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From: Dave Chinner <david@fromorbit.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
	joseph@codesourcery.com, john.stultz@linaro.org,
	hch@infradead.org, tglx@linutronix.de, geert@linux-m68k.org,
	lftan@altera.com, hpa@zytor.com, linux-fsdevel@vger.kernel.org,
	xfs@oss.sgi.com
Subject: Re: [RFC 11/32] xfs: convert to struct inode_time
Date: Sat, 31 May 2014 10:37:12 +1000
Message-ID: <20140531003712.GH14410@dastard> (raw)
In-Reply-To: <1401480116-1973111-12-git-send-email-arnd@arndb.de>

On Fri, May 30, 2014 at 10:01:35PM +0200, Arnd Bergmann wrote:
> xfs uses unsigned 32-bit seconds for inode timestamps, which will work
> for the next 92 years, but the VFS uses struct timespec for timestamps,
> which is only good until 2038 on 32-bit CPUs.
> 
> This gets us one small step closer to lifting the VFS limit by using
> struct inode_time in XFS.
> 
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> Cc: Dave Chinner <david@fromorbit.com>
> Cc: xfs@oss.sgi.com
> ---
>  fs/xfs/time.h            | 4 ++--
>  fs/xfs/xfs_inode.c       | 2 +-
>  fs/xfs/xfs_iops.c        | 2 +-
>  fs/xfs/xfs_trans_inode.c | 6 +++---
>  4 files changed, 7 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/xfs/time.h b/fs/xfs/time.h
> index 387e695..a490f1b 100644
> --- a/fs/xfs/time.h
> +++ b/fs/xfs/time.h
> @@ -21,14 +21,14 @@
>  #include <linux/sched.h>
>  #include <linux/time.h>
>  
> -typedef struct timespec timespec_t;
> +typedef struct inode_time timespec_t;
>  
>  static inline void delay(long ticks)
>  {
>  	schedule_timeout_uninterruptible(ticks);
>  }
>  
> -static inline void nanotime(struct timespec *tvp)
> +static inline void nanotime(struct inode_time *tvp)
>  {
>  	*tvp = CURRENT_TIME;
>  }
> diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
> index a6115fe..16d5392 100644
> --- a/fs/xfs/xfs_inode.c
> +++ b/fs/xfs/xfs_inode.c
> @@ -654,7 +654,7 @@ xfs_ialloc(
>  	xfs_inode_t	*ip;
>  	uint		flags;
>  	int		error;
> -	timespec_t	tv;
> +	struct inode_time tv;
>  
>  	/*
>  	 * Call the space management code to pick
> diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
> index 205613a..092ee7c 100644
> --- a/fs/xfs/xfs_iops.c
> +++ b/fs/xfs/xfs_iops.c
> @@ -956,7 +956,7 @@ xfs_vn_setattr(
>  STATIC int
>  xfs_vn_update_time(
>  	struct inode		*inode,
> -	struct timespec		*now,
> +	struct inode_time	*now,
>  	int			flags)
>  {
>  	struct xfs_inode	*ip = XFS_I(inode);
> diff --git a/fs/xfs/xfs_trans_inode.c b/fs/xfs/xfs_trans_inode.c
> index 50c3f56..bae2520 100644
> --- a/fs/xfs/xfs_trans_inode.c
> +++ b/fs/xfs/xfs_trans_inode.c
> @@ -70,7 +70,7 @@ xfs_trans_ichgtime(
>  	int			flags)
>  {
>  	struct inode		*inode = VFS_I(ip);
> -	timespec_t		tv;
> +	struct inode_time	tv;
>  
>  	ASSERT(tp);
>  	ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
> @@ -78,13 +78,13 @@ xfs_trans_ichgtime(
>  	tv = current_fs_time(inode->i_sb);
>  
>  	if ((flags & XFS_ICHGTIME_MOD) &&
> -	    !timespec_equal(&inode->i_mtime, &tv)) {
> +	    !inode_time_equal(&inode->i_mtime, &tv)) {
>  		inode->i_mtime = tv;
>  		ip->i_d.di_mtime.t_sec = tv.tv_sec;
>  		ip->i_d.di_mtime.t_nsec = tv.tv_nsec;
>  	}

The problem I see here is that the code is now potentially stuffing
a variable that is larger than 32 bits into on on-disk structure
that is only 32 bits in size.  You can't just change the in-memory
representation of inode timestamps and expect the problem to be
fixed - this just pushes the problem down a layer without any
intrastructure allowing filesystems to handle storage of the new
timestamp format sanely.

IOWs, the filesystem has to be able to reject any attempt to set a
timestamp that is can't represent on disk otherwise Bad Stuff will
happen, and filesystems have to be able to specify in their on
disk format what timestamp encoding is being used. The solution will
be different for every filesystem that needs to support time beyond
2038.

