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Mon, 16 Jan 2023 19:31:43 +0800 Message-ID: Date: Mon, 16 Jan 2023 19:31:43 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.5.1 Subject: Re: [PATCH -next 3/7] mm: memory: convert do_cow_fault to use folios Content-Language: en-US To: Matthew Wilcox CC: , , References: <20230112083006.163393-1-wangkefeng.wang@huawei.com> <20230112083006.163393-4-wangkefeng.wang@huawei.com> From: Kefeng Wang In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.243] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To dggpemm500001.china.huawei.com (7.185.36.107) X-CFilter-Loop: Reflected X-Rspam-User: X-Rspamd-Queue-Id: 3970A40009 X-Rspamd-Server: rspam01 X-Stat-Signature: bedk8nme6epncdh8birm8x1mokos9mks X-HE-Tag: 1673868709-323470 X-HE-Meta: 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 2023/1/13 23:37, Matthew Wilcox wrote: > On Thu, Jan 12, 2023 at 04:30:02PM +0800, Kefeng Wang wrote: >> - vmf->cow_page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, vmf->address); >> - if (!vmf->cow_page) >> + cow_folio = vma_alloc_folio(GFP_HIGHUSER_MOVABLE, 0, vma, vmf->address, >> + false); >> + if (!cow_folio) > > I have a patch I've been sitting on that converts vmf->cow_page to be > a folio. I think this series is well and truly wrecked at this point, > so let me go back and dig it out; see if it still makes sense. > For now, as vmf->page and vmf->cow_page used in do_cow_page(), it only supports cow on a page, and after converting, the folio still is 0 order, > I'm a bit unsure about it because maybe we want to allocate > high(ish)-order folios on COW fault, and if we do, then maybe we want > to align them in some way with the virtual addresses, or the other > folios in the VMA. And then we might want to indicate the precise > page for this page fault rather than have this page fault be the > start of a multi-order folio. > This means that if high(ish)-order folios/multi-order folio on cow, it needs additional jobs and precise page for this pagefault, but for order-0, the converting is right but could break/mislead future logical? not very clear about this part, but let's wait for your patches.