MFC r310644: Fix/synchronize field types in struct ctl_modepage_header.

MFC r310640, r310643:
Add support for revert to defaults (RTD) bit in MODE SELECT.

MFC r310257: Improve support for informational exceptions.

While CTL still has no real events to report in this way (like SMART),
it is possible to trigger false event by manually setting TEST bit in
Informational Exceptions Control mode page, that can be useful for
initiator testing. This code supports all flavours of IE reporting:
UNIT ATTENTION, RECOVERED ERROR and NO SENSE sense keys, REQUEST SENSE
command and Informational Exceptions log page.

MFC r307350: Add LUN options to limit UNMAP and WRITE SAME sizes.

CTL itself has no limits on on UNMAP and WRITE SAME sizes. But depending
on backends large requests may take too much time. To avoid that new
configuration options allow to hint initiator maximal sizes it should not
exceed.

MFC r289881: Give CTL support for PIM_EXTLUNS when talking to CAM.

CTL itself still lives in flat LUN space, but it can generate extended
numbers if CAM SIM reports such capability.

MFC r288348: Umplement media load/eject support for removable devices.

In case of block backend eject really closes the backing store, while
load tries to open it back. Failed store open is reported as no media.

MFC r288148: Synchronize mode pages between HA peers.

We allow to modify only few fields in mode pages now, but still it is
not good if they unexpectedly change during failover. Also this fixes
reporting of "Mode parameters changed" UAs on secondary node.

MFC r287967: Relax serseq option operation for reads.

Previously, with serseq enabled, next command was unblocked only after
previous completed. With this change, for read operations, next command
is unblocked as soon as last media read completed. This is important
for frontends that actually wait for data move completion (like camtgt),
or when data are moved through the HA link, or especially when both.

MFC r287940: Replicate initiators WWPNs and names between HA peers.

MFC r287756:
Report INQUIRY DATA HAS CHANGED for related LUNs on port on-/offline.

MFC r287621: Reimplement CTL High Availability.

CTL HA functionality was originally implemented by Copan many years ago,
but large part of the sources was never published. This change includes
clean room implementation of the missing code and fixes for many bugs.

This code supports dual-node HA with ALUA in four modes:
- Active/Unavailable without interlink between nodes;
- Active/Standby with second node handling only basic LUN discovery and
reservation, synchronizing with the first node through the interlink;
- Active/Active with both nodes processing commands and accessing the
backing storage, synchronizing with the first node through the interlink;
- Active/Active with second node working as proxy, transfering all
commands to the first node for execution through the interlink.

Unlike original Copan's implementation, depending on specific hardware,
this code uses simple custom TCP-based protocol for interlink. It has
no authentication, so it should never be enabled on public interfaces.

The code may still need some polishing, but generally it is functional.

Relnotes: yes
Sponsored by: iXsystems, Inc.

MFC r287500: Allow LUN options modification via CTL_LUNREQ_MODIFY.

Not all changes take effect, but that is a different question.

MFC r287433: Small UA cleanup.

MFC r286807: Move "ioctl" CAM frontend into separate file.

It has nothing to share with too huge ctl.c other then device descriptor,
but even that may be counted as design error that may be fixed later.
At some point we may even want to have several ioctl ports.

MFC r286406, r286414:
Wrap some unused functions with notyet, it is necessary to be able to
build the modules/ctl directly.
Remove a dead MALLOC_DEFINE.

MFC r278584: Add support for General Statistics and Performance log page.

CTL already collects most of statistics reported there, so why not.

MFC r275953: Replace ctl_min() macro with MIN().

MFC r275865:
Add configuration options to override physical and UNMAP blocks geometry.

While in most cases CTL should correctly fetch those values from backing
storages, there are some initiators (like MS SQL), that may not like large
physical block sizes, even if they are true. For such cases allow override
fetched values with supported ones (like 4K).

MFC r275474: Add GET LBA STATUS command support to CTL.

It is implemented for LUNs backed by ZVOLs in "dev" mode and files.
GEOM has no such API, so for LUNs backed by raw devices all LBAs will
be reported as mapped/unknown.

Sponsored by: iXsystems, Inc.

MFC r274154, r274163:
Add to CTL support for logical block provisioning threshold notifications.

For ZVOL-backed LUNs this allows to inform initiators if storage's used or
available spaces get above/below the configured thresholds.

Sponsored by: iXsystems, Inc.

MFC r273693: Fix printing non-terminated strings in devlist XML.