Hence I think you are going to need superblock flags and/or
variables to indicate the epoch range the fielsystem can support.
Then the fileystems need conversion functions from whatever the
internal VFS timestamp representation is to whatever their on-disk
format is, and only then can we switch the VFS to using a new
timestamp format.

At that point, filesystem developers can make the changes they need
to the on-disk format to support timestamps beyond 2038, and all
they need to do at the VFS layer is set the "supported range" fields
appropriately in the VFS superblock...

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com

  reply index

Thread overview: 124+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-05-30 20:01 [RFC 00/32] making inode time stamps y2038 ready Arnd Bergmann
2014-05-30 20:01 ` [RFC 01/32] fs: introduce new 'struct inode_time' Arnd Bergmann
2014-05-31  7:56   ` Geert Uytterhoeven
2014-05-31  8:39     ` Andreas Schwab
2014-05-31 13:19       ` Geert Uytterhoeven
2014-05-31 13:46         ` Andreas Schwab
2014-05-31 14:54       ` Arnd Bergmann
2014-05-31 16:15         ` Geert Uytterhoeven
2014-05-31  9:03   ` H. Peter Anvin
2014-05-31 14:53     ` Arnd Bergmann
2014-05-31 14:55       ` H. Peter Anvin
2014-05-30 20:01 ` [RFC 02/32] uapi: add struct __kernel_timespec{32,64} Arnd Bergmann
2014-05-30 20:18   ` H. Peter Anvin
2014-05-31 15:09     ` Arnd Bergmann
2014-05-30 20:01 ` [RFC 03/32] fs: introduce sys_utimens64at Arnd Bergmann
2014-05-31  9:22   ` Andreas Schwab
2014-05-31 14:55     ` Arnd Bergmann
2014-05-30 20:01 ` [RFC 04/32] fs: introduce sys_newfstat64/sys_newfstatat64 Arnd Bergmann
2014-05-30 20:01 ` [RFC 05/32] arch: hook up new stat and utimes syscalls Arnd Bergmann
2014-05-30 20:01 ` [RFC 06/32] isofs: fix timestamps beyond 2027 Arnd Bergmann
2014-05-31  7:59   ` Geert Uytterhoeven
2014-05-31  8:47     ` H. Peter Anvin
2014-05-30 20:01 ` [RFC 07/32] fs/nfs: convert to struct inode_time Arnd Bergmann
2014-05-30 20:01 ` [RFC 08/32] fs/ceph: convert to 'struct inode_time' Arnd Bergmann
2014-05-30 20:01 ` [RFC 09/32] fs/pstore: convert to struct inode_time Arnd Bergmann
2014-05-30 21:14   ` Kees Cook
2014-05-30 20:01 ` [RFC 10/32] fs/coda: " Arnd Bergmann
2014-05-30 20:01 ` [RFC 11/32] xfs: " Arnd Bergmann
2014-05-31  0:37   ` Dave Chinner [this message]
2014-05-31  0:41     ` H. Peter Anvin
2014-05-31  1:14       ` Dave Chinner
2014-05-31  1:22         ` H. Peter Anvin
2014-05-31  5:54           ` Dave Chinner
2014-05-31  8:41             ` H. Peter Anvin
2014-05-31 15:46               ` Nicolas Pitre
2014-06-01 19:56                 ` Arnd Bergmann
2014-06-01 20:26                   ` H. Peter Anvin
2014-06-02 11:02                     ` Arnd Bergmann
2014-06-02  1:36                   ` Nicolas Pitre
2014-06-02  2:22                     ` Dave Chinner
2014-06-02  7:09                       ` Geert Uytterhoeven
2014-06-02 10:56                     ` Arnd Bergmann
2014-06-02 11:57                       ` Theodore Ts'o
2014-06-02 12:38                         ` Arnd Bergmann
2014-06-02 13:15                           ` Theodore Ts'o
2014-06-02 12:52                         ` Arnd Bergmann
2014-06-02 13:07                           ` Theodore Ts'o
2014-06-02 15:01                             ` Arnd Bergmann
2014-06-02 14:52                         ` H. Peter Anvin
2014-06-02 15:04                       ` Chuck Lever
2014-06-02 15:31                         ` Theodore Ts'o
2014-06-02 17:12                           ` H. Peter Anvin
2014-06-02 18:50                             ` Arnd Bergmann
2014-06-02 22:29                             ` Theodore Ts'o
