[mirror_ubuntu-bionic-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"

void blk_recalc_rq_sectors(struct request *rq, int nsect)
{
	if (blk_fs_request(rq) || blk_discard_rq(rq)) {
		rq->hard_sector += nsect;
		rq->hard_nr_sectors -= nsect;

		/*
		 * Move the I/O submission pointers ahead if required.
		 */
		if ((rq->nr_sectors >= rq->hard_nr_sectors) &&
		    (rq->sector <= rq->hard_sector)) {
			rq->sector = rq->hard_sector;
			rq->nr_sectors = rq->hard_nr_sectors;
			rq->hard_cur_sectors = bio_cur_sectors(rq->bio);
			rq->current_nr_sectors = rq->hard_cur_sectors;
			rq->buffer = bio_data(rq->bio);
		}

		/*
		 * if total number of sectors is less than the first segment
		 * size, something has gone terribly wrong
		 */
		if (rq->nr_sectors < rq->current_nr_sectors) {
			printk(KERN_ERR "blk: request botched\n");
			rq->nr_sectors = rq->current_nr_sectors;
		}
	}
}

void blk_recalc_rq_segments(struct request *rq)
{
	int nr_phys_segs;
	unsigned int phys_size;
	struct bio_vec *bv, *bvprv = NULL;
	int seg_size;
	int cluster;
	struct req_iterator iter;
	int high, highprv = 1;
	struct request_queue *q = rq->q;

	if (!rq->bio)
		return;

	cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
	seg_size = 0;
	phys_size = nr_phys_segs = 0;
	rq_for_each_segment(bv, rq, iter) {
		/*
		 * 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) > q->bounce_pfn;
		if (high || highprv)
			goto new_segment;
		if (cluster) {
			if (seg_size + bv->bv_len > q->max_segment_size)
				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:
		nr_phys_segs++;
		bvprv = bv;
		seg_size = bv->bv_len;
		highprv = high;
	}

	rq->nr_phys_segments = nr_phys_segs;
}

void blk_recount_segments(struct request_queue *q, struct bio *bio)
{
	struct request rq;
	struct bio *nxt = bio->bi_next;
	rq.q = q;
	rq.bio = rq.biotail = bio;
	bio->bi_next = NULL;
	blk_recalc_rq_segments(&rq);
	bio->bi_next = nxt;
	bio->bi_phys_segments = rq.nr_phys_segments;
	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_size + nxt->bi_size > q->max_segment_size)
		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 > q->max_segment_size)
				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) &&
	    (rq->data_len & q->dma_pad_mask)) {
		unsigned int pad_len = (q->dma_pad_mask & ~rq->data_len) + 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_mergeable(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 > q->max_phys_segments) {
		req->cmd_flags |= REQ_NOMERGE;
		if (req == q->last_merge)
			q->last_merge = NULL;
		return 0;
	}

	/*
	 * A hw segment is just getting larger, bump just the phys
	 * counter.
	 */
	req->nr_phys_segments += nr_phys_segs;
	return 1;
}

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 > q->max_hw_segments
	    || req->nr_phys_segments + nr_phys_segs > q->max_phys_segments) {
		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(blk_pc_request(req)))
		max_sectors = q->max_hw_sectors;
	else
		max_sectors = q->max_sectors;

	if (req->nr_sectors + 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(blk_pc_request(req)))
		max_sectors = q->max_hw_sectors;
	else
		max_sectors = q->max_sectors;


	if (req->nr_sectors + 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;

	/*
	 * 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 ((req->nr_sectors + next->nr_sectors) > q->max_sectors)
		return 0;

	total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
	if (blk_phys_contig_segment(q, req->biotail, next->bio))
		total_phys_segments--;

	if (total_phys_segments > q->max_phys_segments)
		return 0;

	if (total_phys_segments > q->max_hw_segments)
		return 0;

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

/*
 * 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 (req->sector + req->nr_sectors != next->sector)
		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;

