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Date: Fri, 21 Apr 2017 09:59:43 +0530 From: Anshuman Khandual <khandual@...ux.vnet.ibm.com> To: Zi Yan <zi.yan@...t.com>, n-horiguchi@...jp.nec.com, kirill.shutemov@...ux.intel.com, linux-kernel@...r.kernel.org, linux-mm@...ck.org Cc: akpm@...ux-foundation.org, minchan@...nel.org, vbabka@...e.cz, mgorman@...hsingularity.net, mhocko@...nel.org, khandual@...ux.vnet.ibm.com, zi.yan@...rutgers.edu, dnellans@...dia.com Subject: Re: [PATCH v5 03/11] mm: thp: introduce separate TTU flag for thp freezing On 04/21/2017 02:17 AM, Zi Yan wrote: > From: Naoya Horiguchi <n-horiguchi@...jp.nec.com> > > TTU_MIGRATION is used to convert pte into migration entry until thp split > completes. This behavior conflicts with thp migration added later patches, > so let's introduce a new TTU flag specifically for freezing. > > try_to_unmap() is used both for thp split (via freeze_page()) and page > migration (via __unmap_and_move()). In freeze_page(), ttu_flag given for > head page is like below (assuming anonymous thp): > > (TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS | TTU_RMAP_LOCKED | \ > TTU_MIGRATION | TTU_SPLIT_HUGE_PMD) > > and ttu_flag given for tail pages is: > > (TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS | TTU_RMAP_LOCKED | \ > TTU_MIGRATION) > > __unmap_and_move() calls try_to_unmap() with ttu_flag: > > (TTU_MIGRATION | TTU_IGNORE_MLOCK | TTU_IGNORE_ACCESS) > > Now I'm trying to insert a branch for thp migration at the top of > try_to_unmap_one() like below > > static int try_to_unmap_one(struct page *page, struct vm_area_struct *vma, > unsigned long address, void *arg) > { > ... > if (flags & TTU_MIGRATION) { > if (!pvmw.pte && page) { > set_pmd_migration_entry(&pvmw, page); > continue; > } > } > > , so try_to_unmap() for tail pages called by thp split can go into thp > migration code path (which converts *pmd* into migration entry), while > the expectation is to freeze thp (which converts *pte* into migration entry.) > > I detected this failure as a "bad page state" error in a testcase where > split_huge_page() is called from queue_pages_pte_range(). > > Signed-off-by: Naoya Horiguchi <n-horiguchi@...jp.nec.com> It had Kirril's acked-by (https://patchwork.kernel.org/patch/9416221/) last time around. Please include again.
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