The OBJ_TMPFS flag of vm_object means that there is unreclaimed tmpfs
vnode for the tmpfs node owning this object.  The flag is currently
used for two purposes.  First, it allows to correctly handle VV_TEXT
for tmpfs vnode when the ref count on the object is decremented to 1,
similar to vnode_pager_dealloc() for regular filesystems.  Second, it
prevents some operations, which are done on OBJT_SWAP vm objects
backing user anonymous memory, but are incorrect for the object owned
by tmpfs node.

The second kind of use of the OBJ_TMPFS flag is incorrect, since the
vnode might be reclaimed, which clears the flag, but vm object
operations must still be disallowed.

Introduce one more flag, OBJ_TMPFS_NODE, which is permanently set on
the object for VREG tmpfs node, and used instead of OBJ_TMPFS to test
whether vm object collapse and similar actions should be disabled.

Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
Change forgotten in r268615.  Set the OBJ_TMPFS_NODE flag for
vm_object of VREG tmpfs node.

Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
Rework the tmpfs unmount.

- Suspend filesystem for unmount.  This prevents new tmpfs nodes from
  instantiating, and also ensures that only unmount thread can destroy
  nodes.

- Do not start tmpfs node deletion until all vnodes are reclaimed,
  which guarantees that no thread can access tmpfs data.  For this,
  call vflush() in the loop, until the mnt_nvnodelistsize is non-zero.
  Note that after mnt_nvnodelistsize becomes 0, insmntque() blocks
  insertion of a vnode germ into the mount list of vnodes.

- Fail node allocation when the filesystem is being unmounted.  This
  is race-free due to the vflush() call in loop.  This is mostly
  cosmetic, avoiding some more work which might be done until
  suspension in unmount is started.

Note that there is currently no way to prevent new vnode instantiation
from readers during the unmount.  Due to this, forced unmount might
live-lock if vflush() loop cannot get to the zero vnode count due to
races with readers.  The unmount would proceed after the load is
lifted.

Tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
Unbreak the build by re-enabling exceptions.

Disabling them breaks build on archs using GCC. The problem is at line 156 of
bits/basic_ios.h:

	if (this->exceptions() & __state)
		__throw_exception_again;

With exceptions disabled __throw_exception_again is defined as

#define __throw_exception_again

at line 45 of exception_defines.h and the code results in an empty loop body,
which fails because of -Werror.

Approved by:	cognet
Make generation of nslexer.c more robust.

Ensure that lex errors fail the build instead of being silently ignored
due to the piped call.  Also postpone the update of the nslexer.c file
until we are sure we have generated it properly.

These changes fix some very obscure build failures I encountered while
building FreeBSD within a chroot that did not have devfs mounted. The
specific errors looked like:

.../libc.so.7: undefined reference to `_nsyyerror'
.../libc.so.7: undefined reference to `_nsyyin'
.../libc.so.7: undefined reference to `_nsyylex'
.../libc.so.7: undefined reference to `_nsyylineno'
.../libc.so.7: undefined reference to `_nsyytext'

and were caused due to a mangled nslexer.c being linked into libc.
Don't report non-native block-size pools under zpool status -x

zpool status -x is used to identify pools that are exhibiting
errors or are otherwise unavailable, therefore non-native
block-size pools shouldn't be reported.

Also update man page to clarify other additional conditions
which won't cause a pool to be displayed under zpool status -x.

Sponsored by:	Multiplay
Eliminate dead code.  There is no direct map.  This code was cut-and-pasted
from amd64.
On my Lenovo laptop, the firmware maps the EFI framebuffer with MTRRs set
to uncacheable. This leads to execrable console performance. Once PMAP is
up, remap the framebuffer as write-combining. This reduces boot time on my
laptop by 60% when booting with EFI.

MFC after:	2 weeks
Bump mdoc date after r268621.

X-MFC-With:	r268621
Minor (mostly cosmetic) cleanups

Several whitespace fixes
convert *rootDir from external to static.

Obtained from:	NetBSD, OpenBSD (partial)
MFC after:	3 days
fsck_msdosfs: be a bit more permissive

The free space value in the FSInfo block is merely unitialized when it is
0xffffffff. This fixes a bug found in NetBSD.

It must be noted that we never supported all the checks that NetBSD does
as some of them would cause failures with a freshly created FAT32
from MS-Windows.

While here, bring some space fixes.

Obtained from:	NetBSD (rev. 1.22)
MFC after:	3 days
msdosfs: Assorted fixes from other BSDs.

When truncating cluster chains fix the length of the cluster head.
http://marc.info/?t=140304310700005&r=1&w=2

Avoid infinite loops in cluster chain linked lists.
http://marc.info/?l=openbsd-tech&m=140275150804337&w=2

Avoid off-by-one on FAT12 filesystems.
http://marc.info/?l=openbsd-tech&m=140234174104724&w=2

Obtained from:	NetBSD (from OpenBSD)
MFC after:	1 week
Fix the Zedboard/Zynq ethernet driver to handle media speed changes so
that it can connect to switches at speeds other than 1gb.

This requires changing the reference clock speed.  Since we still don't
have a general clock API that lets a SoC-independant driver manipulate its
own clocks, this change includes a weak reference to a routine named
cgem_set_ref_clk().  The default implementation is a no-op; SoC-specific
code can provide an implementation that actually changes the speed.

Submitted by:	Thomas Skibo <ThomasSkibo@sbcglobal.net>
Manage struct sigacts refcnt with atomics instead of a mutex.

MFC after:	1 week
newfs_msdosfs: Respect FSFIXFAT

Fix some whitespace issues while here.

Obtained from:	NetBSD (rev. 1.9)
MFC after:	3 days
Plug p_pptr null test in do_execve. It is always true.
fortune(8): Search fortune files installed by ports/packages as well as
those supplied by the base system.

PR:		191800
Submitted by:	Andy Kosela
MFC after:	1 week
Add a call to synthesize a C/H/S value for block emulations
that require it (ahci). The algorithm used is from the VHD
specification.
Use the blockif CHS routine to create fake CHS values,
and then populate them in the identity page.

This fixes a divide-by-zero error at probe time with NetBSD.

MFC after:	1 week.
Allow multi-byte reads in the private CHELSIO_T4_GET_I2C ioctl.  The
firmware allows up to 48B to be read this way but the driver limits
itself to 8B at a time to remain compatible with old cxgbetool
binaries.

MFC after:	1 week