Merge tag 'dm-4.3-changes' of git://git.kernel.org/pub/scm/linux/kernel/git/device...
[linux-2.6-microblaze.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 "blk.h"
11
12 static struct bio *blk_bio_discard_split(struct request_queue *q,
13                                          struct bio *bio,
14                                          struct bio_set *bs)
15 {
16         unsigned int max_discard_sectors, granularity;
17         int alignment;
18         sector_t tmp;
19         unsigned split_sectors;
20
21         /* Zero-sector (unknown) and one-sector granularities are the same.  */
22         granularity = max(q->limits.discard_granularity >> 9, 1U);
23
24         max_discard_sectors = min(q->limits.max_discard_sectors, UINT_MAX >> 9);
25         max_discard_sectors -= max_discard_sectors % granularity;
26
27         if (unlikely(!max_discard_sectors)) {
28                 /* XXX: warn */
29                 return NULL;
30         }
31
32         if (bio_sectors(bio) <= max_discard_sectors)
33                 return NULL;
34
35         split_sectors = max_discard_sectors;
36
37         /*
38          * If the next starting sector would be misaligned, stop the discard at
39          * the previous aligned sector.
40          */
41         alignment = (q->limits.discard_alignment >> 9) % granularity;
42
43         tmp = bio->bi_iter.bi_sector + split_sectors - alignment;
44         tmp = sector_div(tmp, granularity);
45
46         if (split_sectors > tmp)
47                 split_sectors -= tmp;
48
49         return bio_split(bio, split_sectors, GFP_NOIO, bs);
50 }
51
52 static struct bio *blk_bio_write_same_split(struct request_queue *q,
53                                             struct bio *bio,
54                                             struct bio_set *bs)
55 {
56         if (!q->limits.max_write_same_sectors)
57                 return NULL;
58
59         if (bio_sectors(bio) <= q->limits.max_write_same_sectors)
60                 return NULL;
61
62         return bio_split(bio, q->limits.max_write_same_sectors, GFP_NOIO, bs);
63 }
64
65 static struct bio *blk_bio_segment_split(struct request_queue *q,
66                                          struct bio *bio,
67                                          struct bio_set *bs)
68 {
69         struct bio *split;
70         struct bio_vec bv, bvprv;
71         struct bvec_iter iter;
72         unsigned seg_size = 0, nsegs = 0, sectors = 0;
73         int prev = 0;
74
75         bio_for_each_segment(bv, bio, iter) {
76                 sectors += bv.bv_len >> 9;
77
78                 if (sectors > queue_max_sectors(q))
79                         goto split;
80
81                 /*
82                  * If the queue doesn't support SG gaps and adding this
83                  * offset would create a gap, disallow it.
84                  */
85                 if (prev && bvec_gap_to_prev(q, &bvprv, bv.bv_offset))
86                         goto split;
87
88                 if (prev && blk_queue_cluster(q)) {
89                         if (seg_size + bv.bv_len > queue_max_segment_size(q))
90                                 goto new_segment;
91                         if (!BIOVEC_PHYS_MERGEABLE(&bvprv, &bv))
92                                 goto new_segment;
93                         if (!BIOVEC_SEG_BOUNDARY(q, &bvprv, &bv))
94                                 goto new_segment;
95
96                         seg_size += bv.bv_len;
97                         bvprv = bv;
98                         prev = 1;
99                         continue;
100                 }
101 new_segment:
102                 if (nsegs == queue_max_segments(q))
103                         goto split;
104
105                 nsegs++;
106                 bvprv = bv;
107                 prev = 1;
108                 seg_size = bv.bv_len;
109         }
110
111         return NULL;
112 split:
113         split = bio_clone_bioset(bio, GFP_NOIO, bs);
114
115         split->bi_iter.bi_size -= iter.bi_size;
116         bio->bi_iter = iter;
117
118         if (bio_integrity(bio)) {
119                 bio_integrity_advance(bio, split->bi_iter.bi_size);
120                 bio_integrity_trim(split, 0, bio_sectors(split));
