memmap should be the address to page struct instead of address to pfn.
As mentioned by David, if system memory and devmem sit within a
section, the mismatch address would lead kdump to dump unexpected
memory.
Since sub-section only works for SPARSEMEM_VMEMMAP, pfn_to_page() is
valid to get the page struct address at this point.
Fixes: ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug")
Signed-off-by: Wei Yang <[email protected]>
CC: Dan Williams <[email protected]>
CC: David Hildenbrand <[email protected]>
CC: Baoquan He <[email protected]>
---
v2:
* adjust comment to mention the mismatch data would affect kdump
---
mm/sparse.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/mm/sparse.c b/mm/sparse.c
index 586d85662978..4862ec2cfbc0 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -887,7 +887,7 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn,
/* Align memmap to section boundary in the subsection case */
if (section_nr_to_pfn(section_nr) != start_pfn)
- memmap = pfn_to_kaddr(section_nr_to_pfn(section_nr));
+ memmap = pfn_to_page(section_nr_to_pfn(section_nr));
sparse_init_one_section(ms, section_nr, memmap, ms->usage, 0);
return 0;
--
2.17.1
On 10.02.20 01:50, Wei Yang wrote:
> memmap should be the address to page struct instead of address to pfn.
>
"mm/sparsemem: fix wrong address in ms->section_mem_map with sub-sections
We want to store the address of the memmap, not the address of the first
pfn.
E.g., we can have both (boot) system memory and devmem residing in a
single section. Once we hot-add the devmem part, the address stored in
ms->section_mem_map would be wrong, and kdump would not be able to
dump the right memory.
"
? See below
> As mentioned by David, if system memory and devmem sit within a
> section, the mismatch address would lead kdump to dump unexpected
> memory.
>
> Since sub-section only works for SPARSEMEM_VMEMMAP, pfn_to_page() is
> valid to get the page struct address at this point.
>
> Fixes: ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug")
> Signed-off-by: Wei Yang <[email protected]>
> CC: Dan Williams <[email protected]>
> CC: David Hildenbrand <[email protected]>
> CC: Baoquan He <[email protected]>
>
> ---
> v2:
> * adjust comment to mention the mismatch data would affect kdump
>
> ---
> mm/sparse.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/sparse.c b/mm/sparse.c
> index 586d85662978..4862ec2cfbc0 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -887,7 +887,7 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn,
>
> /* Align memmap to section boundary in the subsection case */
> if (section_nr_to_pfn(section_nr) != start_pfn)
> - memmap = pfn_to_kaddr(section_nr_to_pfn(section_nr));
> + memmap = pfn_to_page(section_nr_to_pfn(section_nr));
I think this whole code should be reworked.
Callee returns a pointer. Caller: Nah, I know it better.
Just nasty.
Can we do something like this instead:
diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
index 200aef686722..c5091feef29e 100644
--- a/mm/sparse-vmemmap.c
+++ b/mm/sparse-vmemmap.c
@@ -266,5 +266,5 @@ struct page * __meminit
__populate_section_memmap(unsigned long pfn,
if (vmemmap_populate(start, end, nid, altmap))
return NULL;
- return pfn_to_page(pfn);
+ return pfn_to_page(SECTION_ALIGN_DOWN(pfn));
}
diff --git a/mm/sparse.c b/mm/sparse.c
index c184b69460b7..21902d7931e4 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -788,6 +788,10 @@ static void section_deactivate(unsigned long pfn,
unsigned long nr_pages,
depopulate_section_memmap(pfn, nr_pages, altmap);
}
+/*
+ * Returns the memmap of the first pfn of the section (not of
+ * sub-sections).
