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Sat, 14 Dec 2024 15:58:30 +0800 Message-ID: Date: Sat, 14 Dec 2024 15:58:30 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH -next] ovl: respect underlying filesystem's get_unmapped_area() To: Matthew Wilcox CC: Amir Goldstein , Lorenzo Stoakes , Jinjiang Tu , , , , , , , , References: <20241205143038.3260233-1-tujinjiang@huawei.com> <69b72e3d-b101-4641-9ce5-51346c93a98d@lucifer.local> <041dcc1a-0630-27b9-661b-8c64a3775426@huawei.com> <568698a0-c2f2-45d8-9d8b-e22e942fa422@huawei.com> <3207edaf-826b-4545-9c9d-906bfb4d312e@huawei.com> Content-Language: en-US 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: dggems701-chm.china.huawei.com (10.3.19.178) To dggpemf100008.china.huawei.com (7.185.36.138) X-Rspamd-Queue-Id: 9ABCC140004 X-Rspamd-Server: rspam12 X-Stat-Signature: t11qwtober9zsk3yfuttuiowx6fbkbz7 X-Rspam-User: X-HE-Tag: 1734163098-620441 X-HE-Meta: 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 zib28ATZ 16mHflK8pYUVLhWrMWYmvA6hF1onXiA9tX0cOon6pBT6AEgQ1fQCPHZa7QQTIvglMmV9/G/rLNeqHtpj6WBxx5P9B1asuJOFOVd2bcae5LVtYSypak4l5KT3VcJqxYZH+jPsH/HiVcOeJ4UVIyrnYSZ48jiCsNHdmwPOIViz+nADA7wcpa6WiSfSPVZApYhQvy/8bf+VuWayOWCU+UMY9Ky7iCza23ECZMVkn 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: List-Subscribe: List-Unsubscribe: On 2024/12/13 22:00, Matthew Wilcox wrote: > On Fri, Dec 13, 2024 at 03:49:53PM +0800, Kefeng Wang wrote: >> >> >> On 2024/12/13 12:25, Matthew Wilcox wrote: >>> On Wed, Dec 11, 2024 at 10:43:46AM +0100, Amir Goldstein wrote: >>>> I think this patch is fine as is. >>> >>> This patch is complete crap. The test-case is broken. NAK to all of >>> this. >>> >> Hi Matthew, regardless of the test case, the original issue is the >> ovl don't respect underlying fs' get_unmapped_area(), the lower fs may >> have own rules for vma alignment(own get_unmapped_area callback), >> thp_get_unmapped_area() is one case, what's your option/suggestion about > > No, filesystems don't "have their own rules" for get_unmapped_area. > get_unmapped_area is for device drivers. Commit 74d2fad1334d ("thp, dax: add thp_get_unmapped_area for pmd mappings") to enable PMD mappings as a FSDAX filesystem, and with commit 1854bc6e2420 ("mm/readahead: Align file mappings for non-DAX") to enable THPs for mmapped files too, also other filesystem, eg, tmpfs provide a shmem_get_unmapped_area to decide the mapping address, see commit c01d5b300774 ("shmem: get_unmapped_area align huge page"), that is what I think the filesystem have own rules to get the mapping address, correct me if I misunderstood, thanks.