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Date: Thu, 21 May 2020 11:11:50 +0200 From: 'Christoph Hellwig' <hch@....de> To: David Laight <David.Laight@...LAB.COM> Cc: 'Christoph Hellwig' <hch@....de>, "David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, Eric Dumazet <edumazet@...gle.com>, Alexey Kuznetsov <kuznet@....inr.ac.ru>, Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>, Vlad Yasevich <vyasevich@...il.com>, Neil Horman <nhorman@...driver.com>, Marcelo Ricardo Leitner <marcelo.leitner@...il.com>, Jon Maloy <jmaloy@...hat.com>, Ying Xue <ying.xue@...driver.com>, "drbd-dev@...ts.linbit.com" <drbd-dev@...ts.linbit.com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>, "linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>, "target-devel@...r.kernel.org" <target-devel@...r.kernel.org>, "linux-afs@...ts.infradead.org" <linux-afs@...ts.infradead.org>, "linux-cifs@...r.kernel.org" <linux-cifs@...r.kernel.org>, "cluster-devel@...hat.com" <cluster-devel@...hat.com>, "ocfs2-devel@....oracle.com" <ocfs2-devel@....oracle.com>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>, "linux-sctp@...r.kernel.org" <linux-sctp@...r.kernel.org>, "ceph-devel@...r.kernel.org" <ceph-devel@...r.kernel.org>, "rds-devel@....oracle.com" <rds-devel@....oracle.com>, "linux-nfs@...r.kernel.org" <linux-nfs@...r.kernel.org> Subject: Re: remove kernel_setsockopt and kernel_getsockopt v2 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.
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