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![David Woodhouse](/assets/img/avatar_default.png)
But blkdev_issue_discard() still emits requests which are interpreted as soft barriers, because naïve callers might otherwise issue subsequent writes to those same sectors, which might cross on the queue (if they're reallocated quickly enough). Callers still _can_ issue non-barrier discard requests, but they have to take care of queue ordering for themselves. Signed-off-by: David Woodhouse <David.Woodhouse@intel.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
514 lines
12 KiB
C
514 lines
12 KiB
C
/*
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* Functions related to segment and merge handling
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*/
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <linux/bio.h>
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#include <linux/blkdev.h>
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#include <linux/scatterlist.h>
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#include "blk.h"
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void blk_recalc_rq_sectors(struct request *rq, int nsect)
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{
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if (blk_fs_request(rq) || blk_discard_rq(rq)) {
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rq->hard_sector += nsect;
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rq->hard_nr_sectors -= nsect;
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/*
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* Move the I/O submission pointers ahead if required.
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*/
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if ((rq->nr_sectors >= rq->hard_nr_sectors) &&
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(rq->sector <= rq->hard_sector)) {
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rq->sector = rq->hard_sector;
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rq->nr_sectors = rq->hard_nr_sectors;
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rq->hard_cur_sectors = bio_cur_sectors(rq->bio);
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rq->current_nr_sectors = rq->hard_cur_sectors;
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rq->buffer = bio_data(rq->bio);
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}
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/*
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* if total number of sectors is less than the first segment
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* size, something has gone terribly wrong
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*/
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if (rq->nr_sectors < rq->current_nr_sectors) {
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printk(KERN_ERR "blk: request botched\n");
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rq->nr_sectors = rq->current_nr_sectors;
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}
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}
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}
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void blk_recalc_rq_segments(struct request *rq)
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{
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int nr_phys_segs;
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int nr_hw_segs;
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unsigned int phys_size;
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unsigned int hw_size;
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struct bio_vec *bv, *bvprv = NULL;
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int seg_size;
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int hw_seg_size;
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int cluster;
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struct req_iterator iter;
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int high, highprv = 1;
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struct request_queue *q = rq->q;
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if (!rq->bio)
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return;
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cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
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hw_seg_size = seg_size = 0;
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phys_size = hw_size = nr_phys_segs = nr_hw_segs = 0;
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rq_for_each_segment(bv, rq, iter) {
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/*
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* the trick here is making sure that a high page is never
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* considered part of another segment, since that might
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* change with the bounce page.
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*/
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high = page_to_pfn(bv->bv_page) > q->bounce_pfn;
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if (high || highprv)
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goto new_hw_segment;
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if (cluster) {
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if (seg_size + bv->bv_len > q->max_segment_size)
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goto new_segment;
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if (!BIOVEC_PHYS_MERGEABLE(bvprv, bv))
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goto new_segment;
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if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bv))
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goto new_segment;
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if (BIOVEC_VIRT_OVERSIZE(hw_seg_size + bv->bv_len))
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goto new_hw_segment;
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seg_size += bv->bv_len;
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hw_seg_size += bv->bv_len;
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bvprv = bv;
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continue;
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}
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new_segment:
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if (BIOVEC_VIRT_MERGEABLE(bvprv, bv) &&
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!BIOVEC_VIRT_OVERSIZE(hw_seg_size + bv->bv_len))
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hw_seg_size += bv->bv_len;
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else {
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new_hw_segment:
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if (nr_hw_segs == 1 &&
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hw_seg_size > rq->bio->bi_hw_front_size)
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rq->bio->bi_hw_front_size = hw_seg_size;
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hw_seg_size = BIOVEC_VIRT_START_SIZE(bv) + bv->bv_len;
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nr_hw_segs++;
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}
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nr_phys_segs++;
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bvprv = bv;
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seg_size = bv->bv_len;
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highprv = high;
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}
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if (nr_hw_segs == 1 &&
