[mirror_ubuntu-zesty-kernel.git] / block / blk-merge.c

/*
 * Functions related to segment and merge handling
 */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/scatterlist.h>

#include "blk.h"

static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
					     struct bio *bio)
{
	struct bio_vec *bv, *bvprv = NULL;
	int cluster, i, high, highprv = 1;
	unsigned int seg_size, nr_phys_segs;
	struct bio *fbio, *bbio;

	if (!bio)
		return 0;

	fbio = bio;
	cluster = blk_queue_cluster(q);
	seg_size = 0;
	nr_phys_segs = 0;
	for_each_bio(bio) {
		bio_for_each_segment(bv, bio, i) {
			/*
			 * the trick here is making sure that a high page is
			 * never considered part of another segment, since that
			 * might change with the bounce page.
			 */
			high = page_to_pfn(bv->bv_page) > queue_bounce_pfn(q);
			if (high || highprv)
				goto new_segment;
			if (cluster) {
				if (seg_size + bv->bv_len
				    > queue_max_segment_size(q))
					goto new_segment;
				if (!BIOVEC_PHYS_MERGEABLE(bvprv, bv))
					goto new_segment;
				if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bv))
					goto new_segment;

				seg_size += bv->bv_len;
				bvprv = bv;
				continue;
			}
new_segment:
			if (nr_phys_segs == 1 && seg_size >
			    fbio->bi_seg_front_size)
				fbio->bi_seg_front_size = seg_size;

			nr_phys_segs++;
			bvprv = bv;
			seg_size = bv->bv_len;
			highprv = high;
		}
		bbio = bio;
	}

	if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size)
		fbio->bi_seg_front_size = seg_size;
	if (seg_size > bbio->bi_seg_back_size)
		bbio->bi_seg_back_size = seg_size;

	return nr_phys_segs;
}

void blk_recalc_rq_segments(struct request *rq)
{
	rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio);
}

void blk_recount_segments(struct request_queue *q, struct bio *bio)
{
	struct bio *nxt = bio->bi_next;

	bio->bi_next = NULL;
	bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio);
	bio->bi_next = nxt;
	bio->bi_flags |= (1 << BIO_SEG_VALID);
}
EXPORT_SYMBOL(blk_recount_segments);

static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
				   struct bio *nxt)
{
	if (!blk_queue_cluster(q))
		return 0;

	if (bio->bi_seg_back_size + nxt->bi_seg_front_size >
	    queue_max_segment_size(q))
		return 0;

	if (!bio_has_data(bio))
		return 1;

	if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)))
		return 0;

	/*
	 * bio and nxt are contiguous in memory; check if the queue allows
	 * these two to be merged into one
	 */
	if (BIO_SEG_BOUNDARY(q, bio, nxt))
		return 1;

	return 0;
}

static void
__blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec,
		     struct scatterlist *sglist, struct bio_vec **bvprv,
		     struct scatterlist **sg, int *nsegs, int *cluster)
{

	int nbytes = bvec->bv_len;

	if (*bvprv && *cluster) {
		if ((*sg)->length + nbytes > queue_max_segment_size(q))
			goto new_segment;

		if (!BIOVEC_PHYS_MERGEABLE(*bvprv, bvec))
			goto new_segment;
		if (!BIOVEC_SEG_BOUNDARY(q, *bvprv, bvec))
			goto new_segment;

		(*sg)->length += nbytes;
	} else {
new_segment:
		if (!*sg)
			*sg = sglist;
		else {
			/*
			 * If the driver previously mapped a shorter
			 * list, we could see a termination bit
			 * prematurely unless it fully inits the sg
			 * table on each mapping. We KNOW that there
			 * must be more entries here or the driver
			 * would be buggy, so force clear the
			 * termination bit to avoid doing a full
			 * sg_init_table() in drivers for each command.
			 */
			(*sg)->page_link &= ~0x02;
			*sg = sg_next(*sg);
		}

		sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset);
		(*nsegs)++;
	}
	*bvprv = bvec;
}

/*
 * 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 bio_vec *bvec, *bvprv;
	struct req_iterator iter;
	struct scatterlist *sg;
	int nsegs, cluster;

	nsegs = 0;
	cluster = blk_queue_cluster(q);

