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 
bio_get_first_bvec(struct bio * bio,struct bio_vec * bv)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 
bio_get_last_bvec(struct bio * bio,struct bio_vec * bv)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.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 
bio_will_gap(struct request_queue * q,struct request * prev_rq,struct bio * prev,struct bio * next)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(prev) || !queue_virt_boundary(q))
58 		return false;
59 
60 	/*
61 	 * Don't merge if the 1st bio starts with non-zero offset, otherwise it
62 	 * is quite difficult to respect the sg gap limit.  We work hard to
63 	 * merge a huge number of small single bios in case of mkfs.
64 	 */
65 	if (prev_rq)
66 		bio_get_first_bvec(prev_rq->bio, &pb);
67 	else
68 		bio_get_first_bvec(prev, &pb);
69 	if (pb.bv_offset & queue_virt_boundary(q))
70 		return true;
71 
72 	/*
73 	 * We don't need to worry about the situation that the merged segment
74 	 * ends in unaligned virt boundary:
75 	 *
76 	 * - if 'pb' ends aligned, the merged segment ends aligned
77 	 * - if 'pb' ends unaligned, the next bio must include
78 	 *   one single bvec of 'nb', otherwise the 'nb' can't
79 	 *   merge with 'pb'
80 	 */
81 	bio_get_last_bvec(prev, &pb);
82 	bio_get_first_bvec(next, &nb);
83 	if (biovec_phys_mergeable(q, &pb, &nb))
84 		return false;
85 	return __bvec_gap_to_prev(&q->limits, &pb, nb.bv_offset);
86 }
87 
req_gap_back_merge(struct request * req,struct bio * bio)88 static inline bool req_gap_back_merge(struct request *req, struct bio *bio)
89 {
90 	return bio_will_gap(req->q, req, req->biotail, bio);
91 }
92 
req_gap_front_merge(struct request * req,struct bio * bio)93 static inline bool req_gap_front_merge(struct request *req, struct bio *bio)
94 {
95 	return bio_will_gap(req->q, NULL, bio, req->bio);
96 }
97 
98 /*
99  * The max size one bio can handle is UINT_MAX becasue bvec_iter.bi_size
100  * is defined as 'unsigned int', meantime it has to be aligned to with the
101  * logical block size, which is the minimum accepted unit by hardware.
102  */
bio_allowed_max_sectors(const struct queue_limits * lim)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 
bio_split_discard(struct bio * bio,const struct queue_limits * lim,unsigned * nsegs,struct bio_set * bs)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 	/* Zero-sector (unknown) and one-sector granularities are the same.  */
119 	granularity = max(lim->discard_granularity >> 9, 1U);
120 
121 	max_discard_sectors =
122 		min(lim->max_discard_sectors, bio_allowed_max_sectors(lim));
123 	max_discard_sectors -= max_discard_sectors % granularity;
124 
125 	if (unlikely(!max_discard_sectors)) {
126 		/* XXX: warn */
127 		return NULL;
128 	}
129 
130 	if (bio_sectors(bio) <= max_discard_sectors)
131 		return NULL;
132 
133 	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 	tmp = bio->bi_iter.bi_sector + split_sectors -
140 		((lim->discard_alignment >> 9) % granularity);
141 	tmp = sector_div(tmp, granularity);
142 
143 	if (split_sectors > tmp)
144 		split_sectors -= tmp;
145 
146 	return bio_split(bio, split_sectors, GFP_NOIO, bs);
147 }
148 
bio_split_write_zeroes(struct bio * bio,const struct queue_limits * lim,unsigned * nsegs,struct bio_set * bs)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 	*nsegs = 0;
154 	if (!lim->max_write_zeroes_sectors)
155 		return NULL;
156 	if (bio_sectors(bio) <= lim->max_write_zeroes_sectors)
157 		return NULL;
158 	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  */
