Merge branches 'stable/xen-block.rebase' and 'stable/vmalloc-3.2.rebased' into uek2...

Merge branches 'stable/xen-block.rebase' and 'stable/vmalloc-3.2.rebased' into uek2-merge

* stable/xen-block.rebase:
  xen-blkback: Don't disconnect backend until state switched to XenbusStateClosed.
  block: xen-blkback: use API provided by xenbus module to map rings
  xen-blkback: convert hole punching to discard request on loop devices
  xen/blkback: Move processing of BLKIF_OP_DISCARD from dispatch_rw_block_io
  xen/blk[front|back]: Enhance discard support with secure erasing support.
  xen/blk[front|back]: Squash blkif_request_rw and blkif_request_discard together

* stable/vmalloc-3.2.rebased:
  xen: map foreign pages for shared rings by updating the PTEs directly
  net: xen-netback: use API provided by xenbus module to map rings
  block: xen-blkback: use API provided by xenbus module to map rings
  xen: use generic functions instead of xen_{alloc, free}_vm_area()