On Fri, Jul 23, 2021 at 08:33:42PM +0800, Miles Chen wrote: > Clarify pgdat_to_phys() by testing if > pgdat == &contig_page_data when CONFIG_NUMA=n. > > We only expect contig_page_data in such case, so we > use &contig_page_data directly instead of pgdat. > > No functional change intended when CONFIG_BUG_VM=n. > > 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 */ > " > > [1] https://lore.kernel.org/linux-arm-kernel/20210615131902.GB47121@C02TD0UTHF1T.local/ > > Cc: Mike Rapoport <rppt@xxxxxxxxxx> > Cc: Mark Rutland <mark.rutland@xxxxxxx> > Cc: David Hildenbrand <david@xxxxxxxxxx> > Signed-off-by: Miles Chen <miles.chen@xxxxxxxxxxxx> Acked-by: Mike Rapoport <rppt@xxxxxxxxxxxxx> > > -- > > 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. > > Change since v2: > use VM_BUG_ON() to avoid runtime checking when CONFIG_BUG_VM=n > --- > mm/sparse.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/mm/sparse.c b/mm/sparse.c > index 6326cdf36c4f..d13d831f88a5 100644 > --- a/mm/sparse.c > +++ b/mm/sparse.c > @@ -348,7 +348,8 @@ 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); > + VM_BUG_ON(pgdat != &contig_page_data); > + return __pa_symbol(&contig_page_data); > #else > return __pa(pgdat); > #endif > -- > 2.18.0 > -- Sincerely yours, Mike.
