nfs4: support hard links properly

The main purpose of this patch is to prevent VFS from removing a vnode to early
what might have happened if the NFS client knew it had more than one name but
then one of them was deleted. Moreover, all discovered and still valid names
are stored what may be useful in proper file handle recovery when they are
volatile.

This patch fixes both #9558 and #9561.

nfs4: Remove CacheRevalidator

There is no point in periodically revalidating all existing directory caches.
Directory snapshot can be revalidated when readdir is invoked.

nfs4: Introduce VnodeToInode mapping

VnodeToInode is another abstraction layer between VFS vnodes and NFS nodes.
It simplifies dealing with race conditions as well as faking some guarantees
VFS expects but NFS does not provide.

nfs4: Add asynchronous work queue

nfs4: Return delegations when asked to

nfs4: Reply to incorrect and CB_NULL callback requests

nfs4: Add basic RPC level support for callbacks

nfs4: Do not open too much files on server

nfs4: Add ACCESS cache

nfs4: Move low level NFS4 code to Inode's base class

nfs4: Add directory and name basic implementation

nfs4: Rename Filehandle to FileHandle and Filesystem to FileSystem

nfs4: Add id mapper

nfs4: Move file handle recovery code out of Inode class

nfs4: Put file and dir specific code in separate files

nfs4: Add full support for lease migration

nfs4: Use MutexLocker for locking

nfs4: close*() should wake all blocked operations

nfs4: Add per server NFS4 objects

RPC::Server is now able to store RPC programs data.
NFS4Server objects are currently used mainly for managing client id.

nfs4: Add Request class for better handling of NFS4 requests

nfs4: Add stub Inode class, fix and extend Filesystem class

Additionally PUTFH support is added to both RequestBuilder and
ReplyInterpreter.

nfs4: Add stub Filesystem class and Mount method

nfs4: Add NFS4 reply interpreter

Currently supported operations are: ACCESS, GETATTR (partially), GETFH,
LOOKUP and PUTROOTFH.

nfs4: Add NFS4 request builder

Currently supports only the following operations: ACCESS, GETATTR, GETFH
LOOKUP and PUTROOTFH.

nfs4: Add RPC main communication code

RPC::Server represents a server client is connected to.
RPC::RequestManager stores all call that have been sent but no answer was
received so far.
RPC::ServerManager is responsible for reusing connections to the servers
and closing them when no longer needed.

nfs4: Add stub RPC reply code

RPC::Reply interprets incoming RPC replies. Currently only XID is
read.

nfs4: Add call generation code including authentication

RPC::Call generates a RPC call using provided RPC::Auth objects.
RPC::Auth supports AUTH_NONE and AUTH_SYS authentication protocols.

nfs4: Add XDR encoder and decoder

Base classes XDR::Stream and classes XDR::WriteStream and XDR::ReadStream
are added. They implement encoding and decoding XDR (RFC 4506) streams.
All data types used by RPC and NFS4 are supported.

nfs4: Add network code

Connection class supports sending and receiving RPC data using either
TCP or UDP as a transport protocol.

nfs4: Initial commit

Empty file system with only mounting supported.

nfs4: support hard links properly

The main purpose of this patch is to prevent VFS from removing a vnode to early
what might have happened if the NFS client knew it had more than one name but
then one of them was deleted. Moreover, all discovered and still valid names
are stored what may be useful in proper file handle recovery when they are
volatile.

This patch fixes both #9558 and #9561.

nfs4: Remove CacheRevalidator

There is no point in periodically revalidating all existing directory caches.
Directory snapshot can be revalidated when readdir is invoked.

nfs4: Introduce VnodeToInode mapping

VnodeToInode is another abstraction layer between VFS vnodes and NFS nodes.
It simplifies dealing with race conditions as well as faking some guarantees
VFS expects but NFS does not provide.

nfs4: Add asynchronous work queue

nfs4: Return delegations when asked to

nfs4: Reply to incorrect and CB_NULL callback requests

nfs4: Add basic RPC level support for callbacks

nfs4: Do not open too much files on server

nfs4: Add ACCESS cache

nfs4: Move low level NFS4 code to Inode's base class

nfs4: Add directory and name basic implementation

nfs4: Rename Filehandle to FileHandle and Filesystem to FileSystem

nfs4: Add id mapper

nfs4: Move file handle recovery code out of Inode class

nfs4: Put file and dir specific code in separate files

nfs4: Add full support for lease migration

nfs4: Use MutexLocker for locking

nfs4: close*() should wake all blocked operations

nfs4: Add per server NFS4 objects

RPC::Server is now able to store RPC programs data.
NFS4Server objects are currently used mainly for managing client id.

nfs4: Add Request class for better handling of NFS4 requests

nfs4: Add stub Inode class, fix and extend Filesystem class

Additionally PUTFH support is added to both RequestBuilder and
ReplyInterpreter.

nfs4: Add stub Filesystem class and Mount method

nfs4: Add NFS4 reply interpreter

Currently supported operations are: ACCESS, GETATTR (partially), GETFH,
LOOKUP and PUTROOTFH.

nfs4: Add NFS4 request builder

Currently supports only the following operations: ACCESS, GETATTR, GETFH
LOOKUP and PUTROOTFH.

nfs4: Add RPC main communication code

RPC::Server represents a server client is connected to.
RPC::RequestManager stores all call that have been sent but no answer was
received so far.
RPC::ServerManager is responsible for reusing connections to the servers
and closing them when no longer needed.

nfs4: Add stub RPC reply code

RPC::Reply interprets incoming RPC replies. Currently only XID is
read.

nfs4: Add call generation code including authentication

RPC::Call generates a RPC call using provided RPC::Auth objects.
RPC::Auth supports AUTH_NONE and AUTH_SYS authentication protocols.

nfs4: Add XDR encoder and decoder

Base classes XDR::Stream and classes XDR::WriteStream and XDR::ReadStream
are added. They implement encoding and decoding XDR (RFC 4506) streams.
All data types used by RPC and NFS4 are supported.

nfs4: Add network code

Connection class supports sending and receiving RPC data using either
TCP or UDP as a transport protocol.

nfs4: Initial commit

Empty file system with only mounting supported.