	/*
	 * for each bio in rq
	 */
	bvprv = NULL;
	sg = NULL;
	rq_for_each_segment(bvec, rq, iter) {
		__blk_segment_map_sg(q, bvec, sglist, &bvprv, &sg,
				     &nsegs, &cluster);
	} /* segments in rq */


	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;
}
EXPORT_SYMBOL(blk_rq_map_sg);

/**
 * 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 bio_vec *bvec, *bvprv;
	struct scatterlist *sg;
	int nsegs, cluster;
	unsigned long i;

	nsegs = 0;
	cluster = blk_queue_cluster(q);

	bvprv = NULL;
	sg = NULL;
	bio_for_each_segment(bvec, bio, i) {
		__blk_segment_map_sg(q, bvec, sglist, &bvprv, &sg,
				     &nsegs, &cluster);
	} /* segments in bio */

	if (sg)
		sg_mark_end(sg);

	BUG_ON(bio->bi_phys_segments && nsegs > bio->bi_phys_segments);
	return nsegs;
}
EXPORT_SYMBOL(blk_bio_map_sg);

static inline int ll_new_hw_segment(struct request_queue *q,
				    struct request *req,
				    struct bio *bio)
{
	int nr_phys_segs = bio_phys_segments(q, bio);

	if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q))
		goto no_merge;

	if (bio_integrity(bio) && blk_integrity_merge_bio(q, req, bio))
		goto no_merge;

	/*
	 * This will form the start of a new hw segment.  Bump both
	 * counters.
	 */
	req->nr_phys_segments += nr_phys_segs;
	return 1;

no_merge:
	req->cmd_flags |= REQ_NOMERGE;
	if (req == q->last_merge)
		q->last_merge = NULL;
	return 0;
}

int ll_back_merge_fn(struct request_queue *q, struct request *req,
		     struct bio *bio)
{
	unsigned short max_sectors;

	if (unlikely(req->cmd_type == REQ_TYPE_BLOCK_PC))
		max_sectors = queue_max_hw_sectors(q);
	else
		max_sectors = queue_max_sectors(q);

	if (blk_rq_sectors(req) + bio_sectors(bio) > max_sectors) {
		req->cmd_flags |= REQ_NOMERGE;
		if (req == q->last_merge)
			q->last_merge = NULL;
		return 0;
	}
	if (!bio_flagged(req->biotail, BIO_SEG_VALID))
		blk_recount_segments(q, req->biotail);
	if (!bio_flagged(bio, BIO_SEG_VALID))
		blk_recount_segments(q, bio);

	return ll_new_hw_segment(q, req, bio);
}

int ll_front_merge_fn(struct request_queue *q, struct request *req,
		      struct bio *bio)
{
	unsigned short max_sectors;

	if (unlikely(req->cmd_type == REQ_TYPE_BLOCK_PC))
		max_sectors = queue_max_hw_sectors(q);
	else
		max_sectors = queue_max_sectors(q);


	if (blk_rq_sectors(req) + bio_sectors(bio) > max_sectors) {
		req->cmd_flags |= REQ_NOMERGE;
		if (req == q->last_merge)
			q->last_merge = NULL;
		return 0;
	}
	if (!bio_flagged(bio, BIO_SEG_VALID))
		blk_recount_segments(q, bio);
	if (!bio_flagged(req->bio, BIO_SEG_VALID))
		blk_recount_segments(q, req->bio);

	return ll_new_hw_segment(q, req, bio);
}

static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
				struct request *next)
{
	int total_phys_segments;
	unsigned int seg_size =
		req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size;

	/*
	 * First check if the either of the requests are re-queued
	 * requests.  Can't merge them if they are.
	 */
	if (req->special || next->special)
		return 0;

	/*
	 * Will it become too large?
	 */
	if ((blk_rq_sectors(req) + blk_rq_sectors(next)) > queue_max_sectors(q))
		return 0;

	total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
	if (blk_phys_contig_segment(q, req->biotail, next->bio)) {
		if (req->nr_phys_segments == 1)
			req->bio->bi_seg_front_size = seg_size;
		if (next->nr_phys_segments == 1)
			next->biotail->bi_seg_back_size = seg_size;
		total_phys_segments--;
	}

	if (total_phys_segments > queue_max_segments(q))
		return 0;

	if (blk_integrity_rq(req) && blk_integrity_merge_rq(q, req, next))
		return 0;

