]>
git.proxmox.com Git - mirror_ubuntu-jammy-kernel.git/blob - block/blk-merge.c
1 // SPDX-License-Identifier: GPL-2.0
3 * Functions related to segment and merge handling
5 #include <linux/kernel.h>
6 #include <linux/module.h>
8 #include <linux/blkdev.h>
9 #include <linux/scatterlist.h>
11 #include <trace/events/block.h>
16 * Check if the two bvecs from two bios can be merged to one segment. If yes,
17 * no need to check gap between the two bios since the 1st bio and the 1st bvec
18 * in the 2nd bio can be handled in one segment.
20 static inline bool bios_segs_mergeable(struct request_queue
*q
,
21 struct bio
*prev
, struct bio_vec
*prev_last_bv
,
22 struct bio_vec
*next_first_bv
)
24 if (!biovec_phys_mergeable(q
, prev_last_bv
, next_first_bv
))
26 if (prev
->bi_seg_back_size
+ next_first_bv
->bv_len
>
27 queue_max_segment_size(q
))
32 static inline bool bio_will_gap(struct request_queue
*q
,
33 struct request
*prev_rq
, struct bio
*prev
, struct bio
*next
)
35 struct bio_vec pb
, nb
;
37 if (!bio_has_data(prev
) || !queue_virt_boundary(q
))
41 * Don't merge if the 1st bio starts with non-zero offset, otherwise it
42 * is quite difficult to respect the sg gap limit. We work hard to
43 * merge a huge number of small single bios in case of mkfs.
46 bio_get_first_bvec(prev_rq
->bio
, &pb
);
48 bio_get_first_bvec(prev
, &pb
);
49 if (pb
.bv_offset
& queue_virt_boundary(q
))
53 * We don't need to worry about the situation that the merged segment
54 * ends in unaligned virt boundary:
56 * - if 'pb' ends aligned, the merged segment ends aligned
57 * - if 'pb' ends unaligned, the next bio must include
58 * one single bvec of 'nb', otherwise the 'nb' can't
61 bio_get_last_bvec(prev
, &pb
);
62 bio_get_first_bvec(next
, &nb
);
63 if (bios_segs_mergeable(q
, prev
, &pb
, &nb
))
65 return __bvec_gap_to_prev(q
, &pb
, nb
.bv_offset
);
68 static inline bool req_gap_back_merge(struct request
*req
, struct bio
*bio
)
70 return bio_will_gap(req
->q
, req
, req
->biotail
, bio
);
73 static inline bool req_gap_front_merge(struct request
*req
, struct bio
*bio
)
75 return bio_will_gap(req
->q
, NULL
, bio
, req
->bio
);
78 static struct bio
*blk_bio_discard_split(struct request_queue
*q
,
83 unsigned int max_discard_sectors
, granularity
;
86 unsigned split_sectors
;
90 /* Zero-sector (unknown) and one-sector granularities are the same. */
91 granularity
= max(q
->limits
.discard_granularity
>> 9, 1U);
93 max_discard_sectors
= min(q
->limits
.max_discard_sectors
,
94 bio_allowed_max_sectors(q
));
95 max_discard_sectors
-= max_discard_sectors
% granularity
;
97 if (unlikely(!max_discard_sectors
)) {
102 if (bio_sectors(bio
) <= max_discard_sectors
)
105 split_sectors
= max_discard_sectors
;
108 * If the next starting sector would be misaligned, stop the discard at
109 * the previous aligned sector.
