[JFFS2] Add support for JFFS2-on-Dataflash devices.

For Dataflash, can_mark_obsolete = false and the NAND write buffering
code (wbuf.c) is used.

Since the DataFlash chip will automatically erase pages when writing,
the cleanmarkers are not needed - so cleanmarker_oob = false and
cleanmarker_size = 0

DataFlash page-sizes are not a power of two (they're multiples of 528
bytes).  The SECTOR_ADDR macro (added in the previous core patch) is
replaced with a (slower) div/mod version if CONFIG_JFFS2_FS_DATAFLASH is
selected.

Signed-off-by: Andrew Victor <andrew@sanpeople.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/fs/jffs2/erase.c b/fs/jffs2/erase.c
index ae858f8..a3c6cc150 100644
--- a/fs/jffs2/erase.c
+++ b/fs/jffs2/erase.c
@@ -7,7 +7,7 @@
  *
  * For licensing information, see the file 'LICENCE' in this directory.
  *
- * $Id: erase.c,v 1.70 2005/02/09 09:09:01 pavlov Exp $
+ * $Id: erase.c,v 1.71 2005/02/09 09:17:40 pavlov Exp $
  *
  */
 
@@ -310,7 +310,7 @@
 	int ret;
 	uint32_t bad_offset;
 
-	if (!jffs2_cleanmarker_oob(c)) {
+	if ((!jffs2_cleanmarker_oob(c)) && (c->cleanmarker_size > 0)) {
 		marker_ref = jffs2_alloc_raw_node_ref();
 		if (!marker_ref) {
 			printk(KERN_WARNING "Failed to allocate raw node ref for clean marker\n");
@@ -351,7 +351,7 @@
 					bad_offset += i;
 					printk(KERN_WARNING "Newly-erased block contained word 0x%lx at offset 0x%08x\n", datum, bad_offset);
 				bad: 
-					if (!jffs2_cleanmarker_oob(c))
+					if ((!jffs2_cleanmarker_oob(c)) && (c->cleanmarker_size > 0))
 						jffs2_free_raw_node_ref(marker_ref);
 					kfree(ebuf);
 				bad2:
@@ -387,6 +387,13 @@
 		jeb->used_size = 0;
 		jeb->dirty_size = 0;
 		jeb->wasted_size = 0;
+	} else if (c->cleanmarker_size == 0) {
+		jeb->first_node = jeb->last_node = NULL;
+
+		jeb->free_size = c->sector_size;
+		jeb->used_size = 0;
+		jeb->dirty_size = 0;
+		jeb->wasted_size = 0;
 	} else {
 		struct kvec vecs[1];
 		struct jffs2_unknown_node marker = {