	/* Merge is OK... */
	req->nr_phys_segments = total_phys_segments;
	return 1;
}

/**
 * blk_rq_set_mixed_merge - mark a request as mixed merge
 * @rq: request to mark as mixed merge
 *
 * Description:
 *     @rq is about to be mixed merged.  Make sure the attributes
 *     which can be mixed are set in each bio and mark @rq as mixed
 *     merged.
 */
void blk_rq_set_mixed_merge(struct request *rq)
{
	unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
	struct bio *bio;

	if (rq->cmd_flags & REQ_MIXED_MERGE)
		return;

	/*
	 * @rq will no longer represent mixable attributes for all the
	 * contained bios.  It will just track those of the first one.
	 * Distributes the attributs to each bio.
	 */
	for (bio = rq->bio; bio; bio = bio->bi_next) {
		WARN_ON_ONCE((bio->bi_rw & REQ_FAILFAST_MASK) &&
			     (bio->bi_rw & REQ_FAILFAST_MASK) != ff);
		bio->bi_rw |= ff;
	}
	rq->cmd_flags |= REQ_MIXED_MERGE;
}

static void blk_account_io_merge(struct request *req)
{
	if (blk_do_io_stat(req)) {
		struct hd_struct *part;
		int cpu;

		cpu = part_stat_lock();
		part = req->part;

		part_round_stats(cpu, part);
		part_dec_in_flight(part, rq_data_dir(req));

		hd_struct_put(part);
		part_stat_unlock();
	}
}

/*
 * Has to be called with the request spinlock acquired
 */
static int attempt_merge(struct request_queue *q, struct request *req,
			  struct request *next)
{
	if (!rq_mergeable(req) || !rq_mergeable(next))
		return 0;

	/*
	 * not contiguous
	 */
	if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next))
		return 0;

	if (rq_data_dir(req) != rq_data_dir(next)
	    || req->rq_disk != next->rq_disk
	    || next->special)
		return 0;

	/*
	 * If we are allowed to merge, then append bio list
	 * from next to rq and release next. merge_requests_fn
	 * will have updated segment counts, update sector
	 * counts here.
	 */
	if (!ll_merge_requests_fn(q, req, next))
		return 0;

	/*
	 * If failfast settings disagree or any of the two is already
	 * a mixed merge, mark both as mixed before proceeding.  This
	 * makes sure that all involved bios have mixable attributes
	 * set properly.
	 */
	if ((req->cmd_flags | next->cmd_flags) & REQ_MIXED_MERGE ||
	    (req->cmd_flags & REQ_FAILFAST_MASK) !=
	    (next->cmd_flags & REQ_FAILFAST_MASK)) {
		blk_rq_set_mixed_merge(req);
		blk_rq_set_mixed_merge(next);
	}

	/*
	 * At this point we have either done a back merge
	 * or front merge. We need the smaller start_time of
	 * the merged requests to be the current request
	 * for accounting purposes.
	 */
	if (time_after(req->start_time, next->start_time))
		req->start_time = next->start_time;

	req->biotail->bi_next = next->bio;
	req->biotail = next->biotail;

	req->__data_len += blk_rq_bytes(next);

	elv_merge_requests(q, req, next);

	/*
	 * 'next' is going away, so update stats accordingly
	 */
	blk_account_io_merge(next);

	req->ioprio = ioprio_best(req->ioprio, next->ioprio);
	if (blk_rq_cpu_valid(next))
		req->cpu = next->cpu;

	/* owner-ship of bio passed from next to req */
	next->bio = NULL;
	__blk_put_request(q, next);
	return 1;
}

int attempt_back_merge(struct request_queue *q, struct request *rq)
{
	struct request *next = elv_latter_request(q, rq);

	if (next)
		return attempt_merge(q, rq, next);

	return 0;
}

int attempt_front_merge(struct request_queue *q, struct request *rq)
{
	struct request *prev = elv_former_request(q, rq);

	if (prev)
		return attempt_merge(q, prev, rq);

	return 0;
}

int blk_attempt_req_merge(struct request_queue *q, struct request *rq,
			  struct request *next)
{
	return attempt_merge(q, rq, next);
}

bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
{
	if (!rq_mergeable(rq) || !bio_mergeable(bio))
		return false;

	/* different data direction or already started, don't merge */
	if (bio_data_dir(bio) != rq_data_dir(rq))
		return false;

