| Message ID | 1658052271-522-1-git-send-email-hexiaole1994@126.com (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
| Series | [v1] xfs: fix comment for start time value of inode with bigtime enabled | expand |
On Sun, Jul 17, 2022 at 06:04:31PM +0800, Xiaole He wrote: > The 'ctime', 'mtime', and 'atime' for inode is the type of > 'xfs_timestamp_t', which is a 64-bit type: > > /* fs/xfs/libxfs/xfs_format.h begin */ > typedef __be64 xfs_timestamp_t; > /* fs/xfs/libxfs/xfs_format.h end */ > > When the 'bigtime' feature is disabled, this 64-bit type is splitted > into two parts of 32-bit, one part is encoded for seconds since > 1970-01-01 00:00:00 UTC, the other part is encoded for nanoseconds > above the seconds, this two parts are the type of > 'xfs_legacy_timestamp' and the min and max time value of this type are > defined as macros '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 */ > }; > #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 */ > > 'XFS_LEGACY_TIME_MIN' is the min time value of the > 'xfs_legacy_timestamp', that is -(2^31) seconds 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 */ > > When 'bigtime' feature is enabled, this 64-bit type becomes a 64-bit > nanoseconds counter, with the start time value is the min time value of > 'xfs_legacy_timestamp'(start time means the value of 64-bit nanoseconds > counter is 0). We have already caculated the min time value of > 'xfs_legacy_timestamp', that is 1901-12-13 20:45:52 UTC, but the comment > for the start time value of inode with 'bigtime' feature enabled writes > the value is 1901-12-31 20:45:52 UTC: > > /* fs/xfs/libxfs/xfs_format.h begin */ > /* > * XFS Timestamps > * ============== > * When the bigtime feature is enabled, ondisk inode timestamps become an > * unsigned 64-bit nanoseconds counter. This means that the bigtime inode > * timestamp epoch is the start of the classic timestamp range, which is > * Dec 31 20:45:52 UTC 1901. ... > ... > */ > /* fs/xfs/libxfs/xfs_format.h end */ > > That is a typo, and this patch corrects the typo, from 'Dec 31' to > 'Dec 13'. > > Suggested-by: Darrick J. Wong <djwong@kernel.org> > Signed-off-by: Xiaole He <hexiaole@kylinos.cn> Heh, thanks for fixing the typo. Reviewed-by: Darrick J. Wong <djwong@kernel.org> --D > --- > fs/xfs/libxfs/xfs_format.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h > index afdfc81..b55bdfa 100644 > --- a/fs/xfs/libxfs/xfs_format.h > +++ b/fs/xfs/libxfs/xfs_format.h > @@ -704,7 +704,7 @@ struct xfs_agfl { > * When the bigtime feature is enabled, ondisk inode timestamps become an > * unsigned 64-bit nanoseconds counter. This means that the bigtime inode > * timestamp epoch is the start of the classic timestamp range, which is > - * Dec 31 20:45:52 UTC 1901. Because the epochs are not the same, callers > + * Dec 13 20:45:52 UTC 1901. Because the epochs are not the same, callers > * /must/ use the bigtime conversion functions when encoding and decoding raw > * timestamps. > */ > -- > 1.8.3.1 >
diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h index afdfc81..b55bdfa 100644 --- a/fs/xfs/libxfs/xfs_format.h +++ b/fs/xfs/libxfs/xfs_format.h @@ -704,7 +704,7 @@ struct xfs_agfl { * When the bigtime feature is enabled, ondisk inode timestamps become an * unsigned 64-bit nanoseconds counter. This means that the bigtime inode * timestamp epoch is the start of the classic timestamp range, which is - * Dec 31 20:45:52 UTC 1901. Because the epochs are not the same, callers + * Dec 13 20:45:52 UTC 1901. Because the epochs are not the same, callers * /must/ use the bigtime conversion functions when encoding and decoding raw * timestamps. */
The 'ctime', 'mtime', and 'atime' for inode is the type of 'xfs_timestamp_t', which is a 64-bit type: /* fs/xfs/libxfs/xfs_format.h begin */ typedef __be64 xfs_timestamp_t; /* fs/xfs/libxfs/xfs_format.h end */ When the 'bigtime' feature is disabled, this 64-bit type is splitted into two parts of 32-bit, one part is encoded for seconds since 1970-01-01 00:00:00 UTC, the other part is encoded for nanoseconds above the seconds, this two parts are the type of 'xfs_legacy_timestamp' and the min and max time value of this type are defined as macros '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 */ }; #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 */ 'XFS_LEGACY_TIME_MIN' is the min time value of the 'xfs_legacy_timestamp', that is -(2^31) seconds 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 */ When 'bigtime' feature is enabled, this 64-bit type becomes a 64-bit nanoseconds counter, with the start time value is the min time value of 'xfs_legacy_timestamp'(start time means the value of 64-bit nanoseconds counter is 0). We have already caculated the min time value of 'xfs_legacy_timestamp', that is 1901-12-13 20:45:52 UTC, but the comment for the start time value of inode with 'bigtime' feature enabled writes the value is 1901-12-31 20:45:52 UTC: /* fs/xfs/libxfs/xfs_format.h begin */ /* * XFS Timestamps * ============== * When the bigtime feature is enabled, ondisk inode timestamps become an * unsigned 64-bit nanoseconds counter. This means that the bigtime inode * timestamp epoch is the start of the classic timestamp range, which is * Dec 31 20:45:52 UTC 1901. ... ... */ /* fs/xfs/libxfs/xfs_format.h end */ That is a typo, and this patch corrects the typo, from 'Dec 31' to 'Dec 13'. Suggested-by: Darrick J. Wong <djwong@kernel.org> Signed-off-by: Xiaole He <hexiaole@kylinos.cn> --- fs/xfs/libxfs/xfs_format.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)