blob: 4fced1be5d9730ca3bfcdb98472430eb6f7bc3a0 [file] [log] [blame]
Jens Axboed6d48192008-01-29 14:04:06 +01001/*
2 * Functions related to segment and merge handling
3 */
4#include <linux/kernel.h>
5#include <linux/module.h>
6#include <linux/bio.h>
7#include <linux/blkdev.h>
8#include <linux/scatterlist.h>
9
10#include "blk.h"
11
Jens Axboe1e428072009-02-23 09:03:10 +010012static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
Jens Axboe59247ea2009-03-06 08:55:24 +010013 struct bio *bio)
Jens Axboed6d48192008-01-29 14:04:06 +010014{
Jens Axboed6d48192008-01-29 14:04:06 +010015 struct bio_vec *bv, *bvprv = NULL;
Jens Axboe1e428072009-02-23 09:03:10 +010016 int cluster, i, high, highprv = 1;
17 unsigned int seg_size, nr_phys_segs;
Jens Axboe59247ea2009-03-06 08:55:24 +010018 struct bio *fbio, *bbio;
Jens Axboed6d48192008-01-29 14:04:06 +010019
Jens Axboe1e428072009-02-23 09:03:10 +010020 if (!bio)
21 return 0;
Jens Axboed6d48192008-01-29 14:04:06 +010022
Jens Axboe1e428072009-02-23 09:03:10 +010023 fbio = bio;
Martin K. Petersene692cb62010-12-01 19:41:49 +010024 cluster = blk_queue_cluster(q);
Mikulas Patocka5df97b92008-08-15 10:20:02 +020025 seg_size = 0;
Andi Kleen2c8919d2010-06-21 11:02:47 +020026 nr_phys_segs = 0;
Jens Axboe1e428072009-02-23 09:03:10 +010027 for_each_bio(bio) {
28 bio_for_each_segment(bv, bio, i) {
29 /*
30 * the trick here is making sure that a high page is
31 * never considered part of another segment, since that
32 * might change with the bounce page.
33 */
Martin K. Petersenae03bf62009-05-22 17:17:50 -040034 high = page_to_pfn(bv->bv_page) > queue_bounce_pfn(q);
Jens Axboe1e428072009-02-23 09:03:10 +010035 if (high || highprv)
Jens Axboed6d48192008-01-29 14:04:06 +010036 goto new_segment;
Jens Axboe1e428072009-02-23 09:03:10 +010037 if (cluster) {
Martin K. Petersenae03bf62009-05-22 17:17:50 -040038 if (seg_size + bv->bv_len
39 > queue_max_segment_size(q))
Jens Axboe1e428072009-02-23 09:03:10 +010040 goto new_segment;
41 if (!BIOVEC_PHYS_MERGEABLE(bvprv, bv))
42 goto new_segment;
43 if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bv))
44 goto new_segment;
Jens Axboed6d48192008-01-29 14:04:06 +010045
Jens Axboe1e428072009-02-23 09:03:10 +010046 seg_size += bv->bv_len;
47 bvprv = bv;
48 continue;
49 }
Jens Axboed6d48192008-01-29 14:04:06 +010050new_segment:
Jens Axboe1e428072009-02-23 09:03:10 +010051 if (nr_phys_segs == 1 && seg_size >
52 fbio->bi_seg_front_size)
53 fbio->bi_seg_front_size = seg_size;
FUJITA Tomonori86771422008-10-13 14:19:05 +020054
Jens Axboe1e428072009-02-23 09:03:10 +010055 nr_phys_segs++;
56 bvprv = bv;
57 seg_size = bv->bv_len;
58 highprv = high;
59 }
Jens Axboe59247ea2009-03-06 08:55:24 +010060 bbio = bio;
Jens Axboed6d48192008-01-29 14:04:06 +010061 }
62
Jens Axboe59247ea2009-03-06 08:55:24 +010063 if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size)
64 fbio->bi_seg_front_size = seg_size;
65 if (seg_size > bbio->bi_seg_back_size)
66 bbio->bi_seg_back_size = seg_size;
Jens Axboe1e428072009-02-23 09:03:10 +010067
68 return nr_phys_segs;
69}
70
71void blk_recalc_rq_segments(struct request *rq)
72{
Jens Axboe59247ea2009-03-06 08:55:24 +010073 rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio);
