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 | |
21 | static 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 | |
26 | static 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, bytes: 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 | |
52 | static 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(bio: 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(bio: prev_rq->bio, bv: &pb); |
67 | else |
68 | bio_get_first_bvec(bio: prev, bv: &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(bio: prev, bv: &pb); |
82 | bio_get_first_bvec(bio: next, bv: &nb); |
83 | if (biovec_phys_mergeable(q, vec1: &pb, vec2: &nb)) |
84 | return false; |
85 | return __bvec_gap_to_prev(lim: &q->limits, bprv: &pb, offset: nb.bv_offset); |
86 | } |
87 | |
88 | static inline bool req_gap_back_merge(struct request *req, struct bio *bio) |
89 | { |
90 | return bio_will_gap(q: req->q, prev_rq: req, prev: req->biotail, next: bio); |
91 | } |
92 | |
93 | static inline bool req_gap_front_merge(struct request *req, struct bio *bio) |
94 | { |
95 | return bio_will_gap(q: req->q, NULL, prev: bio, next: 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 | */ |
103 | static 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 | |
108 | static 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, sectors: split_sectors, GFP_NOIO, bs); |
143 | } |
144 | |
145 | static 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, sectors: 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 | */ |
165 | static 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 | */ |
193 | static 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 | */ |
227 | static 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, start_page: bv->bv_page, |
238 | offset: 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 | */ |
275 | struct 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, bprv: bvprvp, offset: 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: &bv, nsegs: &nsegs, bytes: &bytes, |
297 | max_segs: lim->max_segments, max_bytes)) |
298 | goto split; |
299 | } |
300 | |
301 | bvprv = bv; |
302 | bvprvp = &bvprv; |
303 | } |
304 | |
305 | *segs = nsegs; |
306 | return NULL; |
307 | split: |
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(error: -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, sectors: bytes >> SECTOR_SHIFT, GFP_NOIO, bs); |
334 | } |
335 | EXPORT_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 | */ |
350 | struct 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, nsegs: nr_segs, bs); |
361 | break; |
362 | case REQ_OP_WRITE_ZEROES: |
363 | split = bio_split_write_zeroes(bio, lim, nsegs: 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(ptr: 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(bio: split); |
378 | bio_chain(split, bio); |
379 | trace_block_split(bio: split, new_sector: 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 | */ |
397 | struct bio *bio_split_to_limits(struct bio *bio) |
398 | { |
399 | const struct queue_limits *lim = &bdev_get_queue(bdev: 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: &nr_segs); |
404 | return bio; |
405 | } |
406 | EXPORT_SYMBOL(bio_split_to_limits); |
407 | |
408 | unsigned 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(bio: rq->bio)) { |
419 | case REQ_OP_DISCARD: |
420 | case REQ_OP_SECURE_ERASE: |
421 | if (queue_max_discard_segments(q: 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(lim: &rq->q->limits, bv: &bv, nsegs: &nr_phys_segs, bytes: &bytes, |
437 | UINT_MAX, UINT_MAX); |