111 alignment
= (q
->limits
.discard_alignment
>> 9) % granularity
;
113 tmp
= bio
->bi_iter
.bi_sector
+ split_sectors
- alignment
;
114 tmp
= sector_div(tmp
, granularity
);
116 if (split_sectors
> tmp
)
117 split_sectors
-= tmp
;
119 return bio_split(bio
, split_sectors
, GFP_NOIO
, bs
);
122 static struct bio
*blk_bio_write_zeroes_split(struct request_queue
*q
,
123 struct bio
*bio
, struct bio_set
*bs
, unsigned *nsegs
)
127 if (!q
->limits
.max_write_zeroes_sectors
)
130 if (bio_sectors(bio
) <= q
->limits
.max_write_zeroes_sectors
)
133 return bio_split(bio
, q
->limits
.max_write_zeroes_sectors
, GFP_NOIO
, bs
);
136 static struct bio
*blk_bio_write_same_split(struct request_queue
*q
,
143 if (!q
->limits
.max_write_same_sectors
)
146 if (bio_sectors(bio
) <= q
->limits
.max_write_same_sectors
)
149 return bio_split(bio
, q
->limits
.max_write_same_sectors
, GFP_NOIO
, bs
);
152 static inline unsigned get_max_io_size(struct request_queue
*q
,
155 unsigned sectors
= blk_max_size_offset(q
, bio
->bi_iter
.bi_sector
);
156 unsigned mask
= queue_logical_block_size(q
) - 1;
158 /* aligned to logical block size */
159 sectors
&= ~(mask
>> 9);
164 static unsigned get_max_segment_size(struct request_queue
*q
,
167 unsigned long mask
= queue_segment_boundary(q
);
169 /* default segment boundary mask means no boundary limit */
170 if (mask
== BLK_SEG_BOUNDARY_MASK
)
171 return queue_max_segment_size(q
);
173 return min_t(unsigned long, mask
- (mask
& offset
) + 1,
174 queue_max_segment_size(q
));
178 * Split the bvec @bv into segments, and update all kinds of
181 static bool bvec_split_segs(struct request_queue
*q
, struct bio_vec
*bv
,
182 unsigned *nsegs
, unsigned *last_seg_size
,
183 unsigned *front_seg_size
, unsigned *sectors
)
185 unsigned len
= bv
->bv_len
;
186 unsigned total_len
= 0;
187 unsigned new_nsegs
= 0, seg_size
= 0;
190 * Multi-page bvec may be too big to hold in one segment, so the
191 * current bvec has to be splitted as multiple segments.
193 while (len
&& new_nsegs
+ *nsegs
< queue_max_segments(q
)) {
194 seg_size
= get_max_segment_size(q
, bv
->bv_offset
+ total_len
);
195 seg_size
= min(seg_size
, len
);
198 total_len
+= seg_size
;
201 if ((bv
->bv_offset
+ total_len
) & queue_virt_boundary(q
))
208 /* update front segment size */
210 unsigned first_seg_size
;
213 first_seg_size
= get_max_segment_size(q
, bv
->bv_offset
);
215 first_seg_size
= queue_max_segment_size(q
);
217 if (*front_seg_size
< first_seg_size
)
218 *front_seg_size
= first_seg_size
;
221 /* update other varibles */
222 *last_seg_size
= seg_size
;
225 *sectors
+= total_len
>> 9;
227 /* split in the middle of the bvec if len != 0 */
231 static struct bio
*blk_bio_segment_split(struct request_queue
*q
,
236 struct bio_vec bv
, bvprv
, *bvprvp
= NULL
;
237 struct bvec_iter iter
;
238 unsigned seg_size
= 0, nsegs
= 0, sectors
= 0;
239 unsigned front_seg_size
= bio
->bi_seg_front_size
;
240 bool do_split
= true;
241 struct bio
*new = NULL
;
242 const unsigned max_sectors
= get_max_io_size(q
, bio
);
244 bio_for_each_bvec(bv
, bio
, iter
) {
246 * If the queue doesn't support SG gaps and adding this
247 * offset would create a gap, disallow it.
249 if (bvprvp
&& bvec_gap_to_prev(q
, bvprvp
, bv
.bv_offset
))
252 if (sectors
+ (bv
.bv_len
>> 9) > max_sectors
) {
254 * Consider this a new segment if we're splitting in
255 * the middle of this vector.
