Re: [PATCH 2/3] NFSv4: Fix a race in the net namespace mount notification

[Stanislav Kinsbursky <skinsbursky@parallels.com>]

Looks good to me.

Acked-by: Stanislav Kinsbursky <skinsbursky@parallels.com>

23.05.2012 21:32, Trond Myklebust написал:
> Since the struct nfs_client gets added to the global nfs_client_list
> before it is initialised, it is possible that rpc_pipefs_event can
> end up trying to create idmapper entries on such a thing.
>
> The solution is to have the mount notification wait for the
> initialisation of each nfs_client to complete, and then to
> skip any entries for which the it failed.
>
> Reported-by: Stanislav Kinsbursky<skinsbursky@parallels.com>
> Signed-off-by: Trond Myklebust<Trond.Myklebust@netapp.com>
> Cc: Stanislav Kinsbursky<skinsbursky@parallels.com>
> ---
>   fs/nfs/client.c   |   16 +++++++++++++---
>   fs/nfs/idmap.c    |   15 +++++++++++++++
>   fs/nfs/internal.h |    1 +
>   3 files changed, 29 insertions(+), 3 deletions(-)
>
> diff --git a/fs/nfs/client.c b/fs/nfs/client.c
> index 78970a1..e6070ea 100644
> --- a/fs/nfs/client.c
> +++ b/fs/nfs/client.c
> @@ -504,6 +504,17 @@ static struct nfs_client *nfs_match_client(const struct nfs_client_initdata *dat
>   	return NULL;
>   }
>
> +static bool nfs_client_init_is_complete(const struct nfs_client *clp)
> +{
> +	return clp->cl_cons_state != NFS_CS_INITING;
> +}
> +
> +int nfs_wait_client_init_complete(const struct nfs_client *clp)
> +{
> +	return wait_event_killable(nfs_client_active_wq,
> +			nfs_client_init_is_complete(clp));
> +}
> +
>   /*
>    * Look up a client by IP address and protocol version
>    * - creates a new record if one doesn't yet exist
> @@ -564,8 +575,7 @@ found_client:
>   	if (new)
>   		nfs_free_client(new);
>
> -	error = wait_event_killable(nfs_client_active_wq,
> -				clp->cl_cons_state<  NFS_CS_INITING);
> +	error = nfs_wait_client_init_complete(clp);
>   	if (error<  0) {
>   		nfs_put_client(clp);
>   		return ERR_PTR(-ERESTARTSYS);
> @@ -1317,7 +1327,7 @@ static int nfs4_init_client_minor_version(struct nfs_client *clp)
>   		 * so that the client back channel can find the
>   		 * nfs_client struct
>   		 */
> -		clp->cl_cons_state = NFS_CS_SESSION_INITING;
> +		nfs_mark_client_ready(clp, NFS_CS_SESSION_INITING);
>   	}
>   #endif /* CONFIG_NFS_V4_1 */
>
> diff --git a/fs/nfs/idmap.c b/fs/nfs/idmap.c
> index 3e8edbe..6ca949b 100644
> --- a/fs/nfs/idmap.c
> +++ b/fs/nfs/idmap.c
> @@ -530,9 +530,24 @@ static struct nfs_client *nfs_get_client_for_event(struct net *net, int event)
>   	struct nfs_net *nn = net_generic(net, nfs_net_id);
>   	struct dentry *cl_dentry;
>   	struct nfs_client *clp;
> +	int err;
>
> +restart:
>   	spin_lock(&nn->nfs_client_lock);
>   	list_for_each_entry(clp,&nn->nfs_client_list, cl_share_link) {
> +		/* Wait for initialisation to finish */
> +		if (clp->cl_cons_state == NFS_CS_INITING) {
> +			atomic_inc(&clp->cl_count);
> +			spin_unlock(&nn->nfs_client_lock);
> +			err = nfs_wait_client_init_complete(clp);
> +			nfs_put_client(clp);
> +			if (err)
> +				return NULL;
> +			goto restart;
> +		}
> +		/* Skip nfs_clients that failed to initialise */
> +		if (clp->cl_cons_state<  0)
> +			continue;
>   		if (clp->rpc_ops !=&nfs_v4_clientops)
>   			continue;
>   		cl_dentry = clp->cl_idmap->idmap_pipe->dentry;
> diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
> index 00b66de..a23daa9 100644
> --- a/fs/nfs/internal.h
> +++ b/fs/nfs/internal.h
> @@ -167,6 +167,7 @@ extern struct nfs_server *nfs_clone_server(struct nfs_server *,
>   					   struct nfs_fh *,
>   					   struct nfs_fattr *,
>   					   rpc_authflavor_t);
> +extern int nfs_wait_client_init_complete(const struct nfs_client *clp);
>   extern void nfs_mark_client_ready(struct nfs_client *clp, int state);
>   extern struct nfs_client *nfs4_set_ds_client(struct nfs_client* mds_clp,
>   					     const struct sockaddr *ds_addr,