lockfile: don't allow multiple instances of daemon to run

until now there is no check to defend on multiple runs of daemon within
the same node. This patch takes a non blocking lock on 'gluster-blockd.lock'
file, if it succeeds only then daemon is allowed to run, if there is
already a lock on lock-file (taken by some other instance of gluster-blockd)
we will exit.

This patch also renames GB_UNIX_ADDRESS  from gluster-block.socket to
gluster-blockd.socket, as that makes better sense.

Change-Id: I43b285f9da15d078fe3df4d231d0ef8d44272d8f
Signed-off-by: Prasanna Kumar Kalever <prasanna.kalever@redhat.com>

2 files changed, 38 insertions, 7 deletions

diff --git a/daemon/gluster-blockd.c b/daemon/gluster-blockd.c
index 399df1f..d4cae91 100644
--- a/daemon/gluster-blockd.c
+++ b/daemon/gluster-blockd.c
@@ -8,6 +8,8 @@
   cases as published by the Free Software Foundation.
 */
 
+
+# include  <fcntl.h>
 # include  <dirent.h>
 # include  <sys/stat.h>
 # include  <pthread.h>
@@ -168,26 +170,54 @@ glusterBlockServerThreadProc(void *vargp)
 int
 main (int argc, char **argv)
 {
+  int fd;
   pthread_t cli_thread;
   pthread_t server_thread;
+  struct flock lock = {0, };
+  int errnosv = 0;
+
 
   if (!glusterBlockLogdirCreate()) {
     return -1;
   }
 
-	pmap_unset(GLUSTER_BLOCK_CLI, GLUSTER_BLOCK_CLI_VERS);
+  /* is gluster-blockd running ? */
+  fd = creat(GB_LOCK_FILE, S_IRUSR | S_IWUSR);
+  if (fd == -1) {
+    LOG("mgmt", GB_LOG_ERROR, "creat(%s) failed[%s]",
+        GB_LOCK_FILE, strerror(errno));
+    goto out;
+  }
+
+  lock.l_type = F_WRLCK;
+  if (fcntl(fd, F_SETLK, &lock) == -1) {
+    errnosv = errno;
+    LOG("mgmt", GB_LOG_ERROR, "%s",
+        "gluster-blockd is already running...");
+    close(fd);
+    exit(errnosv);
+  }
+
+  pmap_unset(GLUSTER_BLOCK_CLI, GLUSTER_BLOCK_CLI_VERS);
   pmap_unset(GLUSTER_BLOCK, GLUSTER_BLOCK_VERS);
 
-  pthread_create(&cli_thread, NULL, glusterBlockCliThreadProc , NULL);
-  pthread_create(&server_thread, NULL, glusterBlockServerThreadProc , NULL);
+  pthread_create(&cli_thread, NULL, glusterBlockCliThreadProc, NULL);
+  pthread_create(&server_thread, NULL, glusterBlockServerThreadProc, NULL);
 
   pthread_join(cli_thread, NULL);
   pthread_join(server_thread, NULL);
 
+  LOG("mgmt", GB_LOG_ERROR, "svc_run returned (%s)", strerror (errno));
 
-  LOG("mgmt", GB_LOG_ERROR, "svc_run returned (%s)",
-      strerror (errno));
+  lock.l_type = F_UNLCK;
+  if (fcntl(fd, F_SETLK, &lock) == -1) {
+    LOG("mgmt", GB_LOG_ERROR, "fcntl(UNLCK) on pidfile %s failed[%s]",
+        GB_LOCK_FILE, strerror(errno));
+  }
 
-  exit (errno);
+  close(fd);
+
+ out:
+  exit (1);
   /* NOTREACHED */
 }
diff --git a/utils/common.h b/utils/common.h
index 6bb3273..c544029 100644
--- a/utils/common.h
+++ b/utils/common.h
@@ -17,7 +17,8 @@
 # define  GB_LOGDIR        DATADIR "/log/gluster-block"
 # define  GB_INFODIR       DATADIR "/run"
 
-# define  GB_UNIX_ADDRESS  GB_INFODIR "/gluster-block.socket"
+# define  GB_LOCK_FILE     GB_INFODIR "/gluster-blockd.lock"
+# define  GB_UNIX_ADDRESS  GB_INFODIR "/gluster-blockd.socket"
 # define  GB_TCP_PORT      24006
 
 # define  DAEMON_LOG_FILE  GB_LOGDIR "/gluster-blockd.log"