ocfs2: ignore NULL vfsmnt in ocfs2_should_update_atime()

This can come from NFSD.
Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>

fs/ocfs2/file.c

@@ -149,6 +149,17 @@ int ocfs2_should_update_atime(struct inode *inode,
 	    ((inode->i_sb->s_flags & MS_NODIRATIME) && S_ISDIR(inode->i_mode)))
 		return 0;
 
+	/*
+	 * We can be called with no vfsmnt structure - NFSD will
+	 * sometimes do this.
+	 *
+	 * Note that our action here is different than touch_atime() -
+	 * if we can't tell whether this is a noatime mount, then we
+	 * don't know whether to trust the value of s_atime_quantum.
+	 */
+	if (vfsmnt == NULL)
+		return 0;
+
 	if ((vfsmnt->mnt_flags & MNT_NOATIME) ||
 	    ((vfsmnt->mnt_flags & MNT_NODIRATIME) && S_ISDIR(inode->i_mode)))
 		return 0;