Messages in this thread Patch in this message | | | Date | Mon, 5 Nov 2018 10:28:51 +0100 | From | Michal Hocko <> | Subject | Re: [PATCH] mm, memory_hotplug: teach has_unmovable_pages about of LRU migrateable pages |
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On Mon 05-11-18 10:14:07, Michal Hocko wrote: > Maybe we can add a retry for movable zone pages.
Or something like this. Ugly as hell, no question about that. I also have to think about this some more to convince myself this will not result in an endless loop under some situations.
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 48ceda313332..342d66eca0f3 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -7779,12 +7779,16 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count, pfn = page_to_pfn(page); for (found = 0, iter = 0; iter < pageblock_nr_pages; iter++) { unsigned long check = pfn + iter; + unsigned long saved_flags; if (!pfn_valid_within(check)) continue; page = pfn_to_page(check); +retry: + saved_flags = READ_ONCE(page->flags); + if (PageReserved(page)) goto unmovable; @@ -7840,6 +7844,13 @@ bool has_unmovable_pages(struct zone *zone, struct page *page, int count, page->mapping->a_ops->migratepage) continue; + /* + * We might race with the allocation of the page so retry + * if flags have changed. + */ + if (saved_flags != READ_ONCE(page->flags)) + goto retry; + /* * If there are RECLAIMABLE pages, we need to check * it. But now, memory offline itself doesn't call -- Michal Hocko SUSE Labs
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