drbd: Take a reference on tconn when finding a tconn by name

Rule #3 of kref.txt

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

3 files changed, 16 insertions, 7 deletions

diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index 3abf982ec559..7797879d3264 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -1381,7 +1381,7 @@ extern void drbd_delete_device(struct drbd_conf *mdev);
 
 struct drbd_tconn *conn_create(const char *name);
 extern void conn_destroy(struct kref *kref);
-struct drbd_tconn *conn_by_name(const char *name);
+struct drbd_tconn *conn_get_by_name(const char *name);
 extern void conn_free_crypto(struct drbd_tconn *tconn);
 
 extern int proc_details;
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 11427f59c5af..f0a0e1759bab 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -2362,7 +2362,7 @@ static void drbd_init_workqueue(struct drbd_work_queue* wq)
         INIT_LIST_HEAD(&wq->q);
 }
 
-struct drbd_tconn *conn_by_name(const char *name)
+struct drbd_tconn *conn_get_by_name(const char *name)
 {
         struct drbd_tconn *tconn;
 
@@ -2371,8 +2371,10 @@ struct drbd_tconn *conn_by_name(const char *name)
 
         down_read(&drbd_cfg_rwsem);
         list_for_each_entry(tconn, &drbd_tconns, all_tconn) {
-                if (!strcmp(tconn->name, name))
+                if (!strcmp(tconn->name, name)) {
+                        kref_get(&tconn->kref);
                         goto found;
+                }
         }
         tconn = NULL;
 found:
diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 23c34baa75a4..272c4a08ee42 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -195,7 +195,7 @@ static int drbd_adm_prepare(struct sk_buff *skb, struct genl_info *info,
 
         adm_ctx.minor = d_in->minor;
         adm_ctx.mdev = minor_to_mdev(d_in->minor);
-        adm_ctx.tconn = conn_by_name(adm_ctx.conn_name);
+        adm_ctx.tconn = conn_get_by_name(adm_ctx.conn_name);
 
         if (!adm_ctx.mdev && (flags & DRBD_ADM_NEED_MINOR)) {
                 drbd_msg_put_info("unknown minor");
@@ -223,8 +223,7 @@ static int drbd_adm_prepare(struct sk_buff *skb, struct genl_info *info,
                 drbd_msg_put_info("minor exists as different volume");
                 return ERR_INVALID_REQUEST;
         }
-        if (adm_ctx.mdev && !adm_ctx.tconn)
-                adm_ctx.tconn = adm_ctx.mdev->tconn;
+
         return NO_ERROR;
 
 fail:
@@ -238,6 +237,11 @@ static int drbd_adm_finish(struct genl_info *info, int retcode)
         struct nlattr *nla;
         const char *conn_name = NULL;
 
+        if (adm_ctx.tconn) {
+                kref_put(&adm_ctx.tconn->kref, &conn_destroy);
+                adm_ctx.tconn = NULL;
+        }
+
         if (!adm_ctx.reply_skb)
                 return -ENOMEM;
 
@@ -2748,10 +2752,13 @@ int drbd_adm_get_status_all(struct sk_buff *skb, struct netlink_callback *cb)
         if (!nla)
                 return -EINVAL;
         conn_name = nla_data(nla);
-        tconn = conn_by_name(conn_name);
+        tconn = conn_get_by_name(conn_name);
+
         if (!tconn)
                 return -ENODEV;
 
+        kref_put(&tconn->kref, &conn_destroy); /* get_one_status() (re)validates tconn by itself */
+
         /* prime iterators, and set "filter" mode mark:
          * only dump this tconn. */
         cb->args[0] = (long)tconn;