[people/ms/linux.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;
		}
	}
}

static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
					     struct bio *bio,
					     unsigned int *seg_size_ptr)
{
	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;

	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;
		}
	}

	if (seg_size_ptr)
		*seg_size_ptr = seg_size;

	return nr_phys_segs;
}

void blk_recalc_rq_segments(struct request *rq)
{
	unsigned int seg_size = 0, phys_segs;

	phys_segs = __blk_recalc_rq_segments(rq->q, rq->bio, &seg_size);

	if (phys_segs == 1 && seg_size > rq->bio->bi_seg_front_size)
		rq->bio->bi_seg_front_size = seg_size;
	if (seg_size > rq->biotail->bi_seg_back_size)
		rq->biotail->bi_seg_back_size = seg_size;

	rq->nr_phys_segments = phys_segs;
}

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, NULL);
	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) &&
	    (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_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;
	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 ((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)) {
		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;
}

/*
 * 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
1e428079 JA	41	static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
	42	struct bio *bio,
	43	unsigned int *seg_size_ptr)
d6d48196	44	{
d6d48196	45	unsigned int phys_size;
d6d48196	46	struct bio_vec bv, bvprv = NULL;
1e428079 JA	47	int cluster, i, high, highprv = 1;
	48	unsigned int seg_size, nr_phys_segs;
	49	struct bio *fbio;
d6d48196	50
1e428079 JA	51	if (!bio)
1e428079 JA	52	return 0;
d6d48196	53
1e428079	54	fbio = bio;
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;
1e428079 JA	58	for_each_bio(bio) {
	59	bio_for_each_segment(bv, bio, i) {
	60	/*
	61	* the trick here is making sure that a high page is
	62	* never considered part of another segment, since that
	63	* might change with the bounce page.
	64	*/
	65	high = page_to_pfn(bv->bv_page) > q->bounce_pfn;
	66	if (high \|\| highprv)
d6d48196	67	goto new_segment;
1e428079 JA	68	if (cluster) {
	69	if (seg_size + bv->bv_len > q->max_segment_size)
	70	goto new_segment;
	71	if (!BIOVEC_PHYS_MERGEABLE(bvprv, bv))
	72	goto new_segment;
	73	if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bv))
	74	goto new_segment;
d6d48196	75
1e428079 JA	76	seg_size += bv->bv_len;
	77	bvprv = bv;
	78	continue;
	79	}
d6d48196	80	new_segment:
1e428079 JA	81	if (nr_phys_segs == 1 && seg_size >
	82	fbio->bi_seg_front_size)
	83	fbio->bi_seg_front_size = seg_size;
86771427	84
1e428079 JA	85	nr_phys_segs++;
	86	bvprv = bv;
	87	seg_size = bv->bv_len;
	88	highprv = high;
	89	}
d6d48196 JA	90	}
d6d48196 JA	91
1e428079 JA	92	if (seg_size_ptr)
	93	*seg_size_ptr = seg_size;
	94
	95	return nr_phys_segs;
	96	}
	97
	98	void blk_recalc_rq_segments(struct request *rq)
	99	{
	100	unsigned int seg_size = 0, phys_segs;
	101
	102	phys_segs = __blk_recalc_rq_segments(rq->q, rq->bio, &seg_size);
	103
	104	if (phys_segs == 1 && seg_size > rq->bio->bi_seg_front_size)
86771427 FT	105	rq->bio->bi_seg_front_size = seg_size;
	106	if (seg_size > rq->biotail->bi_seg_back_size)
	107	rq->biotail->bi_seg_back_size = seg_size;
	108
1e428079	109	rq->nr_phys_segments = phys_segs;
d6d48196 JA	110	}
	111
	112	void blk_recount_segments(struct request_queue q, struct bio bio)
	113	{
d6d48196	114	struct bio *nxt = bio->bi_next;
1e428079	115
d6d48196	116	bio->bi_next = NULL;
