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

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Date:	Sat, 31 Mar 2012 22:13:24 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Konstantin Khlebnikov <khlebnikov@...nvz.org>
Cc:	linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Eric Paris <eparis@...hat.com>,
	linux-security-module@...r.kernel.org, oprofile-list@...ts.sf.net,
	Matt Helsley <matthltc@...ibm.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Cyrill Gorcunov <gorcunov@...nvz.org>
Subject: Re: [PATCH 6/7] mm: kill vma flag VM_EXECUTABLE

On 03/31, Konstantin Khlebnikov wrote:
>
> comment from v2.6.25-6245-g925d1c4 ("procfs task exe symlink"),
> where all this stuff was introduced:
>
> > ...
> > This avoids pinning the mounted filesystem.
>
> So, this logic is hooked into every file mmap/unmmap and vma split/merge just to
> fix some hypothetical pinning fs from umounting by mm which already unmapped all
> its executable files, but still alive. Does anyone know any real world example?

This is the question to Matt.

> keep mm->exe_file alive till final mmput().

Please see the recent discussion, http://marc.info/?t=133096188900012

(just in case, the patch itself was deadly wrong, don't look at it ;)

> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -378,7 +378,6 @@ struct mm_struct {
>
>  	/* store ref to file /proc/<pid>/exe symlink points to */
>  	struct file *exe_file;
> -	unsigned long num_exe_file_vmas;

Add Cyrill. This conflicts with
c-r-prctl-add-ability-to-set-new-mm_struct-exe_file.patch in -mm.

Oleg.

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