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From: Arnd Bergmann <arnd@arndb.de>
To: Christoph Hellwig <hch@infradead.org>
Cc: David Howells <dhowells@redhat.com>,
	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	[thread overview]
Message-ID: <3204439.9qcmCY96fi@wuerfel> (raw)
In-Reply-To: <20160512091141.GA22420@infradead.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.

WARNING: multiple messages have this Message-ID
From: Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>
To: Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
Cc: David Howells <dhowells-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-afs-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org,
	linux-nfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	samba-technical-w/Ol4Ecudpl8XjKLYN78aQ@public.gmane.org,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-ext4-u79uwXL29TY76Z2rM5mHXA@public.gmane.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	[thread overview]
Message-ID: <3204439.9qcmCY96fi@wuerfel> (raw)
In-Reply-To: <20160512091141.GA22420-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.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.
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  reply	other threads:[~2016-05-13 15:29 UTC|newest]

Thread overview: 76+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-04-29 12:57 [RFC][PATCH 0/6] Enhanced file stat system call David Howells
2016-04-29 12:57 ` [PATCH 1/6] statx: Add a system call to make enhanced file info available David Howells
2016-05-02 22:46   ` Andreas Dilger
2016-05-02 22:46     ` Andreas Dilger
2016-05-03 15:53   ` David Howells
2016-05-04 22:56   ` Dave Chinner
2016-05-05  0:09     ` NeilBrown
2016-05-05  0:09       ` NeilBrown
2016-05-05 19:48       ` Jeff Layton
2016-05-06 18:07         ` J. Bruce Fields
2016-05-06 18:07           ` J. Bruce Fields
2016-05-05 20:04       ` David Howells
2016-05-05 20:04         ` David Howells
2016-05-06  1:39         ` Dave Chinner
2016-05-06  1:39           ` Dave Chinner
2016-05-06  1:39           ` Dave Chinner
2016-05-06 18:29     ` J. Bruce Fields
2016-05-09  1:45       ` Dave Chinner
2016-05-09  2:46         ` J. Bruce Fields
2016-05-04 23:56   ` NeilBrown
2016-05-08  8:35   ` Christoph Hellwig
2016-05-08  8:35     ` Christoph Hellwig
2016-05-09 12:02     ` Jeff Layton
2016-05-09 12:02       ` Jeff Layton
2016-05-10  7:00       ` Christoph Hellwig
2016-05-10  7:00         ` Christoph Hellwig
2016-05-10 13:21         ` Jeff Layton
2016-05-10 13:21           ` Jeff Layton
2016-05-09 12:57   ` David Howells
2016-05-09 12:57     ` David Howells
2016-05-09 13:23     ` Trond Myklebust
2016-05-09 13:23       ` Trond Myklebust
2016-05-09 13:23       ` Trond Myklebust
2016-05-10  7:04     ` Christoph Hellwig
2016-05-10  8:25     ` David Howells
2016-05-12  9:11       ` Christoph Hellwig
2016-05-13 15:28         ` Arnd Bergmann [this message]
2016-05-13 15:28           ` Arnd Bergmann
2016-05-23  8:22           ` Christoph Hellwig
2016-05-23  9:33           ` David Howells
2016-05-18 10:55         ` David Howells
2016-05-09 13:00   ` David Howells
2016-05-09 13:00     ` David Howells
2016-05-09 13:38   ` David Howells
2016-05-10  7:08     ` Christoph Hellwig
2016-05-10  8:43     ` David Howells
2016-05-12  9:12       ` Christoph Hellwig
2016-05-09 13:40   ` David Howells
2016-04-29 12:57 ` [PATCH 2/6] statx: AFS: Return enhanced file attributes David Howells
2016-04-29 12:57 ` [PATCH 3/6] statx: Ext4: " David Howells
2016-05-02 22:48   ` Andreas Dilger
2016-05-03 20:24   ` David Howells
2016-05-03 20:24     ` David Howells
2016-05-08  8:38   ` Christoph Hellwig
2016-05-08  8:38     ` Christoph Hellwig
2016-04-29 12:58 ` [PATCH 4/6] statx: NFS: " David Howells
2016-05-02 22:48   ` Andreas Dilger
2016-04-29 12:58 ` [PATCH 5/6] statx: Make windows attributes available for CIFS, NTFS and FAT to use David Howells
2016-05-02 22:52   ` Andreas Dilger
2016-10-03 21:03     ` Steve French
2016-10-03 21:03       ` Steve French
2016-05-03 20:23   ` David Howells
2016-05-08  8:39   ` Christoph Hellwig
2016-05-08  8:39     ` Christoph Hellwig
2016-04-29 12:58 ` [PATCH 6/6] statx: CIFS: Return enhanced attributes David Howells
2016-04-30 21:05 ` [RFC][PATCH 0/6] Enhanced file stat system call Jeff Layton
2016-04-30 21:05   ` Jeff Layton
2016-05-04 13:46 ` Arnd Bergmann
2016-05-04 13:46   ` Arnd Bergmann
2016-05-05 22:54   ` Steve French
2016-05-06  2:00     ` Steve French
2016-05-09 13:09       ` Arnd Bergmann
2016-05-09 13:09         ` Arnd Bergmann
2016-05-13 14:28         ` Richard Sharpe
2016-05-13 14:28           ` Richard Sharpe
2016-05-13 15:08           ` Arnd Bergmann

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