From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by mail19.linbit.com (LINBIT Mail Daemon) with ESMTP id C85964203D6 for ; Thu, 21 May 2020 11:11:54 +0200 (CEST) Date: Thu, 21 May 2020 11:11:50 +0200 From: 'Christoph Hellwig' To: David Laight Message-ID: <20200521091150.GA8401@lst.de> References: <20200520195509.2215098-1-hch@lst.de> <138a17dfff244c089b95f129e4ea2f66@AcuMS.aculab.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <138a17dfff244c089b95f129e4ea2f66@AcuMS.aculab.com> Cc: Marcelo Ricardo Leitner , Eric Dumazet , "linux-nvme@lists.infradead.org" , "linux-sctp@vger.kernel.org" , "target-devel@vger.kernel.org" , "linux-afs@lists.infradead.org" , "drbd-dev@lists.linbit.com" , "linux-cifs@vger.kernel.org" , "rds-devel@oss.oracle.com" , "linux-rdma@vger.kernel.org" , 'Christoph Hellwig' , "cluster-devel@redhat.com" , Alexey Kuznetsov , Jakub Kicinski , "ceph-devel@vger.kernel.org" , "linux-nfs@vger.kernel.org" , Neil Horman , Hideaki YOSHIFUJI , "netdev@vger.kernel.org" , Vlad Yasevich , "linux-kernel@vger.kernel.org" , Jon Maloy , Ying Xue , "David S. Miller" , "ocfs2-devel@oss.oracle.com" Subject: Re: [Drbd-dev] remove kernel_setsockopt and kernel_getsockopt v2 List-Id: "*Coordination* of development, patches, contributions -- *Questions* \(even to developers\) go to drbd-user, please." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Thu, May 21, 2020 at 08:01:33AM +0000, David Laight wrote: > How much does this increase the kernel code by? 44 files changed, 660 insertions(+), 843 deletions(-) > You are also replicating a lot of code making it more > difficult to maintain. No, I specifically don't. > I don't think the performance of an socket option code > really matters - it is usually done once when a socket > is initialised and the other costs of establishing a > connection will dominate. > > Pulling the user copies outside the [gs]etsocksopt switch > statement not only reduces the code size (source and object) > and trivially allows kernel_[sg]sockopt() to me added to > the list of socket calls. > > It probably isn't possible to pull the usercopies right > out into the syscall wrapper because of some broken > requests. Please read through the previous discussion of the rationale and the options. We've been there before. > I worried about whether getsockopt() should read the entire > user buffer first. SCTP needs the some of it often (including a > sockaddr_storage in one case), TCP needs it once. > However the cost of reading a few words is small, and a big > buffer probably needs setting to avoid leaking kernel > memory if the structure has holes or fields that don't get set. > Reading from userspace solves both issues. As mention in the thread on the last series: That was my first idea, but we have way to many sockopts, especially in obscure protocols that just hard code the size. The chance of breaking userspace in a way that can't be fixed without going back to passing user pointers to get/setsockopt is way to high to commit to such a change unfortunately.