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hw_seg_size > rq->bio->bi_hw_front_size)
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rq->bio->bi_hw_front_size = hw_seg_size;
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if (hw_seg_size > rq->biotail->bi_hw_back_size)
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rq->biotail->bi_hw_back_size = hw_seg_size;
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rq->nr_phys_segments = nr_phys_segs;
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rq->nr_hw_segments = nr_hw_segs;
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}
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void blk_recount_segments(struct request_queue *q, struct bio *bio)
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{
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struct request rq;
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struct bio *nxt = bio->bi_next;
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rq.q = q;
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rq.bio = rq.biotail = bio;
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bio->bi_next = NULL;
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blk_recalc_rq_segments(&rq);
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bio->bi_next = nxt;
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bio->bi_phys_segments = rq.nr_phys_segments;
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bio->bi_hw_segments = rq.nr_hw_segments;
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bio->bi_flags |= (1 << BIO_SEG_VALID);
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}
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EXPORT_SYMBOL(blk_recount_segments);
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static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
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struct bio *nxt)
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{
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if (!test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags))
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return 0;
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if (bio->bi_size + nxt->bi_size > q->max_segment_size)
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return 0;
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if (!bio_has_data(bio))
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return 1;
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if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)))
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return 0;
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/*
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* bio and nxt are contiguous in memory; check if the queue allows
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* these two to be merged into one
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*/
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if (BIO_SEG_BOUNDARY(q, bio, nxt))
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return 1;
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return 0;
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}
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static int blk_hw_contig_segment(struct request_queue *q, struct bio *bio,
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struct bio *nxt)
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{
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if (!bio_flagged(bio, BIO_SEG_VALID))
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blk_recount_segments(q, bio);
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if (!bio_flagged(nxt, BIO_SEG_VALID))
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blk_recount_segments(q, nxt);
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if (bio_has_data(bio) &&
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(!BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)) ||
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BIOVEC_VIRT_OVERSIZE(bio->bi_hw_back_size + nxt->bi_hw_front_size)))
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return 0;
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if (bio->bi_hw_back_size + nxt->bi_hw_front_size > q->max_segment_size)
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return 0;
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return 1;
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}
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/*
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* map a request to scatterlist, return number of sg entries setup. Caller
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* must make sure sg can hold rq->nr_phys_segments entries
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*/
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int blk_rq_map_sg(struct request_queue *q, struct request *rq,
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struct scatterlist *sglist)
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{
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struct bio_vec *bvec, *bvprv;
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struct req_iterator iter;
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struct scatterlist *sg;
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int nsegs, cluster;
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nsegs = 0;
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cluster = test_bit(QUEUE_FLAG_CLUSTER, &q->queue_flags);
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/*
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* for each bio in rq
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*/
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bvprv = NULL;
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sg = NULL;
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rq_for_each_segment(bvec, rq, iter) {
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int nbytes = bvec->bv_len;
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if (bvprv && cluster) {
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if (sg->length + nbytes > q->max_segment_size)
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goto new_segment;
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if (!BIOVEC_PHYS_MERGEABLE(bvprv, bvec))
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goto new_segment;
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if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bvec))
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goto new_segment;
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sg->length += nbytes;
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} else {
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new_segment:
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if (!sg)
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sg = sglist;
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else {
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/*
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* If the driver previously mapped a shorter
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* list, we could see a termination bit
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* prematurely unless it fully inits the sg
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* table on each mapping. We KNOW that there
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* must be more entries here or the driver
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* would be buggy, so force clear the
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* termination bit to avoid doing a full
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* sg_init_table() in drivers for each command.