438 | return nr_phys_segs; |
439 | } |
440 | |
441 | static 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: *sg); |
455 | return sg_next(*sg); |
456 | } |
457 | |
458 | static 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: *sg, page, len, offset); |
484 | |
485 | total += len; |
486 | nbytes -= len; |
487 | nsegs++; |
488 | } |
489 | |
490 | return nsegs; |
491 | } |
492 | |
493 | static 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: *sg, page: bv.bv_page, len: bv.bv_len, offset: bv.bv_offset); |
498 | return 1; |
499 | } |
500 | |
501 | /* only try to merge bvecs into one sg if they are from two bios */ |
502 | static 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, vec1: bvprv, vec2: bvec)) |
516 | return false; |
517 | |
518 | (*sg)->length += nbytes; |
519 | |
520 | return true; |
521 | } |
522 | |
523 | static 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: &bvec, bvprv: &bvprv, sg)) |
541 | goto next_bvec; |
542 | |
543 | if (bvec.bv_offset + bvec.bv_len <= PAGE_SIZE) |
544 | nsegs += __blk_bvec_map_sg(bv: bvec, sglist, sg); |
545 | else |
546 | nsegs += blk_bvec_map_sg(q, bvec: &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 | */ |
563 | int __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(bv: rq->special_vec, sglist, sg: last_sg); |
570 | else if (rq->bio) |
571 | nsegs = __blk_bios_map_sg(q, bio: rq->bio, sglist, sg: last_sg); |
572 | |
573 | if (*last_sg) |
574 | sg_mark_end(sg: *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 | } |
584 | EXPORT_SYMBOL(__blk_rq_map_sg); |
585 | |
586 | static 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, op: req_op(req: rq)); |
596 | if (!q->limits.chunk_sectors || |
597 | req_op(req: rq) == REQ_OP_DISCARD || |
598 | req_op(req: 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 | |
604 | static inline int ll_new_hw_segment(struct request *req, struct bio *bio, |
605 | unsigned int nr_phys_segs) |
606 | { |
607 | if (!blk_cgroup_mergeable(rq: 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(rq: 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 | |
627 | no_merge: |
628 | req_set_nomerge(q: req->q, req); |
629 | return 0; |
630 | } |
631 | |
632 | int 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(rq: req) && |
637 | integrity_req_gap_back_merge(req, next: bio)) |
638 | return 0; |
639 | if (!bio_crypt_ctx_back_mergeable(req, bio)) |
640 | return 0; |
641 | if (blk_rq_sectors(rq: req) + bio_sectors(bio) > |
642 | blk_rq_get_max_sectors(rq: req, offset: blk_rq_pos(rq: req))) { |
643 | req_set_nomerge(q: req->q, req); |
644 | return 0; |
645 | } |
646 | |
647 | return ll_new_hw_segment(req, bio, nr_phys_segs: nr_segs); |
648 | } |
649 | |
650 | static 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(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(rq: req) + bio_sectors(bio) > |
661 | blk_rq_get_max_sectors(rq: req, offset: bio->bi_iter.bi_sector)) { |
662 | req_set_nomerge(q: req->q, req); |
663 | return 0; |
664 | } |
665 | |
666 | return ll_new_hw_segment(req, bio, nr_phys_segs: nr_segs); |
667 | } |
668 | |
669 | static 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(rq: req); |
673 | |
674 | if (segments >= queue_max_discard_segments(q)) |
675 | goto no_merge; |
676 | if (blk_rq_sectors(rq: req) + bio_sectors(next->bio) > |
677 | blk_rq_get_max_sectors(rq: req, offset: blk_rq_pos(rq: req))) |
678 | goto no_merge; |
679 | |
680 | req->nr_phys_segments = segments + blk_rq_nr_discard_segments(rq: next); |
681 | return true; |
