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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
12static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
13 struct bio *bio)
14{
15 struct bio_vec *bv, *bvprv = NULL;
16 int cluster, i, high, highprv = 1;
17 unsigned int seg_size, nr_phys_segs;
18 struct bio *fbio, *bbio;
19
20 if (!bio)
21 return 0;
22
23 fbio = bio;
24 cluster = blk_queue_cluster(q);
25 seg_size = 0;
26 nr_phys_segs = 0;
27 for_each_bio(bio) {
28 bio_for_each_segment(bv, bio, i) {
29 /*
30 * the trick here is making sure that a high page is
31 * never considered part of another segment, since that
32 * might change with the bounce page.
33 */
34 high = page_to_pfn(bv->bv_page) > queue_bounce_pfn(q);
35 if (high || highprv)
36 goto new_segment;
37 if (cluster) {
38 if (seg_size + bv->bv_len
39 > queue_max_segment_size(q))
40 goto new_segment;
41 if (!BIOVEC_PHYS_MERGEABLE(bvprv, bv))
42 goto new_segment;
43 if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bv))
44 goto new_segment;
45
46 seg_size += bv->bv_len;
47 bvprv = bv;
48 continue;
49 }
50new_segment:
51 if (nr_phys_segs == 1 && seg_size >
52 fbio->bi_seg_front_size)
53 fbio->bi_seg_front_size = seg_size;
54
55 nr_phys_segs++;
56 bvprv = bv;
57 seg_size = bv->bv_len;
58 highprv = high;
59 }
60 bbio = bio;
61 }
62
63 if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size)
64 fbio->bi_seg_front_size = seg_size;
65 if (seg_size > bbio->bi_seg_back_size)
66 bbio->bi_seg_back_size = seg_size;
67
68 return nr_phys_segs;
69}
70
71void blk_recalc_rq_segments(struct request *rq)
72{
73 rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio);
74}
75
76void blk_recount_segments(struct request_queue *q, struct bio *bio)
77{
78 struct bio *nxt = bio->bi_next;
79
80 bio->bi_next = NULL;
81 bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio);
82 bio->bi_next = nxt;
83 bio->bi_flags |= (1 << BIO_SEG_VALID);
84}
85EXPORT_SYMBOL(blk_recount_segments);
86
87static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
88 struct bio *nxt)
89{
90 if (!blk_queue_cluster(q))
91 return 0;
92
93 if (bio->bi_seg_back_size + nxt->bi_seg_front_size >
94 queue_max_segment_size(q))
95 return 0;
96
97 if (!bio_has_data(bio))
98 return 1;
99
100 if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)))
101 return 0;
102
103 /*
104 * bio and nxt are contiguous in memory; check if the queue allows
105 * these two to be merged into one
106 */
107 if (BIO_SEG_BOUNDARY(q, bio, nxt))
108 return 1;
109
110 return 0;
111}
112
113/*
114 * map a request to scatterlist, return number of sg entries setup. Caller
115 * must make sure sg can hold rq->nr_phys_segments entries
116 */
117int blk_rq_map_sg(struct request_queue *q, struct request *rq,
118 struct scatterlist *sglist)
119{
120 struct bio_vec *bvec, *bvprv;
121 struct req_iterator iter;
122 struct scatterlist *sg;
123 int nsegs, cluster;
124
125 nsegs = 0;
126 cluster = blk_queue_cluster(q);
127
128 /*
129 * for each bio in rq
130 */
131 bvprv = NULL;
132 sg = NULL;
133 rq_for_each_segment(bvec, rq, iter) {
134 int nbytes = bvec->bv_len;
135
136 if (bvprv && cluster) {
137 if (sg->length + nbytes > queue_max_segment_size(q))
138 goto new_segment;
139
140 if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
141 goto new_segment;
142 if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
143 goto new_segment;
144
145 sg->length += nbytes;
146 } else {
147new_segment:
148 if (!sg)
149 sg = sglist;
150 else {
151 /*
152 * If the driver previously mapped a shorter
153 * list, we could see a termination bit
154 * prematurely unless it fully inits the sg
155 * table on each mapping. We KNOW that there
156 * must be more entries here or the driver
157 * would be buggy, so force clear the
158 * termination bit to avoid doing a full
159 * sg_init_table() in drivers for each command.
160 */
161 sg->page_link &= ~0x02;
162 sg = sg_next(sg);
163 }
164
165 sg_set_page(sg, bvec->bv_page, nbytes, bvec->bv_offset);
166 nsegs++;
167 }
168 bvprv = bvec;
169 } /* segments in rq */
170
171
172 if (unlikely(rq->cmd_flags & REQ_COPY_USER) &&
173 (blk_rq_bytes(rq) & q->dma_pad_mask)) {
174 unsigned int pad_len =
175 (q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1;
176
177 sg->length += pad_len;
178 rq->extra_len += pad_len;
179 }
180
181 if (q->dma_drain_size && q->dma_drain_needed(rq)) {
182 if (rq->cmd_flags & REQ_WRITE)
183 memset(q->dma_drain_buffer, 0, q->dma_drain_size);
184
185 sg->page_link &= ~0x02;
186 sg = sg_next(sg);
187 sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
188 q->dma_drain_size,
189 ((unsigned long)q->dma_drain_buffer) &
190 (PAGE_SIZE - 1));
191 nsegs++;
192 rq->extra_len += q->dma_drain_size;
193 }
194
195 if (sg)
196 sg_mark_end(sg);
197
198 return nsegs;
199}
200EXPORT_SYMBOL(blk_rq_map_sg);
201
202static inline int ll_new_hw_segment(struct request_queue *q,
203 struct request *req,
204 struct bio *bio)
205{
206 int nr_phys_segs = bio_phys_segments(q, bio);
207
208 if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q))
209 goto no_merge;
210
211 if (bio_integrity(bio) && blk_integrity_merge_bio(q, req, bio))
212 goto no_merge;
213
214 /*
215 * This will form the start of a new hw segment. Bump both
216 * counters.
