linux-kernel - RE: [PATCH] xen/tmem: cleanup

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Message-ID: <e871af1b-8003-4d3d-8fde-ea40545ff9fe@default>
Date:	Mon, 6 Feb 2012 08:37:17 -0800 (PST)
From:	Dan Magenheimer <dan.magenheimer@...cle.com>
To:	Jan Beulich <JBeulich@...e.com>
Cc:	Jeremy Fitzhardinge <jeremy@...p.org>,
	xen-devel@...ts.xensource.com,
	Konrad Wilk <konrad.wilk@...cle.com>,
	linux-kernel@...r.kernel.org
Subject: RE: [PATCH] xen/tmem: cleanup

> From: Jan Beulich [mailto:JBeulich@...e.com]
> Sent: Monday, February 06, 2012 1:13 AM
> To: Dan Magenheimer
> Cc: Jeremy Fitzhardinge; xen-devel@...ts.xensource.com; Konrad Wilk; linux-kernel@...r.kernel.org
> Subject: RE: [PATCH] xen/tmem: cleanup
> 
> >>> On 04.02.12 at 17:42, Dan Magenheimer <dan.magenheimer@...cle.com> wrote:
> >>  From: Jan Beulich [mailto:JBeulich@...e.com]
> >> Subject: [PATCH] xen/tmem: cleanup
> >>
> >> Use 'bool' for boolean variables. Do proper section placement.
> >> Eliminate an unnecessary export.
> >>
> >> Signed-off-by: Jan Beulich <jbeulich@...e.com>
> >> Cc: Dan Magenheimer <dan.magenheimer@...cle.com>
> >>
> >> -int tmem_enabled __read_mostly;
> >> -EXPORT_SYMBOL(tmem_enabled);
> >> +bool __read_mostly tmem_enabled = false;
> >
> > tmem_enabled is used in xen/drivers/xen-selfballoon.c
> 
> Which can't be built as a module, and hence the symbol doesn't need
> exporting. This patch (of course, I'm tempted to say) survived build
> testing.

Yes, correct.  BUT... I think only the reason xen-selfballoon.c
can't be built as a module is because the MM variable vm_committed_as
(or an access function) is not exported.  Ideally xen-selfballoon.c
probably should be a module but putting a core MM change in
the critical path of a Xen-only-related enhancement seemed
a recipe for sure failure.

Konrad, if you (1) disagree entirely, or (2) want to remove the
tmem_enabled EXPORT_SYMBOL now and add it back later if/when
the core MM change happens, I'll leave that up to you.

If (2), the MM change should be added to the minor-tmem-related-
changes-that-need-to-be-eventually-upstreamed list ;-)

Dan
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