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Date: Fri, 2 Dec 2016 11:04:11 +0100 From: Michal Hocko <mhocko@...nel.org> To: Hillf Danton <hillf.zj@...baba-inc.com> Cc: 'Vlastimil Babka' <vbabka@...e.cz>, 'Mel Gorman' <mgorman@...hsingularity.net>, 'Andrew Morton' <akpm@...ux-foundation.org>, 'Christoph Lameter' <cl@...ux.com>, 'Johannes Weiner' <hannes@...xchg.org>, 'Jesper Dangaard Brouer' <brouer@...hat.com>, 'Linux-MM' <linux-mm@...ck.org>, 'Linux-Kernel' <linux-kernel@...r.kernel.org> Subject: Re: [PATCH 1/2] mm, page_alloc: Keep pcp count and list contents in sync if struct page is corrupted On Fri 02-12-16 17:30:07, Hillf Danton wrote: [...] > > >> @@ -2217,13 +2217,14 @@ static int rmqueue_bulk(struct zone *zone, unsigned int order, > > >> else > > >> list_add_tail(&page->lru, list); > > >> list = &page->lru; > > >> + alloced++; > > >> if (is_migrate_cma(get_pcppage_migratetype(page))) > > >> __mod_zone_page_state(zone, NR_FREE_CMA_PAGES, > > >> -(1 << order)); > > >> } > > >> __mod_zone_page_state(zone, NR_FREE_PAGES, -(i << order)); > > > > > > Now i is a pure index, yes? > > > > No, even if a page fails the check_pcp_refill() check and is not > > "allocated", it is also no longer a free page, so it's correct to > > subtract it from NR_FREE_PAGES. > > > Yes, we can allocate free page next time. No we cannot. The page is gone from the free list. We have effectively leaked it. -- Michal Hocko SUSE Labs
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