[net-next-2.6.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;
	int nr_hw_segs;
	unsigned int phys_size;
	unsigned int hw_size;
	struct bio_vec *bv, *bvprv = NULL;
	int seg_size;
	int hw_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);
	hw_seg_size = seg_size = 0;
	phys_size = hw_size = nr_phys_segs = nr_hw_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;
			hw_seg_size += bv->bv_len;
			bvprv = bv;
			continue;
		}
new_segment:
		if (nr_hw_segs == 1 &&
		    hw_seg_size > rq->bio->bi_hw_front_size)
			rq->bio->bi_hw_front_size = hw_seg_size;
		hw_seg_size = bv->bv_len;
		nr_hw_segs++;

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

	if (nr_hw_segs == 1 &&
	    hw_seg_size > rq->bio->bi_hw_front_size)
		rq->bio->bi_hw_front_size = hw_seg_size;
	if (hw_seg_size > rq->biotail->bi_hw_back_size)
		rq->biotail->bi_hw_back_size = hw_seg_size;
	rq->nr_phys_segments = nr_phys_segs;
	rq->nr_hw_segments = nr_hw_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_hw_segments = rq.nr_hw_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_hw_segs = bio_hw_segments(q, bio);
	int nr_phys_segs = bio_phys_segments(q, bio);

	if (req->nr_hw_segments + nr_hw_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_hw_segments += nr_hw_segs;
	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;
	int total_hw_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;

	total_hw_segments = req->nr_hw_segments + next->nr_hw_segments;

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

	/* Merge is OK... */
	req->nr_phys_segments = total_phys_segments;
	req->nr_hw_segments = total_hw_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
			= get_part(req->rq_disk, req->sector);
		disk_round_stats(req->rq_disk);
		req->rq_disk->in_flight--;
		if (part) {
			part_round_stats(part);
			part->in_flight--;
		}
	}

	req->ioprio = ioprio_best(req->ioprio, next->ioprio);

