2 * Functions related to segment and merge handling
4 #include <linux/kernel.h>
5 #include <linux/module.h>
7 #include <linux/blkdev.h>
8 #include <linux/scatterlist.h>
12 static struct bio
*blk_bio_discard_split(struct request_queue
*q
,
17 unsigned int max_discard_sectors
, granularity
;
20 unsigned split_sectors
;
24 /* Zero-sector (unknown) and one-sector granularities are the same. */
25 granularity
= max(q
->limits
.discard_granularity
>> 9, 1U);
27 max_discard_sectors
= min(q
->limits
.max_discard_sectors
, UINT_MAX
>> 9);
28 max_discard_sectors
-= max_discard_sectors
% granularity
;
30 if (unlikely(!max_discard_sectors
)) {
35 if (bio_sectors(bio
) <= max_discard_sectors
)
38 split_sectors
= max_discard_sectors
;
41 * If the next starting sector would be misaligned, stop the discard at
42 * the previous aligned sector.
44 alignment
= (q
->limits
.discard_alignment
>> 9) % granularity
;
46 tmp
= bio
->bi_iter
.bi_sector
+ split_sectors
- alignment
;
47 tmp
= sector_div(tmp
, granularity
);
49 if (split_sectors
> tmp
)
52 return bio_split(bio
, split_sectors
, GFP_NOIO
, bs
);
55 static struct bio
*blk_bio_write_same_split(struct request_queue
*q
,
62 if (!q
->limits
.max_write_same_sectors
)
65 if (bio_sectors(bio
) <= q
->limits
.max_write_same_sectors
)
68 return bio_split(bio
, q
->limits
.max_write_same_sectors
, GFP_NOIO
, bs
);
71 static struct bio
*blk_bio_segment_split(struct request_queue
*q
,
76 struct bio_vec bv
, bvprv
, *bvprvp
= NULL
;
77 struct bvec_iter iter
;
78 unsigned seg_size
= 0, nsegs
= 0, sectors
= 0;
80 bio_for_each_segment(bv
, bio
, iter
) {
81 if (sectors
+ (bv
.bv_len
>> 9) > queue_max_sectors(q
))
85 * If the queue doesn't support SG gaps and adding this
86 * offset would create a gap, disallow it.
88 if (bvprvp
&& bvec_gap_to_prev(q
, bvprvp
, bv
.bv_offset
))
91 if (bvprvp
&& blk_queue_cluster(q
)) {
92 if (seg_size
+ bv
.bv_len
> queue_max_segment_size(q
))
94 if (!BIOVEC_PHYS_MERGEABLE(bvprvp
, &bv
))
96 if (!BIOVEC_SEG_BOUNDARY(q
, bvprvp
, &bv
))
99 seg_size
+= bv
.bv_len
;
102 sectors
+= bv
.bv_len
>> 9;
106 if (nsegs
== queue_max_segments(q
))
112 seg_size
= bv
.bv_len
;
113 sectors
+= bv
.bv_len
>> 9;
120 return bio_split(bio
, sectors
, GFP_NOIO
, bs
);
123 void blk_queue_split(struct request_queue
*q
, struct bio
**bio
,
126 struct bio
*split
, *res
;
129 if ((*bio
)->bi_rw
& REQ_DISCARD
)
130 split
= blk_bio_discard_split(q
, *bio
, bs
, &nsegs
);
131 else if ((*bio
)->bi_rw
& REQ_WRITE_SAME
)
132 split
= blk_bio_write_same_split(q
, *bio
, bs
, &nsegs
);
134 split
= blk_bio_segment_split(q
, *bio
, q
->bio_split
, &nsegs
);
136 /* physical segments can be figured out during splitting */
137 res
= split
? split
: *bio
;
138 res
->bi_phys_segments
= nsegs
;
139 bio_set_flag(res
, BIO_SEG_VALID
);
142 /* there isn't chance to merge the splitted bio */
143 split
->bi_rw
|= REQ_NOMERGE
;
145 bio_chain(split
, *bio
);
146 generic_make_request(*bio
);
150 EXPORT_SYMBOL(blk_queue_split
);
152 static unsigned int __blk_recalc_rq_segments(struct request_queue
*q
,
156 struct bio_vec bv
, bvprv
= { NULL
};
157 int cluster
, prev
= 0;
158 unsigned int seg_size
, nr_phys_segs
