// 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/blk-integrity.h>
#include <linux/scatterlist.h>
#include <linux/part_stat.h>
#include <linux/blk-cgroup.h>
#include <trace/events/block.h>
#include "blk.h"
#include "blk-mq-sched.h"
#include "blk-rq-qos.h"
#include "blk-throttle.h"
static inline void bio_get_first_bvec(struct bio *bio, struct bio_vec *bv)
{
*bv = mp_bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter);
}
static inline void bio_get_last_bvec(struct bio *bio, struct bio_vec *bv)
{
struct bvec_iter iter = bio->bi_iter;
int idx;
bio_get_first_bvec(bio, bv);
if (bv->bv_len == bio->bi_iter.bi_size)
return; /* this bio only has a single bvec */
bio_advance_iter(bio, &iter, iter.bi_size);
if (!iter.bi_bvec_done)
idx = iter.bi_idx - 1;
else /* in the middle of bvec */
idx = iter.bi_idx;
*bv = bio->bi_io_vec[idx];
/*
* iter.bi_bvec_done records actual length of the last bvec
* if this bio ends in the middle of one io vector
*/
if (iter.bi_bvec_done)
bv->bv_len = iter.bi_bvec_done;
}
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 (biovec_phys_mergeable(q, &pb, &nb))
return false;
return __bvec_gap_to_prev(&q->limits, &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);
}
/*
* The max size one bio can handle is UINT_MAX becasue bvec_iter.bi_size
* is defined as 'unsigned int', meantime it has to be aligned to with the
* logical block size, which is the minimum accepted unit by hardware.
*/
static unsigned int bio_allowed_max_sectors(const struct queue_limits *lim)
{
return round_down(UINT_MAX, lim->logical_block_size) >> SECTOR_SHIFT;
}
static struct bio *bio_submit_split(struct bio *bio, int split_sectors)
{
if (unlikely(split_sectors < 0)) {
bio->bi_status = errno_to_blk_status(split_sectors);
bio_endio(bio);
return NULL;
}
if (split_sectors) {
struct bio *split;
split = bio_split(bio, split_sectors, GFP_NOIO,
&bio->bi_bdev->bd_disk->bio_split);
split->bi_opf |= REQ_NOMERGE;
blkcg_bio_issue_init(split);
bio_chain(split, bio);
trace_block_split(split, bio->bi_iter.bi_sector);
WARN_ON_ONCE(bio_zone_write_plugging(bio));
submit_bio_noacct(bio);
return split;
}
return bio;
}
struct bio *bio_split_discard(struct bio *bio, const struct queue_limits *lim,
unsigned *nsegs)
{
unsigned int max_discard_sectors, granularity;
sector_t tmp;
unsigned split_sectors;
*nsegs = 1;
granularity = max(lim->discard_granularity >> 9, 1U);
max_discard_sectors =
min(lim->max_discard_sectors, bio_allowed_max_sectors(lim));
max_discard_sectors -= max_discard_sectors % granularity;
if (unlikely(!max_discard_sectors))
return bio;
if (bio_sectors(bio) <= max_discard_sectors)
return bio;
split_sectors = max_discard_sectors;
/*
* If the next starting sector would be misaligned, stop the discard at
* the previous aligned sector.
*/
tmp = bio->bi_iter.bi_sector + split_sectors -
((lim->discard_alignment >> 9) % granularity);
tmp = sector_div(tmp, granularity);
if (split_sectors > tmp)
split_sectors -= tmp;
return bio_submit_split(bio, split_sectors);
}
struct bio *bio_split_write_zeroes(struct bio *bio,
const struct queue_limits *lim, unsigned *nsegs)
{
*nsegs = 0;
if (!lim->max_write_zeroes_sectors)
return bio;
if (bio_sectors(bio) <= lim->max_write_zeroes_sectors)
return bio;
return bio_submit_split(bio, lim->max_write_zeroes_sectors);
}
static inline unsigned int blk_boundary_sectors(const struct queue_limits *lim,
bool is_atomic)
{
/*
* chunk_sectors must be a multiple of atomic_write_boundary_sectors if
* both non-zero.
*/
if (is_atomic && lim->atomic_write_boundary_sectors)
return lim->atomic_write_boundary_sectors;
return lim->chunk_sectors;
}
/*
* Return the maximum number of sectors from the start of a bio that may be
* submitted as a single request to a block device. If enough sectors remain,
* align the end to the physical block size. Otherwise align the end to the
* logical block size. This approach minimizes the number of non-aligned
* requests that are submitted to a block device if the start of a bio is not
* aligned to a physical block boundary.
