Line data Source code
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 0 : *bv = mp_bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter);
24 : }
25 :
26 0 : static inline void bio_get_last_bvec(struct bio *bio, struct bio_vec *bv)
27 : {
28 0 : struct bvec_iter iter = bio->bi_iter;
29 : int idx;
30 :
31 0 : bio_get_first_bvec(bio, bv);
32 0 : if (bv->bv_len == bio->bi_iter.bi_size)
33 0 : return; /* this bio only has a single bvec */
34 :
35 0 : bio_advance_iter(bio, &iter, iter.bi_size);
36 :
37 0 : if (!iter.bi_bvec_done)
38 0 : idx = iter.bi_idx - 1;
39 : else /* in the middle of bvec */
40 0 : idx = iter.bi_idx;
41 :
42 0 : *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 0 : if (iter.bi_bvec_done)
49 0 : bv->bv_len = iter.bi_bvec_done;
50 : }
51 :
52 0 : 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 0 : 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 0 : if (prev_rq)
66 0 : bio_get_first_bvec(prev_rq->bio, &pb);
67 : else
68 : bio_get_first_bvec(prev, &pb);
69 0 : 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 0 : bio_get_last_bvec(prev, &pb);
82 0 : bio_get_first_bvec(next, &nb);
83 0 : if (biovec_phys_mergeable(q, &pb, &nb))
84 : return false;
85 0 : return __bvec_gap_to_prev(&q->limits, &pb, nb.bv_offset);
86 : }
87 :
88 : static inline bool req_gap_back_merge(struct request *req, struct bio *bio)
89 : {
90 0 : return bio_will_gap(req->q, req, req->biotail, bio);
91 : }
92 :
93 : static inline bool req_gap_front_merge(struct request *req, struct bio *bio)
94 : {
95 0 : 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 : */
103 : static unsigned int bio_allowed_max_sectors(const struct queue_limits *lim)
104 : {
105 0 : return round_down(UINT_MAX, lim->logical_block_size) >> SECTOR_SHIFT;
106 : }
107 :
108 0 : 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 0 : *nsegs = 1;
117 :
118 : /* Zero-sector (unknown) and one-sector granularities are the same. */
119 0 : granularity = max(lim->discard_granularity >> 9, 1U);
120 :
121 0 : max_discard_sectors =
122 0 : min(lim->max_discard_sectors, bio_allowed_max_sectors(lim));
123 0 : max_discard_sectors -= max_discard_sectors % granularity;
124 :
125 0 : if (unlikely(!max_discard_sectors)) {
126 : /* XXX: warn */
127 : return NULL;
128 : }
129 :
130 0 : if (bio_sectors(bio) <= max_discard_sectors)
131 : return NULL;
132 :
133 0 : split_sectors = max_discard_sectors;
134 :
135 : /*
136 : * If the next starting sector would be misaligned, stop the discard at
137 : * the previous aligned sector.
138 : */
139 0 : tmp = bio->bi_iter.bi_sector + split_sectors -
140 0 : ((lim->discard_alignment >> 9) % granularity);
141 0 : tmp = sector_div(tmp, granularity);
142 :
143 0 : if (split_sectors > tmp)
144 0 : split_sectors -= tmp;
145 :
146 0 : return bio_split(bio, split_sectors, GFP_NOIO, bs);
147 : }
148 :
149 : static struct bio *bio_split_write_zeroes(struct bio *bio,
150 : const struct queue_limits *lim,
151 : unsigned *nsegs, struct bio_set *bs)
152 : {
153 0 : *nsegs = 0;
154 0 : if (!lim->max_write_zeroes_sectors)
155 : return NULL;
156 0 : if (bio_sectors(bio) <= lim->max_write_zeroes_sectors)
157 : return NULL;
158 0 : return bio_split(bio, lim->max_write_zeroes_sectors, GFP_NOIO, bs);
159 : }
160 :
161 : /*
162 : * Return the maximum number of sectors from the start of a bio that may be
163 : * submitted as a single request to a block device. If enough sectors remain,
164 : * align the end to the physical block size. Otherwise align the end to the
165 : * logical block size. This approach minimizes the number of non-aligned
166 : * requests that are submitted to a block device if the start of a bio is not
167 : * aligned to a physical block boundary.
168 : */
169 0 : static inline unsigned get_max_io_size(struct bio *bio,
170 : const struct queue_limits *lim)
171 : {
172 0 : unsigned pbs = lim->physical_block_size >> SECTOR_SHIFT;
173 0 : unsigned lbs = lim->logical_block_size >> SECTOR_SHIFT;
174 0 : unsigned max_sectors = lim->max_sectors, start, end;
175 :
176 0 : if (lim->chunk_sectors) {
177 0 : max_sectors = min(max_sectors,
178 : blk_chunk_sectors_left(bio->bi_iter.bi_sector,
179 : lim->chunk_sectors));
180 : }
181 :
182 0 : start = bio->bi_iter.bi_sector & (pbs - 1);
183 0 : end = (start + max_sectors) & ~(pbs - 1);
184 0 : if (end > start)
185 0 : return end - start;
186 0 : return max_sectors & ~(lbs - 1);
187 : }
188 :
189 : /**
190 : * get_max_segment_size() - maximum number of bytes to add as a single segment
191 : * @lim: Request queue limits.
192 : * @start_page: See below.
193 : * @offset: Offset from @start_page where to add a segment.
194 : *
195 : * Returns the maximum number of bytes that can be added as a single segment.
