Merge tag 'iommu-updates-v4.13' of git://git.kernel.org/pub/scm/linux/kernel/git...
[linux.git] / block / blk-merge.c
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 <trace/events/block.h>
11
12 #include "blk.h"
13
14 static struct bio *blk_bio_discard_split(struct request_queue *q,
15                                          struct bio *bio,
16                                          struct bio_set *bs,
17                                          unsigned *nsegs)
18 {
19         unsigned int max_discard_sectors, granularity;
20         int alignment;
21         sector_t tmp;
22         unsigned split_sectors;
23
24         *nsegs = 1;
25
26         /* Zero-sector (unknown) and one-sector granularities are the same.  */
27         granularity = max(q->limits.discard_granularity >> 9, 1U);
28
29         max_discard_sectors = min(q->limits.max_discard_sectors, UINT_MAX >> 9);
30         max_discard_sectors -= max_discard_sectors % granularity;
31
32         if (unlikely(!max_discard_sectors)) {
33                 /* XXX: warn */
34                 return NULL;
35         }
36
37         if (bio_sectors(bio) <= max_discard_sectors)
38                 return NULL;
39
40         split_sectors = max_discard_sectors;
41
42         /*
43          * If the next starting sector would be misaligned, stop the discard at
44          * the previous aligned sector.
45          */
46         alignment = (q->limits.discard_alignment >> 9) % granularity;
47
48         tmp = bio->bi_iter.bi_sector + split_sectors - alignment;
49         tmp = sector_div(tmp, granularity);
50
51         if (split_sectors > tmp)
52                 split_sectors -= tmp;
53
54         return bio_split(bio, split_sectors, GFP_NOIO, bs);
55 }
56
57 static struct bio *blk_bio_write_zeroes_split(struct request_queue *q,
58                 struct bio *bio, struct bio_set *bs, unsigned *nsegs)
59 {
60         *nsegs = 1;
61
62         if (!q->limits.max_write_zeroes_sectors)
63                 return NULL;
64
65         if (bio_sectors(bio) <= q->limits.max_write_zeroes_sectors)
66                 return NULL;
67
68         return bio_split(bio, q->limits.max_write_zeroes_sectors, GFP_NOIO, bs);
69 }
70
71 static struct bio *blk_bio_write_same_split(struct request_queue *q,
72                                             struct bio *bio,
73                                             struct bio_set *bs,
74                                             unsigned *nsegs)
75 {
76         *nsegs = 1;
77
78         if (!q->limits.max_write_same_sectors)
79                 return NULL;
80
81         if (bio_sectors(bio) <= q->limits.max_write_same_sectors)
82                 return NULL;
83
84         return bio_split(bio, q->limits.max_write_same_sectors, GFP_NOIO, bs);
85 }
86
87 static inline unsigned get_max_io_size(struct request_queue *q,
88                                        struct bio *bio)
89 {
90         unsigned sectors = blk_max_size_offset(q, bio->bi_iter.bi_sector);
91         unsigned mask = queue_logical_block_size(q) - 1;
92
93         /* aligned to logical block size */
94         sectors &= ~(mask >> 9);
95
96         return sectors;
97 }
98
99 static struct bio *blk_bio_segment_split(struct request_queue *q,
100                                          struct bio *bio,
101                                          struct bio_set *bs,
102                                          unsigned *segs)
103 {
104         struct bio_vec bv, bvprv, *bvprvp = NULL;
105         struct bvec_iter iter;
106         unsigned seg_size = 0, nsegs = 0, sectors = 0;
107         unsigned front_seg_size = bio->bi_seg_front_size;
108         bool do_split = true;
109         struct bio *new = NULL;
110         const unsigned max_sectors = get_max_io_size(q, bio);
111
112         bio_for_each_segment(bv, bio, iter) {
113                 /*
114                  * If the queue doesn't support SG gaps and adding this
115                  * offset would create a gap, disallow it.