682 | no_merge: |
683 | req_set_nomerge(q, req); |
684 | return false; |
685 | } |
686 | |
687 | static 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, bio: next->bio)) |
693 | return 0; |
694 | |
695 | /* |
696 | * Will it become too large? |
697 | */ |
698 | if ((blk_rq_sectors(rq: req) + blk_rq_sectors(rq: next)) > |
699 | blk_rq_get_max_sectors(rq: req, offset: blk_rq_pos(rq: 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(rq: req)) |
704 | return 0; |
705 | |
706 | if (!blk_cgroup_mergeable(rq: req, bio: 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 | */ |
729 | static void 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 | |
750 | static 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 | */ |
763 | static 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 | |
777 | static void blk_account_io_merge_request(struct request *req) |
778 | { |
779 | if (blk_do_io_stat(rq: 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 | |
786 | static 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(rq: req) + blk_rq_sectors(rq: req) == blk_rq_pos(rq: 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 | */ |
801 | static struct request *attempt_merge(struct request_queue *q, |
802 | struct request *req, struct request *next) |
803 | { |
804 | if (!rq_mergeable(rq: req) || !rq_mergeable(rq: next)) |
805 | return NULL; |
806 | |
807 | if (req_op(req) != req_op(req: next)) |
808 | return NULL; |
809 | |
810 | if (rq_data_dir(req) != rq_data_dir(next)) |
811 | return NULL; |
812 | |
813 | /* Don't merge requests with different write hints. */ |
814 | if (req->write_hint != next->write_hint) |
815 | return NULL; |
816 | |
817 | if (req->ioprio != next->ioprio) |
818 | return NULL; |
819 | |
820 | /* |
821 | * If we are allowed to merge, then append bio list |
822 | * from next to rq and release next. merge_requests_fn |
823 | * will have updated segment counts, update sector |
824 | * counts here. Handle DISCARDs separately, as they |
825 | * have separate settings. |
826 | */ |
827 | |
828 | switch (blk_try_req_merge(req, next)) { |
829 | case ELEVATOR_DISCARD_MERGE: |
830 | if (!req_attempt_discard_merge(q, req, next)) |
831 | return NULL; |
832 | break; |
833 | case ELEVATOR_BACK_MERGE: |
834 | if (!ll_merge_requests_fn(q, req, next)) |
835 | return NULL; |
836 | break; |
837 | default: |
838 | return NULL; |
839 | } |
840 | |
841 | /* |
842 | * If failfast settings disagree or any of the two is already |
843 | * a mixed merge, mark both as mixed before proceeding. This |
844 | * makes sure that all involved bios have mixable attributes |
845 | * set properly. |
846 | */ |
847 | if (((req->rq_flags | next->rq_flags) & RQF_MIXED_MERGE) || |
848 | (req->cmd_flags & REQ_FAILFAST_MASK) != |
849 | (next->cmd_flags & REQ_FAILFAST_MASK)) { |
850 | blk_rq_set_mixed_merge(rq: req); |
851 | blk_rq_set_mixed_merge(rq: next); |
852 | } |
853 | |
854 | /* |
855 | * At this point we have either done a back merge or front merge. We |
856 | * need the smaller start_time_ns of the merged requests to be the |
857 | * current request for accounting purposes. |
858 | */ |
859 | if (next->start_time_ns < req->start_time_ns) |
860 | req->start_time_ns = next->start_time_ns; |
861 | |
862 | req->biotail->bi_next = next->bio; |
863 | req->biotail = next->biotail; |
864 | |
865 | req->__data_len += blk_rq_bytes(rq: next); |
866 | |
867 | if (!blk_discard_mergable(req)) |
868 | elv_merge_requests(q, req, next); |
869 | |
870 | blk_crypto_rq_put_keyslot(rq: next); |
871 | |
