Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Modify the NFSv4 client so that it can handle owner
and owner_group strings that consist entirely of
digits, interpreting them as the uid/gid number.
This change was needed since new (>= 3.3) Linux
servers reply with these strings by default.
This change is mandated by the rfc3530bis draft.
Reported on freebsd-stable@ under the Subject
heading "Problem with Linux >= 3.3 as NFSv4 server"
by Norbert Aschendorff on Aug. 20, 2012.

Tested by: norbert.aschendorff at yahoo.de
Reviewed by: jhb
MFC after: 2 weeks

A problem with the NFSv4 server was reported by Andrew Leonard
to freebsd-fs@, where the setfacl of an NFSv4 acl would fail.
This was caused by the VOP_ACLCHECK() call for ZFS replying
EOPNOTSUPP. After discussion with rwatson@, it was determined
that a call to VOP_ACLCHECK() before doing VOP_SETACL() is not
required. This patch fixes the problem by deleting the
VOP_ACLCHECK() call.

Tested by: Andrew Leonard (previous version)
MFC after: 1 week

Add DEXITCODE plumbing to NFS.

Isilon has the concept of an in-memory exit-code ring that saves the last exit
code of a function and allows for stack tracing. This is very helpful when
debugging tough issues.

This patch is essentially a no-op for BSD at this point, until we upstream
the dexitcode logic itself. The patch adds DEXITCODE calls to every NFS
function that returns an errno error code. A number of code paths were also
reorganized to have single exit paths, to reduce code duplication.

Submitted by: David Kwan <dkwan@isilon.com>
Reviewed by: rmacklem
Approved by: zml (mentor)
MFC after: 2 weeks

Fix the experimental NFSv4 server so that it uses VOP_PATHCONF()
to determine if a file system supports NFSv4 ACLs. Since
VOP_PATHCONF() must be called with a locked vnode, the function
is called before nfsvno_fillattr() and the result is passed in
as an extra argument.

MFC after: 2 weeks

Modify the experimental server so that it uses VOP_ACCESSX().
This is necessary in order to enable NFSv4 ACL support. The
argument to nfsvno_accchk() was changed to an accmode_t and
the function nfsrv_aclaccess() was no longer needed and,
therefore, deleted.

Reviewed by: trasz
MFC after: 2 weeks

Remove unneeded ifdefs.

Reviewed by: rmacklem

Fix typo in the comment.

Don't check MAC in the NFS server ACL set path, right now we aren't
enforcing MAC for NFS clients.

Fix the experimental nfs subsystem so that it builds with the
current NFSv4 ACLs, as defined in sys/acl.h. It still needs a
way to test a mount point for NFSv4 ACL support before it will
work. Until then, the NFSHASNFS4ACL() macro just always returns 0.

Approved by: kib (mentor)

Adapt to the new ACL #define names.

Reviewed by: rmacklem@

Add the experimental nfs subtree to the kernel, that includes
support for NFSv4 as well as NFSv2 and 3.
It lives in 3 subdirs under sys/fs:
nfs - functions that are common to the client and server
nfsclient - a mutation of sys/nfsclient that call generic functions
to do RPCs and handle state. As such, it retains the
buffer cache handling characteristics and vnode semantics that
are found in sys/nfsclient, for the most part.
nfsserver - the server. It includes a DRC designed specifically for
NFSv4, that is used instead of the generic DRC in sys/rpc.
The build glue will be checked in later, so at this point, it
consists of 3 new subdirs that should not affect kernel building.

Approved by: kib (mentor)