linux/block/blk-merge.c
Ming Lei 6952a7f844 block: split bio if the only bvec's length is > SZ_4K
64K PAGE_SIZE is popular on ARM64 or other ARCHs, and 64K has been big
enough to break some devices probably, so change the logic to split bio
if the only bvec's length is > SZ_4K instead of PAGE_SIZE.

Fixes: fa53228721 (block: avoid blk_bio_segment_split for small I/O operations)
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
2019-11-08 06:59:51 -07:00

911 lines
24 KiB
C

// 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"
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, &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 = 0;
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);
}
/*
* 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 request_queue *q,
struct bio *bio)
{
unsigned sectors = blk_max_size_offset(q, bio->bi_iter.bi_sector);
unsigned max_sectors = sectors;
unsigned pbs = queue_physical_block_size(q) >> SECTOR_SHIFT;
unsigned lbs = queue_logical_block_size(q) >> SECTOR_SHIFT;
unsigned start_offset = bio->bi_iter.bi_sector & (pbs - 1);
max_sectors += start_offset;
max_sectors &= ~(pbs - 1);
if (max_sectors > start_offset)
return max_sectors - start_offset;
return sectors & (lbs - 1);
}
static unsigned get_max_segment_size(const struct request_queue *q,
unsigned offset)
{
unsigned long mask = queue_segment_boundary(q);
/* default segment boundary mask means no boundary limit */
if (mask == BLK_SEG_BOUNDARY_MASK)
return queue_max_segment_size(q);
return min_t(unsigned long, mask - (mask & offset) + 1,
queue_max_segment_size(q));
}
/**
* bvec_split_segs - verify whether or not a bvec should be split in the middle
* @q: [in] request queue associated with the bio associated with @bv
* @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
* @sectors: [in,out] Number of sectors in the bio being built. Incremented
* by the number of sectors from @bv that may be appended to that
* bio without exceeding @max_sectors
* @max_segs: [in] upper bound for *@nsegs
* @max_sectors: [in] upper bound for *@sectors
*
* 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 request_queue *q,
const struct bio_vec *bv, unsigned *nsegs,
unsigned *sectors, unsigned max_segs,
unsigned max_sectors)
{
unsigned max_len = (min(max_sectors, UINT_MAX >> 9) - *sectors) << 9;
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(q, bv->bv_offset + total_len);
seg_size = min(seg_size, len);
(*nsegs)++;
total_len += seg_size;
len -= seg_size;
if ((bv->bv_offset + total_len) & queue_virt_boundary(q))
break;
}
*sectors += total_len >> 9;
/* tell the caller to split the bvec if it is too big to fit */
return len > 0 || bv->bv_len > max_len;
}
/**
* blk_bio_segment_split - split a bio in two bios
* @q: [in] request queue pointer
* @bio: [in] bio to be split
* @bs: [in] bio set to allocate the clone from
* @segs: [out] number of segments in the bio with the first half of the sectors
*
* Clone @bio, update the bi_iter of the clone to represent the first sectors
* of @bio and update @bio->bi_iter to represent the remaining sectors. The
* following is guaranteed for the cloned bio:
* - That it has at most get_max_io_size(@q, @bio) sectors.
* - That it has at most queue_max_segments(@q) segments.
*
* Except for discard requests the cloned bio will point at the bi_io_vec of
* the original bio. It is the responsibility of the caller to ensure that the
* original bio is not freed before the cloned bio. The caller is also
* responsible for ensuring that @bs is only destroyed after processing of the
* split bio has finished.
