[linux-2.6-block.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)
{
	unsigned int phys_size;
	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 = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
	seg_size = 0;
	phys_size = 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 (!test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags))
		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;
}

/*
 * 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 = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);

	/*
	 * for each bio in rq
	 */
	bvprv = NULL;
	sg = NULL;
	rq_for_each_segment(bvec, rq, iter) {
		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;
	} /* 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_RW)
			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);

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

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

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;

	/* 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 = disk_map_sector_rcu(req->rq_disk, blk_rq_pos(req));

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

		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 (blk_integrity_rq(req) != blk_integrity_rq(next))
		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;
}
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	unsigned int phys_size;
d6d48196	16	struct bio_vec bv, bvprv = NULL;
1e428079 JA	17	int cluster, i, high, highprv = 1;
1e428079 JA	18	unsigned int seg_size, nr_phys_segs;
59247eae	19	struct bio fbio, bbio;
d6d48196	20
1e428079 JA	21	if (!bio)
1e428079 JA	22	return 0;
d6d48196	23
1e428079	24	fbio = bio;
75ad23bc	25	cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
5df97b91 MP	26	seg_size = 0;
5df97b91 MP	27	phys_size = nr_phys_segs = 0;
1e428079 JA	28	for_each_bio(bio) {
	29	bio_for_each_segment(bv, bio, i) {
	30	/*
	31	* the trick here is making sure that a high page is
	32	* never considered part of another segment, since that
	33	* might change with the bounce page.
	34	*/
ae03bf63	35	high = page_to_pfn(bv->bv_page) > queue_bounce_pfn(q);
1e428079	36	if (high \|\| highprv)
d6d48196	37	goto new_segment;
1e428079	38	if (cluster) {
ae03bf63 MP	39	if (seg_size + bv->bv_len
ae03bf63 MP	40	> queue_max_segment_size(q))
1e428079 JA	41	goto new_segment;
	42	if (!BIOVEC_PHYS_MERGEABLE(bvprv, bv))
	43	goto new_segment;
	44	if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bv))
	45	goto new_segment;
d6d48196	46
1e428079 JA	47	seg_size += bv->bv_len;
	48	bvprv = bv;
	49	continue;
	50	}
d6d48196	51	new_segment:
1e428079 JA	52	if (nr_phys_segs == 1 && seg_size >
	53	fbio->bi_seg_front_size)
	54	fbio->bi_seg_front_size = seg_size;
86771427	55
1e428079 JA	56	nr_phys_segs++;
	57	bvprv = bv;
	58	seg_size = bv->bv_len;
	59	highprv = high;
	60	}
59247eae	61	bbio = bio;
d6d48196 JA	62	}
d6d48196 JA	63
59247eae JA	64	if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size)
	65	fbio->bi_seg_front_size = seg_size;
	66	if (seg_size > bbio->bi_seg_back_size)
	67	bbio->bi_seg_back_size = seg_size;
1e428079 JA	68
	69	return nr_phys_segs;
	70	}
	71
	72	void blk_recalc_rq_segments(struct request *rq)
	73	{
59247eae	74	rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio);
d6d48196 JA	75	}
	76
	77	void blk_recount_segments(struct request_queue q, struct bio bio)
	78	{
d6d48196	79	struct bio *nxt = bio->bi_next;
1e428079	80
d6d48196	81	bio->bi_next = NULL;
59247eae	82	bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio);
d6d48196	83	bio->bi_next = nxt;
d6d48196 JA	84	bio->bi_flags \|= (1 << BIO_SEG_VALID);
	85	}
	86	EXPORT_SYMBOL(blk_recount_segments);
	87
