mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-21 16:29:59 +00:00
![Paolo Bonzini](/assets/img/avatar_default.png)
This is useful in places that recycle the same scatterlist multiple times, and do not want to incur the cost of sg_init_table every time in hot paths. Acked-by: Jens Axboe <axboe@kernel.dk> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
540 lines
13 KiB
C
540 lines
13 KiB
C
/*
|
|
* 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 "blk.h"
|
|
|
|
static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
|
|
struct bio *bio)
|
|
{
|
|
struct bio_vec *bv, *bvprv = NULL;
|
|
int cluster, i, high, highprv = 1;
|
|
unsigned int seg_size, nr_phys_segs;
|
|
struct bio *fbio, *bbio;
|
|
|
|
if (!bio)
|
|
return 0;
|
|
|
|
fbio = bio;
|
|
cluster = blk_queue_cluster(q);
|
|
seg_size = 0;
|
|
nr_phys_segs = 0;
|
|
for_each_bio(bio) {
|
|
bio_for_each_segment(bv, bio, i) {
|
|
/*
|
|
* the trick here is making sure that a high page is
|
|
* never considered part of another segment, since that
|
|
* might change with the bounce page.
|
|
*/
|
|
high = page_to_pfn(bv->bv_page) > queue_bounce_pfn(q);
|
|
if (high || highprv)
|
|
goto new_segment;
|
|
if (cluster) {
|
|
if (seg_size + bv->bv_len
|
|
> queue_max_segment_size(q))
|
|
goto new_segment;
|
|
if (!BIOVEC_PHYS_MERGEABLE(bvprv, bv))
|
|
goto new_segment;
|
|
if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bv))
|
|
goto new_segment;
|
|
|
|
seg_size += bv->bv_len;
|
|
bvprv = bv;
|
|
continue;
|
|
}
|
|
new_segment:
|
|
if (nr_phys_segs == 1 && seg_size >
|
|
fbio->bi_seg_front_size)
|
|
fbio->bi_seg_front_size = seg_size;
|
|
|
|
nr_phys_segs++;
|
|
bvprv = bv;
|
|
seg_size = bv->bv_len;
|
|
highprv = high;
|
|
}
|
|
bbio = bio;
|
|
}
|
|
|
|
if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size)
|
|
fbio->bi_seg_front_size = seg_size;
|
|
if (seg_size > bbio->bi_seg_back_size)
|
|
bbio->bi_seg_back_size = seg_size;
|
|
|
|
return nr_phys_segs;
|
|
}
|
|
|
|
void blk_recalc_rq_segments(struct request *rq)
|
|
{
|
|
rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio);
|
|
}
|
|
|
|
void blk_recount_segments(struct request_queue *q, struct bio *bio)
|
|
{
|
|
struct bio *nxt = bio->bi_next;
|
|
|
|
bio->bi_next = NULL;
|
|
bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio);
|
|
bio->bi_next = nxt;
|
|
bio->bi_flags |= (1 << BIO_SEG_VALID);
|
|
}
|
|
EXPORT_SYMBOL(blk_recount_segments);
|
|
|
|
static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
|
|
struct bio *nxt)
|
|
{
|
|
if (!blk_queue_cluster(q))
|
|
return 0;
|
|
|
|
if (bio->bi_seg_back_size + nxt->bi_seg_front_size >
|
|
queue_max_segment_size(q))
|
|
return 0;
|
|
|
|
if (!bio_has_data(bio))
|
|
return 1;
|
|
|
|
if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)))
|
|
return 0;
|
|
|
|
/*
|
|
* bio and nxt are contiguous in memory; check if the queue allows
|
|
* these two to be merged into one
|
|
*/
|
|
if (BIO_SEG_BOUNDARY(q, bio, nxt))
|
|
return 1;
|
|
|
|
return 0;
|
|
}
|
|
|
|
static void
|
|
__blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec,
|
|
struct scatterlist *sglist, struct bio_vec **bvprv,
|
|
struct scatterlist **sg, int *nsegs, int *cluster)
|
|
{
|
|
|
|
int nbytes = bvec->bv_len;
|
|
|
|
if (*bvprv && *cluster) {
|
|
if ((*sg)->length + nbytes > queue_max_segment_size(q))
|
|
goto new_segment;
|
|
|
|
if (!BIOVEC_PHYS_MERGEABLE(*bvprv, bvec))
|
|
goto new_segment;
|
|
if (!BIOVEC_SEG_BOUNDARY(q, *bvprv, bvec))
|
|
goto new_segment;
|
|
|
|
(*sg)->length += nbytes;
|
|
} else {
|
|
new_segment:
|
|
if (!*sg)
|
|
*sg = sglist;
|
|
else {
|
|
/*
|
|
* 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);
|
|
*sg = sg_next(*sg);
|
|
}
|
|
|
|
sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset);
