• Scott Mayhew's avatar
    nfs: fix a deadlock in nfs client initialization · c156618e
    Scott Mayhew authored
    The following deadlock can occur between a process waiting for a client
    to initialize in while walking the client list during nfsv4 server trunking
    detection and another process waiting for the nfs_clid_init_mutex so it
    can initialize that client:
    
    Process 1                               Process 2
    ---------                               ---------
    spin_lock(&nn->nfs_client_lock);
    list_add_tail(&CLIENTA->cl_share_link,
            &nn->nfs_client_list);
    spin_unlock(&nn->nfs_client_lock);
                                            spin_lock(&nn->nfs_client_lock);
                                            list_add_tail(&CLIENTB->cl_share_link,
                                                    &nn->nfs_client_list);
                                            spin_unlock(&nn->nfs_client_lock);
                                            mutex_lock(&nfs_clid_init_mutex);
                                            nfs41_walk_client_list(clp, result, cred);
                                            nfs_wait_client_init_complete(CLIENTA);
    (waiting for nfs_clid_init_mutex)
    
    Make sure nfs_match_client() only evaluates clients that have completed
    initialization in order to prevent that deadlock.
    
    This patch also fixes v4.0 trunking behavior by not marking the client
    NFS_CS_READY until the clientid has been confirmed.
    Signed-off-by: default avatarScott Mayhew <smayhew@redhat.com>
    Signed-off-by: default avatarAnna Schumaker <Anna.Schumaker@Netapp.com>
    c156618e
nfs4client.c 31.4 KB