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Re: [dm-devel] [PATCH 1/2] blkdev: fix merge_bvec_fn return value checks



On Fri, 5 Mar 2010 17:37:16 +0000
Alasdair G Kergon <agk redhat com> wrote:

> On Thu, Mar 04, 2010 at 06:59:21PM +0100, Lars Ellenberg wrote:
> > +		/* Restricting max_sectors is not enough.
> > +		 * If someone uses bio_add_page to add 8 disjunct 512 byte
> > +		 * partial pages to a bio, it would succeed,
> > +		 * but could still cross a border of whatever restrictions
> > +		 * are below us (raid0 stripe boundary).  An attempted
> > +		 * bio_split would not succeed, because bi_vcnt is 8.
> > +		 * E.g. the xen io layer is known to trigger this.
> > +		 */
> 
> Sounds plausible.
> 
> Do you or anyone readingt his have example messages demonstrating the failure
> when this patch is not applied?

Yes.  This

   http://marc.info/?l=linux-raid&m=126672681521073&w=2

almost certainly refers to that problem.

NeilBrown


> 
> Alasdair.
> 
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