+ */
static struct page * __meminit section_activate(int nid, unsigned long pfn,
unsigned long nr_pages, struct vmem_altmap *altmap)
{
@@ -882,9 +886,6 @@ int __meminit sparse_add_section(int nid, unsigned
long start_pfn,
set_section_nid(section_nr, nid);
section_mark_present(ms);
- /* Align memmap to section boundary in the subsection case */
- if (section_nr_to_pfn(section_nr) != start_pfn)
- memmap = pfn_to_kaddr(section_nr_to_pfn(section_nr));
sparse_init_one_section(ms, section_nr, memmap, ms->usage, 0);
return 0;
Untested, of course :)
--
Thanks,
David / dhildenb
On 10.02.20 10:00, David Hildenbrand wrote:
> On 10.02.20 01:50, Wei Yang wrote:
>> memmap should be the address to page struct instead of address to pfn.
>>
>
> "mm/sparsemem: fix wrong address in ms->section_mem_map with sub-sections
>
> We want to store the address of the memmap, not the address of the first
> pfn.
>
> E.g., we can have both (boot) system memory and devmem residing in a
> single section. Once we hot-add the devmem part, the address stored in
> ms->section_mem_map would be wrong, and kdump would not be able to
> dump the right memory.
> "
>
> ? See below
>
>> As mentioned by David, if system memory and devmem sit within a
>> section, the mismatch address would lead kdump to dump unexpected
>> memory.
>>
>> Since sub-section only works for SPARSEMEM_VMEMMAP, pfn_to_page() is
>> valid to get the page struct address at this point.
>>
>> Fixes: ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug")
>> Signed-off-by: Wei Yang <[email protected]>
>> CC: Dan Williams <[email protected]>
>> CC: David Hildenbrand <[email protected]>
>> CC: Baoquan He <[email protected]>
>>
>> ---
>> v2:
>> * adjust comment to mention the mismatch data would affect kdump
>>
>> ---
>> mm/sparse.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/mm/sparse.c b/mm/sparse.c
>> index 586d85662978..4862ec2cfbc0 100644
>> --- a/mm/sparse.c
>> +++ b/mm/sparse.c
>> @@ -887,7 +887,7 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn,
>>
>> /* Align memmap to section boundary in the subsection case */
>> if (section_nr_to_pfn(section_nr) != start_pfn)
>> - memmap = pfn_to_kaddr(section_nr_to_pfn(section_nr));
>> + memmap = pfn_to_page(section_nr_to_pfn(section_nr));
>
> I think this whole code should be reworked.
>
> Callee returns a pointer. Caller: Nah, I know it better.
>
> Just nasty.
>
>
> Can we do something like this instead:
>
>
> diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
> index 200aef686722..c5091feef29e 100644
> --- a/mm/sparse-vmemmap.c
> +++ b/mm/sparse-vmemmap.c
> @@ -266,5 +266,5 @@ struct page * __meminit
> __populate_section_memmap(unsigned long pfn,
> if (vmemmap_populate(start, end, nid, altmap))
> return NULL;
>
> - return pfn_to_page(pfn);
> + return pfn_to_page(SECTION_ALIGN_DOWN(pfn));
> }
> diff --git a/mm/sparse.c b/mm/sparse.c
> index c184b69460b7..21902d7931e4 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -788,6 +788,10 @@ static void section_deactivate(unsigned long pfn,
> unsigned long nr_pages,
> depopulate_section_memmap(pfn, nr_pages, altmap);
> }
>
> +/*
> + * Returns the memmap of the first pfn of the section (not of
> + * sub-sections).
> + */
> static struct page * __meminit section_activate(int nid, unsigned long pfn,
> unsigned long nr_pages, struct vmem_altmap *altmap)
> {
> @@ -882,9 +886,6 @@ int __meminit sparse_add_section(int nid, unsigned
> long start_pfn,
> set_section_nid(section_nr, nid);
> section_mark_present(ms);
>
> - /* Align memmap to section boundary in the subsection case */
> - if (section_nr_to_pfn(section_nr) != start_pfn)
> - memmap = pfn_to_kaddr(section_nr_to_pfn(section_nr));
> sparse_init_one_section(ms, section_nr, memmap, ms->usage, 0);
>
> return 0;
>
>
> Untested, of course :)
>
I think the following would be needed as well with Wei's fix:
@@ -876,15 +880,13 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn,
* Poison uninitialized struct pages in order to catch invalid flags
* combinations.
