From: hexiaole <hexiaole@xxxxxxxxxx>
1. Fix description
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':
/* fs/xfs/libxfs/xfs_format.h begin */
struct xfs_legacy_timestamp {
__be32 t_sec; /* timestamp seconds */
__be32 t_nsec; /* timestamp nanoseconds */
};
/* fs/xfs/libxfs/xfs_format.h end */
/* include/linux/limits.h begin */
/* 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@DESKTOP-G0RBR07 sources]# date --utc -d "@`echo '-(2^31)'|bc`" +'%Y-%m-%d %H:%M:%S'
1901-12-13 20:45:52
[root@DESKTOP-G0RBR07 sources]#
/* 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 '3
1st' to '13st'.
2. Question
In the section 'Quota Timers' of 'design/XFS_Filesystem_Structure/timestamps.asciidoc':
/* timestamps.asciidoc begin */
With the introduction of the bigtime feature, the ondisk field now encodes the upper 32 bits of an unsigned 34-bit seconds counter.
...
The smallest quota expiration date is now 00:00:04 UTC on January 1st, 1970;
and the largest is 20:20:24 UTC on July 2nd, 2486.
/* timestamps.asciidoc end */
It seems hard to understand the the relationship among the '32 bits of an unsigned 34-bit seconds counter', '00:00:04 UTC on January 1st, 1970', and 00:00:04 UTC on January 1st, 1970', is it there a typo for '34-bit' and the expected one is '64-bit'?
---
design/XFS_Filesystem_Structure/timestamps.asciidoc | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
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 @@ struct xfs_legacy_timestamp {
};
----
-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]]
--
2.27.0