	/*
	 * 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->nr_sectors = req->hard_nr_sectors += next->hard_nr_sectors;

	elv_merge_requests(q, req, next);

	if (req->rq_disk) {
		struct hd_struct *part;
		int cpu;

		cpu = part_stat_lock();
		part = disk_map_sector_rcu(req->rq_disk, req->sector);

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

		part_stat_unlock();
	}

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

	__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
	12	void blk_recalc_rq_sectors(struct request *rq, int nsect)
	13	{
e17fc0a1	14	if (blk_fs_request(rq) \|\| blk_discard_rq(rq)) {
d6d48196 JA	15	rq->hard_sector += nsect;
	16	rq->hard_nr_sectors -= nsect;
	17
	18	/*
	19	* Move the I/O submission pointers ahead if required.
	20	*/
	21	if ((rq->nr_sectors >= rq->hard_nr_sectors) &&
	22	(rq->sector <= rq->hard_sector)) {
	23	rq->sector = rq->hard_sector;
	24	rq->nr_sectors = rq->hard_nr_sectors;
	25	rq->hard_cur_sectors = bio_cur_sectors(rq->bio);
	26	rq->current_nr_sectors = rq->hard_cur_sectors;
	27	rq->buffer = bio_data(rq->bio);
	28	}
	29
	30	/*
	31	* if total number of sectors is less than the first segment
	32	* size, something has gone terribly wrong
	33	*/
	34	if (rq->nr_sectors < rq->current_nr_sectors) {
6728cb0e	35	printk(KERN_ERR "blk: request botched\n");
d6d48196 JA	36	rq->nr_sectors = rq->current_nr_sectors;
	37	}
	38	}
	39	}
	40
	41	void blk_recalc_rq_segments(struct request *rq)
	42	{
	43	int nr_phys_segs;
d6d48196	44	unsigned int phys_size;
d6d48196 JA	45	struct bio_vec bv, bvprv = NULL;
d6d48196 JA	46	int seg_size;
d6d48196 JA	47	int cluster;
	48	struct req_iterator iter;
	49	int high, highprv = 1;
	50	struct request_queue *q = rq->q;
	51
	52	if (!rq->bio)
	53	return;
	54
75ad23bc	55	cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
5df97b91 MP	56	seg_size = 0;
5df97b91 MP	57	phys_size = nr_phys_segs = 0;
d6d48196 JA	58	rq_for_each_segment(bv, rq, iter) {
	59	/*
	60	* the trick here is making sure that a high page is never
	61	* considered part of another segment, since that might
	62	* change with the bounce page.
	63	*/
	64	high = page_to_pfn(bv->bv_page) > q->bounce_pfn;
	65	if (high \|\| highprv)
b8b3e16c	66	goto new_segment;
d6d48196 JA	67	if (cluster) {
	68	if (seg_size + bv->bv_len > q->max_segment_size)
	69	goto new_segment;
	70	if (!BIOVEC_PHYS_MERGEABLE(bvprv, bv))
	71	goto new_segment;
	72	if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bv))
	73	goto new_segment;
d6d48196 JA	74
d6d48196 JA	75	seg_size += bv->bv_len;
d6d48196 JA	76	bvprv = bv;
	77	continue;
	78	}
	79	new_segment:
d6d48196 JA	80	nr_phys_segs++;
	81	bvprv = bv;
	82	seg_size = bv->bv_len;
	83	highprv = high;
	84	}
	85
d6d48196	86	rq->nr_phys_segments = nr_phys_segs;
d6d48196 JA	87	}
	88
	89	void blk_recount_segments(struct request_queue q, struct bio bio)
	90	{
	91	struct request rq;
	92	struct bio *nxt = bio->bi_next;
	93	rq.q = q;
	94	rq.bio = rq.biotail = bio;
	95	bio->bi_next = NULL;
	96	blk_recalc_rq_segments(&rq);
	97	bio->bi_next = nxt;
	98	bio->bi_phys_segments = rq.nr_phys_segments;