*/
- page_init_poison(pfn_to_page(start_pfn), sizeof(struct page) * nr_pages);
+ page_init_poison(memmap + start_pfn - SECTION_ALIGN_DOWN(start_pfn),
+ sizeof(struct page) * nr_pages);
ms = __nr_to_section(section_nr);
Or we can simply move the poisoning behind sparse_init_one_section().
--
Thanks,
David / dhildenb
On Mon, Feb 10, 2020 at 10:00:47AM +0100, David Hildenbrand wrote:
>On 10.02.20 01:50, Wei Yang wrote:
>> memmap should be the address to page struct instead of address to pfn.
>>
>
>"mm/sparsemem: fix wrong address in ms->section_mem_map with sub-sections
>
>We want to store the address of the memmap, not the address of the first
>pfn.
>
>E.g., we can have both (boot) system memory and devmem residing in a
>single section. Once we hot-add the devmem part, the address stored in
>ms->section_mem_map would be wrong, and kdump would not be able to
>dump the right memory.
>"
>
>? See below
>
>> As mentioned by David, if system memory and devmem sit within a
>> section, the mismatch address would lead kdump to dump unexpected
>> memory.
>>
>> Since sub-section only works for SPARSEMEM_VMEMMAP, pfn_to_page() is
>> valid to get the page struct address at this point.
>>
>> Fixes: ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug")
>> Signed-off-by: Wei Yang <[email protected]>
>> CC: Dan Williams <[email protected]>
>> CC: David Hildenbrand <[email protected]>
>> CC: Baoquan He <[email protected]>
>>
>> ---
>> v2:
>> * adjust comment to mention the mismatch data would affect kdump
>>
>> ---
>> mm/sparse.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/mm/sparse.c b/mm/sparse.c
>> index 586d85662978..4862ec2cfbc0 100644
>> --- a/mm/sparse.c
>> +++ b/mm/sparse.c
>> @@ -887,7 +887,7 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn,
>>
>> /* Align memmap to section boundary in the subsection case */
>> if (section_nr_to_pfn(section_nr) != start_pfn)
>> - memmap = pfn_to_kaddr(section_nr_to_pfn(section_nr));
>> + memmap = pfn_to_page(section_nr_to_pfn(section_nr));
>
>I think this whole code should be reworked.
>
>Callee returns a pointer. Caller: Nah, I know it better.
>
>Just nasty.
>
>
>Can we do something like this instead:
>
>
>diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
>index 200aef686722..c5091feef29e 100644
>--- a/mm/sparse-vmemmap.c
>+++ b/mm/sparse-vmemmap.c
>@@ -266,5 +266,5 @@ struct page * __meminit
>__populate_section_memmap(unsigned long pfn,
> if (vmemmap_populate(start, end, nid, altmap))
> return NULL;
>
>- return pfn_to_page(pfn);
>+ return pfn_to_page(SECTION_ALIGN_DOWN(pfn));
> }
>diff --git a/mm/sparse.c b/mm/sparse.c
>index c184b69460b7..21902d7931e4 100644
>--- a/mm/sparse.c
>+++ b/mm/sparse.c
>@@ -788,6 +788,10 @@ static void section_deactivate(unsigned long pfn,
>unsigned long nr_pages,
> depopulate_section_memmap(pfn, nr_pages, altmap);
> }
>
>+/*
>+ * Returns the memmap of the first pfn of the section (not of
>+ * sub-sections).
