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Greg Kroah-Hartmanb2441312017-11-01 15:07:57 +01001// SPDX-License-Identifier: GPL-2.0
Jens Axboed6d48192008-01-29 14:04:06 +01002/*
3 * Functions related to segment and merge handling
4 */
5#include <linux/kernel.h>
6#include <linux/module.h>
7#include <linux/bio.h>
8#include <linux/blkdev.h>
9#include <linux/scatterlist.h>
10
Mike Krinkincda22642015-12-03 17:32:30 +030011#include <trace/events/block.h>
12
Jens Axboed6d48192008-01-29 14:04:06 +010013#include "blk.h"
14
Kent Overstreet54efd502015-04-23 22:37:18 -070015static struct bio *blk_bio_discard_split(struct request_queue *q,
16 struct bio *bio,
Ming Leibdced432015-10-20 23:13:52 +080017 struct bio_set *bs,
18 unsigned *nsegs)
Kent Overstreet54efd502015-04-23 22:37:18 -070019{
20 unsigned int max_discard_sectors, granularity;
21 int alignment;
22 sector_t tmp;
23 unsigned split_sectors;
24
Ming Leibdced432015-10-20 23:13:52 +080025 *nsegs = 1;
26
Kent Overstreet54efd502015-04-23 22:37:18 -070027 /* Zero-sector (unknown) and one-sector granularities are the same. */
28 granularity = max(q->limits.discard_granularity >> 9, 1U);
29
30 max_discard_sectors = min(q->limits.max_discard_sectors, UINT_MAX >> 9);
31 max_discard_sectors -= max_discard_sectors % granularity;
32
33 if (unlikely(!max_discard_sectors)) {
34 /* XXX: warn */
35 return NULL;
36 }
37
38 if (bio_sectors(bio) <= max_discard_sectors)
39 return NULL;
40
41 split_sectors = max_discard_sectors;
42
43 /*
44 * If the next starting sector would be misaligned, stop the discard at
45 * the previous aligned sector.
46 */
47 alignment = (q->limits.discard_alignment >> 9) % granularity;
48
49 tmp = bio->bi_iter.bi_sector + split_sectors - alignment;
50 tmp = sector_div(tmp, granularity);
51
52 if (split_sectors > tmp)
53 split_sectors -= tmp;
54
55 return bio_split(bio, split_sectors, GFP_NOIO, bs);
56}
57
Christoph Hellwig885fa132017-04-05 19:21:01 +020058static struct bio *blk_bio_write_zeroes_split(struct request_queue *q,
59 struct bio *bio, struct bio_set *bs, unsigned *nsegs)
60{
61 *nsegs = 1;
62
63 if (!q->limits.max_write_zeroes_sectors)
64 return NULL;
65
66 if (bio_sectors(bio) <= q->limits.max_write_zeroes_sectors)
67 return NULL;
68
69 return bio_split(bio, q->limits.max_write_zeroes_sectors, GFP_NOIO, bs);
70}
71
Kent Overstreet54efd502015-04-23 22:37:18 -070072static struct bio *blk_bio_write_same_split(struct request_queue *q,
73 struct bio *bio,
Ming Leibdced432015-10-20 23:13:52 +080074 struct bio_set *bs,
75 unsigned *nsegs)
Kent Overstreet54efd502015-04-23 22:37:18 -070076{
Ming Leibdced432015-10-20 23:13:52 +080077 *nsegs = 1;
78
Kent Overstreet54efd502015-04-23 22:37:18 -070079 if (!q->limits.max_write_same_sectors)
80 return NULL;
81
82 if (bio_sectors(bio) <= q->limits.max_write_same_sectors)
83 return NULL;
84
85 return bio_split(bio, q->limits.max_write_same_sectors, GFP_NOIO, bs);
86}
87
Ming Leid0e5fbb2016-01-23 08:05:33 +080088static inline unsigned get_max_io_size(struct request_queue *q,
89 struct bio *bio)
90{
91 unsigned sectors = blk_max_size_offset(q, bio->bi_iter.bi_sector);
92 unsigned mask = queue_logical_block_size(q) - 1;
93
94 /* aligned to logical block size */
95 sectors &= ~(mask >> 9);
96
97 return sectors;
98}
99
Kent Overstreet54efd502015-04-23 22:37:18 -0700100static struct bio *blk_bio_segment_split(struct request_queue *q,
101 struct bio *bio,
Ming Leibdced432015-10-20 23:13:52 +0800102 struct bio_set *bs,
103 unsigned *segs)
Kent Overstreet54efd502015-04-23 22:37:18 -0700104{
Jens Axboe5014c312015-09-02 16:46:02 -0600105 struct bio_vec bv, bvprv, *bvprvp = NULL;
Kent Overstreet54efd502015-04-23 22:37:18 -0700106 struct bvec_iter iter;
Kent Overstreet8ae12662015-04-27 23:48:34 -0700107 unsigned seg_size = 0, nsegs = 0, sectors = 0;
Ming Lei02e70742015-11-24 10:35:30 +0800108 unsigned front_seg_size = bio->bi_seg_front_size;
109 bool do_split = true;
110 struct bio *new = NULL;
Ming Leid0e5fbb2016-01-23 08:05:33 +0800111 const unsigned max_sectors = get_max_io_size(q, bio);
Kent Overstreet54efd502015-04-23 22:37:18 -0700112
Kent Overstreet54efd502015-04-23 22:37:18 -0700113 bio_for_each_segment(bv, bio, iter) {
Kent Overstreet54efd502015-04-23 22:37:18 -0700114 /*
115 * If the queue doesn't support SG gaps and adding this
116 * offset would create a gap, disallow it.
117 */
Jens Axboe5014c312015-09-02 16:46:02 -0600118 if (bvprvp && bvec_gap_to_prev(q, bvprvp, bv.bv_offset))
Kent Overstreet54efd502015-04-23 22:37:18 -0700119 goto split;
120
Ming Leid0e5fbb2016-01-23 08:05:33 +0800121 if (sectors + (bv.bv_len >> 9) > max_sectors) {
Keith Busche36f6202016-01-12 15:08:39 -0700122 /*
123 * Consider this a new segment if we're splitting in
124 * the middle of this vector.
