[PATCH] md: md/linear oops fix

From: Daniel McNeil <daniel@osdl.org>

This fixes an oops caused by incorrect usage of sector_div()
in which_dev() in md/linear.c.  It was dereferencing an non-existent
hash table entry.

drivers/md/linear.c

@@ -37,7 +37,11 @@ static inline dev_info_t *which_dev(mddev_t *mddev, sector_t sector)
 	linear_conf_t *conf = mddev_to_conf(mddev);
 	sector_t block = sector >> 1;
 
-	hash = conf->hash_table + sector_div(block, conf->smallest->size);
+	/*
+	 * sector_div(a,b) returns the remainer and sets a to a/b
+	 */
+	(void)sector_div(block, conf->smallest->size);
+	hash = conf->hash_table + block;
 
 	if ((sector>>1) >= (hash->dev0->size + hash->dev0->offset))
 		return hash->dev1;