[lvm-devel] Re: rebased snapshot-merge patches

[Mike Snitzer]

On Fri, Sep 11 2009 at  2:51am -0400,
Mike Snitzer <snitzer at redhat.com> wrote:

> Mikulas,
> 
> I ran with your suggestion and it works quite well (results below).
...
> The changes are detailed at the end of this mail.  I still have a "TODO"
> that you'll see in the patch that speaks to needing to have
> snapshot_merge_process() check all origin chunks via __chunk_is_tracked()
> rather than just the one check of the first chunk.  Your feedback here
> would be much appreciated.  I'm not completely clear on the intent of
> the __chunk_is_tracked() check there and what it now needs to do.

I believe I've sorted this out.  The TODO should've read something like:
snapshot_merge_process() should delay the merging of _all_ chunks
that have in-progress writes; not just the first chunk in the region
that is to be merged.

The revised patch (relative to Jon's unified snapshot tree) is here:
http://people.redhat.com/msnitzer/patches/snapshot-merge/kernel_unified/2.6.31/dm-snapshot-merge-use-larger-io-when-merging.patch

Pretty sure it _should_ work; but can't test until we get this unified
snapshot patchset working properly.