[GitHub/mt8127/android_kernel_alcatel_ttab.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) > 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:
			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 >
	    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) &&
	    (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 > 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 (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(blk_pc_request(req)))
		max_sectors = q->max_hw_sectors;
	else
		max_sectors = q->max_sectors;


	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)) > 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)) {
		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 > 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;
}

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);

		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;

	/*
	 * 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	*/
	35	high = page_to_pfn(bv->bv_page) > q->bounce_pfn;
	36	if (high \|\| highprv)
d6d48196	37	goto new_segment;
1e428079 JA	38	if (cluster) {
	39	if (seg_size + bv->bv_len > q->max_segment_size)
	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	{
75ad23bc	90	if (!test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags))
d6d48196 JA	91	return 0;
d6d48196 JA	92
86771427 FT	93	if (bio->bi_seg_back_size + nxt->bi_seg_front_size >
86771427 FT	94	q->max_segment_size)
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
d6d48196 JA	113	/*
	114	* map a request to scatterlist, return number of sg entries setup. Caller
	115	* must make sure sg can hold rq->nr_phys_segments entries
	116	*/
	117	int blk_rq_map_sg(struct request_queue q, struct request rq,
	118	struct scatterlist *sglist)
	119	{
	120	struct bio_vec bvec, bvprv;
	121	struct req_iterator iter;
	122	struct scatterlist *sg;
	123	int nsegs, cluster;
	124
	125	nsegs = 0;
75ad23bc	126	cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
d6d48196 JA	127
	128	/*
	129	* for each bio in rq
	130	*/
	131	bvprv = NULL;
	132	sg = NULL;
	133	rq_for_each_segment(bvec, rq, iter) {
	134	int nbytes = bvec->bv_len;
	135
	136	if (bvprv && cluster) {
	137	if (sg->length + nbytes > q->max_segment_size)
	138	goto new_segment;
	139
	140	if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
	141	goto new_segment;
	142	if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
	143	goto new_segment;
	144
	145	sg->length += nbytes;
	146	} else {
	147	new_segment:
	148	if (!sg)
	149	sg = sglist;
	150	else {
	151	/*
	152	* If the driver previously mapped a shorter
	153	* list, we could see a termination bit
	154	* prematurely unless it fully inits the sg
	155	* table on each mapping. We KNOW that there
	156	* must be more entries here or the driver
	157	* would be buggy, so force clear the
	158	* termination bit to avoid doing a full
	159	* sg_init_table() in drivers for each command.
	160	*/
	161	sg->page_link &= ~0x02;
	162	sg = sg_next(sg);
	163	}
	164
	165	sg_set_page(sg, bvec->bv_page, nbytes, bvec->bv_offset);
	166	nsegs++;
	167	}
	168	bvprv = bvec;
	169	} /* segments in rq */
	170
f18573ab FT	171
f18573ab FT	172	if (unlikely(rq->cmd_flags & REQ_COPY_USER) &&
2e46e8b2 TH	173	(blk_rq_bytes(rq) & q->dma_pad_mask)) {
	174	unsigned int pad_len =
	175	(q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1;
f18573ab FT	176
	177	sg->length += pad_len;
	178	rq->extra_len += pad_len;
	179	}
	180
2fb98e84	181	if (q->dma_drain_size && q->dma_drain_needed(rq)) {
db0a2e00 TH	182	if (rq->cmd_flags & REQ_RW)
	183	memset(q->dma_drain_buffer, 0, q->dma_drain_size);
	184
d6d48196 JA	185	sg->page_link &= ~0x02;
	186	sg = sg_next(sg);
	187	sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
	188	q->dma_drain_size,
	189	((unsigned long)q->dma_drain_buffer) &
	190	(PAGE_SIZE - 1));
	191	nsegs++;
7a85f889	192	rq->extra_len += q->dma_drain_size;
d6d48196 JA	193	}
	194
	195	if (sg)
	196	sg_mark_end(sg);
	197
	198	return nsegs;
	199	}