d6d48196 JA	99	bio->bi_flags \|= (1 << BIO_SEG_VALID);
	100	}
	101	EXPORT_SYMBOL(blk_recount_segments);
	102
	103	static int blk_phys_contig_segment(struct request_queue q, struct bio bio,
	104	struct bio *nxt)
	105	{
75ad23bc	106	if (!test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags))
d6d48196 JA	107	return 0;
d6d48196 JA	108
d6d48196 JA	109	if (bio->bi_size + nxt->bi_size > q->max_segment_size)
	110	return 0;
	111
e17fc0a1 DW	112	if (!bio_has_data(bio))
	113	return 1;
	114
	115	if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)))
	116	return 0;
	117
d6d48196	118	/*
e17fc0a1	119	* bio and nxt are contiguous in memory; check if the queue allows
d6d48196 JA	120	* these two to be merged into one
	121	*/
	122	if (BIO_SEG_BOUNDARY(q, bio, nxt))
	123	return 1;
	124
	125	return 0;
	126	}
	127
d6d48196 JA	128	/*
	129	* map a request to scatterlist, return number of sg entries setup. Caller
	130	* must make sure sg can hold rq->nr_phys_segments entries
	131	*/
	132	int blk_rq_map_sg(struct request_queue q, struct request rq,
	133	struct scatterlist *sglist)
	134	{
	135	struct bio_vec bvec, bvprv;
	136	struct req_iterator iter;
	137	struct scatterlist *sg;
	138	int nsegs, cluster;
	139
	140	nsegs = 0;
75ad23bc	141	cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
d6d48196 JA	142
	143	/*
	144	* for each bio in rq
	145	*/
	146	bvprv = NULL;
	147	sg = NULL;
	148	rq_for_each_segment(bvec, rq, iter) {
	149	int nbytes = bvec->bv_len;
	150
	151	if (bvprv && cluster) {
	152	if (sg->length + nbytes > q->max_segment_size)
	153	goto new_segment;
	154
	155	if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
	156	goto new_segment;
	157	if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
	158	goto new_segment;
	159
	160	sg->length += nbytes;
	161	} else {
	162	new_segment:
	163	if (!sg)
	164	sg = sglist;
	165	else {
	166	/*
	167	* If the driver previously mapped a shorter
	168	* list, we could see a termination bit
	169	* prematurely unless it fully inits the sg
	170	* table on each mapping. We KNOW that there
	171	* must be more entries here or the driver
	172	* would be buggy, so force clear the
	173	* termination bit to avoid doing a full
	174	* sg_init_table() in drivers for each command.
	175	*/
	176	sg->page_link &= ~0x02;
	177	sg = sg_next(sg);
	178	}
	179
	180	sg_set_page(sg, bvec->bv_page, nbytes, bvec->bv_offset);
	181	nsegs++;
	182	}
	183	bvprv = bvec;
	184	} /* segments in rq */
	185
f18573ab FT	186
	187	if (unlikely(rq->cmd_flags & REQ_COPY_USER) &&
	188	(rq->data_len & q->dma_pad_mask)) {
	189	unsigned int pad_len = (q->dma_pad_mask & ~rq->data_len) + 1;
	190
	191	sg->length += pad_len;
	192	rq->extra_len += pad_len;
	193	}
	194
2fb98e84	195	if (q->dma_drain_size && q->dma_drain_needed(rq)) {
db0a2e00 TH	196	if (rq->cmd_flags & REQ_RW)
	197	memset(q->dma_drain_buffer, 0, q->dma_drain_size);
	198
d6d48196 JA	199	sg->page_link &= ~0x02;
	200	sg = sg_next(sg);
	201	sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
	202	q->dma_drain_size,
	203	((unsigned long)q->dma_drain_buffer) &
	204	(PAGE_SIZE - 1));
	205	nsegs++;
