Adds a module parameter to control raid5's internal cache size.

Index: linux-2.6.9/drivers/md/raid5.c
===================================================================
--- linux-2.6.9.orig/drivers/md/raid5.c	2006-05-21 17:57:25.000000000 +0400
+++ linux-2.6.9/drivers/md/raid5.c	2006-05-22 00:01:30.000000000 +0400
@@ -28,7 +28,8 @@
  * Stripe cache
  */
 
-#define NR_STRIPES		256
+static int raid5_nr_stripes = 256 * 8;
+
 #define STRIPE_SIZE		PAGE_SIZE
 #define STRIPE_SHIFT		(PAGE_SHIFT - 9)
 #define STRIPE_SECTORS		(STRIPE_SIZE>>9)
@@ -92,7 +93,7 @@ static inline void __release_stripe(raid
 			list_add_tail(&sh->lru, &conf->inactive_list);
 			atomic_dec(&conf->active_stripes);
 			if (!conf->inactive_blocked ||
-			    atomic_read(&conf->active_stripes) < (NR_STRIPES*3/4))
+			    atomic_read(&conf->active_stripes) < (conf->max_nr_stripes*3/4))
 				wake_up(&conf->wait_for_stripe);
 		}
 	}
@@ -255,7 +256,7 @@ static struct stripe_head *get_active_st
 				conf->inactive_blocked = 1;
 				wait_event_lock_irq(conf->wait_for_stripe,
 						    !list_empty(&conf->inactive_list) &&
-						    (atomic_read(&conf->active_stripes) < (NR_STRIPES *3/4)
+						    (atomic_read(&conf->active_stripes) < (conf->max_nr_stripes *3/4)
 						     || !conf->inactive_blocked),
 						    conf->device_lock,
 						    unplug_slaves(conf->mddev);
@@ -1637,7 +1638,7 @@ static int run (mddev_t *mddev)
 	conf->chunk_size = mddev->chunk_size;
 	conf->level = mddev->level;
 	conf->algorithm = mddev->layout;
-	conf->max_nr_stripes = NR_STRIPES;
+	conf->max_nr_stripes = raid5_nr_stripes;
 
 	/* device size must be a multiple of chunk size */
 	mddev->size &= ~(mddev->chunk_size/1024 -1);
@@ -1957,5 +1958,6 @@ static void raid5_exit (void)
 
 module_init(raid5_init);
 module_exit(raid5_exit);
+module_param(raid5_nr_stripes, int, 0644);
 MODULE_LICENSE("GPL");
 MODULE_ALIAS("md-personality-4"); /* RAID5 */