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![Kent Overstreet](/assets/img/avatar_default.png)
bio_iovec_idx() and __bio_iovec() don't have any valid uses anymore - previous users have been converted to bio_iovec_iter() or other methods. __BVEC_END() has to go too - the bvec array can't be used directly for the last biovec because we might only be using the first portion of it, we have to iterate over the bvec array with bio_for_each_segment() which checks against the current value of bi_iter.bi_size. Signed-off-by: Kent Overstreet <kmo@daterainc.com> Cc: Jens Axboe <axboe@kernel.dk>
557 lines
13 KiB
C
557 lines
13 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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static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
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struct bio *bio)
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{
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struct bio_vec bv, bvprv = { NULL };
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int cluster, high, highprv = 1;
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unsigned int seg_size, nr_phys_segs;
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struct bio *fbio, *bbio;
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struct bvec_iter iter;
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if (!bio)
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return 0;
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fbio = bio;
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cluster = blk_queue_cluster(q);
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seg_size = 0;
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nr_phys_segs = 0;
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for_each_bio(bio) {
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bio_for_each_segment(bv, bio, iter) {
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/*
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* the trick here is making sure that a high page is
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* never considered part of another segment, since that
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* might change with the bounce page.
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*/
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high = page_to_pfn(bv.bv_page) > queue_bounce_pfn(q);
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if (!high && !highprv && cluster) {
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if (seg_size + bv.bv_len
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> queue_max_segment_size(q))
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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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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 (nr_phys_segs == 1 && seg_size >
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fbio->bi_seg_front_size)
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fbio->bi_seg_front_size = seg_size;
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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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bbio = bio;
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}
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if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size)
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fbio->bi_seg_front_size = seg_size;
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if (seg_size > bbio->bi_seg_back_size)
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bbio->bi_seg_back_size = seg_size;
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return nr_phys_segs;
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}
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void blk_recalc_rq_segments(struct request *rq)
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{
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rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio);
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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 bio *nxt = bio->bi_next;
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bio->bi_next = NULL;
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bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio);
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bio->bi_next = nxt;
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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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struct bio_vec end_bv, nxt_bv;
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struct bvec_iter iter;
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if (!blk_queue_cluster(q))
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return 0;
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if (bio->bi_seg_back_size + nxt->bi_seg_front_size >
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queue_max_segment_size(q))
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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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bio_for_each_segment(end_bv, bio, iter)
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if (end_bv.bv_len == iter.bi_size)
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break;
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nxt_bv = bio_iovec(nxt);
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if (!BIOVEC_PHYS_MERGEABLE(&end_bv, &nxt_bv))
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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 (BIOVEC_SEG_BOUNDARY(q, &end_bv, &nxt_bv))
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return 1;
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return 0;
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}
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static inline void
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__blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec,
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struct scatterlist *sglist, struct bio_vec *bvprv,
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struct scatterlist **sg, int *nsegs, int *cluster)
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{
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int nbytes = bvec->bv_len;
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if (*sg && *cluster) {
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if ((*sg)->length + nbytes > queue_max_segment_size(q))
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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_unmark_end(*sg);
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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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}
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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 = blk_queue_cluster(q);
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/*
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* for each bio in rq
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*/
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sg = NULL;
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rq_for_each_segment(bvec, rq, iter) {
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__blk_segment_map_sg(q, &bvec, sglist, &bvprv, &sg,
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&nsegs, &cluster);
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} /* segments in rq */
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if (unlikely(rq->cmd_flags & REQ_COPY_USER) &&
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(blk_rq_bytes(rq) & q->dma_pad_mask)) {
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unsigned int pad_len =
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(q->dma_pad_mask & ~blk_rq_bytes(rq)) + 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_WRITE)
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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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/**
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* blk_bio_map_sg - map a bio to a scatterlist
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* @q: request_queue in question
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* @bio: bio being mapped
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* @sglist: scatterlist being mapped
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*
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* Note:
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* Caller must make sure sg can hold bio->bi_phys_segments entries
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*
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* Will return the number of sg entries setup
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*/
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int blk_bio_map_sg(struct request_queue *q, struct bio *bio,
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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 scatterlist *sg;
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int nsegs, cluster;
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struct bvec_iter iter;
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nsegs = 0;
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cluster = blk_queue_cluster(q);
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sg = NULL;
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bio_for_each_segment(bvec, bio, iter) {
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__blk_segment_map_sg(q, &bvec, sglist, &bvprv, &sg,
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&nsegs, &cluster);
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} /* segments in bio */
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if (sg)
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sg_mark_end(sg);
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BUG_ON(bio->bi_phys_segments && nsegs > bio->bi_phys_segments);
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return nsegs;
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}
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EXPORT_SYMBOL(blk_bio_map_sg);
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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_phys_segs = bio_phys_segments(q, bio);
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if (req->nr_phys_segments + nr_phys_segs > queue_max_segments(q))
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goto no_merge;
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if (bio_integrity(bio) && blk_integrity_merge_bio(q, req, bio))
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goto no_merge;
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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_phys_segments += nr_phys_segs;
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return 1;
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no_merge:
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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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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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if (blk_rq_sectors(req) + bio_sectors(bio) >
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blk_rq_get_max_sectors(req)) {
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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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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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if (blk_rq_sectors(req) + bio_sectors(bio) >
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blk_rq_get_max_sectors(req)) {
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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(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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return ll_new_hw_segment(q, req, bio);
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}
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/*
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* blk-mq uses req->special to carry normal driver per-request payload, it
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* does not indicate a prepared command that we cannot merge with.