*/
static struct bio *blk_bio_segment_split(struct request_queue *q,
struct bio *bio,
struct bio_set *bs,
unsigned *segs)
{
struct bio_vec bv, bvprv, *bvprvp = NULL;
struct bvec_iter iter;
unsigned nsegs = 0, sectors = 0;
const unsigned max_sectors = get_max_io_size(q, bio);
const unsigned max_segs = queue_max_segments(q);
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(q, bvprvp, bv.bv_offset))
goto split;
if (nsegs < max_segs &&
sectors + (bv.bv_len >> 9) <= max_sectors &&
bv.bv_offset + bv.bv_len <= PAGE_SIZE) {
nsegs++;
sectors += bv.bv_len >> 9;
} else if (bvec_split_segs(q, &bv, &nsegs, &sectors, max_segs,
max_sectors)) {
goto split;
}
bvprv = bv;
bvprvp = &bvprv;
}
*segs = nsegs;
return NULL;
split:
*segs = nsegs;
return bio_split(bio, sectors, GFP_NOIO, bs);
}
/**
* __blk_queue_split - split a bio and submit the second half
* @q: [in] request queue pointer
* @bio: [in, out] bio to be split
* @nr_segs: [out] number of segments in the first bio
*
* Split a bio into two bios, chain the two bios, submit the second half and
* store a pointer to the first half in *@bio. If the second bio is still too
* big it will be split by a recursive call to this function. Since this
* function may allocate a new bio from @q->bio_split, it is the responsibility
* of the caller to ensure that @q is only released after processing of the
* split bio has finished.
*/
void __blk_queue_split(struct request_queue *q, struct bio **bio,
unsigned int *nr_segs)
{
struct bio *split = NULL;
switch (bio_op(*bio)) {
case REQ_OP_DISCARD:
case REQ_OP_SECURE_ERASE:
split = blk_bio_discard_split(q, *bio, &q->bio_split, nr_segs);
break;
case REQ_OP_WRITE_ZEROES:
split = blk_bio_write_zeroes_split(q, *bio, &q->bio_split,
nr_segs);
break;
case REQ_OP_WRITE_SAME:
split = blk_bio_write_same_split(q, *bio, &q->bio_split,
nr_segs);
break;
default:
/*
* All drivers must accept single-segments bios that are <=
* PAGE_SIZE. This is a quick and dirty check that relies on
* the fact that bi_io_vec[0] is always valid if a bio has data.
* The check might lead to occasional false negatives when bios
* are cloned, but compared to the performance impact of cloned
* bios themselves the loop below doesn't matter anyway.
*/
if (!q->limits.chunk_sectors &&
(*bio)->bi_vcnt == 1 &&
((*bio)->bi_io_vec[0].bv_len +
(*bio)->bi_io_vec[0].bv_offset) <= SZ_4K) {
*nr_segs = 1;
break;
}
split = blk_bio_segment_split(q, *bio, &q->bio_split, nr_segs);
break;
}
if (split) {
/* there isn't chance to merge the splitted bio */
split->bi_opf |= REQ_NOMERGE;
/*
* Since we're recursing into make_request here, ensure
* that we mark this bio as already having entered the queue.
* If not, and the queue is going away, we can get stuck
* forever on waiting for the queue reference to drop. But
* that will never happen, as we're already holding a
* reference to it.
*/
bio_set_flag(*bio, BIO_QUEUE_ENTERED);
bio_chain(split, *bio);
trace_block_split(q, split, (*bio)->bi_iter.bi_sector);
generic_make_request(*bio);
*bio = split;
}
}
/**
* blk_queue_split - split a bio and submit the second half
* @q: [in] request queue pointer
* @bio: [in, out] bio to be split
*
* Split a bio into two bios, chains the two bios, submit the second half and
* store a pointer to the first half in *@bio. Since this function may allocate
* a new bio from @q->bio_split, it is the responsibility of the caller to
* ensure that @q is only released after processing of the split bio has
* finished.
