[PATCH 09/26] xfs: explicitly define inode timestamp range

Darrick J. Wong
2020-10-26T23:35:15Z

From: Darrick J. Wong <darrick.wong@oracle.com>

Source kernel commit: 876fdc7c4f366a709ac272ef3336ae7dce58f2af

Formally define the inode timestamp ranges that existing filesystems
support, and switch the vfs timetamp ranges to use it.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Allison Collins <allison.henderson@oracle.com>
Reviewed-by: Gao Xiang <hsiangkao@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
include/xfs_fs_compat.h | 4 ++++
libxfs/xfs_format.h | 22 ++++++++++++++++++++++
2 files changed, 26 insertions(+)

diff --git a/include/xfs_fs_compat.h b/include/xfs_fs_compat.h
index d0ffc9775875..0077f00cb949 100644
--- a/include/xfs_fs_compat.h
+++ b/include/xfs_fs_compat.h
@@ -93,4 +93,8 @@ struct timespec64 {
long tv_nsec; /* nanoseconds */
};

+#define U32_MAX ((uint32_t)~0U)
+#define S32_MAX ((int32_t)(U32_MAX >> 1))
+#define S32_MIN ((int32_t)(-S32_MAX - 1))
+
#endif /* __XFS_FS_COMPAT_H__ */
diff --git a/libxfs/xfs_format.h b/libxfs/xfs_format.h
index 5a183b6658e6..4a106b6713ad 100644
--- a/libxfs/xfs_format.h
+++ b/libxfs/xfs_format.h
@@ -848,11 +848,33 @@ struct xfs_agfl {
ASSERT(xfs_daddr_to_agno(mp, d) == \
xfs_daddr_to_agno(mp, (d) + (len) - 1)))

+/*
+ * XFS Timestamps
+ * ==============
+ *
+ * Traditional ondisk inode timestamps consist of signed 32-bit counters for
+ * seconds and nanoseconds; time zero is the Unix epoch, Jan 1 00:00:00 UTC
+ * 1970, which means that the timestamp epoch is the same as the Unix epoch.
+ * Therefore, the ondisk min and max defined here can be used directly to
+ * constrain the incore timestamps on a Unix system.
+ */
typedef struct xfs_timestamp {
__be32 t_sec; /* timestamp seconds */
__be32 t_nsec; /* timestamp nanoseconds */
} xfs_timestamp_t;

+/*
+ * Smallest possible ondisk seconds value with traditional timestamps. This
+ * corresponds exactly with the incore timestamp Dec 13 20:45:52 UTC 1901.
+ */
+#define XFS_LEGACY_TIME_MIN ((int64_t)S32_MIN)
+
+/*
+ * Largest possible ondisk seconds value with traditional timestamps. This
+ * corresponds exactly with the incore timestamp Jan 19 03:14:07 UTC 2038.
+ */
+#define XFS_LEGACY_TIME_MAX ((int64_t)S32_MAX)
+
/*
* On-disk inode structure.
*