linux-kernel - Re: [PATCH] mm: check VMA flags to avoid invalid PROT

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Date:   Fri, 7 Oct 2016 17:22:40 +0100
From:   Lorenzo Stoakes <lstoakes@...il.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Rik van Riel <riel@...hat.com>, Hugh Dickins <hughd@...gle.com>,
        linux-mm <linux-mm@...ck.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        tbsaunde@...aunde.org, robert@...llahan.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] mm: check VMA flags to avoid invalid PROT_NONE NUMA
 balancing

On Fri, Oct 07, 2016 at 08:34:15AM -0700, Linus Torvalds wrote:
> Would you be willing to look at doing that kind of purely syntactic,
> non-semantic cleanup first?

Sure, more than happy to do that! I'll work on a patch for this.

> I think that if we end up having the FOLL_FORCE semantics, we're
> actually better off having an explicit FOLL_FORCE flag, and *not* do
> some kind of implicit "under these magical circumstances we'll force
> it anyway". The implicit thing is what we used to do long long ago, we
> definitely don't want to.

That's a good point, it would definitely be considerably more 'magical', and
expanding the conditions to include uprobes etc. would only add to that.

I wondered about an alternative parameter/flag but it felt like it was
more-or-less FOLL_FORCE in a different form, at which point it may as well
remain FOLL_FORCE :)