	88	static int blk_phys_contig_segment(struct request_queue q, struct bio bio,
	89	struct bio *nxt)
	90	{
75ad23bc	91	if (!test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags))
d6d48196 JA	92	return 0;
d6d48196 JA	93
86771427	94	if (bio->bi_seg_back_size + nxt->bi_seg_front_size >
ae03bf63	95	queue_max_segment_size(q))
d6d48196 JA	96	return 0;
d6d48196 JA	97
e17fc0a1 DW	98	if (!bio_has_data(bio))
	99	return 1;
	100
	101	if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)))
	102	return 0;
	103
d6d48196	104	/*
e17fc0a1	105	* bio and nxt are contiguous in memory; check if the queue allows
d6d48196 JA	106	* these two to be merged into one
	107	*/
	108	if (BIO_SEG_BOUNDARY(q, bio, nxt))
	109	return 1;
	110
	111	return 0;
	112	}
	113
d6d48196 JA	114	/*
	115	* map a request to scatterlist, return number of sg entries setup. Caller
	116	* must make sure sg can hold rq->nr_phys_segments entries
	117	*/
	118	int blk_rq_map_sg(struct request_queue q, struct request rq,
	119	struct scatterlist *sglist)
	120	{
	121	struct bio_vec bvec, bvprv;
	122	struct req_iterator iter;
	123	struct scatterlist *sg;
	124	int nsegs, cluster;
	125
	126	nsegs = 0;
75ad23bc	127	cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
d6d48196 JA	128
	129	/*
	130	* for each bio in rq
	131	*/
	132	bvprv = NULL;
	133	sg = NULL;
	134	rq_for_each_segment(bvec, rq, iter) {
	135	int nbytes = bvec->bv_len;
	136
	137	if (bvprv && cluster) {
ae03bf63	138	if (sg->length + nbytes > queue_max_segment_size(q))
d6d48196 JA	139	goto new_segment;
	140
	141	if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
	142	goto new_segment;
	143	if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
	144	goto new_segment;
	145
	146	sg->length += nbytes;
	147	} else {
	148	new_segment:
	149	if (!sg)
	150	sg = sglist;
	151	else {
	152	/*
	153	* If the driver previously mapped a shorter
	154	* list, we could see a termination bit
	155	* prematurely unless it fully inits the sg
	156	* table on each mapping. We KNOW that there
	157	* must be more entries here or the driver
	158	* would be buggy, so force clear the
	159	* termination bit to avoid doing a full
	160	* sg_init_table() in drivers for each command.
	161	*/
	162	sg->page_link &= ~0x02;
	163	sg = sg_next(sg);
	164	}
	165
	166	sg_set_page(sg, bvec->bv_page, nbytes, bvec->bv_offset);
	167	nsegs++;
	168	}
	169	bvprv = bvec;
	170	} /* segments in rq */
	171
f18573ab FT	172
f18573ab FT	173	if (unlikely(rq->cmd_flags & REQ_COPY_USER) &&
2e46e8b2 TH	174	(blk_rq_bytes(rq) & q->dma_pad_mask)) {
	175	unsigned int pad_len =
	176	(q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1;
f18573ab FT	177
	178	sg->length += pad_len;
	179	rq->extra_len += pad_len;
	180	}
	181
2fb98e84	182	if (q->dma_drain_size && q->dma_drain_needed(rq)) {
db0a2e00 TH	183	if (rq->cmd_flags & REQ_RW)
	184	memset(q->dma_drain_buffer, 0, q->dma_drain_size);
	185
d6d48196 JA	186	sg->page_link &= ~0x02;
	187	sg = sg_next(sg);
	188	sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
	189	q->dma_drain_size,
	190	((unsigned long)q->dma_drain_buffer) &
	191	(PAGE_SIZE - 1));
	192	nsegs++;
7a85f889	193	rq->extra_len += q->dma_drain_size;
d6d48196 JA	194	}
	195
	196	if (sg)
	197	sg_mark_end(sg);
	198
	199	return nsegs;
	200	}
d6d48196 JA	201	EXPORT_SYMBOL(blk_rq_map_sg);
d6d48196 JA	202
d6d48196 JA	203	static inline int ll_new_hw_segment(struct request_queue *q,
	204	struct request *req,
	205	struct bio *bio)
	206	{
d6d48196 JA	207	int nr_phys_segs = bio_phys_segments(q, bio);
d6d48196 JA	208
8a78362c	209	if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q)) {
d6d48196 JA	210	req->cmd_flags \|= REQ_NOMERGE;
	211	if (req == q->last_merge)
