xfs: have xfs_vn_update_time gets its own timestamp

In later patches we're going to drop the "now" parameter from the
update_time operation. Prepare XFS for this by reworking how it fetches
timestamps and sets them in the inode. Ensure that we update the ctime
even if only S_MTIME is set.
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Acked-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Message-Id: <20230807-mgctime-v7-7-d1dec143a704@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>

fs/xfs/xfs_iops.c

@@ -1029,7 +1029,7 @@ xfs_vn_setattr(
 STATIC int
 xfs_vn_update_time(
 	struct inode		*inode,
-	struct timespec64	*now,
+	struct timespec64	*time,
 	int			flags)
 {
 	struct xfs_inode	*ip = XFS_I(inode);
@@ -1037,6 +1037,7 @@ xfs_vn_update_time(
 	int			log_flags = XFS_ILOG_TIMESTAMP;
 	struct xfs_trans	*tp;
 	int			error;
+	struct timespec64	now;
 
 	trace_xfs_update_time(ip);
 
@@ -1056,12 +1057,15 @@ xfs_vn_update_time(
 		return error;
 
 	xfs_ilock(ip, XFS_ILOCK_EXCL);
-	if (flags & S_CTIME)
-		inode_set_ctime_to_ts(inode, *now);
+	if (flags & (S_CTIME|S_MTIME))
+		now = inode_set_ctime_current(inode);
+	else
+		now = current_time(inode);
+
 	if (flags & S_MTIME)
-		inode->i_mtime = *now;
+		inode->i_mtime = now;
 	if (flags & S_ATIME)
-		inode->i_atime = *now;
+		inode->i_atime = now;
 
 	xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);
 	xfs_trans_log_inode(tp, ip, log_flags);