872 | /* |
873 | * 'next' is going away, so update stats accordingly |
874 | */ |
875 | blk_account_io_merge_request(req: next); |
876 | |
877 | trace_block_rq_merge(rq: next); |
878 | |
879 | /* |
880 | * ownership of bio passed from next to req, return 'next' for |
881 | * the caller to free |
882 | */ |
883 | next->bio = NULL; |
884 | return next; |
885 | } |
886 | |
887 | static struct request *attempt_back_merge(struct request_queue *q, |
888 | struct request *rq) |
889 | { |
890 | struct request *next = elv_latter_request(q, rq); |
891 | |
892 | if (next) |
893 | return attempt_merge(q, req: rq, next); |
894 | |
895 | return NULL; |
896 | } |
897 | |
898 | static struct request *attempt_front_merge(struct request_queue *q, |
899 | struct request *rq) |
900 | { |
901 | struct request *prev = elv_former_request(q, rq); |
902 | |
903 | if (prev) |
904 | return attempt_merge(q, req: prev, next: rq); |
905 | |
906 | return NULL; |
907 | } |
908 | |
909 | /* |
910 | * Try to merge 'next' into 'rq'. Return true if the merge happened, false |
911 | * otherwise. The caller is responsible for freeing 'next' if the merge |
912 | * happened. |
913 | */ |
914 | bool blk_attempt_req_merge(struct request_queue *q, struct request *rq, |
915 | struct request *next) |
916 | { |
917 | return attempt_merge(q, req: rq, next); |
918 | } |
919 | |
920 | bool blk_rq_merge_ok(struct request *rq, struct bio *bio) |
921 | { |
922 | if (!rq_mergeable(rq) || !bio_mergeable(bio)) |
923 | return false; |
924 | |
925 | if (req_op(req: rq) != bio_op(bio)) |
926 | return false; |
927 | |
928 | /* different data direction or already started, don't merge */ |
929 | if (bio_data_dir(bio) != rq_data_dir(rq)) |
930 | return false; |
931 | |
932 | /* don't merge across cgroup boundaries */ |
933 | if (!blk_cgroup_mergeable(rq, bio)) |
934 | return false; |
935 | |
936 | /* only merge integrity protected bio into ditto rq */ |
937 | if (blk_integrity_merge_bio(rq->q, rq, bio) == false) |
938 | return false; |
939 | |
940 | /* Only merge if the crypt contexts are compatible */ |
941 | if (!bio_crypt_rq_ctx_compatible(rq, bio)) |
942 | return false; |
943 | |
944 | /* Don't merge requests with different write hints. */ |
945 | if (rq->write_hint != bio->bi_write_hint) |
946 | return false; |
947 | |
948 | if (rq->ioprio != bio_prio(bio)) |
949 | return false; |
950 | |
951 | return true; |
952 | } |
953 | |
954 | enum elv_merge blk_try_merge(struct request *rq, struct bio *bio) |
955 | { |
956 | if (blk_discard_mergable(req: rq)) |
957 | return ELEVATOR_DISCARD_MERGE; |
958 | else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector) |
959 | return ELEVATOR_BACK_MERGE; |
960 | else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector) |
961 | return ELEVATOR_FRONT_MERGE; |
962 | return ELEVATOR_NO_MERGE; |
963 | } |
964 | |
965 | static void blk_account_io_merge_bio(struct request *req) |
966 | { |
967 | if (!blk_do_io_stat(rq: req)) |
968 | return; |
969 | |
970 | part_stat_lock(); |
971 | part_stat_inc(req->part, merges[op_stat_group(req_op(req))]); |
972 | part_stat_unlock(); |
973 | } |
974 | |
975 | enum bio_merge_status { |
976 | BIO_MERGE_OK, |
977 | BIO_MERGE_NONE, |
978 | BIO_MERGE_FAILED, |
979 | }; |
980 | |
981 | static enum bio_merge_status bio_attempt_back_merge(struct request *req, |
982 | struct bio *bio, unsigned int nr_segs) |
983 | { |
984 | const blk_opf_t ff = bio_failfast(bio); |
985 | |
986 | if (!ll_back_merge_fn(req, bio, nr_segs)) |
987 | return BIO_MERGE_FAILED; |
988 | |