>+ */
> static struct page * __meminit section_activate(int nid, unsigned long pfn,
> unsigned long nr_pages, struct vmem_altmap *altmap)
> {
>@@ -882,9 +886,6 @@ int __meminit sparse_add_section(int nid, unsigned
>long start_pfn,
> set_section_nid(section_nr, nid);
> section_mark_present(ms);
>
>- /* Align memmap to section boundary in the subsection case */
>- if (section_nr_to_pfn(section_nr) != start_pfn)
>- memmap = pfn_to_kaddr(section_nr_to_pfn(section_nr));
> sparse_init_one_section(ms, section_nr, memmap, ms->usage, 0);
>
> return 0;
>
>
>Untested, of course :)
I think you get some point. As you mentioned in the following reply, we need
to adjust poisoning after this change.
This looks like a trade off between two options. I don't have a strong
preference.
>
>--
>Thanks,
>
>David / dhildenb
--
Wei Yang
Help you, Help me
On 11.02.20 00:16, Wei Yang wrote:
> On Mon, Feb 10, 2020 at 10:00:47AM +0100, David Hildenbrand wrote:
>> On 10.02.20 01:50, Wei Yang wrote:
>>> memmap should be the address to page struct instead of address to pfn.
>>>
>>
>> "mm/sparsemem: fix wrong address in ms->section_mem_map with sub-sections
>>
>> We want to store the address of the memmap, not the address of the first
>> pfn.
>>
>> E.g., we can have both (boot) system memory and devmem residing in a
>> single section. Once we hot-add the devmem part, the address stored in
>> ms->section_mem_map would be wrong, and kdump would not be able to
>> dump the right memory.
>> "
>>
>> ? See below
>>
>>> As mentioned by David, if system memory and devmem sit within a
>>> section, the mismatch address would lead kdump to dump unexpected
>>> memory.
>>>
>>> Since sub-section only works for SPARSEMEM_VMEMMAP, pfn_to_page() is
>>> valid to get the page struct address at this point.
>>>
>>> Fixes: ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug")
>>> Signed-off-by: Wei Yang <[email protected]>
>>> CC: Dan Williams <[email protected]>
>>> CC: David Hildenbrand <[email protected]>
>>> CC: Baoquan He <[email protected]>
>>>
>>> ---
>>> v2:
>>> * adjust comment to mention the mismatch data would affect kdump
>>>
>>> ---
>>> mm/sparse.c | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/mm/sparse.c b/mm/sparse.c
>>> index 586d85662978..4862ec2cfbc0 100644
>>> --- a/mm/sparse.c
>>> +++ b/mm/sparse.c
>>> @@ -887,7 +887,7 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn,
>>>
>>> /* Align memmap to section boundary in the subsection case */
>>> if (section_nr_to_pfn(section_nr) != start_pfn)
>>> - memmap = pfn_to_kaddr(section_nr_to_pfn(section_nr));
>>> + memmap = pfn_to_page(section_nr_to_pfn(section_nr));
>>
>> I think this whole code should be reworked.
>>
>> Callee returns a pointer. Caller: Nah, I know it better.
>>
>> Just nasty.
>>
>>
>> Can we do something like this instead:
>>
>>
>> diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
>> index 200aef686722..c5091feef29e 100644
>> --- a/mm/sparse-vmemmap.c
>> +++ b/mm/sparse-vmemmap.c
>> @@ -266,5 +266,5 @@ struct page * __meminit
>> __populate_section_memmap(unsigned long pfn,
>> if (vmemmap_populate(start, end, nid, altmap))
>> return NULL;
>>
>> - return pfn_to_page(pfn);
>> + return pfn_to_page(SECTION_ALIGN_DOWN(pfn));
>> }
>> diff --git a/mm/sparse.c b/mm/sparse.c
>> index c184b69460b7..21902d7931e4 100644
>> --- a/mm/sparse.c
>> +++ b/mm/sparse.c
>> @@ -788,6 +788,10 @@ static void section_deactivate(unsigned long pfn,
>> unsigned long nr_pages,
>> depopulate_section_memmap(pfn, nr_pages, altmap);
>> }
>>
>> +/*
>> + * Returns the memmap of the first pfn of the section (not of
>> + * sub-sections).
