On Tue, 2017-11-07 at 09:29 -0500, Scott Mayhew wrote:
> The following deadlock can occur between a process waiting for a
> client
> to initialize in while walking the client list 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_mut
> ex);
> 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.
>
> Signed-off-by: Scott Mayhew <smayhew@xxxxxxxxxx>
> ---
> fs/nfs/client.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/fs/nfs/client.c b/fs/nfs/client.c
> index 22880ef..8b093994 100644
> --- a/fs/nfs/client.c
> +++ b/fs/nfs/client.c
> @@ -291,12 +291,21 @@ 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 (clp->cl_minorversion > 0 &&
> + clp->cl_cons_state > NFS_CS_READY) {
> + spin_unlock(&nn->nfs_client_lock);
> + nfs_wait_client_init_complete(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;
Why the test for clp->cl_minorversion? What's so minor version specific
about any of this?
--
Trond Myklebust
Linux NFS client maintainer, PrimaryData
trond.myklebust@xxxxxxxxxxxxxxx
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