;
159 struct bio
*fbio
, *bbio
;
160 struct bvec_iter iter
;
166 * This should probably be returning 0, but blk_add_request_payload()
169 if (bio
->bi_rw
& REQ_DISCARD
)
172 if (bio
->bi_rw
& REQ_WRITE_SAME
)
176 cluster
= blk_queue_cluster(q
);
180 bio_for_each_segment(bv
, bio
, iter
) {
182 * If SG merging is disabled, each bio vector is
188 if (prev
&& cluster
) {
189 if (seg_size
+ bv
.bv_len
190 > queue_max_segment_size(q
))
192 if (!BIOVEC_PHYS_MERGEABLE(&bvprv
, &bv
))
194 if (!BIOVEC_SEG_BOUNDARY(q
, &bvprv
, &bv
))
197 seg_size
+= bv
.bv_len
;
202 if (nr_phys_segs
== 1 && seg_size
>
203 fbio
->bi_seg_front_size
)
204 fbio
->bi_seg_front_size
= seg_size
;
209 seg_size
= bv
.bv_len
;
214 if (nr_phys_segs
== 1 && seg_size
> fbio
->bi_seg_front_size
)
215 fbio
->bi_seg_front_size
= seg_size
;
216 if (seg_size
> bbio
->bi_seg_back_size
)
217 bbio
->bi_seg_back_size
= seg_size
;
222 void blk_recalc_rq_segments(struct request
*rq
)
224 bool no_sg_merge
= !!test_bit(QUEUE_FLAG_NO_SG_MERGE
,
225 &rq
->q
->queue_flags
);
227 rq
->nr_phys_segments
= __blk_recalc_rq_segments(rq
->q
, rq
->bio
,
231 void blk_recount_segments(struct request_queue
*q
, struct bio
*bio
)
233 unsigned short seg_cnt
;
235 /* estimate segment number by bi_vcnt for non-cloned bio */
236 if (bio_flagged(bio
, BIO_CLONED
))
237 seg_cnt
= bio_segments(bio
);
239 seg_cnt
= bio
->bi_vcnt
;
241 if (test_bit(QUEUE_FLAG_NO_SG_MERGE
, &q
->queue_flags
) &&
242 (seg_cnt
< queue_max_segments(q
)))
243 bio
->bi_phys_segments
= seg_cnt
;
245 struct bio
*nxt
= bio
->bi_next
;
248 bio
->bi_phys_segments
= __blk_recalc_rq_segments(q
, bio
, false);
252 bio_set_flag(bio
, BIO_SEG_VALID
);
254 EXPORT_SYMBOL(blk_recount_segments
);
256 static int blk_phys_contig_segment(struct request_queue
*q
, struct bio
*bio
,
259 struct bio_vec end_bv
= { NULL
}, nxt_bv
;
260 struct bvec_iter iter
;
262 if (!blk_queue_cluster(q
))
265 if (bio
->bi_seg_back_size
+ nxt
->bi_seg_front_size
>
266 queue_max_segment_size(q
))
269 if (!bio_has_data(bio
))
272 bio_for_each_segment(end_bv
, bio
, iter
)
273 if (end_bv
.bv_len
== iter
.bi_size
)
276 nxt_bv
= bio_iovec(nxt
);
278 if (!BIOVEC_PHYS_MERGEABLE(&end_bv
, &nxt_bv
))
282 * bio and nxt are contiguous in memory; check if the queue allows
283 * these two to be merged into one
285 if (BIOVEC_SEG_BOUNDARY(q
, &end_bv
, &nxt_bv
))
292 __blk_segment_map_sg(struct request_queue
*q
, struct bio_vec
*bvec
,
293 struct scatterlist
*sglist
, struct bio_vec
*bvprv
,
294 struct scatterlist
**sg
, int *nsegs
, int *cluster
)
297 int nbytes
= bvec
->bv_len
;
299 if (*sg
&& *cluster
) {
300 if ((*sg
)->length
+ nbytes
> queue_max_segment_size(q
))
303 if (!BIOVEC_PHYS_MERGEABLE(bvprv
, bvec
))
305 if (!BIOVEC_SEG_BOUNDARY(q
, bvprv
, bvec
))
308 (*sg
)->length
+= nbytes
;
315 * If the driver previously mapped a shorter
316 * list, we could see a termination bit
317 * prematurely unless it fully inits the sg
318 * table on each mapping. We KNOW that there
319 * must be more entries here or the driver
320 * would be buggy, so force clear the
321 * termination bit to avoid doing a full
322 * sg_init_table() in drivers for each command.
