- Copy stable/10 (r259064) to releng/10.0 as part of the
10.0-RELEASE cycle.
- Update __FreeBSD_version [1]
- Set branch name to -RC1

[1] 10.0-CURRENT __FreeBSD_version value ended at '55', so
start releng/10.0 at '100' so the branch is started with
a value ending in zero.

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

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

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

Move the NFSv4.1 client patches over from projects/nfsv4.1-client
to head. I don't think the NFS client behaviour will change unless
the new "minorversion=1" mount option is used. It includes basic
NFSv4.1 support plus support for pNFS using the Files Layout only.
All problems detecting during an NFSv4.1 Bakeathon testing event
in June 2012 have been resolved in this code and it has been tested
against the NFSv4.1 server available to me.
Although not reviewed, I believe that kib@ has looked at it.

Post r223774, the NFSv4 client no longer has multiple instances
of the same lock_owner4 string. As such, the handling of cleanup
of lock_owners could be simplified. This simplification permitted
the client to do a ReleaseLockOwner operation when the process that
the lock_owner4 string represents, has exited. This permits the
server to release any storage related to the lock_owner4 string
before the associated open is closed. Without this change, it
is possible to exhaust a server's storage when a long running
process opens a file and then many child processes do locking
on the file, because the open doesn't get closed. A similar patch
was applied to the Linux NFSv4 client recently so that it wouldn't
exhaust a server's storage.

Reviewed by: zack
MFC after: 2 weeks

Post r223774 the NFSv4 client never uses the linked list with the
head nfsc_defunctlockowner. This patch simply removes the code that
loops through this always empty list, since the code no longer does
anything useful. It should not have any effect on the client's
behaviour.

MFC after: 2 weeks

Add a flag to the experimental NFSv4 client to indicate when
delegations are being returned for reasons other than a Recall.
Also, re-organize nfscl_recalldeleg() slightly, so that it leaves
clearing NMODIFIED to the ncl_flush() call and invalidates the
attribute cache after flushing. It is hoped that these changes
might fix the problem others have seen when using the NFSv4
client with delegations enabled, since I can't reliably reproduce
the problem. These changes only affect the client when doing NFSv4
mounts with delegations enabled.

MFC after: 10 days

Avoid extraneous recovery cycles in the experimental NFS client
when an NFSv4 server reboots, by doing two things.
1 - Make the function that acquires a stateid for I/O operations
block until recovery is complete, so that it doesn't acquire
out of date stateids.
2 - Only allow a recovery once every 1/2 of a lease duration, since
the NFSv4 server must provide a recovery grace period of at
least a lease duration. This should avoid recoveries caused
by an out of date stateid that was acquired for an I/O op.
just before a recovery cycle started.

MFC after: 1 week

The experimental NFS client was not filling in recovery credentials
for opens done locally in the client when a delegation for the file
was held. This could cause the client to crash in crsetgroups() when
recovering from a server crash/reboot. This patch fills in the
recovery credentials for this case, in order to avoid the client crash.
Also, add KASSERT()s to the credential copy functions, to catch any
other cases where the credentials aren't filled in correctly.

MFC after: 1 week

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)