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Date: Thu, 18 Feb 2016 14:19:09 +0200 From: "Kirill A. Shutemov" <kirill@...temov.name> To: Dave Hansen <dave.hansen@...el.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, Hugh Dickins <hughd@...gle.com>, Andrea Arcangeli <aarcange@...hat.com>, Andrew Morton <akpm@...ux-foundation.org>, Vlastimil Babka <vbabka@...e.cz>, Christoph Lameter <cl@...two.org>, Naoya Horiguchi <n-horiguchi@...jp.nec.com>, Jerome Marchand <jmarchan@...hat.com>, Yang Shi <yang.shi@...aro.org>, Sasha Levin <sasha.levin@...cle.com>, linux-kernel@...r.kernel.org, linux-mm@...ck.org Subject: Re: [PATCHv2 13/28] thp: support file pages in zap_huge_pmd() On Tue, Feb 16, 2016 at 07:31:58AM -0800, Dave Hansen wrote: > On 02/16/2016 02:00 AM, Kirill A. Shutemov wrote: > > On Fri, Feb 12, 2016 at 10:33:37AM -0800, Dave Hansen wrote: > >> On 02/11/2016 06:21 AM, Kirill A. Shutemov wrote: > >>> For file pages we don't deposit page table on mapping: no need to > >>> withdraw it. > >> > >> I thought the deposit thing was to guarantee we could always do a PMD > >> split. It still seems like if you wanted to split a huge-tmpfs page, > >> you'd need to first split the PMD which might need the deposited one. > >> > >> Why not? > > > > For file thp, split_huge_pmd() is implemented by clearing out the pmd: we > > can setup and fill pte table later. Therefore no need to deposit page > > table -- we would not use it. DAX does the same. > > Ahh... Do we just never split in any fault contexts, or do we just > retry the fault? In fault contexts we would just continue fault handling as if we had pmd_none(). -- Kirill A. Shutemov
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