On 2024/1/21 10:00, Matthew Wilcox wrote:
> On Sat, Jan 20, 2024 at 02:57:29PM +0800, Miaohe Lin wrote:
>> diff --git a/mm/memory-failure.c b/mm/memory-failure.c
>> index 636280d04008..20058f7ac3e9 100644
>> --- a/mm/memory-failure.c
>> +++ b/mm/memory-failure.c
>> @@ -1377,8 +1377,13 @@ void ClearPageHWPoisonTakenOff(struct page *page)
>> */
>> static inline bool HWPoisonHandlable(struct page *page, unsigned long flags)
>> {
>> - /* Soft offline could migrate non-LRU movable pages */
>> - if ((flags & MF_SOFT_OFFLINE) && __PageMovable(page))
>> + /*
>> + * Soft offline could migrate non-LRU movable pages.
>> + * Note that page->mapping is overloaded with slab->slab_list or slabs
>> + * fields which might make slab pages appear like non-LRU movable pages.
>> + * So __PageMovable() has to be done after PageSlab() is checked.
>> + */
>> + if ((flags & MF_SOFT_OFFLINE) && !PageSlab(page) && __PageMovable(page))
>> return true;
>>
>> return PageLRU(page) || is_free_buddy_page(page);
>
> I think would make more sense as
>
> + if (PageSlab(page))
> + return false;
Do you mean add PageSlab check above "if ((flags & MF_SOFT_OFFLINE) && __PageMovable(page))" block
so we don't need to add more comment?
>
> ... and then leave the rest alone (including not touching the comment)> .
I have a concern that __PageMovable() seems unreliable now if we access page from random context.
This might introduce some potential problems. For example, offline_pages() might be stumped with
such pages without any progress until signal occurs IIUC:
offline_pages
..
do {
scan_movable_pages
if (__PageMovable(page)) -- It might be slab page here. ret will also be set to 0.
goto found;
do_migrate_range -- Failed to isolate slab page and retry.
} while (!ret) -- retry since ret is 0.
There might be many similar scenes, but I haven't taken them more closely. Maybe these are
just dumb problems...
Thanks.
