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

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Message-ID: <20120402162733.GI7607@moon>
Date:	Mon, 2 Apr 2012 20:27:33 +0400
From:	Cyrill Gorcunov <gorcunov@...nvz.org>
To:	Konstantin Khlebnikov <khlebnikov@...nvz.org>,
	Oleg Nesterov <oleg@...hat.com>
Cc:	"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>
Subject: Re: [PATCH 6/7] mm: kill vma flag VM_EXECUTABLE

On Mon, Apr 02, 2012 at 08:19:59PM +0400, Konstantin Khlebnikov wrote:
> Oleg Nesterov wrote:
> >On 04/02, Konstantin Khlebnikov wrote:
> >>
> >>In this patch I leave mm->exe_file lockless.
> >>After exec/fork we can change it only for current task and only if mm->mm_users == 1.
> >>
> >>something like this:
> >>
> >>task_lock(current);
> >
> >OK, this protects against the race with get_task_mm()
> >
> >>if (atomic_read(&current->mm->mm_users) == 1)
> >
> >this means PR_SET_MM_EXE_FILE can fail simply because someone did
> >get_task_mm(). Or the caller is multithreaded.
> 
> This is sad, seems like we should keep mm->exe_file protection by mm->mmap_sem.
> So, I'll rework this patch...

Ah, it's about locking. I misundertand it at first.
Oleg, forget about my email then.

	Cyrill
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