Date: Mon, 14 Dec 2015 18:11:16 +0300
From: Cyrill Gorcunov <gorcunov@gmail.com>
To: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        Vegard Nossum <vegard.nossum@oracle.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Willy Tarreau <w@1wt.eu>, Andy Lutomirski <luto@amacapital.net>,
        Kees Cook <keescook@google.com>,
        Vladimir Davydov <vdavydov@virtuozzo.com>,
        Konstantin Khlebnikov <koct9i@gmail.com>,
        Pavel Emelyanov <xemul@virtuozzo.com>,
        Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [RFC 1/2] [RFC] mm: Account anon mappings as RLIMIT_DATA
Message-ID: <20151214151116.GE14045@uranus>
References: <20151213201646.839778758@gmail.com>
 <20151214145126.GC3604@chrystal.uk.oracle.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20151214145126.GC3604@chrystal.uk.oracle.com>
User-Agent: Mutt/1.5.24 (2015-08-30)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1345
Lines: 30

On Mon, Dec 14, 2015 at 03:51:26PM +0100, Quentin Casasnovas wrote:
...
> 
> Do we want to fold may_expand_anon_vm() into may_expand_vm() (potentially
> passing it the flags/struct file if needed) so there is just one such
> helper function?  Rationale being that it then gets hard to see what
> restricts what, and it's easy to miss one place.

I tried to make the patch small as possible (because otherwise indeed
I would have to pass @vm_file|@file as additional argument). This won't
be a problem but may_expand_vm is called way more times than
may_expand_anon_vm. That's the only rationale I followed.

> For example, I couldn't find anything preventing a user to
> mmap(MAP_GROWSDOWN) and uses that as a base to get pages that would not be
> accounted for in your patch (making it a poor-man mremap()).

growsup/down stand for stack usage iirc, so it was intentionally
not accounted here.

> 
> I only had a quick look so apologies if this is handled and I missed it :)

thanks for feedback! also take a look on Kostya's patch, I think it's
even better approach (and I like it more than mine).
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/