[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"

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

	/*
	 * Don't merge file system requests and discard requests
	 */
	if ((req->cmd_flags & REQ_DISCARD) != (next->cmd_flags & REQ_DISCARD))
		return 0;

	/*
	 * Don't merge discard requests and secure discard requests
	 */
	if ((req->cmd_flags & REQ_SECURE) != (next->cmd_flags & REQ_SECURE))
		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	struct bio_vec bv, bvprv = NULL;
1e428079 JA	16	int cluster, i, high, highprv = 1;
1e428079 JA	17	unsigned int seg_size, nr_phys_segs;
59247eae	18	struct bio fbio, bbio;
d6d48196	19
1e428079 JA	20	if (!bio)
1e428079 JA	21	return 0;
d6d48196	22
1e428079	23	fbio = bio;
75ad23bc	24	cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
5df97b91	25	seg_size = 0;
2c8919de	26	nr_phys_segs = 0;
1e428079 JA	27	for_each_bio(bio) {
	28	bio_for_each_segment(bv, bio, i) {
	29	/*
	30	* the trick here is making sure that a high page is
	31	* never considered part of another segment, since that
	32	* might change with the bounce page.
	33	*/
ae03bf63	34	high = page_to_pfn(bv->bv_page) > queue_bounce_pfn(q);
1e428079	35	if (high \|\| highprv)
d6d48196	36	goto new_segment;
1e428079	37	if (cluster) {
ae03bf63 MP	38	if (seg_size + bv->bv_len
ae03bf63 MP	39	> queue_max_segment_size(q))
1e428079 JA	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	93	if (bio->bi_seg_back_size + nxt->bi_seg_front_size >
ae03bf63	94	queue_max_segment_size(q))
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) {
ae03bf63	137	if (sg->length + nbytes > queue_max_segment_size(q))
d6d48196 JA	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)) {
7b6d91da	182	if (rq->cmd_flags & REQ_WRITE)
db0a2e00 TH	183	memset(q->dma_drain_buffer, 0, q->dma_drain_size);
db0a2e00 TH	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
8a78362c	208	if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q)) {
d6d48196 JA	209	req->cmd_flags \|= REQ_NOMERGE;
	210	if (req == q->last_merge)
	211	q->last_merge = NULL;
	212	return 0;
	213	}
	214
	215	/*
	216	* This will form the start of a new hw segment. Bump both
	217	* counters.
	218	*/
d6d48196 JA	219	req->nr_phys_segments += nr_phys_segs;
	220	return 1;
	221	}
	222
	223	int ll_back_merge_fn(struct request_queue q, struct request req,
	224	struct bio *bio)
	225	{
	226	unsigned short max_sectors;
d6d48196	227
33659ebb	228	if (unlikely(req->cmd_type == REQ_TYPE_BLOCK_PC))
ae03bf63	229	max_sectors = queue_max_hw_sectors(q);
d6d48196	230	else
ae03bf63	231	max_sectors = queue_max_sectors(q);
d6d48196	232
83096ebf	233	if (blk_rq_sectors(req) + bio_sectors(bio) > max_sectors) {
d6d48196 JA	234	req->cmd_flags \|= REQ_NOMERGE;
	235	if (req == q->last_merge)
	236	q->last_merge = NULL;
	237	return 0;
	238	}
2cdf79ca	239	if (!bio_flagged(req->biotail, BIO_SEG_VALID))
d6d48196	240	blk_recount_segments(q, req->biotail);
