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Gokhale" , Yang Shi , Marty Mcfadden , Kirill Shutemov , Oleg Nesterov , Jann Horn , Jan Kara , Kirill Tkhai , Andrea Arcangeli , Christoph Hellwig , Andrew Morton Subject: Re: [PATCH 1/4] mm: Trial do_wp_page() simplification Message-ID: <20200914143829.GA1424636@nvidia.com> References: <20200821234958.7896-1-peterx@redhat.com> <20200821234958.7896-2-peterx@redhat.com> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20200821234958.7896-2-peterx@redhat.com> X-ClientProxiedBy: CH2PR17CA0029.namprd17.prod.outlook.com (2603:10b6:610:53::39) To DM6PR12MB3834.namprd12.prod.outlook.com (2603:10b6:5:14a::12) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from mlx.ziepe.ca (206.223.160.26) by CH2PR17CA0029.namprd17.prod.outlook.com (2603:10b6:610:53::39) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3370.16 via Frontend Transport; Mon, 14 Sep 2020 14:38:30 +0000 Received: from jgg by mlx with local (Exim 4.94) (envelope-from ) id 1kHpcj-005ygP-Kp; 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b=WPwy59YK73hKNoWdWVNFT7btv0OEGdauPQEAkFjEAPSGfkb3k4Fm2/tGuhg762KIL uitR0oIkn48u1l375ZpOUl/awXFihj88siUa5elQD7eCdCLcg+lCyxGcsTsDcxdObn /tvO9KviLydhgKp7l+XVvUA1BSKk4C5mqNiwWb7J8aNJsgEHzkuvcg7qcEN9p1wkuX +twLMQT3lHSMoawp9aST3Sd2q73Tq0HVLLnvAuzmCPfRgsVC4MZ2yHsI4MvCR4IaWh 7UQ2fYgblAFgBZs0EeP5byjzZHu4aH0776cTuFKHdL688luajHu4/dL2NrX1Cmmykj BGlNFFmGI8tBw== Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 21, 2020 at 07:49:55PM -0400, Peter Xu wrote: > From: Linus Torvalds > > How about we just make sure we're the only possible valid user fo the > page before we bother to reuse it? > > Simplify, simplify, simplify. > > And get rid of the nasty serialization on the page lock at the same time. > > Signed-off-by: Linus Torvalds > [peterx: add subject prefix] > Signed-off-by: Peter Xu > mm/memory.c | 59 +++++++++++++++-------------------------------------- > 1 file changed, 17 insertions(+), 42 deletions(-) I don't have a detailed explanation right now, but this patch appears to be causing a regression where RDMA subsystem tests fail. Tests return to normal when this patch is reverted. It kind of looks like the process is not seeing DMA'd data to a pin_user_pages()? Thanks, Jason