d6d48196 JA	200	EXPORT_SYMBOL(blk_rq_map_sg);
d6d48196 JA	201
d6d48196 JA	202	static inline int ll_new_hw_segment(struct request_queue *q,
	203	struct request *req,
	204	struct bio *bio)
	205	{
d6d48196 JA	206	int nr_phys_segs = bio_phys_segments(q, bio);
d6d48196 JA	207
5df97b91	208	if (req->nr_phys_segments + nr_phys_segs > q->max_hw_segments
d6d48196 JA	209	\|\| req->nr_phys_segments + nr_phys_segs > q->max_phys_segments) {
	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 JA	228
	229	if (unlikely(blk_pc_request(req)))
	230	max_sectors = q->max_hw_sectors;
	231	else
	232	max_sectors = q->max_sectors;
	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 JA	252
	253	if (unlikely(blk_pc_request(req)))
	254	max_sectors = q->max_hw_sectors;
	255	else
	256	max_sectors = q->max_sectors;
	257
	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	*/
83096ebf	290	if ((blk_rq_sectors(req) + blk_rq_sectors(next)) > q->max_sectors)
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 JA	301
	302	if (total_phys_segments > q->max_phys_segments)
	303	return 0;
	304
5df97b91	305	if (total_phys_segments > q->max_hw_segments)
d6d48196 JA	306	return 0;
	307
	308	/* Merge is OK... */
	309	req->nr_phys_segments = total_phys_segments;
d6d48196 JA	310	return 1;
	311	}
	312
26308eab JM	313	static void blk_account_io_merge(struct request *req)
	314	{
	315	if (blk_do_io_stat(req)) {
	316	struct hd_struct *part;
	317	int cpu;
	318
	319	cpu = part_stat_lock();
83096ebf	320	part = disk_map_sector_rcu(req->rq_disk, blk_rq_pos(req));
26308eab JM	321
	322	part_round_stats(cpu, part);
	323	part_dec_in_flight(part);
	324
	325	part_stat_unlock();
	326	}
	327	}
	328
d6d48196 JA	329	/*
	330	* Has to be called with the request spinlock acquired
	331	*/
	332	static int attempt_merge(struct request_queue q, struct request req,
	333	struct request *next)
	334	{
	335	if (!rq_mergeable(req) \|\| !rq_mergeable(next))
	336	return 0;
	337
	338	/*
	339	* not contiguous
	340	*/
83096ebf	341	if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next))
d6d48196 JA	342	return 0;
	343
	344	if (rq_data_dir(req) != rq_data_dir(next)
	345	\|\| req->rq_disk != next->rq_disk
	346	\|\| next->special)
	347	return 0;
	348
7ba1ba12 MP	349	if (blk_integrity_rq(req) != blk_integrity_rq(next))
	350	return 0;
	351
d6d48196 JA	352	/*
	353	* If we are allowed to merge, then append bio list
	354	* from next to rq and release next. merge_requests_fn
	355	* will have updated segment counts, update sector
	356	* counts here.
	357	*/
	358	if (!ll_merge_requests_fn(q, req, next))
	359	return 0;
	360
	361	/*
	362	* At this point we have either done a back merge
	363	* or front merge. We need the smaller start_time of
	364	* the merged requests to be the current request
	365	* for accounting purposes.
	366	*/
	367	if (time_after(req->start_time, next->start_time))
	368	req->start_time = next->start_time;
	369
	370	req->biotail->bi_next = next->bio;
	371	req->biotail = next->biotail;
	372
a2dec7b3	373	req->__data_len += blk_rq_bytes(next);
d6d48196 JA	374
	375	elv_merge_requests(q, req, next);
	376
42dad764 JM	377	/*
	378	* 'next' is going away, so update stats accordingly
	379	*/
	380	blk_account_io_merge(next);
d6d48196 JA	381
d6d48196 JA	382	req->ioprio = ioprio_best(req->ioprio, next->ioprio);
ab780f1e JA	383	if (blk_rq_cpu_valid(next))
ab780f1e JA	384	req->cpu = next->cpu;
d6d48196	385
1cd96c24 BH	386	/* owner-ship of bio passed from next to req */
1cd96c24 BH	387	next->bio = NULL;
d6d48196 JA	388	__blk_put_request(q, next);
	389	return 1;
	390	}
	391
	392	int attempt_back_merge(struct request_queue q, struct request rq)
	393	{
	394	struct request *next = elv_latter_request(q, rq);
	395
	396	if (next)
	397	return attempt_merge(q, rq, next);
	398
	399	return 0;
	400	}
	401
	402	int attempt_front_merge(struct request_queue q, struct request rq)
	403	{
	404	struct request *prev = elv_former_request(q, rq);
	405
	406	if (prev)
	407	return attempt_merge(q, prev, rq);
	408
	409	return 0;
	410	}