217 */
218 req->nr_phys_segments += nr_phys_segs;
219 return 1;
220
221no_merge:
222 req->cmd_flags |= REQ_NOMERGE;
223 if (req == q->last_merge)
224 q->last_merge = NULL;
225 return 0;
226}
227
228int ll_back_merge_fn(struct request_queue *q, struct request *req,
229 struct bio *bio)
230{
231 unsigned short max_sectors;
232
233 if (unlikely(req->cmd_type == REQ_TYPE_BLOCK_PC))
234 max_sectors = queue_max_hw_sectors(q);
235 else
236 max_sectors = queue_max_sectors(q);
237
238 if (blk_rq_sectors(req) + bio_sectors(bio) > max_sectors) {
239 req->cmd_flags |= REQ_NOMERGE;
240 if (req == q->last_merge)
241 q->last_merge = NULL;
242 return 0;
243 }
244 if (!bio_flagged(req->biotail, BIO_SEG_VALID))
245 blk_recount_segments(q, req->biotail);
246 if (!bio_flagged(bio, BIO_SEG_VALID))
247 blk_recount_segments(q, bio);
248
249 return ll_new_hw_segment(q, req, bio);
250}
251
252int ll_front_merge_fn(struct request_queue *q, struct request *req,
253 struct bio *bio)
254{
255 unsigned short max_sectors;
256
257 if (unlikely(req->cmd_type == REQ_TYPE_BLOCK_PC))
258 max_sectors = queue_max_hw_sectors(q);
259 else
260 max_sectors = queue_max_sectors(q);
261
262
263 if (blk_rq_sectors(req) + bio_sectors(bio) > max_sectors) {
264 req->cmd_flags |= REQ_NOMERGE;
265 if (req == q->last_merge)
266 q->last_merge = NULL;
267 return 0;
268 }
269 if (!bio_flagged(bio, BIO_SEG_VALID))
270 blk_recount_segments(q, bio);
271 if (!bio_flagged(req->bio, BIO_SEG_VALID))
272 blk_recount_segments(q, req->bio);
273
274 return ll_new_hw_segment(q, req, bio);
275}
276
277static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
278 struct request *next)
279{
280 int total_phys_segments;
281 unsigned int seg_size =
282 req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size;
283
284 /*
285 * First check if the either of the requests are re-queued
286 * requests. Can't merge them if they are.
287 */
288 if (req->special || next->special)
289 return 0;
290
291 /*
292 * Will it become too large?
293 */
294 if ((blk_rq_sectors(req) + blk_rq_sectors(next)) > queue_max_sectors(q))
295 return 0;
296
297 total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
298 if (blk_phys_contig_segment(q, req->biotail, next->bio)) {
299 if (req->nr_phys_segments == 1)
300 req->bio->bi_seg_front_size = seg_size;
301 if (next->nr_phys_segments == 1)
302 next->biotail->bi_seg_back_size = seg_size;
303 total_phys_segments--;
304 }
305
306 if (total_phys_segments > queue_max_segments(q))
307 return 0;
308
309 if (blk_integrity_rq(req) && blk_integrity_merge_rq(q, req, next))
310 return 0;
311
312 /* Merge is OK... */
313 req->nr_phys_segments = total_phys_segments;
314 return 1;
315}
316
317/**
318 * blk_rq_set_mixed_merge - mark a request as mixed merge
319 * @rq: request to mark as mixed merge
320 *
321 * Description:
322 * @rq is about to be mixed merged. Make sure the attributes
323 * which can be mixed are set in each bio and mark @rq as mixed
324 * merged.
325 */
326void blk_rq_set_mixed_merge(struct request *rq)
327{
328 unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
329 struct bio *bio;
330
331 if (rq->cmd_flags & REQ_MIXED_MERGE)
332 return;
333
334 /*
335 * @rq will no longer represent mixable attributes for all the
336 * contained bios. It will just track those of the first one.
337 * Distributes the attributs to each bio.
338 */
339 for (bio = rq->bio; bio; bio = bio->bi_next) {
340 WARN_ON_ONCE((bio->bi_rw & REQ_FAILFAST_MASK) &&
341 (bio->bi_rw & REQ_FAILFAST_MASK) != ff);
342 bio->bi_rw |= ff;
343 }
344 rq->cmd_flags |= REQ_MIXED_MERGE;
345}
346
347static void blk_account_io_merge(struct request *req)
348{
349 if (blk_do_io_stat(req)) {
350 struct hd_struct *part;
351 int cpu;
352
353 cpu = part_stat_lock();
354 part = req->part;
355
356 part_round_stats(cpu, part);
357 part_dec_in_flight(part, rq_data_dir(req));
358
359 hd_struct_put(part);
360 part_stat_unlock();
361 }
362}
363
364/*
365 * Has to be called with the request spinlock acquired
366 */
367static int attempt_merge(struct request_queue *q, struct request *req,
368 struct request *next)
369{
370 if (!rq_mergeable(req) || !rq_mergeable(next))
371 return 0;
372
373 /*
374 * Don't merge file system requests and discard requests
375 */
376 if ((req->cmd_flags & REQ_DISCARD) != (next->cmd_flags & REQ_DISCARD))
377 return 0;
378
379 /*
380 * Don't merge discard requests and secure discard requests
381 */
382 if ((req->cmd_flags & REQ_SECURE) != (next->cmd_flags & REQ_SECURE))
383 return 0;
384
385 /*
386 * not contiguous
387 */
388 if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next))
389 return 0;
390
391 if (rq_data_dir(req) != rq_data_dir(next)
392 || req->rq_disk != next->rq_disk
393 || next->special)
394 return 0;
395
396 /*
397 * If we are allowed to merge, then append bio list
398 * from next to rq and release next. merge_requests_fn
399 * will have updated segment counts, update sector
400 * counts here.
401 */
402 if (!ll_merge_requests_fn(q, req, next))
403 return 0;
404
405 /*
406 * If failfast settings disagree or any of the two is already
407 * a mixed merge, mark both as mixed before proceeding. This
408 * makes sure that all involved bios have mixable attributes
409 * set properly.
410 */
411 if ((req->cmd_flags | next->cmd_flags) & REQ_MIXED_MERGE ||
412 (req->cmd_flags & REQ_FAILFAST_MASK) !=
413 (next->cmd_flags & REQ_FAILFAST_MASK)) {
414 blk_rq_set_mixed_merge(req);
415 blk_rq_set_mixed_merge(next);
416 }
417
418 /*
419 * At this point we have either done a back merge
420 * or front merge. We need the smaller start_time of
421 * the merged requests to be the current request
422 * for accounting purposes.