257 if (nsegs
< queue_max_segments(q
) &&
258 sectors
< max_sectors
) {
259 /* split in the middle of bvec */
260 bv
.bv_len
= (max_sectors
- sectors
) << 9;
261 bvec_split_segs(q
, &bv
, &nsegs
,
270 if (seg_size
+ bv
.bv_len
> queue_max_segment_size(q
))
272 if (!biovec_phys_mergeable(q
, bvprvp
, &bv
))
275 seg_size
+= bv
.bv_len
;
278 sectors
+= bv
.bv_len
>> 9;
283 if (nsegs
== queue_max_segments(q
))
289 if (bvec_split_segs(q
, &bv
, &nsegs
, &seg_size
,
290 &front_seg_size
, §ors
))
300 new = bio_split(bio
, sectors
, GFP_NOIO
, bs
);
305 bio
->bi_seg_front_size
= front_seg_size
;
306 if (seg_size
> bio
->bi_seg_back_size
)
307 bio
->bi_seg_back_size
= seg_size
;
309 return do_split
? new : NULL
;
312 void blk_queue_split(struct request_queue
*q
, struct bio
**bio
)
314 struct bio
*split
, *res
;
317 switch (bio_op(*bio
)) {
319 case REQ_OP_SECURE_ERASE
:
320 split
= blk_bio_discard_split(q
, *bio
, &q
->bio_split
, &nsegs
);
322 case REQ_OP_WRITE_ZEROES
:
323 split
= blk_bio_write_zeroes_split(q
, *bio
, &q
->bio_split
, &nsegs
);
325 case REQ_OP_WRITE_SAME
:
326 split
= blk_bio_write_same_split(q
, *bio
, &q
->bio_split
, &nsegs
);
329 split
= blk_bio_segment_split(q
, *bio
, &q
->bio_split
, &nsegs
);
333 /* physical segments can be figured out during splitting */
334 res
= split
? split
: *bio
;
335 res
->bi_phys_segments
= nsegs
;
336 bio_set_flag(res
, BIO_SEG_VALID
);
339 /* there isn't chance to merge the splitted bio */
340 split
->bi_opf
|= REQ_NOMERGE
;
343 * Since we're recursing into make_request here, ensure
344 * that we mark this bio as already having entered the queue.
345 * If not, and the queue is going away, we can get stuck
346 * forever on waiting for the queue reference to drop. But
347 * that will never happen, as we're already holding a
350 bio_set_flag(*bio
, BIO_QUEUE_ENTERED
);
352 bio_chain(split
, *bio
);
353 trace_block_split(q
, split
, (*bio
)->bi_iter
.bi_sector
);
354 generic_make_request(*bio
);
358 EXPORT_SYMBOL(blk_queue_split
);
360 static unsigned int __blk_recalc_rq_segments(struct request_queue
*q
,
363 struct bio_vec bv
, bvprv
= { NULL
};
365 unsigned int seg_size
, nr_phys_segs
;
366 unsigned front_seg_size
= bio
->bi_seg_front_size
;
367 struct bio
*fbio
, *bbio
;
368 struct bvec_iter iter
;
373 switch (bio_op(bio
)) {
375 case REQ_OP_SECURE_ERASE
:
376 case REQ_OP_WRITE_ZEROES
:
378 case REQ_OP_WRITE_SAME
:
386 bio_for_each_bvec(bv
, bio
, iter
) {
388 if (seg_size
+ bv
.bv_len
389 > queue_max_segment_size(q
))
391 if (!biovec_phys_mergeable(q
, &bvprv
, &bv
))
394 seg_size
+= bv
.bv_len
;
401 bvec_split_segs(q
, &bv
, &nr_phys_segs
, &seg_size
,
402 &front_seg_size
, NULL
);
407 fbio
->bi_seg_front_size
= front_seg_size
;
408 if (seg_size
> bbio
->bi_seg_back_size
)
409 bbio
->bi_seg_back_size
= seg_size
;
414 void blk_recalc_rq_segments(struct request
*rq
)
416 rq
->nr_phys_segments
= __blk_recalc_rq_segments(rq
->q
, rq
->bio
);
419 void blk_recount_segments(struct request_queue
*q
, struct bio
*bio
)
421 struct bio
*nxt
= bio
->bi_next
;
424 bio
->bi_phys_segments
= __blk_recalc_rq_segments(q
, bio
);
427 bio_set_flag(bio
, BIO_SEG_VALID
);
430 static int blk_phys_contig_segment(struct request_queue
*q
, struct bio
*bio
,
433 struct bio_vec end_bv
= { NULL
}, nxt_bv
;
435 if (bio
->bi_seg_back_size
+ nxt
->bi_seg_front_size
>
436 queue_max_segment_size(q
))
439 if (!bio_has_data(bio
))
442 bio_get_last_bvec(bio
, &end_bv
);
443 bio_get_first_bvec(nxt
, &nxt_bv
);
445 return biovec_phys_mergeable(q
, &end_bv
, &nxt_bv
);
448 static struct scatterlist
*blk_next_sg(struct scatterlist
**sg
,
449 struct scatterlist
*sglist
)
455 * If the driver previously mapped a shorter list, we could see a
456 * termination bit prematurely unless it fully inits the sg table
457 * on each mapping. We KNOW that there must be more entries here
458 * or the driver would be buggy, so force clear the termination bit
459 * to avoid doing a full sg_init_table() in drivers for each command.