*/
static inline unsigned get_max_io_size(struct bio *bio,
const struct queue_limits *lim)
{
unsigned pbs = lim->physical_block_size >> SECTOR_SHIFT;
unsigned lbs = lim->logical_block_size >> SECTOR_SHIFT;
bool is_atomic = bio->bi_opf & REQ_ATOMIC;
unsigned boundary_sectors = blk_boundary_sectors(lim, is_atomic);
unsigned max_sectors, start, end;
/*
* We ignore lim->max_sectors for atomic writes because it may less
* than the actual bio size, which we cannot tolerate.
*/
if (is_atomic)
max_sectors = lim->atomic_write_max_sectors;
else
max_sectors = lim->max_sectors;
if (boundary_sectors) {
max_sectors = min(max_sectors,
blk_boundary_sectors_left(bio->bi_iter.bi_sector,
boundary_sectors));
}
start = bio->bi_iter.bi_sector & (pbs - 1);
end = (start + max_sectors) & ~(pbs - 1);
if (end > start)
return end - start;
return max_sectors & ~(lbs - 1);
}
/**
* get_max_segment_size() - maximum number of bytes to add as a single segment
* @lim: Request queue limits.
* @paddr: address of the range to add
* @len: maximum length available to add at @paddr
*
* Returns the maximum number of bytes of the range starting at @paddr that can
* be added to a single segment.
*/
static inline unsigned get_max_segment_size(const struct queue_limits *lim,
phys_addr_t paddr, unsigned int len)
{
/*
* Prevent an overflow if mask = ULONG_MAX and offset = 0 by adding 1
* after having calculated the minimum.
*/
return min_t(unsigned long, len,
min(lim->seg_boundary_mask - (lim->seg_boundary_mask & paddr),
(unsigned long)lim->max_segment_size - 1) + 1);
}
/**
* bvec_split_segs - verify whether or not a bvec should be split in the middle
* @lim: [in] queue limits to split based on
* @bv: [in] bvec to examine
* @nsegs: [in,out] Number of segments in the bio being built. Incremented
* by the number of segments from @bv that may be appended to that
* bio without exceeding @max_segs
* @bytes: [in,out] Number of bytes in the bio being built. Incremented
* by the number of bytes from @bv that may be appended to that
* bio without exceeding @max_bytes
* @max_segs: [in] upper bound for *@nsegs
* @max_bytes: [in] upper bound for *@bytes
*
* When splitting a bio, it can happen that a bvec is encountered that is too
* big to fit in a single segment and hence that it has to be split in the
* middle. This function verifies whether or not that should happen. The value
* %true is returned if and only if appending the entire @bv to a bio with
* *@nsegs segments and *@sectors sectors would make that bio unacceptable for
* the block driver.
*/
static bool bvec_split_segs(const struct queue_limits *lim,
const struct bio_vec *bv, unsigned *nsegs, unsigned *bytes,
unsigned max_segs, unsigned max_bytes)
{
unsigned max_len = min(max_bytes, UINT_MAX) - *bytes;
unsigned len = min(bv->bv_len, max_len);
unsigned total_len = 0;
unsigned seg_size = 0;
while (len && *nsegs < max_segs) {
seg_size = get_max_segment_size(lim, bvec_phys(bv) + total_len, len);
(*nsegs)++;
total_len += seg_size;
len -= seg_size;
if ((bv->bv_offset + total_len) & lim->virt_boundary_mask)
break;
}
*bytes += total_len;
/* tell the caller to split the bvec if it is too big to fit */
return len > 0 || bv->bv_len > max_len;
}
/**
* bio_split_rw_at - check if and where to split a read/write bio
* @bio: [in] bio to be split
* @lim: [in] queue limits to split based on
* @segs: [out] number of segments in the bio with the first half of the sectors
* @max_bytes: [in] maximum number of bytes per bio
*
* Find out if @bio needs to be split to fit the queue limits in @lim and a
* maximum size of @max_bytes. Returns a negative error number if @bio can't be
* split, 0 if the bio doesn't have to be split, or a positive sector offset if
* @bio needs to be split.
*/
int bio_split_rw_at(struct bio *bio, const struct queue_limits *lim,
unsigned *segs, unsigned max_bytes)
{
struct bio_vec bv, bvprv, *bvprvp = NULL;
struct bvec_iter iter;
unsigned nsegs = 0, bytes = 0;
bio_for_each_bvec(bv, bio, iter) {
/*
* If the queue doesn't support SG gaps and adding this
* offset would create a gap, disallow it.