196 : */
197 : static inline unsigned get_max_segment_size(const struct queue_limits *lim,
198 : struct page *start_page, unsigned long offset)
199 : {
200 0 : unsigned long mask = lim->seg_boundary_mask;
201 :
202 0 : offset = mask & (page_to_phys(start_page) + offset);
203 :
204 : /*
205 : * Prevent an overflow if mask = ULONG_MAX and offset = 0 by adding 1
206 : * after having calculated the minimum.
207 : */
208 0 : return min(mask - offset, (unsigned long)lim->max_segment_size - 1) + 1;
209 : }
210 :
211 : /**
212 : * bvec_split_segs - verify whether or not a bvec should be split in the middle
213 : * @lim: [in] queue limits to split based on
214 : * @bv: [in] bvec to examine
215 : * @nsegs: [in,out] Number of segments in the bio being built. Incremented
216 : * by the number of segments from @bv that may be appended to that
217 : * bio without exceeding @max_segs
218 : * @bytes: [in,out] Number of bytes in the bio being built. Incremented
219 : * by the number of bytes from @bv that may be appended to that
220 : * bio without exceeding @max_bytes
221 : * @max_segs: [in] upper bound for *@nsegs
222 : * @max_bytes: [in] upper bound for *@bytes
223 : *
224 : * When splitting a bio, it can happen that a bvec is encountered that is too
225 : * big to fit in a single segment and hence that it has to be split in the
226 : * middle. This function verifies whether or not that should happen. The value
227 : * %true is returned if and only if appending the entire @bv to a bio with
228 : * *@nsegs segments and *@sectors sectors would make that bio unacceptable for
229 : * the block driver.
230 : */
231 0 : static bool bvec_split_segs(const struct queue_limits *lim,
232 : const struct bio_vec *bv, unsigned *nsegs, unsigned *bytes,
233 : unsigned max_segs, unsigned max_bytes)
234 : {
235 0 : unsigned max_len = min(max_bytes, UINT_MAX) - *bytes;
236 0 : unsigned len = min(bv->bv_len, max_len);
237 0 : unsigned total_len = 0;
238 0 : unsigned seg_size = 0;
239 :
240 0 : while (len && *nsegs < max_segs) {
241 0 : seg_size = get_max_segment_size(lim, bv->bv_page,
242 0 : bv->bv_offset + total_len);
243 0 : seg_size = min(seg_size, len);
244 :
245 0 : (*nsegs)++;
246 0 : total_len += seg_size;
247 0 : len -= seg_size;
248 :
249 0 : if ((bv->bv_offset + total_len) & lim->virt_boundary_mask)
250 : break;
251 : }
252 :
253 0 : *bytes += total_len;
254 :
255 : /* tell the caller to split the bvec if it is too big to fit */
256 0 : return len > 0 || bv->bv_len > max_len;
257 : }
258 :
259 : /**
260 : * bio_split_rw - split a bio in two bios
261 : * @bio: [in] bio to be split
262 : * @lim: [in] queue limits to split based on
263 : * @segs: [out] number of segments in the bio with the first half of the sectors
264 : * @bs: [in] bio set to allocate the clone from
265 : * @max_bytes: [in] maximum number of bytes per bio
266 : *
267 : * Clone @bio, update the bi_iter of the clone to represent the first sectors
268 : * of @bio and update @bio->bi_iter to represent the remaining sectors. The
269 : * following is guaranteed for the cloned bio:
270 : * - That it has at most @max_bytes worth of data
271 : * - That it has at most queue_max_segments(@q) segments.
272 : *
273 : * Except for discard requests the cloned bio will point at the bi_io_vec of
274 : * the original bio. It is the responsibility of the caller to ensure that the
275 : * original bio is not freed before the cloned bio. The caller is also
276 : * responsible for ensuring that @bs is only destroyed after processing of the
277 : * split bio has finished.
278 : */
279 0 : struct bio *bio_split_rw(struct bio *bio, const struct queue_limits *lim,
280 : unsigned *segs, struct bio_set *bs, unsigned max_bytes)
281 : {
282 0 : struct bio_vec bv, bvprv, *bvprvp = NULL;
283 : struct bvec_iter iter;
284 0 : unsigned nsegs = 0, bytes = 0;
285 :
286 0 : bio_for_each_bvec(bv, bio, iter) {
287 : /*
288 : * If the queue doesn't support SG gaps and adding this
289 : * offset would create a gap, disallow it.
290 : */
291 0 : if (bvprvp && bvec_gap_to_prev(lim, bvprvp, bv.bv_offset))
292 : goto split;
293 :
294 0 : if (nsegs < lim->max_segments &&
295 0 : bytes + bv.bv_len <= max_bytes &&
296 0 : bv.bv_offset + bv.bv_len <= PAGE_SIZE) {
297 0 : nsegs++;
298 0 : bytes += bv.bv_len;
299 : } else {
300 0 : if (bvec_split_segs(lim, &bv, &nsegs, &bytes,
301 : lim->max_segments, max_bytes))
302 : goto split;
303 : }
304 :
305 0 : bvprv = bv;
306 0 : bvprvp = &bvprv;
307 : }
308 :
309 0 : *segs = nsegs;
310 0 : return NULL;
311 : split:
312 : /*
313 : * We can't sanely support splitting for a REQ_NOWAIT bio. End it
314 : * with EAGAIN if splitting is required and return an error pointer.
