linux-kernel - Re: + mm-remove-struct-mm_struct-exe_file-et-al.patch added to -mm tree

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Date:	Wed, 1 Apr 2009 03:40:37 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Matt Helsley <matthltc@...ibm.com>
Cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	adobriyan@...il.com, dhowells@...hat.com, ebiederm@...ssion.com,
	hch@....de
Subject: Re: + mm-remove-struct-mm_struct-exe_file-et-al.patch added to -mm
	tree

On 03/31, Matt Helsley wrote:
>
> On Tue, Mar 31, 2009 at 04:40:51PM +0200, Oleg Nesterov wrote:
> >
> > But, as a advocatus diaboli... There was anotrher reason for ->exe_file,
> > iirc.
> >
> > bprm->file->f_op->mmap() can change vma->vm_file, this means proc_exe_link()
> > can report the "wrong" path. The original file is not pinned in this case.
>
> That's _my_ reason for it. However no mainline code does that and hence it was
> not the reason Andrew accepted it.

Good.

> I still prefer ->exe_file because I think it's a win not to walk the
> VMAs with mmap sem when doing a readlink on /proc/*/exe. It's also less
> sensitive to the order in which VMAs appear should that ever change.

I agree with Alexey, I don't think the VMAs walking can be a problem.

But even if it is problem, we could make a much more simple patch
to avoid it? Just add "struct path exe_path" to ->mm, no?

Oleg.

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