	212	q->last_merge = NULL;
	213	return 0;
	214	}
	215
	216	/*
	217	* This will form the start of a new hw segment. Bump both
	218	* counters.
	219	*/
d6d48196 JA	220	req->nr_phys_segments += nr_phys_segs;
	221	return 1;
	222	}
	223
	224	int ll_back_merge_fn(struct request_queue q, struct request req,
	225	struct bio *bio)
	226	{
	227	unsigned short max_sectors;
d6d48196	228
33659ebb	229	if (unlikely(req->cmd_type == REQ_TYPE_BLOCK_PC))
ae03bf63	230	max_sectors = queue_max_hw_sectors(q);
d6d48196	231	else
ae03bf63	232	max_sectors = queue_max_sectors(q);
d6d48196	233
83096ebf	234	if (blk_rq_sectors(req) + bio_sectors(bio) > max_sectors) {
d6d48196 JA	235	req->cmd_flags \|= REQ_NOMERGE;
	236	if (req == q->last_merge)
	237	q->last_merge = NULL;
	238	return 0;
	239	}
2cdf79ca	240	if (!bio_flagged(req->biotail, BIO_SEG_VALID))
d6d48196	241	blk_recount_segments(q, req->biotail);
2cdf79ca	242	if (!bio_flagged(bio, BIO_SEG_VALID))
d6d48196	243	blk_recount_segments(q, bio);
d6d48196 JA	244
	245	return ll_new_hw_segment(q, req, bio);
	246	}
	247
6728cb0e	248	int ll_front_merge_fn(struct request_queue q, struct request req,
d6d48196 JA	249	struct bio *bio)
	250	{
	251	unsigned short max_sectors;
d6d48196	252
33659ebb	253	if (unlikely(req->cmd_type == REQ_TYPE_BLOCK_PC))
ae03bf63	254	max_sectors = queue_max_hw_sectors(q);
d6d48196	255	else
ae03bf63	256	max_sectors = queue_max_sectors(q);
d6d48196 JA	257
d6d48196 JA	258
83096ebf	259	if (blk_rq_sectors(req) + bio_sectors(bio) > max_sectors) {
d6d48196 JA	260	req->cmd_flags \|= REQ_NOMERGE;
	261	if (req == q->last_merge)
	262	q->last_merge = NULL;
	263	return 0;
	264	}
2cdf79ca	265	if (!bio_flagged(bio, BIO_SEG_VALID))
d6d48196	266	blk_recount_segments(q, bio);
2cdf79ca	267	if (!bio_flagged(req->bio, BIO_SEG_VALID))
d6d48196	268	blk_recount_segments(q, req->bio);
d6d48196 JA	269
	270	return ll_new_hw_segment(q, req, bio);
	271	}
	272
	273	static int ll_merge_requests_fn(struct request_queue q, struct request req,
	274	struct request *next)
	275	{
	276	int total_phys_segments;
86771427 FT	277	unsigned int seg_size =
86771427 FT	278	req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size;
d6d48196 JA	279
	280	/*
	281	* First check if the either of the requests are re-queued
	282	* requests. Can't merge them if they are.
	283	*/
	284	if (req->special \|\| next->special)
	285	return 0;
	286
	287	/*
	288	* Will it become too large?
	289	*/
ae03bf63	290	if ((blk_rq_sectors(req) + blk_rq_sectors(next)) > queue_max_sectors(q))
d6d48196 JA	291	return 0;
	292
	293	total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
86771427 FT	294	if (blk_phys_contig_segment(q, req->biotail, next->bio)) {
	295	if (req->nr_phys_segments == 1)
	296	req->bio->bi_seg_front_size = seg_size;
	297	if (next->nr_phys_segments == 1)
	298	next->biotail->bi_seg_back_size = seg_size;
d6d48196	299	total_phys_segments--;
86771427	300	}
d6d48196	301
8a78362c	302	if (total_phys_segments > queue_max_segments(q))
d6d48196 JA	303	return 0;
	304
	305	/* Merge is OK... */
	306	req->nr_phys_segments = total_phys_segments;
d6d48196 JA	307	return 1;
	308	}
	309
80a761fd TH	310	/**
	311	* blk_rq_set_mixed_merge - mark a request as mixed merge
	312	* @rq: request to mark as mixed merge
	313	*
	314	* Description:
	315	* @rq is about to be mixed merged. Make sure the attributes
	316	* which can be mixed are set in each bio and mark @rq as mixed
	317	* merged.
	318	*/
	319	void blk_rq_set_mixed_merge(struct request *rq)
	320	{
	321	unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
	322	struct bio *bio;
	323
	324	if (rq->cmd_flags & REQ_MIXED_MERGE)
	325	return;
	326
	327	/*