116                  */
117                 if (bvprvp && bvec_gap_to_prev(q, bvprvp, bv.bv_offset))
118                         goto split;
119
120                 if (sectors + (bv.bv_len >> 9) > max_sectors) {
121                         /*
122                          * Consider this a new segment if we're splitting in
123                          * the middle of this vector.
124                          */
125                         if (nsegs < queue_max_segments(q) &&
126                             sectors < max_sectors) {
127                                 nsegs++;
128                                 sectors = max_sectors;
129                         }
130                         if (sectors)
131                                 goto split;
132                         /* Make this single bvec as the 1st segment */
133                 }
134
135                 if (bvprvp && blk_queue_cluster(q)) {
136                         if (seg_size + bv.bv_len > queue_max_segment_size(q))
137                                 goto new_segment;
138                         if (!BIOVEC_PHYS_MERGEABLE(bvprvp, &bv))
139                                 goto new_segment;
140                         if (!BIOVEC_SEG_BOUNDARY(q, bvprvp, &bv))
141                                 goto new_segment;
142
143                         seg_size += bv.bv_len;
144                         bvprv = bv;
145                         bvprvp = &bvprv;
146                         sectors += bv.bv_len >> 9;
147
148                         if (nsegs == 1 && seg_size > front_seg_size)
149                                 front_seg_size = seg_size;
150                         continue;
151                 }
152 new_segment:
153                 if (nsegs == queue_max_segments(q))
154                         goto split;
155
156                 nsegs++;
157                 bvprv = bv;
158                 bvprvp = &bvprv;
159                 seg_size = bv.bv_len;
160                 sectors += bv.bv_len >> 9;
161
162                 if (nsegs == 1 && seg_size > front_seg_size)
163                         front_seg_size = seg_size;
164         }
165
166         do_split = false;
167 split:
168         *segs = nsegs;
169
170         if (do_split) {
171                 new = bio_split(bio, sectors, GFP_NOIO, bs);
172                 if (new)
173                         bio = new;
174         }
175
176         bio->bi_seg_front_size = front_seg_size;
177         if (seg_size > bio->bi_seg_back_size)
178                 bio->bi_seg_back_size = seg_size;
179
180         return do_split ? new : NULL;
181 }
182
183 void blk_queue_split(struct request_queue *q, struct bio **bio)
184 {
185         struct bio *split, *res;
186         unsigned nsegs;
187
188         switch (bio_op(*bio)) {
189         case REQ_OP_DISCARD:
190         case REQ_OP_SECURE_ERASE:
191                 split = blk_bio_discard_split(q, *bio, q->bio_split, &nsegs);
192                 break;
193         case REQ_OP_WRITE_ZEROES:
194                 split = blk_bio_write_zeroes_split(q, *bio, q->bio_split, &nsegs);
195                 break;
196         case REQ_OP_WRITE_SAME:
197                 split = blk_bio_write_same_split(q, *bio, q->bio_split, &nsegs);
198                 break;
199         default:
200                 split = blk_bio_segment_split(q, *bio, q->bio_split, &nsegs);
201                 break;
202         }
203
204         /* physical segments can be figured out during splitting */
205         res = split ? split : *bio;
206         res->bi_phys_segments = nsegs;
207         bio_set_flag(res, BIO_SEG_VALID);
208
209         if (split) {
210                 /* there isn't chance to merge the splitted bio */
211                 split->bi_opf |= REQ_NOMERGE;
212
213                 bio_chain(split, *bio);
214                 trace_block_split(q, split, (*bio)->bi_iter.bi_sector);
215                 generic_make_request(*bio);
216                 *bio = split;
217         }
218 }
219 EXPORT_SYMBOL(blk_queue_split);
220
221 static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
222                                              struct bio *bio,
223                                              bool no_sg_merge)
224 {
225         struct bio_vec bv, bvprv = { NULL };
226         int cluster, prev = 0;
227         unsigned int seg_size, nr_phys_segs;
228         struct bio *fbio, *bbio;
229         struct bvec_iter iter;
230
231         if (!bio)
232                 return 0;
233
234         switch (bio_op(bio)) {
235         case REQ_OP_DISCARD:
236         case REQ_OP_SECURE_ERASE:
237         case REQ_OP_WRITE_ZEROES:
238                 return 0;
239         case REQ_OP_WRITE_SAME:
240                 return 1;