125 */
126 if (nsegs < queue_max_segments(q) &&
Ming Leid0e5fbb2016-01-23 08:05:33 +0800127 sectors < max_sectors) {
Keith Busche36f6202016-01-12 15:08:39 -0700128 nsegs++;
Ming Leid0e5fbb2016-01-23 08:05:33 +0800129 sectors = max_sectors;
Keith Busche36f6202016-01-12 15:08:39 -0700130 }
Ming Leicf8c0c62017-12-18 20:22:16 +0800131 goto split;
Keith Busche36f6202016-01-12 15:08:39 -0700132 }
133
Jens Axboe5014c312015-09-02 16:46:02 -0600134 if (bvprvp && blk_queue_cluster(q)) {
Ming Leib4b6cb62018-01-10 10:51:29 +0800135 if (seg_size + bv.bv_len > queue_max_segment_size(q))
136 goto new_segment;
Jens Axboe5014c312015-09-02 16:46:02 -0600137 if (!BIOVEC_PHYS_MERGEABLE(bvprvp, &bv))
Kent Overstreet54efd502015-04-23 22:37:18 -0700138 goto new_segment;
Jens Axboe5014c312015-09-02 16:46:02 -0600139 if (!BIOVEC_SEG_BOUNDARY(q, bvprvp, &bv))
Kent Overstreet54efd502015-04-23 22:37:18 -0700140 goto new_segment;
141
142 seg_size += bv.bv_len;
143 bvprv = bv;
Ming Lei578270b2015-11-24 10:35:29 +0800144 bvprvp = &bvprv;
Ming Lei52cc6ee2015-09-17 09:58:38 -0600145 sectors += bv.bv_len >> 9;
Ming Leia88d32a2015-11-30 16:05:49 +0800146
Kent Overstreet54efd502015-04-23 22:37:18 -0700147 continue;
148 }
149new_segment:
150 if (nsegs == queue_max_segments(q))
151 goto split;
152
Ming Lei6a501bf2017-12-18 20:22:14 +0800153 if (nsegs == 1 && seg_size > front_seg_size)
154 front_seg_size = seg_size;
155
Kent Overstreet54efd502015-04-23 22:37:18 -0700156 nsegs++;
157 bvprv = bv;
Ming Lei578270b2015-11-24 10:35:29 +0800158 bvprvp = &bvprv;
Kent Overstreet54efd502015-04-23 22:37:18 -0700159 seg_size = bv.bv_len;
Ming Lei52cc6ee2015-09-17 09:58:38 -0600160 sectors += bv.bv_len >> 9;
Ming Lei02e70742015-11-24 10:35:30 +0800161
Kent Overstreet54efd502015-04-23 22:37:18 -0700162 }
163
Ming Lei02e70742015-11-24 10:35:30 +0800164 do_split = false;
Kent Overstreet54efd502015-04-23 22:37:18 -0700165split:
Ming Leibdced432015-10-20 23:13:52 +0800166 *segs = nsegs;
Ming Lei02e70742015-11-24 10:35:30 +0800167
168 if (do_split) {
169 new = bio_split(bio, sectors, GFP_NOIO, bs);
170 if (new)
171 bio = new;
172 }
173
Ming Lei6a501bf2017-12-18 20:22:14 +0800174 if (nsegs == 1 && seg_size > front_seg_size)
175 front_seg_size = seg_size;
Ming Lei02e70742015-11-24 10:35:30 +0800176 bio->bi_seg_front_size = front_seg_size;
177 if (seg_size > bio->bi_seg_back_size)
178 bio->bi_seg_back_size = seg_size;
179
180 return do_split ? new : NULL;
Kent Overstreet54efd502015-04-23 22:37:18 -0700181}
182
NeilBrownaf67c312017-06-18 14:38:57 +1000183void blk_queue_split(struct request_queue *q, struct bio **bio)
Kent Overstreet54efd502015-04-23 22:37:18 -0700184{
Ming Leibdced432015-10-20 23:13:52 +0800185 struct bio *split, *res;
186 unsigned nsegs;
Kent Overstreet54efd502015-04-23 22:37:18 -0700187
Adrian Hunter7afafc82016-08-16 10:59:35 +0300188 switch (bio_op(*bio)) {
189 case REQ_OP_DISCARD:
190 case REQ_OP_SECURE_ERASE:
NeilBrownaf67c312017-06-18 14:38:57 +1000191 split = blk_bio_discard_split(q, *bio, q->bio_split, &nsegs);
Adrian Hunter7afafc82016-08-16 10:59:35 +0300192 break;
Chaitanya Kulkarnia6f07882016-11-30 12:28:59 -0800193 case REQ_OP_WRITE_ZEROES:
NeilBrownaf67c312017-06-18 14:38:57 +1000194 split = blk_bio_write_zeroes_split(q, *bio, q->bio_split, &nsegs);
Chaitanya Kulkarnia6f07882016-11-30 12:28:59 -0800195 break;
Adrian Hunter7afafc82016-08-16 10:59:35 +0300196 case REQ_OP_WRITE_SAME:
NeilBrownaf67c312017-06-18 14:38:57 +1000197 split = blk_bio_write_same_split(q, *bio, q->bio_split, &nsegs);
Adrian Hunter7afafc82016-08-16 10:59:35 +0300198 break;
199 default:
Ming Leibdced432015-10-20 23:13:52 +0800200 split = blk_bio_segment_split(q, *bio, q->bio_split, &nsegs);
Adrian Hunter7afafc82016-08-16 10:59:35 +0300201 break;
202 }
Ming Leibdced432015-10-20 23:13:52 +0800203
204 /* physical segments can be figured out during splitting */
205 res = split ? split : *bio;
206 res->bi_phys_segments = nsegs;
207 bio_set_flag(res, BIO_SEG_VALID);
Kent Overstreet54efd502015-04-23 22:37:18 -0700208
209 if (split) {
Ming Lei6ac45ae2015-10-20 23:13:53 +0800210 /* there isn't chance to merge the splitted bio */
Jens Axboe1eff9d32016-08-05 15:35:16 -0600211 split->bi_opf |= REQ_NOMERGE;
Ming Lei6ac45ae2015-10-20 23:13:53 +0800212
Kent Overstreet54efd502015-04-23 22:37:18 -0700213 bio_chain(split, *bio);
Mike Krinkincda22642015-12-03 17:32:30 +0300214 trace_block_split(q, split, (*bio)->bi_iter.bi_sector);
Kent Overstreet54efd502015-04-23 22:37:18 -0700215 generic_make_request(*bio);
216 *bio = split;
217 }
218}
219EXPORT_SYMBOL(blk_queue_split);
220
Jens Axboe1e428072009-02-23 09:03:10 +0100221static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
Ming Lei07388542014-09-02 23:02:59 +0800222 struct bio *bio,
223 bool no_sg_merge)
Jens Axboed6d48192008-01-29 14:04:06 +0100224{
Kent Overstreet79886132013-11-23 17:19:00 -0800225 struct bio_vec bv, bvprv = { NULL };
Kent Overstreet54efd502015-04-23 22:37:18 -0700226 int cluster, prev = 0;
