[PATCH] arm,arm64: Conditionalize bio_vec usage

[Thierry Reding]

On Wed, Nov 06, 2013 at 04:21:09PM +0000, Stefano Stabellini wrote:
> On Wed, 6 Nov 2013, Catalin Marinas wrote:
> > On Wed, Nov 06, 2013 at 01:05:17PM +0000, Thierry Reding wrote:
> > > Commit 3d1975b57097 (arm,arm64: do not always merge bio_vec if we are
> > > running on Xen) unconditionally added code using the bio_vec typedefs
> > > which causes build errors on configurations where CONFIG_BLOCK is
> > > disabled.
> > 
> > I guess this commit is only in -next. Would it have the same hash when
> > hitting mainline? Otherwise I'm fine with the patch, maybe Stephano can
> > pick it together with the patch that breaks it.
> 
> I sent this patch earlier today to fix the problem:
> 
> http://marc.info/?l=linux-kernel&m=138374169030300&w=2
> 
> I prefer it to adding more ifdefs. I was going to add it to linux-next
> as soon as possible and then send it upstream together with the rest of
> the series.

I generally prefer to avoid #ifdefs too. Although there are cases where
an #ifdef can be an advantage as well. For instance if you call the
xen_biovec_phys_mergeable() function and don't have CONFIG_BLOCK enabled
the kernel will happily compile but fail to link. That might be somewhat
more difficult to figure out than a compile error. Perhaps it won't.

I have no objections to your proposed patch, and it fixes the build
issues, so I'm good.

Thierry
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