Issue: When the disks are getting discovered and assigned device
handles by the kernel, a device block followed by an unblock
(due to broadcast primitives) issued by the driver is
interspersed by the kernel changing the state of the device.
Therefore the unblock by the driver results in a no operation
within the kernel API.

To fix this one, the below patch checks the return of the unblock API
and performs a block followed by an unblock to unfreeze the block
layer's I/O queue. Sufficient checks and prints are also added in the
driver to identify this condition caused by the kernel.
Signed-off-by: NSreekanth Reddy <Sreekanth.Reddy@avagotech.com>
Reviewed-by: NJohannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: NJames Bottomley <JBottomley@Odin.com>