Previously we allowed servers as old as 7.1 to connect (there never was a
7.0).  However, we wrongly assumed a few things about protocols older than
7.8.  This commit attempts to support servers as old as 7.4 but no older.  I
added no new tests because I'm not sure there actually _are_ any servers
this old in the wild.

Sponsored by:	The FreeBSD Foundation

In the case of mmap(), add a HISTORY section.  Mention that mmap() and
mprotect()'s documentation predates an implementation.  The
implementation first saw wide use in 4.3-Reno, but there seems to be no
easy way to express that in mdoc so stick with 4.4BSD.

Reviewed by:	emaste
Requested by:	cem
Sponsored by:	DARPA, AFRL
Differential Revision:	https://reviews.freebsd.org/D20713

This protocol version adds one new feature: the ability for the server to
set the maximum number of background requests and a "congestion threshold"
with ill-defined properties.  I don't know of any fuse file systems in ports
that use this feature, so I'm not implementing it.

Sponsored by:	The FreeBSD Foundation

When encryption was first added to ZFS, we made a decision to
prevent users from creating unencrypted children of encrypted
datasets. The idea was to prevent users from inadvertently
leaving some of their data unencrypted. However, since the
release of 0.8.0, some legitimate reasons have been brought up
for this behavior to be allowed. This patch simply removes this
limitation from all code paths that had checks for it and updates
the tests accordingly.

Reviewed-by: Jason King <jason.king@joyent.com>
Reviewed-by: Sean Eric Fagan <sef@ixsystems.com>
Reviewed-by: Richard Laager <rlaager@wiktel.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Tom Caputi <tcaputi@datto.com>
Closes #8737 
Closes #8870

The whereis command should not be used since it may not exist 
in the initramfs.  The dracut plymouth module also uses the type
command instead of whereis.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Garrett Fields <ghfields@gmail.com>
Signed-off-by: Dacian Reece-Stremtan <dacianstremtan@gmail.com>
Closes #8920 
Closes #8938

A new macro PROT_MAX() alters a protection value so it can be OR'd with
a regular protection value to specify the maximum permissions.  If
present, these flags specify the maximum permissions.

While these flags are non-portable, they can be used in portable code
with simple ifdefs to expand PROT_MAX() to 0.

This change allows (e.g.) a region that must be writable during run-time
linking or JIT code generation to be made permanently read+execute after
writes are complete.  This complements W^X protections allowing more
precise control by the programmer.

This change alters mprotect argument checking and returns an error when
unhandled protection flags are set.  This differs from POSIX (in that
POSIX only specifies an error), but is the documented behavior on Linux
and more closely matches historical mmap behavior.

In addition to explicit setting of the maximum permissions, an
experimental sysctl vm.imply_prot_max causes mmap to assume that the
initial permissions requested should be the maximum when the sysctl is
set to 1.  PROT_NONE mappings are excluded from this for compatibility
with rtld and other consumers that use such mappings to reserve
address space before mapping contents into part of the reservation.  A
final version this is expected to provide per-binary and per-process
opt-in/out options and this sysctl will go away in its current form.
As such it is undocumented.

Reviewed by:	emaste, kib (prior version), markj
Additional suggestions from:	alc
Obtained from:	CheriBSD
Sponsored by:	DARPA, AFRL
Differential Revision:	https://reviews.freebsd.org/D18880

If the fuse daemon supports FUSE_BMAP, then use that for the block mapping.
Otherwise, use the same technique used by vop_stdbmap.  Report large values
for runp and runb in order to maximize read clustering and minimize upcalls,
even if we don't know the true layout.

The major result of this change is that sequential reads to FUSE files will
now usually happen 128KB at a time instead of 64KB.

Sponsored by:	The FreeBSD Foundation

Sponsored by:	The FreeBSD Foundation