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,
16 unsigned int max_discard_sectors, granularity;
19 unsigned split_sectors;
21 /* Zero-sector (unknown) and one-sector granularities are the same. */
22 granularity = max(q->limits.discard_granularity >> 9, 1U);
24 max_discard_sectors = min(q->limits.max_discard_sectors, UINT_MAX >> 9);
25 max_discard_sectors -= max_discard_sectors % granularity;
27 if (unlikely(!max_discard_sectors)) {
32 if (bio_sectors(bio) <= max_discard_sectors)
35 split_sectors = max_discard_sectors;
38 * If the next starting sector would be misaligned, stop the discard at
39 * the previous aligned sector.
41 alignment = (q->limits.discard_alignment >> 9) % granularity;
43 tmp = bio->bi_iter.bi_sector + split_sectors - alignment;
44 tmp = sector_div(tmp, granularity);
46 if (split_sectors > tmp)
49 return bio_split(bio, split_sectors, GFP_NOIO, bs);
52 static struct bio *blk_bio_write_same_split(struct request_queue *q,
56 if (!q->limits.max_write_same_sectors)
59 if (bio_sectors(bio) <= q->limits.max_write_same_sectors)
62 return bio_split(bio, q->limits.max_write_same_sectors, GFP_NOIO, bs);
65 static struct bio *blk_bio_segment_split(struct request_queue *q,
69 struct bio_vec bv, bvprv, *bvprvp = NULL;
70 struct bvec_iter iter;
71 unsigned seg_size = 0, nsegs = 0, sectors = 0;
73 bio_for_each_segment(bv, bio, iter) {
74 if (sectors + (bv.bv_len >> 9) > queue_max_sectors(q))
78 * If the queue doesn't support SG gaps and adding this
79 * offset would create a gap, disallow it.
81 if (bvprvp && bvec_gap_to_prev(q, bvprvp, bv.bv_offset))
84 if (bvprvp && blk_queue_cluster(q)) {
85 if (seg_size + bv.bv_len > queue_max_segment_size(q))
87 if (!BIOVEC_PHYS_MERGEABLE(bvprvp, &bv))
89 if (!BIOVEC_SEG_BOUNDARY(q, bvprvp, &bv))
92 seg_size += bv.bv_len;
95 sectors += bv.bv_len >> 9;
99 if (nsegs == queue_max_segments(q))
105 seg_size = bv.bv_len;
106 sectors += bv.bv_len >> 9;
111 return bio_split(bio, sectors, GFP_NOIO, bs);
114 void blk_queue_split(struct request_queue *q, struct bio **bio,
119 if ((*bio)->bi_rw & REQ_DISCARD)
120 split = blk_bio_discard_split(q, *bio, bs);
121 else if ((*bio)->bi_rw & REQ_WRITE_SAME)
122 split = blk_bio_write_same_split(q, *bio, bs);
124 split = blk_bio_segment_split(q, *bio, q->bio_split);
127 bio_chain(split, *bio);
128 generic_make_request(*bio);
132 EXPORT_SYMBOL(blk_queue_split);
134 static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
138 struct bio_vec bv, bvprv = { NULL };
139 int cluster, prev = 0;
140 unsigned int seg_size, nr_phys_segs;
141 struct bio *fbio, *bbio;
142 struct bvec_iter iter;
148 * This should probably be returning 0, but blk_add_request_payload()
151 if (bio->bi_rw & REQ_DISCARD)
154 if (bio->bi_rw & REQ_WRITE_SAME)
158 cluster = blk_queue_cluster(q);
162 bio_for_each_segment(bv, bio, iter) {
164 * If SG merging is disabled, each bio vector is
170 if (prev && cluster) {
171 if (seg_size + bv.bv_len
172 > queue_max_segment_size(q))
174 if (!BIOVEC_PHYS_MERGEABLE(&bvprv, &bv))
176 if (!BIOVEC_SEG_BOUNDARY(q, &bvprv, &bv))
179 seg_size += bv.bv_len;
184 if (nr_phys_segs == 1 && seg_size >