2cdf79ca	241	if (!bio_flagged(bio, BIO_SEG_VALID))
d6d48196	242	blk_recount_segments(q, bio);
d6d48196 JA	243
	244	return ll_new_hw_segment(q, req, bio);
	245	}
	246
6728cb0e	247	int ll_front_merge_fn(struct request_queue q, struct request req,
d6d48196 JA	248	struct bio *bio)
	249	{
	250	unsigned short max_sectors;
d6d48196	251
33659ebb	252	if (unlikely(req->cmd_type == REQ_TYPE_BLOCK_PC))
ae03bf63	253	max_sectors = queue_max_hw_sectors(q);
d6d48196	254	else
ae03bf63	255	max_sectors = queue_max_sectors(q);
d6d48196 JA	256
d6d48196 JA	257
83096ebf	258	if (blk_rq_sectors(req) + bio_sectors(bio) > max_sectors) {
d6d48196 JA	259	req->cmd_flags \|= REQ_NOMERGE;
	260	if (req == q->last_merge)
	261	q->last_merge = NULL;
	262	return 0;
	263	}
2cdf79ca	264	if (!bio_flagged(bio, BIO_SEG_VALID))
d6d48196	265	blk_recount_segments(q, bio);
2cdf79ca	266	if (!bio_flagged(req->bio, BIO_SEG_VALID))
d6d48196	267	blk_recount_segments(q, req->bio);
d6d48196 JA	268
	269	return ll_new_hw_segment(q, req, bio);
	270	}
	271
	272	static int ll_merge_requests_fn(struct request_queue q, struct request req,
	273	struct request *next)
	274	{
	275	int total_phys_segments;
86771427 FT	276	unsigned int seg_size =
86771427 FT	277	req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size;
d6d48196 JA	278
	279	/*
	280	* First check if the either of the requests are re-queued
	281	* requests. Can't merge them if they are.
	282	*/
	283	if (req->special \|\| next->special)
	284	return 0;
	285
	286	/*
	287	* Will it become too large?
	288	*/
ae03bf63	289	if ((blk_rq_sectors(req) + blk_rq_sectors(next)) > queue_max_sectors(q))
d6d48196 JA	290	return 0;
	291
	292	total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
86771427 FT	293	if (blk_phys_contig_segment(q, req->biotail, next->bio)) {
	294	if (req->nr_phys_segments == 1)
	295	req->bio->bi_seg_front_size = seg_size;
	296	if (next->nr_phys_segments == 1)
	297	next->biotail->bi_seg_back_size = seg_size;
d6d48196	298	total_phys_segments--;
86771427	299	}
d6d48196	300
8a78362c	301	if (total_phys_segments > queue_max_segments(q))
d6d48196 JA	302	return 0;
	303
	304	/* Merge is OK... */
	305	req->nr_phys_segments = total_phys_segments;
d6d48196 JA	306	return 1;
	307	}
	308
80a761fd TH	309	/**
	310	* blk_rq_set_mixed_merge - mark a request as mixed merge
	311	* @rq: request to mark as mixed merge
	312	*
	313	* Description:
	314	* @rq is about to be mixed merged. Make sure the attributes
	315	* which can be mixed are set in each bio and mark @rq as mixed
	316	* merged.
	317	*/
	318	void blk_rq_set_mixed_merge(struct request *rq)
	319	{
	320	unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
	321	struct bio *bio;
	322
	323	if (rq->cmd_flags & REQ_MIXED_MERGE)
	324	return;
	325
	326	/*
	327	* @rq will no longer represent mixable attributes for all the
	328	* contained bios. It will just track those of the first one.
	329	* Distributes the attributs to each bio.
