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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>
This commit is contained in:
Guoqing Jiang 2016-05-02 11:33:12 -04:00 committed by Shaohua Li
parent 5b0fb33e8a
commit 1535212c54
1 changed files with 10 additions and 3 deletions
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13
drivers/md/md-cluster.c
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@ -781,17 +781,24 @@ static int join(struct mddev *mddev, int nodes)
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);