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[174.3.196.123]) by smtp.gmail.com with ESMTPSA id v19-v6sm3470934wmc.9.2018.06.27.07.57.22 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 27 Jun 2018 07:57:22 -0700 (PDT) Received: from jgg by mlx.ziepe.ca with local (Exim 4.86_2) (envelope-from ) id 1fYBsk-0005aW-Kv; Wed, 27 Jun 2018 08:57:18 -0600 Date: Wed, 27 Jun 2018 08:57:18 -0600 From: Jason Gunthorpe To: Jan Kara Cc: Michal Hocko , Dan Williams , John Hubbard , Christoph Hellwig , John Hubbard , Matthew Wilcox , Christopher Lameter , Linux MM , LKML , linux-rdma Subject: Re: [PATCH 2/2] mm: set PG_dma_pinned on get_user_pages*() Message-ID: <20180627145718.GB20171@ziepe.ca> References: <3898ef6b-2fa0-e852-a9ac-d904b47320d5@nvidia.com> <20180626134757.GY28965@dhcp22.suse.cz> <20180626164825.fz4m2lv6hydbdrds@quack2.suse.cz> <20180627113221.GO32348@dhcp22.suse.cz> <20180627115349.cu2k3ainqqdrrepz@quack2.suse.cz> <20180627115927.GQ32348@dhcp22.suse.cz> <20180627124255.np2a6rxy6rb6v7mm@quack2.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180627124255.np2a6rxy6rb6v7mm@quack2.suse.cz> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 27, 2018 at 02:42:55PM +0200, Jan Kara wrote: > On Wed 27-06-18 13:59:27, Michal Hocko wrote: > > On Wed 27-06-18 13:53:49, Jan Kara wrote: > > > On Wed 27-06-18 13:32:21, Michal Hocko wrote: > > [...] > > > > Appart from that, do we really care about 32b here? Big DIO, IB users > > > > seem to be 64b only AFAIU. > > > > > > IMO it is a bad habit to leave unpriviledged-user-triggerable oops in the > > > kernel even for uncommon platforms... > > > > Absolutely agreed! I didn't mean to keep the blow up for 32b. I just > > wanted to say that we can stay with a simple solution for 32b. I thought > > the g-u-p-longterm has plugged the most obvious breakage already. But > > maybe I just misunderstood. > > Most yes, but if you try hard enough, you can still trigger the oops e.g. > with appropriately set up direct IO when racing with writeback / reclaim. gup longterm is only different from normal gup if you have DAX and few people do, which really means it doesn't help at all.. AFAIK?? Jason