>> + */
>> static struct page * __meminit section_activate(int nid, unsigned long pfn,
>> unsigned long nr_pages, struct vmem_altmap *altmap)
>> {
>> @@ -882,9 +886,6 @@ int __meminit sparse_add_section(int nid, unsigned
>> long start_pfn,
>> set_section_nid(section_nr, nid);
>> section_mark_present(ms);
>>
>> - /* Align memmap to section boundary in the subsection case */
>> - if (section_nr_to_pfn(section_nr) != start_pfn)
>> - memmap = pfn_to_kaddr(section_nr_to_pfn(section_nr));
>> sparse_init_one_section(ms, section_nr, memmap, ms->usage, 0);
>>
>> return 0;
>>
>>
>> Untested, of course :)
>
> I think you get some point. As you mentioned in the following reply, we need
> to adjust poisoning after this change.
We can just poison after setting up the section (IOW, move it further down).
>
> This looks like a trade off between two options. I don't have a strong
> preference.
I clearly prefer if *section*_activate() returns the memmap of the
section. This code is just confusing. But I can send a cleanup on top if
you want to keep it like that for now.
--
Thanks,
David / dhildenb
On Tue, Feb 11, 2020 at 03:01:35PM +0100, David Hildenbrand wrote:
>On 11.02.20 00:16, Wei Yang wrote:
>> On Mon, Feb 10, 2020 at 10:00:47AM +0100, David Hildenbrand wrote:
>>> On 10.02.20 01:50, Wei Yang wrote:
>>>> memmap should be the address to page struct instead of address to pfn.
>>>>
>>>
>>> "mm/sparsemem: fix wrong address in ms->section_mem_map with sub-sections
>>>
>>> We want to store the address of the memmap, not the address of the first
>>> pfn.
>>>
>>> E.g., we can have both (boot) system memory and devmem residing in a
>>> single section. Once we hot-add the devmem part, the address stored in
>>> ms->section_mem_map would be wrong, and kdump would not be able to
>>> dump the right memory.
>>> "
>>>
>>> ? See below
>>>
>>>> As mentioned by David, if system memory and devmem sit within a
>>>> section, the mismatch address would lead kdump to dump unexpected
>>>> memory.
>>>>
>>>> Since sub-section only works for SPARSEMEM_VMEMMAP, pfn_to_page() is
>>>> valid to get the page struct address at this point.
>>>>
>>>> Fixes: ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug")
>>>> Signed-off-by: Wei Yang <[email protected]>
>>>> CC: Dan Williams <[email protected]>
>>>> CC: David Hildenbrand <[email protected]>
>>>> CC: Baoquan He <[email protected]>
>>>>
>>>> ---
>>>> v2:
>>>> * adjust comment to mention the mismatch data would affect kdump
>>>>
>>>> ---
>>>> mm/sparse.c | 2 +-
>>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/mm/sparse.c b/mm/sparse.c
>>>> index 586d85662978..4862ec2cfbc0 100644
>>>> --- a/mm/sparse.c
>>>> +++ b/mm/sparse.c
>>>> @@ -887,7 +887,7 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn,
>>>>
>>>> /* Align memmap to section boundary in the subsection case */
>>>> if (section_nr_to_pfn(section_nr) != start_pfn)
>>>> - memmap = pfn_to_kaddr(section_nr_to_pfn(section_nr));
>>>> + memmap = pfn_to_page(section_nr_to_pfn(section_nr));
>>>
>>> I think this whole code should be reworked.
>>>
>>> Callee returns a pointer. Caller: Nah, I know it better.
>>>
>>> Just nasty.