423 */
424 if (time_after(req->start_time, next->start_time))
425 req->start_time = next->start_time;
426
427 req->biotail->bi_next = next->bio;
428 req->biotail = next->biotail;
429
430 req->__data_len += blk_rq_bytes(next);
431
432 elv_merge_requests(q, req, next);
433
434 /*
435 * 'next' is going away, so update stats accordingly
436 */
437 blk_account_io_merge(next);
438
439 req->ioprio = ioprio_best(req->ioprio, next->ioprio);
440 if (blk_rq_cpu_valid(next))
441 req->cpu = next->cpu;
442
443 /* owner-ship of bio passed from next to req */
444 next->bio = NULL;
445 __blk_put_request(q, next);
446 return 1;
447}
448
449int attempt_back_merge(struct request_queue *q, struct request *rq)
450{
451 struct request *next = elv_latter_request(q, rq);
452
453 if (next)
454 return attempt_merge(q, rq, next);
455
456 return 0;
457}
458
459int attempt_front_merge(struct request_queue *q, struct request *rq)
460{
461 struct request *prev = elv_former_request(q, rq);
462
463 if (prev)
464 return attempt_merge(q, prev, rq);
465
466 return 0;
467}
468
469int blk_attempt_req_merge(struct request_queue *q, struct request *rq,
470 struct request *next)
471{
472 return attempt_merge(q, rq, next);
473}
474
475bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
476{
477 if (!rq_mergeable(rq))
478 return false;
479
480 /* don't merge file system requests and discard requests */
481 if ((bio->bi_rw & REQ_DISCARD) != (rq->bio->bi_rw & REQ_DISCARD))
482 return false;
483
484 /* don't merge discard requests and secure discard requests */
485 if ((bio->bi_rw & REQ_SECURE) != (rq->bio->bi_rw & REQ_SECURE))
486 return false;
487
488 /* different data direction or already started, don't merge */
489 if (bio_data_dir(bio) != rq_data_dir(rq))
490 return false;
491
492 /* must be same device and not a special request */
493 if (rq->rq_disk != bio->bi_bdev->bd_disk || rq->special)
494 return false;
495
496 /* only merge integrity protected bio into ditto rq */
497 if (bio_integrity(bio) != blk_integrity_rq(rq))
498 return false;
499
500 return true;
501}
502
503int blk_try_merge(struct request *rq, struct bio *bio)
504{
505 if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_sector)
506 return ELEVATOR_BACK_MERGE;
507 else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_sector)
508 return ELEVATOR_FRONT_MERGE;
509 return ELEVATOR_NO_MERGE;
510}
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Functions related to segment and merge handling
4 */
5#include <linux/kernel.h>
6#include <linux/module.h>
7#include <linux/bio.h>
8#include <linux/blkdev.h>
9#include <linux/blk-integrity.h>
10#include <linux/scatterlist.h>
11#include <linux/part_stat.h>
12#include <linux/blk-cgroup.h>
13
14#include <trace/events/block.h>
15
16#include "blk.h"
17#include "blk-mq-sched.h"
18#include "blk-rq-qos.h"
19#include "blk-throttle.h"
20
21static inline void bio_get_first_bvec(struct bio *bio, struct bio_vec *bv)
22{
23 *bv = mp_bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter);
24}
25
26static inline void bio_get_last_bvec(struct bio *bio, struct bio_vec *bv)
27{
28 struct bvec_iter iter = bio->bi_iter;
29 int idx;
30
31 bio_get_first_bvec(bio, bv);
32 if (bv->bv_len == bio->bi_iter.bi_size)
33 return; /* this bio only has a single bvec */
34
35 bio_advance_iter(bio, &iter, iter.bi_size);
36
37 if (!iter.bi_bvec_done)
38 idx = iter.bi_idx - 1;
39 else /* in the middle of bvec */
40 idx = iter.bi_idx;
41
42 *bv = bio->bi_io_vec[idx];
43
44 /*
45 * iter.bi_bvec_done records actual length of the last bvec
46 * if this bio ends in the middle of one io vector
47 */
48 if (iter.bi_bvec_done)
49 bv->bv_len = iter.bi_bvec_done;
50}
51
52static inline bool bio_will_gap(struct request_queue *q,
53 struct request *prev_rq, struct bio *prev, struct bio *next)
54{
55 struct bio_vec pb, nb;
56
57 if (!bio_has_data(prev) || !queue_virt_boundary(q))
58 return false;
59
60 /*
61 * Don't merge if the 1st bio starts with non-zero offset, otherwise it
62 * is quite difficult to respect the sg gap limit. We work hard to
63 * merge a huge number of small single bios in case of mkfs.
64 */
65 if (prev_rq)
66 bio_get_first_bvec(prev_rq->bio, &pb);
67 else
68 bio_get_first_bvec(prev, &pb);
69 if (pb.bv_offset & queue_virt_boundary(q))
70 return true;
71
72 /*
73 * We don't need to worry about the situation that the merged segment
74 * ends in unaligned virt boundary:
75 *
76 * - if 'pb' ends aligned, the merged segment ends aligned
77 * - if 'pb' ends unaligned, the next bio must include
78 * one single bvec of 'nb', otherwise the 'nb' can't
79 * merge with 'pb'
80 */
81 bio_get_last_bvec(prev, &pb);
82 bio_get_first_bvec(next, &nb);
83 if (biovec_phys_mergeable(q, &pb, &nb))
84 return false;
85 return __bvec_gap_to_prev(&q->limits, &pb, nb.bv_offset);
86}
87
88static inline bool req_gap_back_merge(struct request *req, struct bio *bio)
89{
90 return bio_will_gap(req->q, req, req->biotail, bio);
91}
92
93static inline bool req_gap_front_merge(struct request *req, struct bio *bio)
94{
95 return bio_will_gap(req->q, NULL, bio, req->bio);
96}
97
98/*
99 * The max size one bio can handle is UINT_MAX becasue bvec_iter.bi_size
100 * is defined as 'unsigned int', meantime it has to be aligned to with the
101 * logical block size, which is the minimum accepted unit by hardware.
102 */
103static unsigned int bio_allowed_max_sectors(const struct queue_limits *lim)
104{
105 return round_down(UINT_MAX, lim->logical_block_size) >> SECTOR_SHIFT;
106}
107
108static struct bio *bio_split_discard(struct bio *bio,
109 const struct queue_limits *lim,
110 unsigned *nsegs, struct bio_set *bs)
111{
112 unsigned int max_discard_sectors, granularity;
113 sector_t tmp;
114 unsigned split_sectors;
115
116 *nsegs = 1;
117
118 granularity = max(lim->discard_granularity >> 9, 1U);
119
120 max_discard_sectors =
121 min(lim->max_discard_sectors, bio_allowed_max_sectors(lim));
122 max_discard_sectors -= max_discard_sectors % granularity;
123 if (unlikely(!max_discard_sectors))
124 return NULL;
125
126 if (bio_sectors(bio) <= max_discard_sectors)
127 return NULL;
128
129 split_sectors = max_discard_sectors;
130
131 /*
132 * If the next starting sector would be misaligned, stop the discard at
133 * the previous aligned sector.
134 */
135 tmp = bio->bi_iter.bi_sector + split_sectors -
136 ((lim->discard_alignment >> 9) % granularity);
137 tmp = sector_div(tmp, granularity);
138
139 if (split_sectors > tmp)
140 split_sectors -= tmp;
141
142 return bio_split(bio, split_sectors, GFP_NOIO, bs);
143}
144
145static struct bio *bio_split_write_zeroes(struct bio *bio,
146 const struct queue_limits *lim,
147 unsigned *nsegs, struct bio_set *bs)
148{
149 *nsegs = 0;
150 if (!lim->max_write_zeroes_sectors)
151 return NULL;
152 if (bio_sectors(bio) <= lim->max_write_zeroes_sectors)
153 return NULL;
154 return bio_split(bio, lim->max_write_zeroes_sectors, GFP_NOIO, bs);
155}
156
157/*
158 * Return the maximum number of sectors from the start of a bio that may be
159 * submitted as a single request to a block device. If enough sectors remain,
160 * align the end to the physical block size. Otherwise align the end to the
161 * logical block size. This approach minimizes the number of non-aligned
162 * requests that are submitted to a block device if the start of a bio is not
163 * aligned to a physical block boundary.
