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

[Alasdair G Kergon]

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?

Alasdair.