2021-01-13 07:38:12

by Dan Williams

Subject: [PATCH v3 2/6] mm: Teach pfn_to_online_page() to consider subsection validity

pfn_section_valid() determines pfn validity on subsection granularity
where pfn_valid() may be limited to coarse section granularity.
Explicitly validate subsections after pfn_valid() succeeds.

Fixes: b13bc35193d9 ("mm/hotplug: invalid PFNs from pfn_to_online_page()")
Cc: Qian Cai <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Oscar Salvador <[email protected]>
Reported-by: David Hildenbrand <[email protected]>
Signed-off-by: Dan Williams <[email protected]>
---
mm/memory_hotplug.c | 24 ++++++++++++++++++++----
1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 55a69d4396e7..9f37f8a68da4 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -308,11 +308,27 @@ static int check_hotplug_memory_addressable(unsigned long pfn,
struct page *pfn_to_online_page(unsigned long pfn)
{
unsigned long nr = pfn_to_section_nr(pfn);
+ struct mem_section *ms;
+
+ if (nr >= NR_MEM_SECTIONS)
+ return NULL;
+
+ ms = __nr_to_section(nr);
+ if (!online_section(ms))
+ return NULL;
+
+ /*
+ * Save some code text when online_section() +
+ * pfn_section_valid() are sufficient.
+ */
+ if (IS_ENABLED(CONFIG_HAVE_ARCH_PFN_VALID))
+ if (!pfn_valid(pfn))
+ return NULL;
+
+ if (!pfn_section_valid(ms, pfn))
+ return NULL;

- if (nr < NR_MEM_SECTIONS && online_section_nr(nr) &&
- pfn_valid_within(pfn))
- return pfn_to_page(pfn);
- return NULL;
+ return pfn_to_page(pfn);
}
EXPORT_SYMBOL_GPL(pfn_to_online_page);

2021-01-13 08:32:27

by David Hildenbrand

Subject: Re: [PATCH v3 2/6] mm: Teach pfn_to_online_page() to consider subsection validity

On 13.01.21 08:35, Dan Williams wrote:
> pfn_section_valid() determines pfn validity on subsection granularity
> where pfn_valid() may be limited to coarse section granularity.
> Explicitly validate subsections after pfn_valid() succeeds.
>
> Fixes: b13bc35193d9 ("mm/hotplug: invalid PFNs from pfn_to_online_page()")
> Cc: Qian Cai <[email protected]>
> Cc: Michal Hocko <[email protected]>
> Cc: Oscar Salvador <[email protected]>
> Reported-by: David Hildenbrand <[email protected]>
> Signed-off-by: Dan Williams <[email protected]>
> ---
> mm/memory_hotplug.c | 24 ++++++++++++++++++++----
> 1 file changed, 20 insertions(+), 4 deletions(-)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 55a69d4396e7..9f37f8a68da4 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -308,11 +308,27 @@ static int check_hotplug_memory_addressable(unsigned long pfn,
> struct page *pfn_to_online_page(unsigned long pfn)
> {
> unsigned long nr = pfn_to_section_nr(pfn);
> + struct mem_section *ms;
> +
> + if (nr >= NR_MEM_SECTIONS)
> + return NULL;
> +
> + ms = __nr_to_section(nr);
> + if (!online_section(ms))
> + return NULL;
> +
> + /*
> + * Save some code text when online_section() +
> + * pfn_section_valid() are sufficient.
> + */
> + if (IS_ENABLED(CONFIG_HAVE_ARCH_PFN_VALID))
> + if (!pfn_valid(pfn))
> + return NULL;

Nit:

if (IS_ENABLED(CONFIG_HAVE_ARCH_PFN_VALID) &&
!pfn_valid(pfn))

Reviewed-by: David Hildenbrand <[email protected]>

--
Thanks,

David / dhildenb

2021-01-13 08:34:22

by Oscar Salvador

Subject: Re: [PATCH v3 2/6] mm: Teach pfn_to_online_page() to consider subsection validity

