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Received: from willy by casper.infradead.org with local (Exim 4.98 #2 (Red Hat Linux)) id 1tL4VU-0000000AkAR-00ZY; Tue, 10 Dec 2024 17:58:48 +0000 Date: Tue, 10 Dec 2024 17:58:47 +0000 From: Matthew Wilcox To: Jinjiang Tu Cc: miklos@szeredi.hu, amir73il@gmail.com, akpm@linux-foundation.org, lorenzo.stoakes@oracle.com, vbabka@suse.cz, jannh@google.com, linux-mm@kvack.org, linux-unionfs@vger.kernel.org, wangkefeng.wang@huawei.com, sunnanyong@huawei.com, yi.zhang@huawei.com Subject: Re: [PATCH -next] ovl: respect underlying filesystem's get_unmapped_area() Message-ID: References: <20241205143038.3260233-1-tujinjiang@huawei.com> <4a8e2901-12b3-b700-383c-3193adc0ed60@huawei.com> <30caaca6-df23-c1cc-1980-88b83600807f@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <30caaca6-df23-c1cc-1980-88b83600807f@huawei.com> X-Rspamd-Queue-Id: 76DD04000E X-Stat-Signature: sk4r87i6niytoydbi7ud65ghsuu4kwei X-Rspam-User: X-Rspamd-Server: rspam11 X-HE-Tag: 1733853524-216361 X-HE-Meta: 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 kWX9zS/i ehsPW+rbugGrQQryMG9A2+PHl+NhhS4J6iOZXsOeC38lV5lPnuOnSX4YZqL3k01Z1pXswnyiYzf6P/NgpS9hE0loRfZqU4bYxVS3PTmds6SpZ3Je+Z2ccZk3BrzOwB88ABCCCu9jN1eYTkx2kLhmRJ1d7vbq3uFhiw2Z4h4PYu5otw+0q7q3vQdJ53cxLG0ssq6yWwK7rTgfNEyUOUCx0reYexiYLt9UbdJeYXp0hI0K/PXuVWlGQA4+amql+eoZI4DhGqw5CrO5iiu6+KEc+FXhMEqjOhlHC57dRZSfOXsOHP9A= 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 Tue, Dec 10, 2024 at 03:13:21PM +0800, Jinjiang Tu wrote: > 在 2024/12/9 21:33, Matthew Wilcox 写道: > > On Mon, Dec 09, 2024 at 02:43:08PM +0800, Jinjiang Tu wrote: > > > 在 2024/12/6 21:58, Matthew Wilcox 写道: > > > > On Thu, Dec 05, 2024 at 10:30:38PM +0800, Jinjiang Tu wrote: > > > > > During our tests in containers, there is a read-only file (i.e., shared > > > > Show your test. > > > I mmap an overlayfs file with PROT_READ, and call madvise(MADV_COLLAPSE), the code > > > is as follows: > > > > > > fd = open(path, O_RDONLY); > > > addr = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0); > > > ret = madvise(addr, size, MADV_COLLAPSE); > > > > > > The addr isn't THP-aligned and ret is -1, errno is EINVAL. > > Then your test is buggy. > > > > * Check alignment for file vma and size for both file and anon vma by > > * filtering out the unsuitable orders. > > > > You didn't align your mmap, so it's expected to fail. > > When mmap an ext4 file, since ext4_file_operations defines ".get_unmapped_area = thp_get_unmapped_area", it calls thp_get_unmapped_area() in __get_unmapped_area to > mmap at a THP-aligned address. > > For overlayfs file, it's underlying filesystem may be ext4, which supports large folio. For this situation, should we mmap at a THP-aligned address too, to map > THP? Actually, ext4 doesn't support large folios. thp_get_unmapped_area() was added for DAX in 2016 (dbe6ec815641).