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authorStanislav Kinsbursky <skinsbursky@parallels.com>2013-06-26 10:15:14 +0400
committerTrond Myklebust <Trond.Myklebust@netapp.com>2013-06-28 15:42:02 -0400
commitadb6fa7ffe9031857ec14b8aab75c9ab65556cbc (patch)
tree4d13bd7bf95d0c24478e95f429d6b4e6bbf5a6a5
parent384816051ca9125cd54750e59c780c2a2655fa4f (diff)
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: Stanislav Kinsbursky <skinsbursky@parallels.com> Cc: stable@vger.kernel.org Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
-rw-r--r--net/sunrpc/clnt.c5
-rw-r--r--net/sunrpc/rpc_pipe.c2
2 files changed, 2 insertions, 5 deletions
diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index b827a4b91975..41f180c5a498 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -236,8 +236,6 @@ static struct rpc_clnt *rpc_get_client_for_event(struct net *net, int event)
continue;
if (rpc_clnt_skip_event(clnt, event))
continue;
- if (atomic_inc_not_zero(&clnt->cl_count) == 0)
- continue;
spin_unlock(&sn->rpc_client_lock);
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))) {
error = __rpc_pipefs_event(clnt, event, sb);
- rpc_release_client(clnt);
if (error)
break;
}
@@ -641,8 +638,8 @@ rpc_free_client(struct rpc_clnt *clnt)
rcu_dereference(clnt->cl_xprt)->servername);
if (clnt->cl_parent != clnt)
rpc_release_client(clnt->cl_parent);
- rpc_unregister_client(clnt);
rpc_clnt_remove_pipedir(clnt);
+ rpc_unregister_client(clnt);
rpc_free_iostats(clnt->cl_metrics);
kfree(clnt->cl_principal);
clnt->cl_metrics = NULL;
diff --git a/net/sunrpc/rpc_pipe.c b/net/sunrpc/rpc_pipe.c
index e02823bdfe98..4679df5a6d50 100644
--- a/net/sunrpc/rpc_pipe.c
+++ b/net/sunrpc/rpc_pipe.c
@@ -1166,12 +1166,12 @@ static void rpc_kill_sb(struct super_block *sb)
goto out;
}
sn->pipefs_sb = NULL;
- mutex_unlock(&sn->pipefs_sb_lock);
dprintk("RPC: sending pipefs UMOUNT notification for net %p%s\n",
net, NET_NAME(net));
blocking_notifier_call_chain(&rpc_pipefs_notifier_list,
RPC_PIPEFS_UMOUNT,
sb);
+ mutex_unlock(&sn->pipefs_sb_lock);
put_net(net);
out:
kill_litter_super(sb);