164 */
165static inline unsigned get_max_io_size(struct bio *bio,
166 const struct queue_limits *lim)
167{
168 unsigned pbs = lim->physical_block_size >> SECTOR_SHIFT;
169 unsigned lbs = lim->logical_block_size >> SECTOR_SHIFT;
170 unsigned max_sectors = lim->max_sectors, start, end;
171
172 if (lim->chunk_sectors) {
173 max_sectors = min(max_sectors,
174 blk_chunk_sectors_left(bio->bi_iter.bi_sector,
175 lim->chunk_sectors));
176 }
177
178 start = bio->bi_iter.bi_sector & (pbs - 1);
179 end = (start + max_sectors) & ~(pbs - 1);
180 if (end > start)
181 return end - start;
182 return max_sectors & ~(lbs - 1);
183}
184
185/**
186 * get_max_segment_size() - maximum number of bytes to add as a single segment
187 * @lim: Request queue limits.
188 * @start_page: See below.
189 * @offset: Offset from @start_page where to add a segment.
190 *
191 * Returns the maximum number of bytes that can be added as a single segment.
192 */
193static inline unsigned get_max_segment_size(const struct queue_limits *lim,
194 struct page *start_page, unsigned long offset)
195{
196 unsigned long mask = lim->seg_boundary_mask;
197
198 offset = mask & (page_to_phys(start_page) + offset);
199
200 /*
201 * Prevent an overflow if mask = ULONG_MAX and offset = 0 by adding 1
202 * after having calculated the minimum.
203 */
204 return min(mask - offset, (unsigned long)lim->max_segment_size - 1) + 1;
205}
206
207/**
208 * bvec_split_segs - verify whether or not a bvec should be split in the middle
209 * @lim: [in] queue limits to split based on
210 * @bv: [in] bvec to examine
211 * @nsegs: [in,out] Number of segments in the bio being built. Incremented
212 * by the number of segments from @bv that may be appended to that
213 * bio without exceeding @max_segs
214 * @bytes: [in,out] Number of bytes in the bio being built. Incremented
215 * by the number of bytes from @bv that may be appended to that
216 * bio without exceeding @max_bytes
217 * @max_segs: [in] upper bound for *@nsegs
218 * @max_bytes: [in] upper bound for *@bytes
219 *
220 * When splitting a bio, it can happen that a bvec is encountered that is too
221 * big to fit in a single segment and hence that it has to be split in the
222 * middle. This function verifies whether or not that should happen. The value
223 * %true is returned if and only if appending the entire @bv to a bio with
224 * *@nsegs segments and *@sectors sectors would make that bio unacceptable for
225 * the block driver.
226 */
227static bool bvec_split_segs(const struct queue_limits *lim,
228 const struct bio_vec *bv, unsigned *nsegs, unsigned *bytes,
229 unsigned max_segs, unsigned max_bytes)
230{
231 unsigned max_len = min(max_bytes, UINT_MAX) - *bytes;
232 unsigned len = min(bv->bv_len, max_len);
233 unsigned total_len = 0;
234 unsigned seg_size = 0;
235
236 while (len && *nsegs < max_segs) {
237 seg_size = get_max_segment_size(lim, bv->bv_page,
238 bv->bv_offset + total_len);
239 seg_size = min(seg_size, len);
240
241 (*nsegs)++;
242 total_len += seg_size;
243 len -= seg_size;
244
245 if ((bv->bv_offset + total_len) & lim->virt_boundary_mask)
246 break;
247 }
248
249 *bytes += total_len;
250
251 /* tell the caller to split the bvec if it is too big to fit */
252 return len > 0 || bv->bv_len > max_len;
253}
254
255/**
256 * bio_split_rw - split a bio in two bios
257 * @bio: [in] bio to be split
258 * @lim: [in] queue limits to split based on
259 * @segs: [out] number of segments in the bio with the first half of the sectors
260 * @bs: [in] bio set to allocate the clone from
261 * @max_bytes: [in] maximum number of bytes per bio
262 *
263 * Clone @bio, update the bi_iter of the clone to represent the first sectors
264 * of @bio and update @bio->bi_iter to represent the remaining sectors. The
265 * following is guaranteed for the cloned bio:
266 * - That it has at most @max_bytes worth of data
267 * - That it has at most queue_max_segments(@q) segments.
268 *
269 * Except for discard requests the cloned bio will point at the bi_io_vec of
270 * the original bio. It is the responsibility of the caller to ensure that the
271 * original bio is not freed before the cloned bio. The caller is also
272 * responsible for ensuring that @bs is only destroyed after processing of the
273 * split bio has finished.
274 */
275struct bio *bio_split_rw(struct bio *bio, const struct queue_limits *lim,
276 unsigned *segs, struct bio_set *bs, unsigned max_bytes)
277{
278 struct bio_vec bv, bvprv, *bvprvp = NULL;
279 struct bvec_iter iter;
280 unsigned nsegs = 0, bytes = 0;
281
282 bio_for_each_bvec(bv, bio, iter) {
283 /*
284 * If the queue doesn't support SG gaps and adding this
285 * offset would create a gap, disallow it.
286 */
287 if (bvprvp && bvec_gap_to_prev(lim, bvprvp, bv.bv_offset))
288 goto split;
289
290 if (nsegs < lim->max_segments &&
291 bytes + bv.bv_len <= max_bytes &&
292 bv.bv_offset + bv.bv_len <= PAGE_SIZE) {
293 nsegs++;
294 bytes += bv.bv_len;
295 } else {
296 if (bvec_split_segs(lim, &bv, &nsegs, &bytes,
297 lim->max_segments, max_bytes))
298 goto split;
299 }
300
301 bvprv = bv;
302 bvprvp = &bvprv;
303 }
304
305 *segs = nsegs;
306 return NULL;
307split:
308 /*
309 * We can't sanely support splitting for a REQ_NOWAIT bio. End it
310 * with EAGAIN if splitting is required and return an error pointer.
311 */
312 if (bio->bi_opf & REQ_NOWAIT) {
313 bio->bi_status = BLK_STS_AGAIN;
314 bio_endio(bio);
315 return ERR_PTR(-EAGAIN);
316 }
317
318 *segs = nsegs;
319
320 /*
321 * Individual bvecs might not be logical block aligned. Round down the
322 * split size so that each bio is properly block size aligned, even if
323 * we do not use the full hardware limits.
324 */
325 bytes = ALIGN_DOWN(bytes, lim->logical_block_size);
326
327 /*
328 * Bio splitting may cause subtle trouble such as hang when doing sync
329 * iopoll in direct IO routine. Given performance gain of iopoll for
330 * big IO can be trival, disable iopoll when split needed.
331 */
332 bio_clear_polled(bio);
333 return bio_split(bio, bytes >> SECTOR_SHIFT, GFP_NOIO, bs);
334}
335EXPORT_SYMBOL_GPL(bio_split_rw);
336
337/**
338 * __bio_split_to_limits - split a bio to fit the queue limits
339 * @bio: bio to be split
340 * @lim: queue limits to split based on
341 * @nr_segs: returns the number of segments in the returned bio
342 *
343 * Check if @bio needs splitting based on the queue limits, and if so split off
344 * a bio fitting the limits from the beginning of @bio and return it. @bio is
345 * shortened to the remainder and re-submitted.
346 *
347 * The split bio is allocated from @q->bio_split, which is provided by the
348 * block layer.