*/
if (bvprvp && bvec_gap_to_prev(lim, bvprvp, bv.bv_offset))
goto split;
if (nsegs < lim->max_segments &&
bytes + bv.bv_len <= max_bytes &&
bv.bv_offset + bv.bv_len <= PAGE_SIZE) {
nsegs++;
bytes += bv.bv_len;
} else {
if (bvec_split_segs(lim, &bv, &nsegs, &bytes,
lim->max_segments, max_bytes))
goto split;
}
bvprv = bv;
bvprvp = &bvprv;
}
*segs = nsegs;
return 0;
split:
if (bio->bi_opf & REQ_ATOMIC)
return -EINVAL;
/*
* We can't sanely support splitting for a REQ_NOWAIT bio. End it
* with EAGAIN if splitting is required and return an error pointer.
*/
if (bio->bi_opf & REQ_NOWAIT)
return -EAGAIN;
*segs = nsegs;
/*
* Individual bvecs might not be logical block aligned. Round down the
* split size so that each bio is properly block size aligned, even if
* we do not use the full hardware limits.
*/
bytes = ALIGN_DOWN(bytes, lim->logical_block_size);
/*
* Bio splitting may cause subtle trouble such as hang when doing sync
* iopoll in direct IO routine. Given performance gain of iopoll for
* big IO can be trival, disable iopoll when split needed.
*/
bio_clear_polled(bio);
return bytes >> SECTOR_SHIFT;
}
EXPORT_SYMBOL_GPL(bio_split_rw_at);
struct bio *bio_split_rw(struct bio *bio, const struct queue_limits *lim,
unsigned *nr_segs)
{
return bio_submit_split(bio,
bio_split_rw_at(bio, lim, nr_segs,
get_max_io_size(bio, lim) << SECTOR_SHIFT));
}
/*
* REQ_OP_ZONE_APPEND bios must never be split by the block layer.
*
* But we want the nr_segs calculation provided by bio_split_rw_at, and having
* a good sanity check that the submitter built the bio correctly is nice to
* have as well.
*/
struct bio *bio_split_zone_append(struct bio *bio,
const struct queue_limits *lim, unsigned *nr_segs)
{
unsigned int max_sectors = queue_limits_max_zone_append_sectors(lim);
int split_sectors;
split_sectors = bio_split_rw_at(bio, lim, nr_segs,
max_sectors << SECTOR_SHIFT);
if (WARN_ON_ONCE(split_sectors > 0))
split_sectors = -EINVAL;
return bio_submit_split(bio, split_sectors);
}
/**
* bio_split_to_limits - split a bio to fit the queue limits
* @bio: bio to be split
*
* Check if @bio needs splitting based on the queue limits of @bio->bi_bdev, and
* if so split off a bio fitting the limits from the beginning of @bio and
* return it. @bio is shortened to the remainder and re-submitted.
*
* The split bio is allocated from @q->bio_split, which is provided by the
* block layer.
*/
struct bio *bio_split_to_limits(struct bio *bio)
{
const struct queue_limits *lim = &bdev_get_queue(bio->bi_bdev)->limits;
unsigned int nr_segs;
return __bio_split_to_limits(bio, lim, &nr_segs);
}
EXPORT_SYMBOL(bio_split_to_limits);
unsigned int blk_recalc_rq_segments(struct request *rq)
{
unsigned int nr_phys_segs = 0;
unsigned int bytes = 0;
struct req_iterator iter;
struct bio_vec bv;
if (!rq->bio)
return 0;
switch (bio_op(rq->bio)) {
case REQ_OP_DISCARD:
case REQ_OP_SECURE_ERASE:
if (queue_max_discard_segments(rq->q) > 1) {
struct bio *bio = rq->bio;
for_each_bio(bio)
nr_phys_segs++;
return nr_phys_segs;
}
return 1;
case REQ_OP_WRITE_ZEROES:
return 0;
default:
break;
}
rq_for_each_bvec(bv, rq, iter)
bvec_split_segs(&rq->q->limits, &bv, &nr_phys_segs, &bytes,
UINT_MAX, UINT_MAX);
return nr_phys_segs;
}
static inline struct scatterlist *blk_next_sg(struct scatterlist **sg,
struct scatterlist *sglist)
{
if (!*sg)
return sglist;
/*
* If the driver previously mapped a shorter list, we could see a
* termination bit prematurely unless it fully inits the sg table
* on each mapping. We KNOW that there must be more entries here
* or the driver would be buggy, so force clear the termination bit
* to avoid doing a full sg_init_table() in drivers for each command.
