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Date: Tue, 12 Aug 2014 20:14:45 +0100
From: Al Viro <viro@ZenIV.linux.org.uk>
To: David Herrmann <dh.herrmann@gmail.com>
Cc: linux-kernel@vger.kernel.org,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andrew Morton <akpm@linux-foundation.org>, Tejun Heo <tj@kernel.org>,
        linux-fsdevel@vger.kernel.org, Theodore Tso <tytso@mit.edu>,
        Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH RFC 0/4] VFS revoke()
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On Tue, Aug 12, 2014 at 08:54:04PM +0200, David Herrmann wrote:

> Open questions:
>  * Obviously, we need to protect all calls into file->f_op->xyz(). This series
>    provides enter_file() and leave_file() that can be used like:
>       if (enter_file(file))
>           retval = file->f_op->xyz(file, ...);
>       else
>           retval = -ENODEV;
>    Question is, should we do this at the time we actually invoke those
>    callbacks or should we do it at the syscall-entry time?

The former, obviously.  The real bitch is around mmap - you don't need
that for evdev, but generic solution would better deal with that kind
of crap.

I'll post a review once I'm done with Eric's patchset; hopefully tonight or
tomorrow morning.