RE: [PATCH] xen/tmem: cleanup

From: Dan Magenheimer
Date: Mon Feb 06 2012 - 11:37:54 EST

> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: Monday, February 06, 2012 1:13 AM
> To: Dan Magenheimer
> Cc: Jeremy Fitzhardinge; xen-devel@xxxxxxxxxxxxxxxxxxx; Konrad Wilk; linux-kernel@xxxxxxxxxxxxxxx
> Subject: RE: [PATCH] xen/tmem: cleanup
> >>> On 04.02.12 at 17:42, Dan Magenheimer <dan.magenheimer@xxxxxxxxxx> wrote:
> >> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> >> Subject: [PATCH] xen/tmem: cleanup
> >>
> >> Use 'bool' for boolean variables. Do proper section placement.
> >> Eliminate an unnecessary export.
> >>
> >> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> >> Cc: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>
> >>
> >> -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 ;-)

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