MFC r312603: Add initial support for CTL module unloading.

It is only a first step and not perfect, but better then nothing.
The main blocker is CAM target frontend, that can not be unloaded,
since CAM does not have mechanism to unregister periph driver now.

MFC r311804: Rewrite CTL statistics in more simple and scalable way.

Instead of collecting statistics for each combination of ports and logical
units, that consumed ~45KB per LU with present number of ports, collect
separate statistics for every port and every logical unit separately, that
consume only 176 bytes per each single LU/port. This reduces struct
ctl_lun size down to just 6KB.

Also new IOCTL API/ABI does not hardcode number of LUs/ports, and should
allow handling of very large quantities.

Old API is still enabled in stable branches for compatibility reasons.

MFC r310635: Decouple limits on number of LUNs per port and LUs per CTL.

Those two values are not directly related, so make them independent.
This does not change any limits immediately, but makes number of LUNs
per port controllable via tunable/sysctl kern.cam.ctl.lun_map_size.
After this change increasing CTL_MAX_LUNS should be pretty cheap,
and even making it tunable should be easy.

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Modify target port groups logic in CTL.

- Introduce "ha_shared" port option, which being set to "on" moves the
port into separate port group, shared between HA nodes. This allows to
better handle cases when iSCSI portals are bound to CARP address that can
dynamically move between nodes. Some initiators (at least VMware) don't
detect that after iSCSI reconnect they've attached to different SCSI port
from different port group, that totally breakes ALUA status parsing.
In theory, I believe, it should be enough to have different iSCSI portal
group tags on different nodes to make initiators detect this condition,
but it seems like VMware ignores those values, and even full LUN retaste
forced by UA does not help.
- Make CTL report up to three port groups: 1 -- non-HA mode or ports
with "ha_shared" option set, 2 -- HA node 1, 3 -- HA node 2.
- Report Transitioning state for all port groups when HA interlink is
connected, but neither of nodes is primary for the LUN.

MFC after: 2 weeks

Remove some control_softc references.

Remove unused target and initiator IDs.

Bring per-port LUN enable/disable code up to date:
- remove last remnants of never implemented multiple targets support;
- implement missing support for LUN mapping in this area.

Due to existing locking constraints LUN mapping code is practically
unlocked at this point. Hopefully it is not racy enough to live until
somebody get idea how to call sleeping fronend methods under lock also
taken by the same frontend in non-sleepable context. :(

Remove some dead and duplicate LUN enabling code.

CTL LUN mapping rewrite.

Replace iSCSI-specific LUN mapping mechanism with new one, working for any
ports. By default all ports are created without LUN mapping, exposing all
CTL LUNs as before. But, if needed, LUN mapping can be manually set on
per-port basis via ctladm. For its iSCSI ports ctld does it via ioctl(2).
The next step will be to teach ctld to work with FibreChannel ports also.

Respecting additional flexibility of the new mechanism, ctl.conf now allows
alternative syntax for LUN definition. LUNs can now be defined in global
context, and then referenced from targets by unique name, as needed. It
allows same LUN to be exposed several times via multiple targets.

While there, increase limit for LUNs per target in ctld from 256 to 1024.
Some initiators do not support LUNs above 255, but that is not our problem.

Discussed with: trasz
MFC after: 2 weeks
Relnotes: yes
Sponsored by: iXsystems, Inc.

Partially reconstruct Active/Standby clusting.

In this mode one head is in Active state, supporting all commands, while
another is in Standby state, supporting only minimal LUN discovery subset.

It is still incomplete since Standby state requires reservation support,
which is impossible to do right without having interlink between heads.
But it allows to run some basic experiments.

Add support for VMWare dialect of EXTENDED COPY command, aka VAAI Clone.

This allows to clone VMs and move them between LUNs inside one storage
host without generating extra network traffic to the initiator and back,
and without being limited by network bandwidth.

LUNs participating in copy operation should have UNIQUE NAA or EUI IDs set.
For LUNs without these IDs VMWare will use traditional copy operations.

Beware: the above LUN IDs explicitly set to values non-unique from the VM
cluster point of view may cause data corruption if wrong LUN is addressed!