MFC r273075: Remove couple Copan's vendor-specific mode pages.

Those pages are highly system-/hardware-specific, the code is incomplete,
and so they hardly can be useful for anybody else.

MFC r271309:
Improve cache control support, including DPO/FUA flags and the mode page.

At this moment it works only for files and ZVOLs in device mode since BIOs
have no respective respective cache control flags (DPO/FUA).

MFC r272040:
When reporting some major UNIT ATTENTION condition, like POWER ON OCCURRED
or I_T NEXUS LOSS, clear all minor UAs for the LUN, redundant in this case.

All SAM specifications tell that target MAY do it, but libiscsi initiator
seems require it to be done, terminating connection with error if some more
UAs happen to be reported during iSCSI connection.

Approved by: re (gjb)

MFC r268363:
Add support for READ FULL STATUS action of PERSISTENT RESERVE IN command.

MFC r268353:
Implement ABORT TASK SET and I_T NEXUS RESET task management functions.

Use the last one to terminate active commands on iSCSI session termination.
Previous code was aborting only commands doing some data moves.

MFC r268291:
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.

MFC r268280:
Make options KPI more generic to allow it to be used for ports too,
not only for LUNs.

MFC r267639:
Increase CTL_DEVID_LEN from 16 to 64 bytes.

SPC-4 recommends T10 vendor ID based LUN ID was created by concatenating
product name and serial number (and istgt follows that). But product name
is 16 bytes long by itself, so 16 bytes total length is clearly not enough
to fit both.

To keep compatibility with existing configurations, pad short device IDs
to old length of 16, same as before.

This change probably breaks CTL user-level ABI, so control tools should
be rebuilt after this change.

MFC r267643, r267873, r268391, r268398:
Introduce fine-grained CTL locking to improve SMP scalability.

Split global ctl_lock, historically protecting most of CTL context:
- remaining ctl_lock now protects lists of fronends and backends;
- per-LUN lun_lock(s) protect LUN-specific information;
- per-thread queue_lock(s) protect request queues.
This allows to radically reduce congestion on ctl_lock.

Create multiple worker threads, depending on number of CPUs, and assign
each LUN to one of them. This allows to spread load between multiple CPUs,
still avoiging congestion on queues and LUNs locks.

On 40-core server, exporting 5 LUNs, each backed by gstripe of SATA SSDs,
accessed via 6 iSCSI connections, this change improves peak request rate
from 250K to 680K IOPS.

Sponsored by: iXsystems, Inc.

MFC r267537:
Add support for VERIFY(10/12/16) and COMPARE AND WRITE SCSI commands.

Make data_submit backends method support not only read and write requests,
but also two new ones: verify and compare. Verify just checks readability
of the data in specified location without transferring them outside.
Compare reads the specified data and compares them to received data,
returning error if they are different.

VERIFY(10/12/16) commands request either verify or compare from backend,
depending on BYTCHK CDB field. COMPARE AND WRITE command executed in two
stages: first it requests compare, and then, if succeesed, requests write.
Atomicity of operation is guarantied by CTL request ordering code.

Sponsored by: iXsystems, Inc.

MFC r287756:
Report INQUIRY DATA HAS CHANGED for related LUNs on port on-/offline.

MFC r287621: Reimplement CTL High Availability.

CTL HA functionality was originally implemented by Copan many years ago,
but large part of the sources was never published. This change includes
clean room implementation of the missing code and fixes for many bugs.

This code supports dual-node HA with ALUA in four modes:
- Active/Unavailable without interlink between nodes;
- Active/Standby with second node handling only basic LUN discovery and
reservation, synchronizing with the first node through the interlink;
- Active/Active with both nodes processing commands and accessing the
backing storage, synchronizing with the first node through the interlink;
- Active/Active with second node working as proxy, transfering all
commands to the first node for execution through the interlink.

Unlike original Copan's implementation, depending on specific hardware,
this code uses simple custom TCP-based protocol for interlink. It has
no authentication, so it should never be enabled on public interfaces.

The code may still need some polishing, but generally it is functional.

Relnotes: yes
Sponsored by: iXsystems, Inc.

MFC r287500: Allow LUN options modification via CTL_LUNREQ_MODIFY.

Not all changes take effect, but that is a different question.

MFC r287433: Small UA cleanup.

MFC r286807: Move "ioctl" CAM frontend into separate file.