get_max_io_size(struct bio * bio,const struct queue_limits * lim)169 static inline unsigned get_max_io_size(struct bio *bio,
170 				       const struct queue_limits *lim)
171 {
172 	unsigned pbs = lim->physical_block_size >> SECTOR_SHIFT;
173 	unsigned lbs = lim->logical_block_size >> SECTOR_SHIFT;
174 	unsigned max_sectors = lim->max_sectors, start, end;
175 
176 	if (lim->chunk_sectors) {
177 		max_sectors = min(max_sectors,
178 			blk_chunk_sectors_left(bio->bi_iter.bi_sector,
179 					       lim->chunk_sectors));
180 	}
181 
182 	start = bio->bi_iter.bi_sector & (pbs - 1);
183 	end = (start + max_sectors) & ~(pbs - 1);
184 	if (end > start)
185 		return end - start;
186 	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  */
get_max_segment_size(const struct queue_limits * lim,struct page * start_page,unsigned long offset)197 static inline unsigned get_max_segment_size(const struct queue_limits *lim,
198 		struct page *start_page, unsigned long offset)
199 {
200 	unsigned long mask = lim->seg_boundary_mask;
201 
202 	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 	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  */
bvec_split_segs(const struct queue_limits * lim,const struct bio_vec * bv,unsigned * nsegs,unsigned * bytes,unsigned max_segs,unsigned max_bytes)231 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 	unsigned max_len = min(max_bytes, UINT_MAX) - *bytes;
236 	unsigned len = min(bv->bv_len, max_len);
237 	unsigned total_len = 0;
238 	unsigned seg_size = 0;
239 
240 	while (len && *nsegs < max_segs) {
241 		seg_size = get_max_segment_size(lim, bv->bv_page,
242 						bv->bv_offset + total_len);
243 		seg_size = min(seg_size, len);
244 
245 		(*nsegs)++;
246 		total_len += seg_size;
247 		len -= seg_size;
248 
249 		if ((bv->bv_offset + total_len) & lim->virt_boundary_mask)
250 			break;
251 	}
252 
253 	*bytes += total_len;
254 
255 	/* tell the caller to split the bvec if it is too big to fit */
256 	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  */
bio_split_rw(struct bio * bio,const struct queue_limits * lim,unsigned * segs,struct bio_set * bs,unsigned max_bytes)279 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 	struct bio_vec bv, bvprv, *bvprvp = NULL;
283 	struct bvec_iter iter;
284 	unsigned nsegs = 0, bytes = 0;
285 
286 	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 		if (bvprvp && bvec_gap_to_prev(lim, bvprvp, bv.bv_offset))
292 			goto split;
293 
294 		if (nsegs < lim->max_segments &&
295 		    bytes + bv.bv_len <= max_bytes &&
296 		    bv.bv_offset + bv.bv_len <= PAGE_SIZE) {
297 			nsegs++;
298 			bytes += bv.bv_len;
299 		} else {
300 			if (bvec_split_segs(lim, &bv, &nsegs, &bytes,
301 					lim->max_segments, max_bytes))
302 				goto split;
303 		}
304 
305 		bvprv = bv;
306 		bvprvp = &bvprv;
307 	}
308 
309 	*segs = nsegs;
310 	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 	if (bio->bi_opf & REQ_NOWAIT) {
317 		bio->bi_status = BLK_STS_AGAIN;
318 		bio_endio(bio);
319 		return ERR_PTR(-EAGAIN);
320 	}
321 
322 	*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 	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 	bio_clear_polled(bio);
337 	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  */
__bio_split_to_limits(struct bio * bio,const struct queue_limits * lim,unsigned int * nr_segs)354 struct bio *__bio_split_to_limits(struct bio *bio,
355 				  const struct queue_limits *lim,
356 				  unsigned int *nr_segs)
357 {
358 	struct bio_set *bs = &bio->bi_bdev->bd_disk->bio_split;
359 	struct bio *split;
360 
361 	switch (bio_op(bio)) {
362 	case REQ_OP_DISCARD:
363 	case REQ_OP_SECURE_ERASE:
364 		split = bio_split_discard(bio, lim, nr_segs, bs);
365 		break;
366 	case REQ_OP_WRITE_ZEROES:
367 		split = bio_split_write_zeroes(bio, lim, nr_segs, bs);
368 		break;
369 	default:
370 		split = bio_split_rw(bio, lim, nr_segs, bs,
371 				get_max_io_size(bio, lim) << SECTOR_SHIFT);
372 		if (IS_ERR(split))
373 			return NULL;
374 		break;
375 	}
376 
377 	if (split) {
378 		/* there isn't chance to merge the split bio */
379 		split->bi_opf |= REQ_NOMERGE;
380 
381 		blkcg_bio_issue_init(split);
382 		bio_chain(split, bio);
383 		trace_block_split(split, bio->bi_iter.bi_sector);
384 		submit_bio_noacct(bio);
385 		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  */
bio_split_to_limits(struct bio * bio)401 struct bio *bio_split_to_limits(struct bio *bio)
402 {
403 	const struct queue_limits *lim = &bdev_get_queue(bio->bi_bdev)->limits;
404 	unsigned int nr_segs;
405 
406 	if (bio_may_exceed_limits(bio, lim))
407 		return __bio_split_to_limits(bio, lim, &nr_segs);
408 	return bio;
409 }
410 EXPORT_SYMBOL(bio_split_to_limits);
411 
blk_recalc_rq_segments(struct request * rq)412 unsigned int blk_recalc_rq_segments(struct request *rq)
413 {
414 	unsigned int nr_phys_segs = 0;
415 	unsigned int bytes = 0;
416 	struct req_iterator iter;
417 	struct bio_vec bv;
418 
419 	if (!rq->bio)
420 		return 0;
421 
422 	switch (bio_op(rq->bio)) {
423 	case REQ_OP_DISCARD:
424 	case REQ_OP_SECURE_ERASE:
425 		if (queue_max_discard_segments(rq->q) > 1) {
426 			struct bio *bio = rq->bio;
427 
428 			for_each_bio(bio)
429 				nr_phys_segs++;
430 			return nr_phys_segs;
431 		}
432 		return 1;
433 	case REQ_OP_WRITE_ZEROES:
434 		return 0;
435 	default:
436 		break;
437 	}
438 
439 	rq_for_each_bvec(bv, rq, iter)
440 		bvec_split_segs(&rq->q->limits, &bv, &nr_phys_segs, &bytes,
441 				UINT_MAX, UINT_MAX);
442 	return nr_phys_segs;
443 }
444 
blk_next_sg(struct scatterlist ** sg,struct scatterlist * sglist)445 static inline struct scatterlist *blk_next_sg(struct scatterlist **sg,
446 		struct scatterlist *sglist)
447 {
448 	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 	sg_unmark_end(*sg);
459 	return sg_next(*sg);
460 }
461 
blk_bvec_map_sg(struct request_queue * q,struct bio_vec * bvec,struct scatterlist * sglist,struct scatterlist ** sg)462 static unsigned blk_bvec_map_sg(struct request_queue *q,
463 		struct bio_vec *bvec, struct scatterlist *sglist,
464 		struct scatterlist **sg)
465 {
466 	unsigned nbytes = bvec->bv_len;
467 	unsigned nsegs = 0, total = 0;
468 
469 	while (nbytes > 0) {
470 		unsigned offset = bvec->bv_offset + total;
471 		unsigned len = min(get_max_segment_size(&q->limits,
472 				   bvec->bv_page, offset), nbytes);
473 		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 		page += (offset >> PAGE_SHIFT);
484 		offset &= ~PAGE_MASK;
485 
486 		*sg = blk_next_sg(sg, sglist);
487 		sg_set_page(*sg, page, len, offset);
488 
489 		total += len;
490 		nbytes -= len;
491 		nsegs++;
492 	}
493 
494 	return nsegs;
495 }
496 
__blk_bvec_map_sg(struct bio_vec bv,struct scatterlist * sglist,struct scatterlist ** sg)497 static inline int __blk_bvec_map_sg(struct bio_vec bv,
498 		struct scatterlist *sglist, struct scatterlist **sg)
499 {
500 	*sg = blk_next_sg(sg, sglist);
501 	sg_set_page(*sg, bv.bv_page, bv.bv_len, bv.bv_offset);
502 	return 1;
503 }
504 
505 /* only try to merge bvecs into one sg if they are from two bios */
506 static inline bool
__blk_segment_map_sg_merge(struct request_queue * q,struct bio_vec * bvec,struct bio_vec * bvprv,struct scatterlist ** sg)507 __blk_segment_map_sg_merge(struct request_queue *q, struct bio_vec *bvec,
508 			   struct bio_vec *bvprv, struct scatterlist **sg)