241         }
242
243         fbio = bio;
244         cluster = blk_queue_cluster(q);
245         seg_size = 0;
246         nr_phys_segs = 0;
247         for_each_bio(bio) {
248                 bio_for_each_segment(bv, bio, iter) {
249                         /*
250                          * If SG merging is disabled, each bio vector is
251                          * a segment
252                          */
253                         if (no_sg_merge)
254                                 goto new_segment;
255
256                         if (prev && cluster) {
257                                 if (seg_size + bv.bv_len
258                                     > queue_max_segment_size(q))
259                                         goto new_segment;
260                                 if (!BIOVEC_PHYS_MERGEABLE(&bvprv, &bv))
261                                         goto new_segment;
262                                 if (!BIOVEC_SEG_BOUNDARY(q, &bvprv, &bv))
263                                         goto new_segment;
264
265                                 seg_size += bv.bv_len;
266                                 bvprv = bv;
267                                 continue;
268                         }
269 new_segment:
270                         if (nr_phys_segs == 1 && seg_size >
271                             fbio->bi_seg_front_size)
272                                 fbio->bi_seg_front_size = seg_size;
273
274                         nr_phys_segs++;
275                         bvprv = bv;
276                         prev = 1;
277                         seg_size = bv.bv_len;
278                 }
279                 bbio = bio;
280         }
281
282         if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size)
283                 fbio->bi_seg_front_size = seg_size;
284         if (seg_size > bbio->bi_seg_back_size)
285                 bbio->bi_seg_back_size = seg_size;
286
287         return nr_phys_segs;
288 }
289
290 void blk_recalc_rq_segments(struct request *rq)
291 {
292         bool no_sg_merge = !!test_bit(QUEUE_FLAG_NO_SG_MERGE,
293                         &rq->q->queue_flags);
294
295         rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio,
296                         no_sg_merge);
297 }
298
299 void blk_recount_segments(struct request_queue *q, struct bio *bio)
300 {
301         unsigned short seg_cnt;
302
303         /* estimate segment number by bi_vcnt for non-cloned bio */
304         if (bio_flagged(bio, BIO_CLONED))
305                 seg_cnt = bio_segments(bio);
306         else
307                 seg_cnt = bio->bi_vcnt;
308
309         if (test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags) &&
310                         (seg_cnt < queue_max_segments(q)))
311                 bio->bi_phys_segments = seg_cnt;
312         else {
313                 struct bio *nxt = bio->bi_next;
314
315                 bio->bi_next = NULL;
316                 bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio, false);
317                 bio->bi_next = nxt;
318         }
319
320         bio_set_flag(bio, BIO_SEG_VALID);
321 }
322 EXPORT_SYMBOL(blk_recount_segments);
323
324 static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
325                                    struct bio *nxt)
326 {
327         struct bio_vec end_bv = { NULL }, nxt_bv;
328
329         if (!blk_queue_cluster(q))
330                 return 0;
331
332         if (bio->bi_seg_back_size + nxt->bi_seg_front_size >
333             queue_max_segment_size(q))
334                 return 0;
335
336         if (!bio_has_data(bio))
337                 return 1;
338
339         bio_get_last_bvec(bio, &end_bv);
340         bio_get_first_bvec(nxt, &nxt_bv);
341
342         if (!BIOVEC_PHYS_MERGEABLE(&end_bv, &nxt_bv))
343                 return 0;
344
345         /*
346          * bio and nxt are contiguous in memory; check if the queue allows
347          * these two to be merged into one
348          */
349         if (BIOVEC_SEG_BOUNDARY(q, &end_bv, &nxt_bv))
350                 return 1;
351
352         return 0;
353 }
354
355 static inline void
356 __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec,
357                      struct scatterlist *sglist, struct bio_vec *bvprv,
358                      struct scatterlist **sg, int *nsegs, int *cluster)
359 {
360
361         int nbytes = bvec->bv_len;
362
363         if (*sg && *cluster) {
364                 if ((*sg)->length + nbytes > queue_max_segment_size(q))
365                         goto new_segment;
366
367                 if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
368                         goto new_segment;
369                 if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