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*/
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static bool req_no_special_merge(struct request *req)
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{
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struct request_queue *q = req->q;
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return !q->mq_ops && req->special;
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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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unsigned int seg_size =
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req->biotail->bi_seg_back_size + next->bio->bi_seg_front_size;
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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_no_special_merge(req) || req_no_special_merge(next))
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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 ((blk_rq_sectors(req) + blk_rq_sectors(next)) >
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blk_rq_get_max_sectors(req))
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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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if (req->nr_phys_segments == 1)
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req->bio->bi_seg_front_size = seg_size;
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if (next->nr_phys_segments == 1)
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next->biotail->bi_seg_back_size = seg_size;
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total_phys_segments--;
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}
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if (total_phys_segments > queue_max_segments(q))
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return 0;
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if (blk_integrity_rq(req) && blk_integrity_merge_rq(q, req, next))
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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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return 1;
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}
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/**
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* blk_rq_set_mixed_merge - mark a request as mixed merge
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* @rq: request to mark as mixed merge
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*
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* Description:
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* @rq is about to be mixed merged. Make sure the attributes
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* which can be mixed are set in each bio and mark @rq as mixed
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* merged.
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*/
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void blk_rq_set_mixed_merge(struct request *rq)
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{
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unsigned int ff = rq->cmd_flags & REQ_FAILFAST_MASK;
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struct bio *bio;
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if (rq->cmd_flags & REQ_MIXED_MERGE)
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return;
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/*
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* @rq will no longer represent mixable attributes for all the
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* contained bios. It will just track those of the first one.
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* Distributes the attributs to each bio.
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*/
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for (bio = rq->bio; bio; bio = bio->bi_next) {
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WARN_ON_ONCE((bio->bi_rw & REQ_FAILFAST_MASK) &&
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(bio->bi_rw & REQ_FAILFAST_MASK) != ff);
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bio->bi_rw |= ff;
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}
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rq->cmd_flags |= REQ_MIXED_MERGE;
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}
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static void blk_account_io_merge(struct request *req)
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{
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if (blk_do_io_stat(req)) {
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struct hd_struct *part;
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int cpu;
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cpu = part_stat_lock();
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part = req->part;
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part_round_stats(cpu, part);
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part_dec_in_flight(part, rq_data_dir(req));
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hd_struct_put(part);
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part_stat_unlock();
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}
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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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if (!blk_check_merge_flags(req->cmd_flags, next->cmd_flags))
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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 (blk_rq_pos(req) + blk_rq_sectors(req) != blk_rq_pos(next))
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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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|| req_no_special_merge(next))
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return 0;
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if (req->cmd_flags & REQ_WRITE_SAME &&
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!blk_write_same_mergeable(req->bio, next->bio))
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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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* If failfast settings disagree or any of the two is already
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* a mixed merge, mark both as mixed before proceeding. This
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* makes sure that all involved bios have mixable attributes
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* set properly.
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*/
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if ((req->cmd_flags | next->cmd_flags) & REQ_MIXED_MERGE ||
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(req->cmd_flags & REQ_FAILFAST_MASK) !=
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(next->cmd_flags & REQ_FAILFAST_MASK)) {
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blk_rq_set_mixed_merge(req);
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blk_rq_set_mixed_merge(next);
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}
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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->__data_len += blk_rq_bytes(next);
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elv_merge_requests(q, req, next);
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/*
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* 'next' is going away, so update stats accordingly
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*/
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blk_account_io_merge(next);
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req->ioprio = ioprio_best(req->ioprio, next->ioprio);
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if (blk_rq_cpu_valid(next))
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req->cpu = next->cpu;
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/* owner-ship of bio passed from next to req */
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next->bio = NULL;
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__blk_put_request(q, next);
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return 1;
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}
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int attempt_back_merge(struct request_queue *q, struct request *rq)
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{
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struct request *next = elv_latter_request(q, rq);
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if (next)
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return attempt_merge(q, rq, next);
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return 0;
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}
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int attempt_front_merge(struct request_queue *q, struct request *rq)
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{
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struct request *prev = elv_former_request(q, rq);
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|
|
|
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 || req_no_special_merge(rq))
|
|
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_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;
|
|
}
|