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SubjectRe: [RFC][-mm PATCH 6/8] Memory controller add per container LRU and reclaim (v3)
YAMAMOTO Takashi wrote:
> hi,
>
>> +unsigned long mem_container_isolate_pages(unsigned long nr_to_scan,
>> + struct list_head *dst,
>> + unsigned long *scanned, int order,
>> + int mode, struct zone *z,
>> + struct mem_container *mem_cont,
>> + int active)
>> +{
>> + unsigned long nr_taken = 0;
>> + struct page *page;
>> + unsigned long scan;
>> + LIST_HEAD(mp_list);
>> + struct list_head *src;
>> + struct meta_page *mp;
>> +
>> + if (active)
>> + src = &mem_cont->active_list;
>> + else
>> + src = &mem_cont->inactive_list;
>> +
>> + for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) {
>> + mp = list_entry(src->prev, struct meta_page, lru);
>> + page = mp->page;
>> +
>
> - is it safe to pick the lists without mem_cont->lru_lock held?
>
> - what prevents mem_container_uncharge from freeing this meta_page
> behind us?
>
> YAMAMOTO Takashi

Hi, YAMAMOTO,

We do take the lru_lock before deleting the page from the list
and in mem_container_move_lists(). But, I guess like you point
out page = mp->page might not be a safe operation. I'll fix
the problem in the next release.

Thanks for the review,
--
Balbir Singh
Linux Technology Center
IBM, ISTL
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