From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jerome Glisse Subject: Re: [PATCH v4 0/1] Use HMM for ODP v4 Date: Thu, 23 May 2019 15:39:59 -0400 Message-ID: <20190523193959.GA5658@redhat.com> References: <20190522174852.GA23038@redhat.com> <20190522235737.GD15389@ziepe.ca> <20190523150432.GA5104@redhat.com> <20190523154149.GB12159@ziepe.ca> <20190523155207.GC5104@redhat.com> <20190523163429.GC12159@ziepe.ca> <20190523173302.GD5104@redhat.com> <20190523175546.GE12159@ziepe.ca> <20190523182458.GA3571@redhat.com> <20190523191038.GG12159@ziepe.ca> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Return-path: Content-Disposition: inline In-Reply-To: <20190523191038.GG12159@ziepe.ca> Sender: linux-kernel-owner@vger.kernel.org To: Jason Gunthorpe Cc: linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org, Leon Romanovsky , Doug Ledford , Artemy Kovalyov , Moni Shoua , Mike Marciniszyn , Kaike Wan , Dennis Dalessandro List-Id: linux-rdma@vger.kernel.org On Thu, May 23, 2019 at 04:10:38PM -0300, Jason Gunthorpe wrote: > > On Thu, May 23, 2019 at 02:24:58PM -0400, Jerome Glisse wrote: > > I can not take mmap_sem in range_register, the READ_ONCE is fine and > > they are no race as we do take a reference on the hmm struct thus > > Of course there are use after free races with a READ_ONCE scheme, I > shouldn't have to explain this. Well i can not think of anything again here the mm->hmm can not change while driver is calling hmm_range_register() so if you want i can remove the READ_ONCE() this does not change anything. > If you cannot take the read mmap sem (why not?), then please use my > version and push the update to the driver through -mm.. Please see previous threads on why it was a failure. Cheers, Jérôme