Jens Axboe1e428072009-02-23 09:03:10 +0100227 unsigned int seg_size, nr_phys_segs;
Jens Axboe59247ea2009-03-06 08:55:24 +0100228 struct bio *fbio, *bbio;
Kent Overstreet79886132013-11-23 17:19:00 -0800229 struct bvec_iter iter;
Jens Axboed6d48192008-01-29 14:04:06 +0100230
Jens Axboe1e428072009-02-23 09:03:10 +0100231 if (!bio)
232 return 0;
Jens Axboed6d48192008-01-29 14:04:06 +0100233
Chaitanya Kulkarnia6f07882016-11-30 12:28:59 -0800234 switch (bio_op(bio)) {
235 case REQ_OP_DISCARD:
236 case REQ_OP_SECURE_ERASE:
Chaitanya Kulkarnia6f07882016-11-30 12:28:59 -0800237 case REQ_OP_WRITE_ZEROES:
Christoph Hellwigf9d03f92016-12-08 15:20:32 -0700238 return 0;
239 case REQ_OP_WRITE_SAME:
Kent Overstreet5cb88502014-02-07 13:53:46 -0700240 return 1;
Chaitanya Kulkarnia6f07882016-11-30 12:28:59 -0800241 }
Kent Overstreet5cb88502014-02-07 13:53:46 -0700242
Jens Axboe1e428072009-02-23 09:03:10 +0100243 fbio = bio;
Martin K. Petersene692cb62010-12-01 19:41:49 +0100244 cluster = blk_queue_cluster(q);
Mikulas Patocka5df97b92008-08-15 10:20:02 +0200245 seg_size = 0;
Andi Kleen2c8919d2010-06-21 11:02:47 +0200246 nr_phys_segs = 0;
Jens Axboe1e428072009-02-23 09:03:10 +0100247 for_each_bio(bio) {
Kent Overstreet79886132013-11-23 17:19:00 -0800248 bio_for_each_segment(bv, bio, iter) {
Jens Axboe1e428072009-02-23 09:03:10 +0100249 /*
Jens Axboe05f1dd52014-05-29 09:53:32 -0600250 * If SG merging is disabled, each bio vector is
251 * a segment
252 */
253 if (no_sg_merge)
254 goto new_segment;
255
Kent Overstreet54efd502015-04-23 22:37:18 -0700256 if (prev && cluster) {
Kent Overstreet79886132013-11-23 17:19:00 -0800257 if (seg_size + bv.bv_len
Martin K. Petersenae03bf62009-05-22 17:17:50 -0400258 > queue_max_segment_size(q))
Jens Axboe1e428072009-02-23 09:03:10 +0100259 goto new_segment;
Kent Overstreet79886132013-11-23 17:19:00 -0800260 if (!BIOVEC_PHYS_MERGEABLE(&bvprv, &bv))
Jens Axboe1e428072009-02-23 09:03:10 +0100261 goto new_segment;
Kent Overstreet79886132013-11-23 17:19:00 -0800262 if (!BIOVEC_SEG_BOUNDARY(q, &bvprv, &bv))
Jens Axboe1e428072009-02-23 09:03:10 +0100263 goto new_segment;
Jens Axboed6d48192008-01-29 14:04:06 +0100264
Kent Overstreet79886132013-11-23 17:19:00 -0800265 seg_size += bv.bv_len;
Jens Axboe1e428072009-02-23 09:03:10 +0100266 bvprv = bv;
267 continue;
268 }
Jens Axboed6d48192008-01-29 14:04:06 +0100269new_segment:
Jens Axboe1e428072009-02-23 09:03:10 +0100270 if (nr_phys_segs == 1 && seg_size >
271 fbio->bi_seg_front_size)
272 fbio->bi_seg_front_size = seg_size;
FUJITA Tomonori86771422008-10-13 14:19:05 +0200273
Jens Axboe1e428072009-02-23 09:03:10 +0100274 nr_phys_segs++;
275 bvprv = bv;
Kent Overstreet54efd502015-04-23 22:37:18 -0700276 prev = 1;
Kent Overstreet79886132013-11-23 17:19:00 -0800277 seg_size = bv.bv_len;
Jens Axboe1e428072009-02-23 09:03:10 +0100278 }
Jens Axboe59247ea2009-03-06 08:55:24 +0100279 bbio = bio;
Jens Axboed6d48192008-01-29 14:04:06 +0100280 }
281
Jens Axboe59247ea2009-03-06 08:55:24 +0100282 if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size)
283 fbio->bi_seg_front_size = seg_size;
284 if (seg_size > bbio->bi_seg_back_size)
285 bbio->bi_seg_back_size = seg_size;
Jens Axboe1e428072009-02-23 09:03:10 +0100286
287 return nr_phys_segs;
288}
289
290void blk_recalc_rq_segments(struct request *rq)
291{
Ming Lei07388542014-09-02 23:02:59 +0800292 bool no_sg_merge = !!test_bit(QUEUE_FLAG_NO_SG_MERGE,
293 &rq->q->queue_flags);
294
295 rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio,
296 no_sg_merge);
Jens Axboed6d48192008-01-29 14:04:06 +0100297}
298
299void blk_recount_segments(struct request_queue *q, struct bio *bio)
300{
Ming Lei7f60dca2014-11-12 00:15:41 +0800301 unsigned short seg_cnt;
Ming Lei764f6122014-10-09 23:17:35 +0800302
Ming Lei7f60dca2014-11-12 00:15:41 +0800303 /* estimate segment number by bi_vcnt for non-cloned bio */
304 if (bio_flagged(bio, BIO_CLONED))
305 seg_cnt = bio_segments(bio);
306 else
307 seg_cnt = bio->bi_vcnt;
308
309 if (test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags) &&
310 (seg_cnt < queue_max_segments(q)))
311 bio->bi_phys_segments = seg_cnt;
Jens Axboe05f1dd52014-05-29 09:53:32 -0600312 else {
313 struct bio *nxt = bio->bi_next;
Jens Axboe1e428072009-02-23 09:03:10 +0100314
Jens Axboe05f1dd52014-05-29 09:53:32 -0600315 bio->bi_next = NULL;
Ming Lei7f60dca2014-11-12 00:15:41 +0800316 bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio, false);
Jens Axboe05f1dd52014-05-29 09:53:32 -0600317 bio->bi_next = nxt;
318 }
319
Jens Axboeb7c44ed2015-07-24 12:37:59 -0600320 bio_set_flag(bio, BIO_SEG_VALID);
Jens Axboed6d48192008-01-29 14:04:06 +0100321}
322EXPORT_SYMBOL(blk_recount_segments);
323
324static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
325 struct bio *nxt)
326{
Kent Overstreet2b8221e2013-12-03 14:29:09 -0700327 struct bio_vec end_bv = { NULL }, nxt_bv;
Kent Overstreetf619d252013-08-07 14:30:33 -0700328