989 | trace_block_bio_backmerge(bio); |
990 | rq_qos_merge(q: req->q, rq: req, bio); |
991 | |
992 | if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff) |
993 | blk_rq_set_mixed_merge(rq: req); |
994 | |
995 | blk_update_mixed_merge(req, bio, front_merge: false); |
996 | |
997 | req->biotail->bi_next = bio; |
998 | req->biotail = bio; |
999 | req->__data_len += bio->bi_iter.bi_size; |
1000 | |
1001 | bio_crypt_free_ctx(bio); |
1002 | |
1003 | blk_account_io_merge_bio(req); |
1004 | return BIO_MERGE_OK; |
1005 | } |
1006 | |
1007 | static enum bio_merge_status bio_attempt_front_merge(struct request *req, |
1008 | struct bio *bio, unsigned int nr_segs) |
1009 | { |
1010 | const blk_opf_t ff = bio_failfast(bio); |
1011 | |
1012 | if (!ll_front_merge_fn(req, bio, nr_segs)) |
1013 | return BIO_MERGE_FAILED; |
1014 | |
1015 | trace_block_bio_frontmerge(bio); |
1016 | rq_qos_merge(q: req->q, rq: req, bio); |
1017 | |
1018 | if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff) |
1019 | blk_rq_set_mixed_merge(rq: req); |
1020 | |
1021 | blk_update_mixed_merge(req, bio, front_merge: true); |
1022 | |
1023 | bio->bi_next = req->bio; |
1024 | req->bio = bio; |
1025 | |
1026 | req->__sector = bio->bi_iter.bi_sector; |
1027 | req->__data_len += bio->bi_iter.bi_size; |
1028 | |
1029 | bio_crypt_do_front_merge(rq: req, bio); |
1030 | |
1031 | blk_account_io_merge_bio(req); |
1032 | return BIO_MERGE_OK; |
1033 | } |
1034 | |
1035 | static enum bio_merge_status bio_attempt_discard_merge(struct request_queue *q, |
1036 | struct request *req, struct bio *bio) |
1037 | { |
1038 | unsigned short segments = blk_rq_nr_discard_segments(rq: req); |
1039 | |
1040 | if (segments >= queue_max_discard_segments(q)) |
1041 | goto no_merge; |
1042 | if (blk_rq_sectors(rq: req) + bio_sectors(bio) > |
1043 | blk_rq_get_max_sectors(rq: req, offset: blk_rq_pos(rq: req))) |
1044 | goto no_merge; |
1045 | |
1046 | rq_qos_merge(q, rq: req, bio); |
1047 | |
1048 | req->biotail->bi_next = bio; |
1049 | req->biotail = bio; |
1050 | req->__data_len += bio->bi_iter.bi_size; |
1051 | req->nr_phys_segments = segments + 1; |
1052 | |
1053 | blk_account_io_merge_bio(req); |
1054 | return BIO_MERGE_OK; |
1055 | no_merge: |
1056 | req_set_nomerge(q, req); |
1057 | return BIO_MERGE_FAILED; |
1058 | } |
1059 | |
1060 | static enum bio_merge_status blk_attempt_bio_merge(struct request_queue *q, |
1061 | struct request *rq, |
1062 | struct bio *bio, |
1063 | unsigned int nr_segs, |
1064 | bool sched_allow_merge) |
1065 | { |
1066 | if (!blk_rq_merge_ok(rq, bio)) |
1067 | return BIO_MERGE_NONE; |
1068 | |
1069 | switch (blk_try_merge(rq, bio)) { |
1070 | case ELEVATOR_BACK_MERGE: |
1071 | if (!sched_allow_merge || blk_mq_sched_allow_merge(q, rq, bio)) |
1072 | return bio_attempt_back_merge(req: rq, bio, nr_segs); |
1073 | break; |
1074 | case ELEVATOR_FRONT_MERGE: |
1075 | if (!sched_allow_merge || blk_mq_sched_allow_merge(q, rq, bio)) |
1076 | return bio_attempt_front_merge(req: rq, bio, nr_segs); |
1077 | break; |
1078 | case ELEVATOR_DISCARD_MERGE: |
1079 | return bio_attempt_discard_merge(q, req: rq, bio); |
1080 | default: |
1081 | return BIO_MERGE_NONE; |
1082 | } |
1083 | |
1084 | return BIO_MERGE_FAILED; |
1085 | } |
1086 | |
1087 | /** |
1088 | * blk_attempt_plug_merge - try to merge with %current's plugged list |
1089 | * @q: request_queue new bio is being queued at |
1090 | * @bio: new bio being queued |
1091 | * @nr_segs: number of segments in @bio |
1092 | * from the passed in @q already in the plug list |
1093 | * |