Jens Axboed6d48192008-01-29 14:04:06 +010074}
75
76void blk_recount_segments(struct request_queue *q, struct bio *bio)
77{
Jens Axboed6d48192008-01-29 14:04:06 +010078 struct bio *nxt = bio->bi_next;
Jens Axboe1e428072009-02-23 09:03:10 +010079
Jens Axboed6d48192008-01-29 14:04:06 +010080 bio->bi_next = NULL;
Jens Axboe59247ea2009-03-06 08:55:24 +010081 bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio);
Jens Axboed6d48192008-01-29 14:04:06 +010082 bio->bi_next = nxt;
Jens Axboed6d48192008-01-29 14:04:06 +010083 bio->bi_flags |= (1 << BIO_SEG_VALID);
84}
85EXPORT_SYMBOL(blk_recount_segments);
86
87static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
88 struct bio *nxt)
89{
Martin K. Petersene692cb62010-12-01 19:41:49 +010090 if (!blk_queue_cluster(q))
Jens Axboed6d48192008-01-29 14:04:06 +010091 return 0;
92
FUJITA Tomonori86771422008-10-13 14:19:05 +020093 if (bio->bi_seg_back_size + nxt->bi_seg_front_size >
Martin K. Petersenae03bf62009-05-22 17:17:50 -040094 queue_max_segment_size(q))
Jens Axboed6d48192008-01-29 14:04:06 +010095 return 0;
96
David Woodhousee17fc0a2008-08-09 16:42:20 +010097 if (!bio_has_data(bio))
98 return 1;
99
100 if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)))
101 return 0;
102
Jens Axboed6d48192008-01-29 14:04:06 +0100103 /*
David Woodhousee17fc0a2008-08-09 16:42:20 +0100104 * bio and nxt are contiguous in memory; check if the queue allows
Jens Axboed6d48192008-01-29 14:04:06 +0100105 * these two to be merged into one
106 */
107 if (BIO_SEG_BOUNDARY(q, bio, nxt))
108 return 1;
109
110 return 0;
111}
112
Jens Axboed6d48192008-01-29 14:04:06 +0100113/*
114 * map a request to scatterlist, return number of sg entries setup. Caller
115 * must make sure sg can hold rq->nr_phys_segments entries
116 */
117int blk_rq_map_sg(struct request_queue *q, struct request *rq,
118 struct scatterlist *sglist)
119{
120 struct bio_vec *bvec, *bvprv;
121 struct req_iterator iter;
122 struct scatterlist *sg;
123 int nsegs, cluster;
124
125 nsegs = 0;
Martin K. Petersene692cb62010-12-01 19:41:49 +0100126 cluster = blk_queue_cluster(q);
Jens Axboed6d48192008-01-29 14:04:06 +0100127
128 /*
129 * for each bio in rq
130 */
131 bvprv = NULL;
132 sg = NULL;
133 rq_for_each_segment(bvec, rq, iter) {
134 int nbytes = bvec->bv_len;
135
136 if (bvprv && cluster) {
Martin K. Petersenae03bf62009-05-22 17:17:50 -0400137 if (sg->length + nbytes > queue_max_segment_size(q))
Jens Axboed6d48192008-01-29 14:04:06 +0100138 goto new_segment;
139
140 if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
141 goto new_segment;
142 if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
143 goto new_segment;
144
145 sg->length += nbytes;
146 } else {
147new_segment:
148 if (!sg)
149 sg = sglist;
150 else {
151 /*
152 * If the driver previously mapped a shorter
153 * list, we could see a termination bit
154 * prematurely unless it fully inits the sg
155 * table on each mapping. We KNOW that there
156 * must be more entries here or the driver
157 * would be buggy, so force clear the
158 * termination bit to avoid doing a full
159 * sg_init_table() in drivers for each command.
