On Wed, Jan 23, 2019 at 10:05:26AM +0000, Lu, Qian wrote:
> commit c156618e15101a9cc8c815108fec0300a0ec6637 upstream.
>
> 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: Scott Mayhew <smayhew@xxxxxxxxxx>
> Signed-off-by: Anna Schumaker <Anna.Schumaker@xxxxxxxxxx>
> Signed-off-by: Qian Lu <luqia@xxxxxxxxxx>
> ---
> fs/nfs/client.c | 11 +++++++++++
> fs/nfs/nfs4client.c | 17 +++++++++++++----
> 2 files changed, 24 insertions(+), 4 deletions(-)
>
> diff --git a/fs/nfs/client.c b/fs/nfs/client.c
> index 22880ef6d8dd..7d6ddfd60271 100644
> --- a/fs/nfs/client.c
> +++ b/fs/nfs/client.c
> @@ -291,12 +291,23 @@ static struct nfs_client *nfs_match_client(const struct nfs_client_initdata *dat
> const struct sockaddr *sap = data->addr;
> struct nfs_net *nn = net_generic(data->net, nfs_net_id);
>
> +again:
> list_for_each_entry(clp, &nn->nfs_client_list, cl_share_link) {
> const struct sockaddr *clap = (struct sockaddr *)&clp->cl_addr;
> /* Don't match clients that failed to initialise properly */
> if (clp->cl_cons_state < 0)
> continue;
>
> + /* If a client is still initializing then we need to wait */
> + if (clp->cl_cons_state > NFS_CS_READY) {
> + atomic_inc(&clp->cl_count);
> + spin_unlock(&nn->nfs_client_lock);
> + nfs_wait_client_init_complete(clp);
> + nfs_put_client(clp);
> + spin_lock(&nn->nfs_client_lock);
> + goto again;
> + }
> +
> /* Different NFS versions cannot share the same nfs_client */
> if (clp->rpc_ops != data->nfs_mod->rpc_ops)
> continue;
> diff --git a/fs/nfs/nfs4client.c b/fs/nfs/nfs4client.c
> index fed9c8005c17..8f96f6548dc8 100644
> --- a/fs/nfs/nfs4client.c
> +++ b/fs/nfs/nfs4client.c
> @@ -404,15 +404,19 @@ struct nfs_client *nfs4_init_client(struct nfs_client *clp,
> if (error < 0)
> goto error;
>
> - if (!nfs4_has_session(clp))
> - nfs_mark_client_ready(clp, NFS_CS_READY);
> -
> error = nfs4_discover_server_trunking(clp, &old);
> if (error < 0)
> goto error;
>
> - if (clp != old)
> + if (clp != old) {
> clp->cl_preserve_clid = true;
> + /*
> + * Mark the client as having failed initialization so other
> + * processes walking the nfs_client_list in nfs_match_client()
> + * won't try to use it.
> + */
> + nfs_mark_client_ready(clp, -EPERM);
> + }
> nfs_put_client(clp);
> clear_bit(NFS_CS_TSM_POSSIBLE, &clp->cl_flags);
> return old;
> @@ -539,6 +543,9 @@ int nfs40_walk_client_list(struct nfs_client *new,
> spin_lock(&nn->nfs_client_lock);
> list_for_each_entry(pos, &nn->nfs_client_list, cl_share_link) {
>
> + if (pos == new)
> + goto found;
> +
> status = nfs4_match_client(pos, new, &prev, nn);
> if (status < 0)
> goto out_unlock;
> @@ -559,6 +566,7 @@ int nfs40_walk_client_list(struct nfs_client *new,
> * way that a SETCLIENTID_CONFIRM to pos can succeed is
> * if new and pos point to the same server:
> */
> +found:
> atomic_inc(&pos->cl_count);
> spin_unlock(&nn->nfs_client_lock);
>
> @@ -572,6 +580,7 @@ int nfs40_walk_client_list(struct nfs_client *new,
> case 0:
> nfs4_swap_callback_idents(pos, new);
> pos->cl_confirm = new->cl_confirm;
> + nfs_mark_client_ready(pos, NFS_CS_READY);
>
> prev = NULL;
> *result = pos;
All of the tabs were turned into spaces here and this patch can not be
applied :(
Please fix up and resend.
thanks,
greg k-h
