From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753413AbcEMP3L (ORCPT ); Fri, 13 May 2016 11:29:11 -0400 Received: from mout.kundenserver.de ([212.227.126.135]:50167 "EHLO mout.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753352AbcEMP3I (ORCPT ); Fri, 13 May 2016 11:29:08 -0400 From: Arnd Bergmann To: Christoph Hellwig Cc: David Howells , linux-fsdevel@vger.kernel.org, linux-afs@lists.infradead.org, linux-nfs@vger.kernel.org, samba-technical@lists.samba.org, linux-kernel@vger.kernel.org, linux-ext4@vger.kernel.org Subject: Re: [PATCH 1/6] statx: Add a system call to make enhanced file info available Date: Fri, 13 May 2016 17:28:11 +0200 Message-ID: <3204439.9qcmCY96fi@wuerfel> User-Agent: KMail/4.11.5 (Linux/3.16.0-10-generic; KDE/4.11.5; x86_64; ; ) In-Reply-To: <20160512091141.GA22420@infradead.org> References: <20160510070421.GB30896@infradead.org> <6897.1462868755@warthog.procyon.org.uk> <20160512091141.GA22420@infradead.org> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-Provags-ID: V03:K0:2s80atsPfwDeRd/PBUs6jA/y2IWCo25q92prx575YqUzjEjW5Ey nW/KU6m1pcB2+AksqCetwWxUmnEDPH5BJtpzo8aQjUIEaZxuVcMKpU9f1ji9c9r2YuK/NQt LMwX6vB2L302NRZZ1zr7zrKE5OLSJumv4u71Y6AkmlFzVyAmCM6mQ58lOTp0JBdUhrUMfGl /5U33afYeLw8vlH51er2A== X-UI-Out-Filterresults: notjunk:1;V01:K0:jZ2fOPeGs3U=:HWB0BzzYd+UUdP3JTUYZCA zT24zjJMhbxD5bG8GIO0C46gm8MeygfR7ShnZ5VFvBURyFwPAAPK4xMja0kv6a1NZV8Ay+I/r rPfZvJNj2oYW9QRGcNVwDhMfpPwBzlIcZapuBFMLkEJLp25Z01XG+4g0ZCcZYkL1ElDB0l/NK Qul5bcfnieXSZ+cLdbooVTcjDVYvqr7WpsU6lUNsOg9tezf3WiZ4BjWErlpqvlDDtEpOZaxjv Rv9+ig5TCLgG+kk9zgtWtpUiH96db65LshCMLIY8G7IZWFKR2Byn51MVWRerJ3gtgPz9nGchA BkcXTBYcelwMsIZMKhN/4q0qkPuMVkwKrY6CbncAlH6I40YYcztb8JR+UpmTB8B/Ai3ylwbeI RsMYggZXnw4DSbRBW0hiujbxixXn/qo2UWRH1A+RcXVVcvLrlQVW2qkpWxv4Wa5wUeo9ZWRzF 64qgC0nVXk/vc/NNQE1Pw7WGyWqB/GkNg2hp4NC10kOIm5tLjFm4ri6owtf6xgC+KlLSVmxeF bgshxE5v27HXLXEZ1ftGggRjK1gFEX1+pZxrC03brvOmTkNdzpx7+V+skdVtuORkUd2tCwDz+ vP7RwDmJAqKRICEeStx5UT9Xar4RHErNawLQ27gYYjDdork2svR5j8bRs5EA9oWoHijglWpei Ifb8NFbin1J37m3RCFuQ7XRWqGw/7K8yP0FBGApoXD9d47Bv731iz3sJsR1p/THdUC1KPbzQ2 RBkyBbZdq8fQ0SJ0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thursday 12 May 2016 02:11:41 Christoph Hellwig wrote: > On Tue, May 10, 2016 at 09:25:55AM +0100, David Howells wrote: > > Because it's not necessarily a perfectly working version of it. See the Y2037 > > problem for example. > > > > I was assuming that C libraries might want to update the struct stat and the > > stat call() to provide fields that aren't currently there in Linux but are in > > other OS's. We could even dispense with older stat syscalls on new arches. > > Please stop this whole let's get rid of old syscalls on new > architectures stuff. This just means we have to do the translation > multiple, and the one in userspace is more costly as we it needs to be > in every copy of the library. And times where we had a single libc > instance (nevermind implementation) are long over if we ever actually > had them. I'm trying to understand what that means for the 64-bit time_t syscalls. The patch series I did last year had a replacement 'sys_newfstatat()' syscall but IIRC no other stat variant, the idea being that we would only need to provide this one to the libc and have user space emulate the stat/fstat/lstat/fstatat variants based on that. With the statx introduction, I was hoping to no longer have to add that syscall but instead have libc do everything on top of sys_statx(). Do you think that is reasonable, given that we won't be allowed to call any of the existing stat() variants for a y2038-safe libc build[1], or should we plan to keep needing replacement fstatat (and possibly stat/lstat/fstat) syscalls with 64-bit time_t even after statx() support is merged into the kernel. Arnd [1] the glibc developers plan to allow compatibility for 32-bit time_t and 64-bit time_t in the same binary, but any user space code built with 64-bit time_t must never call into kernel interfaces that use a 32-bit time_t.