MFC after: 2 weeks
Sponsored by: iXsystems, Inc.

Teach ctl_add_initiator() to dynamically allocate IIDs from pool.

If port passed negative IID value, the function will try to allocate IID
from the pool of unused, based on passed wwpn or name arguments. It does
all its best to make IID unique and persistent across reconnects.

This makes persistent reservation properly work for iSCSI. Previously,
in case of reconnects, reservation could be unexpectedly lost, or even
migrate between intiators.

Close race in r268291 between port destruction, delayed by sessions
teardown, and new port creation during `service ctld restart`.

Close it by returning iSCSI port internal state, that allows to identify
dying ports, which should not be counted as existing, from really alive.

Move lun_map() method from command nexus to port.

Previous implementation made impossible to do some things, such as calling
it for ports other then one through which command arrived.

Burry devid port method, which was a gross hack.

Instead make ports provide wanted port and target IDs, and LUNs provide
wanted LUN IDs. After that core Device ID VPD code only had to link all
of them together and add relative port and port group numbers.

LUN ID for iSCSI LUNs no longer created by CTL, but by ctld, and passed
to CTL as "scsiname" LUN option. This makes LUNs to report the same set
of IDs, independently from the port through which it is accessed, as
required by SCSI specifications.

Create separate CTL port for every iSCSI target (and maybe portal group).

Having single port for all iSCSI connections makes problematic implementing
some more advanced SCSI functionality in CTL, that require proper ports
enumeration and identification.

This change extends CTL iSCSI API, making ctld daemon to control list of
iSCSI ports in CTL. When new target is defined in config fine, ctld will
create respective port in CTL. When target is removed -- port will be
also removed after all active commands through that port properly aborted.
This change require ctld to be rebuilt to match the kernel.

As a minor side effect, this allows to have iSCSI targets without LUNs.
While that may look odd and not very useful, that is not incorrect.

Implement and use ctl_frontend_find().

Separate concepts of frontend and port.

Before iSCSI implementation CTL had no knowledge about frontend drivers,
it had only frontends, which really were ports (alike to LUNs, if comparing
to backends). But iSCSI added there ioctl() method, which does not belong
to frontend as a port, but belongs to a frontend driver.

Remove targ_enable()/targ_disable() frontend methods.

Those methods were never implemented, and I believe that their concept is
wrong, since single frontend (SCSI port) can not handle several targets.

CTL changes required for iSCSI target, most notably LUN remapping
and a mechanism to allow CTL frontends for retrieving LUN options.

Reviewed by: ken (earlier version)

Add the CAM Target Layer (CTL).

CTL is a disk and processor device emulation subsystem originally written
for Copan Systems under Linux starting in 2003. It has been shipping in
Copan (now SGI) products since 2005.

It was ported to FreeBSD in 2008, and thanks to an agreement between SGI
(who acquired Copan's assets in 2010) and Spectra Logic in 2010, CTL is
available under a BSD-style license. The intent behind the agreement was
that Spectra would work to get CTL into the FreeBSD tree.

Some CTL features:

- Disk and processor device emulation.
- Tagged queueing
- SCSI task attribute support (ordered, head of queue, simple tags)
- SCSI implicit command ordering support. (e.g. if a read follows a mode
select, the read will be blocked until the mode select completes.)
- Full task management support (abort, LUN reset, target reset, etc.)
- Support for multiple ports
- Support for multiple simultaneous initiators
- Support for multiple simultaneous backing stores
- Persistent reservation support
- Mode sense/select support
- Error injection support
- High Availability support (1)
- All I/O handled in-kernel, no userland context switch overhead.