*/
sg_unmark_end(*sg);
return sg_next(*sg);
}
static unsigned blk_bvec_map_sg(struct request_queue *q,
struct bio_vec *bvec, struct scatterlist *sglist,
struct scatterlist **sg)
{
unsigned nbytes = bvec->bv_len;
unsigned nsegs = 0, total = 0;
while (nbytes > 0) {
unsigned offset = bvec->bv_offset + total;
unsigned len = get_max_segment_size(&q->limits,
bvec_phys(bvec) + total, nbytes);
struct page *page = bvec->bv_page;
/*
* Unfortunately a fair number of drivers barf on scatterlists
* that have an offset larger than PAGE_SIZE, despite other
* subsystems dealing with that invariant just fine. For now
* stick to the legacy format where we never present those from
* the block layer, but the code below should be removed once
* these offenders (mostly MMC/SD drivers) are fixed.
*/
page += (offset >> PAGE_SHIFT);
offset &= ~PAGE_MASK;
*sg = blk_next_sg(sg, sglist);
sg_set_page(*sg, page, len, offset);
total += len;
nbytes -= len;
nsegs++;
}
return nsegs;
}
static inline int __blk_bvec_map_sg(struct bio_vec bv,
struct scatterlist *sglist, struct scatterlist **sg)
{
*sg = blk_next_sg(sg, sglist);
sg_set_page(*sg, bv.bv_page, bv.bv_len, bv.bv_offset);
return 1;
}
/* only try to merge bvecs into one sg if they are from two bios */
static inline bool
__blk_segment_map_sg_merge(struct request_queue *q, struct bio_vec *bvec,
struct bio_vec *bvprv, struct scatterlist **sg)
{
int nbytes = bvec->bv_len;
if (!*sg)
return false;
if ((*sg)->length + nbytes > queue_max_segment_size(q))
return false;
if (!biovec_phys_mergeable(q, bvprv, bvec))
return false;
(*sg)->length += nbytes;
return true;
}
static int __blk_bios_map_sg(struct request_queue *q, struct bio *bio,
struct scatterlist *sglist,
struct scatterlist **sg)
{
struct bio_vec bvec, bvprv = { NULL };
struct bvec_iter iter;
int nsegs = 0;
bool new_bio = false;
for_each_bio(bio) {
bio_for_each_bvec(bvec, bio, iter) {
/*
* Only try to merge bvecs from two bios given we
* have done bio internal merge when adding pages
* to bio
*/
if (new_bio &&
__blk_segment_map_sg_merge(q, &bvec, &bvprv, sg))
goto next_bvec;
if (bvec.bv_offset + bvec.bv_len <= PAGE_SIZE)
nsegs += __blk_bvec_map_sg(bvec, sglist, sg);
else
nsegs += blk_bvec_map_sg(q, &bvec, sglist, sg);
next_bvec:
new_bio = false;
}
if (likely(bio->bi_iter.bi_size)) {
bvprv = bvec;
new_bio = true;
}
}
return nsegs;
}
/*
* map a request to scatterlist, return number of sg entries setup. Caller
* must make sure sg can hold rq->nr_phys_segments entries
*/
int __blk_rq_map_sg(struct request_queue *q, struct request *rq,
struct scatterlist *sglist, struct scatterlist **last_sg)
{
int nsegs = 0;
if (rq->rq_flags & RQF_SPECIAL_PAYLOAD)
nsegs = __blk_bvec_map_sg(rq->special_vec, sglist, last_sg);
else if (rq->bio)
nsegs = __blk_bios_map_sg(q, rq->bio, sglist, last_sg);
if (*last_sg)
sg_mark_end(*last_sg);
/*
* Something must have been wrong if the figured number of
* segment is bigger than number of req's physical segments
*/
WARN_ON(nsegs > blk_rq_nr_phys_segments(rq));
return nsegs;
}
EXPORT_SYMBOL(__blk_rq_map_sg);
static inline unsigned int blk_rq_get_max_sectors(struct request *rq,
sector_t offset)
{
struct request_queue *q = rq->q;
struct queue_limits *lim = &q->limits;
unsigned int max_sectors, boundary_sectors;
bool is_atomic = rq->cmd_flags & REQ_ATOMIC;
if (blk_rq_is_passthrough(rq))
return q->limits.max_hw_sectors;
boundary_sectors = blk_boundary_sectors(lim, is_atomic);
max_sectors = blk_queue_get_max_sectors(rq);
if (!boundary_sectors ||
req_op(rq) == REQ_OP_DISCARD ||
req_op(rq) == REQ_OP_SECURE_ERASE)
return max_sectors;
return min(max_sectors,
blk_boundary_sectors_left(offset, boundary_sectors));
}
static inline int ll_new_hw_segment(struct request *req, struct bio *bio,
unsigned int nr_phys_segs)
{
if (!blk_cgroup_mergeable(req, bio))
goto no_merge;
if (blk_integrity_merge_bio(req->q, req, bio) == false)
goto no_merge;
/* discard request merge won't add new segment */
if (req_op(req) == REQ_OP_DISCARD)
return 1;
if (req->nr_phys_segments + nr_phys_segs > blk_rq_get_max_segments(req))
goto no_merge;
/*
* This will form the start of a new hw segment. Bump both
* counters.
