2 * Functions related to segment and merge handling
4 #include <linux/kernel.h>
5 #include <linux/module.h>
7 #include <linux/blkdev.h>
8 #include <linux/scatterlist.h>
12 static struct bio *blk_bio_discard_split(struct request_queue *q,
17 unsigned int max_discard_sectors, granularity;
20 unsigned split_sectors;
24 /* Zero-sector (unknown) and one-sector granularities are the same. */
25 granularity = max(q->limits.discard_granularity >> 9, 1U);
27 max_discard_sectors = min(q->limits.max_discard_sectors, UINT_MAX >> 9);
28 max_discard_sectors -= max_discard_sectors % granularity;
30 if (unlikely(!max_discard_sectors)) {
35 if (bio_sectors(bio) <= max_discard_sectors)
38 split_sectors = max_discard_sectors;
41 * If the next starting sector would be misaligned, stop the discard at
42 * the previous aligned sector.
44 alignment = (q->limits.discard_alignment >> 9) % granularity;
46 tmp = bio->bi_iter.bi_sector + split_sectors - alignment;
47 tmp = sector_div(tmp, granularity);
49 if (split_sectors > tmp)
52 return bio_split(bio, split_sectors, GFP_NOIO, bs);
55 static struct bio *blk_bio_write_same_split(struct request_queue *q,
62 if (!q->limits.max_write_same_sectors)
65 if (bio_sectors(bio) <= q->limits.max_write_same_sectors)
68 return bio_split(bio, q->limits.max_write_same_sectors, GFP_NOIO, bs);
71 static inline unsigned get_max_io_size(struct request_queue *q,
74 unsigned sectors = blk_max_size_offset(q, bio->bi_iter.bi_sector);
75 unsigned mask = queue_logical_block_size(q) - 1;
77 /* aligned to logical block size */
78 sectors &= ~(mask >> 9);
83 static struct bio *blk_bio_segment_split(struct request_queue *q,
88 struct bio_vec bv, bvprv, *bvprvp = NULL;
89 struct bvec_iter iter;
90 unsigned seg_size = 0, nsegs = 0, sectors = 0;
91 unsigned front_seg_size = bio->bi_seg_front_size;
93 struct bio *new = NULL;
94 const unsigned max_sectors = get_max_io_size(q, bio);
97 bio_for_each_segment(bv, bio, iter) {
99 * With arbitrary bio size, the incoming bio may be very
100 * big. We have to split the bio into small bios so that
101 * each holds at most BIO_MAX_PAGES bvecs because
102 * bio_clone() can fail to allocate big bvecs.
104 * It should have been better to apply the limit per
105 * request queue in which bio_clone() is involved,
106 * instead of globally. The biggest blocker is the
107 * bio_clone() in bio bounce.
109 * If bio is splitted by this reason, we should have
110 * allowed to continue bios merging, but don't do
111 * that now for making the change simple.
113 * TODO: deal with bio bounce's bio_clone() gracefully
114 * and convert the global limit into per-queue limit.
116 if (bvecs++ >= BIO_MAX_PAGES)
120 * If the queue doesn't support SG gaps and adding this
121 * offset would create a gap, disallow it.
123 if (bvprvp && bvec_gap_to_prev(q, bvprvp, bv.bv_offset))
126 if (sectors + (bv.bv_len >> 9) > max_sectors) {
128 * Consider this a new segment if we're splitting in
129 * the middle of this vector.