160 */
161 sg->page_link &= ~0x02;
162 sg = sg_next(sg);
163 }
164
165 sg_set_page(sg, bvec->bv_page, nbytes, bvec->bv_offset);
166 nsegs++;
167 }
168 bvprv = bvec;
169 } /* segments in rq */
170
FUJITA Tomonorif18573a2008-04-11 12:56:52 +0200171
172 if (unlikely(rq->cmd_flags & REQ_COPY_USER) &&
Tejun Heo2e46e8b2009-05-07 22:24:41 +0900173 (blk_rq_bytes(rq) & q->dma_pad_mask)) {
174 unsigned int pad_len =
175 (q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1;
FUJITA Tomonorif18573a2008-04-11 12:56:52 +0200176
177 sg->length += pad_len;
178 rq->extra_len += pad_len;
179 }
180
Tejun Heo2fb98e82008-02-19 11:36:53 +0100181 if (q->dma_drain_size && q->dma_drain_needed(rq)) {
Christoph Hellwig7b6d91d2010-08-07 18:20:39 +0200182 if (rq->cmd_flags & REQ_WRITE)
Tejun Heodb0a2e02008-02-19 11:36:55 +0100183 memset(q->dma_drain_buffer, 0, q->dma_drain_size);
184
Jens Axboed6d48192008-01-29 14:04:06 +0100185 sg->page_link &= ~0x02;
186 sg = sg_next(sg);
187 sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
188 q->dma_drain_size,
189 ((unsigned long)q->dma_drain_buffer) &
190 (PAGE_SIZE - 1));
191 nsegs++;
FUJITA Tomonori7a85f882008-03-04 11:17:11 +0100192 rq->extra_len += q->dma_drain_size;
Jens Axboed6d48192008-01-29 14:04:06 +0100193 }
194
195 if (sg)
196 sg_mark_end(sg);
197
198 return nsegs;
199}
Jens Axboed6d48192008-01-29 14:04:06 +0100200EXPORT_SYMBOL(blk_rq_map_sg);
201
Jens Axboed6d48192008-01-29 14:04:06 +0100202static inline int ll_new_hw_segment(struct request_queue *q,
203 struct request *req,
204 struct bio *bio)
205{
Jens Axboed6d48192008-01-29 14:04:06 +0100206 int nr_phys_segs = bio_phys_segments(q, bio);
207
Martin K. Petersen13f05c82010-09-10 20:50:10 +0200208 if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q))
209 goto no_merge;
210
211 if (bio_integrity(bio) && blk_integrity_merge_bio(q, req, bio))
212 goto no_merge;
Jens Axboed6d48192008-01-29 14:04:06 +0100213
214 /*
215 * This will form the start of a new hw segment. Bump both
216 * counters.
217 */
Jens Axboed6d48192008-01-29 14:04:06 +0100218 req->nr_phys_segments += nr_phys_segs;
219 return 1;
Martin K. Petersen13f05c82010-09-10 20:50:10 +0200220
221no_merge:
222 req->cmd_flags |= REQ_NOMERGE;
223 if (req == q->last_merge)
224 q->last_merge = NULL;
225 return 0;
Jens Axboed6d48192008-01-29 14:04:06 +0100226}
227
228int ll_back_merge_fn(struct request_queue *q, struct request *req,
229 struct bio *bio)
230{
231 unsigned short max_sectors;
Jens Axboed6d48192008-01-29 14:04:06 +0100232
Christoph Hellwig33659eb2010-08-07 18:17:56 +0200233 if (unlikely(req->cmd_type == REQ_TYPE_BLOCK_PC))
Martin K. Petersenae03bf62009-05-22 17:17:50 -0400234 max_sectors = queue_max_hw_sectors(q);
Jens Axboed6d48192008-01-29 14:04:06 +0100235 else
Martin K. Petersenae03bf62009-05-22 17:17:50 -0400236 max_sectors = queue_max_sectors(q);
Jens Axboed6d48192008-01-29 14:04:06 +0100237
Tejun Heo83096eb2009-05-07 22:24:39 +0900238 if (blk_rq_sectors(req) + bio_sectors(bio) > max_sectors) {
Jens Axboed6d48192008-01-29 14:04:06 +0100239 req->cmd_flags |= REQ_NOMERGE;
240 if (req == q->last_merge)
241 q->last_merge = NULL;
242 return 0;
243 }
Jens Axboe2cdf79c2008-05-07 09:33:55 +0200244 if (!bio_flagged(req->biotail, BIO_SEG_VALID))
Jens Axboed6d48192008-01-29 14:04:06 +0100245 blk_recount_segments(q, req->biotail);
Jens Axboe2cdf79c2008-05-07 09:33:55 +0200246 if (!bio_flagged(bio, BIO_SEG_VALID))
Jens Axboed6d48192008-01-29 14:04:06 +0100247 blk_recount_segments(q, bio);