|
|
(*nsegs)++;
|
|
}
|
|
*bvprv = bvec;
|
|
}
|
|
|
|
/*
|
|
* 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 bio_vec *bvec, *bvprv;
|
|
struct req_iterator iter;
|
|
struct scatterlist *sg;
|
|
int nsegs, cluster;
|
|
|
|
nsegs = 0;
|
|
cluster = blk_queue_cluster(q);
|
|
|
|
/*
|
|
* for each bio in rq
|
|
*/
|
|
bvprv = NULL;
|
|
sg = NULL;
|
|
rq_for_each_segment(bvec, rq, iter) {
|
|
__blk_segment_map_sg(q, bvec, sglist, &bvprv, &sg,
|
|
&nsegs, &cluster);
|
|
} /* segments in rq */
|
|
|
|
|
|
if (unlikely(rq->cmd_flags & REQ_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 (rq->cmd_flags & REQ_WRITE)
|
|
memset(q->dma_drain_buffer, 0, q->dma_drain_size);
|
|
|
|
sg->page_link &= ~0x02;
|
|
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);
|
|
|
|
return nsegs;
|
|
}
|
|
EXPORT_SYMBOL(blk_rq_map_sg);
|
|
|
|
/**
|
|
* blk_bio_map_sg - map a bio to a scatterlist
|
|
* @q: request_queue in question
|
|
* @bio: bio being mapped
|
|
* @sglist: scatterlist being mapped
|
|
*
|
|
* Note:
|
|
* Caller must make sure sg can hold bio->bi_phys_segments entries
|
|
*
|
|
* Will return the number of sg entries setup
|
|
*/
|
|
int blk_bio_map_sg(struct request_queue *q, struct bio *bio,
|
|
struct scatterlist *sglist)
|
|
{
|
|
struct bio_vec *bvec, *bvprv;
|
|
struct scatterlist *sg;
|
|
int nsegs, cluster;
|
|
unsigned long i;
|
|
|
|
nsegs = 0;
|
|
cluster = blk_queue_cluster(q);
|
|
|
|
bvprv = NULL;
|
|
sg = NULL;
|
|
bio_for_each_segment(bvec, bio, i) {
|
|
__blk_segment_map_sg(q, bvec, sglist, &bvprv, &sg,
|
|
&nsegs, &cluster);
|
|
} /* segments in bio */
|
|
|
|
if (sg)
|
|
sg_mark_end(sg);
|
|
|
|
BUG_ON(bio->bi_phys_segments && nsegs > bio->bi_phys_segments);
|
|
return nsegs;
|
|
}
|
|
EXPORT_SYMBOL(blk_bio_map_sg);
|
|
|
|
static inline int ll_new_hw_segment(struct request_queue *q,
|
|
struct request *req,
|
|
struct bio *bio)
|
|
{
|
|
int nr_phys_segs = bio_phys_segments(q, bio);
|
|
|
|
if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q))
|
|
goto no_merge;
|
|
|
|
if (bio_integrity(bio) && blk_integrity_merge_bio(q, req, bio))
|
|
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->cmd_flags |= REQ_NOMERGE;
|
|
if (req == q->last_merge)
|
|
q->last_merge = NULL;
|
|
return 0;
|
|
}
|
|
|
|
int ll_back_merge_fn(struct request_queue *q, struct request *req,
|
|
struct bio *bio)
|
|
{
|
|
if (blk_rq_sectors(req) + bio_sectors(bio) >
|
|
blk_rq_get_max_sectors(req)) {
|
|
req->cmd_flags |= REQ_NOMERGE;
|
|
if (req == q->last_merge)
|
|
q->last_merge = NULL;
|
|
return 0;
|
|
}
|
|
if (!bio_flagged(req->biotail, BIO_SEG_VALID))
|
|
blk_recount_segments(q, req->biotail);
|
|
if (!bio_flagged(bio, BIO_SEG_VALID))
|
|
blk_recount_segments(q, bio);
|
|
|
|
return ll_new_hw_segment(q, req, bio);
|
|
}
|
|
|
|
int ll_front_merge_fn(struct request_queue *q, struct request *req,
|
|
struct bio *bio)
|
|
{
|
|
if (blk_rq_sectors(req) + bio_sectors(bio) >
|
|
blk_rq_get_max_sectors(req)) {
|
|
req->cmd_flags |= REQ_NOMERGE;
|
|
if (req == q->last_merge)
|
|
q->last_merge = NULL;
|
|
return 0;
|
|
}
|
|
if (!bio_flagged(bio, BIO_SEG_VALID))
|
|
blk_recount_segments(q, bio);
|
|
if (!bio_flagged(req->bio, BIO_SEG_VALID))
|
|
blk_recount_segments(q, req->bio);
|
|
|
|
return ll_new_hw_segment(q, req, bio);
|
|
}
|
|
|
|
static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
|
|
struct request *next)
|
|
{
|
|
int total_phys_segments;
|
|
unsigned int seg_size =
|
|
req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size;
|
|
|
|
/*
|
|
* First check if the either of the requests are re-queued
|
|
* requests. Can't merge them if they are.
|
|
*/
|
|
if (req->special || next->special)
|
|
return 0;
|
|
|
|
/*
|
|
* Will it become too large?