*/
req->nr_phys_segments += nr_phys_segs;
if (bio_integrity(bio))
req->nr_integrity_segments += blk_rq_count_integrity_sg(req->q,
bio);
return 1;
no_merge:
req_set_nomerge(req->q, req);
return 0;
}
int ll_back_merge_fn(struct request *req, struct bio *bio, unsigned int nr_segs)
{
if (req_gap_back_merge(req, bio))
return 0;
if (blk_integrity_rq(req) &&
integrity_req_gap_back_merge(req, bio))
return 0;
if (!bio_crypt_ctx_back_mergeable(req, bio))
return 0;
if (blk_rq_sectors(req) + bio_sectors(bio) >
blk_rq_get_max_sectors(req, blk_rq_pos(req))) {
req_set_nomerge(req->q, req);
return 0;
}
return ll_new_hw_segment(req, bio, nr_segs);
}
static int ll_front_merge_fn(struct request *req, struct bio *bio,
unsigned int nr_segs)
{
if (req_gap_front_merge(req, bio))
return 0;
if (blk_integrity_rq(req) &&
integrity_req_gap_front_merge(req, bio))
return 0;
if (!bio_crypt_ctx_front_mergeable(req, bio))
return 0;
if (blk_rq_sectors(req) + bio_sectors(bio) >
blk_rq_get_max_sectors(req, bio->bi_iter.bi_sector)) {
req_set_nomerge(req->q, req);
return 0;
}
return ll_new_hw_segment(req, bio, nr_segs);
}
static bool req_attempt_discard_merge(struct request_queue *q, struct request *req,
struct request *next)
{
unsigned short segments = blk_rq_nr_discard_segments(req);
if (segments >= queue_max_discard_segments(q))
goto no_merge;
if (blk_rq_sectors(req) + bio_sectors(next->bio) >
blk_rq_get_max_sectors(req, blk_rq_pos(req)))
goto no_merge;
req->nr_phys_segments = segments + blk_rq_nr_discard_segments(next);
return true;
no_merge:
req_set_nomerge(q, req);
return false;
}
static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
struct request *next)
{
int total_phys_segments;
if (req_gap_back_merge(req, next->bio))
return 0;
/*
* Will it become too large?
*/
if ((blk_rq_sectors(req) + blk_rq_sectors(next)) >
blk_rq_get_max_sectors(req, blk_rq_pos(req)))
return 0;
total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
if (total_phys_segments > blk_rq_get_max_segments(req))
return 0;
if (!blk_cgroup_mergeable(req, next->bio))
return 0;
if (blk_integrity_merge_rq(q, req, next) == false)
return 0;
if (!bio_crypt_ctx_merge_rq(req, next))
return 0;
/* Merge is OK... */
req->nr_phys_segments = total_phys_segments;
req->nr_integrity_segments += next->nr_integrity_segments;
return 1;
}
/**
* blk_rq_set_mixed_merge - mark a request as mixed merge
* @rq: request to mark as mixed merge
*
* Description:
* @rq is about to be mixed merged. Make sure the attributes
* which can be mixed are set in each bio and mark @rq as mixed
* merged.
*/
static void blk_rq_set_mixed_merge(struct request *rq)
{
blk_opf_t ff = rq->cmd_flags & REQ_FAILFAST_MASK;
struct bio *bio;
if (rq->rq_flags & RQF_MIXED_MERGE)
return;
/*
* @rq will no longer represent mixable attributes for all the
* contained bios. It will just track those of the first one.
* Distributes the attributs to each bio.
*/
for (bio = rq->bio; bio; bio = bio->bi_next) {
WARN_ON_ONCE((bio->bi_opf & REQ_FAILFAST_MASK) &&
(bio->bi_opf & REQ_FAILFAST_MASK) != ff);
bio->bi_opf |= ff;
}
rq->rq_flags |= RQF_MIXED_MERGE;
}
static inline blk_opf_t bio_failfast(const struct bio *bio)
{
if (bio->bi_opf & REQ_RAHEAD)
return REQ_FAILFAST_MASK;
return bio->bi_opf & REQ_FAILFAST_MASK;
}
/*
* After we are marked as MIXED_MERGE, any new RA bio has to be updated
* as failfast, and request's failfast has to be updated in case of
* front merge.
