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

geom: unsign some types to match their definitions and avoid overflows.

In struct:gctl_req, nargs is unsigned.

In mirror:
g_mirror_syncreqs is unsigned.

In raid:
in struct:g_raid_volume, v_disks_count is unsigned.

In virstor:
in struct:g_virstor_softc, n_components is unsigned.

MFC after: 2 weeks

Cleanup unnecessary semicolons from the kernel.

Found with devel/coccinelle.

Replace constant with proper sizeof().

Submitted by: Dmitry Luhtionov <dmitryluhtionov@gmail.com>
MFC after: 2 weeks

Reduce number of opens by REOM RAID during provider taste.

Instead opening/closing provider by each of metadata classes, do it only
once in core code. Since for SCSI disks open/close means sending some
SCSI commands to the device, this change reduces taste time.

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

Merge GEOM direct dispatch changes from the projects/camlock branch.

When safety requirements are met, it allows to avoid passing I/O requests
to GEOM g_up/g_down thread, executing them directly in the caller context.
That allows to avoid CPU bottlenecks in g_up/g_down threads, plus avoid
several context switches per I/O.

The defined now safety requirements are:
- caller should not hold any locks and should be reenterable;
- callee should not depend on GEOM dual-threaded concurency semantics;
- on the way down, if request is unmapped while callee doesn't support it,
the context should be sleepable;
- kernel thread stack usage should be below 50%.

To keep compatibility with GEOM classes not meeting above requirements
new provider and consumer flags added:
- G_CF_DIRECT_SEND -- consumer code meets caller requirements (request);
- G_CF_DIRECT_RECEIVE -- consumer code meets callee requirements (done);
- G_PF_DIRECT_SEND -- provider code meets caller requirements (done);
- G_PF_DIRECT_RECEIVE -- provider code meets callee requirements (request).
Capable GEOM class can set them, allowing direct dispatch in cases where
it is safe. If any of requirements are not met, request is queued to
g_up or g_down thread same as before.

Such GEOM classes were reviewed and updated to support direct dispatch:
CONCAT, DEV, DISK, GATE, MD, MIRROR, MULTIPATH, NOP, PART, RAID, STRIPE,
VFS, ZERO, ZFS::VDEV, ZFS::ZVOL, all classes based on g_slice KPI (LABEL,
MAP, FLASHMAP, etc).

To declare direct completion capability disk(9) KPI got new flag equivalent
to G_PF_DIRECT_SEND -- DISKFLAG_DIRECT_COMPLETION. da(4) and ada(4) disk
drivers got it set now thanks to earlier CAM locking work.

This change more then twice increases peak block storage performance on
systems with manu CPUs, together with earlier CAM locking changes reaching
more then 1 million IOPS (512 byte raw reads from 16 SATA SSDs on 4 HBAs to
256 user-level threads).

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

- Fix rebuild position broken at r245522.
- Identify one more metadata field.

For Promise/AMD metadata add support for disks with capacity above 2TiB
and for volumes with sector size above 512 bytes.

Add basic BIO_DELETE support to GEOM RAID class for all RAID levels.

If at least one subdisk in the volume supports it, BIO_DELETE requests
will be propagated down. Unfortunatelly, for RAID levels with redundancy
unmapped blocks will be mapped back during first rebuild/resync process.

Sponsored by: iXsystems, Inc.
MFC after: 1 month

NULL-ify last previously used pointer instead of last possible pointer.
This should be only a cosmetic change.

Found by: Clang Static Analyzer

Make graid command line a bit more friendly by allowing volume name or
provider name to be specified instead of geom name (first argument in all
subcommands except label). In most cases there is only one array used
any way, so it is not really useful to make user type ugly geom names like
Intel-f0bdf223 or SiI-732c2b9448cf. Though they can be used in some cases.

Sponsored by: iXsystems, Inc.
MFC after: 1 month

Add global and per-module sysctls/tunables to enable/disable metadata taste.
That should help to handle some cases when disk has some RAID metadata that
should be ignored, especially during boot.

MFC after: 3 days

Plug small memory leaks.

Fix RAID5 level names changed at r234603.

Add sos@ copyrights to RAID metadata modules, respecting his efforts in
decoding metadata formats in ataraid(4) code.

Add to GEOM RAID class module for reading non-degraded RAID5 volumes and
some environment to differentiate 4 possible RAID5 on-disk layouts.

Tested with Intel and AMD RAID BIOSes.

MFC after: 2 weeks

Clarify disks/volumes above 2TiB support in geom_raid:
- add support for volumes above 2TiB with Promise metadata format;
- enforse and document other limitations:
- Intel and Promise metadata formats do not support disks above 2TiB;
- NVIDIA metadata format does not support volumes above 2TiB.

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

Bunch of small bugfixes and cleanups.

Found with: Clang Static Analyzer

Bunch of small bugfixes and cleanups.

Found with: Coverity Prevent(tm)
CID: 9656, 9658, 9693, 9705, 9706, 9707, 9808, 9809, 9810,
9711, 9712, 9713, 9714

MFgraid/head:
Add new RAID GEOM class, that is going to replace ataraid(4) in supporting
various BIOS-based software RAIDs. Unlike ataraid(4) this implementation
does not depend on legacy ata(4) subsystem and can be used with any disk
drivers, including new CAM-based ones (ahci(4), siis(4), mvs(4), ata(4)
with `options ATA_CAM`). To make code more readable and extensible, this
implementation follows modular design, including core part and two sets
of modules, implementing support for different metadata formats and RAID
levels.

Support for such popular metadata formats is now implemented:
Intel, JMicron, NVIDIA, Promise (also used by AMD/ATI) and SiliconImage.

Such RAID levels are now supported:
RAID0, RAID1, RAID1E, RAID10, SINGLE, CONCAT.

For any all of these RAID levels and metadata formats this class supports
full cycle of volume operations: reading, writing, creation, deletion,
disk removal and insertion, rebuilding, dirty shutdown detection
and resynchronization, bad sector recovery, faulty disks tracking,
hot-spare disks. For Intel and Promise formats there is support multiple
volumes per disk set.

Look graid(8) manual page for additional details.

Co-authored by: imp
Sponsored by: Cisco Systems, Inc. and iXsystems, Inc.