[SCSI] scsi_host regression: fix scsi host leak

commit 9c7701088a61cc0cf8a6e1c68d1e74e3cc2ee0b7
Author: Dave Young <hidave.darkstar@gmail.com>
Date:   Tue Jan 22 14:01:34 2008 +0800

    scsi: use class iteration api

Isn't a correct replacement for the original hand rolled host
lookup. The problem is that class_find_child would get a reference to
the host's class device which is never released.  Since the host class
device holds a reference to the host gendev, the host can never be
freed.

In 2.6.26 we started using class_find_device, and this function also
gets a reference to the device, so we end up with an extra ref
and the host will not get released.

This patch adds a put_device to balance the class_find_device() get. I
kept the scsi_host_get in scsi_host_lookup, because the target layer
is using scsi_host_lookup and it looks like it needs the SHOST_DEL
check.

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>

drivers/scsi/hosts.c

@@ -456,6 +456,10 @@ static int __scsi_host_match(struct device *dev, void *data)
  *
  * Return value:
  *	A pointer to located Scsi_Host or NULL.
+ *
+ *	The caller must do a scsi_host_put() to drop the reference
+ *	that scsi_host_get() took. The put_device() below dropped
+ *	the reference from class_find_device().
  **/
 struct Scsi_Host *scsi_host_lookup(unsigned short hostnum)
 {
@@ -463,9 +467,10 @@ struct Scsi_Host *scsi_host_lookup(unsigned short hostnum)
 	struct Scsi_Host *shost = ERR_PTR(-ENXIO);
 
 	cdev = class_find_device(&shost_class, &hostnum, __scsi_host_match);
-	if (cdev)
+	if (cdev) {
 		shost = scsi_host_get(class_to_shost(cdev));
-
+		put_device(cdev);
+	}
 	return shost;
 }
 EXPORT_SYMBOL(scsi_host_lookup);