315 : */
316 0 : if (bio->bi_opf & REQ_NOWAIT) {
317 0 : bio->bi_status = BLK_STS_AGAIN;
318 0 : bio_endio(bio);
319 0 : return ERR_PTR(-EAGAIN);
320 : }
321 :
322 0 : *segs = nsegs;
323 :
324 : /*
325 : * Individual bvecs might not be logical block aligned. Round down the
326 : * split size so that each bio is properly block size aligned, even if
327 : * we do not use the full hardware limits.
328 : */
329 0 : bytes = ALIGN_DOWN(bytes, lim->logical_block_size);
330 :
331 : /*
332 : * Bio splitting may cause subtle trouble such as hang when doing sync
333 : * iopoll in direct IO routine. Given performance gain of iopoll for
334 : * big IO can be trival, disable iopoll when split needed.
335 : */
336 0 : bio_clear_polled(bio);
337 0 : return bio_split(bio, bytes >> SECTOR_SHIFT, GFP_NOIO, bs);
338 : }
339 : EXPORT_SYMBOL_GPL(bio_split_rw);
340 :
341 : /**
342 : * __bio_split_to_limits - split a bio to fit the queue limits
343 : * @bio: bio to be split
344 : * @lim: queue limits to split based on
345 : * @nr_segs: returns the number of segments in the returned bio
346 : *
347 : * Check if @bio needs splitting based on the queue limits, and if so split off
348 : * a bio fitting the limits from the beginning of @bio and return it. @bio is
349 : * shortened to the remainder and re-submitted.
350 : *
351 : * The split bio is allocated from @q->bio_split, which is provided by the
352 : * block layer.
353 : */
354 0 : struct bio *__bio_split_to_limits(struct bio *bio,
355 : const struct queue_limits *lim,
356 : unsigned int *nr_segs)
357 : {
358 0 : struct bio_set *bs = &bio->bi_bdev->bd_disk->bio_split;
359 : struct bio *split;
360 :
361 0 : switch (bio_op(bio)) {
362 : case REQ_OP_DISCARD:
363 : case REQ_OP_SECURE_ERASE:
364 0 : split = bio_split_discard(bio, lim, nr_segs, bs);
365 0 : break;
366 : case REQ_OP_WRITE_ZEROES:
367 0 : split = bio_split_write_zeroes(bio, lim, nr_segs, bs);
368 : break;
369 : default:
370 0 : split = bio_split_rw(bio, lim, nr_segs, bs,
371 0 : get_max_io_size(bio, lim) << SECTOR_SHIFT);
372 0 : if (IS_ERR(split))
373 : return NULL;
374 : break;
375 : }
376 :
377 0 : if (split) {
378 : /* there isn't chance to merge the split bio */
379 0 : split->bi_opf |= REQ_NOMERGE;
380 :
381 0 : blkcg_bio_issue_init(split);
382 0 : bio_chain(split, bio);
383 0 : trace_block_split(split, bio->bi_iter.bi_sector);
384 0 : submit_bio_noacct(bio);
385 0 : return split;
386 : }
387 : return bio;
388 : }
389 :
390 : /**
391 : * bio_split_to_limits - split a bio to fit the queue limits
392 : * @bio: bio to be split
393 : *
394 : * Check if @bio needs splitting based on the queue limits of @bio->bi_bdev, and
395 : * if so split off a bio fitting the limits from the beginning of @bio and
396 : * return it. @bio is shortened to the remainder and re-submitted.
397 : *
398 : * The split bio is allocated from @q->bio_split, which is provided by the
399 : * block layer.
400 : */
401 0 : struct bio *bio_split_to_limits(struct bio *bio)
402 : {
403 0 : const struct queue_limits *lim = &bdev_get_queue(bio->bi_bdev)->limits;
404 : unsigned int nr_segs;
405 :
406 0 : if (bio_may_exceed_limits(bio, lim))
407 0 : return __bio_split_to_limits(bio, lim, &nr_segs);
408 : return bio;
409 : }
410 : EXPORT_SYMBOL(bio_split_to_limits);
411 :
412 0 : unsigned int blk_recalc_rq_segments(struct request *rq)
413 : {
414 0 : unsigned int nr_phys_segs = 0;
415 0 : unsigned int bytes = 0;
416 : struct req_iterator iter;
417 : struct bio_vec bv;
418 :
419 0 : if (!rq->bio)
420 : return 0;
421 :
422 0 : switch (bio_op(rq->bio)) {
423 : case REQ_OP_DISCARD:
424 : case REQ_OP_SECURE_ERASE:
425 0 : if (queue_max_discard_segments(rq->q) > 1) {
426 : struct bio *bio = rq->bio;
427 :
428 0 : for_each_bio(bio)
429 0 : nr_phys_segs++;
430 0 : return nr_phys_segs;
431 : }
432 : return 1;
433 : case REQ_OP_WRITE_ZEROES:
434 : return 0;
435 : default:
436 : break;
437 : }
438 :
439 0 : rq_for_each_bvec(bv, rq, iter)
440 0 : bvec_split_segs(&rq->q->limits, &bv, &nr_phys_segs, &bytes,
441 : UINT_MAX, UINT_MAX);
442 0 : return nr_phys_segs;
443 : }
444 :
445 : static inline struct scatterlist *blk_next_sg(struct scatterlist **sg,
446 : struct scatterlist *sglist)
447 : {
448 0 : if (!*sg)
449 : return sglist;
450 :
451 : /*
452 : * If the driver previously mapped a shorter list, we could see a
453 : * termination bit prematurely unless it fully inits the sg table
454 : * on each mapping. We KNOW that there must be more entries here
455 : * or the driver would be buggy, so force clear the termination bit
456 : * to avoid doing a full sg_init_table() in drivers for each command.