>>>
>>>
>>> Can we do something like this instead:
>>>
>>>
>>> diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
>>> index 200aef686722..c5091feef29e 100644
>>> --- a/mm/sparse-vmemmap.c
>>> +++ b/mm/sparse-vmemmap.c
>>> @@ -266,5 +266,5 @@ struct page * __meminit
>>> __populate_section_memmap(unsigned long pfn,
>>> if (vmemmap_populate(start, end, nid, altmap))
>>> return NULL;
>>>
>>> - return pfn_to_page(pfn);
>>> + return pfn_to_page(SECTION_ALIGN_DOWN(pfn));
>>> }
>>> diff --git a/mm/sparse.c b/mm/sparse.c
>>> index c184b69460b7..21902d7931e4 100644
>>> --- a/mm/sparse.c
>>> +++ b/mm/sparse.c
>>> @@ -788,6 +788,10 @@ static void section_deactivate(unsigned long pfn,
>>> unsigned long nr_pages,
>>> depopulate_section_memmap(pfn, nr_pages, altmap);
>>> }
>>>
>>> +/*
>>> + * Returns the memmap of the first pfn of the section (not of
>>> + * sub-sections).
>>> + */
>>> static struct page * __meminit section_activate(int nid, unsigned long pfn,
>>> unsigned long nr_pages, struct vmem_altmap *altmap)
>>> {
>>> @@ -882,9 +886,6 @@ int __meminit sparse_add_section(int nid, unsigned
>>> long start_pfn,
>>> set_section_nid(section_nr, nid);
>>> section_mark_present(ms);
>>>
>>> - /* Align memmap to section boundary in the subsection case */
>>> - if (section_nr_to_pfn(section_nr) != start_pfn)
>>> - memmap = pfn_to_kaddr(section_nr_to_pfn(section_nr));
>>> sparse_init_one_section(ms, section_nr, memmap, ms->usage, 0);
>>>
>>> return 0;
>>>
>>>
>>> Untested, of course :)
>>
>> I think you get some point. As you mentioned in the following reply, we need
>> to adjust poisoning after this change.
>
>We can just poison after setting up the section (IOW, move it further down).
>
>>
>> This looks like a trade off between two options. I don't have a strong
>> preference.
>
>I clearly prefer if *section*_activate() returns the memmap of the
>section. This code is just confusing. But I can send a cleanup on top if
>you want to keep it like that for now.
>
Sure, a cleanup patch may help audience get more understanding about the
change.
>
>--
>Thanks,
>
>David / dhildenb
--
Wei Yang
Help you, Help me
On 12.02.20 03:28, Wei Yang wrote:
> On Tue, Feb 11, 2020 at 03:01:35PM +0100, David Hildenbrand wrote:
>> On 11.02.20 00:16, Wei Yang wrote:
>>> On Mon, Feb 10, 2020 at 10:00:47AM +0100, David Hildenbrand wrote:
>>>> On 10.02.20 01:50, Wei Yang wrote:
>>>>> memmap should be the address to page struct instead of address to pfn.
>>>>>
>>>>
>>>> "mm/sparsemem: fix wrong address in ms->section_mem_map with sub-sections
>>>>
>>>> We want to store the address of the memmap, not the address of the first
>>>> pfn.
>>>>
>>>> E.g., we can have both (boot) system memory and devmem residing in a
>>>> single section. Once we hot-add the devmem part, the address stored in
>>>> ms->section_mem_map would be wrong, and kdump would not be able to
>>>> dump the right memory.
>>>> "
>>>>
>>>> ? See below
>>>>
>>>>> As mentioned by David, if system memory and devmem sit within a
>>>>> section, the mismatch address would lead kdump to dump unexpected
>>>>> memory.
>>>>>
>>>>> Since sub-section only works for SPARSEMEM_VMEMMAP, pfn_to_page() is
>>>>> valid to get the page struct address at this point.
