Re: [dm-devel] [PATCH] dm: allow a target to relax discard restrictions

[Christoph Hellwig <hch infradead org>]

On Wed, Apr 27, 2011 at 05:55:38PM -0400, Mike Snitzer wrote:
> A target, like the upcoming thin provisioning target, may want to allow
> discards even if the underlying devices do not support them natively.
> 
> Signed-off-by: Mike Snitzer <snitzer redhat com>

This would work, but I thing it's really confusing to have your
new discards_supported flag in the dm_target structure in addition
to the existing discards_supported in the dm_table and the
num_discard_requests field there.

May we should allow the target to set a tristate

enum discard_enabled {
	NEVER,
	ALWAYS,
	PASSTHROUGH
}

to indicate it's discard support?