	/* must be same device and not a special request */
	if (rq->rq_disk != bio->bi_bdev->bd_disk || rq->special)
		return false;

	/* only merge integrity protected bio into ditto rq */
	if (bio_integrity(bio) != blk_integrity_rq(rq))
		return false;

	return true;
}

int blk_try_merge(struct request *rq, struct bio *bio)
{
	if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_sector)
		return ELEVATOR_BACK_MERGE;
	else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_sector)
		return ELEVATOR_FRONT_MERGE;
	return ELEVATOR_NO_MERGE;
}
Commit	Line	Data
d6d48196 JA	1	/*
	2	* Functions related to segment and merge handling
	3	*/
	4	#include <linux/kernel.h>
	5	#include <linux/module.h>
	6	#include <linux/bio.h>
	7	#include <linux/blkdev.h>
	8	#include <linux/scatterlist.h>
	9
	10	#include "blk.h"
	11
1e428079	12	static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
59247eae	13	struct bio *bio)
d6d48196	14	{
d6d48196	15	struct bio_vec bv, bvprv = NULL;
1e428079 JA	16	int cluster, i, high, highprv = 1;
1e428079 JA	17	unsigned int seg_size, nr_phys_segs;
59247eae	18	struct bio fbio, bbio;
d6d48196	19
1e428079 JA	20	if (!bio)
1e428079 JA	21	return 0;
d6d48196	22
1e428079	23	fbio = bio;
e692cb66	24	cluster = blk_queue_cluster(q);
5df97b91	25	seg_size = 0;
2c8919de	26	nr_phys_segs = 0;
1e428079 JA	27	for_each_bio(bio) {
	28	bio_for_each_segment(bv, bio, i) {
	29	/*
	30	* the trick here is making sure that a high page is
	31	* never considered part of another segment, since that
	32	* might change with the bounce page.
	33	*/
ae03bf63	34	high = page_to_pfn(bv->bv_page) > queue_bounce_pfn(q);
1e428079	35	if (high \|\| highprv)
d6d48196	36	goto new_segment;
1e428079	37	if (cluster) {
ae03bf63 MP	38	if (seg_size + bv->bv_len
ae03bf63 MP	39	> queue_max_segment_size(q))
1e428079 JA	40	goto new_segment;
	41	if (!BIOVEC_PHYS_MERGEABLE(bvprv, bv))
	42	goto new_segment;
	43	if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bv))
	44	goto new_segment;
d6d48196	45
1e428079 JA	46	seg_size += bv->bv_len;
	47	bvprv = bv;
	48	continue;
	49	}
d6d48196	50	new_segment:
1e428079 JA	51	if (nr_phys_segs == 1 && seg_size >
	52	fbio->bi_seg_front_size)
	53	fbio->bi_seg_front_size = seg_size;
86771427	54
1e428079 JA	55	nr_phys_segs++;
	56	bvprv = bv;
	57	seg_size = bv->bv_len;
	58	highprv = high;
	59	}
59247eae	60	bbio = bio;
d6d48196 JA	61	}
d6d48196 JA	62
59247eae JA	63	if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size)
	64	fbio->bi_seg_front_size = seg_size;
	65	if (seg_size > bbio->bi_seg_back_size)
	66	bbio->bi_seg_back_size = seg_size;
1e428079 JA	67
	68	return nr_phys_segs;
	69	}
	70
	71	void blk_recalc_rq_segments(struct request *rq)
	72	{
59247eae	73	rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio);
d6d48196 JA	74	}
	75
	76	void blk_recount_segments(struct request_queue q, struct bio bio)
	77	{
d6d48196	78	struct bio *nxt = bio->bi_next;
1e428079	79
d6d48196	80	bio->bi_next = NULL;
59247eae	81	bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio);
d6d48196	82	bio->bi_next = nxt;
d6d48196 JA	83	bio->bi_flags \|= (1 << BIO_SEG_VALID);
	84	}
	85	EXPORT_SYMBOL(blk_recount_segments);
	86
	87	static int blk_phys_contig_segment(struct request_queue q, struct bio bio,
	88	struct bio *nxt)
	89	{
e692cb66	90	if (!blk_queue_cluster(q))
d6d48196 JA	91	return 0;
d6d48196 JA	92