349 */
350struct bio *__bio_split_to_limits(struct bio *bio,
351 const struct queue_limits *lim,
352 unsigned int *nr_segs)
353{
354 struct bio_set *bs = &bio->bi_bdev->bd_disk->bio_split;
355 struct bio *split;
356
357 switch (bio_op(bio)) {
358 case REQ_OP_DISCARD:
359 case REQ_OP_SECURE_ERASE:
360 split = bio_split_discard(bio, lim, nr_segs, bs);
361 break;
362 case REQ_OP_WRITE_ZEROES:
363 split = bio_split_write_zeroes(bio, lim, nr_segs, bs);
364 break;
365 default:
366 split = bio_split_rw(bio, lim, nr_segs, bs,
367 get_max_io_size(bio, lim) << SECTOR_SHIFT);
368 if (IS_ERR(split))
369 return NULL;
370 break;
371 }
372
373 if (split) {
374 /* there isn't chance to merge the split bio */
375 split->bi_opf |= REQ_NOMERGE;
376
377 blkcg_bio_issue_init(split);
378 bio_chain(split, bio);
379 trace_block_split(split, bio->bi_iter.bi_sector);
380 submit_bio_noacct(bio);
381 return split;
382 }
383 return bio;
384}
385
386/**
387 * bio_split_to_limits - split a bio to fit the queue limits
388 * @bio: bio to be split
389 *
390 * Check if @bio needs splitting based on the queue limits of @bio->bi_bdev, and
391 * if so split off a bio fitting the limits from the beginning of @bio and
392 * return it. @bio is shortened to the remainder and re-submitted.
393 *
394 * The split bio is allocated from @q->bio_split, which is provided by the
395 * block layer.
396 */
397struct bio *bio_split_to_limits(struct bio *bio)
398{
399 const struct queue_limits *lim = &bdev_get_queue(bio->bi_bdev)->limits;
400 unsigned int nr_segs;
401
402 if (bio_may_exceed_limits(bio, lim))
403 return __bio_split_to_limits(bio, lim, &nr_segs);
404 return bio;
405}
406EXPORT_SYMBOL(bio_split_to_limits);
407
408unsigned int blk_recalc_rq_segments(struct request *rq)
409{
410 unsigned int nr_phys_segs = 0;
411 unsigned int bytes = 0;
412 struct req_iterator iter;
413 struct bio_vec bv;
414
415 if (!rq->bio)
416 return 0;
417
418 switch (bio_op(rq->bio)) {
419 case REQ_OP_DISCARD:
420 case REQ_OP_SECURE_ERASE:
421 if (queue_max_discard_segments(rq->q) > 1) {
422 struct bio *bio = rq->bio;
423
424 for_each_bio(bio)
425 nr_phys_segs++;
426 return nr_phys_segs;
427 }
428 return 1;
429 case REQ_OP_WRITE_ZEROES:
430 return 0;
431 default:
432 break;
433 }
434
435 rq_for_each_bvec(bv, rq, iter)
436 bvec_split_segs(&rq->q->limits, &bv, &nr_phys_segs, &bytes,
437 UINT_MAX, UINT_MAX);
438 return nr_phys_segs;
439}
440
441static inline struct scatterlist *blk_next_sg(struct scatterlist **sg,
442 struct scatterlist *sglist)
443{
444 if (!*sg)
445 return sglist;
446
447 /*
448 * If the driver previously mapped a shorter list, we could see a
449 * termination bit prematurely unless it fully inits the sg table
450 * on each mapping. We KNOW that there must be more entries here
451 * or the driver would be buggy, so force clear the termination bit
452 * to avoid doing a full sg_init_table() in drivers for each command.
453 */
454 sg_unmark_end(*sg);
455 return sg_next(*sg);
456}
457
458static unsigned blk_bvec_map_sg(struct request_queue *q,
459 struct bio_vec *bvec, struct scatterlist *sglist,
460 struct scatterlist **sg)
461{
462 unsigned nbytes = bvec->bv_len;
463 unsigned nsegs = 0, total = 0;
464
465 while (nbytes > 0) {
466 unsigned offset = bvec->bv_offset + total;
467 unsigned len = min(get_max_segment_size(&q->limits,
468 bvec->bv_page, offset), nbytes);
469 struct page *page = bvec->bv_page;
470
471 /*
472 * Unfortunately a fair number of drivers barf on scatterlists
473 * that have an offset larger than PAGE_SIZE, despite other
474 * subsystems dealing with that invariant just fine. For now
475 * stick to the legacy format where we never present those from
476 * the block layer, but the code below should be removed once
477 * these offenders (mostly MMC/SD drivers) are fixed.
478 */
479 page += (offset >> PAGE_SHIFT);
480 offset &= ~PAGE_MASK;
481
482 *sg = blk_next_sg(sg, sglist);
483 sg_set_page(*sg, page, len, offset);
484
485 total += len;
486 nbytes -= len;
487 nsegs++;
488 }
489
490 return nsegs;
491}
492
493static inline int __blk_bvec_map_sg(struct bio_vec bv,
494 struct scatterlist *sglist, struct scatterlist **sg)
495{
496 *sg = blk_next_sg(sg, sglist);
497 sg_set_page(*sg, bv.bv_page, bv.bv_len, bv.bv_offset);
498 return 1;
499}
500
501/* only try to merge bvecs into one sg if they are from two bios */
502static inline bool
503__blk_segment_map_sg_merge(struct request_queue *q, struct bio_vec *bvec,
504 struct bio_vec *bvprv, struct scatterlist **sg)
505{
506
507 int nbytes = bvec->bv_len;
508
509 if (!*sg)
510 return false;
511
512 if ((*sg)->length + nbytes > queue_max_segment_size(q))
513 return false;
514
515 if (!biovec_phys_mergeable(q, bvprv, bvec))
516 return false;
517
518 (*sg)->length += nbytes;
519
520 return true;
521}
522
523static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio,
524 struct scatterlist *sglist,
525 struct scatterlist **sg)
526{
527 struct bio_vec bvec, bvprv = { NULL };
528 struct bvec_iter iter;
529 int nsegs = 0;
530 bool new_bio = false;
531
532 for_each_bio(bio) {
533 bio_for_each_bvec(bvec, bio, iter) {
534 /*
535 * Only try to merge bvecs from two bios given we
536 * have done bio internal merge when adding pages
537 * to bio
538 */
539 if (new_bio &&
540 __blk_segment_map_sg_merge(q, &bvec, &bvprv, sg))
541 goto next_bvec;
542
543 if (bvec.bv_offset + bvec.bv_len <= PAGE_SIZE)
544 nsegs += __blk_bvec_map_sg(bvec, sglist, sg);
545 else
546 nsegs += blk_bvec_map_sg(q, &bvec, sglist, sg);
547 next_bvec:
548 new_bio = false;
549 }
550 if (likely(bio->bi_iter.bi_size)) {
551 bvprv = bvec;
552 new_bio = true;
553 }
554 }
555
556 return nsegs;
557}
558
559/*
