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    SubjectRE: [PATCH] xen/tmem: cleanup
    >>> On 06.02.12 at 17:37, Dan Magenheimer <dan.magenheimer@oracle.com> wrote:
    >> From: Jan Beulich [mailto:JBeulich@suse.com]
    >> Sent: Monday, February 06, 2012 1:13 AM
    >> To: Dan Magenheimer
    >> Cc: Jeremy Fitzhardinge; xen-devel@lists.xensource.com; Konrad Wilk;
    > linux-kernel@vger.kernel.org
    >> Subject: RE: [PATCH] xen/tmem: cleanup
    >>
    >> >>> On 04.02.12 at 17:42, Dan Magenheimer <dan.magenheimer@oracle.com> wrote:
    >> >> From: Jan Beulich [mailto:JBeulich@suse.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@suse.com>
    >> >> Cc: Dan Magenheimer <dan.magenheimer@oracle.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.

    No, this isn't the main reason (as you say further down, this could
    easily be adjusted for) afaict. The main reason is that
    register_xen_selfballooning() is being called from non-modular
    code (xen-balloon.c), which could be made a module too, but in
    turn has at least one reference that wouldn't be nice to become
    an export (balloon_set_new_target()).

    Jan

    > 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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