On Tue, Jan 12, 2021 at 11:35:27PM -0800, Dan Williams wrote:
> pfn_section_valid() determines pfn validity on subsection granularity
> where pfn_valid() may be limited to coarse section granularity.
> Explicitly validate subsections after pfn_valid() succeeds.
>
> Fixes: b13bc35193d9 ("mm/hotplug: invalid PFNs from pfn_to_online_page()")
> Cc: Qian Cai <[email protected]>
> Cc: Michal Hocko <[email protected]>
> Cc: Oscar Salvador <[email protected]>
> Reported-by: David Hildenbrand <[email protected]>
> Signed-off-by: Dan Williams <[email protected]>

Reviewed-by: Oscar Salvador <[email protected]>

> ---
> mm/memory_hotplug.c | 24 ++++++++++++++++++++----
> 1 file changed, 20 insertions(+), 4 deletions(-)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 55a69d4396e7..9f37f8a68da4 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -308,11 +308,27 @@ static int check_hotplug_memory_addressable(unsigned long pfn,
> struct page *pfn_to_online_page(unsigned long pfn)
> {
> unsigned long nr = pfn_to_section_nr(pfn);
> + struct mem_section *ms;
> +
> + if (nr >= NR_MEM_SECTIONS)
> + return NULL;
> +
> + ms = __nr_to_section(nr);
> + if (!online_section(ms))
> + return NULL;
> +
> + /*
> + * Save some code text when online_section() +
> + * pfn_section_valid() are sufficient.
> + */
> + if (IS_ENABLED(CONFIG_HAVE_ARCH_PFN_VALID))
> + if (!pfn_valid(pfn))
> + return NULL;
> +
> + if (!pfn_section_valid(ms, pfn))
> + return NULL;
>
> - if (nr < NR_MEM_SECTIONS && online_section_nr(nr) &&
> - pfn_valid_within(pfn))
> - return pfn_to_page(pfn);
> - return NULL;
> + return pfn_to_page(pfn);
> }
> EXPORT_SYMBOL_GPL(pfn_to_online_page);
>
>

--
Oscar Salvador
SUSE L3

2021-01-13 22:11:38

by Dan Williams

Subject: Re: [PATCH v3 2/6] mm: Teach pfn_to_online_page() to consider subsection validity

On Wed, Jan 13, 2021 at 12:29 AM David Hildenbrand <[email protected]> wrote:
>
> On 13.01.21 08:35, Dan Williams wrote:
> > pfn_section_valid() determines pfn validity on subsection granularity
> > where pfn_valid() may be limited to coarse section granularity.
> > Explicitly validate subsections after pfn_valid() succeeds.
> >
> > Fixes: b13bc35193d9 ("mm/hotplug: invalid PFNs from pfn_to_online_page()")
> > Cc: Qian Cai <[email protected]>
> > Cc: Michal Hocko <[email protected]>
> > Cc: Oscar Salvador <[email protected]>
> > Reported-by: David Hildenbrand <[email protected]>
> > Signed-off-by: Dan Williams <[email protected]>
> > ---
> > mm/memory_hotplug.c | 24 ++++++++++++++++++++----
> > 1 file changed, 20 insertions(+), 4 deletions(-)
> >
> > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> > index 55a69d4396e7..9f37f8a68da4 100644
> > --- a/mm/memory_hotplug.c
> > +++ b/mm/memory_hotplug.c
> > @@ -308,11 +308,27 @@ static int check_hotplug_memory_addressable(unsigned long pfn,
> > struct page *pfn_to_online_page(unsigned long pfn)
> > {
> > unsigned long nr = pfn_to_section_nr(pfn);
> > + struct mem_section *ms;
> > +
> > + if (nr >= NR_MEM_SECTIONS)
> > + return NULL;
> > +
> > + ms = __nr_to_section(nr);
> > + if (!online_section(ms))
> > + return NULL;
> > +
> > + /*
> > + * Save some code text when online_section() +
> > + * pfn_section_valid() are sufficient.
> > + */
> > + if (IS_ENABLED(CONFIG_HAVE_ARCH_PFN_VALID))
> > + if (!pfn_valid(pfn))
> > + return NULL;
>
> Nit:
>
> if (IS_ENABLED(CONFIG_HAVE_ARCH_PFN_VALID) &&
> !pfn_valid(pfn))
>

Ok... I'll do a final resend "To: akpm" after the kbuild robot
finishes chewing on this series.