86771427	93	if (bio->bi_seg_back_size + nxt->bi_seg_front_size >
ae03bf63	94	queue_max_segment_size(q))
d6d48196 JA	95	return 0;
d6d48196 JA	96
e17fc0a1 DW	97	if (!bio_has_data(bio))
	98	return 1;
	99
	100	if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)))
	101	return 0;
	102
d6d48196	103	/*
e17fc0a1	104	* bio and nxt are contiguous in memory; check if the queue allows
d6d48196 JA	105	* these two to be merged into one
	106	*/
	107	if (BIO_SEG_BOUNDARY(q, bio, nxt))
	108	return 1;
	109
	110	return 0;
	111	}
	112
963ab9e5 AH	113	static void
	114	__blk_segment_map_sg(struct request_queue q, struct bio_vec bvec,
	115	struct scatterlist sglist, struct bio_vec *bvprv,
	116	struct scatterlist *sg, int nsegs, int *cluster)
	117	{
	118
	119	int nbytes = bvec->bv_len;
	120
	121	if (bvprv && cluster) {
	122	if ((*sg)->length + nbytes > queue_max_segment_size(q))
	123	goto new_segment;
	124
	125	if (!BIOVEC_PHYS_MERGEABLE(*bvprv, bvec))
	126	goto new_segment;
	127	if (!BIOVEC_SEG_BOUNDARY(q, *bvprv, bvec))
	128	goto new_segment;
	129
	130	(*sg)->length += nbytes;
	131	} else {
	132	new_segment:
	133	if (!*sg)
	134	*sg = sglist;
	135	else {
	136	/*
	137	* If the driver previously mapped a shorter
	138	* list, we could see a termination bit
	139	* prematurely unless it fully inits the sg
	140	* table on each mapping. We KNOW that there
	141	* must be more entries here or the driver
	142	* would be buggy, so force clear the
	143	* termination bit to avoid doing a full
	144	* sg_init_table() in drivers for each command.
	145	*/
	146	(*sg)->page_link &= ~0x02;
	147	sg = sg_next(sg);
	148	}
	149
	150	sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset);
	151	(*nsegs)++;
	152	}
	153	*bvprv = bvec;
	154	}
	155
d6d48196 JA	156	/*
	157	* map a request to scatterlist, return number of sg entries setup. Caller
	158	* must make sure sg can hold rq->nr_phys_segments entries
	159	*/
	160	int blk_rq_map_sg(struct request_queue q, struct request rq,
	161	struct scatterlist *sglist)
	162	{
	163	struct bio_vec bvec, bvprv;
	164	struct req_iterator iter;
	165	struct scatterlist *sg;
	166	int nsegs, cluster;
	167
	168	nsegs = 0;
e692cb66	169	cluster = blk_queue_cluster(q);
d6d48196 JA	170
	171	/*
	172	* for each bio in rq
	173	*/
	174	bvprv = NULL;
	175	sg = NULL;
	176	rq_for_each_segment(bvec, rq, iter) {
963ab9e5 AH	177	__blk_segment_map_sg(q, bvec, sglist, &bvprv, &sg,
963ab9e5 AH	178	&nsegs, &cluster);
d6d48196 JA	179	} /* segments in rq */
d6d48196 JA	180
f18573ab FT	181
f18573ab FT	182	if (unlikely(rq->cmd_flags & REQ_COPY_USER) &&
2e46e8b2 TH	183	(blk_rq_bytes(rq) & q->dma_pad_mask)) {
	184	unsigned int pad_len =
	185	(q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1;
f18573ab FT	186
	187	sg->length += pad_len;
	188	rq->extra_len += pad_len;
	189	}
	190
2fb98e84	191	if (q->dma_drain_size && q->dma_drain_needed(rq)) {
7b6d91da	192	if (rq->cmd_flags & REQ_WRITE)
db0a2e00 TH	193	memset(q->dma_drain_buffer, 0, q->dma_drain_size);
db0a2e00 TH	194
d6d48196 JA	195	sg->page_link &= ~0x02;
	196	sg = sg_next(sg);
	197	sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
	198	q->dma_drain_size,
	199	((unsigned long)q->dma_drain_buffer) &
	200	(PAGE_SIZE - 1));
	201	nsegs++;
7a85f889	202	rq->extra_len += q->dma_drain_size;
d6d48196 JA	203	}
	204
	205	if (sg)
	206	sg_mark_end(sg);
	207
	208	return nsegs;
	209	}