121         }
122
123         return split;
124 }
125
126 void blk_queue_split(struct request_queue *q, struct bio **bio,
127                      struct bio_set *bs)
128 {
129         struct bio *split;
130
131         if ((*bio)->bi_rw & REQ_DISCARD)
132                 split = blk_bio_discard_split(q, *bio, bs);
133         else if ((*bio)->bi_rw & REQ_WRITE_SAME)
134                 split = blk_bio_write_same_split(q, *bio, bs);
135         else
136                 split = blk_bio_segment_split(q, *bio, q->bio_split);
137
138         if (split) {
139                 bio_chain(split, *bio);
140                 generic_make_request(*bio);
141                 *bio = split;
142         }
143 }
144 EXPORT_SYMBOL(blk_queue_split);
145
146 static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
147                                              struct bio *bio,
148                                              bool no_sg_merge)
149 {
150         struct bio_vec bv, bvprv = { NULL };
151         int cluster, prev = 0;
152         unsigned int seg_size, nr_phys_segs;
153         struct bio *fbio, *bbio;
154         struct bvec_iter iter;
155
156         if (!bio)
157                 return 0;
158
159         /*
160          * This should probably be returning 0, but blk_add_request_payload()
161          * (Christoph!!!!)
162          */
163         if (bio->bi_rw & REQ_DISCARD)
164                 return 1;
165
166         if (bio->bi_rw & REQ_WRITE_SAME)
167                 return 1;
168
169         fbio = bio;
170         cluster = blk_queue_cluster(q);
171         seg_size = 0;
172         nr_phys_segs = 0;
173         for_each_bio(bio) {
174                 bio_for_each_segment(bv, bio, iter) {
175                         /*
176                          * If SG merging is disabled, each bio vector is
177                          * a segment
178                          */
179                         if (no_sg_merge)
180                                 goto new_segment;
181
182                         if (prev && cluster) {
183                                 if (seg_size + bv.bv_len
184                                     > queue_max_segment_size(q))
185                                         goto new_segment;
186                                 if (!BIOVEC_PHYS_MERGEABLE(&bvprv, &bv))
187                                         goto new_segment;
188                                 if (!BIOVEC_SEG_BOUNDARY(q, &bvprv, &bv))
189                                         goto new_segment;
190
191                                 seg_size += bv.bv_len;
192                                 bvprv = bv;
193                                 continue;
194                         }
195 new_segment:
196                         if (nr_phys_segs == 1 && seg_size >
197                             fbio->bi_seg_front_size)
198                                 fbio->bi_seg_front_size = seg_size;
199
200                         nr_phys_segs++;
201                         bvprv = bv;
202                         prev = 1;
203                         seg_size = bv.bv_len;
204                 }
205                 bbio = bio;
206         }
207
208         if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size)
209                 fbio->bi_seg_front_size = seg_size;
210         if (seg_size > bbio->bi_seg_back_size)
211                 bbio->bi_seg_back_size = seg_size;
212
213         return nr_phys_segs;
214 }
215
216 void blk_recalc_rq_segments(struct request *rq)
217 {
218         bool no_sg_merge = !!test_bit(QUEUE_FLAG_NO_SG_MERGE,
219                         &rq->q->queue_flags);
220
221         rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio,
222                         no_sg_merge);
223 }
224
225 void blk_recount_segments(struct request_queue *q, struct bio *bio)
226 {
227         unsigned short seg_cnt;
228
229         /* estimate segment number by bi_vcnt for non-cloned bio */
230         if (bio_flagged(bio, BIO_CLONED))
231                 seg_cnt = bio_segments(bio);
232         else
233                 seg_cnt = bio->bi_vcnt;
234
235         if (test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags) &&