509 {
510 
511 	int nbytes = bvec->bv_len;
512 
513 	if (!*sg)
514 		return false;
515 
516 	if ((*sg)->length + nbytes > queue_max_segment_size(q))
517 		return false;
518 
519 	if (!biovec_phys_mergeable(q, bvprv, bvec))
520 		return false;
521 
522 	(*sg)->length += nbytes;
523 
524 	return true;
525 }
526 
__blk_bios_map_sg(struct request_queue * q,struct bio * bio,struct scatterlist * sglist,struct scatterlist ** sg)527 static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio,
528 			     struct scatterlist *sglist,
529 			     struct scatterlist **sg)
530 {
531 	struct bio_vec bvec, bvprv = { NULL };
532 	struct bvec_iter iter;
533 	int nsegs = 0;
534 	bool new_bio = false;
535 
536 	for_each_bio(bio) {
537 		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 			if (new_bio &&
544 			    __blk_segment_map_sg_merge(q, &bvec, &bvprv, sg))
545 				goto next_bvec;
546 
547 			if (bvec.bv_offset + bvec.bv_len <= PAGE_SIZE)
548 				nsegs += __blk_bvec_map_sg(bvec, sglist, sg);
549 			else
550 				nsegs += blk_bvec_map_sg(q, &bvec, sglist, sg);
551  next_bvec:
552 			new_bio = false;
553 		}
554 		if (likely(bio->bi_iter.bi_size)) {
555 			bvprv = bvec;
556 			new_bio = true;
557 		}
558 	}
559 
560 	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  */
__blk_rq_map_sg(struct request_queue * q,struct request * rq,struct scatterlist * sglist,struct scatterlist ** last_sg)567 int __blk_rq_map_sg(struct request_queue *q, struct request *rq,
568 		struct scatterlist *sglist, struct scatterlist **last_sg)
569 {
570 	int nsegs = 0;
571 
572 	if (rq->rq_flags & RQF_SPECIAL_PAYLOAD)
573 		nsegs = __blk_bvec_map_sg(rq->special_vec, sglist, last_sg);
574 	else if (rq->bio)
575 		nsegs = __blk_bios_map_sg(q, rq->bio, sglist, last_sg);
576 
577 	if (*last_sg)
578 		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 	WARN_ON(nsegs > blk_rq_nr_phys_segments(rq));
585 
586 	return nsegs;
587 }
588 EXPORT_SYMBOL(__blk_rq_map_sg);
589 
blk_rq_get_max_sectors(struct request * rq,sector_t offset)590 static inline unsigned int blk_rq_get_max_sectors(struct request *rq,
591 						  sector_t offset)
592 {
593 	struct request_queue *q = rq->q;
594 	unsigned int max_sectors;
595 
596 	if (blk_rq_is_passthrough(rq))
597 		return q->limits.max_hw_sectors;
598 
599 	max_sectors = blk_queue_get_max_sectors(q, req_op(rq));
600 	if (!q->limits.chunk_sectors ||
601 	    req_op(rq) == REQ_OP_DISCARD ||
602 	    req_op(rq) == REQ_OP_SECURE_ERASE)
603 		return max_sectors;
604 	return min(max_sectors,
605 		   blk_chunk_sectors_left(offset, q->limits.chunk_sectors));
606 }
607 
ll_new_hw_segment(struct request * req,struct bio * bio,unsigned int nr_phys_segs)608 static inline int ll_new_hw_segment(struct request *req, struct bio *bio,
609 		unsigned int nr_phys_segs)
610 {
611 	if (!blk_cgroup_mergeable(req, bio))
612 		goto no_merge;
613 
614 	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 	if (req_op(req) == REQ_OP_DISCARD)
619 		return 1;
620 
621 	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 	req->nr_phys_segments += nr_phys_segs;
629 	return 1;
630 
631 no_merge:
632 	req_set_nomerge(req->q, req);
633 	return 0;
634 }
635 
ll_back_merge_fn(struct request * req,struct bio * bio,unsigned int nr_segs)636 int ll_back_merge_fn(struct request *req, struct bio *bio, unsigned int nr_segs)
637 {
638 	if (req_gap_back_merge(req, bio))
639 		return 0;
640 	if (blk_integrity_rq(req) &&
641 	    integrity_req_gap_back_merge(req, bio))
642 		return 0;
