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[134.134.136.31]) by mx.google.com with ESMTPS id c131si13774963pga.358.2019.02.26.17.13.18 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 26 Feb 2019 17:13:18 -0800 (PST) Received-SPF: pass (google.com: domain of ying.huang@intel.com designates 134.134.136.31 as permitted sender) client-ip=134.134.136.31; Authentication-Results: mx.google.com; spf=pass (google.com: domain of ying.huang@intel.com designates 134.134.136.31 as permitted sender) smtp.mailfrom=ying.huang@intel.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga003.jf.intel.com ([10.7.209.27]) by orsmga104.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 26 Feb 2019 17:13:18 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.58,417,1544515200"; d="scan'208";a="129624334" Received: from yhuang-dev.sh.intel.com (HELO yhuang-dev) ([10.239.159.151]) by orsmga003.jf.intel.com with ESMTP; 26 Feb 2019 17:13:14 -0800 From: "Huang\, Ying" To: Daniel Jordan Cc: Andrea Arcangeli , Andrew Morton , , , Hugh Dickins , "Paul E . McKenney" , Minchan Kim , Johannes Weiner , "Tim Chen" , Mel Gorman , =?utf-8?B?SsOpcsO0bWU=?= Glisse , Michal Hocko , David Rientjes , Rik van Riel , Jan Kara , Dave Jiang , Aaron Lu , Andrea Parri Subject: Re: [PATCH -mm -V8] mm, swap: fix race between swapoff and some swap operations References: <20190218070142.5105-1-ying.huang@intel.com> <87mumjt57i.fsf@yhuang-dev.intel.com> <20190226230729.bz2ukzlub3rbdoqp@ca-dmjordan1.us.oracle.com> Date: Wed, 27 Feb 2019 09:13:14 +0800 In-Reply-To: <20190226230729.bz2ukzlub3rbdoqp@ca-dmjordan1.us.oracle.com> (Daniel Jordan's message of "Tue, 26 Feb 2019 18:07:29 -0500") Message-ID: <87imx6rq39.fsf@yhuang-dev.intel.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=ascii 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: Daniel Jordan writes: > On Tue, Feb 26, 2019 at 02:49:05PM +0800, Huang, Ying wrote: >> Do you have time to take a look at this patch? > > Hi Ying, is this handling all places where swapoff might cause a task to read > invalid data? For example, why don't other reads of swap_map (for example > swp_swapcount, page_swapcount, swap_entry_free) need to be synchronized like > this? I have checked these places. They are safe because there are some locks (like page lock, page table lock, etc.) held to prevent swapoff. I found another place in the kernel that is unsafe: the mincore. I have a patch for that and will post it (in fact again) after this one is merged. Best Regards, Huang, Ying