[dm-devel] [PATCH 4/4] Support discard if at least one underlying device supports it

[Alasdair G Kergon]

On Fri, Jul 02, 2010 at 04:47:09PM -0400, Mike Snitzer wrote:

> If a region doesn't support the discard
> DM has no business processing anything related to the discard (barriers
> included).  It is as simple as that.
 
Indeed - if an I/O is going to fail, discover that as early as we can, trying
to avoid the relatively-expensive barrier process whenever we reasonably can.

Alasdair