From 18e3b8c234fac67c6c96e9ff34f0ab4598220fa1 Mon Sep 17 00:00:00 2001
From: "Darrick J. Wong" <darrick.wong@oracle.com>
Date: Tue, 10 Nov 2020 15:11:09 -0500
Subject: [PATCH] xfs: explicitly define inode timestamp range

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: Eric Sandeen <sandeen@sandeen.net>
---

NOTE: we hvae no xfs_compat.h so S32_MAX etc went in xfs_fs.h

diff --git a/libxfs/xfs_format.h b/libxfs/xfs_format.h
index 7f7b03a..5712aa0 100644
--- a/libxfs/xfs_format.h
+++ b/libxfs/xfs_format.h
@@ -839,11 +839,33 @@ typedef 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.
  *
diff --git a/libxfs/xfs_fs.h b/libxfs/xfs_fs.h
index fbc9031..4fa9852 100644
--- a/libxfs/xfs_fs.h
+++ b/libxfs/xfs_fs.h
@@ -694,6 +694,10 @@ 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))
+
 #ifndef HAVE_BBMACROS
 /*
  * Block I/O parameterization.	A basic block (BB) is the lowest size of