328 sg_set_page(*sg
, bvec
->bv_page
, nbytes
, bvec
->bv_offset
);
334 static int __blk_bios_map_sg(struct request_queue
*q
, struct bio
*bio
,
335 struct scatterlist
*sglist
,
336 struct scatterlist
**sg
)
338 struct bio_vec bvec
, bvprv
= { NULL
};
339 struct bvec_iter iter
;
343 cluster
= blk_queue_cluster(q
);
345 if (bio
->bi_rw
& REQ_DISCARD
) {
347 * This is a hack - drivers should be neither modifying the
348 * biovec, nor relying on bi_vcnt - but because of
349 * blk_add_request_payload(), a discard bio may or may not have
350 * a payload we need to set up here (thank you Christoph) and
351 * bi_vcnt is really the only way of telling if we need to.
360 if (bio
->bi_rw
& REQ_WRITE_SAME
) {
363 bvec
= bio_iovec(bio
);
364 sg_set_page(*sg
, bvec
.bv_page
, bvec
.bv_len
, bvec
.bv_offset
);
369 bio_for_each_segment(bvec
, bio
, iter
)
370 __blk_segment_map_sg(q
, &bvec
, sglist
, &bvprv
, sg
,
377 * map a request to scatterlist, return number of sg entries setup. Caller
378 * must make sure sg can hold rq->nr_phys_segments entries
380 int blk_rq_map_sg(struct request_queue
*q
, struct request
*rq
,
381 struct scatterlist
*sglist
)
383 struct scatterlist
*sg
= NULL
;
387 nsegs
= __blk_bios_map_sg(q
, rq
->bio
, sglist
, &sg
);
389 if (unlikely(rq
->cmd_flags
& REQ_COPY_USER
) &&
390 (blk_rq_bytes(rq
) & q
->dma_pad_mask
)) {
391 unsigned int pad_len
=
392 (q
->dma_pad_mask
& ~blk_rq_bytes(rq
)) + 1;
394 sg
->length
+= pad_len
;
395 rq
->extra_len
+= pad_len
;
398 if (q
->dma_drain_size
&& q
->dma_drain_needed(rq
)) {
399 if (rq
->cmd_flags
& REQ_WRITE
)
400 memset(q
->dma_drain_buffer
, 0, q
->dma_drain_size
);
404 sg_set_page(sg
, virt_to_page(q
->dma_drain_buffer
),
406 ((unsigned long)q
->dma_drain_buffer
) &
409 rq
->extra_len
+= q
->dma_drain_size
;
417 EXPORT_SYMBOL(blk_rq_map_sg
);
419 static inline int ll_new_hw_segment(struct request_queue
*q
,
423 int nr_phys_segs
= bio_phys_segments(q
, bio
);
425 if (req
->nr_phys_segments
+ nr_phys_segs
> queue_max_segments(q
))
428 if (blk_integrity_merge_bio(q
, req
, bio
) == false)
432 * This will form the start of a new hw segment. Bump both
435 req
->nr_phys_segments
+= nr_phys_segs
;
439 req
->cmd_flags
|= REQ_NOMERGE
;
440 if (req
== q
->last_merge
)
441 q
->last_merge
= NULL
;
445 int ll_back_merge_fn(struct request_queue
*q
, struct request
*req
,
448 if (req_gap_back_merge(req
, bio
))
450 if (blk_integrity_rq(req
) &&
451 integrity_req_gap_back_merge(req
, bio
))
453 if (blk_rq_sectors(req
) + bio_sectors(bio
) >
454 blk_rq_get_max_sectors(req
)) {
455 req
->cmd_flags
|= REQ_NOMERGE
;
456 if (req
== q
->last_merge
)
457 q
->last_merge
= NULL
;
460 if (!bio_flagged(req
->biotail
, BIO_SEG_VALID
))
