xfs: ensure correct timestamp updates from truncate

The VFS doesn't set the proper ATTR_CTIME and ATTR_MTIME values for
truncate, so filesystems have to manually add them.  The
introduction of xfs_setattr_time accidentally broke this special
case an caused a regression in generic/313.  Fix this by removing
the local mask variable in xfs_setattr_size so that we only have a
single place to keep the attribute information.

cc: <stable@vger.kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Jie Liu <jeff.liu@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

fs/xfs/xfs_iops.c

@@ -705,7 +705,6 @@ xfs_setattr_size(
 {
 	struct xfs_mount	*mp = ip->i_mount;
 	struct inode		*inode = VFS_I(ip);
-	int			mask = iattr->ia_valid;
 	xfs_off_t		oldsize, newsize;
 	struct xfs_trans	*tp;
 	int			error;
@@ -726,7 +725,7 @@ xfs_setattr_size(
 
 	ASSERT(xfs_isilocked(ip, XFS_IOLOCK_EXCL));
 	ASSERT(S_ISREG(ip->i_d.di_mode));
-	ASSERT((mask & (ATTR_UID|ATTR_GID|ATTR_ATIME|ATTR_ATIME_SET|
+	ASSERT((iattr->ia_valid & (ATTR_UID|ATTR_GID|ATTR_ATIME|ATTR_ATIME_SET|
 		ATTR_MTIME_SET|ATTR_KILL_PRIV|ATTR_TIMES_SET)) == 0);
 
 	oldsize = inode->i_size;
@@ -736,7 +735,7 @@ xfs_setattr_size(
 	 * Short circuit the truncate case for zero length files.
 	 */
 	if (newsize == 0 && oldsize == 0 && ip->i_d.di_nextents == 0) {
-		if (!(mask & (ATTR_CTIME|ATTR_MTIME)))
+		if (!(iattr->ia_valid & (ATTR_CTIME|ATTR_MTIME)))
 			return 0;
 
 		/*
@@ -824,10 +823,11 @@ xfs_setattr_size(
 	 * these flags set.  For all other operations the VFS set these flags
 	 * explicitly if it wants a timestamp update.
 	 */
-	if (newsize != oldsize && (!(mask & (ATTR_CTIME | ATTR_MTIME)))) {
+	if (newsize != oldsize &&
+	    !(iattr->ia_valid & (ATTR_CTIME | ATTR_MTIME))) {
 		iattr->ia_ctime = iattr->ia_mtime =
 			current_fs_time(inode->i_sb);
-		mask |= ATTR_CTIME | ATTR_MTIME;
+		iattr->ia_valid |= ATTR_CTIME | ATTR_MTIME;
 	}
 
 	/*
@@ -863,9 +863,9 @@ xfs_setattr_size(
 		xfs_inode_clear_eofblocks_tag(ip);
 	}
 
-	if (mask & ATTR_MODE)
+	if (iattr->ia_valid & ATTR_MODE)
 		xfs_setattr_mode(ip, iattr);
-	if (mask & (ATTR_ATIME|ATTR_CTIME|ATTR_MTIME))
+	if (iattr->ia_valid & (ATTR_ATIME|ATTR_CTIME|ATTR_MTIME))
 		xfs_setattr_time(ip, iattr);
 
 	xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);