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From: Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>
To: Theodore Ts'o <tytso-3s7WtUTddSA@public.gmane.org>
Cc: David Howells <dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	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
	<deepa.kernel-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Subject: Re: [PATCH 01/12] Ext4: Fix extended timestamp encoding and decoding
Date: Mon, 30 Nov 2015 15:37:43 +0100	[thread overview]
Message-ID: <4966628.zR0sijQ42t@wuerfel> (raw)
In-Reply-To: <20151130141605.GA4316-AKGzg7BKzIDYtjvyW6yDsg@public.gmane.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
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WARNING: multiple messages have this Message-ID
From: Arnd Bergmann <arnd@arndb.de>
To: "Theodore Ts'o" <tytso@mit.edu>
Cc: David Howells <dhowells@redhat.com>,
	linux-afs@vger.kernel.org, linux-nfs@vger.kernel.org,
	linux-cifs@vger.kernel.org, samba-technical@lists.samba.org,
	linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-ext4@vger.kernel.org,
	Deepa Dinamani <deepa.kernel@gmail.com>
Subject: Re: [PATCH 01/12] Ext4: Fix extended timestamp encoding and decoding
Date: Mon, 30 Nov 2015 15:37:43 +0100	[thread overview]
Message-ID: <4966628.zR0sijQ42t@wuerfel> (raw)
In-Reply-To: <20151130141605.GA4316@thunk.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

  parent reply	other threads:[~2015-11-30 14:37 UTC|newest]

Thread overview: 64+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-11-20 14:54 [RFC][PATCH 00/12] Enhanced file stat system call David Howells
2015-11-20 14:54 ` [PATCH 01/12] Ext4: Fix extended timestamp encoding and decoding David Howells
     [not found]   ` <20151120145434.18930.89755.stgit-S6HVgzuS8uM4Awkfq6JHfwNdhmdF6hFW@public.gmane.org>
2015-11-24 17:37     ` Andreas Dilger
2015-11-24 17:37       ` Andreas Dilger
2015-11-24 19:36   ` Theodore Ts'o
     [not found]     ` <20151124193646.GA3482-AKGzg7BKzIDYtjvyW6yDsg@public.gmane.org>
2015-11-24 20:10       ` Arnd Bergmann
2015-11-24 20:10         ` Arnd Bergmann
2015-11-29  2:45         ` Theodore Ts'o
2015-11-29  2:45           ` Theodore Ts'o
     [not found]           ` <20151129024555.GA31968-AKGzg7BKzIDYtjvyW6yDsg@public.gmane.org>
2015-11-29 21:30             ` Arnd Bergmann
2015-11-29 21:30               ` Arnd Bergmann
2015-11-30 14:16               ` Theodore Ts'o
     [not found]                 ` <20151130141605.GA4316-AKGzg7BKzIDYtjvyW6yDsg@public.gmane.org>
2015-11-30 14:37                   ` Arnd Bergmann [this message]
2015-11-30 14:37                     ` Arnd Bergmann
2015-11-30 14:46                 ` Elmar Stellnberger
2015-11-26 15:28       ` David Howells
2015-11-26 15:28         ` David Howells
2015-11-20 14:54 ` [PATCH 02/12] statx: Provide IOC flags for Windows fs attributes David Howells
     [not found]   ` <20151120145447.18930.5308.stgit-S6HVgzuS8uM4Awkfq6JHfwNdhmdF6hFW@public.gmane.org>
2015-11-24 19:52     ` Theodore Ts'o
2015-11-24 19:52       ` Theodore Ts'o
2015-11-26 15:35   ` David Howells
     [not found]   ` <7976.1448552129-S6HVgzuS8uM4Awkfq6JHfwNdhmdF6hFW@public.gmane.org>
2015-11-26 16:01     ` David Howells
2015-11-26 16:01       ` David Howells
2015-11-26 22:10     ` Andreas Dilger
2015-11-26 22:10       ` Andreas Dilger
2015-11-20 14:54 ` [PATCH 03/12] statx: Add a system call to make enhanced file info available David Howells
     [not found]   ` <20151120145457.18930.79678.stgit-S6HVgzuS8uM4Awkfq6JHfwNdhmdF6hFW@public.gmane.org>
2015-11-24 20:21     ` Dave Chinner
2015-11-24 20:21       ` Dave Chinner
2015-12-04 12:06     ` Pavel Machek
2015-12-04 12:06       ` Pavel Machek
2015-12-21 23:21   ` David Howells
2015-11-20 14:55 ` [PATCH 04/12] statx: AFS: Return enhanced file attributes David Howells
2015-11-20 14:55 ` [PATCH 05/12] statx: Ext4: " David Howells
2015-11-20 14:55 ` [PATCH 06/12] statx: NFS: " David Howells
2015-11-20 14:55 ` [PATCH 07/12] statx: CIFS: Return enhanced attributes David Howells
2015-11-24 17:33   ` Steve French
2015-11-24 17:34   ` Steve French
2015-11-24 17:34     ` Steve French
2015-11-20 14:56 ` [PATCH 08/12] fsinfo: Add a system call to make enhanced filesystem info available David Howells
2015-11-20 14:56 ` [PATCH 09/12] fsinfo: Ext4: Return information through the filesystem info syscall David Howells
2015-11-20 14:56 ` [PATCH 10/12] fsinfo: AFS: " David Howells
2015-11-20 14:56 ` [PATCH 11/12] fsinfo: NFS: " David Howells
     [not found] ` <20151120145422.18930.72662.stgit-S6HVgzuS8uM4Awkfq6JHfwNdhmdF6hFW@public.gmane.org>
2015-11-20 14:56   ` [PATCH 12/12] fsinfo: CIFS: " David Howells
2015-11-20 14:56     ` David Howells
2015-11-24  8:11   ` [RFC][PATCH 00/12] Enhanced file stat system call Christoph Hellwig
2015-11-24  8:11     ` Christoph Hellwig
2015-11-20 16:19 ` Martin Steigerwald
2015-11-24  8:13   ` Christoph Hellwig
2015-11-24  8:48     ` Martin Steigerwald
2015-11-24  8:50       ` Christoph Hellwig
2015-11-20 16:28 ` David Howells
2015-11-20 16:28   ` David Howells
2015-11-20 16:35   ` Martin Steigerwald
     [not found]   ` <4495.1448036915-S6HVgzuS8uM4Awkfq6JHfwNdhmdF6hFW@public.gmane.org>
2015-11-25 17:51     ` J. Bruce Fields
2015-11-25 17:51       ` J. Bruce Fields
     [not found]       ` <20151125175153.GA30335-uC3wQj2KruNg9hUCZPvPmw@public.gmane.org>
2015-11-25 19:30         ` Andreas Dilger
2015-11-25 19:30           ` Andreas Dilger
2015-11-20 16:50 ` Casey Schaufler
     [not found]   ` <564F4F4E.8060603-iSGtlc1asvQWG2LlvL+J4A@public.gmane.org>
2015-11-24  8:15     ` Christoph Hellwig
2015-11-24  8:15       ` Christoph Hellwig
2015-11-24 14:43       ` Casey Schaufler
2015-11-24 16:28   ` Andreas Dilger
2015-11-26 15:19 ` David Howells
2015-11-26 22:06   ` Andreas Dilger

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