Martin K. Petersene692cb62010-12-01 19:41:49 +0100329 if (!blk_queue_cluster(q))
Jens Axboed6d48192008-01-29 14:04:06 +0100330 return 0;
331
FUJITA Tomonori86771422008-10-13 14:19:05 +0200332 if (bio->bi_seg_back_size + nxt->bi_seg_front_size >
Martin K. Petersenae03bf62009-05-22 17:17:50 -0400333 queue_max_segment_size(q))
Jens Axboed6d48192008-01-29 14:04:06 +0100334 return 0;
335
David Woodhousee17fc0a2008-08-09 16:42:20 +0100336 if (!bio_has_data(bio))
337 return 1;
338
Ming Leie8270912016-02-26 23:40:53 +0800339 bio_get_last_bvec(bio, &end_bv);
340 bio_get_first_bvec(nxt, &nxt_bv);
Kent Overstreetf619d252013-08-07 14:30:33 -0700341
342 if (!BIOVEC_PHYS_MERGEABLE(&end_bv, &nxt_bv))
David Woodhousee17fc0a2008-08-09 16:42:20 +0100343 return 0;
344
Jens Axboed6d48192008-01-29 14:04:06 +0100345 /*
David Woodhousee17fc0a2008-08-09 16:42:20 +0100346 * bio and nxt are contiguous in memory; check if the queue allows
Jens Axboed6d48192008-01-29 14:04:06 +0100347 * these two to be merged into one
348 */
Kent Overstreetf619d252013-08-07 14:30:33 -0700349 if (BIOVEC_SEG_BOUNDARY(q, &end_bv, &nxt_bv))
Jens Axboed6d48192008-01-29 14:04:06 +0100350 return 1;
351
352 return 0;
353}
354
Kent Overstreet79886132013-11-23 17:19:00 -0800355static inline void
Asias He963ab9e2012-08-02 23:42:03 +0200356__blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec,
Kent Overstreet79886132013-11-23 17:19:00 -0800357 struct scatterlist *sglist, struct bio_vec *bvprv,
Asias He963ab9e2012-08-02 23:42:03 +0200358 struct scatterlist **sg, int *nsegs, int *cluster)
359{
360
361 int nbytes = bvec->bv_len;
362
Kent Overstreet79886132013-11-23 17:19:00 -0800363 if (*sg && *cluster) {
Ming Leib4b6cb62018-01-10 10:51:29 +0800364 if ((*sg)->length + nbytes > queue_max_segment_size(q))
365 goto new_segment;
366
Kent Overstreet79886132013-11-23 17:19:00 -0800367 if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
Asias He963ab9e2012-08-02 23:42:03 +0200368 goto new_segment;
Kent Overstreet79886132013-11-23 17:19:00 -0800369 if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
Asias He963ab9e2012-08-02 23:42:03 +0200370 goto new_segment;
371
372 (*sg)->length += nbytes;
373 } else {
374new_segment:
375 if (!*sg)
376 *sg = sglist;
377 else {
378 /*
379 * If the driver previously mapped a shorter
380 * list, we could see a termination bit
381 * prematurely unless it fully inits the sg
382 * table on each mapping. We KNOW that there
383 * must be more entries here or the driver
384 * would be buggy, so force clear the
385 * termination bit to avoid doing a full
386 * sg_init_table() in drivers for each command.
387 */
Paolo Bonzinic8164d82013-03-20 15:37:08 +1030388 sg_unmark_end(*sg);
Asias He963ab9e2012-08-02 23:42:03 +0200389 *sg = sg_next(*sg);
390 }
391
392 sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset);
393 (*nsegs)++;
394 }
Kent Overstreet79886132013-11-23 17:19:00 -0800395 *bvprv = *bvec;
Asias He963ab9e2012-08-02 23:42:03 +0200396}
397
Christoph Hellwigf9d03f92016-12-08 15:20:32 -0700398static inline int __blk_bvec_map_sg(struct request_queue *q, struct bio_vec bv,
399 struct scatterlist *sglist, struct scatterlist **sg)
400{
401 *sg = sglist;
402 sg_set_page(*sg, bv.bv_page, bv.bv_len, bv.bv_offset);
403 return 1;
404}
405
Kent Overstreet5cb88502014-02-07 13:53:46 -0700406static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio,
407 struct scatterlist *sglist,
408 struct scatterlist **sg)
409{
410 struct bio_vec bvec, bvprv = { NULL };
411 struct bvec_iter iter;
Christoph Hellwigf9d03f92016-12-08 15:20:32 -0700412 int cluster = blk_queue_cluster(q), nsegs = 0;
Kent Overstreet5cb88502014-02-07 13:53:46 -0700413
414 for_each_bio(bio)
415 bio_for_each_segment(bvec, bio, iter)
416 __blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg,
417 &nsegs, &cluster);
418
419 return nsegs;
420}
421
Jens Axboed6d48192008-01-29 14:04:06 +0100422/*
423 * map a request to scatterlist, return number of sg entries setup. Caller
424 * must make sure sg can hold rq->nr_phys_segments entries
425 */
426int blk_rq_map_sg(struct request_queue *q, struct request *rq,
427 struct scatterlist *sglist)
428{
Kent Overstreet5cb88502014-02-07 13:53:46 -0700429 struct scatterlist *sg = NULL;
430 int nsegs = 0;
Jens Axboed6d48192008-01-29 14:04:06 +0100431
Christoph Hellwigf9d03f92016-12-08 15:20:32 -0700432 if (rq->rq_flags & RQF_SPECIAL_PAYLOAD)
433 nsegs = __blk_bvec_map_sg(q, rq->special_vec, sglist, &sg);
434 else if (rq->bio && bio_op(rq->bio) == REQ_OP_WRITE_SAME)
435 nsegs = __blk_bvec_map_sg(q, bio_iovec(rq->bio), sglist, &sg);
436 else if (rq->bio)
Kent Overstreet5cb88502014-02-07 13:53:46 -0700437 nsegs = __blk_bios_map_sg(q, rq->bio, sglist, &sg);
FUJITA Tomonorif18573a2008-04-11 12:56:52 +0200438
Christoph Hellwige8064022016-10-20 15:12:13 +0200439 if (unlikely(rq->rq_flags & RQF_COPY_USER) &&
Tejun Heo2e46e8b2009-05-07 22:24:41 +0900440 (blk_rq_bytes(rq) & q->dma_pad_mask)) {