185 fbio->bi_seg_front_size)
186 fbio->bi_seg_front_size = seg_size;
191 seg_size = bv.bv_len;
196 if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size)
197 fbio->bi_seg_front_size = seg_size;
198 if (seg_size > bbio->bi_seg_back_size)
199 bbio->bi_seg_back_size = seg_size;
204 void blk_recalc_rq_segments(struct request *rq)
206 bool no_sg_merge = !!test_bit(QUEUE_FLAG_NO_SG_MERGE,
207 &rq->q->queue_flags);
209 rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio,
213 void blk_recount_segments(struct request_queue *q, struct bio *bio)
215 unsigned short seg_cnt;
217 /* estimate segment number by bi_vcnt for non-cloned bio */
218 if (bio_flagged(bio, BIO_CLONED))
219 seg_cnt = bio_segments(bio);
221 seg_cnt = bio->bi_vcnt;
223 if (test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags) &&
224 (seg_cnt < queue_max_segments(q)))
225 bio->bi_phys_segments = seg_cnt;
227 struct bio *nxt = bio->bi_next;
230 bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio, false);
234 bio_set_flag(bio, BIO_SEG_VALID);
236 EXPORT_SYMBOL(blk_recount_segments);
238 static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
241 struct bio_vec end_bv = { NULL }, nxt_bv;
242 struct bvec_iter iter;
244 if (!blk_queue_cluster(q))
247 if (bio->bi_seg_back_size + nxt->bi_seg_front_size >
248 queue_max_segment_size(q))
251 if (!bio_has_data(bio))
254 bio_for_each_segment(end_bv, bio, iter)
255 if (end_bv.bv_len == iter.bi_size)
258 nxt_bv = bio_iovec(nxt);
260 if (!BIOVEC_PHYS_MERGEABLE(&end_bv, &nxt_bv))
264 * bio and nxt are contiguous in memory; check if the queue allows
265 * these two to be merged into one
267 if (BIOVEC_SEG_BOUNDARY(q, &end_bv, &nxt_bv))
274 __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec,
275 struct scatterlist *sglist, struct bio_vec *bvprv,
276 struct scatterlist **sg, int *nsegs, int *cluster)
279 int nbytes = bvec->bv_len;
281 if (*sg && *cluster) {
282 if ((*sg)->length + nbytes > queue_max_segment_size(q))
285 if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
287 if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
290 (*sg)->length += nbytes;
297 * If the driver previously mapped a shorter
298 * list, we could see a termination bit
299 * prematurely unless it fully inits the sg
300 * table on each mapping. We KNOW that there
301 * must be more entries here or the driver
302 * would be buggy, so force clear the
303 * termination bit to avoid doing a full
304 * sg_init_table() in drivers for each command.
310 sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset);
316 static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio,
317 struct scatterlist *sglist,
318 struct scatterlist **sg)
320 struct bio_vec bvec, bvprv = { NULL };
321 struct bvec_iter iter;
325 cluster = blk_queue_cluster(q);
327 if (bio->bi_rw & REQ_DISCARD) {
329 * This is a hack - drivers should be neither modifying the
330 * biovec, nor relying on bi_vcnt - but because of
331 * blk_add_request_payload(), a discard bio may or may not have
332 * a payload we need to set up here (thank you Christoph) and
333 * bi_vcnt is really the only way of telling if we need to.