*/
static inline void blk_update_mixed_merge(struct request *req,
struct bio *bio, bool front_merge)
{
if (req->rq_flags & RQF_MIXED_MERGE) {
if (bio->bi_opf & REQ_RAHEAD)
bio->bi_opf |= REQ_FAILFAST_MASK;
if (front_merge) {
req->cmd_flags &= ~REQ_FAILFAST_MASK;
req->cmd_flags |= bio->bi_opf & REQ_FAILFAST_MASK;
}
}
}
static void blk_account_io_merge_request(struct request *req)
{
if (blk_do_io_stat(req)) {
part_stat_lock();
part_stat_inc(req->part, merges[op_stat_group(req_op(req))]);
part_stat_local_dec(req->part,
in_flight[op_is_write(req_op(req))]);
part_stat_unlock();
}
}
static enum elv_merge blk_try_req_merge(struct request *req,
struct request *next)
{
if (blk_discard_mergable(req))
return ELEVATOR_DISCARD_MERGE;
else if (blk_rq_pos(req) + blk_rq_sectors(req) == blk_rq_pos(next))
return ELEVATOR_BACK_MERGE;
return ELEVATOR_NO_MERGE;
}
static bool blk_atomic_write_mergeable_rq_bio(struct request *rq,
struct bio *bio)
{
return (rq->cmd_flags & REQ_ATOMIC) == (bio->bi_opf & REQ_ATOMIC);
}
static bool blk_atomic_write_mergeable_rqs(struct request *rq,
struct request *next)
{
return (rq->cmd_flags & REQ_ATOMIC) == (next->cmd_flags & REQ_ATOMIC);
}
/*
* For non-mq, this has to be called with the request spinlock acquired.
* For mq with scheduling, the appropriate queue wide lock should be held.
*/
static struct request *attempt_merge(struct request_queue *q,
struct request *req, struct request *next)
{
if (!rq_mergeable(req) || !rq_mergeable(next))
return NULL;
if (req_op(req) != req_op(next))
return NULL;
if (rq_data_dir(req) != rq_data_dir(next))
return NULL;
/* Don't merge requests with different write hints. */
if (req->write_hint != next->write_hint)
return NULL;
if (req->ioprio != next->ioprio)
return NULL;
if (!blk_atomic_write_mergeable_rqs(req, next))
return NULL;
/*
* If we are allowed to merge, then append bio list
* from next to rq and release next. merge_requests_fn
* will have updated segment counts, update sector
* counts here. Handle DISCARDs separately, as they
* have separate settings.
*/
switch (blk_try_req_merge(req, next)) {
case ELEVATOR_DISCARD_MERGE:
if (!req_attempt_discard_merge(q, req, next))
return NULL;
break;
case ELEVATOR_BACK_MERGE:
if (!ll_merge_requests_fn(q, req, next))
return NULL;
break;
default:
return NULL;
}
/*
* If failfast settings disagree or any of the two is already
* a mixed merge, mark both as mixed before proceeding. This
* makes sure that all involved bios have mixable attributes
* set properly.
*/
if (((req->rq_flags | next->rq_flags) & RQF_MIXED_MERGE) ||
(req->cmd_flags & REQ_FAILFAST_MASK) !=
(next->cmd_flags & REQ_FAILFAST_MASK)) {
blk_rq_set_mixed_merge(req);
blk_rq_set_mixed_merge(next);
}
/*
* At this point we have either done a back merge or front merge. We
* need the smaller start_time_ns of the merged requests to be the
* current request for accounting purposes.
*/
if (next->start_time_ns < req->start_time_ns)
req->start_time_ns = next->start_time_ns;
req->biotail->bi_next = next->bio;
req->biotail = next->biotail;
req->__data_len += blk_rq_bytes(next);
if (!blk_discard_mergable(req))
elv_merge_requests(q, req, next);
blk_crypto_rq_put_keyslot(next);
/*
* 'next' is going away, so update stats accordingly
*/
blk_account_io_merge_request(next);
trace_block_rq_merge(next);
/*
* ownership of bio passed from next to req, return 'next' for
* the caller to free
*/
next->bio = NULL;
return next;
}
static struct request *attempt_back_merge(struct request_queue *q,
struct request *rq)
{
struct request *next = elv_latter_request(q, rq);
if (next)
return attempt_merge(q, rq, next);
return NULL;
}
static struct request *attempt_front_merge(struct request_queue *q,
struct request *rq)
{
struct request *prev = elv_former_request(q, rq);
if (prev)
return attempt_merge(q, prev, rq);
return NULL;
}
/*
* Try to merge 'next' into 'rq'. Return true if the merge happened, false
* otherwise. The caller is responsible for freeing 'next' if the merge
* happened.
