[dm-devel] [PATCH v2] dm: Fix alignment stacking on partitioned devices

[Mike Snitzer]

On Wed, Dec 23 2009 at  1:07pm -0500,
Mike Snitzer <snitzer at redhat.com> wrote:

> From: Martin K. Petersen <martin.petersen at oracle.com> 
> 
> The DM device limits function passes the start offset within the block
> device to the block layer stacking function.  The stacking function
> expects the provided start offset to be relative to start of the disk
> (request_queue).  Until now DM was passing a start offset that was
> relative to beginning of the partition (block_device), resulting in
> incorrect alignment stacking.
> 
> Add the partition offset to the values passed to blk_stack_limits().
> 
> Also clarify, in the DMWARN message, that the device which caused
> blk_stack_limits() to return failure isn't necessarily misaligned
> itself.  It caused the top-level (DM) device to have inconsistent
> alignment when taken in combination with all previously stacked
> device(s).

Alasdair,

This should be pushed as a fix for 2.6.33.  It should probably go to
stable (2.6.31.y and 2.6.32.y) too.

Mike