342 if (bio->bi_rw & REQ_WRITE_SAME) {
345 bvec = bio_iovec(bio);
346 sg_set_page(*sg, bvec.bv_page, bvec.bv_len, bvec.bv_offset);
351 bio_for_each_segment(bvec, bio, iter)
352 __blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg,
359 * map a request to scatterlist, return number of sg entries setup. Caller
360 * must make sure sg can hold rq->nr_phys_segments entries
362 int blk_rq_map_sg(struct request_queue *q, struct request *rq,
363 struct scatterlist *sglist)
365 struct scatterlist *sg = NULL;
369 nsegs = __blk_bios_map_sg(q, rq->bio, sglist, &sg);
371 if (unlikely(rq->cmd_flags & REQ_COPY_USER) &&
372 (blk_rq_bytes(rq) & q->dma_pad_mask)) {
373 unsigned int pad_len =
374 (q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1;
376 sg->length += pad_len;
377 rq->extra_len += pad_len;
380 if (q->dma_drain_size && q->dma_drain_needed(rq)) {
381 if (rq->cmd_flags & REQ_WRITE)
382 memset(q->dma_drain_buffer, 0, q->dma_drain_size);
386 sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
388 ((unsigned long)q->dma_drain_buffer) &
391 rq->extra_len += q->dma_drain_size;
399 EXPORT_SYMBOL(blk_rq_map_sg);
401 static inline int ll_new_hw_segment(struct request_queue *q,
405 int nr_phys_segs = bio_phys_segments(q, bio);
407 if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q))
410 if (blk_integrity_merge_bio(q, req, bio) == false)
414 * This will form the start of a new hw segment. Bump both
417 req->nr_phys_segments += nr_phys_segs;
421 req->cmd_flags |= REQ_NOMERGE;
422 if (req == q->last_merge)
423 q->last_merge = NULL;
427 int ll_back_merge_fn(struct request_queue *q, struct request *req,
430 if (req_gap_back_merge(req, bio))
432 if (blk_integrity_rq(req) &&
433 integrity_req_gap_back_merge(req, bio))
435 if (blk_rq_sectors(req) + bio_sectors(bio) >
436 blk_rq_get_max_sectors(req)) {
437 req->cmd_flags |= REQ_NOMERGE;
438 if (req == q->last_merge)
439 q->last_merge = NULL;
442 if (!bio_flagged(req->biotail, BIO_SEG_VALID))
443 blk_recount_segments(q, req->biotail);
444 if (!bio_flagged(bio, BIO_SEG_VALID))
445 blk_recount_segments(q, bio);
447 return ll_new_hw_segment(q, req, bio);
450 int ll_front_merge_fn(struct request_queue *q, struct request *req,
454 if (req_gap_front_merge(req, bio))
456 if (blk_integrity_rq(req) &&
457 integrity_req_gap_front_merge(req, bio))
459 if (blk_rq_sectors(req) + bio_sectors(bio) >
460 blk_rq_get_max_sectors(req)) {
461 req->cmd_flags |= REQ_NOMERGE;
462 if (req == q->last_merge)
463 q->last_merge = NULL;
466 if (!bio_flagged(bio, BIO_SEG_VALID))
467 blk_recount_segments(q, bio);
468 if (!bio_flagged(req->bio, BIO_SEG_VALID))
469 blk_recount_segments(q, req->bio);
471 return ll_new_hw_segment(q, req, bio);
475 * blk-mq uses req->special to carry normal driver per-request payload, it
476 * does not indicate a prepared command that we cannot merge with.
478 static bool req_no_special_merge(struct request *req)
480 struct request_queue *q = req->q;
482 return !q->mq_ops && req->special;
485 static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
486 struct request *next)
488 int total_phys_segments;
489 unsigned int seg_size =
490 req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size;
493 * First check if the either of the requests are re-queued
494 * requests. Can't merge them if they are.
496 if (req_no_special_merge(req) || req_no_special_merge(next))
499 if (req_gap_back_merge(req, next->bio))
503 * Will it become too large?
505 if ((blk_rq_sectors(req) + blk_rq_sectors(next)) >
506 blk_rq_get_max_sectors(req))
509 total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
510 if (blk_phys_contig_segment(q, req->biotail, next->bio)) {
511 if (req->nr_phys_segments == 1)
512 req->bio->bi_seg_front_size = seg_size;
513 if (next->nr_phys_segments == 1)
514 next->biotail->bi_seg_back_size = seg_size;
515 total_phys_segments--;
518 if (total_phys_segments > queue_max_segments(q))
521 if (blk_integrity_merge_rq(q, req, next) == false)
525 req->nr_phys_segments = total_phys_segments;
530 * blk_rq_set_mixed_merge - mark a request as mixed merge
531 * @rq: request to mark as mixed merge
534 * @rq is about to be mixed merged. Make sure the attributes
535 * which can be mixed are set in each bio and mark @rq as mixed
538 void blk_rq_set_mixed_merge(struct request *rq)
540 unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
543 if (rq->cmd_flags & REQ_MIXED_MERGE)
547 * @rq will no longer represent mixable attributes for all the
548 * contained bios. It will just track those of the first one.
549 * Distributes the attributs to each bio.