*/
bool blk_attempt_req_merge(struct request_queue *q, struct request *rq,
struct request *next)
{
return attempt_merge(q, rq, next);
}
bool blk_rq_merge_ok(struct request *rq, struct bio *bio)
{
if (!rq_mergeable(rq) || !bio_mergeable(bio))
return false;
if (req_op(rq) != bio_op(bio))
return false;
/* different data direction or already started, don't merge */
if (bio_data_dir(bio) != rq_data_dir(rq))
return false;
/* don't merge across cgroup boundaries */
if (!blk_cgroup_mergeable(rq, bio))
return false;
/* only merge integrity protected bio into ditto rq */
if (blk_integrity_merge_bio(rq->q, rq, bio) == false)
return false;
/* Only merge if the crypt contexts are compatible */
if (!bio_crypt_rq_ctx_compatible(rq, bio))
return false;
/* Don't merge requests with different write hints. */
if (rq->write_hint != bio->bi_write_hint)
return false;
if (rq->ioprio != bio_prio(bio))
return false;
if (blk_atomic_write_mergeable_rq_bio(rq, bio) == false)
return false;
return true;
}
enum elv_merge blk_try_merge(struct request *rq, struct bio *bio)
{
if (blk_discard_mergable(rq))
return ELEVATOR_DISCARD_MERGE;
else if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_iter.bi_sector)
return ELEVATOR_BACK_MERGE;
else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_iter.bi_sector)
return ELEVATOR_FRONT_MERGE;
return ELEVATOR_NO_MERGE;
}
static void blk_account_io_merge_bio(struct request *req)
{
if (!blk_do_io_stat(req))
return;
part_stat_lock();
part_stat_inc(req->part, merges[op_stat_group(req_op(req))]);
part_stat_unlock();
}
enum bio_merge_status bio_attempt_back_merge(struct request *req,
struct bio *bio, unsigned int nr_segs)
{
const blk_opf_t ff = bio_failfast(bio);
if (!ll_back_merge_fn(req, bio, nr_segs))
return BIO_MERGE_FAILED;
trace_block_bio_backmerge(bio);
rq_qos_merge(req->q, req, bio);
if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
blk_rq_set_mixed_merge(req);
blk_update_mixed_merge(req, bio, false);
if (req->rq_flags & RQF_ZONE_WRITE_PLUGGING)
blk_zone_write_plug_bio_merged(bio);
req->biotail->bi_next = bio;
req->biotail = bio;
req->__data_len += bio->bi_iter.bi_size;
bio_crypt_free_ctx(bio);
blk_account_io_merge_bio(req);
return BIO_MERGE_OK;
}
static enum bio_merge_status bio_attempt_front_merge(struct request *req,
struct bio *bio, unsigned int nr_segs)
{
const blk_opf_t ff = bio_failfast(bio);
/*
* A front merge for writes to sequential zones of a zoned block device
* can happen only if the user submitted writes out of order. Do not
* merge such write to let it fail.
