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authorJens Axboe <jens.axboe@oracle.com>2008-01-29 14:04:06 +0100
committerJens Axboe <jens.axboe@oracle.com>2008-01-29 21:55:12 +0100
commitd6d48196961729b79509dcaeeb0f0fb4fbb47d29 (patch)
treee80f5cdc7f0d682a46b816f5a489357f7d622d62 /block/blk-merge.c
parentdb1d08c646e47f3c7835ecdabb51a906ec311f69 (diff)
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block: ll_rw_blk.c split, add blk-merge.c
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Diffstat (limited to 'block/blk-merge.c')
-rw-r--r--block/blk-merge.c485
1 files changed, 485 insertions, 0 deletions
diff --git a/block/blk-merge.c b/block/blk-merge.c
new file mode 100644
index 00000000000..5023f0b0807
--- /dev/null
+++ b/block/blk-merge.c
@@ -0,0 +1,485 @@
+/*
+ * 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)) {
+ 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("blk: request botched\n");
+ rq->nr_sectors = rq->current_nr_sectors;
+ }
+ }
+}
+
+void blk_recalc_rq_segments(struct request *rq)
+{
+ int nr_phys_segs;
+ int nr_hw_segs;
+ unsigned int phys_size;
+ unsigned int hw_size;
+ struct bio_vec *bv, *bvprv = NULL;
+ int seg_size;
+ int hw_seg_size;
+ int cluster;
+ struct req_iterator iter;
+ int high, highprv = 1;
+ struct request_queue *q = rq->q;
+
+ if (!rq->bio)
+ return;
+
+ cluster = q->queue_flags & (1 << QUEUE_FLAG_CLUSTER);
+ hw_seg_size = seg_size = 0;
+ phys_size = hw_size = nr_phys_segs = nr_hw_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_hw_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;
+ if (BIOVEC_VIRT_OVERSIZE(hw_seg_size + bv->bv_len))
+ goto new_hw_segment;
+
+ seg_size += bv->bv_len;
+ hw_seg_size += bv->bv_len;
+ bvprv = bv;
+ continue;
+ }
+new_segment:
+ if (BIOVEC_VIRT_MERGEABLE(bvprv, bv) &&
+ !BIOVEC_VIRT_OVERSIZE(hw_seg_size + bv->bv_len))
+ hw_seg_size += bv->bv_len;
+ else {
+new_hw_segment:
+ if (nr_hw_segs == 1 &&
+ hw_seg_size > rq->bio->bi_hw_front_size)
+ rq->bio->bi_hw_front_size = hw_seg_size;
+ hw_seg_size = BIOVEC_VIRT_START_SIZE(bv) + bv->bv_len;
+ nr_hw_segs++;
+ }
+
+ nr_phys_segs++;
+ bvprv = bv;
+ seg_size = bv->bv_len;
+ highprv = high;
+ }
+
+ if (nr_hw_segs == 1 &&
+ hw_seg_size > rq->bio->bi_hw_front_size)
+ rq->bio->bi_hw_front_size = hw_seg_size;
+ if (hw_seg_size > rq->biotail->bi_hw_back_size)
+ rq->biotail->bi_hw_back_size = hw_seg_size;
+ rq->nr_phys_segments = nr_phys_segs;
+ rq->nr_hw_segments = nr_hw_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_hw_segments = rq.nr_hw_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 (!(q->queue_flags & (1 << QUEUE_FLAG_CLUSTER)))
+ return 0;
+
+ if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)))
+ return 0;
+ if (bio->bi_size + nxt->bi_size > q->max_segment_size)
+ return 0;
+
+ /*
+ * bio and nxt are contigous 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 int blk_hw_contig_segment(struct request_queue *q, struct bio *bio,
+ struct bio *nxt)
+{
+ if (unlikely(!bio_flagged(bio, BIO_SEG_VALID)))
+ blk_recount_segments(q, bio);
+ if (unlikely(!bio_flagged(nxt, BIO_SEG_VALID)))
+ blk_recount_segments(q, nxt);
+ if (!BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)) ||
+ BIOVEC_VIRT_OVERSIZE(bio->bi_hw_back_size + nxt->bi_hw_front_size))
+ return 0;
+ if (bio->bi_hw_back_size + nxt->bi_hw_front_size > q->max_segment_size)
+ return 0;
+
+ return 1;
+}
+
+/*
+ * 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 = q->queue_flags & (1 << QUEUE_FLAG_CLUSTER);
+
+ /*
+ * 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 (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++;
+ }
+
+ 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_hw_segs = bio_hw_segments(q, bio);
+ int nr_phys_segs = bio_phys_segments(q, bio);
+
+ if (req->nr_hw_segments + nr_hw_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_hw_segments += nr_hw_segs;
+ 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;
+ int len;
+
+ 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 (unlikely(!bio_flagged(req->biotail, BIO_SEG_VALID)))
+ blk_recount_segments(q, req->biotail);
+ if (unlikely(!bio_flagged(bio, BIO_SEG_VALID)))
+ blk_recount_segments(q, bio);
+ len = req->biotail->bi_hw_back_size + bio->bi_hw_front_size;
+ if (BIOVEC_VIRT_MERGEABLE(__BVEC_END(req->biotail), __BVEC_START(bio)) &&
+ !BIOVEC_VIRT_OVERSIZE(len)) {
+ int mergeable = ll_new_mergeable(q, req, bio);
+
+ if (mergeable) {
+ if (req->nr_hw_segments == 1)
+ req->bio->bi_hw_front_size = len;
+ if (bio->bi_hw_segments == 1)
+ bio->bi_hw_back_size = len;
+ }
+ return mergeable;
+ }
+
+ 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;
+ int len;
+
+ 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;
+ }
+ len = bio->bi_hw_back_size + req->bio->bi_hw_front_size;
+ if (unlikely(!bio_flagged(bio, BIO_SEG_VALID)))
+ blk_recount_segments(q, bio);
+ if (unlikely(!bio_flagged(req->bio, BIO_SEG_VALID)))
+ blk_recount_segments(q, req->bio);
+ if (BIOVEC_VIRT_MERGEABLE(__BVEC_END(bio), __BVEC_START(req->bio)) &&
+ !BIOVEC_VIRT_OVERSIZE(len)) {
+ int mergeable = ll_new_mergeable(q, req, bio);
+
+ if (mergeable) {
+ if (bio->bi_hw_segments == 1)
+ bio->bi_hw_front_size = len;
+ if (req->nr_hw_segments == 1)
+ req->biotail->bi_hw_back_size = len;
+ }
+ return mergeable;
+ }
+
+ 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;
+ int total_hw_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;
+
+ total_hw_segments = req->nr_hw_segments + next->nr_hw_segments;
+ if (blk_hw_contig_segment(q, req->biotail, next->bio)) {
+ int len = req->biotail->bi_hw_back_size + next->bio->bi_hw_front_size;
+ /*
+ * propagate the combined length to the end of the requests
+ */
+ if (req->nr_hw_segments == 1)
+ req->bio->bi_hw_front_size = len;
+ if (next->nr_hw_segments == 1)
+ next->biotail->bi_hw_back_size = len;
+ total_hw_segments--;
+ }
+
+ if (total_hw_segments > q->max_hw_segments)
+ return 0;
+
+ /* Merge is OK... */
+ req->nr_phys_segments = total_phys_segments;
+ req->nr_hw_segments = total_hw_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 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) {
+ disk_round_stats(req->rq_disk);
+ req->rq_disk->in_flight--;
+ }
+
+ 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;
+}