* [PATCH] mm/page_isolation: fix potential missing call to unset_migratetype_isolate()
@ 2021-09-04 9:20 Miaohe Lin
2021-09-06 9:27 ` David Hildenbrand
0 siblings, 1 reply; 5+ messages in thread
From: Miaohe Lin @ 2021-09-04 9:20 UTC (permalink / raw)
To: akpm; +Cc: mhocko, vbabka, linux-mm, linux-kernel, linmiaohe
In start_isolate_page_range() undo path, pfn_to_online_page() just checks
the first pfn in a pageblock while __first_valid_page() will traverse the
pageblock until the first online pfn is found. So we may miss the call to
unset_migratetype_isolate() in undo path and pages will remain isolated
unexpectedly. Fix this by calling undo_isolate_page_range() and this will
also help to remove some duplicated codes.
Fixes: 2ce13640b3f4 ("mm: __first_valid_page skip over offline pages")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
---
mm/page_isolation.c | 9 +--------
1 file changed, 1 insertion(+), 8 deletions(-)
diff --git a/mm/page_isolation.c b/mm/page_isolation.c
index 471e3a13b541..9bb562d5d194 100644
--- a/mm/page_isolation.c
+++ b/mm/page_isolation.c
@@ -202,14 +202,7 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
}
return 0;
undo:
- for (pfn = start_pfn;
- pfn < undo_pfn;
- pfn += pageblock_nr_pages) {
- struct page *page = pfn_to_online_page(pfn);
- if (!page)
- continue;
- unset_migratetype_isolate(page, migratetype);
- }
+ undo_isolate_page_range(start_pfn, undo_pfn, migratetype);
return -EBUSY;
}
--
2.23.0
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] mm/page_isolation: fix potential missing call to unset_migratetype_isolate()
2021-09-04 9:20 [PATCH] mm/page_isolation: fix potential missing call to unset_migratetype_isolate() Miaohe Lin
@ 2021-09-06 9:27 ` David Hildenbrand
2021-09-06 9:38 ` Miaohe Lin
0 siblings, 1 reply; 5+ messages in thread
From: David Hildenbrand @ 2021-09-06 9:27 UTC (permalink / raw)
To: Miaohe Lin, akpm; +Cc: mhocko, vbabka, linux-mm, linux-kernel
On 04.09.21 11:20, Miaohe Lin wrote:
> In start_isolate_page_range() undo path, pfn_to_online_page() just checks
> the first pfn in a pageblock while __first_valid_page() will traverse the
> pageblock until the first online pfn is found. So we may miss the call to
> unset_migratetype_isolate() in undo path and pages will remain isolated
> unexpectedly. Fix this by calling undo_isolate_page_range() and this will
> also help to remove some duplicated codes.
>
> Fixes: 2ce13640b3f4 ("mm: __first_valid_page skip over offline pages")
While that is true, we shouldn't ever trigger, neither via cma,
virtio-mem nor memory offlining, because essentially all operate on
MAX_ORDER -1 -aligned ranges without memory holes.
> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
> ---
> mm/page_isolation.c | 9 +--------
> 1 file changed, 1 insertion(+), 8 deletions(-)
>
> diff --git a/mm/page_isolation.c b/mm/page_isolation.c
> index 471e3a13b541..9bb562d5d194 100644
> --- a/mm/page_isolation.c
> +++ b/mm/page_isolation.c
> @@ -202,14 +202,7 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
> }
> return 0;
> undo:
> - for (pfn = start_pfn;
> - pfn < undo_pfn;
> - pfn += pageblock_nr_pages) {
> - struct page *page = pfn_to_online_page(pfn);
> - if (!page)
> - continue;
> - unset_migratetype_isolate(page, migratetype);
> - }
> + undo_isolate_page_range(start_pfn, undo_pfn, migratetype);
>
It'd be even cleaner to drop the label completely and call it from the
single callsite. We can even avoid undo_pfn ...
if (page && set_migratetype_isolate(page, migratetype, flags)) {
undo_isolate_page_range(start_pfn, pfn, migratetype);
return -EBUSY;
}
If pfn == start_pfn, undo_isolate_page_range() will simply do nothing.
> return -EBUSY;
> }
>
--
Thanks,
David / dhildenb
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] mm/page_isolation: fix potential missing call to unset_migratetype_isolate()
2021-09-06 9:27 ` David Hildenbrand
@ 2021-09-06 9:38 ` Miaohe Lin
2021-09-06 9:46 ` David Hildenbrand
0 siblings, 1 reply; 5+ messages in thread
From: Miaohe Lin @ 2021-09-06 9:38 UTC (permalink / raw)
To: David Hildenbrand, akpm; +Cc: mhocko, vbabka, linux-mm, linux-kernel
On 2021/9/6 17:27, David Hildenbrand wrote:
> On 04.09.21 11:20, Miaohe Lin wrote:
>> In start_isolate_page_range() undo path, pfn_to_online_page() just checks
>> the first pfn in a pageblock while __first_valid_page() will traverse the
>> pageblock until the first online pfn is found. So we may miss the call to
>> unset_migratetype_isolate() in undo path and pages will remain isolated
>> unexpectedly. Fix this by calling undo_isolate_page_range() and this will
>> also help to remove some duplicated codes.
>>
>> Fixes: 2ce13640b3f4 ("mm: __first_valid_page skip over offline pages")
>
> While that is true, we shouldn't ever trigger, neither via cma, virtio-mem nor memory offlining, because essentially all operate on MAX_ORDER -1 -aligned ranges without memory holes.
I think this should never trigger too. It's a theoretical issue. So is the Fixes tag necessary ?