	328	* @rq will no longer represent mixable attributes for all the
	329	* contained bios. It will just track those of the first one.
	330	* Distributes the attributs to each bio.
	331	*/
	332	for (bio = rq->bio; bio; bio = bio->bi_next) {
	333	WARN_ON_ONCE((bio->bi_rw & REQ_FAILFAST_MASK) &&
	334	(bio->bi_rw & REQ_FAILFAST_MASK) != ff);
	335	bio->bi_rw \|= ff;
	336	}
	337	rq->cmd_flags \|= REQ_MIXED_MERGE;
	338	}
	339
26308eab JM	340	static void blk_account_io_merge(struct request *req)
	341	{
	342	if (blk_do_io_stat(req)) {
	343	struct hd_struct *part;
	344	int cpu;
	345
	346	cpu = part_stat_lock();
83096ebf	347	part = disk_map_sector_rcu(req->rq_disk, blk_rq_pos(req));
26308eab JM	348
26308eab JM	349	part_round_stats(cpu, part);
316d315b	350	part_dec_in_flight(part, rq_data_dir(req));
26308eab JM	351
	352	part_stat_unlock();
	353	}
	354	}
	355
d6d48196 JA	356	/*
	357	* Has to be called with the request spinlock acquired
	358	*/
	359	static int attempt_merge(struct request_queue q, struct request req,
	360	struct request *next)
	361	{
	362	if (!rq_mergeable(req) \|\| !rq_mergeable(next))
	363	return 0;
	364
	365	/*
	366	* not contiguous
	367	*/
83096ebf	368	if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next))
d6d48196 JA	369	return 0;
	370
	371	if (rq_data_dir(req) != rq_data_dir(next)
	372	\|\| req->rq_disk != next->rq_disk
	373	\|\| next->special)
	374	return 0;
	375
7ba1ba12 MP	376	if (blk_integrity_rq(req) != blk_integrity_rq(next))
	377	return 0;
	378
d6d48196 JA	379	/*
	380	* If we are allowed to merge, then append bio list
	381	* from next to rq and release next. merge_requests_fn
	382	* will have updated segment counts, update sector
	383	* counts here.
	384	*/
	385	if (!ll_merge_requests_fn(q, req, next))
	386	return 0;
	387
80a761fd TH	388	/*
	389	* If failfast settings disagree or any of the two is already
	390	* a mixed merge, mark both as mixed before proceeding. This
	391	* makes sure that all involved bios have mixable attributes
	392	* set properly.
	393	*/
	394	if ((req->cmd_flags \| next->cmd_flags) & REQ_MIXED_MERGE \|\|
	395	(req->cmd_flags & REQ_FAILFAST_MASK) !=
	396	(next->cmd_flags & REQ_FAILFAST_MASK)) {
	397	blk_rq_set_mixed_merge(req);
	398	blk_rq_set_mixed_merge(next);
	399	}
	400
d6d48196 JA	401	/*
	402	* At this point we have either done a back merge
	403	* or front merge. We need the smaller start_time of
	404	* the merged requests to be the current request
	405	* for accounting purposes.
	406	*/
	407	if (time_after(req->start_time, next->start_time))
	408	req->start_time = next->start_time;
	409
	410	req->biotail->bi_next = next->bio;
	411	req->biotail = next->biotail;
	412
a2dec7b3	413	req->__data_len += blk_rq_bytes(next);
d6d48196 JA	414
	415	elv_merge_requests(q, req, next);
	416
42dad764 JM	417	/*
	418	* 'next' is going away, so update stats accordingly
	419	*/
	420	blk_account_io_merge(next);
d6d48196 JA	421
d6d48196 JA	422	req->ioprio = ioprio_best(req->ioprio, next->ioprio);
ab780f1e JA	423	if (blk_rq_cpu_valid(next))
ab780f1e JA	424	req->cpu = next->cpu;
d6d48196	425
1cd96c24 BH	426	/* owner-ship of bio passed from next to req */
1cd96c24 BH	427	next->bio = NULL;
d6d48196 JA	428	__blk_put_request(q, next);
	429	return 1;
	430	}
	431
	432	int attempt_back_merge(struct request_queue q, struct request rq)
	433	{
	434	struct request *next = elv_latter_request(q, rq);
	435
	436	if (next)
	437	return attempt_merge(q, rq, next);
	438
	439	return 0;
	440	}
	441
	442	int attempt_front_merge(struct request_queue q, struct request rq)
	443	{
	444	struct request *prev = elv_former_request(q, rq);
	445
	446	if (prev)
	447	return attempt_merge(q, prev, rq);
	448
	449	return 0;
	450	}