Referrals support

Hi Nic,

as discussed here is now the third version of the referrals infrastructure. All the configfs layout changes have been removed as requested.

Main features of this patchset:

- Asynchronous transitioning: I've switched 'transitioning' handling to use a workqueue, that should allow us to simulate asynchronous transitioning modes. IE TCM should now be capable of handling requests while in transitioning, and properly terminate these with the correct sense code.
- Include target device descriptor in VPD page 83
For the ALUA device handler we'd need to identify the target device where a given target port belongs to. So include the respective values in the VPD page.
- Referrals support: Adding a new configfs attribute 'lba_map' which contains the referrals access mapping. The 'LBD Dependent' ALUA state can only be selected if an lba_map is present; also explicit ALUA has to be disabled.

Hannes Reinecke (8):
target_core_alua: validate ALUA state transition
target_core_alua: Allocate ALUA metadata on demand
target_core_alua: store old and pending ALUA state
target_core_alua: Use workqueue for ALUA transitioning
target_core: simplify scsi_name_len calculation
target_core_spc: Include target device descriptor in VPD page 83
target_core_alua: Referrals infrastructure
target_core_alua: Referrals configfs integration

 drivers/target/target_core_alua.c      | 546 +++++++++++++++++++++++++++------
 drivers/target/target_core_alua.h      |  15 +-
 drivers/target/target_core_configfs.c  | 180 ++++++++++-
 drivers/target/target_core_device.c    |   3 +
 drivers/target/target_core_sbc.c       |   5 +-
 drivers/target/target_core_spc.c       |  76 ++++-
 drivers/target/target_core_transport.c |  28 +-
 include/scsi/scsi.h                    |   1 +
 include/target/target_core_base.h      |  27 +-
 9 files changed, 770 insertions(+), 111 deletions(-)

1.7.12.4