131 if (nsegs < queue_max_segments(q) &&
132 sectors < max_sectors) {
134 sectors = max_sectors;
138 /* Make this single bvec as the 1st segment */
141 if (bvprvp && blk_queue_cluster(q)) {
142 if (seg_size + bv.bv_len > queue_max_segment_size(q))
144 if (!BIOVEC_PHYS_MERGEABLE(bvprvp, &bv))
146 if (!BIOVEC_SEG_BOUNDARY(q, bvprvp, &bv))
149 seg_size += bv.bv_len;
152 sectors += bv.bv_len >> 9;
154 if (nsegs == 1 && seg_size > front_seg_size)
155 front_seg_size = seg_size;
159 if (nsegs == queue_max_segments(q))
165 seg_size = bv.bv_len;
166 sectors += bv.bv_len >> 9;
168 if (nsegs == 1 && seg_size > front_seg_size)
169 front_seg_size = seg_size;
177 new = bio_split(bio, sectors, GFP_NOIO, bs);
182 bio->bi_seg_front_size = front_seg_size;
183 if (seg_size > bio->bi_seg_back_size)
184 bio->bi_seg_back_size = seg_size;
186 return do_split ? new : NULL;
189 void blk_queue_split(struct request_queue *q, struct bio **bio,
192 struct bio *split, *res;
195 if ((*bio)->bi_rw & REQ_DISCARD)
196 split = blk_bio_discard_split(q, *bio, bs, &nsegs);
197 else if ((*bio)->bi_rw & REQ_WRITE_SAME)
198 split = blk_bio_write_same_split(q, *bio, bs, &nsegs);
200 split = blk_bio_segment_split(q, *bio, q->bio_split, &nsegs);
202 /* physical segments can be figured out during splitting */
203 res = split ? split : *bio;
204 res->bi_phys_segments = nsegs;
205 bio_set_flag(res, BIO_SEG_VALID);
208 /* there isn't chance to merge the splitted bio */
209 split->bi_rw |= REQ_NOMERGE;
211 bio_chain(split, *bio);
212 generic_make_request(*bio);
216 EXPORT_SYMBOL(blk_queue_split);
218 static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
222 struct bio_vec bv, bvprv = { NULL };
223 int cluster, prev = 0;
224 unsigned int seg_size, nr_phys_segs;
225 struct bio *fbio, *bbio;
226 struct bvec_iter iter;
232 * This should probably be returning 0, but blk_add_request_payload()
235 if (bio->bi_rw & REQ_DISCARD)
238 if (bio->bi_rw & REQ_WRITE_SAME)
242 cluster = blk_queue_cluster(q);
246 bio_for_each_segment(bv, bio, iter) {
248 * If SG merging is disabled, each bio vector is
254 if (prev && cluster) {
255 if (seg_size + bv.bv_len
256 > queue_max_segment_size(q))
258 if (!BIOVEC_PHYS_MERGEABLE(&bvprv, &bv))
260 if (!BIOVEC_SEG_BOUNDARY(q, &bvprv, &bv))
263 seg_size += bv.bv_len;
268 if (nr_phys_segs == 1 && seg_size >
269 fbio->bi_seg_front_size)
270 fbio->bi_seg_front_size = seg_size;
275 seg_size = bv.bv_len;
280 if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size)
281 fbio->bi_seg_front_size = seg_size;
282 if (seg_size > bbio->bi_seg_back_size)
283 bbio->bi_seg_back_size = seg_size;
288 void blk_recalc_rq_segments(struct request *rq)
290 bool no_sg_merge = !!test_bit(QUEUE_FLAG_NO_SG_MERGE,
291 &rq->q->queue_flags);
293 rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio,
297 void blk_recount_segments(struct request_queue *q, struct bio *bio)
299 unsigned short seg_cnt;
301 /* estimate segment number by bi_vcnt for non-cloned bio */
302 if (bio_flagged(bio, BIO_CLONED))
303 seg_cnt = bio_segments(bio);
305 seg_cnt = bio->bi_vcnt;
307 if (test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags) &&
308 (seg_cnt < queue_max_segments(q)))
309 bio->bi_phys_segments = seg_cnt;
311 struct bio *nxt = bio->bi_next;
314 bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio, false);
318 bio_set_flag(bio, BIO_SEG_VALID);
320 EXPORT_SYMBOL(blk_recount_segments);