236                         (seg_cnt < queue_max_segments(q)))
237                 bio->bi_phys_segments = seg_cnt;
238         else {
239                 struct bio *nxt = bio->bi_next;
240
241                 bio->bi_next = NULL;
242                 bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio, false);
243                 bio->bi_next = nxt;
244         }
245
246         bio_set_flag(bio, BIO_SEG_VALID);
247 }
248 EXPORT_SYMBOL(blk_recount_segments);
249
250 static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
251                                    struct bio *nxt)
252 {
253         struct bio_vec end_bv = { NULL }, nxt_bv;
254         struct bvec_iter iter;
255
256         if (!blk_queue_cluster(q))
257                 return 0;
258
259         if (bio->bi_seg_back_size + nxt->bi_seg_front_size >
260             queue_max_segment_size(q))
261                 return 0;
262
263         if (!bio_has_data(bio))
264                 return 1;
265
266         bio_for_each_segment(end_bv, bio, iter)
267                 if (end_bv.bv_len == iter.bi_size)
268                         break;
269
270         nxt_bv = bio_iovec(nxt);
271
272         if (!BIOVEC_PHYS_MERGEABLE(&end_bv, &nxt_bv))
273                 return 0;
274
275         /*
276          * bio and nxt are contiguous in memory; check if the queue allows
277          * these two to be merged into one
278          */
279         if (BIOVEC_SEG_BOUNDARY(q, &end_bv, &nxt_bv))
280                 return 1;
281
282         return 0;
283 }
284
285 static inline void
286 __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec,
287                      struct scatterlist *sglist, struct bio_vec *bvprv,
288                      struct scatterlist **sg, int *nsegs, int *cluster)
289 {
290
291         int nbytes = bvec->bv_len;
292
293         if (*sg && *cluster) {
294                 if ((*sg)->length + nbytes > queue_max_segment_size(q))
295                         goto new_segment;
296
297                 if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
298                         goto new_segment;
299                 if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
300                         goto new_segment;
301
302                 (*sg)->length += nbytes;
303         } else {
304 new_segment:
305                 if (!*sg)
306                         *sg = sglist;
307                 else {
308                         /*
309                          * If the driver previously mapped a shorter
310                          * list, we could see a termination bit
311                          * prematurely unless it fully inits the sg
312                          * table on each mapping. We KNOW that there
313                          * must be more entries here or the driver
314                          * would be buggy, so force clear the
315                          * termination bit to avoid doing a full
316                          * sg_init_table() in drivers for each command.
317                          */
318                         sg_unmark_end(*sg);
319                         *sg = sg_next(*sg);
320                 }
321
322                 sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset);
323                 (*nsegs)++;
324         }
325         *bvprv = *bvec;
326 }
327
328 static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio,
329                              struct scatterlist *sglist,
330                              struct scatterlist **sg)
331 {
332         struct bio_vec bvec, bvprv = { NULL };
333         struct bvec_iter iter;
334         int nsegs, cluster;
335
336         nsegs = 0;
337         cluster = blk_queue_cluster(q);
338
339         if (bio->bi_rw & REQ_DISCARD) {
340                 /*
341                  * This is a hack - drivers should be neither modifying the
342                  * biovec, nor relying on bi_vcnt - but because of
343                  * blk_add_request_payload(), a discard bio may or may not have
344                  * a payload we need to set up here (thank you Christoph) and
345                  * bi_vcnt is really the only way of telling if we need to.
