xfsdocs: fix inode timestamps lower limit value
In kernel source tree 'fs/xfs/libxfs/xfs_format.h', there defined inode
timestamps as 'xfs_legacy_timestamp' if the 'bigtime' feature disabled,
and also defined the min and max time constants 'XFS_LEGACY_TIME_MIN'
and 'XFS_LEGACY_TIME_MAX' as below:
/* fs/xfs/libxfs/xfs_format.h begin */
struct xfs_legacy_timestamp {
__be32 t_sec; /* timestamp seconds */
__be32 t_nsec; /* timestamp nanoseconds */
};
#define XFS_LEGACY_TIME_MIN ((int64_t)S32_MIN)
#define XFS_LEGACY_TIME_MAX ((int64_t)S32_MAX)
/* fs/xfs/libxfs/xfs_format.h end */
/* include/linux/limits.h begin */
#define U32_MAX ((u32)~0U)
#define S32_MAX ((s32)(U32_MAX >> 1))
#define S32_MIN ((s32)(-S32_MAX - 1))
/* include/linux/limits.h end */
When the 't_sec' and 't_nsec' are 0, the time value it represents is
1970-01-01 00:00:00 UTC, the 'XFS_LEGACY_TIME_MIN', that is -(2^31),
represents the min second offset relative to the
1970-01-01 00:00:00 UTC, it can be converted to human-friendly time
value by 'date' command:
/* command begin */
[root@~]# date --utc -d '@0' +'%Y-%m-%d %H:%M:%S'
1970-01-01 00:00:00
[root@~]# date --utc -d "@`echo '-(2^31)'|bc`" +'%Y-%m-%d %H:%M:%S'
1901-12-13 20:45:52
[root@~]#
/* command end */
That is, the min time value is 1901-12-13 20:45:52 UTC, but the
'design/XFS_Filesystem_Structure/timestamps.asciidoc' write the min
time value as 'The smalle st date this format can represent is
20:45:52 UTC on December 31st', there should be a typo, and this patch
correct 2 places of wrong min time value, from '31st' to '13st'.
Signed-off-by: Xiaole He <hexiaole@kylinos.cn>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
diff --git a/design/XFS_Filesystem_Structure/timestamps.asciidoc b/design/XFS_Filesystem_Structure/timestamps.asciidoc
index 08baa1e..56d4dc9 100644
--- a/design/XFS_Filesystem_Structure/timestamps.asciidoc
+++ b/design/XFS_Filesystem_Structure/timestamps.asciidoc
@@ -26,13 +26,13 @@
};
----
-The smallest date this format can represent is 20:45:52 UTC on December 31st,
+The smallest date this format can represent is 20:45:52 UTC on December 13st,
1901, and the largest date supported is 03:14:07 UTC on January 19, 2038.
With the introduction of the bigtime feature, the format is changed to
interpret the timestamp as a 64-bit count of nanoseconds since the smallest
date supported by the old encoding. This means that the smallest date
-supported is still 20:45:52 UTC on December 31st, 1901; but now the largest
+supported is still 20:45:52 UTC on December 13st, 1901; but now the largest
date supported is 20:20:24 UTC on July 2nd, 2486.
[[Quota_Timers]]
