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Mon, 31 Jan 2022 18:24:02 -0800 (PST) MIME-Version: 1.0 References: <20220131230255.789059-1-mfo@canonical.com> <20220131154340.e65ebe932d8933bc68c4ddf4@linux-foundation.org> In-Reply-To: <20220131154340.e65ebe932d8933bc68c4ddf4@linux-foundation.org> From: Mauricio Faria de Oliveira Date: Mon, 31 Jan 2022 23:23:50 -0300 Message-ID: Subject: Re: [PATCH v3] mm: fix race between MADV_FREE reclaim and blkdev direct IO read To: Andrew Morton Cc: Minchan Kim , "Huang, Ying" , Yu Zhao , Yang Shi , Miaohe Lin , linux-mm@kvack.org, linux-block@vger.kernel.org Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: EE60F1C0005 X-Stat-Signature: ic3ghe59cwm1ptstk7gzx96qadx8jghz X-Rspam-User: nil Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=canonical.com header.s=20210705 header.b="M+/C+Wpj"; spf=pass (imf20.hostedemail.com: domain of mauricio.oliveira@canonical.com designates 185.125.188.122 as permitted sender) smtp.mailfrom=mauricio.oliveira@canonical.com; dmarc=pass (policy=none) header.from=canonical.com X-HE-Tag: 1643682248-511905 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 Mon, Jan 31, 2022 at 8:43 PM Andrew Morton wrote: > > On Mon, 31 Jan 2022 20:02:55 -0300 Mauricio Faria de Oliveira wrote: > > > Problem: > > ======= > > > > Userspace might read the zero-page instead of actual data from a > > direct IO read on a block device if the buffers have been called > > madvise(MADV_FREE) on earlier (this is discussed below) due to a > > race between page reclaim on MADV_FREE and blkdev direct IO read. > > > > ... > > > > Fixes: 802a3a92ad7a ("mm: reclaim MADV_FREE pages") > > Five years ago. As it doesn't seem urgent I targeted 5.18-rc1 for > this, and added a cc:stable so it will trickle back into earlier trees. > > How does this plan sound? That sounds good; it's not urgent, indeed. Thanks! -- Mauricio Faria de Oliveira