457 : */
458 0 : sg_unmark_end(*sg);
459 0 : return sg_next(*sg);
460 : }
461 :
462 0 : static unsigned blk_bvec_map_sg(struct request_queue *q,
463 : struct bio_vec *bvec, struct scatterlist *sglist,
464 : struct scatterlist **sg)
465 : {
466 0 : unsigned nbytes = bvec->bv_len;
467 0 : unsigned nsegs = 0, total = 0;
468 :
469 0 : while (nbytes > 0) {
470 0 : unsigned offset = bvec->bv_offset + total;
471 0 : unsigned len = min(get_max_segment_size(&q->limits,
472 : bvec->bv_page, offset), nbytes);
473 0 : struct page *page = bvec->bv_page;
474 :
475 : /*
476 : * Unfortunately a fair number of drivers barf on scatterlists
477 : * that have an offset larger than PAGE_SIZE, despite other
478 : * subsystems dealing with that invariant just fine. For now
479 : * stick to the legacy format where we never present those from
480 : * the block layer, but the code below should be removed once
481 : * these offenders (mostly MMC/SD drivers) are fixed.
482 : */
483 0 : page += (offset >> PAGE_SHIFT);
484 0 : offset &= ~PAGE_MASK;
485 :
486 0 : *sg = blk_next_sg(sg, sglist);
487 0 : sg_set_page(*sg, page, len, offset);
488 :
489 0 : total += len;
490 0 : nbytes -= len;
491 0 : nsegs++;
492 : }
493 :
494 0 : return nsegs;
495 : }
496 :
497 0 : static inline int __blk_bvec_map_sg(struct bio_vec bv,
498 : struct scatterlist *sglist, struct scatterlist **sg)
499 : {
500 0 : *sg = blk_next_sg(sg, sglist);
501 0 : sg_set_page(*sg, bv.bv_page, bv.bv_len, bv.bv_offset);
502 0 : return 1;
503 : }
504 :
505 : /* only try to merge bvecs into one sg if they are from two bios */
506 : static inline bool
507 0 : __blk_segment_map_sg_merge(struct request_queue *q, struct bio_vec *bvec,
508 : struct bio_vec *bvprv, struct scatterlist **sg)
509 : {
510 :
511 0 : int nbytes = bvec->bv_len;
512 :
513 0 : if (!*sg)
514 : return false;
515 :
516 0 : if ((*sg)->length + nbytes > queue_max_segment_size(q))
517 : return false;
518 :
519 0 : if (!biovec_phys_mergeable(q, bvprv, bvec))
520 : return false;
521 :
522 0 : (*sg)->length += nbytes;
523 :
524 : return true;
525 : }
526 :
527 0 : static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio,
528 : struct scatterlist *sglist,
529 : struct scatterlist **sg)
530 : {
531 0 : struct bio_vec bvec, bvprv = { NULL };
532 : struct bvec_iter iter;
533 0 : int nsegs = 0;
534 0 : bool new_bio = false;
535 :
536 0 : for_each_bio(bio) {
537 0 : bio_for_each_bvec(bvec, bio, iter) {
538 : /*
539 : * Only try to merge bvecs from two bios given we
540 : * have done bio internal merge when adding pages
541 : * to bio
542 : */
543 0 : if (new_bio &&
544 0 : __blk_segment_map_sg_merge(q, &bvec, &bvprv, sg))
545 : goto next_bvec;
546 :
547 0 : if (bvec.bv_offset + bvec.bv_len <= PAGE_SIZE)
548 0 : nsegs += __blk_bvec_map_sg(bvec, sglist, sg);
549 : else
550 0 : nsegs += blk_bvec_map_sg(q, &bvec, sglist, sg);
551 : next_bvec:
552 0 : new_bio = false;
553 : }
554 0 : if (likely(bio->bi_iter.bi_size)) {
555 0 : bvprv = bvec;
556 0 : new_bio = true;
557 : }
558 : }
559 :
560 0 : return nsegs;
561 : }
562 :
563 : /*
564 : * map a request to scatterlist, return number of sg entries setup. Caller
565 : * must make sure sg can hold rq->nr_phys_segments entries
566 : */
567 0 : int __blk_rq_map_sg(struct request_queue *q, struct request *rq,
568 : struct scatterlist *sglist, struct scatterlist **last_sg)
569 : {
570 0 : int nsegs = 0;
571 :
572 0 : if (rq->rq_flags & RQF_SPECIAL_PAYLOAD)
573 0 : nsegs = __blk_bvec_map_sg(rq->special_vec, sglist, last_sg);
574 0 : else if (rq->bio)
575 0 : nsegs = __blk_bios_map_sg(q, rq->bio, sglist, last_sg);
576 :
577 0 : if (*last_sg)
578 0 : sg_mark_end(*last_sg);
579 :
580 : /*
581 : * Something must have been wrong if the figured number of
582 : * segment is bigger than number of req's physical segments
583 : */
584 0 : WARN_ON(nsegs > blk_rq_nr_phys_segments(rq));
585 :
586 0 : return nsegs;
587 : }
588 : EXPORT_SYMBOL(__blk_rq_map_sg);
589 :
590 0 : static inline unsigned int blk_rq_get_max_sectors(struct request *rq,
591 : sector_t offset)
592 : {
593 0 : struct request_queue *q = rq->q;
594 : unsigned int max_sectors;
595 :
596 0 : if (blk_rq_is_passthrough(rq))
597 0 : return q->limits.max_hw_sectors;
598 :
599 0 : max_sectors = blk_queue_get_max_sectors(q, req_op(rq));
600 0 : if (!q->limits.chunk_sectors ||
601 0 : req_op(rq) == REQ_OP_DISCARD ||
602 0 : req_op(rq) == REQ_OP_SECURE_ERASE)
603 : return max_sectors;
604 0 : return min(max_sectors,
605 : blk_chunk_sectors_left(offset, q->limits.chunk_sectors));
606 : }
607 :
608 : static inline int ll_new_hw_segment(struct request *req, struct bio *bio,
609 : unsigned int nr_phys_segs)
610 : {
611 0 : if (!blk_cgroup_mergeable(req, bio))
612 : goto no_merge;
613 :
614 0 : if (blk_integrity_merge_bio(req->q, req, bio) == false)
615 : goto no_merge;
616 :
617 : /* discard request merge won't add new segment */
618 0 : if (req_op(req) == REQ_OP_DISCARD)
619 : return 1;
620 :
621 0 : if (req->nr_phys_segments + nr_phys_segs > blk_rq_get_max_segments(req))
622 : goto no_merge;
623 :
624 : /*
625 : * This will form the start of a new hw segment. Bump both
626 : * counters.