370                         goto new_segment;
371
372                 (*sg)->length += nbytes;
373         } else {
374 new_segment:
375                 if (!*sg)
376                         *sg = sglist;
377                 else {
378                         /*
379                          * If the driver previously mapped a shorter
380                          * list, we could see a termination bit
381                          * prematurely unless it fully inits the sg
382                          * table on each mapping. We KNOW that there
383                          * must be more entries here or the driver
384                          * would be buggy, so force clear the
385                          * termination bit to avoid doing a full
386                          * sg_init_table() in drivers for each command.
387                          */
388                         sg_unmark_end(*sg);
389                         *sg = sg_next(*sg);
390                 }
391
392                 sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset);
393                 (*nsegs)++;
394         }
395         *bvprv = *bvec;
396 }
397
398 static inline int __blk_bvec_map_sg(struct request_queue *q, struct bio_vec bv,
399                 struct scatterlist *sglist, struct scatterlist **sg)
400 {
401         *sg = sglist;
402         sg_set_page(*sg, bv.bv_page, bv.bv_len, bv.bv_offset);
403         return 1;
404 }
405
406 static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio,
407                              struct scatterlist *sglist,
408                              struct scatterlist **sg)
409 {
410         struct bio_vec bvec, bvprv = { NULL };
411         struct bvec_iter iter;
412         int cluster = blk_queue_cluster(q), nsegs = 0;
413
414         for_each_bio(bio)
415                 bio_for_each_segment(bvec, bio, iter)
416                         __blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg,
417                                              &nsegs, &cluster);
418
419         return nsegs;
420 }
421
422 /*
423  * map a request to scatterlist, return number of sg entries setup. Caller
424  * must make sure sg can hold rq->nr_phys_segments entries
425  */
426 int blk_rq_map_sg(struct request_queue *q, struct request *rq,
427                   struct scatterlist *sglist)
428 {
429         struct scatterlist *sg = NULL;
430         int nsegs = 0;
431
432         if (rq->rq_flags & RQF_SPECIAL_PAYLOAD)
433                 nsegs = __blk_bvec_map_sg(q, rq->special_vec, sglist, &sg);
434         else if (rq->bio && bio_op(rq->bio) == REQ_OP_WRITE_SAME)
435                 nsegs = __blk_bvec_map_sg(q, bio_iovec(rq->bio), sglist, &sg);
436         else if (rq->bio)
437                 nsegs = __blk_bios_map_sg(q, rq->bio, sglist, &sg);
438
439         if (unlikely(rq->rq_flags & RQF_COPY_USER) &&
440             (blk_rq_bytes(rq) & q->dma_pad_mask)) {
441                 unsigned int pad_len =
442                         (q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1;
443
444                 sg->length += pad_len;
445                 rq->extra_len += pad_len;
446         }
447
448         if (q->dma_drain_size && q->dma_drain_needed(rq)) {
449                 if (op_is_write(req_op(rq)))
450                         memset(q->dma_drain_buffer, 0, q->dma_drain_size);
451
452                 sg_unmark_end(sg);
453                 sg = sg_next(sg);
454                 sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
455                             q->dma_drain_size,
456                             ((unsigned long)q->dma_drain_buffer) &
457                             (PAGE_SIZE - 1));
458                 nsegs++;
459                 rq->extra_len += q->dma_drain_size;
460         }
461
462         if (sg)
463                 sg_mark_end(sg);
464
465         /*
466          * Something must have been wrong if the figured number of
467          * segment is bigger than number of req's physical segments
468          */
469         WARN_ON(nsegs > blk_rq_nr_phys_segments(rq));
470
471         return nsegs;
472 }
473 EXPORT_SYMBOL(blk_rq_map_sg);
474
475 static inline int ll_new_hw_segment(struct request_queue *q,
476                                     struct request *req,
477                                     struct bio *bio)
478 {
479         int nr_phys_segs = bio_phys_segments(q, bio);
480
481         if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q))
482                 goto no_merge;
483
484         if (blk_integrity_merge_bio(q, req, bio) == false)
485                 goto no_merge;
486
487         /*
488          * This will form the start of a new hw segment.  Bump both
489          * counters.