Jens Axboed6d48192008-01-29 14:04:06 +0100248
249 return ll_new_hw_segment(q, req, bio);
250}
251
Jens Axboe6728cb02008-01-31 13:03:55 +0100252int ll_front_merge_fn(struct request_queue *q, struct request *req,
Jens Axboed6d48192008-01-29 14:04:06 +0100253 struct bio *bio)
254{
255 unsigned short max_sectors;
Jens Axboed6d48192008-01-29 14:04:06 +0100256
Christoph Hellwig33659eb2010-08-07 18:17:56 +0200257 if (unlikely(req->cmd_type == REQ_TYPE_BLOCK_PC))
Martin K. Petersenae03bf62009-05-22 17:17:50 -0400258 max_sectors = queue_max_hw_sectors(q);
Jens Axboed6d48192008-01-29 14:04:06 +0100259 else
Martin K. Petersenae03bf62009-05-22 17:17:50 -0400260 max_sectors = queue_max_sectors(q);
Jens Axboed6d48192008-01-29 14:04:06 +0100261
262
Tejun Heo83096eb2009-05-07 22:24:39 +0900263 if (blk_rq_sectors(req) + bio_sectors(bio) > max_sectors) {
Jens Axboed6d48192008-01-29 14:04:06 +0100264 req->cmd_flags |= REQ_NOMERGE;
265 if (req == q->last_merge)
266 q->last_merge = NULL;
267 return 0;
268 }
Jens Axboe2cdf79c2008-05-07 09:33:55 +0200269 if (!bio_flagged(bio, BIO_SEG_VALID))
Jens Axboed6d48192008-01-29 14:04:06 +0100270 blk_recount_segments(q, bio);
Jens Axboe2cdf79c2008-05-07 09:33:55 +0200271 if (!bio_flagged(req->bio, BIO_SEG_VALID))
Jens Axboed6d48192008-01-29 14:04:06 +0100272 blk_recount_segments(q, req->bio);
Jens Axboed6d48192008-01-29 14:04:06 +0100273
274 return ll_new_hw_segment(q, req, bio);
275}
276
277static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
278 struct request *next)
279{
280 int total_phys_segments;
FUJITA Tomonori86771422008-10-13 14:19:05 +0200281 unsigned int seg_size =
282 req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size;
Jens Axboed6d48192008-01-29 14:04:06 +0100283
284 /*
285 * First check if the either of the requests are re-queued
286 * requests. Can't merge them if they are.
287 */
288 if (req->special || next->special)
289 return 0;
290
291 /*
292 * Will it become too large?
293 */
Martin K. Petersenae03bf62009-05-22 17:17:50 -0400294 if ((blk_rq_sectors(req) + blk_rq_sectors(next)) > queue_max_sectors(q))
Jens Axboed6d48192008-01-29 14:04:06 +0100295 return 0;
296
297 total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
FUJITA Tomonori86771422008-10-13 14:19:05 +0200298 if (blk_phys_contig_segment(q, req->biotail, next->bio)) {
299 if (req->nr_phys_segments == 1)
300 req->bio->bi_seg_front_size = seg_size;
301 if (next->nr_phys_segments == 1)
302 next->biotail->bi_seg_back_size = seg_size;
Jens Axboed6d48192008-01-29 14:04:06 +0100303 total_phys_segments--;
FUJITA Tomonori86771422008-10-13 14:19:05 +0200304 }
Jens Axboed6d48192008-01-29 14:04:06 +0100305
Martin K. Petersen8a783622010-02-26 00:20:39 -0500306 if (total_phys_segments > queue_max_segments(q))
Jens Axboed6d48192008-01-29 14:04:06 +0100307 return 0;
308
Martin K. Petersen13f05c82010-09-10 20:50:10 +0200309 if (blk_integrity_rq(req) && blk_integrity_merge_rq(q, req, next))
310 return 0;
311
Jens Axboed6d48192008-01-29 14:04:06 +0100312 /* Merge is OK... */
313 req->nr_phys_segments = total_phys_segments;
Jens Axboed6d48192008-01-29 14:04:06 +0100314 return 1;
315}
316
Tejun Heo80a761f2009-07-03 17:48:17 +0900317/**
318 * blk_rq_set_mixed_merge - mark a request as mixed merge
319 * @rq: request to mark as mixed merge
320 *
321 * Description:
322 * @rq is about to be mixed merged. Make sure the attributes
323 * which can be mixed are set in each bio and mark @rq as mixed
324 * merged.