627 : */
628 0 : req->nr_phys_segments += nr_phys_segs;
629 : return 1;
630 :
631 : no_merge:
632 0 : req_set_nomerge(req->q, req);
633 : return 0;
634 : }
635 :
636 0 : int ll_back_merge_fn(struct request *req, struct bio *bio, unsigned int nr_segs)
637 : {
638 0 : if (req_gap_back_merge(req, bio))
639 : return 0;
640 0 : if (blk_integrity_rq(req) &&
641 : integrity_req_gap_back_merge(req, bio))
642 : return 0;
643 0 : if (!bio_crypt_ctx_back_mergeable(req, bio))
644 : return 0;
645 0 : if (blk_rq_sectors(req) + bio_sectors(bio) >
646 0 : blk_rq_get_max_sectors(req, blk_rq_pos(req))) {
647 0 : req_set_nomerge(req->q, req);
648 : return 0;
649 : }
650 :
651 0 : return ll_new_hw_segment(req, bio, nr_segs);
652 : }
653 :
654 0 : static int ll_front_merge_fn(struct request *req, struct bio *bio,
655 : unsigned int nr_segs)
656 : {
657 0 : if (req_gap_front_merge(req, bio))
658 : return 0;
659 0 : if (blk_integrity_rq(req) &&
660 : integrity_req_gap_front_merge(req, bio))
661 : return 0;
662 0 : if (!bio_crypt_ctx_front_mergeable(req, bio))
663 : return 0;
664 0 : if (blk_rq_sectors(req) + bio_sectors(bio) >
665 0 : blk_rq_get_max_sectors(req, bio->bi_iter.bi_sector)) {
666 0 : req_set_nomerge(req->q, req);
667 : return 0;
668 : }
669 :
670 0 : return ll_new_hw_segment(req, bio, nr_segs);
671 : }
672 :
673 0 : static bool req_attempt_discard_merge(struct request_queue *q, struct request *req,
674 : struct request *next)
675 : {
676 0 : unsigned short segments = blk_rq_nr_discard_segments(req);
677 :
678 0 : if (segments >= queue_max_discard_segments(q))
679 : goto no_merge;
680 0 : if (blk_rq_sectors(req) + bio_sectors(next->bio) >
681 0 : blk_rq_get_max_sectors(req, blk_rq_pos(req)))
682 : goto no_merge;
683 :
684 0 : req->nr_phys_segments = segments + blk_rq_nr_discard_segments(next);
685 0 : return true;
686 : no_merge:
687 0 : req_set_nomerge(q, req);
688 : return false;
689 : }
690 :
691 0 : static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
692 : struct request *next)
693 : {
694 : int total_phys_segments;
695 :
696 0 : if (req_gap_back_merge(req, next->bio))
697 : return 0;
698 :
699 : /*
700 : * Will it become too large?
701 : */
702 0 : if ((blk_rq_sectors(req) + blk_rq_sectors(next)) >
703 0 : blk_rq_get_max_sectors(req, blk_rq_pos(req)))
704 : return 0;
705 :
706 0 : total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
707 0 : if (total_phys_segments > blk_rq_get_max_segments(req))
708 : return 0;
709 :
710 0 : if (!blk_cgroup_mergeable(req, next->bio))
711 : return 0;
712 :
713 0 : if (blk_integrity_merge_rq(q, req, next) == false)
714 : return 0;
715 :
716 0 : if (!bio_crypt_ctx_merge_rq(req, next))
717 : return 0;
718 :
719 : /* Merge is OK... */
720 0 : req->nr_phys_segments = total_phys_segments;
721 : return 1;
722 : }
723 :
724 : /**
725 : * blk_rq_set_mixed_merge - mark a request as mixed merge
726 : * @rq: request to mark as mixed merge
727 : *
728 : * Description:
729 : * @rq is about to be mixed merged. Make sure the attributes
730 : * which can be mixed are set in each bio and mark @rq as mixed
731 : * merged.
732 : */
733 0 : void blk_rq_set_mixed_merge(struct request *rq)
734 : {
735 0 : blk_opf_t ff = rq->cmd_flags & REQ_FAILFAST_MASK;
736 : struct bio *bio;
737 :
738 0 : if (rq->rq_flags & RQF_MIXED_MERGE)
739 : return;
740 :
741 : /*
742 : * @rq will no longer represent mixable attributes for all the
743 : * contained bios. It will just track those of the first one.
