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Date: Fri, 11 Mar 2016 10:25:30 -0800
Message-ID: <CA+55aFxQOgDjL643J33d-3q7gYGvyN84vCn4qJq-Ox8E-WRx9w@mail.gmail.com>
Subject: Re: [PATCH 2/2] block: create ioctl to discard-or-zeroout a range of blocks
From: Linus Torvalds <torvalds@linux-foundation.org>
To: Andy Lutomirski <luto@amacapital.net>
Cc: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>,
        Ric Wheeler <rwheeler@redhat.com>, "Theodore Ts'o" <tytso@mit.edu>,
        Gregory Farnum <greg@gregs42.com>, Dave Chinner <david@fromorbit.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        Christoph Hellwig <hch@infradead.org>,
        "Darrick J. Wong" <darrick.wong@oracle.com>,
        Jens Axboe <axboe@kernel.dk>,
        Andrew Morton <akpm@linux-foundation.org>,
        Linux API <linux-api@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        shane.seymour@hpe.com, Bruce Fields <bfields@fieldses.org>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>,
        Jeff Layton <jlayton@poochiereds.net>,
        Eric Sandeen <esandeen@redhat.com>
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On Fri, Mar 11, 2016 at 9:30 AM, Andy Lutomirski <luto@amacapital.net> 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".

                Linus