441 unsigned int pad_len =
442 (q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1;
FUJITA Tomonorif18573a2008-04-11 12:56:52 +0200443
444 sg->length += pad_len;
445 rq->extra_len += pad_len;
446 }
447
Tejun Heo2fb98e82008-02-19 11:36:53 +0100448 if (q->dma_drain_size && q->dma_drain_needed(rq)) {
Mike Christiea8ebb052016-06-05 14:31:45 -0500449 if (op_is_write(req_op(rq)))
Tejun Heodb0a2e02008-02-19 11:36:55 +0100450 memset(q->dma_drain_buffer, 0, q->dma_drain_size);
451
Dan Williamsda81ed12015-08-07 18:15:14 +0200452 sg_unmark_end(sg);
Jens Axboed6d48192008-01-29 14:04:06 +0100453 sg = sg_next(sg);
454 sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
455 q->dma_drain_size,
456 ((unsigned long)q->dma_drain_buffer) &
457 (PAGE_SIZE - 1));
458 nsegs++;
FUJITA Tomonori7a85f882008-03-04 11:17:11 +0100459 rq->extra_len += q->dma_drain_size;
Jens Axboed6d48192008-01-29 14:04:06 +0100460 }
461
462 if (sg)
463 sg_mark_end(sg);
464
Ming Lei12e57f52015-11-24 10:35:31 +0800465 /*
466 * Something must have been wrong if the figured number of
467 * segment is bigger than number of req's physical segments
468 */
Christoph Hellwigf9d03f92016-12-08 15:20:32 -0700469 WARN_ON(nsegs > blk_rq_nr_phys_segments(rq));
Ming Lei12e57f52015-11-24 10:35:31 +0800470
Jens Axboed6d48192008-01-29 14:04:06 +0100471 return nsegs;
472}
Jens Axboed6d48192008-01-29 14:04:06 +0100473EXPORT_SYMBOL(blk_rq_map_sg);
474
Jens Axboed6d48192008-01-29 14:04:06 +0100475static inline int ll_new_hw_segment(struct request_queue *q,
476 struct request *req,
477 struct bio *bio)
478{
Jens Axboed6d48192008-01-29 14:04:06 +0100479 int nr_phys_segs = bio_phys_segments(q, bio);
480
Martin K. Petersen13f05c82010-09-10 20:50:10 +0200481 if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q))
482 goto no_merge;
483
Martin K. Petersen4eaf99b2014-09-26 19:20:06 -0400484 if (blk_integrity_merge_bio(q, req, bio) == false)
Martin K. Petersen13f05c82010-09-10 20:50:10 +0200485 goto no_merge;
Jens Axboed6d48192008-01-29 14:04:06 +0100486
487 /*
488 * This will form the start of a new hw segment. Bump both
489 * counters.
490 */
Jens Axboed6d48192008-01-29 14:04:06 +0100491 req->nr_phys_segments += nr_phys_segs;
492 return 1;
Martin K. Petersen13f05c82010-09-10 20:50:10 +0200493
494no_merge:
Ritesh Harjanie0c72302016-12-01 08:36:16 -0700495 req_set_nomerge(q, req);
Martin K. Petersen13f05c82010-09-10 20:50:10 +0200496 return 0;
Jens Axboed6d48192008-01-29 14:04:06 +0100497}
498
499int ll_back_merge_fn(struct request_queue *q, struct request *req,
500 struct bio *bio)
501{
Jens Axboe5e7c4272015-09-03 19:28:20 +0300502 if (req_gap_back_merge(req, bio))
503 return 0;
Sagi Grimberg7f39add2015-09-11 09:03:04 -0600504 if (blk_integrity_rq(req) &&
505 integrity_req_gap_back_merge(req, bio))
506 return 0;
Martin K. Petersenf31dc1c2012-09-18 12:19:26 -0400507 if (blk_rq_sectors(req) + bio_sectors(bio) >
Damien Le Moal17007f32016-07-20 21:40:47 -0600508 blk_rq_get_max_sectors(req, blk_rq_pos(req))) {
Ritesh Harjanie0c72302016-12-01 08:36:16 -0700509 req_set_nomerge(q, req);
Jens Axboed6d48192008-01-29 14:04:06 +0100510 return 0;
511 }
Jens Axboe2cdf79c2008-05-07 09:33:55 +0200512 if (!bio_flagged(req->biotail, BIO_SEG_VALID))
Jens Axboed6d48192008-01-29 14:04:06 +0100513 blk_recount_segments(q, req->biotail);
Jens Axboe2cdf79c2008-05-07 09:33:55 +0200514 if (!bio_flagged(bio, BIO_SEG_VALID))
Jens Axboed6d48192008-01-29 14:04:06 +0100515 blk_recount_segments(q, bio);
Jens Axboed6d48192008-01-29 14:04:06 +0100516
517 return ll_new_hw_segment(q, req, bio);
518}
519
Jens Axboe6728cb02008-01-31 13:03:55 +0100520int ll_front_merge_fn(struct request_queue *q, struct request *req,
Jens Axboed6d48192008-01-29 14:04:06 +0100521 struct bio *bio)
522{
Jens Axboe5e7c4272015-09-03 19:28:20 +0300523
524 if (req_gap_front_merge(req, bio))
525 return 0;
Sagi Grimberg7f39add2015-09-11 09:03:04 -0600526 if (blk_integrity_rq(req) &&
527 integrity_req_gap_front_merge(req, bio))
528 return 0;
Martin K. Petersenf31dc1c2012-09-18 12:19:26 -0400529 if (blk_rq_sectors(req) + bio_sectors(bio) >
Damien Le Moal17007f32016-07-20 21:40:47 -0600530 blk_rq_get_max_sectors(req, bio->bi_iter.bi_sector)) {
Ritesh Harjanie0c72302016-12-01 08:36:16 -0700531 req_set_nomerge(q, req);
Jens Axboed6d48192008-01-29 14:04:06 +0100532 return 0;
533 }
Jens Axboe2cdf79c2008-05-07 09:33:55 +0200534 if (!bio_flagged(bio, BIO_SEG_VALID))
Jens Axboed6d48192008-01-29 14:04:06 +0100535 blk_recount_segments(q, bio);
Jens Axboe2cdf79c2008-05-07 09:33:55 +0200536 if (!bio_flagged(req->bio, BIO_SEG_VALID))
Jens Axboed6d48192008-01-29 14:04:06 +0100537 blk_recount_segments(q, req->bio);
Jens Axboed6d48192008-01-29 14:04:06 +0100538
539 return ll_new_hw_segment(q, req, bio);
540}
541
Jens Axboee7e24502013-10-29 12:11:47 -0600542/*
543 * blk-mq uses req->special to carry normal driver per-request payload, it
544 * does not indicate a prepared command that we cannot merge with.
