* [PATCH v3] mm/sparse: clarify pgdat_to_phys
@ 2021-07-23 12:33 Miles Chen
2021-07-23 12:54 ` David Hildenbrand
2021-07-24 7:47 ` Mike Rapoport
0 siblings, 2 replies; 3+ messages in thread
From: Miles Chen @ 2021-07-23 12:33 UTC (permalink / raw)
To: Andrew Morton, Mike Rapoport, Mark Rutland, David Hildenbrand
Cc: linux-mm, linux-kernel, linux-mediatek, wsd_upstream, Miles Chen
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@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: David Hildenbrand <david@redhat.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.
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
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v3] mm/sparse: clarify pgdat_to_phys
2021-07-23 12:33 [PATCH v3] mm/sparse: clarify pgdat_to_phys Miles Chen
@ 2021-07-23 12:54 ` David Hildenbrand
2021-07-24 7:47 ` Mike Rapoport
1 sibling, 0 replies; 3+ messages in thread
From: David Hildenbrand @ 2021-07-23 12:54 UTC (permalink / raw)
To: Miles Chen, Andrew Morton, Mike Rapoport, Mark Rutland
Cc: linux-mm, linux-kernel, linux-mediatek, wsd_upstream
On 23.07.21 14:33, 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@kernel.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: David Hildenbrand <david@redhat.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.
>
> 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
>
Reviewed-by: David Hildenbrand <david@redhat.com>
--
Thanks,
David / dhildenb
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v3] mm/sparse: clarify pgdat_to_phys
2021-07-23 12:33 [PATCH v3] mm/sparse: clarify pgdat_to_phys Miles Chen
2021-07-23 12:54 ` David Hildenbrand
@ 2021-07-24 7:47 ` Mike Rapoport
1 sibling, 0 replies; 3+ messages in thread
From: Mike Rapoport @ 2021-07-24 7:47 UTC (permalink / raw)
To: Miles Chen
Cc: Andrew Morton, Mark Rutland, David Hildenbrand, linux-mm,
linux-kernel, linux-mediatek, wsd_upstream
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@kernel.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: David Hildenbrand <david@redhat.com>
> Signed-off-by: Miles Chen <miles.chen@mediatek.com>
Acked-by: Mike Rapoport <rppt@linux.ibm.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.
>
> 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.
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