| Message ID | 20210723070137.23321-1-miles.chen@mediatek.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [RESEND,v2] mm/sparse: clarify pgdat_to_phys | expand |
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?
On Fri, 2021-07-23 at 09:10 +0200, David Hildenbrand wrote: > 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://urldefense.com/v3/__https://lore.kernel.org/linux-arm-kernel/20210615131902.GB47121@C02TD0UTHF1T.local/__;!!CTRNKA9wMg0ARbw!1bJTnH2gJ6QvsBKTXH8xOiKfHF-xq_1dok3cnETD4e4qjryntFm8K0XjtEmkHAxG6g$ > > [2] https://urldefense.com/v3/__https://lore.kernel.org/patchwork/patch/1452903/*1650759__;Iw!!CTRNKA9wMg0ARbw!1bJTnH2gJ6QvsBKTXH8xOiKfHF-xq_1dok3cnETD4e4qjryntFm8K0XjtEmbGXEkVg$ > > > > 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 for your comment, I will use VM_BUG_ON() to check if pgdat == contig_page_data to avoid the runtime check. > >
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"); +#endif /* !CONFIG_NUMA */ return __pa(pgdat); -#endif } #ifdef CONFIG_MEMORY_HOTREMOVE
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(-)