322 static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
325 struct bio_vec end_bv = { NULL }, nxt_bv;
326 struct bvec_iter iter;
328 if (!blk_queue_cluster(q))
331 if (bio->bi_seg_back_size + nxt->bi_seg_front_size >
332 queue_max_segment_size(q))
335 if (!bio_has_data(bio))
338 bio_for_each_segment(end_bv, bio, iter)
339 if (end_bv.bv_len == iter.bi_size)
342 nxt_bv = bio_iovec(nxt);
344 if (!BIOVEC_PHYS_MERGEABLE(&end_bv, &nxt_bv))
348 * bio and nxt are contiguous in memory; check if the queue allows
349 * these two to be merged into one
351 if (BIOVEC_SEG_BOUNDARY(q, &end_bv, &nxt_bv))
358 __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec,
359 struct scatterlist *sglist, struct bio_vec *bvprv,
360 struct scatterlist **sg, int *nsegs, int *cluster)
363 int nbytes = bvec->bv_len;
365 if (*sg && *cluster) {
366 if ((*sg)->length + nbytes > queue_max_segment_size(q))
369 if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
371 if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
374 (*sg)->length += nbytes;
381 * If the driver previously mapped a shorter
382 * list, we could see a termination bit
383 * prematurely unless it fully inits the sg
384 * table on each mapping. We KNOW that there
385 * must be more entries here or the driver
386 * would be buggy, so force clear the
387 * termination bit to avoid doing a full
388 * sg_init_table() in drivers for each command.
394 sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset);
400 static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio,
401 struct scatterlist *sglist,
402 struct scatterlist **sg)
404 struct bio_vec bvec, bvprv = { NULL };
405 struct bvec_iter iter;
409 cluster = blk_queue_cluster(q);
411 if (bio->bi_rw & REQ_DISCARD) {
413 * This is a hack - drivers should be neither modifying the
414 * biovec, nor relying on bi_vcnt - but because of
415 * blk_add_request_payload(), a discard bio may or may not have
416 * a payload we need to set up here (thank you Christoph) and
417 * bi_vcnt is really the only way of telling if we need to.
426 if (bio->bi_rw & REQ_WRITE_SAME) {
429 bvec = bio_iovec(bio);
430 sg_set_page(*sg, bvec.bv_page, bvec.bv_len, bvec.bv_offset);
435 bio_for_each_segment(bvec, bio, iter)
436 __blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg,
443 * map a request to scatterlist, return number of sg entries setup. Caller
444 * must make sure sg can hold rq->nr_phys_segments entries
446 int blk_rq_map_sg(struct request_queue *q, struct request *rq,
447 struct scatterlist *sglist)
449 struct scatterlist *sg = NULL;
453 nsegs = __blk_bios_map_sg(q, rq->bio, sglist, &sg);
455 if (unlikely(rq->cmd_flags & REQ_COPY_USER) &&
456 (blk_rq_bytes(rq) & q->dma_pad_mask)) {
457 unsigned int pad_len =
458 (q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1;
460 sg->length += pad_len;
461 rq->extra_len += pad_len;
464 if (q->dma_drain_size && q->dma_drain_needed(rq)) {
465 if (rq->cmd_flags & REQ_WRITE)
466 memset(q->dma_drain_buffer, 0, q->dma_drain_size);
470 sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
472 ((unsigned long)q->dma_drain_buffer) &
475 rq->extra_len += q->dma_drain_size;
482 * Something must have been wrong if the figured number of
483 * segment is bigger than number of req's physical segments
485 WARN_ON(nsegs > rq->nr_phys_segments);
489 EXPORT_SYMBOL(blk_rq_map_sg);
491 static inline int ll_new_hw_segment(struct request_queue *q,