490          */
491         req->nr_phys_segments += nr_phys_segs;
492         return 1;
493
494 no_merge:
495         req_set_nomerge(q, req);
496         return 0;
497 }
498
499 int ll_back_merge_fn(struct request_queue *q, struct request *req,
500                      struct bio *bio)
501 {
502         if (req_gap_back_merge(req, bio))
503                 return 0;
504         if (blk_integrity_rq(req) &&
505             integrity_req_gap_back_merge(req, bio))
506                 return 0;
507         if (blk_rq_sectors(req) + bio_sectors(bio) >
508             blk_rq_get_max_sectors(req, blk_rq_pos(req))) {
509                 req_set_nomerge(q, req);
510                 return 0;
511         }
512         if (!bio_flagged(req->biotail, BIO_SEG_VALID))
513                 blk_recount_segments(q, req->biotail);
514         if (!bio_flagged(bio, BIO_SEG_VALID))
515                 blk_recount_segments(q, bio);
516
517         return ll_new_hw_segment(q, req, bio);
518 }
519
520 int ll_front_merge_fn(struct request_queue *q, struct request *req,
521                       struct bio *bio)
522 {
523
524         if (req_gap_front_merge(req, bio))
525                 return 0;
526         if (blk_integrity_rq(req) &&
527             integrity_req_gap_front_merge(req, bio))
528                 return 0;
529         if (blk_rq_sectors(req) + bio_sectors(bio) >
530             blk_rq_get_max_sectors(req, bio->bi_iter.bi_sector)) {
531                 req_set_nomerge(q, req);
532                 return 0;
533         }
534         if (!bio_flagged(bio, BIO_SEG_VALID))
535                 blk_recount_segments(q, bio);
536         if (!bio_flagged(req->bio, BIO_SEG_VALID))
537                 blk_recount_segments(q, req->bio);
538
539         return ll_new_hw_segment(q, req, bio);
540 }
541
542 /*
543  * blk-mq uses req->special to carry normal driver per-request payload, it
544  * does not indicate a prepared command that we cannot merge with.
545  */
546 static bool req_no_special_merge(struct request *req)
547 {
548         struct request_queue *q = req->q;
549
550         return !q->mq_ops && req->special;
551 }
552
553 static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
554                                 struct request *next)
555 {
556         int total_phys_segments;
557         unsigned int seg_size =
558                 req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size;
559
560         /*
561          * First check if the either of the requests are re-queued
562          * requests.  Can't merge them if they are.
563          */
564         if (req_no_special_merge(req) || req_no_special_merge(next))
565                 return 0;
566
567         if (req_gap_back_merge(req, next->bio))
568                 return 0;
569
570         /*
571          * Will it become too large?
