGE_SIZE - 1));
nsegs++;
rq->extra_len += q->dma_drain_size;
}
if (sg)
sg_mark_end(sg);
return nsegs;
}