545 */
546static bool req_no_special_merge(struct request *req)
547{
548 struct request_queue *q = req->q;
549
550 return !q->mq_ops && req->special;
551}
552
Jens Axboe445251d2018-02-01 14:01:02 -0700553static bool req_attempt_discard_merge(struct request_queue *q, struct request *req,
554 struct request *next)
555{
556 unsigned short segments = blk_rq_nr_discard_segments(req);
557
558 if (segments >= queue_max_discard_segments(q))
559 goto no_merge;
560 if (blk_rq_sectors(req) + bio_sectors(next->bio) >
561 blk_rq_get_max_sectors(req, blk_rq_pos(req)))
562 goto no_merge;
563
564 req->nr_phys_segments = segments + blk_rq_nr_discard_segments(next);
565 return true;
566no_merge:
567 req_set_nomerge(q, req);
568 return false;
569}
570
Jens Axboed6d48192008-01-29 14:04:06 +0100571static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
572 struct request *next)
573{
574 int total_phys_segments;
FUJITA Tomonori86771422008-10-13 14:19:05 +0200575 unsigned int seg_size =
576 req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size;
Jens Axboed6d48192008-01-29 14:04:06 +0100577
578 /*
579 * First check if the either of the requests are re-queued
580 * requests. Can't merge them if they are.
581 */
Jens Axboee7e24502013-10-29 12:11:47 -0600582 if (req_no_special_merge(req) || req_no_special_merge(next))
Jens Axboed6d48192008-01-29 14:04:06 +0100583 return 0;
584
Jens Axboe5e7c4272015-09-03 19:28:20 +0300585 if (req_gap_back_merge(req, next->bio))
Keith Busch854fbb92015-02-11 08:20:13 -0700586 return 0;
587
Jens Axboed6d48192008-01-29 14:04:06 +0100588 /*
589 * Will it become too large?
590 */
Martin K. Petersenf31dc1c2012-09-18 12:19:26 -0400591 if ((blk_rq_sectors(req) + blk_rq_sectors(next)) >
Damien Le Moal17007f32016-07-20 21:40:47 -0600592 blk_rq_get_max_sectors(req, blk_rq_pos(req)))
Jens Axboed6d48192008-01-29 14:04:06 +0100593 return 0;
594
595 total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
FUJITA Tomonori86771422008-10-13 14:19:05 +0200596 if (blk_phys_contig_segment(q, req->biotail, next->bio)) {
597 if (req->nr_phys_segments == 1)
598 req->bio->bi_seg_front_size = seg_size;
599 if (next->nr_phys_segments == 1)
600 next->biotail->bi_seg_back_size = seg_size;
Jens Axboed6d48192008-01-29 14:04:06 +0100601 total_phys_segments--;
FUJITA Tomonori86771422008-10-13 14:19:05 +0200602 }
Jens Axboed6d48192008-01-29 14:04:06 +0100603
Martin K. Petersen8a783622010-02-26 00:20:39 -0500604 if (total_phys_segments > queue_max_segments(q))
Jens Axboed6d48192008-01-29 14:04:06 +0100605 return 0;
606
Martin K. Petersen4eaf99b2014-09-26 19:20:06 -0400607 if (blk_integrity_merge_rq(q, req, next) == false)
Martin K. Petersen13f05c82010-09-10 20:50:10 +0200608 return 0;
609
Jens Axboed6d48192008-01-29 14:04:06 +0100610 /* Merge is OK... */
611 req->nr_phys_segments = total_phys_segments;
Jens Axboed6d48192008-01-29 14:04:06 +0100612 return 1;
613}
614
Tejun Heo80a761f2009-07-03 17:48:17 +0900615/**
616 * blk_rq_set_mixed_merge - mark a request as mixed merge
617 * @rq: request to mark as mixed merge
618 *
619 * Description:
620 * @rq is about to be mixed merged. Make sure the attributes
621 * which can be mixed are set in each bio and mark @rq as mixed
622 * merged.
623 */
624void blk_rq_set_mixed_merge(struct request *rq)
625{
626 unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
627 struct bio *bio;
628
Christoph Hellwige8064022016-10-20 15:12:13 +0200629 if (rq->rq_flags & RQF_MIXED_MERGE)
Tejun Heo80a761f2009-07-03 17:48:17 +0900630 return;
631
632 /*
633 * @rq will no longer represent mixable attributes for all the
634 * contained bios. It will just track those of the first one.
635 * Distributes the attributs to each bio.
