[PATCH] mkfs: add discard support

[Christoph Hellwig]

On Wed, Oct 07, 2009 at 03:42:16PM +1100, Dave Chinner wrote:
> On Tue, Oct 06, 2009 at 02:47:58PM -0400, Christoph Hellwig wrote:
> > Call the BLKDISCARD ioctl to mark the whole disk as unused before creating
> > a new filesystem.  This will allow SSDs, Arrays with thin provisioning support
> > and virtual machines to make smarter allocation decisions.
> 
> Good idea, but perhaps the discard should be optional rather than
> unconditional.  My immediate thought was the SOP for setting up
> encrypted devices - fill the empty disk with random data before
> setting up the encrypted device. If you then send it a discard....

Yeah.  I'm fine with making it the default but adding a option to
disable it.