465 static unsigned blk_bvec_map_sg(struct request_queue
*q
,
466 struct bio_vec
*bvec
, struct scatterlist
*sglist
,
467 struct scatterlist
**sg
)
469 unsigned nbytes
= bvec
->bv_len
;
470 unsigned nsegs
= 0, total
= 0, offset
= 0;
477 *sg
= blk_next_sg(sg
, sglist
);
479 seg_size
= get_max_segment_size(q
, bvec
->bv_offset
+ total
);
480 seg_size
= min(nbytes
, seg_size
);
482 offset
= (total
+ bvec
->bv_offset
) % PAGE_SIZE
;
483 idx
= (total
+ bvec
->bv_offset
) / PAGE_SIZE
;
484 pg
= nth_page(bvec
->bv_page
, idx
);
486 sg_set_page(*sg
, pg
, seg_size
, offset
);
497 __blk_segment_map_sg(struct request_queue
*q
, struct bio_vec
*bvec
,
498 struct scatterlist
*sglist
, struct bio_vec
*bvprv
,
499 struct scatterlist
**sg
, int *nsegs
)
502 int nbytes
= bvec
->bv_len
;
505 if ((*sg
)->length
+ nbytes
> queue_max_segment_size(q
))
507 if (!biovec_phys_mergeable(q
, bvprv
, bvec
))
510 (*sg
)->length
+= nbytes
;
513 (*nsegs
) += blk_bvec_map_sg(q
, bvec
, sglist
, sg
);
518 static inline int __blk_bvec_map_sg(struct request_queue
*q
, struct bio_vec bv
,
519 struct scatterlist
*sglist
, struct scatterlist
**sg
)
522 sg_set_page(*sg
, bv
.bv_page
, bv
.bv_len
, bv
.bv_offset
);
526 static int __blk_bios_map_sg(struct request_queue
*q
, struct bio
*bio
,
527 struct scatterlist
*sglist
,
528 struct scatterlist
**sg
)
530 struct bio_vec bvec
, bvprv
= { NULL
};
531 struct bvec_iter iter
;
535 bio_for_each_bvec(bvec
, bio
, iter
)
536 __blk_segment_map_sg(q
, &bvec
, sglist
, &bvprv
, sg
,
543 * map a request to scatterlist, return number of sg entries setup. Caller
544 * must make sure sg can hold rq->nr_phys_segments entries
546 int blk_rq_map_sg(struct request_queue
*q
, struct request
*rq
,
547 struct scatterlist
*sglist
)
549 struct scatterlist
*sg
= NULL
;
552 if (rq
->rq_flags
& RQF_SPECIAL_PAYLOAD
)
553 nsegs
= __blk_bvec_map_sg(q
, rq
->special_vec
, sglist
, &sg
);
554 else if (rq
->bio
&& bio_op(rq
->bio
) == REQ_OP_WRITE_SAME
)
555 nsegs
= __blk_bvec_map_sg(q
, bio_iovec(rq
->bio
), sglist
, &sg
);
557 nsegs
= __blk_bios_map_sg(q
, rq
->bio
, sglist
, &sg
);
559 if (unlikely(rq
->rq_flags
& RQF_COPY_USER
) &&
560 (blk_rq_bytes(rq
) & q
->dma_pad_mask
)) {
561 unsigned int pad_len
=
562 (q
->dma_pad_mask
& ~blk_rq_bytes(rq
)) + 1;
564 sg
->length
+= pad_len
;
565 rq
->extra_len
+= pad_len
;
568 if (q
->dma_drain_size
&& q
->dma_drain_needed(rq
)) {
569 if (op_is_write(req_op(rq
)))
570 memset(q
->dma_drain_buffer
, 0, q
->dma_drain_size
);
574 sg_set_page(sg
, virt_to_page(q
->dma_drain_buffer
),