	__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;
	44	int nr_hw_segs;
	45	unsigned int phys_size;
	46	unsigned int hw_size;
	47	struct bio_vec bv, bvprv = NULL;
	48	int seg_size;
	49	int hw_seg_size;
	50	int cluster;
	51	struct req_iterator iter;
	52	int high, highprv = 1;
	53	struct request_queue *q = rq->q;
	54
	55	if (!rq->bio)
	56	return;
	57
75ad23bc	58	cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
d6d48196 JA	59	hw_seg_size = seg_size = 0;
	60	phys_size = hw_size = nr_phys_segs = nr_hw_segs = 0;
	61	rq_for_each_segment(bv, rq, iter) {
	62	/*
	63	* the trick here is making sure that a high page is never
	64	* considered part of another segment, since that might
	65	* change with the bounce page.
	66	*/
	67	high = page_to_pfn(bv->bv_page) > q->bounce_pfn;
	68	if (high \|\| highprv)
b8b3e16c	69	goto new_segment;
d6d48196 JA	70	if (cluster) {
	71	if (seg_size + bv->bv_len > q->max_segment_size)
	72	goto new_segment;
	73	if (!BIOVEC_PHYS_MERGEABLE(bvprv, bv))
	74	goto new_segment;
	75	if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bv))
	76	goto new_segment;
d6d48196 JA	77
	78	seg_size += bv->bv_len;
	79	hw_seg_size += bv->bv_len;
	80	bvprv = bv;
	81	continue;
	82	}
	83	new_segment:
b8b3e16c MP	84	if (nr_hw_segs == 1 &&
	85	hw_seg_size > rq->bio->bi_hw_front_size)
	86	rq->bio->bi_hw_front_size = hw_seg_size;
	87	hw_seg_size = bv->bv_len;
	88	nr_hw_segs++;
d6d48196 JA	89
	90	nr_phys_segs++;
	91	bvprv = bv;
	92	seg_size = bv->bv_len;
	93	highprv = high;
	94	}
	95
	96	if (nr_hw_segs == 1 &&
	97	hw_seg_size > rq->bio->bi_hw_front_size)
	98	rq->bio->bi_hw_front_size = hw_seg_size;
	99	if (hw_seg_size > rq->biotail->bi_hw_back_size)
	100	rq->biotail->bi_hw_back_size = hw_seg_size;
	101	rq->nr_phys_segments = nr_phys_segs;
	102	rq->nr_hw_segments = nr_hw_segs;
	103	}
	104
	105	void blk_recount_segments(struct request_queue q, struct bio bio)
	106	{
	107	struct request rq;
	108	struct bio *nxt = bio->bi_next;
	109	rq.q = q;
	110	rq.bio = rq.biotail = bio;
	111	bio->bi_next = NULL;
	112	blk_recalc_rq_segments(&rq);
	113	bio->bi_next = nxt;
	114	bio->bi_phys_segments = rq.nr_phys_segments;
	115	bio->bi_hw_segments = rq.nr_hw_segments;
	116	bio->bi_flags \|= (1 << BIO_SEG_VALID);
	117	}
	118	EXPORT_SYMBOL(blk_recount_segments);
	119
	120	static int blk_phys_contig_segment(struct request_queue q, struct bio bio,
	121	struct bio *nxt)
	122	{
75ad23bc	123	if (!test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags))
d6d48196 JA	124	return 0;
d6d48196 JA	125
d6d48196 JA	126	if (bio->bi_size + nxt->bi_size > q->max_segment_size)
	127	return 0;
	128
e17fc0a1 DW	129	if (!bio_has_data(bio))
	130	return 1;
	131
	132	if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)))
	133	return 0;
	134
d6d48196	135	/*
e17fc0a1	136	* bio and nxt are contiguous in memory; check if the queue allows
d6d48196 JA	137	* these two to be merged into one
	138	*/
	139	if (BIO_SEG_BOUNDARY(q, bio, nxt))
	140	return 1;
	141
	142	return 0;
	143	}
	144
d6d48196 JA	145	/*
	146	* map a request to scatterlist, return number of sg entries setup. Caller
	147	* must make sure sg can hold rq->nr_phys_segments entries
	148	*/
	149	int blk_rq_map_sg(struct request_queue q, struct request rq,
	150	struct scatterlist *sglist)
	151	{
	152	struct bio_vec bvec, bvprv;
	153	struct req_iterator iter;
	154	struct scatterlist *sg;
	155	int nsegs, cluster;
	156
	157	nsegs = 0;
75ad23bc	158	cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
d6d48196 JA	159
	160	/*
	161	* for each bio in rq
	162	*/
	163	bvprv = NULL;
	164	sg = NULL;
	165	rq_for_each_segment(bvec, rq, iter) {
	166	int nbytes = bvec->bv_len;
	167
	168	if (bvprv && cluster) {
	169	if (sg->length + nbytes > q->max_segment_size)
	170	goto new_segment;
	171
	172	if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
