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