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SubjectRe: [PATCH 1/1] mm/migrate: fix list corruption in migration of non-LRU movable pages
On Wed 04-09-19 02:18:38, sunqiuyang wrote:
> The isolate path of non-lru movable pages:
>
> isolate_migratepages_block
> isolate_movable_page
> trylock_page
> // if PageIsolated, goto out_no_isolated
> a_ops->isolate_page
> __SetPageIsolated
> unlock_page
> list_add(&page->lru, &cc->migratepages)
>
> The migration path:
>
> unmap_and_move
> __unmap_and_move
> lock_page
> move_to_new_page
> a_ops->migratepage
> __ClearPageIsolated
> unlock_page
> /* here, the page could be isolated again by another thread, and added into another cc->migratepages,
> since PG_Isolated has been cleared, and not protected by page_lock */
> list_del(&page->lru)

But the page has been migrated already and not freed yet because there
is still a pin on it. So nobody should be touching it at this stage.
Or do I still miss something?
--
Michal Hocko
SUSE Labs

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