On Sun, Jul 17, 2022 at 06:07:28PM +0800, Xiaole He wrote:
> 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@xxxxxxxxxx>
Looks correct, will commit...
Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx>
--D
> ---
> V1 -> V2: Wrap line at 72 column, add Signed-off-by, add one more
> 'date' command for explanation, remove the question section.
>
> 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]]
> --
> 1.8.3.1
>