495 int nr_phys_segs = bio_phys_segments(q, bio);
497 if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q))
500 if (blk_integrity_merge_bio(q, req, bio) == false)
504 * This will form the start of a new hw segment. Bump both
507 req->nr_phys_segments += nr_phys_segs;
511 req->cmd_flags |= REQ_NOMERGE;
512 if (req == q->last_merge)
513 q->last_merge = NULL;
517 int ll_back_merge_fn(struct request_queue *q, struct request *req,
520 if (req_gap_back_merge(req, bio))
522 if (blk_integrity_rq(req) &&
523 integrity_req_gap_back_merge(req, bio))
525 if (blk_rq_sectors(req) + bio_sectors(bio) >
526 blk_rq_get_max_sectors(req)) {
527 req->cmd_flags |= REQ_NOMERGE;
528 if (req == q->last_merge)
529 q->last_merge = NULL;
532 if (!bio_flagged(req->biotail, BIO_SEG_VALID))
533 blk_recount_segments(q, req->biotail);
534 if (!bio_flagged(bio, BIO_SEG_VALID))
535 blk_recount_segments(q, bio);
537 return ll_new_hw_segment(q, req, bio);
540 int ll_front_merge_fn(struct request_queue *q, struct request *req,
544 if (req_gap_front_merge(req, bio))
546 if (blk_integrity_rq(req) &&
547 integrity_req_gap_front_merge(req, bio))
549 if (blk_rq_sectors(req) + bio_sectors(bio) >
550 blk_rq_get_max_sectors(req)) {
551 req->cmd_flags |= REQ_NOMERGE;
552 if (req == q->last_merge)
553 q->last_merge = NULL;
556 if (!bio_flagged(bio, BIO_SEG_VALID))
557 blk_recount_segments(q, bio);
558 if (!bio_flagged(req->bio, BIO_SEG_VALID))
559 blk_recount_segments(q, req->bio);
561 return ll_new_hw_segment(q, req, bio);
565 * blk-mq uses req->special to carry normal driver per-request payload, it
566 * does not indicate a prepared command that we cannot merge with.
568 static bool req_no_special_merge(struct request *req)
570 struct request_queue *q = req->q;
572 return !q->mq_ops && req->special;
575 static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
576 struct request *next)
578 int total_phys_segments;
579 unsigned int seg_size =
580 req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size;
583 * First check if the either of the requests are re-queued
584 * requests. Can't merge them if they are.
586 if (req_no_special_merge(req) || req_no_special_merge(next))
589 if (req_gap_back_merge(req, next->bio))
593 * Will it become too large?
595 if ((blk_rq_sectors(req) + blk_rq_sectors(next)) >
596 blk_rq_get_max_sectors(req))
599 total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
600 if (blk_phys_contig_segment(q, req->biotail, next->bio)) {
601 if (req->nr_phys_segments == 1)
602 req->bio->bi_seg_front_size = seg_size;
603 if (next->nr_phys_segments == 1)
604 next->biotail->bi_seg_back_size = seg_size;
605 total_phys_segments--;
608 if (total_phys_segments > queue_max_segments(q))
611 if (blk_integrity_merge_rq(q, req, next) == false)
615 req->nr_phys_segments = total_phys_segments;
620 * blk_rq_set_mixed_merge - mark a request as mixed merge
621 * @rq: request to mark as mixed merge
624 * @rq is about to be mixed merged. Make sure the attributes
625 * which can be mixed are set in each bio and mark @rq as mixed
628 void blk_rq_set_mixed_merge(struct request *rq)
630 unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
633 if (rq->cmd_flags & REQ_MIXED_MERGE)
637 * @rq will no longer represent mixable attributes for all the
638 * contained bios. It will just track those of the first one.
639 * Distributes the attributs to each bio.
