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Date: Thu, 16 Aug 2007 21:20:54 +1000
From: NeilBrown <neilb@...e.de>
To: Jens Axboe <jens.axboe@...cle.com>
Cc: linux-kernel@...r.kernel.org, Tejun Heo <htejun@...il.com>
Subject: [PATCH 001 of 6] Merge blk_recount_segments into blk_recalc_rq_segments
blk_recalc_rq_segments calls blk_recount_segments on each bio,
then does some extra calculations to handle segments that overlap
two bios.
If we merge the code from blk_recount_segments into
blk_recalc_rq_segments, we can process the whole request one bio_vec
at a time, and not need the messy cross-bio calculations.
Then blk_recount_segments can be implemented by calling
blk_recalc_rq_segments, passing it a simple on-stack request which
stores just the bio.
Signed-off-by: Neil Brown <neilb@...e.de>
### Diffstat output
./block/ll_rw_blk.c | 102 ++++++++++++++++++++++------------------------------
1 file changed, 44 insertions(+), 58 deletions(-)
diff .prev/block/ll_rw_blk.c ./block/ll_rw_blk.c
--- .prev/block/ll_rw_blk.c 2007-08-16 17:37:43.000000000 +1000
+++ ./block/ll_rw_blk.c 2007-08-16 17:43:27.000000000 +1000
@@ -42,6 +42,7 @@ static void drive_stat_acct(struct reque
static void init_request_from_bio(struct request *req, struct bio *bio);
static int __make_request(struct request_queue *q, struct bio *bio);
static struct io_context *current_io_context(gfp_t gfp_flags, int node);
+static void blk_recalc_rq_segments(struct request *rq);
/*
* For the allocated request tables
@@ -1209,16 +1210,42 @@ EXPORT_SYMBOL(blk_dump_rq_flags);
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 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 i, nr_phys_segs, nr_hw_segs, seg_size, hw_seg_size, cluster;
+ int seg_size;
+ int hw_seg_size;
+ int cluster;
+ struct bio *bio;
+ int i;
int high, highprv = 1;
+ struct request_queue *q = rq->q;
- if (unlikely(!bio->bi_io_vec))
+ if (!rq->bio)
return;
cluster = q->queue_flags & (1 << QUEUE_FLAG_CLUSTER);
- hw_seg_size = seg_size = nr_phys_segs = nr_hw_segs = 0;
- bio_for_each_segment(bv, bio, i) {
+ hw_seg_size = seg_size = 0;
+ phys_size = hw_size = nr_phys_segs = nr_hw_segs = 0;
+ rq_for_each_bio(bio, rq)
+ bio_for_each_segment(bv, bio, i) {
/*
* the trick here is making sure that a high page is never
* considered part of another segment, since that might
@@ -1244,12 +1271,13 @@ void blk_recount_segments(struct request
}
new_segment:
if (BIOVEC_VIRT_MERGEABLE(bvprv, bv) &&
- !BIOVEC_VIRT_OVERSIZE(hw_seg_size + bv->bv_len)) {
+ !BIOVEC_VIRT_OVERSIZE(hw_seg_size + bv->bv_len))
hw_seg_size += bv->bv_len;
- } else {
+ else {
new_hw_segment:
- if (hw_seg_size > bio->bi_hw_front_size)
- bio->bi_hw_front_size = hw_seg_size;
+ 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++;
}
@@ -1259,15 +1287,15 @@ new_hw_segment:
seg_size = bv->bv_len;
highprv = high;
}
- if (hw_seg_size > bio->bi_hw_back_size)
- bio->bi_hw_back_size = hw_seg_size;
- if (nr_hw_segs == 1 && hw_seg_size > bio->bi_hw_front_size)
- bio->bi_hw_front_size = hw_seg_size;
- bio->bi_phys_segments = nr_phys_segs;
- bio->bi_hw_segments = nr_hw_segs;
- bio->bi_flags |= (1 << BIO_SEG_VALID);
+
+ 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;
}
-EXPORT_SYMBOL(blk_recount_segments);
static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
struct bio *nxt)
@@ -3316,48 +3344,6 @@ void submit_bio(int rw, struct bio *bio)
EXPORT_SYMBOL(submit_bio);
-static void blk_recalc_rq_segments(struct request *rq)
-{
- struct bio *bio, *prevbio = NULL;
- int nr_phys_segs, nr_hw_segs;
- unsigned int phys_size, hw_size;
- struct request_queue *q = rq->q;
-
- if (!rq->bio)
- return;
-
- phys_size = hw_size = nr_phys_segs = nr_hw_segs = 0;
- rq_for_each_bio(bio, rq) {
- /* Force bio hw/phys segs to be recalculated. */
- bio->bi_flags &= ~(1 << BIO_SEG_VALID);
-
- nr_phys_segs += bio_phys_segments(q, bio);
- nr_hw_segs += bio_hw_segments(q, bio);
- if (prevbio) {
- int pseg = phys_size + prevbio->bi_size + bio->bi_size;
- int hseg = hw_size + prevbio->bi_size + bio->bi_size;
-
- if (blk_phys_contig_segment(q, prevbio, bio) &&
- pseg <= q->max_segment_size) {
- nr_phys_segs--;
- phys_size += prevbio->bi_size + bio->bi_size;
- } else
- phys_size = 0;
-
- if (blk_hw_contig_segment(q, prevbio, bio) &&
- hseg <= q->max_segment_size) {
- nr_hw_segs--;
- hw_size += prevbio->bi_size + bio->bi_size;
- } else
- hw_size = 0;
- }
- prevbio = bio;
- }
-
- rq->nr_phys_segments = nr_phys_segs;
- rq->nr_hw_segments = nr_hw_segs;
-}
-
static void blk_recalc_rq_sectors(struct request *rq, int nsect)
{
if (blk_fs_request(rq)) {
-
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