643 	if (!bio_crypt_ctx_back_mergeable(req, bio))
644 		return 0;
645 	if (blk_rq_sectors(req) + bio_sectors(bio) >
646 	    blk_rq_get_max_sectors(req, blk_rq_pos(req))) {
647 		req_set_nomerge(req->q, req);
648 		return 0;
649 	}
650 
651 	return ll_new_hw_segment(req, bio, nr_segs);
652 }
653 
ll_front_merge_fn(struct request * req,struct bio * bio,unsigned int nr_segs)654 static int ll_front_merge_fn(struct request *req, struct bio *bio,
655 		unsigned int nr_segs)
656 {
657 	if (req_gap_front_merge(req, bio))
658 		return 0;
659 	if (blk_integrity_rq(req) &&
660 	    integrity_req_gap_front_merge(req, bio))
661 		return 0;
662 	if (!bio_crypt_ctx_front_mergeable(req, bio))
663 		return 0;
664 	if (blk_rq_sectors(req) + bio_sectors(bio) >
665 	    blk_rq_get_max_sectors(req, bio->bi_iter.bi_sector)) {
666 		req_set_nomerge(req->q, req);
667 		return 0;
668 	}
669 
670 	return ll_new_hw_segment(req, bio, nr_segs);
671 }
672 
req_attempt_discard_merge(struct request_queue * q,struct request * req,struct request * next)673 static bool req_attempt_discard_merge(struct request_queue *q, struct request *req,
674 		struct request *next)
675 {
676 	unsigned short segments = blk_rq_nr_discard_segments(req);
677 
678 	if (segments >= queue_max_discard_segments(q))
679 		goto no_merge;
680 	if (blk_rq_sectors(req) + bio_sectors(next->bio) >
681 	    blk_rq_get_max_sectors(req, blk_rq_pos(req)))
682 		goto no_merge;
683 
684 	req->nr_phys_segments = segments + blk_rq_nr_discard_segments(next);
685 	return true;
686 no_merge:
687 	req_set_nomerge(q, req);
688 	return false;
689 }
690 
ll_merge_requests_fn(struct request_queue * q,struct request * req,struct request * next)691 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 	if (req_gap_back_merge(req, next->bio))
697 		return 0;
698 
699 	/*
700 	 * Will it become too large?
701 	 */
702 	if ((blk_rq_sectors(req) + blk_rq_sectors(next)) >
703 	    blk_rq_get_max_sectors(req, blk_rq_pos(req)))
704 		return 0;
705 
706 	total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
707 	if (total_phys_segments > blk_rq_get_max_segments(req))
708 		return 0;
709 
710 	if (!blk_cgroup_mergeable(req, next->bio))
711 		return 0;
712 
713 	if (blk_integrity_merge_rq(q, req, next) == false)
714 		return 0;
715 
716 	if (!bio_crypt_ctx_merge_rq(req, next))
717 		return 0;
718 
719 	/* Merge is OK... */
720 	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  */
blk_rq_set_mixed_merge(struct request * rq)733 void blk_rq_set_mixed_merge(struct request *rq)
734 {
735 	blk_opf_t ff = rq->cmd_flags & REQ_FAILFAST_MASK;
736 	struct bio *bio;
737 
738 	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 	for (bio = rq->bio; bio; bio = bio->bi_next) {
747 		WARN_ON_ONCE((bio->bi_opf & REQ_FAILFAST_MASK) &&
748 			     (bio->bi_opf & REQ_FAILFAST_MASK) != ff);
749 		bio->bi_opf |= ff;
750 	}
751 	rq->rq_flags |= RQF_MIXED_MERGE;
752 }
753 
bio_failfast(const struct bio * bio)754 static inline blk_opf_t bio_failfast(const struct bio *bio)
755 {
756 	if (bio->bi_opf & REQ_RAHEAD)
757 		return REQ_FAILFAST_MASK;
758 
759 	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  */
blk_update_mixed_merge(struct request * req,struct bio * bio,bool front_merge)767 static inline void blk_update_mixed_merge(struct request *req,
768 		struct bio *bio, bool front_merge)
769 {
770 	if (req->rq_flags & RQF_MIXED_MERGE) {
771 		if (bio->bi_opf & REQ_RAHEAD)
772 			bio->bi_opf |= REQ_FAILFAST_MASK;
773 
774 		if (front_merge) {
775 			req->cmd_flags &= ~REQ_FAILFAST_MASK;
776 			req->cmd_flags |= bio->bi_opf & REQ_FAILFAST_MASK;
777 		}