560 * map a request to scatterlist, return number of sg entries setup. Caller
561 * must make sure sg can hold rq->nr_phys_segments entries
562 */
563int __blk_rq_map_sg(struct request_queue *q, struct request *rq,
564 struct scatterlist *sglist, struct scatterlist **last_sg)
565{
566 int nsegs = 0;
567
568 if (rq->rq_flags & RQF_SPECIAL_PAYLOAD)
569 nsegs = __blk_bvec_map_sg(rq->special_vec, sglist, last_sg);
570 else if (rq->bio)
571 nsegs = __blk_bios_map_sg(q, rq->bio, sglist, last_sg);
572
573 if (*last_sg)
574 sg_mark_end(*last_sg);
575
576 /*
577 * Something must have been wrong if the figured number of
578 * segment is bigger than number of req's physical segments
579 */
580 WARN_ON(nsegs > blk_rq_nr_phys_segments(rq));
581
582 return nsegs;
583}
584EXPORT_SYMBOL(__blk_rq_map_sg);
585
586static inline unsigned int blk_rq_get_max_sectors(struct request *rq,
587 sector_t offset)
588{
589 struct request_queue *q = rq->q;
590 unsigned int max_sectors;
591
592 if (blk_rq_is_passthrough(rq))
593 return q->limits.max_hw_sectors;
594
595 max_sectors = blk_queue_get_max_sectors(q, req_op(rq));
596 if (!q->limits.chunk_sectors ||
597 req_op(rq) == REQ_OP_DISCARD ||
598 req_op(rq) == REQ_OP_SECURE_ERASE)
599 return max_sectors;
600 return min(max_sectors,
601 blk_chunk_sectors_left(offset, q->limits.chunk_sectors));
602}
603
604static inline int ll_new_hw_segment(struct request *req, struct bio *bio,
605 unsigned int nr_phys_segs)
606{
607 if (!blk_cgroup_mergeable(req, bio))
608 goto no_merge;
609
610 if (blk_integrity_merge_bio(req->q, req, bio) == false)
611 goto no_merge;
612
613 /* discard request merge won't add new segment */
614 if (req_op(req) == REQ_OP_DISCARD)
615 return 1;
616
617 if (req->nr_phys_segments + nr_phys_segs > blk_rq_get_max_segments(req))
618 goto no_merge;
619
620 /*
621 * This will form the start of a new hw segment. Bump both
622 * counters.
623 */
624 req->nr_phys_segments += nr_phys_segs;
625 return 1;
626
627no_merge:
628 req_set_nomerge(req->q, req);
629 return 0;
630}
631
632int ll_back_merge_fn(struct request *req, struct bio *bio, unsigned int nr_segs)
633{
634 if (req_gap_back_merge(req, bio))
635 return 0;
636 if (blk_integrity_rq(req) &&
637 integrity_req_gap_back_merge(req, bio))
638 return 0;
639 if (!bio_crypt_ctx_back_mergeable(req, bio))
640 return 0;
641 if (blk_rq_sectors(req) + bio_sectors(bio) >
642 blk_rq_get_max_sectors(req, blk_rq_pos(req))) {
643 req_set_nomerge(req->q, req);
644 return 0;
645 }
646
647 return ll_new_hw_segment(req, bio, nr_segs);
648}
649
650static int ll_front_merge_fn(struct request *req, struct bio *bio,
651 unsigned int nr_segs)
652{
653 if (req_gap_front_merge(req, bio))
654 return 0;
655 if (blk_integrity_rq(req) &&
656 integrity_req_gap_front_merge(req, bio))
657 return 0;
658 if (!bio_crypt_ctx_front_mergeable(req, bio))
659 return 0;
660 if (blk_rq_sectors(req) + bio_sectors(bio) >
661 blk_rq_get_max_sectors(req, bio->bi_iter.bi_sector)) {
662 req_set_nomerge(req->q, req);
663 return 0;
664 }
665
666 return ll_new_hw_segment(req, bio, nr_segs);
667}
668
669static bool req_attempt_discard_merge(struct request_queue *q, struct request *req,
670 struct request *next)
671{
672 unsigned short segments = blk_rq_nr_discard_segments(req);
673
674 if (segments >= queue_max_discard_segments(q))
675 goto no_merge;
676 if (blk_rq_sectors(req) + bio_sectors(next->bio) >
677 blk_rq_get_max_sectors(req, blk_rq_pos(req)))
678 goto no_merge;
679
680 req->nr_phys_segments = segments + blk_rq_nr_discard_segments(next);
681 return true;
682no_merge:
683 req_set_nomerge(q, req);
684 return false;
685}
686
687static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
688 struct request *next)
689{
690 int total_phys_segments;
691
692 if (req_gap_back_merge(req, next->bio))
693 return 0;
694
695 /*
696 * Will it become too large?
697 */
698 if ((blk_rq_sectors(req) + blk_rq_sectors(next)) >
699 blk_rq_get_max_sectors(req, blk_rq_pos(req)))
700 return 0;
701
702 total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
703 if (total_phys_segments > blk_rq_get_max_segments(req))
704 return 0;
705
706 if (!blk_cgroup_mergeable(req, next->bio))
707 return 0;
708
709 if (blk_integrity_merge_rq(q, req, next) == false)
710 return 0;
711
712 if (!bio_crypt_ctx_merge_rq(req, next))
713 return 0;
714
715 /* Merge is OK... */
716 req->nr_phys_segments = total_phys_segments;
717 return 1;
718}
719
720/**
721 * blk_rq_set_mixed_merge - mark a request as mixed merge
722 * @rq: request to mark as mixed merge
723 *
724 * Description:
725 * @rq is about to be mixed merged. Make sure the attributes
726 * which can be mixed are set in each bio and mark @rq as mixed
727 * merged.
728 */
729void blk_rq_set_mixed_merge(struct request *rq)
730{
731 blk_opf_t ff = rq->cmd_flags & REQ_FAILFAST_MASK;
732 struct bio *bio;
733
734 if (rq->rq_flags & RQF_MIXED_MERGE)
735 return;
736
737 /*
738 * @rq will no longer represent mixable attributes for all the
739 * contained bios. It will just track those of the first one.
740 * Distributes the attributs to each bio.
741 */
742 for (bio = rq->bio; bio; bio = bio->bi_next) {
743 WARN_ON_ONCE((bio->bi_opf & REQ_FAILFAST_MASK) &&
744 (bio->bi_opf & REQ_FAILFAST_MASK) != ff);
745 bio->bi_opf |= ff;
746 }
747 rq->rq_flags |= RQF_MIXED_MERGE;
748}
749
750static inline blk_opf_t bio_failfast(const struct bio *bio)
751{
752 if (bio->bi_opf & REQ_RAHEAD)
753 return REQ_FAILFAST_MASK;
754
755 return bio->bi_opf & REQ_FAILFAST_MASK;
756}
757
758/*
759 * After we are marked as MIXED_MERGE, any new RA bio has to be updated
760 * as failfast, and request's failfast has to be updated in case of
761 * front merge.