572          */
573         if ((blk_rq_sectors(req) + blk_rq_sectors(next)) >
574             blk_rq_get_max_sectors(req, blk_rq_pos(req)))
575                 return 0;
576
577         total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
578         if (blk_phys_contig_segment(q, req->biotail, next->bio)) {
579                 if (req->nr_phys_segments == 1)
580                         req->bio->bi_seg_front_size = seg_size;
581                 if (next->nr_phys_segments == 1)
582                         next->biotail->bi_seg_back_size = seg_size;
583                 total_phys_segments--;
584         }
585
586         if (total_phys_segments > queue_max_segments(q))
587                 return 0;
588
589         if (blk_integrity_merge_rq(q, req, next) == false)
590                 return 0;
591
592         /* Merge is OK... */
593         req->nr_phys_segments = total_phys_segments;
594         return 1;
595 }
596
597 /**
598  * blk_rq_set_mixed_merge - mark a request as mixed merge
599  * @rq: request to mark as mixed merge
600  *
601  * Description:
602  *     @rq is about to be mixed merged.  Make sure the attributes
603  *     which can be mixed are set in each bio and mark @rq as mixed
604  *     merged.
605  */
606 void blk_rq_set_mixed_merge(struct request *rq)
607 {
608         unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
609         struct bio *bio;
610
611         if (rq->rq_flags & RQF_MIXED_MERGE)
612                 return;
613
614         /*
615          * @rq will no longer represent mixable attributes for all the
616          * contained bios.  It will just track those of the first one.
617          * Distributes the attributs to each bio.
618          */
619         for (bio = rq->bio; bio; bio = bio->bi_next) {
620                 WARN_ON_ONCE((bio->bi_opf & REQ_FAILFAST_MASK) &&
621                              (bio->bi_opf & REQ_FAILFAST_MASK) != ff);
622                 bio->bi_opf |= ff;
623         }
624         rq->rq_flags |= RQF_MIXED_MERGE;
625 }
626
627 static void blk_account_io_merge(struct request *req)
628 {
629         if (blk_do_io_stat(req)) {
630                 struct hd_struct *part;
631                 int cpu;
632
633                 cpu = part_stat_lock();
634                 part = req->part;
635
636                 part_round_stats(cpu, part);
637                 part_dec_in_flight(part, rq_data_dir(req));
638
639                 hd_struct_put(part);
640                 part_stat_unlock();
641         }
642 }
643
644 /*
645  * For non-mq, this has to be called with the request spinlock acquired.
646  * For mq with scheduling, the appropriate queue wide lock should be held.
647  */
648 static struct request *attempt_merge(struct request_queue *q,
649                                      struct request *req, struct request *next)
650 {
651         if (!q->mq_ops)
652                 lockdep_assert_held(q->queue_lock);
653
654         if (!rq_mergeable(req) || !rq_mergeable(next))
655                 return NULL;
656
657         if (req_op(req) != req_op(next))
658                 return NULL;
659
660         /*
661          * not contiguous
662          */
663         if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next))
664                 return NULL;
665
666         if (rq_data_dir(req) != rq_data_dir(next)
667             || req->rq_disk != next->rq_disk
668             || req_no_special_merge(next))
669                 return NULL;
670
671         if (req_op(req) == REQ_OP_WRITE_SAME &&
672             !blk_write_same_mergeable(req->bio, next->bio))
673                 return NULL;
674
675         /*
676          * Don't allow merge of different write hints, or for a hint with
677          * non-hint IO.
678          */
679         if (req->write_hint != next->write_hint)
680                 return NULL;
681
682         /*
683          * If we are allowed to merge, then append bio list
684          * from next to rq and release next. merge_requests_fn
685          * will have updated segment counts, update sector
686          * counts here.
687          */
688         if (!ll_merge_requests_fn(q, req, next))
689                 return NULL;
690
691         /*
692          * If failfast settings disagree or any of the two is already
693          * a mixed merge, mark both as mixed before proceeding.  This
694          * makes sure that all involved bios have mixable attributes
695          * set properly.