778 	}
779 }
780 
blk_account_io_merge_request(struct request * req)781 static void blk_account_io_merge_request(struct request *req)
782 {
783 	if (blk_do_io_stat(req)) {
784 		part_stat_lock();
785 		part_stat_inc(req->part, merges[op_stat_group(req_op(req))]);
786 		part_stat_unlock();
787 	}
788 }
789 
blk_try_req_merge(struct request * req,struct request * next)790 static enum elv_merge blk_try_req_merge(struct request *req,
791 					struct request *next)
792 {
793 	if (blk_discard_mergable(req))
794 		return ELEVATOR_DISCARD_MERGE;
795 	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  */
attempt_merge(struct request_queue * q,struct request * req,struct request * next)805 static struct request *attempt_merge(struct request_queue *q,
806 				     struct request *req, struct request *next)
807 {
808 	if (!rq_mergeable(req) || !rq_mergeable(next))
809 		return NULL;
810 
811 	if (req_op(req) != req_op(next))
812 		return NULL;
813 
814 	if (rq_data_dir(req) != rq_data_dir(next))
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(req);
851 		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 	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(next);
866 
867 	if (!blk_discard_mergable(req))
868 		elv_merge_requests(q, req, next);
869 
870 	blk_crypto_rq_put_keyslot(next);
871 
872 	/*
873 	 * 'next' is going away, so update stats accordingly
874 	 */
875 	blk_account_io_merge_request(next);
876 
877 	trace_block_rq_merge(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 
attempt_back_merge(struct request_queue * q,struct request * rq)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, rq, next);
894 
895 	return NULL;
896 }
897 
attempt_front_merge(struct request_queue * q,struct request * rq)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, prev, 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  */
blk_attempt_req_merge(struct request_queue * q,struct request * rq,struct request * next)914 bool blk_attempt_req_merge(struct request_queue *q, struct request *rq,
915 			   struct request *next)
916 {
917 	return attempt_merge(q, rq, next);
918 }
919 
blk_rq_merge_ok(struct request * rq,struct bio * bio)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(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 	if (rq->ioprio != bio_prio(bio))
945 		return false;
946 
947 	return true;
948 }
949 
blk_try_merge(struct request * rq,struct bio * bio)950 enum elv_merge blk_try_merge(struct request *rq, struct bio *bio)
951 {
952 	if (blk_discard_mergable(rq))
953 		return ELEVATOR_DISCARD_MERGE;
954 	else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector)
955 		return ELEVATOR_BACK_MERGE;
956 	else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector)
957 		return ELEVATOR_FRONT_MERGE;
958 	return ELEVATOR_NO_MERGE;
959 }
960 
blk_account_io_merge_bio(struct request * req)961 static void blk_account_io_merge_bio(struct request *req)
962 {
963 	if (!blk_do_io_stat(req))
964 		return;
965 
966 	part_stat_lock();
967 	part_stat_inc(req->part, merges[op_stat_group(req_op(req))]);
968 	part_stat_unlock();
969 }
970 
971 enum bio_merge_status {
972 	BIO_MERGE_OK,
973 	BIO_MERGE_NONE,
974 	BIO_MERGE_FAILED,
975 };
976 
bio_attempt_back_merge(struct request * req,struct bio * bio,unsigned int nr_segs)977 static enum bio_merge_status bio_attempt_back_merge(struct request *req,
978 		struct bio *bio, unsigned int nr_segs)
979 {
980 	const blk_opf_t ff = bio_failfast(bio);
981 
982 	if (!ll_back_merge_fn(req, bio, nr_segs))
983 		return BIO_MERGE_FAILED;
984 
985 	trace_block_bio_backmerge(bio);
986 	rq_qos_merge(req->q, req, bio);
