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SubjectRe: [PATCH] Fix panic in 2.6 with bounced bio and dm
Mark Haverkamp <markh@osdl.org> wrote:
>
>
> Last September a fix was checked in for a memory leak problem in
> bounce_end_io causing the entire bio to be checked. This ended up
> causing some dm cloned bios that had bounce buffers to free NULL pages
> because their bi_idx can be non-zero. This patch skips NULL pages in
> the bio's bio_vec. I'm not sure if this is the most optimal fix but I
> think that it is safe since bvec_alloc memsets the bio_vec to zero.
>

Thanks, we should get fixed for 2.6.11.

It seems very weird for dm to be shoving NULL page*'s into the middle of a
bio's bvec array, so your fix might end up being a workaround pending a
closer look at what's going on in there.

>
> ===== mm/highmem.c 1.55 vs edited =====
> --- 1.55/mm/highmem.c 2005-01-07 21:44:13 -08:00
> +++ edited/mm/highmem.c 2005-02-25 07:54:21 -08:00
> @@ -319,7 +319,7 @@
> */
> __bio_for_each_segment(bvec, bio, i, 0) {
> org_vec = bio_orig->bi_io_vec + i;
> - if (bvec->bv_page == org_vec->bv_page)
> + if (!bvec->bv_page || bvec->bv_page == org_vec->bv_page)
> continue;
>
> mempool_free(bvec->bv_page, pool);
>
> --
> Mark Haverkamp <markh@osdl.org>
>
> -
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