SUNRPC: fix races on PipeFS UMOUNT notifications
authorStanislav Kinsbursky <skinsbursky@parallels.com>
Wed, 26 Jun 2013 06:15:14 +0000 (10:15 +0400)
committerTrond Myklebust <Trond.Myklebust@netapp.com>
Fri, 28 Jun 2013 19:42:02 +0000 (15:42 -0400)
commitadb6fa7ffe9031857ec14b8aab75c9ab65556cbc
tree4d13bd7bf95d0c24478e95f429d6b4e6bbf5a6a5
parent384816051ca9125cd54750e59c780c2a2655fa4f
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>
net/sunrpc/clnt.c
net/sunrpc/rpc_pipe.c