Commit 89de1504 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
Browse files

block: provide a blk_rq_map_sg variant that returns the last element 



To be able to move some of the special purpose hacks in blk_rq_map_sg
into the callers we need a variant that returns the last mapped
S/G list element to the caller.  Add that variant as __blk_rq_map_sg
and make blk_rq_map_sg a trivial inline wrapper around it.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent e64a0e16

block/blk-merge.c

+12 −13
Original line number Diff line number Diff line
@@ -519,24 +519,23 @@ static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio, 
 * 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)

int __blk_rq_map_sg(struct request_queue *q, struct request *rq,

		struct scatterlist *sglist, struct scatterlist **last_sg)

{

	struct scatterlist *sg = NULL;

	int nsegs = 0;



	if (rq->rq_flags & RQF_SPECIAL_PAYLOAD)

		nsegs = __blk_bvec_map_sg(rq->special_vec, sglist, &sg);

		nsegs = __blk_bvec_map_sg(rq->special_vec, sglist, last_sg);

	else if (rq->bio && bio_op(rq->bio) == REQ_OP_WRITE_SAME)

		nsegs = __blk_bvec_map_sg(bio_iovec(rq->bio), sglist, &sg);

		nsegs = __blk_bvec_map_sg(bio_iovec(rq->bio), sglist, last_sg);

	else if (rq->bio)

		nsegs = __blk_bios_map_sg(q, rq->bio, sglist, &sg);

		nsegs = __blk_bios_map_sg(q, rq->bio, sglist, last_sg);



	if (blk_rq_bytes(rq) && (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;

		(*last_sg)->length += pad_len;

		rq->extra_len += pad_len;

	}
@@ -544,9 +543,9 @@ int blk_rq_map_sg(struct request_queue *q, struct request *rq, 
		if (op_is_write(req_op(rq)))

			memset(q->dma_drain_buffer, 0, q->dma_drain_size);



		sg_unmark_end(sg);

		sg = sg_next(sg);

		sg_set_page(sg, virt_to_page(q->dma_drain_buffer),

		sg_unmark_end(*last_sg);

		*last_sg = sg_next(*last_sg);

		sg_set_page(*last_sg, virt_to_page(q->dma_drain_buffer),

			    q->dma_drain_size,

			    ((unsigned long)q->dma_drain_buffer) &

			    (PAGE_SIZE - 1));
@@ -554,8 +553,8 @@ int blk_rq_map_sg(struct request_queue *q, struct request *rq, 
		rq->extra_len += q->dma_drain_size;

	}



	if (sg)

		sg_mark_end(sg);

	if (*last_sg)

		sg_mark_end(*last_sg);



	/*

	 * Something must have been wrong if the figured number of
@@ -565,7 +564,7 @@ int blk_rq_map_sg(struct request_queue *q, struct request *rq, 


	return nsegs;

}

EXPORT_SYMBOL(blk_rq_map_sg);

EXPORT_SYMBOL(__blk_rq_map_sg);



static inline int ll_new_hw_segment(struct request *req, struct bio *bio,

		unsigned int nr_phys_segs)

include/linux/blkdev.h

+9 −1
Original line number Diff line number Diff line
@@ -1136,7 +1136,15 @@ static inline unsigned short blk_rq_nr_discard_segments(struct request *rq) 
	return max_t(unsigned short, rq->nr_phys_segments, 1);

}



extern int blk_rq_map_sg(struct request_queue *, struct request *, struct scatterlist *);

int __blk_rq_map_sg(struct request_queue *q, struct request *rq,

		struct scatterlist *sglist, struct scatterlist **last_sg);

static inline int blk_rq_map_sg(struct request_queue *q, struct request *rq,

		struct scatterlist *sglist)

{

	struct scatterlist *last_sg = NULL;



	return __blk_rq_map_sg(q, rq, sglist, &last_sg);

}

extern void blk_dump_rq_flags(struct request *, char *);

extern long nr_blockdev_pages(void);