7a85f889	206	rq->extra_len += q->dma_drain_size;
d6d48196 JA	207	}
	208
	209	if (sg)
	210	sg_mark_end(sg);
	211
	212	return nsegs;
	213	}
d6d48196 JA	214	EXPORT_SYMBOL(blk_rq_map_sg);
	215
	216	static inline int ll_new_mergeable(struct request_queue *q,
	217	struct request *req,
	218	struct bio *bio)
	219	{
	220	int nr_phys_segs = bio_phys_segments(q, bio);
	221
	222	if (req->nr_phys_segments + nr_phys_segs > q->max_phys_segments) {
	223	req->cmd_flags \|= REQ_NOMERGE;
	224	if (req == q->last_merge)
	225	q->last_merge = NULL;
	226	return 0;
	227	}
	228
	229	/*
	230	* A hw segment is just getting larger, bump just the phys
	231	* counter.
	232	*/
	233	req->nr_phys_segments += nr_phys_segs;
	234	return 1;
	235	}
	236
	237	static inline int ll_new_hw_segment(struct request_queue *q,
	238	struct request *req,
	239	struct bio *bio)
	240	{
d6d48196 JA	241	int nr_phys_segs = bio_phys_segments(q, bio);
d6d48196 JA	242
5df97b91	243	if (req->nr_phys_segments + nr_phys_segs > q->max_hw_segments
d6d48196 JA	244	\|\| req->nr_phys_segments + nr_phys_segs > q->max_phys_segments) {
	245	req->cmd_flags \|= REQ_NOMERGE;
	246	if (req == q->last_merge)
	247	q->last_merge = NULL;
	248	return 0;
	249	}
	250
	251	/*
	252	* This will form the start of a new hw segment. Bump both
	253	* counters.
	254	*/
d6d48196 JA	255	req->nr_phys_segments += nr_phys_segs;
	256	return 1;
	257	}
	258
	259	int ll_back_merge_fn(struct request_queue q, struct request req,
	260	struct bio *bio)
	261	{
	262	unsigned short max_sectors;
d6d48196 JA	263
	264	if (unlikely(blk_pc_request(req)))
	265	max_sectors = q->max_hw_sectors;
	266	else
	267	max_sectors = q->max_sectors;
	268
	269	if (req->nr_sectors + bio_sectors(bio) > max_sectors) {
	270	req->cmd_flags \|= REQ_NOMERGE;
	271	if (req == q->last_merge)
	272	q->last_merge = NULL;
	273	return 0;
	274	}
2cdf79ca	275	if (!bio_flagged(req->biotail, BIO_SEG_VALID))
d6d48196	276	blk_recount_segments(q, req->biotail);
2cdf79ca	277	if (!bio_flagged(bio, BIO_SEG_VALID))
d6d48196	278	blk_recount_segments(q, bio);
d6d48196 JA	279
	280	return ll_new_hw_segment(q, req, bio);
	281	}
	282
6728cb0e	283	int ll_front_merge_fn(struct request_queue q, struct request req,
d6d48196 JA	284	struct bio *bio)
	285	{
	286	unsigned short max_sectors;
d6d48196 JA	287
	288	if (unlikely(blk_pc_request(req)))
	289	max_sectors = q->max_hw_sectors;
	290	else
	291	max_sectors = q->max_sectors;
	292
	293
	294	if (req->nr_sectors + bio_sectors(bio) > max_sectors) {
	295	req->cmd_flags \|= REQ_NOMERGE;
	296	if (req == q->last_merge)
	297	q->last_merge = NULL;
	298	return 0;
	299	}
2cdf79ca	300	if (!bio_flagged(bio, BIO_SEG_VALID))
d6d48196	301	blk_recount_segments(q, bio);
2cdf79ca	302	if (!bio_flagged(req->bio, BIO_SEG_VALID))
d6d48196	303	blk_recount_segments(q, req->bio);
d6d48196 JA	304
	305	return ll_new_hw_segment(q, req, bio);
	306	}
	307
	308	static int ll_merge_requests_fn(struct request_queue q, struct request req,
	309	struct request *next)
	310	{
	311	int total_phys_segments;
d6d48196 JA	312
	313	/*
	314	* First check if the either of the requests are re-queued