762 */
763static inline void blk_update_mixed_merge(struct request *req,
764 struct bio *bio, bool front_merge)
765{
766 if (req->rq_flags & RQF_MIXED_MERGE) {
767 if (bio->bi_opf & REQ_RAHEAD)
768 bio->bi_opf |= REQ_FAILFAST_MASK;
769
770 if (front_merge) {
771 req->cmd_flags &= ~REQ_FAILFAST_MASK;
772 req->cmd_flags |= bio->bi_opf & REQ_FAILFAST_MASK;
773 }
774 }
775}
776
777static void blk_account_io_merge_request(struct request *req)
778{
779 if (blk_do_io_stat(req)) {
780 part_stat_lock();
781 part_stat_inc(req->part, merges[op_stat_group(req_op(req))]);
782 part_stat_unlock();
783 }
784}
785
786static enum elv_merge blk_try_req_merge(struct request *req,
787 struct request *next)
788{
789 if (blk_discard_mergable(req))
790 return ELEVATOR_DISCARD_MERGE;
791 else if (blk_rq_pos(req) + blk_rq_sectors(req) == blk_rq_pos(next))
792 return ELEVATOR_BACK_MERGE;
793
794 return ELEVATOR_NO_MERGE;
795}
796
797/*
798 * For non-mq, this has to be called with the request spinlock acquired.
799 * For mq with scheduling, the appropriate queue wide lock should be held.
800 */
801static struct request *attempt_merge(struct request_queue *q,
802 struct request *req, struct request *next)
803{
804 if (!rq_mergeable(req) || !rq_mergeable(next))
805 return NULL;
806
807 if (req_op(req) != req_op(next))
808 return NULL;
809
810 if (rq_data_dir(req) != rq_data_dir(next))
811 return NULL;
812
813 if (req->ioprio != next->ioprio)
814 return NULL;
815
816 /*
817 * If we are allowed to merge, then append bio list
818 * from next to rq and release next. merge_requests_fn
819 * will have updated segment counts, update sector
820 * counts here. Handle DISCARDs separately, as they
821 * have separate settings.
822 */
823
824 switch (blk_try_req_merge(req, next)) {
825 case ELEVATOR_DISCARD_MERGE:
826 if (!req_attempt_discard_merge(q, req, next))
827 return NULL;
828 break;
829 case ELEVATOR_BACK_MERGE:
830 if (!ll_merge_requests_fn(q, req, next))
831 return NULL;
832 break;
833 default:
834 return NULL;
835 }
836
837 /*
838 * If failfast settings disagree or any of the two is already
839 * a mixed merge, mark both as mixed before proceeding. This
840 * makes sure that all involved bios have mixable attributes
841 * set properly.
842 */
843 if (((req->rq_flags | next->rq_flags) & RQF_MIXED_MERGE) ||
844 (req->cmd_flags & REQ_FAILFAST_MASK) !=
845 (next->cmd_flags & REQ_FAILFAST_MASK)) {
846 blk_rq_set_mixed_merge(req);
847 blk_rq_set_mixed_merge(next);
848 }
849
850 /*
851 * At this point we have either done a back merge or front merge. We
852 * need the smaller start_time_ns of the merged requests to be the
853 * current request for accounting purposes.
854 */
855 if (next->start_time_ns < req->start_time_ns)
856 req->start_time_ns = next->start_time_ns;
857
858 req->biotail->bi_next = next->bio;
859 req->biotail = next->biotail;
860
861 req->__data_len += blk_rq_bytes(next);
862
863 if (!blk_discard_mergable(req))
864 elv_merge_requests(q, req, next);
865
866 blk_crypto_rq_put_keyslot(next);
867
868 /*
869 * 'next' is going away, so update stats accordingly
870 */
871 blk_account_io_merge_request(next);
872
873 trace_block_rq_merge(next);
874
875 /*
876 * ownership of bio passed from next to req, return 'next' for
877 * the caller to free
878 */
879 next->bio = NULL;
880 return next;
881}
882
883static struct request *attempt_back_merge(struct request_queue *q,
884 struct request *rq)
885{
886 struct request *next = elv_latter_request(q, rq);
887
888 if (next)
889 return attempt_merge(q, rq, next);
890
891 return NULL;
892}
893
894static struct request *attempt_front_merge(struct request_queue *q,
895 struct request *rq)
896{
897 struct request *prev = elv_former_request(q, rq);
898
899 if (prev)
900 return attempt_merge(q, prev, rq);
901
902 return NULL;
903}
904
905/*
906 * Try to merge 'next' into 'rq'. Return true if the merge happened, false
907 * otherwise. The caller is responsible for freeing 'next' if the merge
908 * happened.
909 */
910bool blk_attempt_req_merge(struct request_queue *q, struct request *rq,
911 struct request *next)
912{
913 return attempt_merge(q, rq, next);
914}
915
916bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
917{
918 if (!rq_mergeable(rq) || !bio_mergeable(bio))
919 return false;
920
921 if (req_op(rq) != bio_op(bio))
922 return false;
923
924 /* different data direction or already started, don't merge */
925 if (bio_data_dir(bio) != rq_data_dir(rq))
926 return false;
927
928 /* don't merge across cgroup boundaries */
929 if (!blk_cgroup_mergeable(rq, bio))
930 return false;
931
932 /* only merge integrity protected bio into ditto rq */
933 if (blk_integrity_merge_bio(rq->q, rq, bio) == false)
934 return false;
935
936 /* Only merge if the crypt contexts are compatible */
937 if (!bio_crypt_rq_ctx_compatible(rq, bio))
938 return false;
939
940 if (rq->ioprio != bio_prio(bio))
941 return false;
942
943 return true;
944}
945
946enum elv_merge blk_try_merge(struct request *rq, struct bio *bio)
947{
948 if (blk_discard_mergable(rq))
949 return ELEVATOR_DISCARD_MERGE;
950 else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector)
951 return ELEVATOR_BACK_MERGE;
952 else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector)
953 return ELEVATOR_FRONT_MERGE;
954 return ELEVATOR_NO_MERGE;
955}
956
957static void blk_account_io_merge_bio(struct request *req)
958{
959 if (!blk_do_io_stat(req))
960 return;
961
962 part_stat_lock();
963 part_stat_inc(req->part, merges[op_stat_group(req_op(req))]);
964 part_stat_unlock();
965}
966
967enum bio_merge_status {
968 BIO_MERGE_OK,
969 BIO_MERGE_NONE,
970 BIO_MERGE_FAILED,
971};
972
973static enum bio_merge_status bio_attempt_back_merge(struct request *req,
974 struct bio *bio, unsigned int nr_segs)
975{
976 const blk_opf_t ff = bio_failfast(bio);
977
978 if (!ll_back_merge_fn(req, bio, nr_segs))
979 return BIO_MERGE_FAILED;
980
981 trace_block_bio_backmerge(bio);
982 rq_qos_merge(req->q, req, bio);
983
