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Re: [PATCH 01/12] Ext4: Fix extended timestamp encoding and decoding

From Arnd Bergmann <arnd@arndb.de>
Newsgroups linux.kernel
Subject Re: [PATCH 01/12] Ext4: Fix extended timestamp encoding and decoding
Date 2015-11-30 15:40 +0100
Message-ID <qAxMu-4Or-25@gated-at.bofh.it> (permalink)
References <qwVkl-6h-3@gated-at.bofh.it> <qAhRo-2Xn-27@gated-at.bofh.it> <qAxt8-4HX-13@gated-at.bofh.it>
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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
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[RFC][PATCH 00/12] Enhanced file stat system call David Howells <dhowells@redhat.com> - 2015-11-20 16:00 +0100
  [PATCH 04/12] statx: AFS: Return enhanced file attributes David Howells <dhowells@redhat.com> - 2015-11-20 16:00 +0100
  [PATCH 11/12] fsinfo: NFS: Return information through the  filesystem info syscall David Howells <dhowells@redhat.com> - 2015-11-20 16:00 +0100
  [PATCH 07/12] statx: CIFS: Return enhanced attributes David Howells <dhowells@redhat.com> - 2015-11-20 16:00 +0100
    Re: [PATCH 07/12] statx: CIFS: Return enhanced attributes Steve French <smfrench@gmail.com> - 2015-11-24 18:40 +0100
  [PATCH 01/12] Ext4: Fix extended timestamp encoding and decoding David Howells <dhowells@redhat.com> - 2015-11-20 16:00 +0100
    Re: [PATCH 01/12] Ext4: Fix extended timestamp encoding and decoding Andreas Dilger <adilger@dilger.ca> - 2015-11-24 18:40 +0100
    Re: [PATCH 01/12] Ext4: Fix extended timestamp encoding and decoding Theodore Ts'o <tytso@mit.edu> - 2015-11-24 20:40 +0100
      Re: [PATCH 01/12] Ext4: Fix extended timestamp encoding and decoding Arnd Bergmann <arnd@arndb.de> - 2015-11-24 21:20 +0100
        Re: [PATCH 01/12] Ext4: Fix extended timestamp encoding and decoding Theodore Ts'o <tytso@mit.edu> - 2015-11-29 03:50 +0100
          Re: [PATCH 01/12] Ext4: Fix extended timestamp encoding and decoding Arnd Bergmann <arnd@arndb.de> - 2015-11-29 22:40 +0100
            Re: [PATCH 01/12] Ext4: Fix extended timestamp encoding and decoding Theodore Ts'o <tytso@mit.edu> - 2015-11-30 15:20 +0100
              Re: [PATCH 01/12] Ext4: Fix extended timestamp encoding and decoding Arnd Bergmann <arnd@arndb.de> - 2015-11-30 15:40 +0100
              Re: [PATCH 01/12] Ext4: Fix extended timestamp encoding and decoding Elmar Stellnberger <estellnb@elstel.org> - 2015-11-30 16:00 +0100
      Re: [PATCH 01/12] Ext4: Fix extended timestamp encoding and decoding David Howells <dhowells@redhat.com> - 2015-11-26 16:30 +0100
  Re: [RFC][PATCH 00/12] Enhanced file stat system call Martin Steigerwald <martin@lichtvoll.de> - 2015-11-20 17:30 +0100
    Re: [RFC][PATCH 00/12] Enhanced file stat system call David Howells <dhowells@redhat.com> - 2015-11-20 17:30 +0100
      Re: [RFC][PATCH 00/12] Enhanced file stat system call Martin Steigerwald <martin@lichtvoll.de> - 2015-11-20 17:40 +0100
      Re: [RFC][PATCH 00/12] Enhanced file stat system call bfields@fieldses.org (J. Bruce Fields) - 2015-11-25 19:00 +0100
        Re: [RFC][PATCH 00/12] Enhanced file stat system call Andreas Dilger <adilger@dilger.ca> - 2015-11-25 20:40 +0100
    Re: [RFC][PATCH 00/12] Enhanced file stat system call Christoph Hellwig <hch@infradead.org> - 2015-11-24 09:20 +0100
      Re: [RFC][PATCH 00/12] Enhanced file stat system call Martin Steigerwald <martin@lichtvoll.de> - 2015-11-24 09:50 +0100
        Re: [RFC][PATCH 00/12] Enhanced file stat system call Christoph Hellwig <hch@infradead.org> - 2015-11-24 10:00 +0100
  Re: [RFC][PATCH 00/12] Enhanced file stat system call Casey Schaufler <casey@schaufler-ca.com> - 2015-11-20 18:00 +0100
    Re: [RFC][PATCH 00/12] Enhanced file stat system call Christoph Hellwig <hch@infradead.org> - 2015-11-24 09:20 +0100
      Re: [RFC][PATCH 00/12] Enhanced file stat system call Casey Schaufler <casey@schaufler-ca.com> - 2015-11-24 16:00 +0100
    Re: [RFC][PATCH 00/12] Enhanced file stat system call Andreas Dilger <adilger@dilger.ca> - 2015-11-24 17:30 +0100
  Re: [RFC][PATCH 00/12] Enhanced file stat system call Christoph Hellwig <hch@infradead.org> - 2015-11-24 09:20 +0100
    Re: [RFC][PATCH 00/12] Enhanced file stat system call David Howells <dhowells@redhat.com> - 2015-11-26 16:20 +0100
      Re: [RFC][PATCH 00/12] Enhanced file stat system call Andreas Dilger <adilger@dilger.ca> - 2015-11-26 23:10 +0100
  Re: [PATCH 03/12] statx: Add a system call to make enhanced file  info available Dave Chinner <david@fromorbit.com> - 2015-11-24 21:30 +0100
  Re: [PATCH 03/12] statx: Add a system call to make enhanced file  info available Pavel Machek <pavel@ucw.cz> - 2015-12-04 13:10 +0100

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