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[195.135.220.15]) by mx.google.com with ESMTPS id u16si1413354edx.384.2019.02.12.08.44.54 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 12 Feb 2019 08:44:54 -0800 (PST) Received-SPF: pass (google.com: domain of jack@suse.cz designates 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=pass (google.com: domain of jack@suse.cz designates 195.135.220.15 as permitted sender) smtp.mailfrom=jack@suse.cz X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id AB6ADAF50; Tue, 12 Feb 2019 16:44:53 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id 7FD1F1E09C5; Tue, 12 Feb 2019 17:44:52 +0100 (CET) Date: Tue, 12 Feb 2019 17:44:52 +0100 From: Jan Kara To: Christopher Lameter Cc: Dan Williams , Jason Gunthorpe , Matthew Wilcox , Ira Weiny , Jan Kara , Dave Chinner , Doug Ledford , lsf-pc@lists.linux-foundation.org, linux-rdma , Linux MM , Linux Kernel Mailing List , John Hubbard , Jerome Glisse , Michal Hocko Subject: Re: [LSF/MM TOPIC] Discuss least bad options for resolving longterm-GUP usage by RDMA Message-ID: <20190212164452.GF19076@quack2.suse.cz> References: <20190211102402.GF19029@quack2.suse.cz> <20190211180654.GB24692@ziepe.ca> <20190211181921.GA5526@iweiny-DESK2.sc.intel.com> <20190211182649.GD24692@ziepe.ca> <20190211184040.GF12668@bombadil.infradead.org> <20190211204945.GF24692@ziepe.ca> <01000168e2913f2e-56010847-a10b-407e-b4eb-7730164267de-000000@email.amazonses.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <01000168e2913f2e-56010847-a10b-407e-b4eb-7730164267de-000000@email.amazonses.com> User-Agent: Mutt/1.10.1 (2018-07-13) 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 Tue 12-02-19 16:36:36, Christopher Lameter wrote: > On Mon, 11 Feb 2019, Dan Williams wrote: > > > An mmap write after a fault due to a hole punch is free to trigger > > SIGBUS if the subsequent page allocation fails. So no, I don't see > > them as the same unless you're allowing for the holder of the MR to > > receive a re-fault failure. > > Order 0 page allocation failures are generally not possible in that path. > System will reclaim and OOM before that happens. But also block allocation can fail in the filesystem or you can have memcgs set up that make the page allocation fail, can't you? So in principle Dan is right. Page faults can and do fail... Honza -- Jan Kara SUSE Labs, CR