636 */
637 for (bio = rq->bio; bio; bio = bio->bi_next) {
Jens Axboe1eff9d32016-08-05 15:35:16 -0600638 WARN_ON_ONCE((bio->bi_opf & REQ_FAILFAST_MASK) &&
639 (bio->bi_opf & REQ_FAILFAST_MASK) != ff);
640 bio->bi_opf |= ff;
Tejun Heo80a761f2009-07-03 17:48:17 +0900641 }
Christoph Hellwige8064022016-10-20 15:12:13 +0200642 rq->rq_flags |= RQF_MIXED_MERGE;
Tejun Heo80a761f2009-07-03 17:48:17 +0900643}
644
Jerome Marchand26308ea2009-03-27 10:31:51 +0100645static void blk_account_io_merge(struct request *req)
646{
647 if (blk_do_io_stat(req)) {
648 struct hd_struct *part;
649 int cpu;
650
651 cpu = part_stat_lock();
Jerome Marchand09e099d2011-01-05 16:57:38 +0100652 part = req->part;
Jerome Marchand26308ea2009-03-27 10:31:51 +0100653
Jens Axboed62e26b2017-06-30 21:55:08 -0600654 part_round_stats(req->q, cpu, part);
655 part_dec_in_flight(req->q, part, rq_data_dir(req));
Jerome Marchand26308ea2009-03-27 10:31:51 +0100656
Jens Axboe6c23a962011-01-07 08:43:37 +0100657 hd_struct_put(part);
Jerome Marchand26308ea2009-03-27 10:31:51 +0100658 part_stat_unlock();
659 }
660}
661
Jens Axboed6d48192008-01-29 14:04:06 +0100662/*
Jens Axboeb973cb72017-02-02 08:54:40 -0700663 * For non-mq, this has to be called with the request spinlock acquired.
664 * For mq with scheduling, the appropriate queue wide lock should be held.
Jens Axboed6d48192008-01-29 14:04:06 +0100665 */
Jens Axboeb973cb72017-02-02 08:54:40 -0700666static struct request *attempt_merge(struct request_queue *q,
667 struct request *req, struct request *next)
Jens Axboed6d48192008-01-29 14:04:06 +0100668{
Bart Van Assche2fff8a92017-06-20 11:15:45 -0700669 if (!q->mq_ops)
670 lockdep_assert_held(q->queue_lock);
671
Jens Axboed6d48192008-01-29 14:04:06 +0100672 if (!rq_mergeable(req) || !rq_mergeable(next))
Jens Axboeb973cb72017-02-02 08:54:40 -0700673 return NULL;
Jens Axboed6d48192008-01-29 14:04:06 +0100674
Christoph Hellwig288dab82016-06-09 16:00:36 +0200675 if (req_op(req) != req_op(next))
Jens Axboeb973cb72017-02-02 08:54:40 -0700676 return NULL;
Martin K. Petersenf31dc1c2012-09-18 12:19:26 -0400677
Jens Axboed6d48192008-01-29 14:04:06 +0100678 /*
679 * not contiguous
680 */
Tejun Heo83096eb2009-05-07 22:24:39 +0900681 if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next))
Jens Axboeb973cb72017-02-02 08:54:40 -0700682 return NULL;
Jens Axboed6d48192008-01-29 14:04:06 +0100683
684 if (rq_data_dir(req) != rq_data_dir(next)
685 || req->rq_disk != next->rq_disk
Jens Axboee7e24502013-10-29 12:11:47 -0600686 || req_no_special_merge(next))
Jens Axboeb973cb72017-02-02 08:54:40 -0700687 return NULL;
Jens Axboed6d48192008-01-29 14:04:06 +0100688
Mike Christie8fe0d472016-06-05 14:32:15 -0500689 if (req_op(req) == REQ_OP_WRITE_SAME &&
Martin K. Petersen4363ac72012-09-18 12:19:27 -0400690 !blk_write_same_mergeable(req->bio, next->bio))
Jens Axboeb973cb72017-02-02 08:54:40 -0700691 return NULL;
Martin K. Petersen4363ac72012-09-18 12:19:27 -0400692
Jens Axboed6d48192008-01-29 14:04:06 +0100693 /*
Jens Axboecb6934f2017-06-27 09:22:02 -0600694 * Don't allow merge of different write hints, or for a hint with
695 * non-hint IO.
696 */
697 if (req->write_hint != next->write_hint)
698 return NULL;
699
700 /*
Jens Axboed6d48192008-01-29 14:04:06 +0100701 * If we are allowed to merge, then append bio list
702 * from next to rq and release next. merge_requests_fn
703 * will have updated segment counts, update sector
Jens Axboe445251d2018-02-01 14:01:02 -0700704 * counts here. Handle DISCARDs separately, as they
705 * have separate settings.
Jens Axboed6d48192008-01-29 14:04:06 +0100706 */
Jens Axboe445251d2018-02-01 14:01:02 -0700707 if (req_op(req) == REQ_OP_DISCARD) {
708 if (!req_attempt_discard_merge(q, req, next))
709 return NULL;
710 } else if (!ll_merge_requests_fn(q, req, next))
Jens Axboeb973cb72017-02-02 08:54:40 -0700711 return NULL;
Jens Axboed6d48192008-01-29 14:04:06 +0100712
713 /*
Tejun Heo80a761f2009-07-03 17:48:17 +0900714 * If failfast settings disagree or any of the two is already
715 * a mixed merge, mark both as mixed before proceeding. This
716 * makes sure that all involved bios have mixable attributes
717 * set properly.
718 */
Christoph Hellwige8064022016-10-20 15:12:13 +0200719 if (((req->rq_flags | next->rq_flags) & RQF_MIXED_MERGE) ||
Tejun Heo80a761f2009-07-03 17:48:17 +0900720 (req->cmd_flags & REQ_FAILFAST_MASK) !=
721 (next->cmd_flags & REQ_FAILFAST_MASK)) {
722 blk_rq_set_mixed_merge(req);
723 blk_rq_set_mixed_merge(next);
724 }
725
726 /*
Jens Axboed6d48192008-01-29 14:04:06 +0100727 * At this point we have either done a back merge
728 * or front merge. We need the smaller start_time of
729 * the merged requests to be the current request
730 * for accounting purposes.