461 blk_recount_segments(q
, req
->biotail
);
462 if (!bio_flagged(bio
, BIO_SEG_VALID
))
463 blk_recount_segments(q
, bio
);
465 return ll_new_hw_segment(q
, req
, bio
);
468 int ll_front_merge_fn(struct request_queue
*q
, struct request
*req
,
472 if (req_gap_front_merge(req
, bio
))
474 if (blk_integrity_rq(req
) &&
475 integrity_req_gap_front_merge(req
, bio
))
477 if (blk_rq_sectors(req
) + bio_sectors(bio
) >
478 blk_rq_get_max_sectors(req
)) {
479 req
->cmd_flags
|= REQ_NOMERGE
;
480 if (req
== q
->last_merge
)
481 q
->last_merge
= NULL
;
484 if (!bio_flagged(bio
, BIO_SEG_VALID
))
485 blk_recount_segments(q
, bio
);
486 if (!bio_flagged(req
->bio
, BIO_SEG_VALID
))
487 blk_recount_segments(q
, req
->bio
);
489 return ll_new_hw_segment(q
, req
, bio
);
493 * blk-mq uses req->special to carry normal driver per-request payload, it
494 * does not indicate a prepared command that we cannot merge with.
496 static bool req_no_special_merge(struct request
*req
)
498 struct request_queue
*q
= req
->q
;
500 return !q
->mq_ops
&& req
->special
;
503 static int ll_merge_requests_fn(struct request_queue
*q
, struct request
*req
,
504 struct request
*next
)
506 int total_phys_segments
;
507 unsigned int seg_size
=
508 req
->biotail
->bi_seg_back_size
+ next
->bio
->bi_seg_front_size
;
511 * First check if the either of the requests are re-queued
512 * requests. Can't merge them if they are.
514 if (req_no_special_merge(req
) || req_no_special_merge(next
))
517 if (req_gap_back_merge(req
, next
->bio
))
521 * Will it become too large?
523 if ((blk_rq_sectors(req
) + blk_rq_sectors(next
)) >
524 blk_rq_get_max_sectors(req
))
527 total_phys_segments
= req
->nr_phys_segments
+ next
->nr_phys_segments
;
528 if (blk_phys_contig_segment(q
, req
->biotail
, next
->bio
)) {
529 if (req
->nr_phys_segments
== 1)
530 req
->bio
->bi_seg_front_size
= seg_size
;
531 if (next
->nr_phys_segments
== 1)
532 next
->biotail
->bi_seg_back_size
= seg_size
;
533 total_phys_segments
--;
536 if (total_phys_segments
> queue_max_segments(q
))
539 if (blk_integrity_merge_rq(q
, req
, next
) == false)
543 req
->nr_phys_segments
= total_phys_segments
;
548 * blk_rq_set_mixed_merge - mark a request as mixed merge
549 * @rq: request to mark as mixed merge
552 * @rq is about to be mixed merged. Make sure the attributes
553 * which can be mixed are set in each bio and mark @rq as mixed
556 void blk_rq_set_mixed_merge(struct request
*rq
)
558 unsigned int ff
= rq
->cmd_flags
& REQ_FAILFAST_MASK
;
561 if (rq
->cmd_flags
& REQ_MIXED_MERGE
)
565 * @rq will no longer represent mixable attributes for all the
566 * contained bios. It will just track those of the first one.
567 * Distributes the attributs to each bio.
