protocol/client,server: fcntl lock self healing.

Currently(with out this patch), on a disconnect the server cleans up
the transport which inturn closes the fd's and releases the locks acquired on
those fd's by that client. On a reconnect, client just reopens the fd's but
doesn't reacquire the locks. The application that had previously acquired
the locks still is under the assumption that it is the owner of those locks
which might have been granted to other clients(if they request) by the server
leading to data corruption.

This patch allows the client to reacquire the fcntl locks (held on the fd's)
during client-server handshake.

* The server identifies the client via process-uuid-xl (which is a combination
  of uuid and client-protocol name, it is assumed to be unique) and lk-version
  number.

* The client maintains a list of process-uuid-xl, lk-version pair for each
  accepted connection. On a connect, the server traverses the list for a
  matching pair, if a matching pair is not found the the server returns
  lk-version with value 0, else it returns the lk-version it has in store.

* On a disconnect, the server and client enter grace period, and on the
  completion of the grace period, the client bumps up its lk-version number
  (which means, it will reacquire the locks the next time) and the server will
  distroy the connection. If reconnection happens within the grace period, the
  server will find the matching (process-uuid-xl, lk-version) pair in its list
  which guarantees that the fd's and there corresponding locks are still valid
  for this client.

Configurable options:
  To set grace-timeout, the following options are
    option server.grace-timeout value
    option client.grace-timeout value

  To enable or disable the lk-heal,
    option lk-heal [on|off]

gluster volume set command can be used to configurable options
Change-Id: Id677ef1087b300d649f278b8b2aa0d94eae85ed2
BUG: 795386
Signed-off-by: Mohammed Junaid <junaid@redhat.com>
Reviewed-on: http://review.gluster.com/2766
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vijay@gluster.com>

1 files changed, 72 insertions, 0 deletions

diff --git a/libglusterfs/src/fd-lk.h b/libglusterfs/src/fd-lk.h
new file mode 100644
index 00000000000..3e419e14377
--- /dev/null
+++ b/libglusterfs/src/fd-lk.h
@@ -0,0 +1,72 @@
+/*
+  Copyright (c) 2011-2012 Gluster, Inc. <http://www.gluster.com>
+  This file is part of GlusterFS.
+
+  GlusterFS is free software; you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published
+  by the Free Software Foundation; either version 3 of the License,
+  or (at your option) any later version.
+
+  GlusterFS is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+  General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with this program.  If not, see
+  <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef _FD_LK_H
+#define _FD_LK_H
+
+#include "fd.h"
+#include "locking.h"
+#include "list.h"
+#include "logging.h"
+#include "mem-pool.h"
+#include "mem-types.h"
+#include "glusterfs.h"
+
+#define get_lk_type(type)                                               \
+        type == F_UNLCK ? "F_UNLCK" : (type == F_RDLCK ? "F_RDLCK" : "F_WRLCK")
+
+#define get_lk_cmd(cmd)                                                 \
+        cmd == F_SETLKW ? "F_SETLKW" : (cmd == F_SETLK ? "F_SETLK" : "F_GETLK")
+
+struct _fd;
+
+struct fd_lk_ctx {
+        struct list_head lk_list;
+        int   ref;
+        gf_lock_t lock;
+};
+typedef struct fd_lk_ctx fd_lk_ctx_t;
+
+struct fd_lk_ctx_node {
+        int32_t            cmd;
+        struct gf_flock    user_flock;
+        off_t              fl_start;
+        off_t              fl_end;
+        short              fl_type;
+        struct list_head   next;
+};
+typedef struct fd_lk_ctx_node fd_lk_ctx_node_t;
+
+fd_lk_ctx_t *
+_fd_lk_ctx_ref (fd_lk_ctx_t *lk_ctx);
+
+fd_lk_ctx_t *
+fd_lk_ctx_ref (fd_lk_ctx_t *lk_ctx);
+
+fd_lk_ctx_t *
+fd_lk_ctx_create ();
+
+int
+fd_lk_insert_and_merge (struct _fd *lk_ctx, int32_t cmd,
+                        struct gf_flock *flock);
+
+int
+fd_lk_ctx_unref (fd_lk_ctx_t *lk_ctx);
+
+#endif /* _FD_LK_H */