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*/
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sg->page_link &= ~0x02;
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sg = sg_next(sg);
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}
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sg_set_page(sg, bvec->bv_page, nbytes, bvec->bv_offset);
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nsegs++;
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}
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bvprv = bvec;
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} /* segments in rq */
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if (unlikely(rq->cmd_flags & REQ_COPY_USER) &&
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(rq->data_len & q->dma_pad_mask)) {
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unsigned int pad_len = (q->dma_pad_mask & ~rq->data_len) + 1;
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sg->length += pad_len;
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rq->extra_len += pad_len;
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}
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if (q->dma_drain_size && q->dma_drain_needed(rq)) {
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if (rq->cmd_flags & REQ_RW)
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memset(q->dma_drain_buffer, 0, q->dma_drain_size);
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sg->page_link &= ~0x02;
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sg = sg_next(sg);
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sg_set_page(sg, virt_to_page(q->dma_drain_buffer),
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q->dma_drain_size,
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((unsigned long)q->dma_drain_buffer) &
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(PAGE_SIZE - 1));
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nsegs++;
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rq->extra_len += q->dma_drain_size;
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}
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if (sg)
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sg_mark_end(sg);
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return nsegs;
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}
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EXPORT_SYMBOL(blk_rq_map_sg);
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static inline int ll_new_mergeable(struct request_queue *q,
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struct request *req,
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struct bio *bio)
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{
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int nr_phys_segs = bio_phys_segments(q, bio);
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if (req->nr_phys_segments + nr_phys_segs > q->max_phys_segments) {
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req->cmd_flags |= REQ_NOMERGE;
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if (req == q->last_merge)
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q->last_merge = NULL;
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return 0;
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}
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/*
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* A hw segment is just getting larger, bump just the phys
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* counter.
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*/
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req->nr_phys_segments += nr_phys_segs;
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return 1;
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}
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static inline int ll_new_hw_segment(struct request_queue *q,
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struct request *req,
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struct bio *bio)
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{
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int nr_hw_segs = bio_hw_segments(q, bio);
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int nr_phys_segs = bio_phys_segments(q, bio);
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if (req->nr_hw_segments + nr_hw_segs > q->max_hw_segments
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|| req->nr_phys_segments + nr_phys_segs > q->max_phys_segments) {
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req->cmd_flags |= REQ_NOMERGE;
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if (req == q->last_merge)
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q->last_merge = NULL;
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return 0;
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}
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/*
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* This will form the start of a new hw segment. Bump both
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* counters.
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*/
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req->nr_hw_segments += nr_hw_segs;
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req->nr_phys_segments += nr_phys_segs;
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return 1;
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}
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int ll_back_merge_fn(struct request_queue *q, struct request *req,
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struct bio *bio)
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{
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unsigned short max_sectors;
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int len;
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if (unlikely(blk_pc_request(req)))
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max_sectors = q->max_hw_sectors;
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else
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max_sectors = q->max_sectors;
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if (req->nr_sectors + bio_sectors(bio) > max_sectors) {
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req->cmd_flags |= REQ_NOMERGE;
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if (req == q->last_merge)
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q->last_merge = NULL;
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return 0;
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}
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if (!bio_flagged(req->biotail, BIO_SEG_VALID))
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blk_recount_segments(q, req->biotail);
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if (!bio_flagged(bio, BIO_SEG_VALID))
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blk_recount_segments(q, bio);
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len = req->biotail->bi_hw_back_size + bio->bi_hw_front_size;
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if (!bio_has_data(bio) ||
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(BIOVEC_VIRT_MERGEABLE(__BVEC_END(req->biotail), __BVEC_START(bio))
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&& !BIOVEC_VIRT_OVERSIZE(len))) {
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int mergeable = ll_new_mergeable(q, req, bio);
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if (mergeable) {
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if (req->nr_hw_segments == 1)
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req->bio->bi_hw_front_size = len;
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if (bio->bi_hw_segments == 1)
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bio->bi_hw_back_size = len;
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}
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return mergeable;
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}
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return ll_new_hw_segment(q, req, bio);
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}
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int ll_front_merge_fn(struct request_queue *q, struct request *req,
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struct bio *bio)
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{
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unsigned short max_sectors;
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int len;
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if (unlikely(blk_pc_request(req)))
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max_sectors = q->max_hw_sectors;
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else
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max_sectors = q->max_sectors;
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if (req->nr_sectors + bio_sectors(bio) > max_sectors) {
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req->cmd_flags |= REQ_NOMERGE;
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if (req == q->last_merge)
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q->last_merge = NULL;
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return 0;
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}
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len = bio->bi_hw_back_size + req->bio->bi_hw_front_size;
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if (!bio_flagged(bio, BIO_SEG_VALID))
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blk_recount_segments(q, bio);
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if (!bio_flagged(req->bio, BIO_SEG_VALID))
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blk_recount_segments(q, req->bio);
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if (!bio_has_data(bio) ||
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(BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(req->bio)) &&
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!BIOVEC_VIRT_OVERSIZE(len))) {
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int mergeable = ll_new_mergeable(q, req, bio);
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if (mergeable) {
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if (bio->bi_hw_segments == 1)
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bio->bi_hw_front_size = len;
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if (req->nr_hw_segments == 1)
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req->biotail->bi_hw_back_size = len;
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}
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return mergeable;
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}
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return ll_new_hw_segment(q, req, bio);
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}
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static int ll_merge_requests_fn(struct request_queue *q, struct request *req,
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struct request *next)
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{
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int total_phys_segments;
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int total_hw_segments;
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/*
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* First check if the either of the requests are re-queued
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* requests. Can't merge them if they are.