551 for (bio = rq->bio; bio; bio = bio->bi_next) {
552 WARN_ON_ONCE((bio->bi_rw & REQ_FAILFAST_MASK) &&
553 (bio->bi_rw & REQ_FAILFAST_MASK) != ff);
556 rq->cmd_flags |= REQ_MIXED_MERGE;
559 static void blk_account_io_merge(struct request *req)
561 if (blk_do_io_stat(req)) {
562 struct hd_struct *part;
565 cpu = part_stat_lock();
568 part_round_stats(cpu, part);
569 part_dec_in_flight(part, rq_data_dir(req));
577 * Has to be called with the request spinlock acquired
579 static int attempt_merge(struct request_queue *q, struct request *req,
580 struct request *next)
582 if (!rq_mergeable(req) || !rq_mergeable(next))
585 if (!blk_check_merge_flags(req->cmd_flags, next->cmd_flags))
591 if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next))
594 if (rq_data_dir(req) != rq_data_dir(next)
595 || req->rq_disk != next->rq_disk
596 || req_no_special_merge(next))
599 if (req->cmd_flags & REQ_WRITE_SAME &&
600 !blk_write_same_mergeable(req->bio, next->bio))
604 * If we are allowed to merge, then append bio list
605 * from next to rq and release next. merge_requests_fn
606 * will have updated segment counts, update sector
609 if (!ll_merge_requests_fn(q, req, next))
613 * If failfast settings disagree or any of the two is already
614 * a mixed merge, mark both as mixed before proceeding. This
615 * makes sure that all involved bios have mixable attributes
618 if ((req->cmd_flags | next->cmd_flags) & REQ_MIXED_MERGE ||
619 (req->cmd_flags & REQ_FAILFAST_MASK) !=
620 (next->cmd_flags & REQ_FAILFAST_MASK)) {
621 blk_rq_set_mixed_merge(req);
622 blk_rq_set_mixed_merge(next);
626 * At this point we have either done a back merge
627 * or front merge. We need the smaller start_time of
628 * the merged requests to be the current request
629 * for accounting purposes.
631 if (time_after(req->start_time, next->start_time))
632 req->start_time = next->start_time;
634 req->biotail->bi_next = next->bio;
635 req->biotail = next->biotail;
637 req->__data_len += blk_rq_bytes(next);
639 elv_merge_requests(q, req, next);
642 * 'next' is going away, so update stats accordingly
644 blk_account_io_merge(next);
646 req->ioprio = ioprio_best(req->ioprio, next->ioprio);
647 if (blk_rq_cpu_valid(next))
648 req->cpu = next->cpu;
650 /* owner-ship of bio passed from next to req */
652 __blk_put_request(q, next);
656 int attempt_back_merge(struct request_queue *q, struct request *rq)
658 struct request *next = elv_latter_request(q, rq);
661 return attempt_merge(q, rq, next);
666 int attempt_front_merge(struct request_queue *q, struct request *rq)
668 struct request *prev = elv_former_request(q, rq);
671 return attempt_merge(q, prev, rq);
676 int blk_attempt_req_merge(struct request_queue *q, struct request *rq,
677 struct request *next)
679 return attempt_merge(q, rq, next);
682 bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
684 if (!rq_mergeable(rq) || !bio_mergeable(bio))
687 if (!blk_check_merge_flags(rq->cmd_flags, bio->bi_rw))
690 /* different data direction or already started, don't merge */
691 if (bio_data_dir(bio) != rq_data_dir(rq))
694 /* must be same device and not a special request */
695 if (rq->rq_disk != bio->bi_bdev->bd_disk || req_no_special_merge(rq))
698 /* only merge integrity protected bio into ditto rq */
699 if (blk_integrity_merge_bio(rq->q, rq, bio) == false)
702 /* must be using the same buffer */
703 if (rq->cmd_flags & REQ_WRITE_SAME &&
704 !blk_write_same_mergeable(rq->bio, bio))
710 int blk_try_merge(struct request *rq, struct bio *bio)
712 if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector)
713 return ELEVATOR_BACK_MERGE;
714 else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector)
715 return ELEVATOR_FRONT_MERGE;
716 return ELEVATOR_NO_MERGE;