346                  */
347
348                 if (bio->bi_vcnt)
349                         goto single_segment;
350
351                 return 0;
352         }
353
354         if (bio->bi_rw & REQ_WRITE_SAME) {
355 single_segment:
356                 *sg = sglist;
357                 bvec = bio_iovec(bio);
358                 sg_set_page(*sg, bvec.bv_page, bvec.bv_len, bvec.bv_offset);
359                 return 1;
360         }
361
362         for_each_bio(bio)
363                 bio_for_each_segment(bvec, bio, iter)
364                         __blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg,
365                                              &nsegs, &cluster);
366
367         return nsegs;
368 }
369
370 /*
371  * map a request to scatterlist, return number of sg entries setup. Caller
372  * must make sure sg can hold rq->nr_phys_segments entries
373  */
374 int blk_rq_map_sg(struct request_queue *q, struct request *rq,
375                   struct scatterlist *sglist)
376 {
377         struct scatterlist *sg = NULL;
378         int nsegs = 0;
379
380         if (rq->bio)
381                 nsegs = __blk_bios_map_sg(q, rq->bio, sglist, &sg);
382
383         if (unlikely(rq->cmd_flags & REQ_COPY_USER) &&
384             (blk_rq_bytes(rq) & q->dma_pad_mask)) {
385                 unsigned int pad_len =
386                         (q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1;
387
388                 sg->length += pad_len;
389                 rq->extra_len += pad_len;
390         }
391
392         if (q->dma_drain_size && q->dma_drain_needed(rq)) {
393                 if (rq->cmd_flags & REQ_WRITE)
394                         memset(q->dma_drain_buffer, 0, q->dma_drain_size);
395
396                 sg_unmark_end(sg);
397                 sg = sg_next(sg);
398                 sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
399                             q->dma_drain_size,
400                             ((unsigned long)q->dma_drain_buffer) &
401                             (PAGE_SIZE - 1));
402                 nsegs++;
403                 rq->extra_len += q->dma_drain_size;
404         }
405
406         if (sg)
407                 sg_mark_end(sg);
408
409         return nsegs;
410 }
411 EXPORT_SYMBOL(blk_rq_map_sg);
412
413 static inline int ll_new_hw_segment(struct request_queue *q,
414                                     struct request *req,
415                                     struct bio *bio)
416 {
417         int nr_phys_segs = bio_phys_segments(q, bio);
418
419         if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q))
420                 goto no_merge;
421
422         if (blk_integrity_merge_bio(q, req, bio) == false)
423                 goto no_merge;
424
425         /*
426          * This will form the start of a new hw segment.  Bump both
427          * counters.
428          */
429         req->nr_phys_segments += nr_phys_segs;
430         return 1;
431
432 no_merge:
433         req->cmd_flags |= REQ_NOMERGE;
434         if (req == q->last_merge)
435                 q->last_merge = NULL;
436         return 0;
437 }
438
439 int ll_back_merge_fn(struct request_queue *q, struct request *req,
440                      struct bio *bio)
441 {
442         if (blk_rq_sectors(req) + bio_sectors(bio) >
443             blk_rq_get_max_sectors(req)) {
444                 req->cmd_flags |= REQ_NOMERGE;
445                 if (req == q->last_merge)
446                         q->last_merge = NULL;
447                 return 0;
448         }
449         if (!bio_flagged(req->biotail, BIO_SEG_VALID))
450                 blk_recount_segments(q, req->biotail);
451         if (!bio_flagged(bio, BIO_SEG_VALID))
452                 blk_recount_segments(q, bio);
453
454         return ll_new_hw_segment(q, req, bio);
455 }
456
457 int ll_front_merge_fn(struct request_queue *q, struct request *req,
458                       struct bio *bio)
459 {
460         if (blk_rq_sectors(req) + bio_sectors(bio) >
461             blk_rq_get_max_sectors(req)) {
462                 req->cmd_flags |= REQ_NOMERGE;
463                 if (req == q->last_merge)
464                         q->last_merge = NULL;
465                 return 0;
466         }
467         if (!bio_flagged(bio, BIO_SEG_VALID))
468                 blk_recount_segments(q, bio);
469         if (!bio_flagged(req->bio, BIO_SEG_VALID))
470                 blk_recount_segments(q, req->bio);
471
472         return ll_new_hw_segment(q, req, bio);
473 }
474
475 /*
476  * blk-mq uses req->special to carry normal driver per-request payload, it
477  * does not indicate a prepared command that we cannot merge with.
