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Commit adb6fa7f authored by Stanislav Kinsbursky's avatar Stanislav Kinsbursky Committed by Trond Myklebust
Browse files

SUNRPC: fix races on PipeFS UMOUNT notifications 



CPU#0                                   CPU#1
-----------------------------           -----------------------------
rpc_kill_sb
sn->pipefs_sb = NULL                    rpc_release_client
(UMOUNT_EVENT)                          rpc_free_auth
rpc_pipefs_event
rpc_get_client_for_event
!atomic_inc_not_zero(cl_count)
<skip the client>
                                        atomic_inc(cl_count)
                                        rpc_free_client
                                        rpc_clnt_remove_pipedir
                                        <skip client dir removing>

To fix this, this patch does the following:

1) Calls RPC_PIPEFS_UMOUNT notification with sn->pipefs_sb_lock being held.
2) Removes SUNRPC client from the list AFTER pipes destroying.
3) Doesn't hold RPC client on notification: if client in the list, then it
can't be destroyed while sn->pipefs_sb_lock in hold by notification caller.

Signed-off-by: default avatarStanislav Kinsbursky <skinsbursky@parallels.com>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarTrond Myklebust <Trond.Myklebust@netapp.com>
parent 38481605

net/sunrpc/clnt.c

+1 −4
Original line number Original line Diff line number Diff line
@@ -236,8 +236,6 @@ static struct rpc_clnt *rpc_get_client_for_event(struct net *net, int event) 
			continue;

			continue;

		if (rpc_clnt_skip_event(clnt, event))

		if (rpc_clnt_skip_event(clnt, event))

			continue;

			continue;

		if (atomic_inc_not_zero(&clnt->cl_count) == 0)

			continue;

		spin_unlock(&sn->rpc_client_lock);

		spin_unlock(&sn->rpc_client_lock);

		return clnt;

		return clnt;

	}

	}
@@ -254,7 +252,6 @@ static int rpc_pipefs_event(struct notifier_block *nb, unsigned long event, 




	while ((clnt = rpc_get_client_for_event(sb->s_fs_info, event))) {

	while ((clnt = rpc_get_client_for_event(sb->s_fs_info, event))) {

		error = __rpc_pipefs_event(clnt, event, sb);

		error = __rpc_pipefs_event(clnt, event, sb);

		rpc_release_client(clnt);

		if (error)

		if (error)

			break;

			break;

	}

	}
@@ -641,8 +638,8 @@ rpc_free_client(struct rpc_clnt *clnt) 
			rcu_dereference(clnt->cl_xprt)->servername);

			rcu_dereference(clnt->cl_xprt)->servername);

	if (clnt->cl_parent != clnt)

	if (clnt->cl_parent != clnt)

		rpc_release_client(clnt->cl_parent);

		rpc_release_client(clnt->cl_parent);

	rpc_unregister_client(clnt);

	rpc_clnt_remove_pipedir(clnt);

	rpc_clnt_remove_pipedir(clnt);

	rpc_unregister_client(clnt);

	rpc_free_iostats(clnt->cl_metrics);

	rpc_free_iostats(clnt->cl_metrics);

	kfree(clnt->cl_principal);

	kfree(clnt->cl_principal);

	clnt->cl_metrics = NULL;

	clnt->cl_metrics = NULL;

net/sunrpc/rpc_pipe.c

+1 −1
Original line number Original line Diff line number Diff line
@@ -1166,12 +1166,12 @@ static void rpc_kill_sb(struct super_block *sb) 
		goto out;

		goto out;

	}

	}

	sn->pipefs_sb = NULL;

	sn->pipefs_sb = NULL;

	mutex_unlock(&sn->pipefs_sb_lock);

	dprintk("RPC:       sending pipefs UMOUNT notification for net %p%s\n",

	dprintk("RPC:       sending pipefs UMOUNT notification for net %p%s\n",

		net, NET_NAME(net));

		net, NET_NAME(net));

	blocking_notifier_call_chain(&rpc_pipefs_notifier_list,

	blocking_notifier_call_chain(&rpc_pipefs_notifier_list,

					   RPC_PIPEFS_UMOUNT,

					   RPC_PIPEFS_UMOUNT,

					   sb);

					   sb);

	mutex_unlock(&sn->pipefs_sb_lock);

	put_net(net);

	put_net(net);

out:

out:

	kill_litter_super(sb);

	kill_litter_super(sb);