744 : * Distributes the attributs to each bio.
745 : */
746 0 : for (bio = rq->bio; bio; bio = bio->bi_next) {
747 0 : WARN_ON_ONCE((bio->bi_opf & REQ_FAILFAST_MASK) &&
748 : (bio->bi_opf & REQ_FAILFAST_MASK) != ff);
749 0 : bio->bi_opf |= ff;
750 : }
751 0 : rq->rq_flags |= RQF_MIXED_MERGE;
752 : }
753 :
754 : static inline blk_opf_t bio_failfast(const struct bio *bio)
755 : {
756 0 : if (bio->bi_opf & REQ_RAHEAD)
757 : return REQ_FAILFAST_MASK;
758 :
759 0 : return bio->bi_opf & REQ_FAILFAST_MASK;
760 : }
761 :
762 : /*
763 : * After we are marked as MIXED_MERGE, any new RA bio has to be updated
764 : * as failfast, and request's failfast has to be updated in case of
765 : * front merge.
766 : */
767 : static inline void blk_update_mixed_merge(struct request *req,
768 : struct bio *bio, bool front_merge)
769 : {
770 0 : if (req->rq_flags & RQF_MIXED_MERGE) {
771 0 : if (bio->bi_opf & REQ_RAHEAD)
772 0 : bio->bi_opf |= REQ_FAILFAST_MASK;
773 :
774 : if (front_merge) {
775 0 : req->cmd_flags &= ~REQ_FAILFAST_MASK;
776 0 : req->cmd_flags |= bio->bi_opf & REQ_FAILFAST_MASK;
777 : }
778 : }
779 : }
780 :
781 0 : static void blk_account_io_merge_request(struct request *req)
782 : {
783 0 : if (blk_do_io_stat(req)) {
784 0 : part_stat_lock();
785 0 : part_stat_inc(req->part, merges[op_stat_group(req_op(req))]);
786 0 : part_stat_unlock();
787 : }
788 0 : }
789 :
790 : static enum elv_merge blk_try_req_merge(struct request *req,
791 : struct request *next)
792 : {
793 0 : if (blk_discard_mergable(req))
794 : return ELEVATOR_DISCARD_MERGE;
795 0 : else if (blk_rq_pos(req) + blk_rq_sectors(req) == blk_rq_pos(next))
796 : return ELEVATOR_BACK_MERGE;
797 :
798 : return ELEVATOR_NO_MERGE;
799 : }
800 :
801 : /*
802 : * For non-mq, this has to be called with the request spinlock acquired.
803 : * For mq with scheduling, the appropriate queue wide lock should be held.
804 : */
805 0 : static struct request *attempt_merge(struct request_queue *q,
806 : struct request *req, struct request *next)
807 : {
808 0 : if (!rq_mergeable(req) || !rq_mergeable(next))
809 : return NULL;
810 :
811 0 : if (req_op(req) != req_op(next))
812 : return NULL;
813 :
814 0 : if (rq_data_dir(req) != rq_data_dir(next))
815 : return NULL;
816 :
817 0 : 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 0 : switch (blk_try_req_merge(req, next)) {
829 : case ELEVATOR_DISCARD_MERGE:
830 0 : if (!req_attempt_discard_merge(q, req, next))
831 : return NULL;
832 : break;
833 : case ELEVATOR_BACK_MERGE:
834 0 : 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 0 : if (((req->rq_flags | next->rq_flags) & RQF_MIXED_MERGE) ||
848 0 : (req->cmd_flags & REQ_FAILFAST_MASK) !=
849 0 : (next->cmd_flags & REQ_FAILFAST_MASK)) {
850 0 : blk_rq_set_mixed_merge(req);
851 0 : blk_rq_set_mixed_merge(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 0 : if (next->start_time_ns < req->start_time_ns)
860 0 : req->start_time_ns = next->start_time_ns;
861 :
862 0 : req->biotail->bi_next = next->bio;
863 0 : req->biotail = next->biotail;
864 :
865 0 : req->__data_len += blk_rq_bytes(next);
866 :
867 0 : if (!blk_discard_mergable(req))
868 0 : elv_merge_requests(q, req, next);
869 :
870 : /*
871 : * 'next' is going away, so update stats accordingly
872 : */
873 0 : blk_account_io_merge_request(next);
874 :
875 0 : trace_block_rq_merge(next);
876 :
877 : /*
878 : * ownership of bio passed from next to req, return 'next' for
879 : * the caller to free
880 : */
881 0 : next->bio = NULL;
882 0 : return next;
883 : }
884 :
885 0 : static struct request *attempt_back_merge(struct request_queue *q,
886 : struct request *rq)
887 : {
888 0 : struct request *next = elv_latter_request(q, rq);
889 :
890 0 : if (next)
891 0 : return attempt_merge(q, rq, next);
892 :
893 : return NULL;
894 : }
895 :
896 0 : static struct request *attempt_front_merge(struct request_queue *q,
897 : struct request *rq)
898 : {
899 0 : struct request *prev = elv_former_request(q, rq);
900 :
901 0 : if (prev)
902 0 : return attempt_merge(q, prev, rq);
903 :
904 : return NULL;
905 : }
906 :
907 : /*
908 : * Try to merge 'next' into 'rq'. Return true if the merge happened, false
909 : * otherwise. The caller is responsible for freeing 'next' if the merge
910 : * happened.