>
>> Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
>> ---
>> mm/page_isolation.c | 9 +--------
>> 1 file changed, 1 insertion(+), 8 deletions(-)
>>
>> diff --git a/mm/page_isolation.c b/mm/page_isolation.c
>> index 471e3a13b541..9bb562d5d194 100644
>> --- a/mm/page_isolation.c
>> +++ b/mm/page_isolation.c
>> @@ -202,14 +202,7 @@ int start_isolate_page_range(unsigned long start_pfn, unsigned long end_pfn,
>> }
>> return 0;
>> undo:
>> - for (pfn = start_pfn;
>> - pfn < undo_pfn;
>> - pfn += pageblock_nr_pages) {
>> - struct page *page = pfn_to_online_page(pfn);
>> - if (!page)
>> - continue;
>> - unset_migratetype_isolate(page, migratetype);
>> - }
>> + undo_isolate_page_range(start_pfn, undo_pfn, migratetype);
>>
>
> It'd be even cleaner to drop the label completely and call it from the single callsite. We can even avoid undo_pfn ...
>
> if (page && set_migratetype_isolate(page, migratetype, flags)) {
> undo_isolate_page_range(start_pfn, pfn, migratetype);
> return -EBUSY;
> }
>
Looks much better. Will do it later. Many thanks. :)
> If pfn == start_pfn, undo_isolate_page_range() will simply do nothing.
>
>> return -EBUSY;
>> }
>>
>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] mm/page_isolation: fix potential missing call to unset_migratetype_isolate()
2021-09-06 9:38 ` Miaohe Lin
@ 2021-09-06 9:46 ` David Hildenbrand
2021-09-06 11:42 ` Miaohe Lin
0 siblings, 1 reply; 5+ messages in thread
From: David Hildenbrand @ 2021-09-06 9:46 UTC (permalink / raw)
To: Miaohe Lin, akpm; +Cc: mhocko, vbabka, linux-mm, linux-kernel
On 06.09.21 11:38, Miaohe Lin wrote:
> On 2021/9/6 17:27, David Hildenbrand wrote:
>> On 04.09.21 11:20, Miaohe Lin wrote:
>>> In start_isolate_page_range() undo path, pfn_to_online_page() just checks
>>> the first pfn in a pageblock while __first_valid_page() will traverse the
>>> pageblock until the first online pfn is found. So we may miss the call to
>>> unset_migratetype_isolate() in undo path and pages will remain isolated
>>> unexpectedly. Fix this by calling undo_isolate_page_range() and this will
>>> also help to remove some duplicated codes.
>>>
>>> Fixes: 2ce13640b3f4 ("mm: __first_valid_page skip over offline pages")
>>
>> While that is true, we shouldn't ever trigger, neither via cma, virtio-mem nor memory offlining, because essentially all operate on MAX_ORDER -1 -aligned ranges without memory holes.
>
> I think this should never trigger too. It's a theoretical issue. So is the Fixes tag necessary ?
>
I think it's one of these "let's add Fixes: but no need for Cc: stable".
BUT in older kernels we could have triggered this via memory offlining
eventually ... before c5e79ef561b0 ("mm/memory_hotplug.c: don't allow to
online/offline memory blocks with holes") ... so maybe even a Cc: stable?
--
Thanks,
David / dhildenb
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] mm/page_isolation: fix potential missing call to unset_migratetype_isolate()
2021-09-06 9:46 ` David Hildenbrand
@ 2021-09-06 11:42 ` Miaohe Lin
0 siblings, 0 replies; 5+ messages in thread
From: Miaohe Lin @ 2021-09-06 11:42 UTC (permalink / raw)
To: David Hildenbrand, akpm; +Cc: mhocko, vbabka, linux-mm, linux-kernel
On 2021/9/6 17:46, David Hildenbrand wrote:
> On 06.09.21 11:38, Miaohe Lin wrote:
>> On 2021/9/6 17:27, David Hildenbrand wrote:
>>> On 04.09.21 11:20, Miaohe Lin wrote:
>>>> In start_isolate_page_range() undo path, pfn_to_online_page() just checks
>>>> the first pfn in a pageblock while __first_valid_page() will traverse the
>>>> pageblock until the first online pfn is found. So we may miss the call to
>>>> unset_migratetype_isolate() in undo path and pages will remain isolated
>>>> unexpectedly. Fix this by calling undo_isolate_page_range() and this will
>>>> also help to remove some duplicated codes.
>>>>
>>>> Fixes: 2ce13640b3f4 ("mm: __first_valid_page skip over offline pages")
>>>
>>> While that is true, we shouldn't ever trigger, neither via cma, virtio-mem nor memory offlining, because essentially all operate on MAX_ORDER -1 -aligned ranges without memory holes.
>>
>> I think this should never trigger too. It's a theoretical issue. So is the Fixes tag necessary ?
>>
>
> I think it's one of these "let's add Fixes: but no need for Cc: stable".
>
> BUT in older kernels we could have triggered this via memory offlining eventually ... before c5e79ef561b0 ("mm/memory_hotplug.c: don't allow to online/offline memory blocks with holes") ... so maybe even a Cc: stable?
Looks like it could happen in older kernels. Maybe a Cc: stable is necessary.
Many thanks.
>
^ permalink raw reply [flat|nested] 5+ messages in thread
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2021-09-04 9:20 [PATCH] mm/page_isolation: fix potential missing call to unset_migratetype_isolate() Miaohe Lin
2021-09-06 9:27 ` David Hildenbrand
2021-09-06 9:38 ` Miaohe Lin
2021-09-06 9:46 ` David Hildenbrand
2021-09-06 11:42 ` Miaohe Lin
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