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