Three improvements to vnode_pager_generic_getpages():

Eliminate an exclusive object lock acquisition and release on the expected
execution path.

Do page zeroing before the object lock is acquired rather than during the
time that the object lock is held.

Use vm_pager_free_nonreq() to eliminate duplicated code.

Reviewed by:	kib
MFC after:	6 weeks
Sponsored by:	EMC / Isilon Storage Division
Add stricter checking of some mmap() arguments:
- Fail with EINVAL if an invalid protection mask is passed to mmap().
- Fail with EINVAL if an unknown flag is passed to mmap().
- Fail with EINVAL if both MAP_PRIVATE and MAP_SHARED are passed to mmap().
- Require one of either MAP_PRIVATE or MAP_SHARED for non-anonymous
  mappings.

Reviewed by:	alc, kib
MFC after:	2 weeks
Differential Revision:	https://reviews.freebsd.org/D698
Chunk IDs are 8 bit entities, not 16 bit.
Thanks to Peter Kasting from Google for drawing
my attention to it.

MFC after: 3 days
Add quirks to disable READ CAPACITY (16) for PNY USB 3.0 Flash Drives.

Submitted by:	Sean Fagan <sef@ixsystems.com>
MFC after:	3 days
Set DROP_EN on each RX queue if transmit flow-control is disabled.

This allows the NIC to drop frames on the receive queue and not
cause the MAC to block on receiving to _any_ queue.

Tested:

igb0@pci0:5:0:0:        class=0x020000 card=0x152115d9 chip=0x15218086 rev=0x01 hdr=0x00
    vendor     = 'Intel Corporation'
    device     = 'I350 Gigabit Network Connection'
    class      = network
    subclass   = ethernet

Discussed with: Eric Joyner <eric.joyner@intel.com>

MFC after:	1 week
Sponsored by:	Norse Corp, Inc.
Fix a double-free of mbufs in rx_ixgbe_discard().

fmp->buf at the free point is already part of the chain being freed,
so double-freeing is counter-productive.

Submitted by:	Marc De La Gueronniere <mdelagueronniere@verisign.com>
MFC after:	1 week
Sponsored by:	Verisign, Inc.
The error bits are not valid with EOP=0; so intermediary fragments should
not be discarded.

Submitted by:	Marc De La Gueronniere <mdelagueronniere@verisign.com>
MFC after:	1 week
Sponsored by:	Verisign, Inc.
Disable flow-director support until it's been debugged and verified.

The flowdirector feature shares on-chip memory with other things
such as the RX buffers.  In theory it should be configured in a way
that doesn't interfere with the rest of operation.  In practice,
the RX buffer calculation didn't take the flow-director allocation
into account and there'd be overlap.  This lead to various garbage
frames being received containing what looks like internal NIC state.

What _I_ saw was traffic ending up in the wrong RX queues.
If I was doing a UDP traffic test with only one NIC ring receiving
traffic, everything is fine.  If I fired up a second UDP stream
which came in on another ring, there'd be a few percent of traffic
from both rings ending up in the wrong ring.  Ie, the RSS hash would
indicate it was supposed to come in ring X, but it'd come in ring Y.

However, when the allocation was fixed up, the developers at Verisign
still saw traffic stalls.

The flowdirector feature ends up fiddling with the NIC to do various
attempts at load balancing connections by populating flow table rules
based on sampled traffic.  It's likely that all of that has to be
carefully reviewed and made less "magic".

So for now the flow director feature is disabled (which fixes both
what I was seeing and what they were seeing) until it's all much
more debugged and verified.

Tested:

* (me) 82599EB 2x10G NIC, RSS UDP testing.
* (verisign) not sure on the NIC (but likely 82599), 100k-200k/sec TCP
  transaction tests.

Submitted by:	Marc De La Gueronniere <mdelagueronniere@verisign.com>
MFC after:	1 week
Sponsored by:	Verisign, Inc.
Merge remote-tracking branch 'origin/master' into hardened/current/master

Conflicts:
	sys/vm/vm_mmap.c (fixed)