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DEFINITIONS
This source file includes following definitions.
- blk_recalc_rq_sectors
- blk_recalc_rq_segments
- blk_recount_segments
- blk_phys_contig_segment
- blk_rq_map_sg
- ll_new_mergeable
- ll_new_hw_segment
- ll_back_merge_fn
- ll_front_merge_fn
- ll_merge_requests_fn
- attempt_merge
- attempt_back_merge
- attempt_front_merge
/*
* 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"
void blk_recalc_rq_sectors(struct request *rq, int nsect)
{
if (blk_fs_request(rq) || blk_discard_rq(rq)) {
rq->hard_sector += nsect;
rq->hard_nr_sectors -= nsect;
/*
* Move the I/O submission pointers ahead if required.
*/
if ((rq->nr_sectors >= rq->hard_nr_sectors) &&
(rq->sector <= rq->hard_sector)) {
rq->sector = rq->hard_sector;
rq->nr_sectors = rq->hard_nr_sectors;
rq->hard_cur_sectors = bio_cur_sectors(rq->bio);
rq->current_nr_sectors = rq->hard_cur_sectors;
rq->buffer = bio_data(rq->bio);
}
/*
* if total number of sectors is less than the first segment
* size, something has gone terribly wrong
*/
if (rq->nr_sectors < rq->current_nr_sectors) {
printk(KERN_ERR "blk: request botched\n");
rq->nr_sectors = rq->current_nr_sectors;
}
}
}
void blk_recalc_rq_segments(struct request *rq)
{
int nr_phys_segs;
unsigned int phys_size;
struct bio_vec *bv, *bvprv = NULL;
int seg_size;
int cluster;
struct req_iterator iter;
int high, highprv = 1;
struct request_queue *q = rq->q;
if (!rq->bio)
return;
cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
seg_size = 0;
phys_size = nr_phys_segs = 0;
rq_for_each_segment(bv, rq, iter) {
/*
* 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) > q->bounce_pfn;
if (high || highprv)
goto new_segment;
if (cluster) {
if (seg_size + bv->bv_len > q->max_segment_size)
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:
nr_phys_segs++;
bvprv = bv;
seg_size = bv->bv_len;
highprv = high;
}
rq->nr_phys_segments = nr_phys_segs;
}
void blk_recount_segments(struct request_queue *q, struct bio *bio)
{
struct request rq;
struct bio *nxt = bio->bi_next;
rq.q = q;
rq.bio = rq.biotail = bio;
bio->bi_next = NULL;
blk_recalc_rq_segments(&rq);
bio->bi_next = nxt;
bio->bi_phys_segments = rq.nr_phys_segments;
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 (!test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags))
return 0;
if (bio->bi_size + nxt->bi_size > q->max_segment_size)
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;
}
/*
* 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 = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
/*
* for each bio in rq
*/
bvprv = NULL;
sg = NULL;
rq_for_each_segment(bvec, rq, iter) {
int nbytes = bvec->bv_len;
if (bvprv && cluster) {
if (sg->length + nbytes > q->max_segment_size)
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->page_link &= ~0x02;
sg = sg_next(sg);
}
sg_set_page(sg, bvec->bv_page, nbytes, bvec->bv_offset);
nsegs++;
}
bvprv = bvec;
} /* segments in rq */
if (unlikely(rq->cmd_flags & REQ_COPY_USER) &&
(rq->data_len & q->dma_pad_mask)) {
unsigned int pad_len = (q->dma_pad_mask & ~rq->data_len) + 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_RW)
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);
static inline int ll_new_mergeable(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 > q->max_phys_segments) {
req->cmd_flags |= REQ_NOMERGE;
if (req == q->last_merge)
q->last_merge = NULL;
return 0;
}
/*
* A hw segment is just getting larger, bump just the phys
* counter.
*/
req->nr_phys_segments += nr_phys_segs;
return 1;
}
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 > q->max_hw_segments
|| req->nr_phys_segments + nr_phys_segs > q->max_phys_segments) {
req->cmd_flags |= REQ_NOMERGE;
if (req == q->last_merge)
q->last_merge = NULL;
return 0;
}
/*
* This will form the start of a new hw segment. Bump both
* counters.
*/
req->nr_phys_segments += nr_phys_segs;
return 1;
}
int ll_back_merge_fn(struct request_queue *q, struct request *req,
struct bio *bio)
{
unsigned short max_sectors;
if (unlikely(blk_pc_request(req)))
max_sectors = q->max_hw_sectors;
else
max_sectors = q->max_sectors;
if (req->nr_sectors + bio_sectors(bio) > max_sectors) {
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)
{
unsigned short max_sectors;
if (unlikely(blk_pc_request(req)))
max_sectors = q->max_hw_sectors;
else
max_sectors = q->max_sectors;
if (req->nr_sectors + bio_sectors(bio) > max_sectors) {
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;
/*
* 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 ((req->nr_sectors + next->nr_sectors) > q->max_sectors)
return 0;
total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
if (blk_phys_contig_segment(q, req->biotail, next->bio))
total_phys_segments--;
if (total_phys_segments > q->max_phys_segments)
return 0;
if (total_phys_segments > q->max_hw_segments)
return 0;
/* Merge is OK... */
req->nr_phys_segments = total_phys_segments;
return 1;
}
/*
* 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;
/*
* not contiguous
*/
if (req->sector + req->nr_sectors != next->sector)
return 0;
if (rq_data_dir(req) != rq_data_dir(next)
|| req->rq_disk != next->rq_disk
|| next->special)
return 0;
if (blk_integrity_rq(req) != blk_integrity_rq(next))
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;
/*
* 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->nr_sectors = req->hard_nr_sectors += next->hard_nr_sectors;
elv_merge_requests(q, req, next);
if (req->rq_disk) {
struct hd_struct *part;
int cpu;
cpu = part_stat_lock();
part = disk_map_sector_rcu(req->rq_disk, req->sector);
part_round_stats(cpu, part);
part_dec_in_flight(part);
part_stat_unlock();
}
req->ioprio = ioprio_best(req->ioprio, next->ioprio);
if (blk_rq_cpu_valid(next))
req->cpu = next->cpu;
__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;
}