// SPDX-License-Identifier: GPL-2.0
/*
* Functions related to segment and merge handling
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/bio.h>
#include <linux/blkdev.h>
#include <linux/scatterlist.h>
#include <trace/events/block.h>
#include "blk.h"
/*
* Check if the two bvecs from two bios can be merged to one segment. If yes,
* no need to check gap between the two bios since the 1st bio and the 1st bvec
* in the 2nd bio can be handled in one segment.
*/
static inline bool bios_segs_mergeable(struct request_queue *q,
struct bio *prev, struct bio_vec *prev_last_bv,
struct bio_vec *next_first_bv)
{
if (!biovec_phys_mergeable(q, prev_last_bv, next_first_bv))
return false;
if (prev->bi_seg_back_size + next_first_bv->bv_len >
queue_max_segment_size(q))
return false;
return true;
}
static inline bool bio_will_gap(struct request_queue *q,
struct request *prev_rq, struct bio *prev, struct bio *next)
{
struct bio_vec pb, nb;
if (!bio_has_data(prev) || !queue_virt_boundary(q))
return false;
/*
* Don't merge if the 1st bio starts with non-zero offset, otherwise it
* is quite difficult to respect the sg gap limit. We work hard to
* merge a huge number of small single bios in case of mkfs.
*/
if (prev_rq)
bio_get_first_bvec(prev_rq->bio, &pb);
else
bio_get_first_bvec(prev, &pb);
if (pb.bv_offset & queue_virt_boundary(q))
return true;
/*
* We don't need to worry about the situation that the merged segment
* ends in unaligned virt boundary:
*
* - if 'pb' ends aligned, the merged segment ends aligned
* - if 'pb' ends unaligned, the next bio must include
* one single bvec of 'nb', otherwise the 'nb' can't
* merge with 'pb'
*/
bio_get_last_bvec(prev, &pb);
bio_get_first_bvec(next, &nb);
if (bios_segs_mergeable(q, prev, &pb, &nb))
return false;
return __bvec_gap_to_prev(q, &pb, nb.bv_offset);
}
static inline bool req_gap_back_merge(struct request *req, struct bio *bio)
{
return bio_will_gap(req->q, req, req->biotail, bio);
}
static inline bool req_gap_front_merge(struct request *req, struct bio *bio)
{
return bio_will_gap(req->q, NULL, bio, req->bio);
}
static struct bio *blk_bio_discard_split(struct request_queue *q,
struct bio *bio,
struct bio_set *bs,
unsigned *nsegs)
{
unsigned int max_discard_sectors, granularity;
int alignment;
sector_t tmp;
unsigned split_sectors;
*nsegs = 1;
/* Zero-sector (unknown) and one-sector granularities are the same. */
granularity = max(q->limits.discard_granularity >> 9, 1U);
max_discard_sectors = min(q->limits.max_discard_sectors,
bio_allowed_max_sectors(q));
max_discard_sectors -= max_discard_sectors % granularity;
if (unlikely(!max_discard_sectors)) {
/* XXX: warn */
return NULL;
}
if (bio_sectors(bio) <= max_discard_sectors)
return NULL;
split_sectors = max_discard_sectors;
/*
* If the next starting sector would be misaligned, stop the discard at
* the previous aligned sector.
*/
alignment = (q->limits.discard_alignment >> 9) % granularity;
tmp = bio->bi_iter.bi_sector + split_sectors - alignment;
tmp = sector_div(tmp, granularity);
if (split_sectors > tmp)
split_sectors -= tmp;
return bio_split(bio, split_sectors, GFP_NOIO, bs);
}
static struct bio *blk_bio_write_zeroes_split(struct request_queue *q,
struct bio *bio, struct bio_set *bs, unsigned *nsegs)
{
*nsegs = 1;
if (!q->limits.max_write_zeroes_sectors)
return NULL;
if (bio_sectors(bio) <= q->limits.max_write_zeroes_sectors)
return NULL;
return bio_split(bio, q->limits.max_write_zeroes_sectors, GFP_NOIO, bs);
}
static struct bio *blk_bio_write_same_split(struct request_queue *q,
struct bio *bio,
struct bio_set *bs,
unsigned *nsegs)
{
*nsegs = 1;
if (!q->limits.max_write_same_sectors)
return NULL;
if (bio_sectors(bio) <= q->limits.max_write_same_sectors)
return NULL;
return bio_split(bio, q->limits.max_write_same_sectors, GFP_NOIO, bs);
}
static inline unsigned get_max_io_size(struct request_queue *q,
struct bio *bio)
{
unsigned sectors = blk_max_size_offset(q, bio->bi_iter.bi_sector);
unsigned mask