Make metadata updates from manage to monitor 'synchronous'

A metadata update may modify the data structure of the metadata
including freeing things, so it is not safe of the manager to touch
the metadata while an update is pending in the monitor.
So When an update has been submitted, don't do anything else in the
manager until it is complete.

Signed-off-by: NeilBrown <neilb@suse.de>

diff --git a/managemon.c b/managemon.c
index 0a251de72fe7d1ed30d540df7a67b1f69eeb6295..b211d8f446b17d6e2f5111c206bd0b8f51073dde 100644 (file)
--- a/managemon.c
+++ b/managemon.c
@@ -218,15 +218,6 @@ static void queue_metadata_update(struct metadata_update *mu)
        *qp = mu;
 }
 
-void wait_update_handled(void)
-{
-       /* Wait for any pending update to be handled by monitor.
-        * i.e. wait until update_queue is NULL
-        */
-       while (update_queue)
-               usleep(100 * 1000);
-}
-
 static void manage_container(struct mdstat_ent *mdstat,
                             struct supertype *container)
 {
@@ -272,7 +263,7 @@ static void manage_member(struct mdstat_ent *mdstat,
                struct metadata_update *updates = NULL;
                struct mdinfo *newdev;
                struct active_array *newa;
-               wait_update_handled();
+
                a->check_degraded = 0;
 
                /* The array may not be degraded, this is just a good time
@@ -467,13 +458,20 @@ static void handle_message(struct supertype *container, struct metadata_update *
        struct metadata_update *mu;
 
        if (msg->len == 0) {
-               int cnt = monitor_loop_cnt;
+               int cnt;
+               
+               while (update_queue_pending || update_queue) {
+                       check_update_queue(container);
+                       usleep(15*1000);
+               }
+
+               cnt = monitor_loop_cnt;
                if (cnt & 1)
                        cnt += 2; /* wait until next pselect */
                else
                        cnt += 3; /* wait for 2 pselects */
                wakeup_monitor();
-               wait_update_handled();
+
                while (monitor_loop_cnt - cnt < 0)
                        usleep(10 * 1000);
        } else {
@@ -536,20 +534,29 @@ void do_manager(struct supertype *container)
                if (exit_now)
                        exit(0);
 
-               mdstat = mdstat_read(1, 0);
-
-               manage(mdstat, container);
+               /* Can only 'manage' things if 'monitor' is not making
+                * structural changes to metadata, so need to check
+                * update_queue
+                */
+               if (update_queue == NULL) {
+                       mdstat = mdstat_read(1, 0);
 
-               read_sock(container);
+                       manage(mdstat, container);
 
-               free_mdstat(mdstat);
+                       read_sock(container);
 
+                       free_mdstat(mdstat);
+               }
                remove_old();
 
                check_update_queue(container);
 
                manager_ready = 1;
 
-               mdstat_wait_fd(container->sock, &set);
+               if (update_queue == NULL)
+                       mdstat_wait_fd(container->sock, &set);
+               else
+                       /* If an update is happening, just wait for signal */
+                       pselect(0, NULL, NULL, NULL, NULL, &set);
        } while(1);
 }