It has nothing to share with too huge ctl.c other then device descriptor,
but even that may be counted as design error that may be fixed later.
At some point we may even want to have several ioctl ports.

MFC r286406, r286414:
Wrap some unused functions with notyet, it is necessary to be able to
build the modules/ctl directly.
Remove a dead MALLOC_DEFINE.

MFC r278584: Add support for General Statistics and Performance log page.

CTL already collects most of statistics reported there, so why not.

MFC r275953: Replace ctl_min() macro with MIN().

MFC r275865:
Add configuration options to override physical and UNMAP blocks geometry.

While in most cases CTL should correctly fetch those values from backing
storages, there are some initiators (like MS SQL), that may not like large
physical block sizes, even if they are true. For such cases allow override
fetched values with supported ones (like 4K).

MFC r275474: Add GET LBA STATUS command support to CTL.

It is implemented for LUNs backed by ZVOLs in "dev" mode and files.
GEOM has no such API, so for LUNs backed by raw devices all LBAs will
be reported as mapped/unknown.

Sponsored by: iXsystems, Inc.

MFC r274154, r274163:
Add to CTL support for logical block provisioning threshold notifications.

For ZVOL-backed LUNs this allows to inform initiators if storage's used or
available spaces get above/below the configured thresholds.

Sponsored by: iXsystems, Inc.

MFC r273693: Fix printing non-terminated strings in devlist XML.

MFC r273075: Remove couple Copan's vendor-specific mode pages.

Those pages are highly system-/hardware-specific, the code is incomplete,
and so they hardly can be useful for anybody else.

MFC r271309:
Improve cache control support, including DPO/FUA flags and the mode page.

At this moment it works only for files and ZVOLs in device mode since BIOs
have no respective respective cache control flags (DPO/FUA).

MFC r272040:
When reporting some major UNIT ATTENTION condition, like POWER ON OCCURRED
or I_T NEXUS LOSS, clear all minor UAs for the LUN, redundant in this case.

All SAM specifications tell that target MAY do it, but libiscsi initiator
seems require it to be done, terminating connection with error if some more
UAs happen to be reported during iSCSI connection.

Approved by: re (gjb)

MFC r268363:
Add support for READ FULL STATUS action of PERSISTENT RESERVE IN command.

MFC r268353:
Implement ABORT TASK SET and I_T NEXUS RESET task management functions.

Use the last one to terminate active commands on iSCSI session termination.
Previous code was aborting only commands doing some data moves.

MFC r268291:
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.

MFC r268280:
Make options KPI more generic to allow it to be used for ports too,
not only for LUNs.

MFC r267639:
Increase CTL_DEVID_LEN from 16 to 64 bytes.

SPC-4 recommends T10 vendor ID based LUN ID was created by concatenating
product name and serial number (and istgt follows that). But product name
is 16 bytes long by itself, so 16 bytes total length is clearly not enough
to fit both.

To keep compatibility with existing configurations, pad short device IDs
to old length of 16, same as before.

This change probably breaks CTL user-level ABI, so control tools should
be rebuilt after this change.

MFC r267643, r267873, r268391, r268398:
Introduce fine-grained CTL locking to improve SMP scalability.

Split global ctl_lock, historically protecting most of CTL context:
- remaining ctl_lock now protects lists of fronends and backends;
- per-LUN lun_lock(s) protect LUN-specific information;
- per-thread queue_lock(s) protect request queues.
This allows to radically reduce congestion on ctl_lock.

Create multiple worker threads, depending on number of CPUs, and assign
each LUN to one of them. This allows to spread load between multiple CPUs,
still avoiging congestion on queues and LUNs locks.

On 40-core server, exporting 5 LUNs, each backed by gstripe of SATA SSDs,
accessed via 6 iSCSI connections, this change improves peak request rate
from 250K to 680K IOPS.

Sponsored by: iXsystems, Inc.

MFC r267537:
Add support for VERIFY(10/12/16) and COMPARE AND WRITE SCSI commands.

Make data_submit backends method support not only read and write requests,
but also two new ones: verify and compare. Verify just checks readability
of the data in specified location without transferring them outside.
Compare reads the specified data and compares them to received data,
returning error if they are different.

VERIFY(10/12/16) commands request either verify or compare from backend,
depending on BYTCHK CDB field. COMPARE AND WRITE command executed in two
stages: first it requests compare, and then, if succeesed, requests write.
Atomicity of operation is guarantied by CTL request ordering code.

Sponsored by: iXsystems, Inc.