(1) HA Support is just an API stub, and needs much more to be fully
functional.

ctl.c: The core of CTL. Command handlers and processing,
character driver, and HA support are here.

ctl.h: Basic function declarations and data structures.

ctl_backend.c,
ctl_backend.h: The basic CTL backend API.

ctl_backend_block.c,
ctl_backend_block.h: The block and file backend. This allows for using
a disk or a file as the backing store for a LUN.
Multiple threads are started to do I/O to the
backing device, primarily because the VFS API
requires that to get any concurrency.

ctl_backend_ramdisk.c: A "fake" ramdisk backend. It only allocates a
small amount of memory to act as a source and sink
for reads and writes from an initiator. Therefore
it cannot be used for any real data, but it can be
used to test for throughput. It can also be used
to test initiators' support for extremely large LUNs.

ctl_cmd_table.c: This is a table with all 256 possible SCSI opcodes,
and command handler functions defined for supported
opcodes.

ctl_debug.h: Debugging support.

ctl_error.c,
ctl_error.h: CTL-specific wrappers around the CAM sense building
functions.

ctl_frontend.c,
ctl_frontend.h: These files define the basic CTL frontend port API.

ctl_frontend_cam_sim.c: This is a CTL frontend port that is also a CAM SIM.
This frontend allows for using CTL without any
target-capable hardware. So any LUNs you create in
CTL are visible in CAM via this port.

ctl_frontend_internal.c,
ctl_frontend_internal.h:
This is a frontend port written for Copan to do
some system-specific tasks that required sending
commands into CTL from inside the kernel. This
isn't entirely relevant to FreeBSD in general,
but can perhaps be repurposed.

ctl_ha.h: This is a stubbed-out High Availability API. Much
more is needed for full HA support. See the
comments in the header and the description of what
is needed in the README.ctl.txt file for more
details.

ctl_io.h: This defines most of the core CTL I/O structures.
union ctl_io is conceptually very similar to CAM's
union ccb.

ctl_ioctl.h: This defines all ioctls available through the CTL
character device, and the data structures needed
for those ioctls.

ctl_mem_pool.c,
ctl_mem_pool.h: Generic memory pool implementation used by the
internal frontend.

ctl_private.h: Private data structres (e.g. CTL softc) and
function prototypes. This also includes the SCSI
vendor and product names used by CTL.

ctl_scsi_all.c,
ctl_scsi_all.h: CTL wrappers around CAM sense printing functions.

ctl_ser_table.c: Command serialization table. This defines what
happens when one type of command is followed by
another type of command.

ctl_util.c,
ctl_util.h: CTL utility functions, primarily designed to be
used from userland. See ctladm for the primary
consumer of these functions. These include CDB
building functions.

scsi_ctl.c: CAM target peripheral driver and CTL frontend port.
This is the path into CTL for commands from
target-capable hardware/SIMs.

README.ctl.txt: CTL code features, roadmap, to-do list.

usr.sbin/Makefile: Add ctladm.

ctladm/Makefile,
ctladm/ctladm.8,
ctladm/ctladm.c,
ctladm/ctladm.h,
ctladm/util.c: ctladm(8) is the CTL management utility.
It fills a role similar to camcontrol(8).
It allow configuring LUNs, issuing commands,
injecting errors and various other control
functions.

usr.bin/Makefile: Add ctlstat.

ctlstat/Makefile
ctlstat/ctlstat.8,
ctlstat/ctlstat.c: ctlstat(8) fills a role similar to iostat(8).
It reports I/O statistics for CTL.

sys/conf/files: Add CTL files.

sys/conf/NOTES: Add device ctl.

sys/cam/scsi_all.h: To conform to more recent specs, the inquiry CDB
length field is now 2 bytes long.

Add several mode page definitions for CTL.

sys/cam/scsi_all.c: Handle the new 2 byte inquiry length.

sys/dev/ciss/ciss.c,
sys/dev/ata/atapi-cam.c,
sys/cam/scsi/scsi_targ_bh.c,
scsi_target/scsi_cmds.c,
mlxcontrol/interface.c: Update for 2 byte inquiry length field.

scsi_da.h: Add versions of the format and rigid disk pages
that are in a more reasonable format for CTL.

amd64/conf/GENERIC,
i386/conf/GENERIC,
ia64/conf/GENERIC,
sparc64/conf/GENERIC: Add device ctl.

i386/conf/PAE: The CTL frontend SIM at least does not compile
cleanly on PAE.

Sponsored by: Copan Systems, SGI and Spectra Logic
MFC after: 1 month