911 : */
912 0 : bool blk_attempt_req_merge(struct request_queue *q, struct request *rq,
913 : struct request *next)
914 : {
915 0 : return attempt_merge(q, rq, next);
916 : }
917 :
918 0 : bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
919 : {
920 0 : if (!rq_mergeable(rq) || !bio_mergeable(bio))
921 : return false;
922 :
923 0 : if (req_op(rq) != bio_op(bio))
924 : return false;
925 :
926 : /* different data direction or already started, don't merge */
927 0 : if (bio_data_dir(bio) != rq_data_dir(rq))
928 : return false;
929 :
930 : /* don't merge across cgroup boundaries */
931 0 : if (!blk_cgroup_mergeable(rq, bio))
932 : return false;
933 :
934 : /* only merge integrity protected bio into ditto rq */
935 0 : if (blk_integrity_merge_bio(rq->q, rq, bio) == false)
936 : return false;
937 :
938 : /* Only merge if the crypt contexts are compatible */
939 0 : if (!bio_crypt_rq_ctx_compatible(rq, bio))
940 : return false;
941 :
942 0 : if (rq->ioprio != bio_prio(bio))
943 : return false;
944 :
945 0 : return true;
946 : }
947 :
948 0 : enum elv_merge blk_try_merge(struct request *rq, struct bio *bio)
949 : {
950 0 : if (blk_discard_mergable(rq))
951 : return ELEVATOR_DISCARD_MERGE;
952 0 : else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector)
953 : return ELEVATOR_BACK_MERGE;
954 0 : else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector)
955 : return ELEVATOR_FRONT_MERGE;
956 0 : return ELEVATOR_NO_MERGE;
957 : }
958 :
959 0 : static void blk_account_io_merge_bio(struct request *req)
960 : {
961 0 : if (!blk_do_io_stat(req))
962 : return;
963 :
964 0 : part_stat_lock();
965 0 : part_stat_inc(req->part, merges[op_stat_group(req_op(req))]);
966 0 : part_stat_unlock();
967 : }
968 :
969 : enum bio_merge_status {
970 : BIO_MERGE_OK,
971 : BIO_MERGE_NONE,
972 : BIO_MERGE_FAILED,
973 : };
974 :
975 0 : static enum bio_merge_status bio_attempt_back_merge(struct request *req,
976 : struct bio *bio, unsigned int nr_segs)
977 : {
978 0 : const blk_opf_t ff = bio_failfast(bio);
979 :
980 0 : if (!ll_back_merge_fn(req, bio, nr_segs))
981 : return BIO_MERGE_FAILED;
982 :
983 0 : trace_block_bio_backmerge(bio);
984 0 : rq_qos_merge(req->q, req, bio);
985 :
986 0 : if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
987 0 : blk_rq_set_mixed_merge(req);
988 :
989 0 : blk_update_mixed_merge(req, bio, false);
990 :
991 0 : req->biotail->bi_next = bio;
992 0 : req->biotail = bio;
993 0 : req->__data_len += bio->bi_iter.bi_size;
994 :
995 0 : bio_crypt_free_ctx(bio);
996 :
997 0 : blk_account_io_merge_bio(req);
998 0 : return BIO_MERGE_OK;
999 : }
1000 :
1001 0 : static enum bio_merge_status bio_attempt_front_merge(struct request *req,
1002 : struct bio *bio, unsigned int nr_segs)
1003 : {
1004 0 : const blk_opf_t ff = bio_failfast(bio);
1005 :
1006 0 : if (!ll_front_merge_fn(req, bio, nr_segs))
1007 : return BIO_MERGE_FAILED;
1008 :
1009 0 : trace_block_bio_frontmerge(bio);
1010 0 : rq_qos_merge(req->q, req, bio);
1011 :
1012 0 : if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
1013 0 : blk_rq_set_mixed_merge(req);
1014 :
1015 0 : blk_update_mixed_merge(req, bio, true);
1016 :
1017 0 : bio->bi_next = req->bio;
1018 0 : req->bio = bio;
1019 :
1020 0 : req->__sector = bio->bi_iter.bi_sector;
1021 0 : req->__data_len += bio->bi_iter.bi_size;
1022 :
1023 0 : bio_crypt_do_front_merge(req, bio);
1024 :
1025 0 : blk_account_io_merge_bio(req);
1026 0 : return BIO_MERGE_OK;
1027 : }
1028 :
1029 0 : static enum bio_merge_status bio_attempt_discard_merge(struct request_queue *q,
1030 : struct request *req, struct bio *bio)
1031 : {
1032 0 : unsigned short segments = blk_rq_nr_discard_segments(req);
1033 :
1034 0 : if (segments >= queue_max_discard_segments(q))
1035 : goto no_merge;
1036 0 : if (blk_rq_sectors(req) + bio_sectors(bio) >
1037 0 : blk_rq_get_max_sectors(req, blk_rq_pos(req)))
1038 : goto no_merge;
1039 :
1040 0 : rq_qos_merge(q, req, bio);
1041 :
1042 0 : req->biotail->bi_next = bio;
1043 0 : req->biotail = bio;
1044 0 : req->__data_len += bio->bi_iter.bi_size;
1045 0 : req->nr_phys_segments = segments + 1;
1046 :
1047 0 : blk_account_io_merge_bio(req);
1048 0 : return BIO_MERGE_OK;
1049 : no_merge:
1050 0 : req_set_nomerge(q, req);
1051 : return BIO_MERGE_FAILED;
1052 : }
1053 :
1054 0 : static enum bio_merge_status blk_attempt_bio_merge(struct request_queue *q,
1055 : struct request *rq,
1056 : struct bio *bio,
1057 : unsigned int nr_segs,
1058 : bool sched_allow_merge)
1059 : {
1060 0 : if (!blk_rq_merge_ok(rq, bio))
1061 : return BIO_MERGE_NONE;
1062 :
1063 0 : switch (blk_try_merge(rq, bio)) {
1064 : case ELEVATOR_BACK_MERGE:
1065 0 : if (!sched_allow_merge || blk_mq_sched_allow_merge(q, rq, bio))
1066 0 : return bio_attempt_back_merge(rq, bio, nr_segs);
1067 : break;
1068 : case ELEVATOR_FRONT_MERGE:
1069 0 : if (!sched_allow_merge || blk_mq_sched_allow_merge(q, rq, bio))
1070 0 : return bio_attempt_front_merge(rq, bio, nr_segs);
1071 : break;
1072 : case ELEVATOR_DISCARD_MERGE:
1073 0 : return bio_attempt_discard_merge(q, rq, bio);
1074 : default:
1075 : return BIO_MERGE_NONE;
1076 : }
1077 :
1078 : return BIO_MERGE_FAILED;
1079 : }
1080 :
1081 : /**
1082 : * blk_attempt_plug_merge - try to merge with %current's plugged list
1083 : * @q: request_queue new bio is being queued at
1084 : * @bio: new bio being queued
1085 : * @nr_segs: number of segments in @bio
1086 : * from the passed in @q already in the plug list
1087 : *
1088 : * Determine whether @bio being queued on @q can be merged with the previous
1089 : * request on %current's plugged list. Returns %true if merge was successful,
1090 : * otherwise %false.