1e428079	117	bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio, NULL);
d6d48196	118	bio->bi_next = nxt;
d6d48196 JA	119	bio->bi_flags \|= (1 << BIO_SEG_VALID);
	120	}
	121	EXPORT_SYMBOL(blk_recount_segments);
	122
	123	static int blk_phys_contig_segment(struct request_queue q, struct bio bio,
	124	struct bio *nxt)
	125	{
75ad23bc	126	if (!test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags))
d6d48196 JA	127	return 0;
d6d48196 JA	128
86771427 FT	129	if (bio->bi_seg_back_size + nxt->bi_seg_front_size >
86771427 FT	130	q->max_segment_size)
d6d48196 JA	131	return 0;
d6d48196 JA	132
e17fc0a1 DW	133	if (!bio_has_data(bio))
	134	return 1;
	135
	136	if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)))
	137	return 0;
	138
d6d48196	139	/*
e17fc0a1	140	* bio and nxt are contiguous in memory; check if the queue allows
d6d48196 JA	141	* these two to be merged into one
	142	*/
	143	if (BIO_SEG_BOUNDARY(q, bio, nxt))
	144	return 1;
	145
	146	return 0;
	147	}
	148
d6d48196 JA	149	/*
	150	* map a request to scatterlist, return number of sg entries setup. Caller
	151	* must make sure sg can hold rq->nr_phys_segments entries
	152	*/
	153	int blk_rq_map_sg(struct request_queue q, struct request rq,
	154	struct scatterlist *sglist)
	155	{
	156	struct bio_vec bvec, bvprv;
	157	struct req_iterator iter;
	158	struct scatterlist *sg;
	159	int nsegs, cluster;
	160
	161	nsegs = 0;
75ad23bc	162	cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
d6d48196 JA	163
	164	/*
	165	* for each bio in rq
	166	*/
	167	bvprv = NULL;
	168	sg = NULL;
	169	rq_for_each_segment(bvec, rq, iter) {
	170	int nbytes = bvec->bv_len;
	171
	172	if (bvprv && cluster) {
	173	if (sg->length + nbytes > q->max_segment_size)
	174	goto new_segment;
	175
	176	if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
	177	goto new_segment;
	178	if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
	179	goto new_segment;
	180
	181	sg->length += nbytes;
	182	} else {
	183	new_segment:
	184	if (!sg)
	185	sg = sglist;
	186	else {
	187	/*
	188	* If the driver previously mapped a shorter
	189	* list, we could see a termination bit
	190	* prematurely unless it fully inits the sg
	191	* table on each mapping. We KNOW that there
	192	* must be more entries here or the driver
	193	* would be buggy, so force clear the
	194	* termination bit to avoid doing a full
	195	* sg_init_table() in drivers for each command.
	196	*/
	197	sg->page_link &= ~0x02;
	198	sg = sg_next(sg);
	199	}
	200
	201	sg_set_page(sg, bvec->bv_page, nbytes, bvec->bv_offset);
	202	nsegs++;
	203	}
	204	bvprv = bvec;
	205	} /* segments in rq */
	206
f18573ab FT	207
	208	if (unlikely(rq->cmd_flags & REQ_COPY_USER) &&
	209	(rq->data_len & q->dma_pad_mask)) {
	210	unsigned int pad_len = (q->dma_pad_mask & ~rq->data_len) + 1;
	211
	212	sg->length += pad_len;
	213	rq->extra_len += pad_len;
	214	}
	215
2fb98e84	216	if (q->dma_drain_size && q->dma_drain_needed(rq)) {
db0a2e00 TH	217	if (rq->cmd_flags & REQ_RW)
	218	memset(q->dma_drain_buffer, 0, q->dma_drain_size);
	219
d6d48196 JA	220	sg->page_link &= ~0x02;
	221	sg = sg_next(sg);
	222	sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
	223	q->dma_drain_size,
	224	((unsigned long)q->dma_drain_buffer) &
	225	(PAGE_SIZE - 1));
	226	nsegs++;
7a85f889	227	rq->extra_len += q->dma_drain_size;
d6d48196 JA	228	}
	229
	230	if (sg)
	231	sg_mark_end(sg);
	232
	233	return nsegs;
	234	}
d6d48196 JA	235	EXPORT_SYMBOL(blk_rq_map_sg);
d6d48196 JA	236
d6d48196 JA	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;
