Merge tag 'sound-4.2-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/tiwai...
[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 unsigned int __blk_recalc_rq_segments(struct request_queue *q,
13                                              struct bio *bio,
14                                              bool no_sg_merge)
15 {
16         struct bio_vec bv, bvprv = { NULL };
17         int cluster, high, highprv = 1;
18         unsigned int seg_size, nr_phys_segs;
19         struct bio *fbio, *bbio;
20         struct bvec_iter iter;
21
22         if (!bio)
23                 return 0;
24
25         /*
26          * This should probably be returning 0, but blk_add_request_payload()
27          * (Christoph!!!!)
28          */
29         if (bio->bi_rw & REQ_DISCARD)
30                 return 1;
31
32         if (bio->bi_rw & REQ_WRITE_SAME)
33                 return 1;
34
35         fbio = bio;
36         cluster = blk_queue_cluster(q);
37         seg_size = 0;
38         nr_phys_segs = 0;
39         high = 0;
40         for_each_bio(bio) {
41                 bio_for_each_segment(bv, bio, iter) {
42                         /*
43                          * If SG merging is disabled, each bio vector is
44                          * a segment
45                          */
46                         if (no_sg_merge)
47                                 goto new_segment;
48
49                         /*
50                          * the trick here is making sure that a high page is
51                          * never considered part of another segment, since
52                          * that might change with the bounce page.
53                          */
54                         high = page_to_pfn(bv.bv_page) > queue_bounce_pfn(q);
55                         if (!high && !highprv && cluster) {
56                                 if (seg_size + bv.bv_len
57                                     > queue_max_segment_size(q))
58                                         goto new_segment;
59                                 if (!BIOVEC_PHYS_MERGEABLE(&bvprv, &bv))
60                                         goto new_segment;
61                                 if (!BIOVEC_SEG_BOUNDARY(q, &bvprv, &bv))
62                                         goto new_segment;
63
64                                 seg_size += bv.bv_len;
65                                 bvprv = bv;
66                                 continue;
67                         }
68 new_segment:
69                         if (nr_phys_segs == 1 && seg_size >
70                             fbio->bi_seg_front_size)
71                                 fbio->bi_seg_front_size = seg_size;
72
73                         nr_phys_segs++;
74                         bvprv = bv;
75                         seg_size = bv.bv_len;
76                         highprv = high;
77                 }
78                 bbio = bio;
79         }
80
81         if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size)
82                 fbio->bi_seg_front_size = seg_size;
83         if (seg_size > bbio->bi_seg_back_size)
84                 bbio->bi_seg_back_size = seg_size;
85
86         return nr_phys_segs;
87 }
88
89 void blk_recalc_rq_segments(struct request *rq)
90 {
91         bool no_sg_merge = !!test_bit(QUEUE_FLAG_NO_SG_MERGE,
92                         &rq->q->queue_flags);
93
94         rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio,
95                         no_sg_merge);
96 }
97
98 void blk_recount_segments(struct request_queue *q, struct bio *bio)
99 {
100         unsigned short seg_cnt;
101
102         /* estimate segment number by bi_vcnt for non-cloned bio */
103         if (bio_flagged(bio, BIO_CLONED))
104                 seg_cnt = bio_segments(bio);
105         else
106                 seg_cnt = bio->bi_vcnt;
107
108         if (test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags) &&
109                         (seg_cnt < queue_max_segments(q)))
110                 bio->bi_phys_segments = seg_cnt;
111         else {
