[PATCH] use bd_claim in the raw driver

Currently if you use the raw driver against /dev/hda1 while it has an
fs mounted, everything gets confused and the kernel locks up or oopses.

Al said to use bd_claim().  This prevents the raw driver from being
able to open the device under these circumstances.

There is value in being able to read the raw device while there's a
filesystem mounted: to poke around at the disk without interacting with
the kernel's caching.  You can still do that, with an O_DIRECT open of
/dev/hda1.

drivers/char/raw.c

@@ -56,9 +56,15 @@ static int raw_open(struct inode *inode, struct file *filp)
 	bdev = raw_devices[minor].binding;
 	err = -ENODEV;
 	if (bdev) {
+		err = bd_claim(bdev, raw_open);
+		if (err)
+			goto out;
 		atomic_inc(&bdev->bd_count);
 		err = blkdev_get(bdev, filp->f_mode, 0, BDEV_RAW);
-		if (!err) {
+		if (err) {
+			bd_release(bdev);
+			goto out;
+		} else {
 			err = set_blocksize(bdev, bdev_hardsect_size(bdev));
 			if (err == 0) {
 				raw_devices[minor].inuse++;
@@ -69,6 +75,7 @@ static int raw_open(struct inode *inode, struct file *filp)
 		}
 	}
 	filp->private_data = bdev;
+out:
 	up(&raw_mutex);
 	return err;
 }
@@ -82,6 +89,7 @@ static int raw_release(struct inode *inode, struct file *filp)
 	bdev = raw_devices[minor].binding;
 	raw_devices[minor].inuse--;
 	up(&raw_mutex);
+	bd_release(bdev);
 	blkdev_put(bdev, BDEV_RAW);
 	return 0;
 }