[dm-devel] [PATCH, RFC] block: don't allocate a payload for discard request
Mike Snitzer
snitzer at redhat.com
Sat Jun 19 04:25:34 UTC 2010
On Fri, Jun 18 2010 at 10:59am -0400,
Christoph Hellwig <hch at lst.de> wrote:
>
> Allocating a fixed payload for discard requests always was a horrible hack,
> and it's not coming to byte us when adding support for discard in DM/MD.
>
> So change the code to leave the allocation of a payload to the lowlevel
> driver. Unfortunately that means we'll need another hack, which allows
> us to update the various block layer length fields indicating that we
> have a payload. Instead of hiding this in sd.c, which we already partially
> do for UNMAP support add a documented helper in the core block layer for it.
>
> Signed-off-by: Christoph Hellwig <hch at lst.de>
Acked-by: Mike Snitzer <snitzer at redhat.com>
I've built on your patch to successfully implement discard support for
DM (this includes splitting discards that span targets; only the linear
and striped DM targets are supported so far).
The patchset is still a work in progress but is available here (against
2.6.34 at the moment):
http://people.redhat.com/msnitzer/patches/dm-discard/latest/
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