Messages in this thread | | | Date | Thu, 6 Jul 2017 08:50:56 +0200 | From | Michal Hocko <> | Subject | Re: [PATCH] mm: disallow early_pfn_to_nid on configurations which do not implement it |
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On Wed 05-07-17 16:00:55, Andrew Morton wrote: > On Tue, 4 Jul 2017 09:58:03 +0200 Michal Hocko <mhocko@kernel.org> wrote: > > > From: Michal Hocko <mhocko@suse.com> > > > > early_pfn_to_nid will return node 0 if both HAVE_ARCH_EARLY_PFN_TO_NID > > and HAVE_MEMBLOCK_NODE_MAP are disabled. It seems we are safe now > > because all architectures which support NUMA define one of them (with an > > exception of alpha which however has CONFIG_NUMA marked as broken) so > > this works as expected. It can get silently and subtly broken too > > easily, though. Make sure we fail the compilation if NUMA is enabled and > > there is no proper implementation for this function. If that ever > > happens we know that either the specific configuration is invalid > > and the fix should either disable NUMA or enable one of the above > > configs. > > > > ... > > > > --- a/include/linux/mmzone.h > > +++ b/include/linux/mmzone.h > > @@ -1055,6 +1055,7 @@ static inline struct zoneref *first_zones_zonelist(struct zonelist *zonelist, > > !defined(CONFIG_HAVE_MEMBLOCK_NODE_MAP) > > static inline unsigned long early_pfn_to_nid(unsigned long pfn) > > { > > + BUILD_BUG_ON(IS_ENABLED(CONFIG_NUMA)); > > return 0; > > } > > #endif > > Wouldn't this be more conventional?
Well, both would lead to a compilation errors which is what I want to achieve. The above is easier to parse IMHO. If you believe a longer ifdef chain is better I won't object.
> --- a/include/linux/mmzone.h~a > +++ a/include/linux/mmzone.h > @@ -1052,7 +1052,8 @@ static inline struct zoneref *first_zone > #endif > > #if !defined(CONFIG_HAVE_ARCH_EARLY_PFN_TO_NID) && \ > - !defined(CONFIG_HAVE_MEMBLOCK_NODE_MAP) > + !defined(CONFIG_HAVE_MEMBLOCK_NODE_MAP) && \ > + !defined(CONFIG_NUMA) > static inline unsigned long early_pfn_to_nid(unsigned long pfn) > { > return 0; > _ >
-- Michal Hocko SUSE Labs
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