linux-kernel - Re: [PATCH] Reimplement old functionality of vm_munmap to vm_munmap

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Message-ID: <20131119170416.GD10323@ZenIV.linux.org.uk>
Date:	Tue, 19 Nov 2013 17:04:16 +0000
From:	Al Viro <viro@...IV.linux.org.uk>
To:	James Custer <jcuster@....com>
Cc:	linux-mm@...ck.org, Rik van Riel <riel@...hat.com>,
	Mel Gorman <mgorman@...e.de>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Jiang Liu <jiang.liu@...wei.com>,
	Michel Lespinasse <walken@...gle.com>,
	Hugh Dickins <hughd@...gle.com>,
	Oleg Nesterov <oleg@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Reimplement old functionality of vm_munmap to
 vm_munmap_mm

On Tue, Nov 19, 2013 at 10:29:52AM -0600, James Custer wrote:
> Commit bfce281c287a427d0841fadf5d59242757b4e620 killed the mm parameter to
> vm_munmap. Although the mm parameter was not used in any in-tree kernel
> modules, it is used by some out-of-tree modules.
> 
> We create a new function vm_munmap_mm that has the same functionality as
> vm_munmap, whereas vm_munmap uses current->mm, vm_munmap_mm takes the mm as
> a paramter.
> 
> Since this is a newly exported symbol it is marked EXPORT_SYMBOL_GPL.

Which modules and what are they doing with it?  More to the point,
what prevents races with e.g. dumping core?  And that's not an idle
question - for example, fs/aio.c used to contain very unpleasant
races of that kind exactly because it was playing games with modifying
->mm other than current->mm.

In other words, NAK.
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