112                 struct bio *nxt = bio->bi_next;
113
114                 bio->bi_next = NULL;
115                 bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio, false);
116                 bio->bi_next = nxt;
117         }
118
119         bio->bi_flags |= (1 << BIO_SEG_VALID);
120 }
121 EXPORT_SYMBOL(blk_recount_segments);
122
123 static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
124                                    struct bio *nxt)
125 {
126         struct bio_vec end_bv = { NULL }, nxt_bv;
127         struct bvec_iter iter;
128
129         if (!blk_queue_cluster(q))
130                 return 0;
131
132         if (bio->bi_seg_back_size + nxt->bi_seg_front_size >
133             queue_max_segment_size(q))
134                 return 0;
135
136         if (!bio_has_data(bio))
137                 return 1;
138
139         bio_for_each_segment(end_bv, bio, iter)
140                 if (end_bv.bv_len == iter.bi_size)
141                         break;
142
143         nxt_bv = bio_iovec(nxt);
144
145         if (!BIOVEC_PHYS_MERGEABLE(&end_bv, &nxt_bv))
146                 return 0;
147
148         /*
149          * bio and nxt are contiguous in memory; check if the queue allows
150          * these two to be merged into one
151          */
152         if (BIOVEC_SEG_BOUNDARY(q, &end_bv, &nxt_bv))
153                 return 1;
154
155         return 0;
156 }
157
158 static inline void
159 __blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec,
160                      struct scatterlist *sglist, struct bio_vec *bvprv,
161                      struct scatterlist **sg, int *nsegs, int *cluster)
162 {
163
164         int nbytes = bvec->bv_len;
165
166         if (*sg && *cluster) {
167                 if ((*sg)->length + nbytes > queue_max_segment_size(q))
168                         goto new_segment;
169
170                 if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
171                         goto new_segment;
172                 if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
173                         goto new_segment;
174
175                 (*sg)->length += nbytes;
176         } else {
177 new_segment:
178                 if (!*sg)
179                         *sg = sglist;
180                 else {
181                         /*
182                          * If the driver previously mapped a shorter
183                          * list, we could see a termination bit
184                          * prematurely unless it fully inits the sg
185                          * table on each mapping. We KNOW that there
186                          * must be more entries here or the driver
187                          * would be buggy, so force clear the
188                          * termination bit to avoid doing a full
189                          * sg_init_table() in drivers for each command.
190                          */
191                         sg_unmark_end(*sg);
192                         *sg = sg_next(*sg);
193                 }
194
195                 sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset);
196                 (*nsegs)++;
197         }
198         *bvprv = *bvec;
199 }
200
201 static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio,
202                              struct scatterlist *sglist,
203                              struct scatterlist **sg)
204 {
205         struct bio_vec bvec, bvprv = { NULL };
206         struct bvec_iter iter;
207         int nsegs, cluster;
208
209         nsegs = 0;
210         cluster = blk_queue_cluster(q);
211
212         if (bio->bi_rw & REQ_DISCARD) {
213                 /*
214                  * This is a hack - drivers should be neither modifying the
215                  * biovec, nor relying on bi_vcnt - but because of
216                  * blk_add_request_payload(), a discard bio may or may not have
217                  * a payload we need to set up here (thank you Christoph) and
218                  * bi_vcnt is really the only way of telling if we need to.