2014-06-02 22:32                               ` H. Peter Anvin
2014-06-02 23:32                                 ` Theodore Ts'o
2014-06-02 23:33                                   ` H. Peter Anvin
2014-06-03 13:09                                   ` Roger Willcocks
2014-06-02 18:52                         ` Arnd Bergmann
2014-06-02 18:58                         ` Roger Willcocks
2014-06-02 19:04                           ` Chuck Lever
2014-06-02 19:10                             ` Arnd Bergmann
2014-06-01  0:39               ` Dave Chinner
2014-06-02 14:00             ` Joseph S. Myers
2014-05-31 15:37         ` Arnd Bergmann
2014-06-01  0:24           ` Dave Chinner
2014-06-02  0:28             ` Dave Chinner
2014-06-02 11:35               ` Roger Willcocks
2014-06-02 11:43               ` Arnd Bergmann
2014-06-03  0:32                 ` Dave Chinner
2014-06-03  7:33                   ` Arnd Bergmann
2014-06-03  8:41                     ` Dave Chinner
2014-06-03  9:16                       ` Arnd Bergmann
2014-05-30 20:01 ` [RFC 12/32] btrfs: " Arnd Bergmann
2014-05-30 20:01 ` [RFC 13/32] ext3: " Arnd Bergmann
2014-05-31  9:10   ` H. Peter Anvin
2014-05-31 14:32     ` Arnd Bergmann
2014-05-30 20:01 ` [RFC 14/32] ext4: " Arnd Bergmann
2014-05-30 20:01 ` [RFC 15/32] cifs: " Arnd Bergmann
2014-05-30 20:01 ` [RFC 16/32] ntfs: " Arnd Bergmann
2014-05-30 20:01 ` [RFC 17/32] ubifs: " Arnd Bergmann
2014-06-02  7:54   ` Artem Bityutskiy
2014-05-30 20:01 ` [RFC 18/32] ocfs2: " Arnd Bergmann
2014-05-30 20:01 ` [RFC 19/32] fs/fat: " Arnd Bergmann
2014-05-30 20:01 ` [RFC 20/32] afs: " Arnd Bergmann
2014-05-30 20:01 ` [RFC 21/32] udf: " Arnd Bergmann
2014-05-30 20:01 ` [RFC 22/32] fs: convert simple fs to inode_time Arnd Bergmann
2014-05-30 23:06   ` Greg Kroah-Hartman
2014-05-30 20:01 ` [RFC 23/32] logfs: convert to struct inode_time Arnd Bergmann
2014-05-30 20:01 ` [RFC 24/32] hfs, hfsplus: " Arnd Bergmann
2014-05-31 14:23   ` Vyacheslav Dubeyko
2014-05-30 20:01 ` [RFC 25/32] gfs2: " Arnd Bergmann
2014-06-02  9:52   ` Steven Whitehouse
2014-05-30 20:01 ` [RFC 26/32] reiserfs: " Arnd Bergmann
2014-05-30 20:01 ` [RFC 27/32] jffs2: " Arnd Bergmann
2014-05-30 20:01 ` [RFC 28/32] adfs: " Arnd Bergmann
2014-05-30 20:01 ` [RFC 29/32] f2fs: " Arnd Bergmann
2014-05-30 20:01 ` [RFC 30/32] fuse: " Arnd Bergmann
2014-05-30 20:01 ` [RFC 31/32] scsi: fnic: use current_kernel_time() for timestamp Arnd Bergmann
2014-05-30 20:01 ` [RFC 32/32] fs: use new inode_time definition unconditionally Arnd Bergmann
2014-05-31 14:30 ` [RFC 00/32] making inode time stamps y2038 ready Vyacheslav Dubeyko
2014-06-03 12:21   ` Arnd Bergmann
2014-05-31 14:51 ` Richard Cochran
2014-05-31 15:23   ` Arnd Bergmann
2014-05-31 18:22     ` Richard Cochran
2014-05-31 19:34       ` H. Peter Anvin
2014-06-01  4:46         ` Richard Cochran
2014-06-01  4:44     ` Richard Cochran
2014-06-02 13:52 ` Joseph S. Myers
2014-06-02 19:19   ` Arnd Bergmann
2014-06-02 19:26     ` H. Peter Anvin
2014-06-02 19:55       ` Arnd Bergmann
2014-06-02 21:57         ` H. Peter Anvin
2014-06-03 14:22           ` Arnd Bergmann
2014-06-03 14:33             ` Joseph S. Myers
2014-06-03 14:37               ` Arnd Bergmann
2014-06-03 21:38             ` Dave Chinner
2014-06-04 15:03               ` Arnd Bergmann
2014-06-04 17:30                 ` Nicolas Pitre
2014-06-04 19:24                   ` Arnd Bergmann
2014-06-05  0:10                     ` H. Peter Anvin
2014-06-10  9:54                       ` Arnd Bergmann
2014-06-02 21:02     ` Joseph S. Myers
2014-06-04 15:05       ` Arnd Bergmann

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