325 */
326void blk_rq_set_mixed_merge(struct request *rq)
327{
328 unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
329 struct bio *bio;
330
331 if (rq->cmd_flags & REQ_MIXED_MERGE)
332 return;
333
334 /*
335 * @rq will no longer represent mixable attributes for all the
336 * contained bios. It will just track those of the first one.
337 * Distributes the attributs to each bio.
338 */
339 for (bio = rq->bio; bio; bio = bio->bi_next) {
340 WARN_ON_ONCE((bio->bi_rw & REQ_FAILFAST_MASK) &&
341 (bio->bi_rw & REQ_FAILFAST_MASK) != ff);
342 bio->bi_rw |= ff;
343 }
344 rq->cmd_flags |= REQ_MIXED_MERGE;
345}
346
Jerome Marchand26308ea2009-03-27 10:31:51 +0100347static void blk_account_io_merge(struct request *req)
348{
349 if (blk_do_io_stat(req)) {
350 struct hd_struct *part;
351 int cpu;
352
353 cpu = part_stat_lock();
Jerome Marchand09e099d2011-01-05 16:57:38 +0100354 part = req->part;
Jerome Marchand26308ea2009-03-27 10:31:51 +0100355
356 part_round_stats(cpu, part);
Nikanth Karthikesan316d3152009-10-06 20:16:55 +0200357 part_dec_in_flight(part, rq_data_dir(req));
Jerome Marchand26308ea2009-03-27 10:31:51 +0100358
Jens Axboe6c23a962011-01-07 08:43:37 +0100359 hd_struct_put(part);
Jerome Marchand26308ea2009-03-27 10:31:51 +0100360 part_stat_unlock();
361 }
362}
363
Jens Axboed6d48192008-01-29 14:04:06 +0100364/*
365 * Has to be called with the request spinlock acquired
366 */
367static int attempt_merge(struct request_queue *q, struct request *req,
368 struct request *next)
369{
370 if (!rq_mergeable(req) || !rq_mergeable(next))
371 return 0;
372
373 /*
Adrian Hunterf281fb52010-09-25 12:42:55 +0200374 * Don't merge file system requests and discard requests
375 */
376 if ((req->cmd_flags & REQ_DISCARD) != (next->cmd_flags & REQ_DISCARD))
377 return 0;
378
379 /*
380 * Don't merge discard requests and secure discard requests
381 */
382 if ((req->cmd_flags & REQ_SECURE) != (next->cmd_flags & REQ_SECURE))
383 return 0;
384
385 /*
Maya Erez73937f52012-05-24 23:33:05 +0300386 * Don't merge file system requests and sanitize requests
387 */
388 if ((req->cmd_flags & REQ_SANITIZE) != (next->cmd_flags & REQ_SANITIZE))
389 return 0;
390
391 /*
Jens Axboed6d48192008-01-29 14:04:06 +0100392 * not contiguous
393 */
Tejun Heo83096eb2009-05-07 22:24:39 +0900394 if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next))
Jens Axboed6d48192008-01-29 14:04:06 +0100395 return 0;
396
397 if (rq_data_dir(req) != rq_data_dir(next)
398 || req->rq_disk != next->rq_disk
399 || next->special)
400 return 0;
401
402 /*
403 * If we are allowed to merge, then append bio list
404 * from next to rq and release next. merge_requests_fn
405 * will have updated segment counts, update sector
406 * counts here.
