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Subject[PATCH 004 of 35] 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. This function is only temporary and will go away
completely by the end of this patch series.

This allows us to remove rq_for_each_bio


Signed-off-by: Neil Brown <neilb@suse.de>

### Diffstat output
./block/ll_rw_blk.c | 125 ++++++++++++++++++++---------------------------
./include/linux/blkdev.h | 3 -
2 files changed, 55 insertions(+), 73 deletions(-)
diff .prev/block/ll_rw_blk.c ./block/ll_rw_blk.c
--- .prev/block/ll_rw_blk.c 2007-07-31 11:20:44.000000000 +1000
+++ ./block/ll_rw_blk.c 2007-07-31 11:20:46.000000000 +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
@@ -1209,65 +1210,91 @@ EXPORT_SYMBOL(blk_dump_rq_flags);

void blk_recount_segments(struct request_queue *q, struct bio *bio)
{
- struct bio_vec *bv, *bvprv = NULL;
- int i, nr_phys_segs, nr_hw_segs, seg_size, hw_seg_size, cluster;
+ 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;
+ struct bio_vec bvprv = {0};
+ int seg_size;
+ int hw_seg_size;
+ int cluster;
+ struct req_iterator 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_segment(rq, i, bv) {
/*
* 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;
+ 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)
+ if (seg_size + bv.bv_len > q->max_segment_size)
goto new_segment;
- if (!BIOVEC_PHYS_MERGEABLE(bvprv, bv))
+ if (!BIOVEC_PHYS_MERGEABLE(&bvprv, &bv))
goto new_segment;
- if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bv))
+ if (!BIOVEC_SEG_BOUNDARY(q, &bvprv, &bv))
goto new_segment;
- if (BIOVEC_VIRT_OVERSIZE(hw_seg_size + bv->bv_len))
+ 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;
+ 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 {
+ 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 (hw_seg_size > bio->bi_hw_front_size)
- bio->bi_hw_front_size = hw_seg_size;
- hw_seg_size = BIOVEC_VIRT_START_SIZE(bv) + bv->bv_len;
+ 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;
+ 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)
@@ -3311,48 +3338,6 @@ 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)) {
diff .prev/include/linux/blkdev.h ./include/linux/blkdev.h
--- .prev/include/linux/blkdev.h 2007-07-31 11:20:44.000000000 +1000
+++ ./include/linux/blkdev.h 2007-07-31 11:20:46.000000000 +1000
@@ -650,9 +650,6 @@ struct req_iterator {
)
#define rq_iter_last(rq, _iter) (_iter.bio->bi_next == NULL && \
_iter.i == _iter.bio->bi_vcnt - 1)
-#define rq_for_each_bio(_bio, rq) \
- if ((rq->bio)) \
- for (_bio = (rq)->bio; _bio; _bio = _bio->bi_next)

extern int blk_register_queue(struct gendisk *disk);
extern void blk_unregister_queue(struct gendisk *disk);
-
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