987 
988 	if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
989 		blk_rq_set_mixed_merge(req);
990 
991 	blk_update_mixed_merge(req, bio, false);
992 
993 	req->biotail->bi_next = bio;
994 	req->biotail = bio;
995 	req->__data_len += bio->bi_iter.bi_size;
996 
997 	bio_crypt_free_ctx(bio);
998 
999 	blk_account_io_merge_bio(req);
1000 	return BIO_MERGE_OK;
1001 }
1002 
bio_attempt_front_merge(struct request * req,struct bio * bio,unsigned int nr_segs)1003 static enum bio_merge_status bio_attempt_front_merge(struct request *req,
1004 		struct bio *bio, unsigned int nr_segs)
1005 {
1006 	const blk_opf_t ff = bio_failfast(bio);
1007 
1008 	if (!ll_front_merge_fn(req, bio, nr_segs))
1009 		return BIO_MERGE_FAILED;
1010 
1011 	trace_block_bio_frontmerge(bio);
1012 	rq_qos_merge(req->q, req, bio);
1013 
1014 	if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
1015 		blk_rq_set_mixed_merge(req);
1016 
1017 	blk_update_mixed_merge(req, bio, true);
1018 
1019 	bio->bi_next = req->bio;
1020 	req->bio = bio;
1021 
1022 	req->__sector = bio->bi_iter.bi_sector;
1023 	req->__data_len += bio->bi_iter.bi_size;
1024 
1025 	bio_crypt_do_front_merge(req, bio);
1026 
1027 	blk_account_io_merge_bio(req);
1028 	return BIO_MERGE_OK;
1029 }
1030 
bio_attempt_discard_merge(struct request_queue * q,struct request * req,struct bio * bio)1031 static enum bio_merge_status bio_attempt_discard_merge(struct request_queue *q,
1032 		struct request *req, struct bio *bio)
1033 {
1034 	unsigned short segments = blk_rq_nr_discard_segments(req);
1035 
1036 	if (segments >= queue_max_discard_segments(q))
1037 		goto no_merge;
1038 	if (blk_rq_sectors(req) + bio_sectors(bio) >
1039 	    blk_rq_get_max_sectors(req, blk_rq_pos(req)))
1040 		goto no_merge;
1041 
1042 	rq_qos_merge(q, req, bio);
1043 
1044 	req->biotail->bi_next = bio;
1045 	req->biotail = bio;
1046 	req->__data_len += bio->bi_iter.bi_size;
1047 	req->nr_phys_segments = segments + 1;
1048 
1049 	blk_account_io_merge_bio(req);
1050 	return BIO_MERGE_OK;
1051 no_merge:
1052 	req_set_nomerge(q, req);
1053 	return BIO_MERGE_FAILED;
1054 }
1055 
blk_attempt_bio_merge(struct request_queue * q,struct request * rq,struct bio * bio,unsigned int nr_segs,bool sched_allow_merge)1056 static enum bio_merge_status blk_attempt_bio_merge(struct request_queue *q,
1057 						   struct request *rq,
1058 						   struct bio *bio,
1059 						   unsigned int nr_segs,
1060 						   bool sched_allow_merge)
1061 {
1062 	if (!blk_rq_merge_ok(rq, bio))
1063 		return BIO_MERGE_NONE;
1064 
1065 	switch (blk_try_merge(rq, bio)) {
1066 	case ELEVATOR_BACK_MERGE:
1067 		if (!sched_allow_merge || blk_mq_sched_allow_merge(q, rq, bio))
1068 			return bio_attempt_back_merge(rq, bio, nr_segs);
1069 		break;
1070 	case ELEVATOR_FRONT_MERGE:
1071 		if (!sched_allow_merge || blk_mq_sched_allow_merge(q, rq, bio))
1072 			return bio_attempt_front_merge(rq, bio, nr_segs);
1073 		break;
1074 	case ELEVATOR_DISCARD_MERGE:
1075 		return bio_attempt_discard_merge(q, rq, bio);
1076 	default:
1077 		return BIO_MERGE_NONE;
1078 	}
1079 
1080 	return BIO_MERGE_FAILED;
1081 }
1082 
1083 /**
1084  * blk_attempt_plug_merge - try to merge with %current's plugged list
1085  * @q: request_queue new bio is being queued at
1086  * @bio: new bio being queued
1087  * @nr_segs: number of segments in @bio
1088  * from the passed in @q already in the plug list
1089  *
1090  * Determine whether @bio being queued on @q can be merged with the previous
1091  * request on %current's plugged list.  Returns %true if merge was successful,
1092  * otherwise %false.
