Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks

From: Linus Torvalds
Date: Fri Mar 11 2016 - 13:25:36 EST

On Fri, Mar 11, 2016 at 9:30 AM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:
> What if we had an ioctl to do these data-leaking operations that took,
> as an extra parameter, an fd to the block device node. They allow
> access if the fd points to the right inode and has FMODE_READ (and LSM
> checks say it's okay). Sure, it's awkward, but it's much safer.

That sounds absolutely horrible.

I'd *much* prefer the suggestion from Alan to simply have a mount-time
option to enable it. That way, you will never get any surprises, and
no "subtle new behavior for somebody who set their system up in a way
that doesn't allow for this".

So you'd have to explicitly say "my setup is ok with hole punching".