This patch was merged between 2.6.0-test3 and -test4. It breaks EVMS on many
systems by not allowing Device-Mapper to activate DM devices on top of disks
that also contain mounted partitions.

There are three solutions to this problem.

1. Switch to using EVMS for *all* your volumes and partitions. This is, of
   course, the preferred solution, but also requires some extra work on your
   part to convert to mounting your root filesystem using an EVMS volume.

2. Tell EVMS to exclude any disks that contain partitions that you are going
   to mount through the kernel-provided-partitions. You can do this by adding
   an entry to the "exclude" line in your /etc/evms.conf file.

3. Apply this patch, which will revert the change that disallows EVMS to use
   the disk at the same time the kernel-partitions are.

   cd /usr/src/linux-2.6.0-test5
   patch -p1 < bd_claim.patch


### Comments for ChangeSet

Current devices can be 'claimed' by filesystems (when mounting) or
md/raid (when being included in an array) or 'raw' or ....
This stop concurrent access by these systems.

However it is still possible for one system to claim the whole device
and a second system to claim one partition, which is not good.

With this patch, when a partition is claimed, the whole device is 
claimed for partitioning.  So you cannot have a partition and the
whole devices claimed at the same time (except if the whole device
is claimed for partitioning).

 ----------- Diffstat output ------------
 ./fs/block_dev.c |   32 ++++++++++++++++++++++++++++----
 1 files changed, 28 insertions(+), 4 deletions(-)

diff a/fs/block_dev.c b/fs/block_dev.c
--- a/fs/block_dev.c	2003-08-11 09:01:38.000000000 +1000
+++ b/fs/block_dev.c	2003-08-11 09:01:38.000000000 +1000
@@ -411,34 +411,12 @@ void bd_forget(struct inode *inode)
 
 int bd_claim(struct block_device *bdev, void *holder)
 {
+	int res = -EBUSY;
-	int res;
 	spin_lock(&bdev_lock);
+	if (!bdev->bd_holder || bdev->bd_holder == holder) {
+		bdev->bd_holder = holder;
-
-	/* first decide result */
-	if (bdev->bd_holder == holder)
-		res = 0;	 /* already a holder */
-	else if (bdev->bd_holder != NULL)
-		res = -EBUSY; 	 /* held by someone else */
-	else if (bdev->bd_contains == bdev)
-		res = 0;  	 /* is a whole device which isn't held */
-
-	else if (bdev->bd_contains->bd_holder == bd_claim)
-		res = 0; 	 /* is a partition of a device that is being partitioned */
-	else if (bdev->bd_contains->bd_holder != NULL)
-		res = -EBUSY;	 /* is a partition of a held device */
-	else
-		res = 0;	 /* is a partition of an un-held device */
-
-	/* now impose change */
-	if (res==0) {
-		/* note that for a whole device bd_holders
-		 * will be incremented twice, and bd_holder will
-		 * be set to bd_claim before being set to holder
-		 */
-		bdev->bd_contains->bd_holders ++;
-		bdev->bd_contains->bd_holder = bd_claim;
 		bdev->bd_holders++;
+		res = 0;
-		bdev->bd_holder = holder;
 	}
 	spin_unlock(&bdev_lock);
 	return res;
@@ -447,8 +425,6 @@ int bd_claim(struct block_device *bdev, 
 void bd_release(struct block_device *bdev)
 {
 	spin_lock(&bdev_lock);
-	if (!--bdev->bd_contains->bd_holders)
-		bdev->bd_contains->bd_holder = NULL;
 	if (!--bdev->bd_holders)
 		bdev->bd_holder = NULL;
 	spin_unlock(&bdev_lock);