drbd: Proper locking for updates to net_conf under RCU

Removing the get_net_conf()/put_net_conf() functions

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

1 files changed, 30 insertions, 38 deletions

diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 34be84260bee..f86e882efcac 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -589,11 +589,12 @@ drbd_set_role(struct drbd_conf *mdev, enum drbd_role new_role, int force)
                         put_ldev(mdev);
                 }
         } else {
-                rcu_read_lock();
-                nc = rcu_dereference(mdev->tconn->net_conf);
+                mutex_lock(&mdev->tconn->net_conf_update);
+                nc = mdev->tconn->net_conf;
                 if (nc)
-                        nc->want_lose = 0;
-                rcu_read_unlock();
+                        nc->want_lose = 0; /* without copy; single bit op is atomic */
+                mutex_unlock(&mdev->tconn->net_conf_update);
+
                 set_disk_ro(mdev->vdisk, false);
                 if (get_ldev(mdev)) {
                         if (((mdev->state.conn < C_CONNECTED ||
@@ -1760,17 +1761,16 @@ int drbd_adm_net_opts(struct sk_buff *skb, struct genl_info *info)
 
         conn_reconfig_start(tconn);
 
-        rcu_read_lock();
-        old_conf = rcu_dereference(tconn->net_conf);
+        mutex_lock(&tconn->net_conf_update);
+        old_conf = tconn->net_conf;
 
         if (!old_conf) {
                 drbd_msg_put_info("net conf missing, try connect");
                 retcode = ERR_INVALID_REQUEST;
-                goto fail_rcu_unlock;
+                goto fail;
         }
 
         *new_conf = *old_conf;
-        rcu_read_unlock();
 
         err = net_conf_from_attrs_for_change(new_conf, info);
         if (err) {
@@ -1785,13 +1785,10 @@ int drbd_adm_net_opts(struct sk_buff *skb, struct genl_info *info)
 
         /* re-sync running */
         rsr = conn_resync_running(tconn);
-        rcu_read_lock();
-        old_conf = rcu_dereference(tconn->net_conf);
         if (rsr && old_conf && strcmp(new_conf->csums_alg, old_conf->csums_alg)) {
                 retcode = ERR_CSUMS_RESYNC_RUNNING;
-                goto fail_rcu_unlock;
+                goto fail;
         }
-        rcu_read_unlock();
 
         if (!rsr && new_conf->csums_alg[0]) {
                 csums_tfm = crypto_alloc_hash(new_conf->csums_alg, 0, CRYPTO_ALG_ASYNC);
@@ -1809,15 +1806,12 @@ int drbd_adm_net_opts(struct sk_buff *skb, struct genl_info *info)
 
         /* online verify running */
         ovr = conn_ov_running(tconn);
-        rcu_read_lock();
-        old_conf = rcu_dereference(tconn->net_conf);
-        if (ovr && old_conf) {
+        if (ovr) {
                 if (strcmp(new_conf->verify_alg, old_conf->verify_alg)) {
                         retcode = ERR_VERIFY_RUNNING;
-                        goto fail_rcu_unlock;
+                        goto fail;
                 }
         }
-        rcu_read_unlock();
 
         if (!ovr && new_conf->verify_alg[0]) {
                 verify_tfm = crypto_alloc_hash(new_conf->verify_alg, 0, CRYPTO_ALG_ASYNC);
@@ -1834,8 +1828,6 @@ int drbd_adm_net_opts(struct sk_buff *skb, struct genl_info *info)
         }
 
         rcu_assign_pointer(tconn->net_conf, new_conf);
-        synchronize_rcu();
-        kfree(old_conf);
 
         if (!rsr) {
                 crypto_free_hash(tconn->csums_tfm);
@@ -1848,15 +1840,21 @@ int drbd_adm_net_opts(struct sk_buff *skb, struct genl_info *info)
                 verify_tfm = NULL;
         }
 
+        mutex_unlock(&tconn->net_conf_update);
+        synchronize_rcu();
+        kfree(old_conf);
+
         if (tconn->cstate >= C_WF_REPORT_PARAMS)
                 drbd_send_sync_param(minor_to_mdev(conn_lowest_minor(tconn)));
 
- fail_rcu_unlock:
-        rcu_read_unlock();
+        goto done;
+
  fail:
+        mutex_unlock(&tconn->net_conf_update);
         crypto_free_hash(csums_tfm);
         crypto_free_hash(verify_tfm);
         kfree(new_conf);
+ done:
         conn_reconfig_done(tconn);
  out:
         drbd_adm_finish(info, retcode);
@@ -2032,32 +2030,26 @@ int drbd_adm_connect(struct sk_buff *skb, struct genl_info *info)
         }
 
         conn_flush_workqueue(tconn);
-        spin_lock_irq(&tconn->req_lock);
-        rcu_read_lock();
-        old_conf = rcu_dereference(tconn->net_conf);
-        if (old_conf != NULL) {
+
+        mutex_lock(&tconn->net_conf_update);
+        old_conf = tconn->net_conf;
+        if (old_conf) {
                 retcode = ERR_NET_CONFIGURED;
-                rcu_read_unlock();
-                spin_unlock_irq(&tconn->req_lock);
+                mutex_unlock(&tconn->net_conf_update);
                 goto fail;
         }
         rcu_assign_pointer(tconn->net_conf, new_conf);
 
-        crypto_free_hash(tconn->cram_hmac_tfm);
+        conn_free_crypto(tconn);
         tconn->cram_hmac_tfm = tfm;
-
-        crypto_free_hash(tconn->integrity_w_tfm);
         tconn->integrity_w_tfm = integrity_w_tfm;
-
-        crypto_free_hash(tconn->integrity_r_tfm);
         tconn->integrity_r_tfm = integrity_r_tfm;
+        tconn->int_dig_in = int_dig_in;
+        tconn->int_dig_vv = int_dig_vv;
 
-        kfree(tconn->int_dig_in);
-        kfree(tconn->int_dig_vv);
-        tconn->int_dig_in=int_dig_in;
-        tconn->int_dig_vv=int_dig_vv;
-        retcode = _conn_request_state(tconn, NS(conn, C_UNCONNECTED), CS_VERBOSE);
-        spin_unlock_irq(&tconn->req_lock);
+        mutex_unlock(&tconn->net_conf_update);
+
+        retcode = conn_request_state(tconn, NS(conn, C_UNCONNECTED), CS_VERBOSE);
 
         rcu_read_lock();
         idr_for_each_entry(&tconn->volumes, mdev, i) {