On 2021/9/13 20:15, David Hildenbrand wrote:
> On 13.09.21 13:50, Miaohe Lin wrote:
>> If __isolate_free_page() failed, due to zone watermark check, the page is
>> still on the free list. But this page will be put back to free list again
>> via __putback_isolated_page() now. This may trigger page->flags checks in
>> __free_one_page() if PageReported is set. Or we will corrupt the free list
>> because list_add() will be called for pages already on another list.
>>
>> Fixes: 3c605096d315 ("mm/page_alloc: restrict max order of merging on isolated pageblock")
>> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
>> ---
>> v1->v2:
>> Add VM_WARN_ON to catch unexpected isolating failure.
>> ---
>> mm/page_isolation.c | 9 +++++++--
>> 1 file changed, 7 insertions(+), 2 deletions(-)
>>
>> diff --git a/mm/page_isolation.c b/mm/page_isolation.c
>> index f93cc63d8fa1..f67c4c70f17f 100644
>> --- a/mm/page_isolation.c
>> +++ b/mm/page_isolation.c
>> @@ -94,8 +94,13 @@ static void unset_migratetype_isolate(struct page *page, unsigned migratetype)
>> buddy = page + (buddy_pfn - pfn);
>> if (!is_migrate_isolate_page(buddy)) {
>> - __isolate_free_page(page, order);
>> - isolated_page = true;
>> + isolated_page = !!__isolate_free_page(page, order);
>> + /*
>> + * Isolating a free page in an isolated pageblock
>> + * is expected to always work as watermarks don't
>> + * apply here.
>> + */
>> + VM_WARN_ON(!isolated_page);
>
>
> Didn't we discuss that this can never happen?
>
> In that case, the patch description+subject needs updating and the "Fixes" line would be wrong.
>
I thought this might need a Fixes tag... Will change all of these. Many thanks.
>> }
>> }
>> }
>>
>
>