731 */
732 if (time_after(req->start_time, next->start_time))
733 req->start_time = next->start_time;
734
735 req->biotail->bi_next = next->bio;
736 req->biotail = next->biotail;
737
Tejun Heoa2dec7b2009-05-07 22:24:44 +0900738 req->__data_len += blk_rq_bytes(next);
Jens Axboed6d48192008-01-29 14:04:06 +0100739
Jens Axboe445251d2018-02-01 14:01:02 -0700740 if (req_op(req) != REQ_OP_DISCARD)
741 elv_merge_requests(q, req, next);
Jens Axboed6d48192008-01-29 14:04:06 +0100742
Jerome Marchand42dad762009-04-22 14:01:49 +0200743 /*
744 * 'next' is going away, so update stats accordingly
745 */
746 blk_account_io_merge(next);
Jens Axboed6d48192008-01-29 14:04:06 +0100747
748 req->ioprio = ioprio_best(req->ioprio, next->ioprio);
Jens Axboeab780f12008-08-26 10:25:02 +0200749 if (blk_rq_cpu_valid(next))
750 req->cpu = next->cpu;
Jens Axboed6d48192008-01-29 14:04:06 +0100751
Jens Axboee4d750c2017-02-03 09:48:28 -0700752 /*
753 * ownership of bio passed from next to req, return 'next' for
754 * the caller to free
755 */
Boaz Harrosh1cd96c22009-03-24 12:35:07 +0100756 next->bio = NULL;
Jens Axboeb973cb72017-02-02 08:54:40 -0700757 return next;
Jens Axboed6d48192008-01-29 14:04:06 +0100758}
759
Jens Axboeb973cb72017-02-02 08:54:40 -0700760struct request *attempt_back_merge(struct request_queue *q, struct request *rq)
Jens Axboed6d48192008-01-29 14:04:06 +0100761{
762 struct request *next = elv_latter_request(q, rq);
763
764 if (next)
765 return attempt_merge(q, rq, next);
766
Jens Axboeb973cb72017-02-02 08:54:40 -0700767 return NULL;
Jens Axboed6d48192008-01-29 14:04:06 +0100768}
769
Jens Axboeb973cb72017-02-02 08:54:40 -0700770struct request *attempt_front_merge(struct request_queue *q, struct request *rq)
Jens Axboed6d48192008-01-29 14:04:06 +0100771{
772 struct request *prev = elv_former_request(q, rq);
773
774 if (prev)
775 return attempt_merge(q, prev, rq);
776
Jens Axboeb973cb72017-02-02 08:54:40 -0700777 return NULL;
Jens Axboed6d48192008-01-29 14:04:06 +0100778}
Jens Axboe5e84ea32011-03-21 10:14:27 +0100779
780int blk_attempt_req_merge(struct request_queue *q, struct request *rq,
781 struct request *next)
782{
Tahsin Erdogan72ef7992016-07-07 11:48:22 -0700783 struct elevator_queue *e = q->elevator;
Jens Axboee4d750c2017-02-03 09:48:28 -0700784 struct request *free;
Tahsin Erdogan72ef7992016-07-07 11:48:22 -0700785
Jens Axboebd166ef2017-01-17 06:03:22 -0700786 if (!e->uses_mq && e->type->ops.sq.elevator_allow_rq_merge_fn)
Jens Axboec51ca6c2016-12-10 15:13:59 -0700787 if (!e->type->ops.sq.elevator_allow_rq_merge_fn(q, rq, next))
Tahsin Erdogan72ef7992016-07-07 11:48:22 -0700788 return 0;
789
Jens Axboee4d750c2017-02-03 09:48:28 -0700790 free = attempt_merge(q, rq, next);
791 if (free) {
792 __blk_put_request(q, free);
793 return 1;
794 }
795
796 return 0;
Jens Axboe5e84ea32011-03-21 10:14:27 +0100797}
Tejun Heo050c8ea2012-02-08 09:19:38 +0100798
799bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
800{
Martin K. Petersene2a60da2012-09-18 12:19:25 -0400801 if (!rq_mergeable(rq) || !bio_mergeable(bio))
Tejun Heo050c8ea2012-02-08 09:19:38 +0100802 return false;
803
Christoph Hellwig288dab82016-06-09 16:00:36 +0200804 if (req_op(rq) != bio_op(bio))
Martin K. Petersenf31dc1c2012-09-18 12:19:26 -0400805 return false;
806
Tejun Heo050c8ea2012-02-08 09:19:38 +0100807 /* different data direction or already started, don't merge */
808 if (bio_data_dir(bio) != rq_data_dir(rq))
809 return false;
810
811 /* must be same device and not a special request */
Christoph Hellwig74d46992017-08-23 19:10:32 +0200812 if (rq->rq_disk != bio->bi_disk || req_no_special_merge(rq))
Tejun Heo050c8ea2012-02-08 09:19:38 +0100813 return false;
814
815 /* only merge integrity protected bio into ditto rq */
Martin K. Petersen4eaf99b2014-09-26 19:20:06 -0400816 if (blk_integrity_merge_bio(rq->q, rq, bio) == false)
Tejun Heo050c8ea2012-02-08 09:19:38 +0100817 return false;
818
Martin K. Petersen4363ac72012-09-18 12:19:27 -0400819 /* must be using the same buffer */
Mike Christie8fe0d472016-06-05 14:32:15 -0500820 if (req_op(rq) == REQ_OP_WRITE_SAME &&
Martin K. Petersen4363ac72012-09-18 12:19:27 -0400821 !blk_write_same_mergeable(rq->bio, bio))
822 return false;
823
Jens Axboecb6934f2017-06-27 09:22:02 -0600824 /*
825 * Don't allow merge of different write hints, or for a hint with
826 * non-hint IO.
827 */
828 if (rq->write_hint != bio->bi_write_hint)
829 return false;
830
Tejun Heo050c8ea2012-02-08 09:19:38 +0100831 return true;
832}
833
Christoph Hellwig34fe7c02017-02-08 14:46:48 +0100834enum elv_merge blk_try_merge(struct request *rq, struct bio *bio)
Tejun Heo050c8ea2012-02-08 09:19:38 +0100835{
Christoph Hellwig1e739732017-02-08 14:46:49 +0100836 if (req_op(rq) == REQ_OP_DISCARD &&
837 queue_max_discard_segments(rq->q) > 1)
838 return ELEVATOR_DISCARD_MERGE;
839 else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector)
Tejun Heo050c8ea2012-02-08 09:19:38 +0100840 return ELEVATOR_BACK_MERGE;
Kent Overstreet4f024f32013-10-11 15:44:27 -0700841 else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector)
Tejun Heo050c8ea2012-02-08 09:19:38 +0100842 return ELEVATOR_FRONT_MERGE;
843 return ELEVATOR_NO_MERGE;
844}