d6d48196 JA	210	EXPORT_SYMBOL(blk_rq_map_sg);
d6d48196 JA	211
85b9f66a AH	212	/**
	213	* blk_bio_map_sg - map a bio to a scatterlist
	214	* @q: request_queue in question
	215	* @bio: bio being mapped
	216	* @sglist: scatterlist being mapped
	217	*
	218	* Note:
	219	* Caller must make sure sg can hold bio->bi_phys_segments entries
	220	*
	221	* Will return the number of sg entries setup
	222	*/
	223	int blk_bio_map_sg(struct request_queue q, struct bio bio,
	224	struct scatterlist *sglist)
	225	{
	226	struct bio_vec bvec, bvprv;
	227	struct scatterlist *sg;
	228	int nsegs, cluster;
	229	unsigned long i;
	230
	231	nsegs = 0;
	232	cluster = blk_queue_cluster(q);
	233
	234	bvprv = NULL;
	235	sg = NULL;
	236	bio_for_each_segment(bvec, bio, i) {
	237	__blk_segment_map_sg(q, bvec, sglist, &bvprv, &sg,
	238	&nsegs, &cluster);
	239	} /* segments in bio */
	240
	241	if (sg)
	242	sg_mark_end(sg);
	243
	244	BUG_ON(bio->bi_phys_segments && nsegs > bio->bi_phys_segments);
	245	return nsegs;
	246	}
	247	EXPORT_SYMBOL(blk_bio_map_sg);
	248
d6d48196 JA	249	static inline int ll_new_hw_segment(struct request_queue *q,
	250	struct request *req,
	251	struct bio *bio)
	252	{
d6d48196 JA	253	int nr_phys_segs = bio_phys_segments(q, bio);
d6d48196 JA	254
13f05c8d MP	255	if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q))
	256	goto no_merge;
	257
	258	if (bio_integrity(bio) && blk_integrity_merge_bio(q, req, bio))
	259	goto no_merge;
d6d48196 JA	260
	261	/*
	262	* This will form the start of a new hw segment. Bump both
	263	* counters.
	264	*/
d6d48196 JA	265	req->nr_phys_segments += nr_phys_segs;
d6d48196 JA	266	return 1;
13f05c8d MP	267
	268	no_merge:
	269	req->cmd_flags \|= REQ_NOMERGE;
	270	if (req == q->last_merge)
	271	q->last_merge = NULL;
	272	return 0;
d6d48196 JA	273	}
	274
	275	int ll_back_merge_fn(struct request_queue q, struct request req,
	276	struct bio *bio)
	277	{
	278	unsigned short max_sectors;
d6d48196	279
33659ebb	280	if (unlikely(req->cmd_type == REQ_TYPE_BLOCK_PC))
ae03bf63	281	max_sectors = queue_max_hw_sectors(q);
d6d48196	282	else
ae03bf63	283	max_sectors = queue_max_sectors(q);
d6d48196	284
83096ebf	285	if (blk_rq_sectors(req) + bio_sectors(bio) > max_sectors) {
d6d48196 JA	286	req->cmd_flags \|= REQ_NOMERGE;
	287	if (req == q->last_merge)
	288	q->last_merge = NULL;
	289	return 0;
	290	}
2cdf79ca	291	if (!bio_flagged(req->biotail, BIO_SEG_VALID))
d6d48196	292	blk_recount_segments(q, req->biotail);
2cdf79ca	293	if (!bio_flagged(bio, BIO_SEG_VALID))
d6d48196	294	blk_recount_segments(q, bio);
d6d48196 JA	295
	296	return ll_new_hw_segment(q, req, bio);
	297	}
	298
6728cb0e	299	int ll_front_merge_fn(struct request_queue q, struct request req,
d6d48196 JA	300	struct bio *bio)
	301	{
	302	unsigned short max_sectors;
d6d48196	303
33659ebb	304	if (unlikely(req->cmd_type == REQ_TYPE_BLOCK_PC))
ae03bf63	305	max_sectors = queue_max_hw_sectors(q);
d6d48196	306	else
ae03bf63	307	max_sectors = queue_max_sectors(q);
d6d48196 JA	308
d6d48196 JA	309
83096ebf	310	if (blk_rq_sectors(req) + bio_sectors(bio) > max_sectors) {
d6d48196 JA	311	req->cmd_flags \|= REQ_NOMERGE;
	312	if (req == q->last_merge)
	313	q->last_merge = NULL;
	314	return 0;
	315	}
2cdf79ca	316	if (!bio_flagged(bio, BIO_SEG_VALID))
d6d48196	317	blk_recount_segments(q, bio);
2cdf79ca	318	if (!bio_flagged(req->bio, BIO_SEG_VALID))
