[PATCH] md.c semaphore updates

[Ross Vandegrift <ross@willow.seitz.com>]

Neil,

	I read through the md code this afternoon looking for uses of
mddev->disks, and protected each use with reconfig_sem.  These three are
the only three I saw.

Ross Vandegrift
ross@willow.seitz.com
--- md.c.orig	Wed Feb 27 16:04:50 2002
+++ md.c	Wed Feb 27 20:42:41 2002
@@ -606,7 +606,9 @@
 			mdidx(mddev), partition_name(rdev->dev),
 				partition_name(same_pdev->dev));
 
+	down(&mddev->reconfig_sem);
 	md_list_add(&rdev->same_set, &mddev->disks);
+	up(&mddev->reconfig_sem);
 	rdev->mddev = mddev;
 	mddev->nb_dev++;
 	printk(KERN_INFO "md: bind<%s,%d>\n", partition_name(rdev->dev), mddev->nb_dev);
@@ -1889,10 +1891,13 @@
 	struct md_list_head *tmp;
 	int err;
 
+	down(&mddev->reconfig_sem);
 	if (mddev->disks.prev == &mddev->disks) {
+		up(&mddev->reconfig_sem);
 		MD_BUG();
 		return;
 	}
+	up(&mddev->reconfig_sem);
 
 	printk(KERN_INFO "md: running: ");
 
@@ -2204,8 +2209,11 @@
 			return -EINVAL;
 		}
 		if (mddev->nb_dev) {
-			mdk_rdev_t *rdev0 = md_list_entry(mddev->disks.next,
+			mdk_rdev_t *rdev0;
+			down(&mddev->reconfig_sem);
+		       	rdev0 = md_list_entry(mddev->disks.next,
 							mdk_rdev_t, same_set);
+			up(&mddev->reconfig_sem);
 			if (!uuid_equal(rdev0, rdev)) {
 				printk(KERN_WARNING "md: %s has different UUID to %s\n",
 				       partition_name(rdev->dev), partition_name(rdev0->dev));