xfs: explicitly define inode timestamp range

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>

2 files changed, 24 insertions, 2 deletions

diff --git a/fs/xfs/libxfs/xfs_format.h b/fs/xfs/libxfs/xfs_format.h
index fe129fe16d5f..e57360a8fd16 100644
--- a/fs/xfs/libxfs/xfs_format.h
+++ b/fs/xfs/libxfs/xfs_format.h
@@ -848,12 +848,34 @@ 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.
  *
  * This is just the header or "dinode core", the inode is expanded to fill a
diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
index c7ffcb57b586..b3b0e6154bf2 100644
--- a/fs/xfs/xfs_super.c
+++ b/fs/xfs/xfs_super.c
@@ -1484,8 +1484,8 @@ xfs_fc_fill_super(
 	sb->s_maxbytes = MAX_LFS_FILESIZE;
 	sb->s_max_links = XFS_MAXLINK;
 	sb->s_time_gran = 1;
-	sb->s_time_min = S32_MIN;
-	sb->s_time_max = S32_MAX;
+	sb->s_time_min = XFS_LEGACY_TIME_MIN;
+	sb->s_time_max = XFS_LEGACY_TIME_MAX;
 	sb->s_iflags |= SB_I_CGROUPWB;
 
 	set_posix_acl_flag(sb);