Messages in this thread | | | Subject | Re: [RESEND PATCH v2] mm/sparse: clarify pgdat_to_phys | From | David Hildenbrand <> | Date | Fri, 23 Jul 2021 09:10:53 +0200 |
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On 23.07.21 09:01, Miles Chen wrote: > Clarify pgdat_to_phys() by testing if > pgdat == &contig_page_data when CONFIG_NUMA=n. > > contig_page_data is only available when CONFIG_NUMA=n > so we have to use #ifndef here. > > No functional change intended. > > Comment from Mark [1]: > " > ... and I reckon it'd be clearer and more robust to define > pgdat_to_phys() in the same ifdefs as contig_page_data so > that these, stay in-sync. e.g. have: > > | #ifdef CONFIG_NUMA > | #define pgdat_to_phys(x) virt_to_phys(x) > | #else /* CONFIG_NUMA */ > | > | extern struct pglist_data contig_page_data; > | ... > | #define pgdat_to_phys(x) __pa_symbol(&contig_page_data) > | > | #endif /* CONIFIG_NUMA */ > " > > Comment from Mike [2]: > " > I'm not sure a macro is better than a static inline. > > Maybe we'd want to warn if pgdat passed to pgtat_to_phys() is not > &contig_page_data, e.g something like > > static inline phys_addr_t pgdat_to_phys(struct pglist_data *pgdat) > { > if (!IS_ENABLED(CONFIG_NUMA)) { > if (pgdat == &contig_page_data) > return __pa_symbol(&contig_page_data); > else > pr_warn("Unexpected pglist_data pointer!\n"); > } > > return __pa(pgdat); > } > " > > [1] https://lore.kernel.org/linux-arm-kernel/20210615131902.GB47121@C02TD0UTHF1T.local/ > [2] https://lore.kernel.org/patchwork/patch/1452903/#1650759 > > Cc: Mike Rapoport <rppt@kernel.org> > Cc: Mark Rutland <mark.rutland@arm.com> > Signed-off-by: Miles Chen <miles.chen@mediatek.com> > > --- > > Change since v1: > Thanks for Mike's comment, check if pgdat == &contig_page_data, > so it is clearer that we only expect contig_page_data when > CONFIG_NUMA=n. > --- > mm/sparse.c | 7 ++++--- > 1 file changed, 4 insertions(+), 3 deletions(-) > > diff --git a/mm/sparse.c b/mm/sparse.c > index 6326cdf36c4f..f73ff3c124c5 100644 > --- a/mm/sparse.c > +++ b/mm/sparse.c > @@ -348,10 +348,11 @@ size_t mem_section_usage_size(void) > static inline phys_addr_t pgdat_to_phys(struct pglist_data *pgdat) > { > #ifndef CONFIG_NUMA > - return __pa_symbol(pgdat); > -#else > + if (pgdat == &contig_page_data) > + return __pa_symbol(&contig_page_data); > + pr_warn("Unexpected pglist_data pointer!\n");
Shouldn't this rather be a VM_BUG_ON()?
Because it looks like something that should barely happen and we might not want to perform runtime checks on each and every system?
-- Thanks,
David / dhildenb
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