[JFFS2] Write buffer offset adjustment for NOR-ECC (Sibley) flash

After choosing new c->nextblock, don't leave the wbuf offset field
occasionally pointing at the start of the next physical eraseblock.
This was causing a BUG() on NOR-ECC (Sibley) flash, where we start
writing after the cleanmarker.

Among other this fix should cover write buffer offset adjustment
after flushing the last page of an eraseblock.

Signed-off-by: Alexander Belyakov <abelyako@googlemail.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
diff --git a/fs/jffs2/nodemgmt.c b/fs/jffs2/nodemgmt.c
index a9bf960..0875b60 100644
--- a/fs/jffs2/nodemgmt.c
+++ b/fs/jffs2/nodemgmt.c
@@ -261,6 +261,10 @@
 
 	jffs2_sum_reset_collected(c->summary); /* reset collected summary */
 
+	/* adjust write buffer offset, else we get a non contiguous write bug */
+	if (!(c->wbuf_ofs % c->sector_size) && !c->wbuf_len)
+		c->wbuf_ofs = 0xffffffff;
+
 	D1(printk(KERN_DEBUG "jffs2_find_nextblock(): new nextblock = 0x%08x\n", c->nextblock->offset));
 
 	return 0;