569 for (bio
= rq
->bio
; bio
; bio
= bio
->bi_next
) {
570 WARN_ON_ONCE((bio
->bi_rw
& REQ_FAILFAST_MASK
) &&
571 (bio
->bi_rw
& REQ_FAILFAST_MASK
) != ff
);
574 rq
->cmd_flags
|= REQ_MIXED_MERGE
;
577 static void blk_account_io_merge(struct request
*req
)
579 if (blk_do_io_stat(req
)) {
580 struct hd_struct
*part
;
583 cpu
= part_stat_lock();
586 part_round_stats(cpu
, part
);
587 part_dec_in_flight(part
, rq_data_dir(req
));
595 * Has to be called with the request spinlock acquired
597 static int attempt_merge(struct request_queue
*q
, struct request
*req
,
598 struct request
*next
)
600 if (!rq_mergeable(req
) || !rq_mergeable(next
))
603 if (!blk_check_merge_flags(req
->cmd_flags
, next
->cmd_flags
))
609 if (blk_rq_pos(req
) + blk_rq_sectors(req
) != blk_rq_pos(next
))
612 if (rq_data_dir(req
) != rq_data_dir(next
)
613 || req
->rq_disk
!= next
->rq_disk
614 || req_no_special_merge(next
))
617 if (req
->cmd_flags
& REQ_WRITE_SAME
&&
618 !blk_write_same_mergeable(req
->bio
, next
->bio
))
622 * If we are allowed to merge, then append bio list
623 * from next to rq and release next. merge_requests_fn
624 * will have updated segment counts, update sector
627 if (!ll_merge_requests_fn(q
, req
, next
))
631 * If failfast settings disagree or any of the two is already
632 * a mixed merge, mark both as mixed before proceeding. This
633 * makes sure that all involved bios have mixable attributes
636 if ((req
->cmd_flags
| next
->cmd_flags
) & REQ_MIXED_MERGE
||
637 (req
->cmd_flags
& REQ_FAILFAST_MASK
) !=
638 (next
->cmd_flags
& REQ_FAILFAST_MASK
)) {
639 blk_rq_set_mixed_merge(req
);
640 blk_rq_set_mixed_merge(next
);
644 * At this point we have either done a back merge
645 * or front merge. We need the smaller start_time of
646 * the merged requests to be the current request
647 * for accounting purposes.
649 if (time_after(req
->start_time
, next
->start_time
))
650 req
->start_time
= next
->start_time
;
652 req
->biotail
->bi_next
= next
->bio
;
653 req
->biotail
= next
->biotail
;
655 req
->__data_len
+= blk_rq_bytes(next
);
657 elv_merge_requests(q
, req
, next
);
660 * 'next' is going away, so update stats accordingly
662 blk_account_io_merge(next
);
664 req
->ioprio
= ioprio_best(req
->ioprio
, next
->ioprio
);
665 if (blk_rq_cpu_valid(next
))
666 req
->cpu
= next
->cpu
;
668 /* owner-ship of bio passed from next to req */
670 __blk_put_request(q
, next
);
674 int attempt_back_merge(struct request_queue
*q
, struct request
*rq
)
676 struct request
*next
= elv_latter_request(q
, rq
);
679 return attempt_merge(q
, rq
, next
);
684 int attempt_front_merge(struct request_queue
*q
, struct request
*rq
)
686 struct request
*prev
= elv_former_request(q
, rq
);
689 return attempt_merge(q
, prev
, rq
);
694 int blk_attempt_req_merge(struct request_queue
*q
, struct request
*rq
,
695 struct request
*next
)
697 return attempt_merge(q
, rq
, next
);
700 bool blk_rq_merge_ok(struct request
*rq
, struct bio
*bio
)
702 if (!rq_mergeable(rq
) || !bio_mergeable(bio
))
705 if (!blk_check_merge_flags(rq
->cmd_flags
, bio
->bi_rw
))
708 /* different data direction or already started, don't merge */
709 if (bio_data_dir(bio
) != rq_data_dir(rq
))
712 /* must be same device and not a special request */
713 if (rq
->rq_disk
!= bio
->bi_bdev
->bd_disk
|| req_no_special_merge(rq
))
716 /* only merge integrity protected bio into ditto rq */
717 if (blk_integrity_merge_bio(rq
->q
, rq
, bio
) == false)
720 /* must be using the same buffer */
721 if (rq
->cmd_flags
& REQ_WRITE_SAME
&&
722 !blk_write_same_mergeable(rq
->bio
, bio
))
728 int blk_try_merge(struct request
*rq
, struct bio
*bio
)
730 if (blk_rq_pos(rq
) + blk_rq_sectors(rq
) == bio
->bi_iter
.bi_sector
)
731 return ELEVATOR_BACK_MERGE
;
732 else if (blk_rq_pos(rq
) - bio_sectors(bio
) == bio
->bi_iter
.bi_sector
)
733 return ELEVATOR_FRONT_MERGE
;
734 return ELEVATOR_NO_MERGE
;
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