	315	* requests. Can't merge them if they are.
	316	*/
	317	if (req->special \|\| next->special)
	318	return 0;
	319
	320	/*
	321	* Will it become too large?
	322	*/
	323	if ((req->nr_sectors + next->nr_sectors) > q->max_sectors)
	324	return 0;
	325
	326	total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
	327	if (blk_phys_contig_segment(q, req->biotail, next->bio))
	328	total_phys_segments--;
	329
	330	if (total_phys_segments > q->max_phys_segments)
	331	return 0;
	332
5df97b91	333	if (total_phys_segments > q->max_hw_segments)
d6d48196 JA	334	return 0;
	335
	336	/* Merge is OK... */
	337	req->nr_phys_segments = total_phys_segments;
d6d48196 JA	338	return 1;
	339	}
	340
	341	/*
	342	* Has to be called with the request spinlock acquired
	343	*/
	344	static int attempt_merge(struct request_queue q, struct request req,
	345	struct request *next)
	346	{
	347	if (!rq_mergeable(req) \|\| !rq_mergeable(next))
	348	return 0;
	349
	350	/*
	351	* not contiguous
	352	*/
	353	if (req->sector + req->nr_sectors != next->sector)
	354	return 0;
	355
	356	if (rq_data_dir(req) != rq_data_dir(next)
	357	\|\| req->rq_disk != next->rq_disk
	358	\|\| next->special)
	359	return 0;
	360
7ba1ba12 MP	361	if (blk_integrity_rq(req) != blk_integrity_rq(next))
	362	return 0;
	363
d6d48196 JA	364	/*
	365	* If we are allowed to merge, then append bio list
	366	* from next to rq and release next. merge_requests_fn
	367	* will have updated segment counts, update sector
	368	* counts here.
	369	*/
	370	if (!ll_merge_requests_fn(q, req, next))
	371	return 0;
	372
	373	/*
	374	* At this point we have either done a back merge
	375	* or front merge. We need the smaller start_time of
	376	* the merged requests to be the current request
	377	* for accounting purposes.
	378	*/
	379	if (time_after(req->start_time, next->start_time))
	380	req->start_time = next->start_time;
	381
	382	req->biotail->bi_next = next->bio;
	383	req->biotail = next->biotail;
	384
	385	req->nr_sectors = req->hard_nr_sectors += next->hard_nr_sectors;
	386
	387	elv_merge_requests(q, req, next);
	388
	389	if (req->rq_disk) {
e71bf0d0	390	struct hd_struct *part;
c9959059	391	int cpu;
e71bf0d0	392
074a7aca	393	cpu = part_stat_lock();
e71bf0d0	394	part = disk_map_sector_rcu(req->rq_disk, req->sector);
c9959059	395
074a7aca TH	396	part_round_stats(cpu, part);
074a7aca TH	397	part_dec_in_flight(part);
e71bf0d0	398
074a7aca	399	part_stat_unlock();
d6d48196 JA	400	}
	401
	402	req->ioprio = ioprio_best(req->ioprio, next->ioprio);
ab780f1e JA	403	if (blk_rq_cpu_valid(next))
ab780f1e JA	404	req->cpu = next->cpu;
d6d48196 JA	405
	406	__blk_put_request(q, next);
	407	return 1;
	408	}
	409
	410	int attempt_back_merge(struct request_queue q, struct request rq)
	411	{
	412	struct request *next = elv_latter_request(q, rq);
	413
	414	if (next)
	415	return attempt_merge(q, rq, next);
	416
	417	return 0;
	418	}
	419
	420	int attempt_front_merge(struct request_queue q, struct request rq)
	421	{
	422	struct request *prev = elv_former_request(q, rq);
	423
	424	if (prev)
	425	return attempt_merge(q, prev, rq);
	426
	427	return 0;
	428	}