linux-kernel - Re: [PATCH 6/7] mm: kill vma flag VM

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Date:	Fri, 06 Apr 2012 08:36:03 +0400
From:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Matt Helsley <matthltc@...ibm.com>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	Oleg Nesterov <oleg@...hat.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Eric Paris <eparis@...hat.com>,
	"linux-security-module@...r.kernel.org" 
	<linux-security-module@...r.kernel.org>,
	"oprofile-list@...ts.sf.net" <oprofile-list@...ts.sf.net>,
	Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [PATCH 6/7] mm: kill vma flag VM_EXECUTABLE

Linus Torvalds wrote:
> On Thu, Apr 5, 2012 at 2:44 PM, Matt Helsley<matthltc@...ibm.com>  wrote:
>>
>> I don't think the definition of an ABI is whether there's documentation
>> for it. It's whether the interface is used or not. At least that's the
>> impression I've gotten from reading Linus' rants over the years.
>
> Yes.
>
> That said, I *do* have some very dim memory of us having had real
> issues with the /proc/<pid>/exe thing and having regressions due to
> holding refcounts to executables that were a.out binaries and not
> demand-loaded. And people wanting to unmount filesystems despite the
> binaries being live.
>
> That said, I suspect that whatever issues we used to have with that
> are pretty long gone. I don't think people use non-mmap'ed binaries
> any more. So I think we can try it and see. And revert if somebody
> actually notices and has problems.

Instead of tracking count of vma with VM_EXECUTABLE bit we can track
count of vma with vma->vm_file == mm->exe_file, this will be nearly
the same behaviour. This was in early version of my patch, but I prefer
to go deeper. So, we can revert it without introducing VM_EXECUTABLE again.

>
>                      Linus

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