984 if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
985 blk_rq_set_mixed_merge(req);
986
987 blk_update_mixed_merge(req, bio, false);
988
989 req->biotail->bi_next = bio;
990 req->biotail = bio;
991 req->__data_len += bio->bi_iter.bi_size;
992
993 bio_crypt_free_ctx(bio);
994
995 blk_account_io_merge_bio(req);
996 return BIO_MERGE_OK;
997}
998
999static enum bio_merge_status bio_attempt_front_merge(struct request *req,
1000 struct bio *bio, unsigned int nr_segs)
1001{
1002 const blk_opf_t ff = bio_failfast(bio);
1003
1004 if (!ll_front_merge_fn(req, bio, nr_segs))
1005 return BIO_MERGE_FAILED;
1006
1007 trace_block_bio_frontmerge(bio);
1008 rq_qos_merge(req->q, req, bio);
1009
1010 if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
1011 blk_rq_set_mixed_merge(req);
1012
1013 blk_update_mixed_merge(req, bio, true);
1014
1015 bio->bi_next = req->bio;
1016 req->bio = bio;
1017
1018 req->__sector = bio->bi_iter.bi_sector;
1019 req->__data_len += bio->bi_iter.bi_size;
1020
1021 bio_crypt_do_front_merge(req, bio);
1022
1023 blk_account_io_merge_bio(req);
1024 return BIO_MERGE_OK;
1025}
1026
1027static enum bio_merge_status bio_attempt_discard_merge(struct request_queue *q,
1028 struct request *req, struct bio *bio)
1029{
1030 unsigned short segments = blk_rq_nr_discard_segments(req);
1031
1032 if (segments >= queue_max_discard_segments(q))
1033 goto no_merge;
1034 if (blk_rq_sectors(req) + bio_sectors(bio) >
1035 blk_rq_get_max_sectors(req, blk_rq_pos(req)))
1036 goto no_merge;
1037
1038 rq_qos_merge(q, req, bio);
1039
1040 req->biotail->bi_next = bio;
1041 req->biotail = bio;
1042 req->__data_len += bio->bi_iter.bi_size;
1043 req->nr_phys_segments = segments + 1;
1044
1045 blk_account_io_merge_bio(req);
1046 return BIO_MERGE_OK;
1047no_merge:
1048 req_set_nomerge(q, req);
1049 return BIO_MERGE_FAILED;
1050}
1051
1052static enum bio_merge_status blk_attempt_bio_merge(struct request_queue *q,
1053 struct request *rq,
1054 struct bio *bio,
1055 unsigned int nr_segs,
1056 bool sched_allow_merge)
1057{
1058 if (!blk_rq_merge_ok(rq, bio))
1059 return BIO_MERGE_NONE;
1060
1061 switch (blk_try_merge(rq, bio)) {
1062 case ELEVATOR_BACK_MERGE:
1063 if (!sched_allow_merge || blk_mq_sched_allow_merge(q, rq, bio))
1064 return bio_attempt_back_merge(rq, bio, nr_segs);
1065 break;
1066 case ELEVATOR_FRONT_MERGE:
1067 if (!sched_allow_merge || blk_mq_sched_allow_merge(q, rq, bio))
1068 return bio_attempt_front_merge(rq, bio, nr_segs);
1069 break;
1070 case ELEVATOR_DISCARD_MERGE:
1071 return bio_attempt_discard_merge(q, rq, bio);
1072 default:
1073 return BIO_MERGE_NONE;
1074 }
1075
1076 return BIO_MERGE_FAILED;
1077}
1078
1079/**
1080 * blk_attempt_plug_merge - try to merge with %current's plugged list
1081 * @q: request_queue new bio is being queued at
1082 * @bio: new bio being queued
1083 * @nr_segs: number of segments in @bio
1084 * from the passed in @q already in the plug list
1085 *
1086 * Determine whether @bio being queued on @q can be merged with the previous
1087 * request on %current's plugged list. Returns %true if merge was successful,
1088 * otherwise %false.
1089 *
1090 * Plugging coalesces IOs from the same issuer for the same purpose without
1091 * going through @q->queue_lock. As such it's more of an issuing mechanism
1092 * than scheduling, and the request, while may have elvpriv data, is not
1093 * added on the elevator at this point. In addition, we don't have
1094 * reliable access to the elevator outside queue lock. Only check basic
1095 * merging parameters without querying the elevator.
1096 *
1097 * Caller must ensure !blk_queue_nomerges(q) beforehand.
1098 */
1099bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
1100 unsigned int nr_segs)
1101{
1102 struct blk_plug *plug;
1103 struct request *rq;
1104
1105 plug = blk_mq_plug(bio);
1106 if (!plug || rq_list_empty(plug->mq_list))
1107 return false;
1108
1109 rq_list_for_each(&plug->mq_list, rq) {
1110 if (rq->q == q) {
1111 if (blk_attempt_bio_merge(q, rq, bio, nr_segs, false) ==
1112 BIO_MERGE_OK)
1113 return true;
1114 break;
1115 }
1116
1117 /*
1118 * Only keep iterating plug list for merges if we have multiple
1119 * queues
1120 */
1121 if (!plug->multiple_queues)
1122 break;
1123 }
1124 return false;
1125}
1126
1127/*
1128 * Iterate list of requests and see if we can merge this bio with any
1129 * of them.
1130 */
1131bool blk_bio_list_merge(struct request_queue *q, struct list_head *list,
1132 struct bio *bio, unsigned int nr_segs)
1133{
1134 struct request *rq;
1135 int checked = 8;
1136
1137 list_for_each_entry_reverse(rq, list, queuelist) {
1138 if (!checked--)
1139 break;
1140
1141 switch (blk_attempt_bio_merge(q, rq, bio, nr_segs, true)) {
1142 case BIO_MERGE_NONE:
1143 continue;
1144 case BIO_MERGE_OK:
1145 return true;
1146 case BIO_MERGE_FAILED:
1147 return false;
1148 }
1149
1150 }
1151
1152 return false;
1153}
1154EXPORT_SYMBOL_GPL(blk_bio_list_merge);
1155
1156bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
1157 unsigned int nr_segs, struct request **merged_request)
1158{
1159 struct request *rq;
1160
1161 switch (elv_merge(q, &rq, bio)) {
1162 case ELEVATOR_BACK_MERGE:
1163 if (!blk_mq_sched_allow_merge(q, rq, bio))
1164 return false;
1165 if (bio_attempt_back_merge(rq, bio, nr_segs) != BIO_MERGE_OK)
1166 return false;
1167 *merged_request = attempt_back_merge(q, rq);
1168 if (!*merged_request)
1169 elv_merged_request(q, rq, ELEVATOR_BACK_MERGE);
1170 return true;
1171 case ELEVATOR_FRONT_MERGE:
1172 if (!blk_mq_sched_allow_merge(q, rq, bio))
1173 return false;
1174 if (bio_attempt_front_merge(rq, bio, nr_segs) != BIO_MERGE_OK)
1175 return false;
1176 *merged_request = attempt_front_merge(q, rq);
1177 if (!*merged_request)
1178 elv_merged_request(q, rq, ELEVATOR_FRONT_MERGE);
1179 return true;
1180 case ELEVATOR_DISCARD_MERGE:
1181 return bio_attempt_discard_merge(q, rq, bio) == BIO_MERGE_OK;
1182 default:
1183 return false;
1184 }
1185}
1186EXPORT_SYMBOL_GPL(blk_mq_sched_try_merge);