*/
if (req->rq_flags & RQF_ZONE_WRITE_PLUGGING)
return BIO_MERGE_FAILED;
if (!ll_front_merge_fn(req, bio, nr_segs))
return BIO_MERGE_FAILED;
trace_block_bio_frontmerge(bio);
rq_qos_merge(req->q, req, bio);
if ((req->cmd_flags & REQ_FAILFAST_MASK) != ff)
blk_rq_set_mixed_merge(req);
blk_update_mixed_merge(req, bio, true);
bio->bi_next = req->bio;
req->bio = bio;
req->__sector = bio->bi_iter.bi_sector;
req->__data_len += bio->bi_iter.bi_size;
bio_crypt_do_front_merge(req, bio);
blk_account_io_merge_bio(req);
return BIO_MERGE_OK;
}
static enum bio_merge_status bio_attempt_discard_merge(struct request_queue *q,
struct request *req, struct bio *bio)
{
unsigned short segments = blk_rq_nr_discard_segments(req);
if (segments >= queue_max_discard_segments(q))
goto no_merge;
if (blk_rq_sectors(req) + bio_sectors(bio) >
blk_rq_get_max_sectors(req, blk_rq_pos(req)))
goto no_merge;
rq_qos_merge(q, req, bio);
req->biotail->bi_next = bio;
req->biotail = bio;
req->__data_len += bio->bi_iter.bi_size;
req->nr_phys_segments = segments + 1;
blk_account_io_merge_bio(req);
return BIO_MERGE_OK;
no_merge:
req_set_nomerge(q, req);
return BIO_MERGE_FAILED;
}
static enum bio_merge_status blk_attempt_bio_merge(struct request_queue *q,
struct request *rq,
struct bio *bio,
unsigned int nr_segs,
bool sched_allow_merge)
{
if (!blk_rq_merge_ok(rq, bio))
return BIO_MERGE_NONE;
switch (blk_try_merge(rq, bio)) {
case ELEVATOR_BACK_MERGE:
if (!sched_allow_merge || blk_mq_sched_allow_merge(q, rq, bio))
return bio_attempt_back_merge(rq, bio, nr_segs);
break;
case ELEVATOR_FRONT_MERGE:
if (!sched_allow_merge || blk_mq_sched_allow_merge(q, rq, bio))
return bio_attempt_front_merge(rq, bio, nr_segs);
break;
case ELEVATOR_DISCARD_MERGE:
return bio_attempt_discard_merge(q, rq, bio);
default:
return BIO_MERGE_NONE;
}
return BIO_MERGE_FAILED;
}
/**
* blk_attempt_plug_merge - try to merge with %current's plugged list
* @q: request_queue new bio is being queued at
* @bio: new bio being queued
* @nr_segs: number of segments in @bio
* from the passed in @q already in the plug list
*
* Determine whether @bio being queued on @q can be merged with the previous
* request on %current's plugged list. Returns %true if merge was successful,
* otherwise %false.
*
* Plugging coalesces IOs from the same issuer for the same purpose without
* going through @q->queue_lock. As such it's more of an issuing mechanism
* than scheduling, and the request, while may have elvpriv data, is not
* added on the elevator at this point. In addition, we don't have
* reliable access to the elevator outside queue lock. Only check basic
* merging parameters without querying the elevator.
*
* Caller must ensure !blk_queue_nomerges(q) beforehand.
*/
bool blk_attempt_plug_merge(struct request_queue *q, struct bio *bio,
unsigned int nr_segs)
{
struct blk_plug *plug = current->plug;
struct request *rq;
if (!plug || rq_list_empty(plug->mq_list))
return false;
rq_list_for_each(&plug->mq_list, rq) {
if (rq->q == q) {
if (blk_attempt_bio_merge(q, rq, bio, nr_segs, false) ==
BIO_MERGE_OK)
return true;
break;
}
/*
* Only keep iterating plug list for merges if we have multiple
* queues
*/
if (!plug->multiple_queues)
break;
}
return false;
}
/*
* Iterate list of requests and see if we can merge this bio with any
* of them.
*/
bool blk_bio_list_merge(struct request_queue *q, struct list_head *list,
struct bio *bio, unsigned int nr_segs)
{
struct request *rq;
int checked = 8;
list_for_each_entry_reverse(rq, list, queuelist) {
if (!checked--)
break;
switch (blk_attempt_bio_merge(q, rq, bio, nr_segs, true)) {
case BIO_MERGE_NONE:
continue;
case BIO_MERGE_OK:
return true;
case BIO_MERGE_FAILED:
return false;
}
}
return false;
}
EXPORT_SYMBOL_GPL(blk_bio_list_merge);
bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
unsigned int nr_segs, struct request **merged_request)
{
struct request *rq;
switch (elv_merge(q, &rq, bio)) {
case ELEVATOR_BACK_MERGE:
if (!blk_mq_sched_allow_merge(q, rq, bio))
return false;
if (bio_attempt_back_merge(rq, bio, nr_segs) != BIO_MERGE_OK)
return false;
*merged_request = attempt_back_merge(q, rq);
if (!*merged_request)
elv_merged_request(q, rq, ELEVATOR_BACK_MERGE);
return true;
case ELEVATOR_FRONT_MERGE:
if (!blk_mq_sched_allow_merge(q, rq, bio))
return false;
if (bio_attempt_front_merge(rq, bio, nr_segs) != BIO_MERGE_OK)
return false;
*merged_request = attempt_front_merge(q, rq);
if (!*merged_request)
elv_merged_request(q, rq, ELEVATOR_FRONT_MERGE);
return true;
case ELEVATOR_DISCARD_MERGE:
return bio_attempt_discard_merge(q, rq, bio) == BIO_MERGE_OK;
default:
return false;
}
}
EXPORT_SYMBOL_GPL(blk_mq_sched_try_merge);
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