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*/
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if (req->special || next->special)
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return 0;
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/*
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* Will it become too large?
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*/
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if ((req->nr_sectors + next->nr_sectors) > q->max_sectors)
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return 0;
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total_phys_segments = req->nr_phys_segments + next->nr_phys_segments;
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if (blk_phys_contig_segment(q, req->biotail, next->bio))
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total_phys_segments--;
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if (total_phys_segments > q->max_phys_segments)
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return 0;
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total_hw_segments = req->nr_hw_segments + next->nr_hw_segments;
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if (blk_hw_contig_segment(q, req->biotail, next->bio)) {
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int len = req->biotail->bi_hw_back_size +
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next->bio->bi_hw_front_size;
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/*
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* propagate the combined length to the end of the requests
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*/
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if (req->nr_hw_segments == 1)
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req->bio->bi_hw_front_size = len;
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if (next->nr_hw_segments == 1)
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next->biotail->bi_hw_back_size = len;
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total_hw_segments--;
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}
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if (total_hw_segments > q->max_hw_segments)
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return 0;
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/* Merge is OK... */
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req->nr_phys_segments = total_phys_segments;
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req->nr_hw_segments = total_hw_segments;
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return 1;
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}
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/*
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* Has to be called with the request spinlock acquired
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*/
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static int attempt_merge(struct request_queue *q, struct request *req,
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struct request *next)
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{
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if (!rq_mergeable(req) || !rq_mergeable(next))
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return 0;
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/*
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* not contiguous
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*/
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if (req->sector + req->nr_sectors != next->sector)
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return 0;
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if (rq_data_dir(req) != rq_data_dir(next)
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|| req->rq_disk != next->rq_disk
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|| next->special)
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return 0;
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if (blk_integrity_rq(req) != blk_integrity_rq(next))
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return 0;
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/*
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* If we are allowed to merge, then append bio list
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* from next to rq and release next. merge_requests_fn
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* will have updated segment counts, update sector
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* counts here.
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*/
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if (!ll_merge_requests_fn(q, req, next))
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return 0;
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/*
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* At this point we have either done a back merge
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* or front merge. We need the smaller start_time of
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* the merged requests to be the current request
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* for accounting purposes.
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*/
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if (time_after(req->start_time, next->start_time))
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req->start_time = next->start_time;
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req->biotail->bi_next = next->bio;
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req->biotail = next->biotail;
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req->nr_sectors = req->hard_nr_sectors += next->hard_nr_sectors;
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elv_merge_requests(q, req, next);
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if (req->rq_disk) {
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struct hd_struct *part
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= get_part(req->rq_disk, req->sector);
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disk_round_stats(req->rq_disk);
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req->rq_disk->in_flight--;
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if (part) {
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part_round_stats(part);
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part->in_flight--;
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}
|
|
}
|
|
|
|
req->ioprio = ioprio_best(req->ioprio, next->ioprio);
|
|
|
|
__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;
|
|
}
|