I think you need this patch otherwise you will be passing uninitialised
data from the stack to GNTTABOP_unmap_grant_ref in fast_flush_area.

Also, I think the memset of the pending_grant_handles array should
happen before you start using them so I moved it to before
blkif_xenbus_init.  I'm not sure if this is necessary or it might
possibly have to go even earlier.

Signed off by Harry Butterworth butterwo@uk.ibm.com.