	330	*/
	331	for (bio = rq->bio; bio; bio = bio->bi_next) {
	332	WARN_ON_ONCE((bio->bi_rw & REQ_FAILFAST_MASK) &&
	333	(bio->bi_rw & REQ_FAILFAST_MASK) != ff);
	334	bio->bi_rw \|= ff;
	335	}
	336	rq->cmd_flags \|= REQ_MIXED_MERGE;
	337	}
	338
26308eab JM	339	static void blk_account_io_merge(struct request *req)
	340	{
	341	if (blk_do_io_stat(req)) {
	342	struct hd_struct *part;
	343	int cpu;
	344
	345	cpu = part_stat_lock();
83096ebf	346	part = disk_map_sector_rcu(req->rq_disk, blk_rq_pos(req));
26308eab JM	347
26308eab JM	348	part_round_stats(cpu, part);
316d315b	349	part_dec_in_flight(part, rq_data_dir(req));
26308eab JM	350
	351	part_stat_unlock();
	352	}
	353	}
	354
d6d48196 JA	355	/*
	356	* Has to be called with the request spinlock acquired
	357	*/
	358	static int attempt_merge(struct request_queue q, struct request req,
	359	struct request *next)
	360	{
	361	if (!rq_mergeable(req) \|\| !rq_mergeable(next))
	362	return 0;
	363
f281fb5f AH	364	/*
	365	* Don't merge file system requests and discard requests
	366	*/
	367	if ((req->cmd_flags & REQ_DISCARD) != (next->cmd_flags & REQ_DISCARD))
	368	return 0;
	369
	370	/*
	371	* Don't merge discard requests and secure discard requests
	372	*/
	373	if ((req->cmd_flags & REQ_SECURE) != (next->cmd_flags & REQ_SECURE))
	374	return 0;
	375
d6d48196 JA	376	/*
	377	* not contiguous
	378	*/
83096ebf	379	if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next))
d6d48196 JA	380	return 0;
	381
	382	if (rq_data_dir(req) != rq_data_dir(next)
	383	\|\| req->rq_disk != next->rq_disk
	384	\|\| next->special)
	385	return 0;
	386
7ba1ba12 MP	387	if (blk_integrity_rq(req) != blk_integrity_rq(next))
	388	return 0;
	389
d6d48196 JA	390	/*
	391	* If we are allowed to merge, then append bio list
	392	* from next to rq and release next. merge_requests_fn
	393	* will have updated segment counts, update sector
	394	* counts here.
	395	*/
	396	if (!ll_merge_requests_fn(q, req, next))
	397	return 0;
	398
80a761fd TH	399	/*
	400	* If failfast settings disagree or any of the two is already
	401	* a mixed merge, mark both as mixed before proceeding. This
	402	* makes sure that all involved bios have mixable attributes
	403	* set properly.
	404	*/
	405	if ((req->cmd_flags \| next->cmd_flags) & REQ_MIXED_MERGE \|\|
	406	(req->cmd_flags & REQ_FAILFAST_MASK) !=
	407	(next->cmd_flags & REQ_FAILFAST_MASK)) {
	408	blk_rq_set_mixed_merge(req);
	409	blk_rq_set_mixed_merge(next);
	410	}
	411
d6d48196 JA	412	/*
	413	* At this point we have either done a back merge
	414	* or front merge. We need the smaller start_time of
	415	* the merged requests to be the current request
	416	* for accounting purposes.
	417	*/
	418	if (time_after(req->start_time, next->start_time))
	419	req->start_time = next->start_time;
	420
	421	req->biotail->bi_next = next->bio;
	422	req->biotail = next->biotail;
	423
a2dec7b3	424	req->__data_len += blk_rq_bytes(next);
d6d48196 JA	425
	426	elv_merge_requests(q, req, next);
	427
42dad764 JM	428	/*
	429	* 'next' is going away, so update stats accordingly
	430	*/
	431	blk_account_io_merge(next);
d6d48196 JA	432
d6d48196 JA	433	req->ioprio = ioprio_best(req->ioprio, next->ioprio);
ab780f1e JA	434	if (blk_rq_cpu_valid(next))
ab780f1e JA	435	req->cpu = next->cpu;
d6d48196	436
1cd96c24 BH	437	/* owner-ship of bio passed from next to req */
1cd96c24 BH	438	next->bio = NULL;
d6d48196 JA	439	__blk_put_request(q, next);
	440	return 1;
	441	}
	442
	443	int attempt_back_merge(struct request_queue q, struct request rq)
	444	{
	445	struct request *next = elv_latter_request(q, rq);
	446
	447	if (next)
	448	return attempt_merge(q, rq, next);
	449
	450	return 0;
	451	}
	452
	453	int attempt_front_merge(struct request_queue q, struct request rq)
	454	{
	455	struct request *prev = elv_former_request(q, rq);
	456
	457	if (prev)
	458	return attempt_merge(q, prev, rq);
	459
	460	return 0;
	461	}