dlm: prevent connections during shutdown

During lowcomms shutdown, a new connection could possibly
be created, and attempt to use a workqueue that's been
destroyed.  Similarly, during startup, a new connection
could attempt to use a workqueue that's not been set up
yet.  Add a global variable to indicate when new connections
are allowed.

Based on patch by: Christine Caulfield <ccaulfie@redhat.com>

Reported-by: dann frazier <dann.frazier@canonical.com>
Reviewed-by: dann frazier <dann.frazier@canonical.com>
Signed-off-by: David Teigland <teigland@redhat.com>

1 files changed, 20 insertions, 8 deletions

diff --git a/fs/dlm/lowcomms.c b/fs/dlm/lowcomms.c
index 133ef6dc7cb7..5c1b0e38c7a4 100644
--- a/fs/dlm/lowcomms.c
+++ b/fs/dlm/lowcomms.c
@@ -142,6 +142,7 @@ struct writequeue_entry {
 
 static struct sockaddr_storage *dlm_local_addr[DLM_MAX_ADDR_COUNT];
 static int dlm_local_count;
+static int dlm_allow_conn;
 
 /* Work queues */
 static struct workqueue_struct *recv_workqueue;
@@ -710,6 +711,13 @@ static int tcp_accept_from_sock(struct connection *con)
         struct connection *newcon;
         struct connection *addcon;
 
+        mutex_lock(&connections_lock);
+        if (!dlm_allow_conn) {
+                mutex_unlock(&connections_lock);
+                return -1;
+        }
+        mutex_unlock(&connections_lock);
+
         memset(&peeraddr, 0, sizeof(peeraddr));
         result = sock_create_kern(dlm_local_addr[0]->ss_family, SOCK_STREAM,
                                   IPPROTO_TCP, &newsock);
@@ -1503,6 +1511,7 @@ void dlm_lowcomms_stop(void)
            socket activity.
         */
         mutex_lock(&connections_lock);
+        dlm_allow_conn = 0;
         foreach_conn(stop_conn);
         mutex_unlock(&connections_lock);
 
@@ -1530,7 +1539,7 @@ int dlm_lowcomms_start(void)
         if (!dlm_local_count) {
                 error = -ENOTCONN;
                 log_print("no local IP address has been set");
-                goto out;
+                goto fail;
         }
 
         error = -ENOMEM;
@@ -1538,7 +1547,13 @@ int dlm_lowcomms_start(void)
                                       __alignof__(struct connection), 0,
                                       NULL);
         if (!con_cache)
-                goto out;
+                goto fail;
+
+        error = work_start();
+        if (error)
+                goto fail_destroy;
+
+        dlm_allow_conn = 1;
 
         /* Start listening */
         if (dlm_config.ci_protocol == 0)
@@ -1548,20 +1563,17 @@ int dlm_lowcomms_start(void)
         if (error)
                 goto fail_unlisten;
 
-        error = work_start();
-        if (error)
-                goto fail_unlisten;
-
         return 0;
 
 fail_unlisten:
+        dlm_allow_conn = 0;
         con = nodeid2con(0,0);
         if (con) {
                 close_connection(con, false);
                 kmem_cache_free(con_cache, con);
         }
+fail_destroy:
         kmem_cache_destroy(con_cache);
-
-out:
+fail:
         return error;
 }