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/[email protected]/
[2] https://lore.kernel.org/patchwork/patch/1452903/#1650759
Cc: Mike Rapoport <[email protected]>
Cc: Mark Rutland <[email protected]>
Signed-off-by: Miles Chen <[email protected]>
---
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");
+#endif /* !CONFIG_NUMA */
return __pa(pgdat);
-#endif
}
#ifdef CONFIG_MEMORY_HOTREMOVE
--
2.18.0
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/[email protected]/
> [2] https://lore.kernel.org/patchwork/patch/1452903/#1650759
>
> Cc: Mike Rapoport <[email protected]>
> Cc: Mark Rutland <[email protected]>
> Signed-off-by: Miles Chen <[email protected]>
>
> ---
>
> 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
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/[email protected]/__;!!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 <[email protected]>
> > Cc: Mark Rutland <[email protected]>
> > Signed-off-by: Miles Chen <[email protected]>
> >
> > ---
> >
> > 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.
>
>