219                  */
220
221                 if (bio->bi_vcnt)
222                         goto single_segment;
223
224                 return 0;
225         }
226
227         if (bio->bi_rw & REQ_WRITE_SAME) {
228 single_segment:
229                 *sg = sglist;
230                 bvec = bio_iovec(bio);
231                 sg_set_page(*sg, bvec.bv_page, bvec.bv_len, bvec.bv_offset);
232                 return 1;
233         }
234
235         for_each_bio(bio)
236                 bio_for_each_segment(bvec, bio, iter)
237                         __blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg,
238                                              &nsegs, &cluster);
239
240         return nsegs;
241 }
242
243 /*
244  * map a request to scatterlist, return number of sg entries setup. Caller
245  * must make sure sg can hold rq->nr_phys_segments entries
246  */
247 int blk_rq_map_sg(struct request_queue *q, struct request *rq,
248                   struct scatterlist *sglist)
249 {
250         struct scatterlist *sg = NULL;
251         int nsegs = 0;
252
253         if (rq->bio)
254                 nsegs = __blk_bios_map_sg(q, rq->bio, sglist, &sg);
255
256         if (unlikely(rq->cmd_flags & REQ_COPY_USER) &&
257             (blk_rq_bytes(rq) & q->dma_pad_mask)) {
258                 unsigned int pad_len =
259                         (q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1;
260
261                 sg->length += pad_len;
262                 rq->extra_len += pad_len;
263         }
264
265         if (q->dma_drain_size && q->dma_drain_needed(rq)) {
266                 if (rq->cmd_flags & REQ_WRITE)
267                         memset(q->dma_drain_buffer, 0, q->dma_drain_size);
268
269                 sg->page_link &= ~0x02;
270                 sg = sg_next(sg);
271                 sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
272                             q->dma_drain_size,
273                             ((unsigned long)q->dma_drain_buffer) &
274                             (PAGE_SIZE - 1));
275                 nsegs++;
276                 rq->extra_len += q->dma_drain_size;
277         }
278
279         if (sg)
280                 sg_mark_end(sg);
281
282         return nsegs;
283 }
284 EXPORT_SYMBOL(blk_rq_map_sg);
285
286 static inline int ll_new_hw_segment(struct request_queue *q,
287                                     struct request *req,
288                                     struct bio *bio)
289 {
290         int nr_phys_segs = bio_phys_segments(q, bio);
291
292         if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q))
293                 goto no_merge;
294
295         if (blk_integrity_merge_bio(q, req, bio) == false)
296                 goto no_merge;
297
298         /*
299          * This will form the start of a new hw segment.  Bump both
300          * counters.
301          */
302         req->nr_phys_segments += nr_phys_segs;
303         return 1;
304
305 no_merge:
306         req->cmd_flags |= REQ_NOMERGE;
307         if (req == q->last_merge)
308                 q->last_merge = NULL;
309         return 0;
310 }
311
312 int ll_back_merge_fn(struct request_queue *q, struct request *req,
313                      struct bio *bio)
314 {
315         if (blk_rq_sectors(req) + bio_sectors(bio) >
316             blk_rq_get_max_sectors(req)) {
317                 req->cmd_flags |= REQ_NOMERGE;
318                 if (req == q->last_merge)
319                         q->last_merge = NULL;
320                 return 0;
321         }
322         if (!bio_flagged(req->biotail, BIO_SEG_VALID))
323                 blk_recount_segments(q, req->biotail);
324         if (!bio_flagged(bio, BIO_SEG_VALID))
325                 blk_recount_segments(q, bio);
326
327         return ll_new_hw_segment(q, req, bio);
328 }
329
330 int ll_front_merge_fn(struct request_queue *q, struct request *req,
331                       struct bio *bio)
332 {
333         if (blk_rq_sectors(req) + bio_sectors(bio) >
334             blk_rq_get_max_sectors(req)) {
335                 req->cmd_flags |= REQ_NOMERGE;
336                 if (req == q->last_merge)
337                         q->last_merge = NULL;
338                 return 0;
339         }
340         if (!bio_flagged(bio, BIO_SEG_VALID))
341                 blk_recount_segments(q, bio);
342         if (!bio_flagged(req->bio, BIO_SEG_VALID))
343                 blk_recount_segments(q, req->bio);
344
345         return ll_new_hw_segment(q, req, bio);
346 }
347
348 /*
349  * blk-mq uses req->special to carry normal driver per-request payload, it
350  * does not indicate a prepared command that we cannot merge with.
351  */
352 static bool req_no_special_merge(struct request *req)
353 {
354         struct request_queue *q = req->q;
355
356         return !q->mq_ops && req->special;
357 }
358
359 static int req_gap_to_prev(struct request *req, struct request *next)
360 {
361         struct bio *prev = req->biotail;
362
363         return bvec_gap_to_prev(&prev->bi_io_vec[prev->bi_vcnt - 1],
364                                 next->bio->bi_io_vec[0].bv_offset);
365 }
366
367 static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
368                                 struct request *next)
369 {
370         int total_phys_segments;
371         unsigned int seg_size =
372                 req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size;
373
374         /*
375          * First check if the either of the requests are re-queued
376          * requests.  Can't merge them if they are.