576 ((unsigned long)q
->dma_drain_buffer
) &
579 rq
->extra_len
+= q
->dma_drain_size
;
586 * Something must have been wrong if the figured number of
587 * segment is bigger than number of req's physical segments
589 WARN_ON(nsegs
> blk_rq_nr_phys_segments(rq
));
593 EXPORT_SYMBOL(blk_rq_map_sg
);
595 static inline int ll_new_hw_segment(struct request_queue
*q
,
599 int nr_phys_segs
= bio_phys_segments(q
, bio
);
601 if (req
->nr_phys_segments
+ nr_phys_segs
> queue_max_segments(q
))
604 if (blk_integrity_merge_bio(q
, req
, bio
) == false)
608 * This will form the start of a new hw segment. Bump both
611 req
->nr_phys_segments
+= nr_phys_segs
;
615 req_set_nomerge(q
, req
);
619 int ll_back_merge_fn(struct request_queue
*q
, struct request
*req
,
622 if (req_gap_back_merge(req
, bio
))
624 if (blk_integrity_rq(req
) &&
625 integrity_req_gap_back_merge(req
, bio
))
627 if (blk_rq_sectors(req
) + bio_sectors(bio
) >
628 blk_rq_get_max_sectors(req
, blk_rq_pos(req
))) {
629 req_set_nomerge(q
, req
);
632 if (!bio_flagged(req
->biotail
, BIO_SEG_VALID
))
633 blk_recount_segments(q
, req
->biotail
);
634 if (!bio_flagged(bio
, BIO_SEG_VALID
))
635 blk_recount_segments(q
, bio
);
637 return ll_new_hw_segment(q
, req
, bio
);
640 int ll_front_merge_fn(struct request_queue
*q
, struct request
*req
,
644 if (req_gap_front_merge(req
, bio
))
646 if (blk_integrity_rq(req
) &&
647 integrity_req_gap_front_merge(req
, bio
))
649 if (blk_rq_sectors(req
) + bio_sectors(bio
) >
650 blk_rq_get_max_sectors(req
, bio
->bi_iter
.bi_sector
)) {
651 req_set_nomerge(q
, req
);
654 if (!bio_flagged(bio
, BIO_SEG_VALID
))
655 blk_recount_segments(q
, bio
);
656 if (!bio_flagged(req
->bio
, BIO_SEG_VALID
))
657 blk_recount_segments(q
, req
->bio
);
659 return ll_new_hw_segment(q
, req
, bio
);
662 static bool req_attempt_discard_merge(struct request_queue
*q
, struct request
*req
,
663 struct request
*next
)
665 unsigned short segments
= blk_rq_nr_discard_segments(req
);
667 if (segments
>= queue_max_discard_segments(q
))
669 if (blk_rq_sectors(req
) + bio_sectors(next
->bio
) >
670 blk_rq_get_max_sectors(req
, blk_rq_pos(req
)))
673 req
->nr_phys_segments
= segments
+ blk_rq_nr_discard_segments(next
);
676 req_set_nomerge(q
, req
);
680 static int ll_merge_requests_fn(struct request_queue
*q
, struct request
*req
,
681 struct request
*next
)
683 int total_phys_segments
;
684 unsigned int seg_size
=
685 req
->biotail
->bi_seg_back_size
+ next
->bio
->bi_seg_front_size
;
687 if (req_gap_back_merge(req
, next
->bio
))
691 * Will it become too large?
