Two questions on scsi_device_{get,put}

[Christoph Hellwig <hch@lst.de>]

I'm trying to forward-port my locking infrastructure for
shost->my_devices to the current scsi tree.  As this list is
acquired from irq context we need these locks to be spinlocks,
but for that to work scsi_device_get/scsi_device_put must not
block.

But after your changes it's using the class r/w semaphore for
synchronisation.  What it this protecting except sdev->access_count?
Also what's the reason we can't do the device_del directly but have
to do it in scsi_device_put?

A final nitpick:  you're losing a module refernece for some failure
pathes of scsi_module_get.