	173	goto new_segment;
	174	if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
	175	goto new_segment;
	176
	177	sg->length += nbytes;
	178	} else {
	179	new_segment:
	180	if (!sg)
	181	sg = sglist;
	182	else {
	183	/*
	184	* If the driver previously mapped a shorter
	185	* list, we could see a termination bit
	186	* prematurely unless it fully inits the sg
	187	* table on each mapping. We KNOW that there
	188	* must be more entries here or the driver
	189	* would be buggy, so force clear the
	190	* termination bit to avoid doing a full
	191	* sg_init_table() in drivers for each command.
	192	*/
	193	sg->page_link &= ~0x02;
	194	sg = sg_next(sg);
	195	}
	196
	197	sg_set_page(sg, bvec->bv_page, nbytes, bvec->bv_offset);
	198	nsegs++;
	199	}
	200	bvprv = bvec;
	201	} /* segments in rq */
	202
f18573ab FT	203
	204	if (unlikely(rq->cmd_flags & REQ_COPY_USER) &&
	205	(rq->data_len & q->dma_pad_mask)) {
	206	unsigned int pad_len = (q->dma_pad_mask & ~rq->data_len) + 1;
	207
	208	sg->length += pad_len;
	209	rq->extra_len += pad_len;
	210	}
	211
2fb98e84	212	if (q->dma_drain_size && q->dma_drain_needed(rq)) {
db0a2e00 TH	213	if (rq->cmd_flags & REQ_RW)
	214	memset(q->dma_drain_buffer, 0, q->dma_drain_size);
	215
d6d48196 JA	216	sg->page_link &= ~0x02;
	217	sg = sg_next(sg);
	218	sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
	219	q->dma_drain_size,
	220	((unsigned long)q->dma_drain_buffer) &
	221	(PAGE_SIZE - 1));
	222	nsegs++;
7a85f889	223	rq->extra_len += q->dma_drain_size;
d6d48196 JA	224	}
	225
	226	if (sg)
	227	sg_mark_end(sg);
	228
	229	return nsegs;
	230	}
d6d48196 JA	231	EXPORT_SYMBOL(blk_rq_map_sg);
	232
	233	static inline int ll_new_mergeable(struct request_queue *q,
	234	struct request *req,
	235	struct bio *bio)
	236	{
	237	int nr_phys_segs = bio_phys_segments(q, bio);
	238
	239	if (req->nr_phys_segments + nr_phys_segs > q->max_phys_segments) {
	240	req->cmd_flags \|= REQ_NOMERGE;
	241	if (req == q->last_merge)
	242	q->last_merge = NULL;
	243	return 0;
	244	}
	245
	246	/*
	247	* A hw segment is just getting larger, bump just the phys
	248	* counter.
	249	*/
	250	req->nr_phys_segments += nr_phys_segs;
	251	return 1;
	252	}
	253
	254	static inline int ll_new_hw_segment(struct request_queue *q,
	255	struct request *req,
	256	struct bio *bio)
	257	{
	258	int nr_hw_segs = bio_hw_segments(q, bio);
	259	int nr_phys_segs = bio_phys_segments(q, bio);
	260
	261	if (req->nr_hw_segments + nr_hw_segs > q->max_hw_segments
	262	\|\| req->nr_phys_segments + nr_phys_segs > q->max_phys_segments) {
	263	req->cmd_flags \|= REQ_NOMERGE;
	264	if (req == q->last_merge)
	265	q->last_merge = NULL;
	266	return 0;
	267	}
	268
	269	/*
	270	* This will form the start of a new hw segment. Bump both
	271	* counters.
	272	*/
	273	req->nr_hw_segments += nr_hw_segs;
	274	req->nr_phys_segments += nr_phys_segs;
	275	return 1;
	276	}
	277
	278	int ll_back_merge_fn(struct request_queue q, struct request req,
	279	struct bio *bio)
	280	{
	281	unsigned short max_sectors;
d6d48196 JA	282
	283	if (unlikely(blk_pc_request(req)))
	284	max_sectors = q->max_hw_sectors;
	285	else
	286	max_sectors = q->max_sectors;
	287
	288	if (req->nr_sectors + bio_sectors(bio) > max_sectors) {
	289	req->cmd_flags \|= REQ_NOMERGE;
	290	if (req == q->last_merge)
	291	q->last_merge = NULL;
	292	return 0;
	293	}
2cdf79ca	294	if (!bio_flagged(req->biotail, BIO_SEG_VALID))
d6d48196	295	blk_recount_segments(q, req->biotail);
2cdf79ca	296	if (!bio_flagged(bio, BIO_SEG_VALID))
d6d48196	297	blk_recount_segments(q, bio);
d6d48196 JA	298
	299	return ll_new_hw_segment(q, req, bio);
	300	}
	301
6728cb0e	302	int ll_front_merge_fn(struct request_queue q, struct request req,
d6d48196 JA	303	struct bio *bio)
	304	{
	305	unsigned short max_sectors;
d6d48196 JA	306
	307	if (unlikely(blk_pc_request(req)))
	308	max_sectors = q->max_hw_sectors;
