From: Arnd Bergmann Subject: Re: [PATCH 01/12] Ext4: Fix extended timestamp encoding and decoding Date: Mon, 30 Nov 2015 15:37:43 +0100 Message-ID: <4966628.zR0sijQ42t@wuerfel> References: <20151120145422.18930.72662.stgit@warthog.procyon.org.uk> <2872067.shHdUXoF07@wuerfel> <20151130141605.GA4316@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Cc: David Howells , linux-afs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-cifs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, samba-technical-w/Ol4Ecudpl8XjKLYN78aQ@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-ext4-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Deepa Dinamani To: Theodore Ts'o Return-path: In-Reply-To: <20151130141605.GA4316-AKGzg7BKzIDYtjvyW6yDsg@public.gmane.org> Sender: linux-nfs-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-ext4.vger.kernel.org On Monday 30 November 2015 09:16:05 Theodore Ts'o wrote: > On Sun, Nov 29, 2015 at 10:30:39PM +0100, Arnd Bergmann wrote: > > The other large missing piece is the system call implementation. I have > > posted a series earlier this year before my parental leave, and it's > > currently lacking review from libc folks, and blocked on me to update > > the series and post it again. > > I assume that this also means there hasn't been much thought about > userspace support above libc? i.e., how to take a 64-bit time64_t (or > changing the size of time_t) and translating that to a string using > some kind of version of ctime() and asctime(), and how to parse a > post-2038 date string and turning it into a 64-bit time_t on a 32-bit > platform? > > The reason why I'm asking is because I'm thinking about how to add the > appropriate regression test support to e2fsprogs for 32-bit platforms. > I'm probably going to just skip the tests on architectures where > sizeof(time_t) == 4 for now, since with a 32-bit time_t adding support > for post-2038 in a e2fsprogs-specific way is (a) something I don't > have time for, and (b) probably a waste of time since presumably we > will either need to have a more general solution, or simply decide to > give up on 32-bit platforms by 2038.... We are definitely going to be using 32-bit embedded platforms in 2038, but we won't be using a 32-bit time_t then, so basing the check on sizeof(time_t) sounds reasonable. I assume most generic distros will stay with 32-bit time_t for compatibility reasons and just not give long term support for 32-bit architectures, while the embedded distros will move over to 64-bit time_t, but on those you recompile all user space for each product anyway. The glibc functions should all work with a 64-bit time_t as they do today on 64-bit architectures. There is an open discussion on how you move to 64-bit time_t. With the current glibc plan at https://sourceware.org/glibc/wiki/Y2038ProofnessDesign, you will have to set -D_TIME_BITS=64 to enable it explicitly, but I'd also like to see a way to build a glibc that defaults to that and does not allow backwards compatibility, which is important for folks that want to ship a system that has they can guarantee to survive 2038. Arnd -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html