407 */
408 if (!ll_merge_requests_fn(q, req, next))
409 return 0;
410
411 /*
Tejun Heo80a761f2009-07-03 17:48:17 +0900412 * If failfast settings disagree or any of the two is already
413 * a mixed merge, mark both as mixed before proceeding. This
414 * makes sure that all involved bios have mixable attributes
415 * set properly.
416 */
417 if ((req->cmd_flags | next->cmd_flags) & REQ_MIXED_MERGE ||
418 (req->cmd_flags & REQ_FAILFAST_MASK) !=
419 (next->cmd_flags & REQ_FAILFAST_MASK)) {
420 blk_rq_set_mixed_merge(req);
421 blk_rq_set_mixed_merge(next);
422 }
423
424 /*
Jens Axboed6d48192008-01-29 14:04:06 +0100425 * At this point we have either done a back merge
426 * or front merge. We need the smaller start_time of
427 * the merged requests to be the current request
428 * for accounting purposes.
429 */
430 if (time_after(req->start_time, next->start_time))
431 req->start_time = next->start_time;
432
433 req->biotail->bi_next = next->bio;
434 req->biotail = next->biotail;
435
Tejun Heoa2dec7b2009-05-07 22:24:44 +0900436 req->__data_len += blk_rq_bytes(next);
Jens Axboed6d48192008-01-29 14:04:06 +0100437
438 elv_merge_requests(q, req, next);
439
Jerome Marchand42dad762009-04-22 14:01:49 +0200440 /*
441 * 'next' is going away, so update stats accordingly
442 */
443 blk_account_io_merge(next);
Jens Axboed6d48192008-01-29 14:04:06 +0100444
445 req->ioprio = ioprio_best(req->ioprio, next->ioprio);
Jens Axboeab780f12008-08-26 10:25:02 +0200446 if (blk_rq_cpu_valid(next))
447 req->cpu = next->cpu;
Jens Axboed6d48192008-01-29 14:04:06 +0100448
Boaz Harrosh1cd96c22009-03-24 12:35:07 +0100449 /* owner-ship of bio passed from next to req */
450 next->bio = NULL;
Jens Axboed6d48192008-01-29 14:04:06 +0100451 __blk_put_request(q, next);
452 return 1;
453}
454
455int attempt_back_merge(struct request_queue *q, struct request *rq)
456{
457 struct request *next = elv_latter_request(q, rq);
458
459 if (next)
460 return attempt_merge(q, rq, next);
461
462 return 0;
463}
464
465int attempt_front_merge(struct request_queue *q, struct request *rq)
466{
467 struct request *prev = elv_former_request(q, rq);
468
469 if (prev)
470 return attempt_merge(q, prev, rq);
471
472 return 0;
473}
Jens Axboe5e84ea32011-03-21 10:14:27 +0100474
475int blk_attempt_req_merge(struct request_queue *q, struct request *rq,
476 struct request *next)
477{
478 return attempt_merge(q, rq, next);
479}
Tejun Heo050c8ea2012-02-08 09:19:38 +0100480
481bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
482{
483 if (!rq_mergeable(rq))
484 return false;
485
486 /* don't merge file system requests and discard requests */
487 if ((bio->bi_rw & REQ_DISCARD) != (rq->bio->bi_rw & REQ_DISCARD))
488 return false;
489
490 /* don't merge discard requests and secure discard requests */
491 if ((bio->bi_rw & REQ_SECURE) != (rq->bio->bi_rw & REQ_SECURE))
492 return false;
493
494 /* different data direction or already started, don't merge */
495 if (bio_data_dir(bio) != rq_data_dir(rq))
496 return false;
497
498 /* must be same device and not a special request */
499 if (rq->rq_disk != bio->bi_bdev->bd_disk || rq->special)
500 return false;
501
502 /* only merge integrity protected bio into ditto rq */
503 if (bio_integrity(bio) != blk_integrity_rq(rq))
504 return false;
505
506 return true;
507}
508
509int blk_try_merge(struct request *rq, struct bio *bio)
510{
511 if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_sector)
512 return ELEVATOR_BACK_MERGE;
513 else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_sector)
514 return ELEVATOR_FRONT_MERGE;
515 return ELEVATOR_NO_MERGE;
516}