478  */
479 static bool req_no_special_merge(struct request *req)
480 {
481         struct request_queue *q = req->q;
482
483         return !q->mq_ops && req->special;
484 }
485
486 static int req_gap_to_prev(struct request *req, struct bio *next)
487 {
488         struct bio *prev = req->biotail;
489
490         return bvec_gap_to_prev(req->q, &prev->bi_io_vec[prev->bi_vcnt - 1],
491                         next->bi_io_vec[0].bv_offset);
492 }
493
494 static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
495                                 struct request *next)
496 {
497         int total_phys_segments;
498         unsigned int seg_size =
499                 req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size;
500
501         /*
502          * First check if the either of the requests are re-queued
503          * requests.  Can't merge them if they are.
504          */
505         if (req_no_special_merge(req) || req_no_special_merge(next))
506                 return 0;
507
508         if (req_gap_to_prev(req, next->bio))
509                 return 0;
510
511         /*
512          * Will it become too large?
513          */
514         if ((blk_rq_sectors(req) + blk_rq_sectors(next)) >
515             blk_rq_get_max_sectors(req))
516                 return 0;
517
518         total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
519         if (blk_phys_contig_segment(q, req->biotail, next->bio)) {
520                 if (req->nr_phys_segments == 1)
521                         req->bio->bi_seg_front_size = seg_size;
522                 if (next->nr_phys_segments == 1)
523                         next->biotail->bi_seg_back_size = seg_size;
524                 total_phys_segments--;
525         }
526
527         if (total_phys_segments > queue_max_segments(q))
528                 return 0;
529
530         if (blk_integrity_merge_rq(q, req, next) == false)
531                 return 0;
532
533         /* Merge is OK... */
534         req->nr_phys_segments = total_phys_segments;
535         return 1;
536 }
537
538 /**
539  * blk_rq_set_mixed_merge - mark a request as mixed merge
540  * @rq: request to mark as mixed merge
541  *
542  * Description:
543  *     @rq is about to be mixed merged.  Make sure the attributes
544  *     which can be mixed are set in each bio and mark @rq as mixed
545  *     merged.
546  */
547 void blk_rq_set_mixed_merge(struct request *rq)
548 {
549         unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
550         struct bio *bio;
551
552         if (rq->cmd_flags & REQ_MIXED_MERGE)
553                 return;
554
555         /*
556          * @rq will no longer represent mixable attributes for all the
557          * contained bios.  It will just track those of the first one.
558          * Distributes the attributs to each bio.
559          */
560         for (bio = rq->bio; bio; bio = bio->bi_next) {
561                 WARN_ON_ONCE((bio->bi_rw & REQ_FAILFAST_MASK) &&
562                              (bio->bi_rw & REQ_FAILFAST_MASK) != ff);
563                 bio->bi_rw |= ff;
564         }
565         rq->cmd_flags |= REQ_MIXED_MERGE;
566 }
567
568 static void blk_account_io_merge(struct request *req)
569 {
570         if (blk_do_io_stat(req)) {
571                 struct hd_struct *part;
572                 int cpu;
573
574                 cpu = part_stat_lock();
575                 part = req->part;
576
577                 part_round_stats(cpu, part);
578                 part_dec_in_flight(part, rq_data_dir(req));
579
580                 hd_struct_put(part);
581                 part_stat_unlock();
582         }
583 }
584
585 /*
586  * Has to be called with the request spinlock acquired
587  */
588 static int attempt_merge(struct request_queue *q, struct request *req,
589                           struct request *next)
590 {
591         if (!rq_mergeable(req) || !rq_mergeable(next))
592                 return 0;
593
594         if (!blk_check_merge_flags(req->cmd_flags, next->cmd_flags))
595                 return 0;
596
597         /*
598          * not contiguous
599          */
600         if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next))
601                 return 0;
602
603         if (rq_data_dir(req) != rq_data_dir(next)
604             || req->rq_disk != next->rq_disk
605             || req_no_special_merge(next))
606                 return 0;
607
608         if (req->cmd_flags & REQ_WRITE_SAME &&
609             !blk_write_same_mergeable(req->bio, next->bio))
610                 return 0;
611
612         /*
613          * If we are allowed to merge, then append bio list
614          * from next to rq and release next. merge_requests_fn
615          * will have updated segment counts, update sector
616          * counts here.