1094 | * Determine whether @bio being queued on @q can be merged with the previous |
1095 | * request on %current's plugged list. Returns %true if merge was successful, |
1096 | * otherwise %false. |
1097 | * |
1098 | * Plugging coalesces IOs from the same issuer for the same purpose without |
1099 | * going through @q->queue_lock. As such it's more of an issuing mechanism |
1100 | * than scheduling, and the request, while may have elvpriv data, is not |
1101 | * added on the elevator at this point. In addition, we don't have |
1102 | * reliable access to the elevator outside queue lock. Only check basic |
1103 | * merging parameters without querying the elevator. |
1104 | * |
1105 | * Caller must ensure !blk_queue_nomerges(q) beforehand. |
1106 | */ |
1107 | bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio, |
1108 | unsigned int nr_segs) |
1109 | { |
1110 | struct blk_plug *plug; |
1111 | struct request *rq; |
1112 | |
1113 | plug = blk_mq_plug(bio); |
1114 | if (!plug || rq_list_empty(plug->mq_list)) |
1115 | return false; |
1116 | |
1117 | rq_list_for_each(&plug->mq_list, rq) { |
1118 | if (rq->q == q) { |
1119 | if (blk_attempt_bio_merge(q, rq, bio, nr_segs, sched_allow_merge: false) == |
1120 | BIO_MERGE_OK) |
1121 | return true; |
1122 | break; |
1123 | } |
1124 | |
1125 | /* |
1126 | * Only keep iterating plug list for merges if we have multiple |
1127 | * queues |
1128 | */ |
1129 | if (!plug->multiple_queues) |
1130 | break; |
1131 | } |
1132 | return false; |
1133 | } |
1134 | |
1135 | /* |
1136 | * Iterate list of requests and see if we can merge this bio with any |
1137 | * of them. |
1138 | */ |
1139 | bool blk_bio_list_merge(struct request_queue *q, struct list_head *list, |
1140 | struct bio *bio, unsigned int nr_segs) |
1141 | { |
1142 | struct request *rq; |
1143 | int checked = 8; |
1144 | |
1145 | list_for_each_entry_reverse(rq, list, queuelist) { |
1146 | if (!checked--) |
1147 | break; |
1148 | |
1149 | switch (blk_attempt_bio_merge(q, rq, bio, nr_segs, sched_allow_merge: true)) { |
1150 | case BIO_MERGE_NONE: |
1151 | continue; |
1152 | case BIO_MERGE_OK: |
1153 | return true; |
1154 | case BIO_MERGE_FAILED: |
1155 | return false; |
1156 | } |
1157 | |
1158 | } |
1159 | |
1160 | return false; |
1161 | } |
1162 | EXPORT_SYMBOL_GPL(blk_bio_list_merge); |
1163 | |
1164 | bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio, |
1165 | unsigned int nr_segs, struct request **merged_request) |
1166 | { |
1167 | struct request *rq; |
1168 | |
1169 | switch (elv_merge(q, &rq, bio)) { |
1170 | case ELEVATOR_BACK_MERGE: |
1171 | if (!blk_mq_sched_allow_merge(q, rq, bio)) |
1172 | return false; |
1173 | if (bio_attempt_back_merge(req: rq, bio, nr_segs) != BIO_MERGE_OK) |
1174 | return false; |
1175 | *merged_request = attempt_back_merge(q, rq); |
1176 | if (!*merged_request) |
1177 | elv_merged_request(q, rq, ELEVATOR_BACK_MERGE); |
1178 | return true; |
1179 | case ELEVATOR_FRONT_MERGE: |
1180 | if (!blk_mq_sched_allow_merge(q, rq, bio)) |
1181 | return false; |
1182 | if (bio_attempt_front_merge(req: rq, bio, nr_segs) != BIO_MERGE_OK) |
1183 | return false; |
1184 | *merged_request = attempt_front_merge(q, rq); |
1185 | if (!*merged_request) |
1186 | elv_merged_request(q, rq, ELEVATOR_FRONT_MERGE); |
1187 | return true; |
1188 | case ELEVATOR_DISCARD_MERGE: |
1189 | return bio_attempt_discard_merge(q, req: rq, bio) == BIO_MERGE_OK; |
1190 | default: |
1191 | return false; |
1192 | } |
1193 | } |
1194 | EXPORT_SYMBOL_GPL(blk_mq_sched_try_merge); |
1195 | |