1093  *
1094  * Plugging coalesces IOs from the same issuer for the same purpose without
1095  * going through @q->queue_lock.  As such it's more of an issuing mechanism
1096  * than scheduling, and the request, while may have elvpriv data, is not
1097  * added on the elevator at this point.  In addition, we don't have
1098  * reliable access to the elevator outside queue lock.  Only check basic
1099  * merging parameters without querying the elevator.
1100  *
1101  * Caller must ensure !blk_queue_nomerges(q) beforehand.
1102  */
blk_attempt_plug_merge(struct request_queue * q,struct bio * bio,unsigned int nr_segs)1103 bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
1104 		unsigned int nr_segs)
1105 {
1106 	struct blk_plug *plug;
1107 	struct request *rq;
1108 
1109 	plug = blk_mq_plug(bio);
1110 	if (!plug || rq_list_empty(plug->mq_list))
1111 		return false;
1112 
1113 	rq_list_for_each(&plug->mq_list, rq) {
1114 		if (rq->q == q) {
1115 			if (blk_attempt_bio_merge(q, rq, bio, nr_segs, false) ==
1116 			    BIO_MERGE_OK)
1117 				return true;
1118 			break;
1119 		}
1120 
1121 		/*
1122 		 * Only keep iterating plug list for merges if we have multiple
1123 		 * queues
1124 		 */
1125 		if (!plug->multiple_queues)
1126 			break;
1127 	}
1128 	return false;
1129 }
1130 
1131 /*
1132  * Iterate list of requests and see if we can merge this bio with any
1133  * of them.
1134  */
blk_bio_list_merge(struct request_queue * q,struct list_head * list,struct bio * bio,unsigned int nr_segs)1135 bool blk_bio_list_merge(struct request_queue *q, struct list_head *list,
1136 			struct bio *bio, unsigned int nr_segs)
1137 {
1138 	struct request *rq;
1139 	int checked = 8;
1140 
1141 	list_for_each_entry_reverse(rq, list, queuelist) {
1142 		if (!checked--)
1143 			break;
1144 
1145 		switch (blk_attempt_bio_merge(q, rq, bio, nr_segs, true)) {
1146 		case BIO_MERGE_NONE:
1147 			continue;
1148 		case BIO_MERGE_OK:
1149 			return true;
1150 		case BIO_MERGE_FAILED:
1151 			return false;
1152 		}
1153 
1154 	}
1155 
1156 	return false;
1157 }
1158 EXPORT_SYMBOL_GPL(blk_bio_list_merge);
1159 
blk_mq_sched_try_merge(struct request_queue * q,struct bio * bio,unsigned int nr_segs,struct request ** merged_request)1160 bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
1161 		unsigned int nr_segs, struct request **merged_request)
1162 {
1163 	struct request *rq;
1164 
1165 	switch (elv_merge(q, &rq, bio)) {
1166 	case ELEVATOR_BACK_MERGE:
1167 		if (!blk_mq_sched_allow_merge(q, rq, bio))
1168 			return false;
1169 		if (bio_attempt_back_merge(rq, bio, nr_segs) != BIO_MERGE_OK)
1170 			return false;
1171 		*merged_request = attempt_back_merge(q, rq);
1172 		if (!*merged_request)
1173 			elv_merged_request(q, rq, ELEVATOR_BACK_MERGE);
1174 		return true;
1175 	case ELEVATOR_FRONT_MERGE:
1176 		if (!blk_mq_sched_allow_merge(q, rq, bio))
1177 			return false;
1178 		if (bio_attempt_front_merge(rq, bio, nr_segs) != BIO_MERGE_OK)
1179 			return false;
1180 		*merged_request = attempt_front_merge(q, rq);
1181 		if (!*merged_request)
1182 			elv_merged_request(q, rq, ELEVATOR_FRONT_MERGE);
1183 		return true;
1184 	case ELEVATOR_DISCARD_MERGE:
1185 		return bio_attempt_discard_merge(q, rq, bio) == BIO_MERGE_OK;
1186 	default:
1187 		return false;
1188 	}
1189 }
1190 EXPORT_SYMBOL_GPL(blk_mq_sched_try_merge);
1191