d6d48196	319	blk_recount_segments(q, req->bio);
d6d48196 JA	320
	321	return ll_new_hw_segment(q, req, bio);
	322	}
	323
	324	static int ll_merge_requests_fn(struct request_queue q, struct request req,
	325	struct request *next)
	326	{
	327	int total_phys_segments;
86771427 FT	328	unsigned int seg_size =
86771427 FT	329	req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size;
d6d48196 JA	330
	331	/*
	332	* First check if the either of the requests are re-queued
	333	* requests. Can't merge them if they are.
	334	*/
	335	if (req->special \|\| next->special)
	336	return 0;
	337
	338	/*
	339	* Will it become too large?
	340	*/
ae03bf63	341	if ((blk_rq_sectors(req) + blk_rq_sectors(next)) > queue_max_sectors(q))
d6d48196 JA	342	return 0;
	343
	344	total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
86771427 FT	345	if (blk_phys_contig_segment(q, req->biotail, next->bio)) {
	346	if (req->nr_phys_segments == 1)
	347	req->bio->bi_seg_front_size = seg_size;
	348	if (next->nr_phys_segments == 1)
	349	next->biotail->bi_seg_back_size = seg_size;
d6d48196	350	total_phys_segments--;
86771427	351	}
d6d48196	352
8a78362c	353	if (total_phys_segments > queue_max_segments(q))
d6d48196 JA	354	return 0;
d6d48196 JA	355
13f05c8d MP	356	if (blk_integrity_rq(req) && blk_integrity_merge_rq(q, req, next))
	357	return 0;
	358
d6d48196 JA	359	/* Merge is OK... */
d6d48196 JA	360	req->nr_phys_segments = total_phys_segments;
d6d48196 JA	361	return 1;
	362	}
	363
80a761fd TH	364	/**
	365	* blk_rq_set_mixed_merge - mark a request as mixed merge
	366	* @rq: request to mark as mixed merge
	367	*
	368	* Description:
	369	* @rq is about to be mixed merged. Make sure the attributes
	370	* which can be mixed are set in each bio and mark @rq as mixed
	371	* merged.
	372	*/
	373	void blk_rq_set_mixed_merge(struct request *rq)
	374	{
	375	unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
	376	struct bio *bio;
	377
	378	if (rq->cmd_flags & REQ_MIXED_MERGE)
	379	return;
	380
	381	/*
	382	* @rq will no longer represent mixable attributes for all the
	383	* contained bios. It will just track those of the first one.
	384	* Distributes the attributs to each bio.
	385	*/
	386	for (bio = rq->bio; bio; bio = bio->bi_next) {
	387	WARN_ON_ONCE((bio->bi_rw & REQ_FAILFAST_MASK) &&
	388	(bio->bi_rw & REQ_FAILFAST_MASK) != ff);
	389	bio->bi_rw \|= ff;
	390	}
	391	rq->cmd_flags \|= REQ_MIXED_MERGE;
	392	}
	393
26308eab JM	394	static void blk_account_io_merge(struct request *req)
	395	{
	396	if (blk_do_io_stat(req)) {
	397	struct hd_struct *part;
	398	int cpu;
	399
	400	cpu = part_stat_lock();
09e099d4	401	part = req->part;
26308eab JM	402
26308eab JM	403	part_round_stats(cpu, part);
316d315b	404	part_dec_in_flight(part, rq_data_dir(req));
26308eab	405
6c23a968	406	hd_struct_put(part);
26308eab JM	407	part_stat_unlock();
	408	}
	409	}
	410
d6d48196 JA	411	/*
	412	* Has to be called with the request spinlock acquired
	413	*/
	414	static int attempt_merge(struct request_queue q, struct request req,
	415	struct request *next)
	416	{
	417	if (!rq_mergeable(req) \|\| !rq_mergeable(next))
	418	return 0;
	419
	420	/*
	421	* not contiguous
	422	*/
83096ebf	423	if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next))
d6d48196 JA	424	return 0;
	425
	426	if (rq_data_dir(req) != rq_data_dir(next)
	427	\|\| req->rq_disk != next->rq_disk