641 for (bio = rq->bio; bio; bio = bio->bi_next) {
642 WARN_ON_ONCE((bio->bi_rw & REQ_FAILFAST_MASK) &&
643 (bio->bi_rw & REQ_FAILFAST_MASK) != ff);
646 rq->cmd_flags |= REQ_MIXED_MERGE;
649 static void blk_account_io_merge(struct request *req)
651 if (blk_do_io_stat(req)) {
652 struct hd_struct *part;
655 cpu = part_stat_lock();
658 part_round_stats(cpu, part);
659 part_dec_in_flight(part, rq_data_dir(req));
667 * Has to be called with the request spinlock acquired
669 static int attempt_merge(struct request_queue *q, struct request *req,
670 struct request *next)
672 if (!rq_mergeable(req) || !rq_mergeable(next))
675 if (!blk_check_merge_flags(req->cmd_flags, next->cmd_flags))
681 if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next))
684 if (rq_data_dir(req) != rq_data_dir(next)
685 || req->rq_disk != next->rq_disk
686 || req_no_special_merge(next))
689 if (req->cmd_flags & REQ_WRITE_SAME &&
690 !blk_write_same_mergeable(req->bio, next->bio))
694 * If we are allowed to merge, then append bio list
695 * from next to rq and release next. merge_requests_fn
696 * will have updated segment counts, update sector
699 if (!ll_merge_requests_fn(q, req, next))
703 * If failfast settings disagree or any of the two is already
704 * a mixed merge, mark both as mixed before proceeding. This
705 * makes sure that all involved bios have mixable attributes
708 if ((req->cmd_flags | next->cmd_flags) & REQ_MIXED_MERGE ||
709 (req->cmd_flags & REQ_FAILFAST_MASK) !=
710 (next->cmd_flags & REQ_FAILFAST_MASK)) {
711 blk_rq_set_mixed_merge(req);
712 blk_rq_set_mixed_merge(next);
716 * At this point we have either done a back merge
717 * or front merge. We need the smaller start_time of
718 * the merged requests to be the current request
719 * for accounting purposes.
721 if (time_after(req->start_time, next->start_time))
722 req->start_time = next->start_time;
724 req->biotail->bi_next = next->bio;
725 req->biotail = next->biotail;
727 req->__data_len += blk_rq_bytes(next);
729 elv_merge_requests(q, req, next);
732 * 'next' is going away, so update stats accordingly
734 blk_account_io_merge(next);
736 req->ioprio = ioprio_best(req->ioprio, next->ioprio);
737 if (blk_rq_cpu_valid(next))
738 req->cpu = next->cpu;
740 /* owner-ship of bio passed from next to req */
742 __blk_put_request(q, next);
746 int attempt_back_merge(struct request_queue *q, struct request *rq)
748 struct request *next = elv_latter_request(q, rq);
751 return attempt_merge(q, rq, next);
756 int attempt_front_merge(struct request_queue *q, struct request *rq)
758 struct request *prev = elv_former_request(q, rq);
761 return attempt_merge(q, prev, rq);
766 int blk_attempt_req_merge(struct request_queue *q, struct request *rq,
767 struct request *next)
769 return attempt_merge(q, rq, next);
772 bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
774 if (!rq_mergeable(rq) || !bio_mergeable(bio))
777 if (!blk_check_merge_flags(rq->cmd_flags, bio->bi_rw))
780 /* different data direction or already started, don't merge */
781 if (bio_data_dir(bio) != rq_data_dir(rq))
784 /* must be same device and not a special request */
785 if (rq->rq_disk != bio->bi_bdev->bd_disk || req_no_special_merge(rq))
788 /* only merge integrity protected bio into ditto rq */
789 if (blk_integrity_merge_bio(rq->q, rq, bio) == false)
792 /* must be using the same buffer */
793 if (rq->cmd_flags & REQ_WRITE_SAME &&
794 !blk_write_same_mergeable(rq->bio, bio))
800 int blk_try_merge(struct request *rq, struct bio *bio)
802 if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector)
803 return ELEVATOR_BACK_MERGE;
804 else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector)
805 return ELEVATOR_FRONT_MERGE;
806 return ELEVATOR_NO_MERGE;