|
|
*/
|
|
if ((blk_rq_sectors(req) + blk_rq_sectors(next)) >
|
|
blk_rq_get_max_sectors(req))
|
|
return 0;
|
|
|
|
total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
|
|
if (blk_phys_contig_segment(q, req->biotail, next->bio)) {
|
|
if (req->nr_phys_segments == 1)
|
|
req->bio->bi_seg_front_size = seg_size;
|
|
if (next->nr_phys_segments == 1)
|
|
next->biotail->bi_seg_back_size = seg_size;
|
|
total_phys_segments--;
|
|
}
|
|
|
|
if (total_phys_segments > queue_max_segments(q))
|
|
return 0;
|
|
|
|
if (blk_integrity_rq(req) && blk_integrity_merge_rq(q, req, next))
|
|
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->cmd_flags & REQ_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_rw & REQ_FAILFAST_MASK) &&
|
|
(bio->bi_rw & REQ_FAILFAST_MASK) != ff);
|
|
bio->bi_rw |= ff;
|
|
}
|
|
rq->cmd_flags |= REQ_MIXED_MERGE;
|
|
}
|
|
|
|
static void blk_account_io_merge(struct request *req)
|
|
{
|
|
if (blk_do_io_stat(req)) {
|
|
struct hd_struct *part;
|
|
int cpu;
|
|
|
|
cpu = part_stat_lock();
|
|
part = req->part;
|
|
|
|
part_round_stats(cpu, part);
|
|
part_dec_in_flight(part, rq_data_dir(req));
|
|
|
|
hd_struct_put(part);
|
|
part_stat_unlock();
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Has to be called with the request spinlock acquired
|
|
*/
|
|
static int attempt_merge(struct request_queue *q, struct request *req,
|
|
struct request *next)
|
|
{
|
|
if (!rq_mergeable(req) || !rq_mergeable(next))
|
|
return 0;
|
|
|
|
if (!blk_check_merge_flags(req->cmd_flags, next->cmd_flags))
|
|
return 0;
|
|
|
|
/*
|
|
* not contiguous
|
|
*/
|
|
if (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next))
|
|
return 0;
|
|
|
|
if (rq_data_dir(req) != rq_data_dir(next)
|
|
|| req->rq_disk != next->rq_disk
|
|
|| next->special)
|
|
return 0;
|
|
|
|
if (req->cmd_flags & REQ_WRITE_SAME &&
|
|
!blk_write_same_mergeable(req->bio, next->bio))
|
|
return 0;
|
|
|
|
/*
|
|
* 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.
|
|
*/
|
|
if (!ll_merge_requests_fn(q, req, next))
|
|
return 0;
|
|
|
|
/*
|
|
* 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->cmd_flags | next->cmd_flags) & REQ_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 of
|
|
* the merged requests to be the current request
|
|
* for accounting purposes.
|
|
*/
|
|
if (time_after(req->start_time, next->start_time))
|
|
req->start_time = next->start_time;
|
|
|
|
req->biotail->bi_next = next->bio;
|
|
req->biotail = next->biotail;
|
|
|
|
req->__data_len += blk_rq_bytes(next);
|
|
|
|
elv_merge_requests(q, req, next);
|
|
|
|
/*
|
|
* 'next' is going away, so update stats accordingly
|
|
*/
|
|
blk_account_io_merge(next);
|
|
|
|
req->ioprio = ioprio_best(req->ioprio, next->ioprio);
|
|
if (blk_rq_cpu_valid(next))
|
|
req->cpu = next->cpu;
|
|
|
|
/* owner-ship of bio passed from next to req */
|
|
next->bio = NULL;
|
|
__blk_put_request(q, next);
|
|
return 1;
|
|
}
|
|
|
|
int 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 0;
|
|
}
|
|
|
|
int 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 0;
|
|
}
|
|
|
|
int 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 (!blk_check_merge_flags(rq->cmd_flags, bio->bi_rw))
|
|
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 and not a special request */
|
|
if (rq->rq_disk != bio->bi_bdev->bd_disk || rq->special)
|
|
return false;
|
|
|
|
/* only merge integrity protected bio into ditto rq */
|
|
if (bio_integrity(bio) != blk_integrity_rq(rq))
|
|
return false;
|
|
|
|
/* must be using the same buffer */
|
|
if (rq->cmd_flags & REQ_WRITE_SAME &&
|
|
!blk_write_same_mergeable(rq->bio, bio))
|
|
return false;
|
|
|
|
return true;
|
|
}
|
|
|
|
int blk_try_merge(struct request *rq, struct bio *bio)
|
|
{
|
|
if (blk_rq_pos(rq) + blk_rq_sectors(rq) == bio->bi_sector)
|
|
return ELEVATOR_BACK_MERGE;
|
|
else if (blk_rq_pos(rq) - bio_sectors(bio) == bio->bi_sector)
|
|
return ELEVATOR_FRONT_MERGE;
|
|
return ELEVATOR_NO_MERGE;
|
|
}
|