>>>>>
>>>>> Fixes: ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug")
>>>>> Signed-off-by: Wei Yang <[email protected]>
>>>>> CC: Dan Williams <[email protected]>
>>>>> CC: David Hildenbrand <[email protected]>
>>>>> CC: Baoquan He <[email protected]>
>>>>>
>>>>> ---
>>>>> v2:
>>>>> * adjust comment to mention the mismatch data would affect kdump
>>>>>
>>>>> ---
>>>>> mm/sparse.c | 2 +-
>>>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/mm/sparse.c b/mm/sparse.c
>>>>> index 586d85662978..4862ec2cfbc0 100644
>>>>> --- a/mm/sparse.c
>>>>> +++ b/mm/sparse.c
>>>>> @@ -887,7 +887,7 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn,
>>>>>
>>>>> /* Align memmap to section boundary in the subsection case */
>>>>> if (section_nr_to_pfn(section_nr) != start_pfn)
>>>>> - memmap = pfn_to_kaddr(section_nr_to_pfn(section_nr));
>>>>> + memmap = pfn_to_page(section_nr_to_pfn(section_nr));
>>>>
>>>> I think this whole code should be reworked.
>>>>
>>>> Callee returns a pointer. Caller: Nah, I know it better.
>>>>
>>>> Just nasty.
>>>>
>>>>
>>>> Can we do something like this instead:
>>>>
>>>>
>>>> diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c
>>>> index 200aef686722..c5091feef29e 100644
>>>> --- a/mm/sparse-vmemmap.c
>>>> +++ b/mm/sparse-vmemmap.c
>>>> @@ -266,5 +266,5 @@ struct page * __meminit
>>>> __populate_section_memmap(unsigned long pfn,
>>>> if (vmemmap_populate(start, end, nid, altmap))
>>>> return NULL;
>>>>
>>>> - return pfn_to_page(pfn);
>>>> + return pfn_to_page(SECTION_ALIGN_DOWN(pfn));
>>>> }
>>>> diff --git a/mm/sparse.c b/mm/sparse.c
>>>> index c184b69460b7..21902d7931e4 100644
>>>> --- a/mm/sparse.c
>>>> +++ b/mm/sparse.c
>>>> @@ -788,6 +788,10 @@ static void section_deactivate(unsigned long pfn,
>>>> unsigned long nr_pages,
>>>> depopulate_section_memmap(pfn, nr_pages, altmap);
>>>> }
>>>>
>>>> +/*
>>>> + * Returns the memmap of the first pfn of the section (not of
>>>> + * sub-sections).
>>>> + */
>>>> static struct page * __meminit section_activate(int nid, unsigned long pfn,
>>>> unsigned long nr_pages, struct vmem_altmap *altmap)
>>>> {
>>>> @@ -882,9 +886,6 @@ int __meminit sparse_add_section(int nid, unsigned
>>>> long start_pfn,
>>>> set_section_nid(section_nr, nid);
>>>> section_mark_present(ms);
>>>>
>>>> - /* Align memmap to section boundary in the subsection case */
>>>> - if (section_nr_to_pfn(section_nr) != start_pfn)
>>>> - memmap = pfn_to_kaddr(section_nr_to_pfn(section_nr));
>>>> sparse_init_one_section(ms, section_nr, memmap, ms->usage, 0);
>>>>
>>>> return 0;
>>>>
>>>>
>>>> Untested, of course :)
>>>
>>> I think you get some point. As you mentioned in the following reply, we need
>>> to adjust poisoning after this change.
>>
>> We can just poison after setting up the section (IOW, move it further down).
>>
>>>
>>> This looks like a trade off between two options. I don't have a strong
>>> preference.
>>
>> I clearly prefer if *section*_activate() returns the memmap of the
>> section. This code is just confusing. But I can send a cleanup on top if
>> you want to keep it like that for now.
>>
>
> Sure, a cleanup patch may help audience get more understanding about the
> change.
>
For this simple fix for now.
Acked-by: David Hildenbrand <[email protected]>
Will send a cleanup in case I don't forget :)
--
Thanks,
David / dhildenb