[Cluster-devel] Re: [RFC]Drop unused plock resource when no other plock request comes

[David Teigland <teigland@redhat.com>]

On Tue, Aug 25, 2009 at 11:10:03AM +0800, Jiaju Zhang wrote:
> On Mon, Aug 24, 2009 at 10:31 PM, David Teigland <teigland@redhat.com>wrote:
> 
> >
> > You're correct; yes the daemon could easily be changed to drop resources
> > when
> > there's no locking activity.  We'd just set a poll timeout when
> > plock_resources is non-empty and call drop_resources() if it times out.
> >
> > (If you simply want to work around this, you can write a little program to
> > lock a file on the fs to trigger the drop.)
> >
> > Dave
> 
> 
> Many thanks for your guidance :-)
> So I write a patch to try to fix this. Review and comments are welcome.

Thanks, that looks like it would do the job, but the code is a little
complicated.  Here's a simpler patch, I've not tried it so it may not work :)

Dave


diff --git a/group/dlm_controld/dlm_daemon.h b/group/dlm_controld/dlm_daemon.h
index df2e148..18479d7 100644
--- a/group/dlm_controld/dlm_daemon.h
+++ b/group/dlm_controld/dlm_daemon.h
@@ -73,6 +73,7 @@ extern int poll_fencing;
 extern int poll_quorum;
 extern int poll_fs;
 extern int poll_ignore_plock;
+extern int poll_drop_plock;
 extern int plock_fd;
 extern int plock_ci;
 extern struct list_head lockspaces;
@@ -296,6 +297,7 @@ void process_netlink(int ci);
 int setup_plocks(void);
 void close_plocks(void);
 void process_plocks(int ci);
+void drop_resources_all(void);
 int limit_plocks(void);
 void receive_plock(struct lockspace *ls, struct dlm_header *hd, int len);
 void receive_own(struct lockspace *ls, struct dlm_header *hd, int len);
diff --git a/group/dlm_controld/main.c b/group/dlm_controld/main.c
index 93b40f8..75ee55d 100644
--- a/group/dlm_controld/main.c
+++ b/group/dlm_controld/main.c
@@ -1011,6 +1011,13 @@ static void loop(void)
 			}
 			poll_timeout = 1000;
 		}
+
+		if (poll_drop_plock) {
+			drop_resources_all();
+			if (poll_drop_plock)
+				poll_timeout = 1000;
+		}
+
 		query_unlock();
 	}
  out:
@@ -1310,6 +1317,7 @@ int poll_fencing;
 int poll_quorum;
 int poll_fs;
 int poll_ignore_plock;
+int poll_drop_plock;
 int plock_fd;
 int plock_ci;
 struct list_head lockspaces;
diff --git a/group/dlm_controld/plock.c b/group/dlm_controld/plock.c
index 3d4431e..197b15c 100644
--- a/group/dlm_controld/plock.c
+++ b/group/dlm_controld/plock.c
@@ -1351,8 +1351,20 @@ static int drop_resources(struct lockspace *ls)
 	struct timeval now;
 	int count = 0;
 
+	if (!cfgd_plock_ownership)
+		return 0;
+
+	if (list_empty(&ls->plock_resources))
+		return 0;
+
 	gettimeofday(&now, NULL);
 
+	if (time_diff_ms(&ls->drop_resources_last, &now) <
+	    		 cfgd_drop_resources_time)
+		return 1;
+
+	ls->drop_resources_last = now;
+
 	/* try to drop the oldest, unused resources */
 
 	list_for_each_entry_reverse(r, &ls->plock_resources, list) {
@@ -1376,7 +1388,21 @@ static int drop_resources(struct lockspace *ls)
 		}
 	}
 
-	return 0;
+	return 1;
+}
+
+void drop_resources_all(void)
+{
+	struct lockspace *ls;
+	int rv = 0;
+
+	poll_drop_plock = 0;
+
+	list_for_each_entry(ls, &lockspaces, list) {
+		rv = drop_resources(ls);
+		if (rv)
+			poll_drop_plock = 1;
+	}
 }
 
 int limit_plocks(void)
@@ -1495,13 +1521,8 @@ void process_plocks(int ci)
 		save_pending_plock(ls, r, &info);
 	}
 
-	if (cfgd_plock_ownership &&
-	    time_diff_ms(&ls->drop_resources_last, &now) >=
-	    		 cfgd_drop_resources_time) {
-		ls->drop_resources_last = now;
-		drop_resources(ls);
-	}
-
+	if (cfgd_plock_ownership && !list_empty(&ls->plock_resources))
+		poll_drop_plock = 1;
 	return;
 
  fail: