[PATCH] md: Assorted little md fixes

- version-1 superblock
  + The default_bitmap_offset is in sectors, not bytes.
  + the 'size' field in the superblock is in sectors, not KB
- raid0_run should return a negative number on error, not '1'
- raid10_read_balance should not return a valid 'disk' number if
     ->rdev turned out to be NULL
- kmem_cache_destroy doesn't like being passed a NULL.

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

drivers/md/raid5.c

@@ -350,7 +350,8 @@ static void shrink_stripes(raid5_conf_t *conf)
 	while (drop_one_stripe(conf))
 		;
 
-	kmem_cache_destroy(conf->slab_cache);
+	if (conf->slab_cache)
+		kmem_cache_destroy(conf->slab_cache);
 	conf->slab_cache = NULL;
 }