drbd: remove /proc/drbd before unregistering from netlink

There still exists a (theoretical) race on module unload, where
/proc/drbd may still exist, but the netlink callback has been
unregistered already, allowing drbdsetup to shout without listeners,
and get no reply.

Reorder remove_proc_entry and unregister of netlink callback.
drbdsetup first checks for existence of the proc entry,
and if that is missing, won't even try to contact the module.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

1 files changed, 11 insertions, 2 deletions

diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 8b8a38dc6492..150ed16d26ef 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -3174,11 +3174,20 @@ static void drbd_cleanup(void)
 
         unregister_reboot_notifier(&drbd_notifier);
 
+        /* first remove proc,
+         * drbdsetup uses it's presence to detect
+         * whether DRBD is loaded.
+         * If we would get stuck in proc removal,
+         * but have netlink already deregistered,
+         * some drbdsetup commands may wait forever
+         * for an answer.
+         */
+        if (drbd_proc)
+                remove_proc_entry("drbd", NULL);
+
         drbd_nl_cleanup();
 
         if (minor_table) {
-                if (drbd_proc)
-                        remove_proc_entry("drbd", NULL);
                 i = minor_count;
                 while (i--)
                         drbd_delete_device(i);