*/
void blk_queue_split(struct request_queue *q, struct bio **bio)
{
unsigned int nr_segs;
__blk_queue_split(q, bio, &nr_segs);
}
EXPORT_SYMBOL(blk_queue_split);
unsigned int blk_recalc_rq_segments(struct request *rq)
{
unsigned int nr_phys_segs = 0;
unsigned int nr_sectors = 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:
case REQ_OP_WRITE_ZEROES:
return 0;
case REQ_OP_WRITE_SAME:
return 1;
}
rq_for_each_bvec(bv, rq, iter)
bvec_split_segs(rq->q, &bv, &nr_phys_segs, &nr_sectors,
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 = min(get_max_segment_size(q, offset), 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 uninitialized_var(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 *sg = NULL;
int nsegs = 0;
if (rq->rq_flags & RQF_SPECIAL_PAYLOAD)
nsegs = __blk_bvec_map_sg(rq->special_vec, sglist, &sg);
else if (rq->bio && bio_op(rq->bio) == REQ_OP_WRITE_SAME)
nsegs = __blk_bvec_map_sg(bio_iovec(rq->bio), sglist, &sg);
else if (rq->bio)
nsegs = __blk_bios_map_sg(q, rq->bio, sglist, &sg);
if (unlikely(rq->rq_flags & RQF_COPY_USER) &&
(blk_rq_bytes(rq) & q->dma_pad_mask)) {
unsigned int pad_len =
(q->dma_pad_mask & ~blk_rq_bytes(rq)) + 1;
sg->length += pad_len;
rq->extra_len += pad_len;
}
if (q->dma_drain_size && q->dma_drain_needed(rq)) {
if (op_is_write(req_op(rq)))
memset(q->dma_drain_buffer, 0, q->dma_drain_size);
sg_unmark_end(sg);
sg = sg_next(sg);
sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
q->dma_drain_size,
((unsigned long)q->dma_drain_buffer) &
(PAGE_SIZE - 1));
nsegs++;
rq->extra_len += q->dma_drain_size;
}
if (sg)
sg_mark_end(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 int ll_new_hw_segment(struct request *req, struct bio *bio,
unsigned int nr_phys_segs)
{
if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(req->q))
goto no_merge;
if (blk_integrity_merge_bio(req->q, req, bio) == false)
goto no_merge;
/*
* This will form the start of a new hw segment. Bump both
* counters.
*/
req->nr_phys_segments += nr_phys_segs;
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 (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);
}
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 (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 > queue_max_segments(q))
return 0;
if (blk_integrity_merge_rq(q, req, next) == false)
return 0;
/* Merge is OK... */
req->nr_phys_segments = total_phys_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.
*/
void blk_rq_set_mixed_merge(struct request *rq)
{
unsigned int 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 void blk_account_io_merge(struct request *req)
{
if (blk_do_io_stat(req)) {
struct hd_struct *part;
part_stat_lock();
part = req->part;
part_dec_in_flight(req->q, part, rq_data_dir(req));
hd_struct_put(part);
part_stat_unlock();
}
}
/*
* Two cases of handling DISCARD merge:
* If max_discard_segments > 1, the driver takes every bio
* as a range and send them to controller together. The ranges
* needn't to be contiguous.
* Otherwise, the bios/requests will be handled as same as
* others which should be contiguous.
*/
static inline bool blk_discard_mergable(struct request *req)
{
if (req_op(req) == REQ_OP_DISCARD &&
queue_max_discard_segments(req->q) > 1)
return true;
return false;
}
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;
}
/*
* 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)
|| req->rq_disk != next->rq_disk)
return NULL;
if (req_op(req) == REQ_OP_WRITE_SAME &&
!blk_write_same_mergeable(req->bio, next->bio))
return NULL;
/*
* Don't allow merge of different write hints, or for a hint with
* non-hint IO.
*/
if (req->write_hint != next->write_hint)
return NULL;
if (req->ioprio != next->ioprio)
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);
/*
* 'next' is going away, so update stats accordingly
*/
blk_account_io_merge(next);
/*
* ownership of bio passed from next to req, return 'next' for
* the caller to free
*/
next->bio = NULL;
return next;
}
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;
}
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;
}
int blk_attempt_req_merge(struct request_queue *q, struct request *rq,
struct request *next)
{
struct request *free;
free = attempt_merge(q, rq, next);
if (free) {
blk_put_request(free);
return 1;
}
return 0;
}
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;
/* must be same device */
if (rq->rq_disk != bio->bi_disk)
return false;
/* only merge integrity protected bio into ditto rq */
if (blk_integrity_merge_bio(rq->q, rq, bio) == false)
return false;
/* must be using the same buffer */
if (req_op(rq) == REQ_OP_WRITE_SAME &&
!blk_write_same_mergeable(rq->bio, bio))
return false;
/*
* Don't allow merge of different write hints, or for a hint with
* non-hint IO.
*/
if (rq->write_hint != bio->bi_write_hint)
return false;
if (rq->ioprio != bio_prio(bio))
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;
}