md-cluster: fix locking when node joins cluster during message broadcast
If a node joins the cluster while a message broadcast
is under way, a lock issue could happen as follows.
For a cluster which included two nodes, if node A is
calling __sendmsg before up-convert CR to EX on ack,
and node B released CR on ack. But if a new node C
joins the cluster and it doesn't receive the message
which A sent before, so it could hold CR on ack before
A up-convert CR to EX on ack.
So a node joining the cluster should get an EX lock on
the "token" first to ensure no broadcast is ongoing,
then release it after held CR on ack.
Reviewed-by: NeilBrown <neilb@suse.com>
Signed-off-by: Guoqing Jiang <gqjiang@suse.com>
Signed-off-by: Shaohua Li <shli@fb.com>
diff --git a/drivers/md/md-cluster.c b/drivers/md/md-cluster.c
index 76f88f7..30f1160 100644
--- a/drivers/md/md-cluster.c
+++ b/drivers/md/md-cluster.c
@@ -781,17 +781,24 @@
cinfo->token_lockres = lockres_init(mddev, "token", NULL, 0);
if (!cinfo->token_lockres)
goto err;
- cinfo->ack_lockres = lockres_init(mddev, "ack", ack_bast, 0);
- if (!cinfo->ack_lockres)
- goto err;
cinfo->no_new_dev_lockres = lockres_init(mddev, "no-new-dev", NULL, 0);
if (!cinfo->no_new_dev_lockres)
goto err;
+ ret = dlm_lock_sync(cinfo->token_lockres, DLM_LOCK_EX);
+ if (ret) {
+ ret = -EAGAIN;
+ pr_err("md-cluster: can't join cluster to avoid lock issue\n");
+ goto err;
+ }
+ cinfo->ack_lockres = lockres_init(mddev, "ack", ack_bast, 0);
+ if (!cinfo->ack_lockres)
+ goto err;
/* get sync CR lock on ACK. */
if (dlm_lock_sync(cinfo->ack_lockres, DLM_LOCK_CR))
pr_err("md-cluster: failed to get a sync CR lock on ACK!(%d)\n",
ret);
+ dlm_unlock_sync(cinfo->token_lockres);
/* get sync CR lock on no-new-dev. */
if (dlm_lock_sync(cinfo->no_new_dev_lockres, DLM_LOCK_CR))
pr_err("md-cluster: failed to get a sync CR lock on no-new-dev!(%d)\n", ret);