Staging: Pohmelfs: Added IO permissions and priorities.

Signed-off-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

Documentation/filesystems/pohmelfs/design_notes.txt

@@ -56,9 +56,10 @@ workloads and can fully utilize the bandwidth to the servers when doing bulk
 data transfers.
 
 POHMELFS clients operate with a working set of servers and are capable of balancing read-only
-operations (like lookups or directory listings) between them.
+operations (like lookups or directory listings) between them according to IO priorities.
 Administrators can add or remove servers from the set at run-time via special commands (described
-in Documentation/pohmelfs/info.txt file). Writes are replicated to all servers.
+in Documentation/pohmelfs/info.txt file). Writes are replicated to all servers, which are connected
+with write permission turned on. IO priority and permissions can be changed in run-time.
 
 POHMELFS is capable of full data channel encryption and/or strong crypto hashing.
 One can select any kernel supported cipher, encryption mode, hash type and operation mode

Documentation/filesystems/pohmelfs/info.txt

@@ -1,6 +1,8 @@
 POHMELFS usage information.
 
-Mount options:
+Mount options.
+All but index, number of crypto threads and maximum IO size can changed via remount.
+
 idx=%u
  Each mountpoint is associated with a special index via this option.
  Administrator can add or remove servers from the given index, so all mounts,
@@ -52,16 +54,27 @@ mcache_timeout=%u
 
 Usage examples.
 
-Add (or remove if it already exists) server server1.net:1025 into the working set with index $idx
+Add server server1.net:1025 into the working set with index $idx
 with appropriate hash algorithm and key file and cipher algorithm, mode and key file:
-$cfg -a server1.net -p 1025 -i $idx -K $hash_key -k $cipher_key
+$cfg A add -a server1.net -p 1025 -i $idx -K $hash_key -k $cipher_key
 
 Mount filesystem with given index $idx to /mnt mountpoint.
 Client will connect to all servers specified in the working set via previous command:
 mount -t pohmel -o idx=$idx q /mnt
 
-One can add or remove servers from working set after mounting too.
+Change permissions to read-only (-I 1 option, '-I 2' - write-only, 3 - rw):
+$cfg A modify -a server1.net -p 1025 -i $idx -I 1
 
+Change IO priority to 123 (node with the highest priority gets read requests).
+$cfg A modify -a server1.net -p 1025 -i $idx -P 123
+
+One can check currect status of all connections in the mountstats file:
+# cat /proc/$PID/mountstats
+...
+device none mounted on /mnt with fstype pohmel
+idx addr(:port) socket_type protocol active priority permissions
+0 server1.net:1026 1 6 1 250 1
+0 server2.net:1025 1 6 1 123 3
 
 Server installation.