693 if ((blk_rq_sectors(req
) + blk_rq_sectors(next
)) >
694 blk_rq_get_max_sectors(req
, blk_rq_pos(req
)))
697 total_phys_segments
= req
->nr_phys_segments
+ next
->nr_phys_segments
;
698 if (blk_phys_contig_segment(q
, req
->biotail
, next
->bio
)) {
699 if (req
->nr_phys_segments
== 1)
700 req
->bio
->bi_seg_front_size
= seg_size
;
701 if (next
->nr_phys_segments
== 1)
702 next
->biotail
->bi_seg_back_size
= seg_size
;
703 total_phys_segments
--;
706 if (total_phys_segments
> queue_max_segments(q
))
709 if (blk_integrity_merge_rq(q
, req
, next
) == false)
713 req
->nr_phys_segments
= total_phys_segments
;
718 * blk_rq_set_mixed_merge - mark a request as mixed merge
719 * @rq: request to mark as mixed merge
722 * @rq is about to be mixed merged. Make sure the attributes
723 * which can be mixed are set in each bio and mark @rq as mixed
726 void blk_rq_set_mixed_merge(struct request
*rq
)
728 unsigned int ff
= rq
->cmd_flags
& REQ_FAILFAST_MASK
;
731 if (rq
->rq_flags
& RQF_MIXED_MERGE
)
735 * @rq will no longer represent mixable attributes for all the
736 * contained bios. It will just track those of the first one.
737 * Distributes the attributs to each bio.
739 for (bio
= rq
->bio
; bio
; bio
= bio
->bi_next
) {
740 WARN_ON_ONCE((bio
->bi_opf
& REQ_FAILFAST_MASK
) &&
741 (bio
->bi_opf
& REQ_FAILFAST_MASK
) != ff
);
744 rq
->rq_flags
|= RQF_MIXED_MERGE
;
747 static void blk_account_io_merge(struct request
*req
)
749 if (blk_do_io_stat(req
)) {
750 struct hd_struct
*part
;
755 part_dec_in_flight(req
->q
, part
, rq_data_dir(req
));
762 * Two cases of handling DISCARD merge:
763 * If max_discard_segments > 1, the driver takes every bio
764 * as a range and send them to controller together. The ranges
765 * needn't to be contiguous.
766 * Otherwise, the bios/requests will be handled as same as
767 * others which should be contiguous.
769 static inline bool blk_discard_mergable(struct request
*req
)
771 if (req_op(req
) == REQ_OP_DISCARD
&&
772 queue_max_discard_segments(req
->q
) > 1)
777 static enum elv_merge
blk_try_req_merge(struct request
*req
,
778 struct request
*next
)
780 if (blk_discard_mergable(req
))
781 return ELEVATOR_DISCARD_MERGE
;
782 else if (blk_rq_pos(req
) + blk_rq_sectors(req
) == blk_rq_pos(next
))
783 return ELEVATOR_BACK_MERGE
;
785 return ELEVATOR_NO_MERGE
;
789 * For non-mq, this has to be called with the request spinlock acquired.
790 * For mq with scheduling, the appropriate queue wide lock should be held.
792 static struct request
*attempt_merge(struct request_queue
*q
,
793 struct request
*req
, struct request
*next
)
795 if (!rq_mergeable(req
) || !rq_mergeable(next
))
798 if (req_op(req
) != req_op(next
))
801 if (rq_data_dir(req
) != rq_data_dir(next
)
802 || req
->rq_disk
!= next
->rq_disk
)
805 if (req_op(req
) == REQ_OP_WRITE_SAME
&&
806 !blk_write_same_mergeable(req
->bio
, next
->bio
))
810 * Don't allow merge of different write hints, or for a hint with
813 if (req
->write_hint
!= next
->write_hint
)
816 if (req
->ioprio
!= next
->ioprio
)
820 * If we are allowed to merge, then append bio list
821 * from next to rq and release next. merge_requests_fn
822 * will have updated segment counts, update sector
823 * counts here. Handle DISCARDs separately, as they
824 * have separate settings.