	309	else
	310	max_sectors = q->max_sectors;
	311
	312
	313	if (req->nr_sectors + bio_sectors(bio) > max_sectors) {
	314	req->cmd_flags \|= REQ_NOMERGE;
	315	if (req == q->last_merge)
	316	q->last_merge = NULL;
	317	return 0;
	318	}
2cdf79ca	319	if (!bio_flagged(bio, BIO_SEG_VALID))
d6d48196	320	blk_recount_segments(q, bio);
2cdf79ca	321	if (!bio_flagged(req->bio, BIO_SEG_VALID))
d6d48196	322	blk_recount_segments(q, req->bio);
d6d48196 JA	323
	324	return ll_new_hw_segment(q, req, bio);
	325	}
	326
	327	static int ll_merge_requests_fn(struct request_queue q, struct request req,
	328	struct request *next)
	329	{
	330	int total_phys_segments;
	331	int total_hw_segments;
	332
	333	/*
	334	* First check if the either of the requests are re-queued
	335	* requests. Can't merge them if they are.
	336	*/
	337	if (req->special \|\| next->special)
	338	return 0;
	339
	340	/*
	341	* Will it become too large?
	342	*/
	343	if ((req->nr_sectors + next->nr_sectors) > q->max_sectors)
	344	return 0;
	345
	346	total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
	347	if (blk_phys_contig_segment(q, req->biotail, next->bio))
	348	total_phys_segments--;
	349
	350	if (total_phys_segments > q->max_phys_segments)
	351	return 0;
	352
	353	total_hw_segments = req->nr_hw_segments + next->nr_hw_segments;
d6d48196 JA	354
	355	if (total_hw_segments > q->max_hw_segments)
	356	return 0;
	357
	358	/* Merge is OK... */
	359	req->nr_phys_segments = total_phys_segments;
	360	req->nr_hw_segments = total_hw_segments;
	361	return 1;
	362	}
	363
	364	/*
	365	* Has to be called with the request spinlock acquired
	366	*/
	367	static int attempt_merge(struct request_queue q, struct request req,
	368	struct request *next)
	369	{
	370	if (!rq_mergeable(req) \|\| !rq_mergeable(next))
	371	return 0;
	372
	373	/*
	374	* not contiguous
	375	*/
	376	if (req->sector + req->nr_sectors != next->sector)
	377	return 0;
	378
	379	if (rq_data_dir(req) != rq_data_dir(next)
	380	\|\| req->rq_disk != next->rq_disk
	381	\|\| next->special)
	382	return 0;
	383
7ba1ba12 MP	384	if (blk_integrity_rq(req) != blk_integrity_rq(next))
	385	return 0;
	386
d6d48196 JA	387	/*
	388	* If we are allowed to merge, then append bio list
	389	* from next to rq and release next. merge_requests_fn
	390	* will have updated segment counts, update sector
	391	* counts here.
	392	*/
	393	if (!ll_merge_requests_fn(q, req, next))
	394	return 0;
	395
	396	/*
	397	* At this point we have either done a back merge
	398	* or front merge. We need the smaller start_time of
	399	* the merged requests to be the current request
	400	* for accounting purposes.
	401	*/
	402	if (time_after(req->start_time, next->start_time))
	403	req->start_time = next->start_time;
	404
	405	req->biotail->bi_next = next->bio;
	406	req->biotail = next->biotail;
	407
	408	req->nr_sectors = req->hard_nr_sectors += next->hard_nr_sectors;
	409
	410	elv_merge_requests(q, req, next);
	411
	412	if (req->rq_disk) {
6f2576af JM	413	struct hd_struct *part
6f2576af JM	414	= get_part(req->rq_disk, req->sector);
d6d48196 JA	415	disk_round_stats(req->rq_disk);
d6d48196 JA	416	req->rq_disk->in_flight--;
6f2576af JM	417	if (part) {
	418	part_round_stats(part);
	419	part->in_flight--;
	420	}
d6d48196 JA	421	}
	422
	423	req->ioprio = ioprio_best(req->ioprio, next->ioprio);
	424
	425	__blk_put_request(q, next);
	426	return 1;
	427	}
	428
	429	int attempt_back_merge(struct request_queue q, struct request rq)
	430	{
	431	struct request *next = elv_latter_request(q, rq);
	432
	433	if (next)
	434	return attempt_merge(q, rq, next);
	435
	436	return 0;
	437	}
	438
	439	int attempt_front_merge(struct request_queue q, struct request rq)
	440	{
	441	struct request *prev = elv_former_request(q, rq);
	442
	443	if (prev)
	444	return attempt_merge(q, prev, rq);
	445
	446	return 0;
	447	}