617          */
618         if (!ll_merge_requests_fn(q, req, next))
619                 return 0;
620
621         /*
622          * If failfast settings disagree or any of the two is already
623          * a mixed merge, mark both as mixed before proceeding.  This
624          * makes sure that all involved bios have mixable attributes
625          * set properly.
626          */
627         if ((req->cmd_flags | next->cmd_flags) & REQ_MIXED_MERGE ||
628             (req->cmd_flags & REQ_FAILFAST_MASK) !=
629             (next->cmd_flags & REQ_FAILFAST_MASK)) {
630                 blk_rq_set_mixed_merge(req);
631                 blk_rq_set_mixed_merge(next);
632         }
633
634         /*
635          * At this point we have either done a back merge
636          * or front merge. We need the smaller start_time of
637          * the merged requests to be the current request
638          * for accounting purposes.
639          */
640         if (time_after(req->start_time, next->start_time))
641                 req->start_time = next->start_time;
642
643         req->biotail->bi_next = next->bio;
644         req->biotail = next->biotail;
645
646         req->__data_len += blk_rq_bytes(next);
647
648         elv_merge_requests(q, req, next);
649
650         /*
651          * 'next' is going away, so update stats accordingly
652          */
653         blk_account_io_merge(next);
654
655         req->ioprio = ioprio_best(req->ioprio, next->ioprio);
656         if (blk_rq_cpu_valid(next))
657                 req->cpu = next->cpu;
658
659         /* owner-ship of bio passed from next to req */
660         next->bio = NULL;
661         __blk_put_request(q, next);
662         return 1;
663 }
664
665 int attempt_back_merge(struct request_queue *q, struct request *rq)
666 {
667         struct request *next = elv_latter_request(q, rq);
668
669         if (next)
670                 return attempt_merge(q, rq, next);
671
672         return 0;
673 }
674
675 int attempt_front_merge(struct request_queue *q, struct request *rq)
676 {
677         struct request *prev = elv_former_request(q, rq);
678
679         if (prev)
680                 return attempt_merge(q, prev, rq);
681
682         return 0;
683 }
684
685 int blk_attempt_req_merge(struct request_queue *q, struct request *rq,
686                           struct request *next)
687 {
688         return attempt_merge(q, rq, next);
689 }
690
691 bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
692 {
693         if (!rq_mergeable(rq) || !bio_mergeable(bio))
694                 return false;
695
696         if (!blk_check_merge_flags(rq->cmd_flags, bio->bi_rw))
697                 return false;
698
699         /* different data direction or already started, don't merge */
700         if (bio_data_dir(bio) != rq_data_dir(rq))
701                 return false;
702
703         /* must be same device and not a special request */
704         if (rq->rq_disk != bio->bi_bdev->bd_disk || req_no_special_merge(rq))
705                 return false;
706
707         /* only merge integrity protected bio into ditto rq */
708         if (blk_integrity_merge_bio(rq->q, rq, bio) == false)
709                 return false;
710
711         /* must be using the same buffer */
712         if (rq->cmd_flags & REQ_WRITE_SAME &&
713             !blk_write_same_mergeable(rq->bio, bio))
714                 return false;
715
716         /* Only check gaps if the bio carries data */
717         if (bio_has_data(bio) && req_gap_to_prev(rq, bio))
718                 return false;
719
720         return true;
721 }
722
723 int blk_try_merge(struct request *rq, struct bio *bio)
724 {
725         if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector)
726                 return ELEVATOR_BACK_MERGE;
727         else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector)
728                 return ELEVATOR_FRONT_MERGE;
729         return ELEVATOR_NO_MERGE;
730 }