827 switch (blk_try_req_merge(req
, next
)) {
828 case ELEVATOR_DISCARD_MERGE
:
829 if (!req_attempt_discard_merge(q
, req
, next
))
832 case ELEVATOR_BACK_MERGE
:
833 if (!ll_merge_requests_fn(q
, req
, next
))
841 * If failfast settings disagree or any of the two is already
842 * a mixed merge, mark both as mixed before proceeding. This
843 * makes sure that all involved bios have mixable attributes
846 if (((req
->rq_flags
| next
->rq_flags
) & RQF_MIXED_MERGE
) ||
847 (req
->cmd_flags
& REQ_FAILFAST_MASK
) !=
848 (next
->cmd_flags
& REQ_FAILFAST_MASK
)) {
849 blk_rq_set_mixed_merge(req
);
850 blk_rq_set_mixed_merge(next
);
854 * At this point we have either done a back merge or front merge. We
855 * need the smaller start_time_ns of the merged requests to be the
856 * current request for accounting purposes.
858 if (next
->start_time_ns
< req
->start_time_ns
)
859 req
->start_time_ns
= next
->start_time_ns
;
861 req
->biotail
->bi_next
= next
->bio
;
862 req
->biotail
= next
->biotail
;
864 req
->__data_len
+= blk_rq_bytes(next
);
866 if (!blk_discard_mergable(req
))
867 elv_merge_requests(q
, req
, next
);
870 * 'next' is going away, so update stats accordingly
872 blk_account_io_merge(next
);
875 * ownership of bio passed from next to req, return 'next' for
882 struct request
*attempt_back_merge(struct request_queue
*q
, struct request
*rq
)
884 struct request
*next
= elv_latter_request(q
, rq
);
887 return attempt_merge(q
, rq
, next
);
892 struct request
*attempt_front_merge(struct request_queue
*q
, struct request
*rq
)
894 struct request
*prev
= elv_former_request(q
, rq
);
897 return attempt_merge(q
, prev
, rq
);
902 int blk_attempt_req_merge(struct request_queue
*q
, struct request
*rq
,
903 struct request
*next
)
905 struct request
*free
;
907 free
= attempt_merge(q
, rq
, next
);
909 blk_put_request(free
);
916 bool blk_rq_merge_ok(struct request
*rq
, struct bio
*bio
)
918 if (!rq_mergeable(rq
) || !bio_mergeable(bio
))
921 if (req_op(rq
) != bio_op(bio
))
924 /* different data direction or already started, don't merge */
925 if (bio_data_dir(bio
) != rq_data_dir(rq
))
928 /* must be same device */
929 if (rq
->rq_disk
!= bio
->bi_disk
)
932 /* only merge integrity protected bio into ditto rq */
933 if (blk_integrity_merge_bio(rq
->q
, rq
, bio
) == false)
936 /* must be using the same buffer */
937 if (req_op(rq
) == REQ_OP_WRITE_SAME
&&
938 !blk_write_same_mergeable(rq
->bio
, bio
))
942 * Don't allow merge of different write hints, or for a hint with
945 if (rq
->write_hint
!= bio
->bi_write_hint
)
948 if (rq
->ioprio
!= bio_prio(bio
))
954 enum elv_merge
blk_try_merge(struct request
*rq
, struct bio
*bio
)
956 if (blk_discard_mergable(rq
))
957 return ELEVATOR_DISCARD_MERGE
;
958 else if (blk_rq_pos(rq
) + blk_rq_sectors(rq
) == bio
->bi_iter
.bi_sector
)
959 return ELEVATOR_BACK_MERGE
;
960 else if (blk_rq_pos(rq
) - bio_sectors(bio
) == bio
->bi_iter
.bi_sector
)
961 return ELEVATOR_FRONT_MERGE
;
962 return ELEVATOR_NO_MERGE
;