Add a reload command.

Reviewed by:	hrs
MFC after:	3 days
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
Remove Giant-locked drivers support (DISKFLAG_NEEDSGIANT flag) from disk(9).

Since at least FreeBSD 7 we had only four of them in the base tree, and
in head branch, thanks to jhb@, we have no any for more then a year.
Remove global device lock acquisition from dev_relthread(), replacing it
with atomics on per-device data.
Update ahci(4), respecting recent driver changes.
Fix memory and references leak due to unfreed path.

Coverity CID:	1109817
Unconditionally acquire periph reference on CCB allocation failure.

cam_periph_acquire() can return error if periph already invalidated, but
that may be unacceptable and cause deadlock if the invalidated periph can't
be destroyed without "executing" the scheduled request.

Coverity CID:	1109822
MFC after:	2 months
Use the vdev's ashift to calculate the supported min block size passed to
zio_compress_data(..) when compressing l2arc buffers.

This eliminates l2arc I/O errors, which resulted in very poor performance on
vdev's configured with block size greater than 512b due to compression
assuming a smaller min block size than the vdev supports.

MFC after:	2 days
Fix memory and references leak due to unfreed path.

Coverity CID:	1109815
Fix memory and references leak due to unfreed path.

Coverity CID:	1054773
Standards-conformance and code deduplication:
- Use bus reference phandles in place of FDT offsets as IRQ domain keys
- Unify the identical macio/fdt/mambo OpenPIC drivers into one
- Be more forgiving (following ePAPR) about what we need from the device
  tree to identify an OpenPIC
- Correctly map all IRQs into an interrupt domain
- Set IRQ_*_CONFORM for interrupts on an unknown PIC type instead of
  failing attachment for that device.
Allow lots of interrupts (useful on multi-domain platforms) and do not
set device_quiet() on all devices attached under nexus(4).
Set BUS_PROBE_NOWILDCARD on this attachment as a stopgap. Unconditionally
poking at registers in unknown devices is not the best probe mechanism.
This should be reverted and a better solution found later.
Catch up on 6 years of improvements in Open Firmware nexus devices by
importing the sparc64 one. At least 90% of this code is MI and will be
moved into /sys/dev/ofw at some point in the future.
MFP4: 223121 (PIC portion), 225861, 227822, 229692 (PIC only), 229693,
230523, 1123614

Implement a driver for Robert Norton's PIC as an FDT interrupt
controller. Devices whose interrupt-parent property points to a beripic
device will have their interrupt allocation, activation , and setup
operations routed through the IC rather than down the traditional bus
hierarchy.

This driver largely abstracts the underlying CPU away allowing the
PIC to be implemented on CPU's other than BERI. Due to insufficient
abstractions a small amount of MIPS specific code is currently required
in fdt_mips.c and to implement counters.

MFC after:	3 days
Sponsored by:	DARPA/AFRL
Sync BERI kernel configs with P4:

Switch the majority of device configuration to FDT from hints.

Add BERI_*_BASE configs to reduce duplication in the MDROOT and SDROOT
kernels.

Add NFS and GSSAPI support by default.

MFC after:	3 days
Sponsored by:	DARPA/AFRL
Ignore registers on devices where the reg property is malformed. Issue a
warning if this happens under bootverbose. This prevents some
strange-looking entries in dmesg for SMU devices on Apple G5 systems.
Stop conflating WITHOUT_CLANG with WITHOUT_CLANG_IS_CC.  This allows
bootstrapping a copy of clang without building clang for the base system
which is useful for nanobsd and similar setups.  It's still probably
wrong to conflate what is installed as /usr/bin/cc with the selection
of a bootstrap compiler under WITH*_CLANG_IS_CC, but that's for another
day.

MFC after:	1 week
Sponsored by:	DARPA/AFRL
Mask out non-address bits in the mac address register, for proper
detection of an all-zeroes address.  Also remove a misplaced return.

Reviewed by:	br@
The TCP delayed ACK logic isn't aware of LRO passing up large aggregated
segments thinking it received only one segment. This causes it to enable
the delay the ACK for 100ms to wait for another segment which may never
come because all the data was received already.

Doing delayed ACK for LRO segments is bogus for two reasons: a) it pushes
us further away from acking every other packet; b) it introduces additional
delay in responding to the sender.  The latter is especially bad because it
is in the nature of LRO to aggregated all segments of a burst with no more
coming until an ACK is sent back.

Change the delayed ACK logic to detect LRO segments by being larger than
the MSS for this connection and issuing an immediate ACK for them to keep
the ACK clock ticking without interruption.

Reported by:	julian, cperciva
Tested by:	cperciva
Reviewed by:	lstewart
MFC after:	3 days