377          */
378         if (req_no_special_merge(req) || req_no_special_merge(next))
379                 return 0;
380
381         if (test_bit(QUEUE_FLAG_SG_GAPS, &q->queue_flags) &&
382             req_gap_to_prev(req, next))
383                 return 0;
384
385         /*
386          * Will it become too large?
387          */
388         if ((blk_rq_sectors(req) + blk_rq_sectors(next)) >
389             blk_rq_get_max_sectors(req))
390                 return 0;
391
392         total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
393         if (blk_phys_contig_segment(q, req->biotail, next->bio)) {
394                 if (req->nr_phys_segments == 1)
395                         req->bio->bi_seg_front_size = seg_size;
396                 if (next->nr_phys_segments == 1)
397                         next->biotail->bi_seg_back_size = seg_size;
398                 total_phys_segments--;
399         }
400
401         if (total_phys_segments > queue_max_segments(q))
402                 return 0;
403
404         if (blk_integrity_merge_rq(q, req, next) == false)
405                 return 0;
406
407         /* Merge is OK... */
408         req->nr_phys_segments = total_phys_segments;
409         return 1;
410 }
411
412 /**
413  * blk_rq_set_mixed_merge - mark a request as mixed merge
414  * @rq: request to mark as mixed merge
415  *
416  * Description:
417  *     @rq is about to be mixed merged.  Make sure the attributes
418  *     which can be mixed are set in each bio and mark @rq as mixed
419  *     merged.
420  */
421 void blk_rq_set_mixed_merge(struct request *rq)
422 {
423         unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
424         struct bio *bio;
425
426         if (rq->cmd_flags & REQ_MIXED_MERGE)
427                 return;
428
429         /*
430          * @rq will no longer represent mixable attributes for all the
431          * contained bios.  It will just track those of the first one.
432          * Distributes the attributs to each bio.
433          */
434         for (bio = rq->bio; bio; bio = bio->bi_next) {
435                 WARN_ON_ONCE((bio->bi_rw & REQ_FAILFAST_MASK) &&
436                              (bio->bi_rw & REQ_FAILFAST_MASK) != ff);
437                 bio->bi_rw |= ff;
438         }
439         rq->cmd_flags |= REQ_MIXED_MERGE;
440 }
441
442 static void blk_account_io_merge(struct request *req)
443 {
444         if (blk_do_io_stat(req)) {
445                 struct hd_struct *part;
446                 int cpu;
447
448                 cpu = part_stat_lock();
449                 part = req->part;
450
451                 part_round_stats(cpu, part);
452                 part_dec_in_flight(part, rq_data_dir(req));
453
454                 hd_struct_put(part);
455                 part_stat_unlock();
456         }
457 }
458
459 /*
460  * Has to be called with the request spinlock acquired
461  */
462 static int attempt_merge(struct request_queue *q, struct request *req,
463                           struct request *next)
464 {
465         if (!rq_mergeable(req) || !rq_mergeable(next))
466                 return 0;
467
468         if (!blk_check_merge_flags(req->cmd_flags, next->cmd_flags))
469                 return 0;
470
471         /*
472          * not contiguous
473          */
474         if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next))
475                 return 0;
476
477         if (rq_data_dir(req) != rq_data_dir(next)
478             || req->rq_disk != next->rq_disk
479             || req_no_special_merge(next))
480                 return 0;
481
482         if (req->cmd_flags & REQ_WRITE_SAME &&
483             !blk_write_same_mergeable(req->bio, next->bio))
484                 return 0;
485
486         /*
487          * If we are allowed to merge, then append bio list
488          * from next to rq and release next. merge_requests_fn
489          * will have updated segment counts, update sector
490          * counts here.
