Overall, the aim of this patch is to change the result of an nfs
op depending on whether the underlying volume is up or down
as notified by CHILD_UP and CHILD_DOWN events.

This patch contains three intertwined changes:
o Only when the lookup on the root of a volume is successful does gnfs now
export the subvolume. Till now the result of the lookup was not used to
determine whether we should export that volume. Not accounting for root lookup
failure resulted in ESTALEs on first access because some children of distribute
were down at the time of the root lookup.

o Only when lookups on all the subvolumes have succeeded are
these exports enabled through NFS.

o When a child of say distribute goes down, on CHILD_DOWN event nfs will
ignore all incoming requests from the client because ignoring these
will prevent ESTALEs for those requests and in the hope that ignoring the
requests will make the client retransmit. There are risks in this approach
absent the DRC but we're willing to live with that for now.
When a child goes down, the mount exports list will continue to show it
but mount requests will be denied.

Signed-off-by: Shehjar Tikoo <shehjart@gluster.com>
Signed-off-by: Vijay Bellur <vijay@dev.gluster.com>

BUG: 1643 (Initial requests after mount ESTALE if DHT subvolumes connect after nfs startup)
URL: http://bugs.gluster.com/cgi-bin/bugzilla3/show_bug.cgi?id=1643

Signed-off-by: Shehjar Tikoo <shehjart@gluster.com>
Signed-off-by: Vijay Bellur <vijay@dev.gluster.com>

BUG: 971 (dynamic volume management)
URL: http://bugs.gluster.com/cgi-bin/bugzilla3/show_bug.cgi?id=971

- incorporate usage of uuid (gfid) as the key for finding inodes
- deprecate inode number/generation number based inode_get
- undo code specific to generation numbers (attic list etc.)

Signed-off-by: Anand V. Avati <avati@blackhole.gluster.com>
Signed-off-by: Anand V. Avati <avati@amp.gluster.com>
Signed-off-by: Vijay Bellur <vijay@dev.gluster.com>

BUG: 971 (dynamic volume management)
URL: http://bugs.gluster.com/cgi-bin/bugzilla3/show_bug.cgi?id=971

This is plain wrong. this must always be the xlator that receives the callback.
Use cookie to access the child subvolume on which the fop was issued.

Signed-off-by: Shehjar Tikoo <shehjart@gluster.com>
Signed-off-by: Vijay Bellur <vijay@dev.gluster.com>

BUG: 1410 (nfs uses this for child translator during frame creation)
URL: http://bugs.gluster.com/cgi-bin/bugzilla3/show_bug.cgi?id=1410

Signed-off-by: Kaushik BV <kaushikbv@gluster.com>
Signed-off-by: Anand V. Avati <avati@dev.gluster.com>

BUG: 1117 ()
URL: http://bugs.gluster.com/cgi-bin/bugzilla3/show_bug.cgi?id=1117

Signed-off-by: Shehjar Tikoo <shehjart@gluster.com>
Signed-off-by: Anand V. Avati <avati@dev.gluster.com>

BUG: 1274 (nfs fails to start)
URL: http://bugs.gluster.com/cgi-bin/bugzilla3/show_bug.cgi?id=1274

nfsx has followed traditional approach of exporting whole volumes
as NFS exports. The Platform requires and some users have approached us for
introducing exports of only specific directories instead of full Gluster
volumes. This commit introduces this support through two nfsx options:

Option 1:

=========
option nfs3.<volume-name>.export-dir <subdir1-in-vol>,<subdir2-in-vol>,..<subdirN-in-vol>

export-dir will allow the export of a particular dir as a single export
by itself. For eg.:

volume posix
        type storage/posix
        option directory /export/
end-volume

volume posix-ac
        type features/access-control
        subvolumes posix
end-volume

volume nfs
        type nfs/server
        subvolumes posix-ac
        option rpc-auth.addr.allow *
        option nfs3.posix-ac.export-dir /homes/shehjart
end-volume

A comma separate list of sub-directories will set up those dirs as separated exports.
At the nfs client, the mount command will be:

$ mount <nfsserver>:/posix-ac/homes/shehjart /mnt

Option 2:
=========
option nfs3.<volume-name>.export-volumes <on|off>

There can be situations where users only want the directory level
exports and require that volume exports be completely disabled. The
above option allows us to do this. By default, volume exports are
enabled. From the earlier example, replacing <volume-name> with
posix-ac, will disable mounting of the posix-ac volume as a whole.

Signed-off-by: Shehjar Tikoo <shehjart@gluster.com>
Signed-off-by: Anand V. Avati <avati@dev.gluster.com>

BUG: 989 (Support directory exports in nfsx)
URL: http://bugs.gluster.com/cgi-bin/bugzilla3/show_bug.cgi?id=989

In case the nfs client sends an unmount request for a volume
that does not exist anymore.

Signed-off-by: Shehjar Tikoo <shehjart@gluster.com>
Signed-off-by: Anand V. Avati <avati@dev.gluster.com>

BUG: 961 (Unmount with invalid export crashes nfsx)
URL: http://bugs.gluster.com/cgi-bin/bugzilla3/show_bug.cgi?id=961

Till now nfsx would crash if the export was mounted simply as
<volname> as compared to the traditional method of /<volname>.

Signed-off-by: Shehjar Tikoo <shehjart@gluster.com>
Signed-off-by: Anand V. Avati <avati@dev.gluster.com>

BUG: 944 (vmware unmount crashes nfsx)
URL: http://bugs.gluster.com/cgi-bin/bugzilla3/show_bug.cgi?id=944

Memory accounting Changes. Thanks to Vinayak Hegde and Csaba Henk for their
contributions.

Signed-off-by: Vijay Bellur <vijay@gluster.com>
Signed-off-by: Anand V. Avati <avati@dev.gluster.com>

BUG: 329 (Replacing memory allocation functions with mem-type functions)
URL: http://bugs.gluster.com/cgi-bin/bugzilla3/show_bug.cgi?id=329