86771427 FT	312	unsigned int seg_size =
86771427 FT	313	req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size;
d6d48196 JA	314
	315	/*
	316	* First check if the either of the requests are re-queued
	317	* requests. Can't merge them if they are.
	318	*/
	319	if (req->special \|\| next->special)
	320	return 0;
	321
	322	/*
	323	* Will it become too large?
	324	*/
	325	if ((req->nr_sectors + next->nr_sectors) > q->max_sectors)
	326	return 0;
	327
	328	total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
86771427 FT	329	if (blk_phys_contig_segment(q, req->biotail, next->bio)) {
	330	if (req->nr_phys_segments == 1)
	331	req->bio->bi_seg_front_size = seg_size;
	332	if (next->nr_phys_segments == 1)
	333	next->biotail->bi_seg_back_size = seg_size;
d6d48196	334	total_phys_segments--;
86771427	335	}
d6d48196 JA	336
	337	if (total_phys_segments > q->max_phys_segments)
	338	return 0;
	339
5df97b91	340	if (total_phys_segments > q->max_hw_segments)
d6d48196 JA	341	return 0;
	342
	343	/* Merge is OK... */
	344	req->nr_phys_segments = total_phys_segments;
d6d48196 JA	345	return 1;
	346	}
	347
	348	/*
	349	* Has to be called with the request spinlock acquired
	350	*/
	351	static int attempt_merge(struct request_queue q, struct request req,
	352	struct request *next)
	353	{
	354	if (!rq_mergeable(req) \|\| !rq_mergeable(next))
	355	return 0;
	356
	357	/*
	358	* not contiguous
	359	*/
	360	if (req->sector + req->nr_sectors != next->sector)
	361	return 0;
	362
	363	if (rq_data_dir(req) != rq_data_dir(next)
	364	\|\| req->rq_disk != next->rq_disk
	365	\|\| next->special)
	366	return 0;
	367
7ba1ba12 MP	368	if (blk_integrity_rq(req) != blk_integrity_rq(next))
	369	return 0;
	370
d6d48196 JA	371	/*
	372	* If we are allowed to merge, then append bio list
	373	* from next to rq and release next. merge_requests_fn
	374	* will have updated segment counts, update sector
	375	* counts here.
	376	*/
	377	if (!ll_merge_requests_fn(q, req, next))
	378	return 0;
	379
	380	/*
	381	* At this point we have either done a back merge
	382	* or front merge. We need the smaller start_time of
	383	* the merged requests to be the current request
	384	* for accounting purposes.
	385	*/
	386	if (time_after(req->start_time, next->start_time))
	387	req->start_time = next->start_time;
	388
	389	req->biotail->bi_next = next->bio;
	390	req->biotail = next->biotail;
	391
	392	req->nr_sectors = req->hard_nr_sectors += next->hard_nr_sectors;
	393
	394	elv_merge_requests(q, req, next);
	395
	396	if (req->rq_disk) {
e71bf0d0	397	struct hd_struct *part;
c9959059	398	int cpu;
e71bf0d0	399
074a7aca	400	cpu = part_stat_lock();
e71bf0d0	401	part = disk_map_sector_rcu(req->rq_disk, req->sector);
c9959059	402
074a7aca TH	403	part_round_stats(cpu, part);
074a7aca TH	404	part_dec_in_flight(part);
e71bf0d0	405
074a7aca	406	part_stat_unlock();
d6d48196 JA	407	}
	408
	409	req->ioprio = ioprio_best(req->ioprio, next->ioprio);
ab780f1e JA	410	if (blk_rq_cpu_valid(next))
ab780f1e JA	411	req->cpu = next->cpu;
d6d48196 JA	412
	413	__blk_put_request(q, next);
	414	return 1;
	415	}
	416
	417	int attempt_back_merge(struct request_queue q, struct request rq)
	418	{
	419	struct request *next = elv_latter_request(q, rq);
	420
	421	if (next)
	422	return attempt_merge(q, rq, next);
	423
	424	return 0;
	425	}
	426
	427	int attempt_front_merge(struct request_queue q, struct request rq)
	428	{
	429	struct request *prev = elv_former_request(q, rq);
	430
	431	if (prev)
	432	return attempt_merge(q, prev, rq);
	433
	434	return 0;
	435	}