linux/fs/ext2
Markus Rechberger 4d7bf11d64 ext2/3/4: fix file date underflow on ext2 3 filesystems on 64 bit systems
Taken from http://bugzilla.kernel.org/show_bug.cgi?id=5079

signed long ranges from -2.147.483.648 to 2.147.483.647 on x86 32bit

10000011110110100100111110111101 .. -2,082,844,739
10000011110110100100111110111101 ..  2,212,122,557 <- this currently gets
stored on the disk but when converting it to a 64bit signed long value it loses
its sign and becomes positive.

Cc: Andreas Dilger <adilger@dilger.ca>
Cc: <linux-ext4@vger.kernel.org>

Andreas says:

This patch is now treating timestamps with the high bit set as negative
times (before Jan 1, 1970).  This means we lose 1/2 of the possible range
of timestamps (lopping off 68 years before unix timestamp overflow -
now only 30 years away :-) to handle the extremely rare case of setting
timestamps into the distant past.

If we are only interested in fixing the underflow case, we could just
limit the values to 0 instead of storing negative values.  At worst this
will skew the timestamp by a few hours for timezones in the far east
(files would still show Jan 1, 1970 in "ls -l" output).

That said, it seems 32-bit systems (mine at least) allow files to be set
into the past (01/01/1907 works fine) so it seems this patch is bringing
the x86_64 behaviour into sync with other kernels.

On the plus side, we have a patch that is ready to add nanosecond timestamps
to ext3 and as an added bonus adds 2 high bits to the on-disk timestamp so
this extends the maximum date to 2242.

Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-05-08 11:14:58 -07:00
..
Makefile [PATCH] Make EXT2_DEBUG work again 2006-06-25 10:01:12 -07:00
acl.c [PATCH] fs: Removing useless casts 2006-09-27 08:26:10 -07:00
acl.h [PATCH] remove <linux/xattr_acl.h> 2005-06-23 09:45:33 -07:00
balloc.c [PATCH] ext[234]: update documentation 2007-02-20 17:10:14 -08:00
dir.c mm: make read_cache_page synchronous 2007-05-07 12:12:51 -07:00
ext2.h [PATCH] mark struct inode_operations const 1 2007-02-12 09:48:46 -08:00
file.c [PATCH] mark struct inode_operations const 1 2007-02-12 09:48:46 -08:00
fsync.c [PATCH] ext2: cleanup: put_page and comment fix 2006-06-25 10:01:25 -07:00
ialloc.c [PATCH] inode-diet: Eliminate i_blksize from the inode structure 2006-09-27 08:26:18 -07:00
inode.c ext2/3/4: fix file date underflow on ext2 3 filesystems on 64 bit systems 2007-05-08 11:14:58 -07:00
ioctl.c [PATCH] ext2: change uses of f_{dentry, vfsmnt} to use f_path 2006-12-08 08:28:41 -08:00
namei.c [PATCH] mark struct inode_operations const 1 2007-02-12 09:48:46 -08:00
super.c slab allocators: Remove SLAB_DEBUG_INITIAL flag 2007-05-07 12:12:57 -07:00
symlink.c [PATCH] mark struct inode_operations const 1 2007-02-12 09:48:46 -08:00
xattr.c [PATCH] Remove superfluous lock_super() in extN xattr code 2006-12-07 08:39:32 -08:00
xattr.h Remove obsolete #include <linux/config.h> 2006-06-30 19:25:36 +02:00
xattr_security.c [PATCH] ext2: Enable atomic inode security labeling 2005-09-09 13:57:27 -07:00
xattr_trusted.c [PATCH] capable/capability.h (fs/) 2006-01-11 18:42:13 -08:00
xattr_user.c [PATCH] remove ext2 xattr permission checks 2006-01-10 08:01:30 -08:00
xip.c [PATCH] fix xip sparse file handling in ext2 2005-07-27 16:25:53 -07:00
xip.h [PATCH] xip: ext2: execute in place 2005-06-24 00:06:41 -07:00