	428	\|\| next->special)
	429	return 0;
	430
	431	/*
	432	* If we are allowed to merge, then append bio list
	433	* from next to rq and release next. merge_requests_fn
	434	* will have updated segment counts, update sector
	435	* counts here.
	436	*/
	437	if (!ll_merge_requests_fn(q, req, next))
	438	return 0;
	439
80a761fd TH	440	/*
	441	* If failfast settings disagree or any of the two is already
	442	* a mixed merge, mark both as mixed before proceeding. This
	443	* makes sure that all involved bios have mixable attributes
	444	* set properly.
	445	*/
	446	if ((req->cmd_flags \| next->cmd_flags) & REQ_MIXED_MERGE \|\|
	447	(req->cmd_flags & REQ_FAILFAST_MASK) !=
	448	(next->cmd_flags & REQ_FAILFAST_MASK)) {
	449	blk_rq_set_mixed_merge(req);
	450	blk_rq_set_mixed_merge(next);
	451	}
	452
d6d48196 JA	453	/*
	454	* At this point we have either done a back merge
	455	* or front merge. We need the smaller start_time of
	456	* the merged requests to be the current request
	457	* for accounting purposes.
	458	*/
	459	if (time_after(req->start_time, next->start_time))
	460	req->start_time = next->start_time;
	461
	462	req->biotail->bi_next = next->bio;
	463	req->biotail = next->biotail;
	464
a2dec7b3	465	req->__data_len += blk_rq_bytes(next);
d6d48196 JA	466
	467	elv_merge_requests(q, req, next);
	468
42dad764 JM	469	/*
	470	* 'next' is going away, so update stats accordingly
	471	*/
	472	blk_account_io_merge(next);
d6d48196 JA	473
d6d48196 JA	474	req->ioprio = ioprio_best(req->ioprio, next->ioprio);
ab780f1e JA	475	if (blk_rq_cpu_valid(next))
ab780f1e JA	476	req->cpu = next->cpu;
d6d48196	477
1cd96c24 BH	478	/* owner-ship of bio passed from next to req */
1cd96c24 BH	479	next->bio = NULL;
d6d48196 JA	480	__blk_put_request(q, next);
	481	return 1;
	482	}
	483
	484	int attempt_back_merge(struct request_queue q, struct request rq)
	485	{
	486	struct request *next = elv_latter_request(q, rq);
	487
	488	if (next)
	489	return attempt_merge(q, rq, next);
	490
	491	return 0;
	492	}
	493
	494	int attempt_front_merge(struct request_queue q, struct request rq)
	495	{
	496	struct request *prev = elv_former_request(q, rq);
	497
	498	if (prev)
	499	return attempt_merge(q, prev, rq);
	500
	501	return 0;
	502	}
5e84ea3a JA	503
	504	int blk_attempt_req_merge(struct request_queue q, struct request rq,
	505	struct request *next)
	506	{
	507	return attempt_merge(q, rq, next);
	508	}
050c8ea8 TH	509
	510	bool blk_rq_merge_ok(struct request rq, struct bio bio)
	511	{
e2a60da7	512	if (!rq_mergeable(rq) \|\| !bio_mergeable(bio))
050c8ea8 TH	513	return false;
	514
	515	/* different data direction or already started, don't merge */
	516	if (bio_data_dir(bio) != rq_data_dir(rq))
	517	return false;
	518
	519	/* must be same device and not a special request */
	520	if (rq->rq_disk != bio->bi_bdev->bd_disk \|\| rq->special)
	521	return false;
	522
	523	/* only merge integrity protected bio into ditto rq */
	524	if (bio_integrity(bio) != blk_integrity_rq(rq))
	525	return false;
	526
	527	return true;
	528	}
	529
	530	int blk_try_merge(struct request rq, struct bio bio)
	531	{
	532	if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_sector)
	533	return ELEVATOR_BACK_MERGE;
	534	else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_sector)
	535	return ELEVATOR_FRONT_MERGE;
	536	return ELEVATOR_NO_MERGE;
	537	}