re-add zft_dirty to zftape-ctl.c

@@ -648,6 +648,50 @@
 	TRACE_EXIT 0;
 }
 
+/*  decide when we should lock the module in memory, even when calling
+ *  the release routine. This really is necessary for use with
+ *  kerneld.
+ *
+ *  NOTE: we MUST NOT use zft_write_protected, because this includes
+ *  the file access mode as well which has no meaning with our 
+ *  asynchronous update scheme.
+ *
+ *  Ugly, ugly. We need to look the module if we changed the block size.
+ *  How sad! Need persistent modules storage!
+ *
+ *  NOTE: I don't want to lock the module if the number of dma buffers 
+ *  has been changed. It's enough! Stop the story! Give me persisitent
+ *  module storage! Do it!
+ */
+int zft_dirty(void)
+{
+	if (!ft_formatted || zft_offline) { 
+		/* cannot be dirty if not formatted or offline */
+		return 0;
+	}
+	if (zft_blk_sz != CONFIG_ZFT_DFLT_BLK_SZ) {
+		/* blocksize changed, must lock */
+		return 1;
+	}
+	if (zft_mt_compression != 0) {
+		/* compression mode with /dev/qft, must lock */
+		return 1;
+	}
+	if (!zft_header_read) {
+		/* tape is logical at BOT, no lock */
+		return 0;
+	}
+	if (!zft_tape_at_lbot(&zft_pos)) {
+		/* somewhere inside a volume, lock tape */
+		return 1;
+	}
+	if (zft_volume_table_changed || zft_header_changed) {
+		/* header segments dirty if tape not write protected */
+		return !(ft_write_protected || zft_old_ftape);
+	}
+	return 0;
+}
+
 /*      OPEN routine called by kernel-interface code
  *
  *      NOTE: this is also called by mt_reset() with dev_minor == -1

@@ -47,7 +47,6 @@
 extern void zft_reset_position(zft_position *pos);
 extern int  zft_check_write_access(zft_position *pos);
 extern int  zft_def_idle_state(void);
-extern int  zft_dirty(void);
 
 /*  hooks for the VFS interface 
  */

@@ -790,13 +790,6 @@
 		zft_uninit_mem();
 		going_offline = 0;
 		zft_offline   = 1;
-	} else if (zft_dirty()) {
-		TRACE(ft_t_noise, "Keeping module locked in memory because:\n"
-		      KERN_INFO "header segments need updating: %s\n"
-		      KERN_INFO "tape not at BOT              : %s",
-		      (zft_volume_table_changed || zft_header_changed) 
-		      ? "yes" : "no",
-		      zft_tape_at_lbot(&zft_pos) ? "no" : "yes");
 	} else if (zft_cmpr_lock(0 /* don't load */) == 0) {
 		(*zft_cmpr_ops->reset)(); /* unlock it again */
 	}