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SubjectRe: [BIO] Bounce queue in bio_add_page
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On Mon, Nov 03, 2003 at 01:25:00PM +0100, Jens Axboe wrote:
>
> I think the best fix would be to simply not allow more than one page
> that needs to be bounced to a bio. The problem is that the whole bio and

Here is an alternative solution, what if we simply disregarded high
pages when doing the recount? Something like this,
--
Debian GNU/Linux 3.0 is out! ( http://www.debian.org/ )
Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
Index: kernel-source-2.5/drivers/block/ll_rw_blk.c
===================================================================
RCS file: /home/gondolin/herbert/src/CVS/debian/kernel-source-2.5/drivers/block/ll_rw_blk.c,v
retrieving revision 1.9
diff -u -r1.9 ll_rw_blk.c
--- kernel-source-2.5/drivers/block/ll_rw_blk.c 11 Oct 2003 06:29:20 -0000 1.9
+++ kernel-source-2.5/drivers/block/ll_rw_blk.c 3 Nov 2003 20:48:53 -0000
@@ -816,6 +816,7 @@
{
struct bio_vec *bv, *bvprv = NULL;
int i, nr_phys_segs, nr_hw_segs, seg_size, cluster;
+ int high, highprv = 1;

if (unlikely(!bio->bi_io_vec))
return;
@@ -823,7 +824,10 @@
cluster = q->queue_flags & (1 << QUEUE_FLAG_CLUSTER);
seg_size = nr_phys_segs = nr_hw_segs = 0;
bio_for_each_segment(bv, bio, i) {
- if (bvprv && cluster) {
+ 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))
@@ -836,12 +840,15 @@
continue;
}
new_segment:
- if (!bvprv || !BIOVEC_VIRT_MERGEABLE(bvprv, bv))
+ if (!BIOVEC_VIRT_MERGEABLE(bvprv, bv)) {
+new_hw_segment:
nr_hw_segs++;
+ }

nr_phys_segs++;
bvprv = bv;
seg_size = bv->bv_len;
+ highprv = high;
}

bio->bi_phys_segments = nr_phys_segs;
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