1091 : *
1092 : * Plugging coalesces IOs from the same issuer for the same purpose without
1093 : * going through @q->queue_lock. As such it's more of an issuing mechanism
1094 : * than scheduling, and the request, while may have elvpriv data, is not
1095 : * added on the elevator at this point. In addition, we don't have
1096 : * reliable access to the elevator outside queue lock. Only check basic
1097 : * merging parameters without querying the elevator.
1098 : *
1099 : * Caller must ensure !blk_queue_nomerges(q) beforehand.
1100 : */
1101 0 : bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
1102 : unsigned int nr_segs)
1103 : {
1104 : struct blk_plug *plug;
1105 : struct request *rq;
1106 :
1107 0 : plug = blk_mq_plug(bio);
1108 0 : if (!plug || rq_list_empty(plug->mq_list))
1109 : return false;
1110 :
1111 0 : rq_list_for_each(&plug->mq_list, rq) {
1112 0 : if (rq->q == q) {
1113 0 : if (blk_attempt_bio_merge(q, rq, bio, nr_segs, false) ==
1114 : BIO_MERGE_OK)
1115 : return true;
1116 : break;
1117 : }
1118 :
1119 : /*
1120 : * Only keep iterating plug list for merges if we have multiple
1121 : * queues
1122 : */
1123 0 : if (!plug->multiple_queues)
1124 : break;
1125 : }
1126 : return false;
1127 : }
1128 :
1129 : /*
1130 : * Iterate list of requests and see if we can merge this bio with any
1131 : * of them.
1132 : */
1133 0 : bool blk_bio_list_merge(struct request_queue *q, struct list_head *list,
1134 : struct bio *bio, unsigned int nr_segs)
1135 : {
1136 : struct request *rq;
1137 0 : int checked = 8;
1138 :
1139 0 : list_for_each_entry_reverse(rq, list, queuelist) {
1140 0 : if (!checked--)
1141 : break;
1142 :
1143 0 : switch (blk_attempt_bio_merge(q, rq, bio, nr_segs, true)) {
1144 : case BIO_MERGE_NONE:
1145 0 : continue;
1146 : case BIO_MERGE_OK:
1147 : return true;
1148 : case BIO_MERGE_FAILED:
1149 0 : return false;
1150 : }
1151 :
1152 : }
1153 :
1154 : return false;
1155 : }
1156 : EXPORT_SYMBOL_GPL(blk_bio_list_merge);
1157 :
1158 0 : bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
1159 : unsigned int nr_segs, struct request **merged_request)
1160 : {
1161 : struct request *rq;
1162 :
1163 0 : switch (elv_merge(q, &rq, bio)) {
1164 : case ELEVATOR_BACK_MERGE:
1165 0 : if (!blk_mq_sched_allow_merge(q, rq, bio))
1166 : return false;
1167 0 : if (bio_attempt_back_merge(rq, bio, nr_segs) != BIO_MERGE_OK)
1168 : return false;
1169 0 : *merged_request = attempt_back_merge(q, rq);
1170 0 : if (!*merged_request)
1171 0 : elv_merged_request(q, rq, ELEVATOR_BACK_MERGE);
1172 : return true;
1173 : case ELEVATOR_FRONT_MERGE:
1174 0 : if (!blk_mq_sched_allow_merge(q, rq, bio))
1175 : return false;
1176 0 : if (bio_attempt_front_merge(rq, bio, nr_segs) != BIO_MERGE_OK)
1177 : return false;
1178 0 : *merged_request = attempt_front_merge(q, rq);
1179 0 : if (!*merged_request)
1180 0 : elv_merged_request(q, rq, ELEVATOR_FRONT_MERGE);
1181 : return true;
1182 : case ELEVATOR_DISCARD_MERGE:
1183 0 : return bio_attempt_discard_merge(q, rq, bio) == BIO_MERGE_OK;
1184 : default:
1185 : return false;
1186 : }
1187 : }
1188 : EXPORT_SYMBOL_GPL(blk_mq_sched_try_merge);
|
