The following patches were made over Linus tree and also apply over mst tree's vhost branch. The patches fix an issue where management operations like LUN mapping/unmapping and device addition hang for 30 seconds or up to N minutes depending on the device. The problem is that we use a global mutex to protect the list of tpgs but we hold that mutex during those management operations. So if you are just trying to add another device, it will have to wait on another device if we are in the middle of clearing it's endpoint and it's waiting on hung IO. This patchset fixes up the ordering of how we flush IO and release refcounts so we don't need to always hold the mutex.