696          */
697         if (((req->rq_flags | next->rq_flags) & RQF_MIXED_MERGE) ||
698             (req->cmd_flags & REQ_FAILFAST_MASK) !=
699             (next->cmd_flags & REQ_FAILFAST_MASK)) {
700                 blk_rq_set_mixed_merge(req);
701                 blk_rq_set_mixed_merge(next);
702         }
703
704         /*
705          * At this point we have either done a back merge
706          * or front merge. We need the smaller start_time of
707          * the merged requests to be the current request
708          * for accounting purposes.
709          */
710         if (time_after(req->start_time, next->start_time))
711                 req->start_time = next->start_time;
712
713         req->biotail->bi_next = next->bio;
714         req->biotail = next->biotail;
715
716         req->__data_len += blk_rq_bytes(next);
717
718         elv_merge_requests(q, req, next);
719
720         /*
721          * 'next' is going away, so update stats accordingly
722          */
723         blk_account_io_merge(next);
724
725         req->ioprio = ioprio_best(req->ioprio, next->ioprio);
726         if (blk_rq_cpu_valid(next))
727                 req->cpu = next->cpu;
728
729         /*
730          * ownership of bio passed from next to req, return 'next' for
731          * the caller to free
732          */
733         next->bio = NULL;
734         return next;
735 }
736
737 struct request *attempt_back_merge(struct request_queue *q, struct request *rq)
738 {
739         struct request *next = elv_latter_request(q, rq);
740
741         if (next)
742                 return attempt_merge(q, rq, next);
743
744         return NULL;
745 }
746
747 struct request *attempt_front_merge(struct request_queue *q, struct request *rq)
748 {
749         struct request *prev = elv_former_request(q, rq);
750
751         if (prev)
752                 return attempt_merge(q, prev, rq);
753
754         return NULL;
755 }
756
757 int blk_attempt_req_merge(struct request_queue *q, struct request *rq,
758                           struct request *next)
759 {
760         struct elevator_queue *e = q->elevator;
761         struct request *free;
762
763         if (!e->uses_mq && e->type->ops.sq.elevator_allow_rq_merge_fn)
764                 if (!e->type->ops.sq.elevator_allow_rq_merge_fn(q, rq, next))
765                         return 0;
766
767         free = attempt_merge(q, rq, next);
768         if (free) {
769                 __blk_put_request(q, free);
770                 return 1;
771         }
772
773         return 0;
774 }
775
776 bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
777 {
778         if (!rq_mergeable(rq) || !bio_mergeable(bio))
779                 return false;
780
781         if (req_op(rq) != bio_op(bio))
782                 return false;
783
784         /* different data direction or already started, don't merge */
785         if (bio_data_dir(bio) != rq_data_dir(rq))
786                 return false;
787
788         /* must be same device and not a special request */
789         if (rq->rq_disk != bio->bi_bdev->bd_disk || req_no_special_merge(rq))
790                 return false;
791
792         /* only merge integrity protected bio into ditto rq */
793         if (blk_integrity_merge_bio(rq->q, rq, bio) == false)
794                 return false;
795
796         /* must be using the same buffer */
797         if (req_op(rq) == REQ_OP_WRITE_SAME &&
798             !blk_write_same_mergeable(rq->bio, bio))
799                 return false;
800
801         /*
802          * Don't allow merge of different write hints, or for a hint with
803          * non-hint IO.
804          */
805         if (rq->write_hint != bio->bi_write_hint)
806                 return false;
807
808         return true;
809 }
810
811 enum elv_merge blk_try_merge(struct request *rq, struct bio *bio)
812 {
813         if (req_op(rq) == REQ_OP_DISCARD &&
814             queue_max_discard_segments(rq->q) > 1)
815                 return ELEVATOR_DISCARD_MERGE;
816         else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector)
817                 return ELEVATOR_BACK_MERGE;
818         else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector)
819                 return ELEVATOR_FRONT_MERGE;
820         return ELEVATOR_NO_MERGE;
821 }