491          */
492         if (!ll_merge_requests_fn(q, req, next))
493                 return 0;
494
495         /*
496          * If failfast settings disagree or any of the two is already
497          * a mixed merge, mark both as mixed before proceeding.  This
498          * makes sure that all involved bios have mixable attributes
499          * set properly.
500          */
501         if ((req->cmd_flags | next->cmd_flags) & REQ_MIXED_MERGE ||
502             (req->cmd_flags & REQ_FAILFAST_MASK) !=
503             (next->cmd_flags & REQ_FAILFAST_MASK)) {
504                 blk_rq_set_mixed_merge(req);
505                 blk_rq_set_mixed_merge(next);
506         }
507
508         /*
509          * At this point we have either done a back merge
510          * or front merge. We need the smaller start_time of
511          * the merged requests to be the current request
512          * for accounting purposes.
513          */
514         if (time_after(req->start_time, next->start_time))
515                 req->start_time = next->start_time;
516
517         req->biotail->bi_next = next->bio;
518         req->biotail = next->biotail;
519
520         req->__data_len += blk_rq_bytes(next);
521
522         elv_merge_requests(q, req, next);
523
524         /*
525          * 'next' is going away, so update stats accordingly
526          */
527         blk_account_io_merge(next);
528
529         req->ioprio = ioprio_best(req->ioprio, next->ioprio);
530         if (blk_rq_cpu_valid(next))
531                 req->cpu = next->cpu;
532
533         /* owner-ship of bio passed from next to req */
534         next->bio = NULL;
535         __blk_put_request(q, next);
536         return 1;
537 }
538
539 int attempt_back_merge(struct request_queue *q, struct request *rq)
540 {
541         struct request *next = elv_latter_request(q, rq);
542
543         if (next)
544                 return attempt_merge(q, rq, next);
545
546         return 0;
547 }
548
549 int attempt_front_merge(struct request_queue *q, struct request *rq)
550 {
551         struct request *prev = elv_former_request(q, rq);
552
553         if (prev)
554                 return attempt_merge(q, prev, rq);
555
556         return 0;
557 }
558
559 int blk_attempt_req_merge(struct request_queue *q, struct request *rq,
560                           struct request *next)
561 {
562         return attempt_merge(q, rq, next);
563 }
564
565 bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
566 {
567         struct request_queue *q = rq->q;
568
569         if (!rq_mergeable(rq) || !bio_mergeable(bio))
570                 return false;
571
572         if (!blk_check_merge_flags(rq->cmd_flags, bio->bi_rw))
573                 return false;
574
575         /* different data direction or already started, don't merge */
576         if (bio_data_dir(bio) != rq_data_dir(rq))
577                 return false;
578
579         /* must be same device and not a special request */
580         if (rq->rq_disk != bio->bi_bdev->bd_disk || req_no_special_merge(rq))
581                 return false;
582
583         /* only merge integrity protected bio into ditto rq */
584         if (blk_integrity_merge_bio(rq->q, rq, bio) == false)
585                 return false;
586
587         /* must be using the same buffer */
588         if (rq->cmd_flags & REQ_WRITE_SAME &&
589             !blk_write_same_mergeable(rq->bio, bio))
590                 return false;
591
592         /* Only check gaps if the bio carries data */
593         if (q->queue_flags & (1 << QUEUE_FLAG_SG_GAPS) && bio_has_data(bio)) {
594                 struct bio_vec *bprev;
595
596                 bprev = &rq->biotail->bi_io_vec[rq->biotail->bi_vcnt - 1];
597                 if (bvec_gap_to_prev(bprev, bio->bi_io_vec[0].bv_offset))
598                         return false;
599         }
600
601         return true;
602 }
603
604 int blk_try_merge(struct request *rq, struct bio *bio)
605 {
606         if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector)
607                 return ELEVATOR_BACK_MERGE;
608         else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector)
609                 return ELEVATOR_FRONT_MERGE;
610         return ELEVATOR_NO_MERGE;
611 }