[PATCH 1/3] NFSv4.1: Fix session initialisation races

[PATCH 1/3] NFSv4.1: Fix session initialisation races

[Trond Myklebust]

Session initialisation is not complete until the lease manager
has run. We need to ensure that both nfs4_init_session and
nfs4_init_ds_session do so, and that they check for any resulting
errors in clp->cl_cons_state.

Only after this is done, can nfs4_ds_connect check the contents
of clp->cl_exchange_flags.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: Andy Adamson <andros@netapp.com>
---
 fs/nfs/client.c            |   16 ---------
 fs/nfs/internal.h          |    3 +-
 fs/nfs/nfs4filelayoutdev.c |   23 +------------
 fs/nfs/nfs4proc.c          |   77 ++++++++++++++++++++++++++++---------------
 4 files changed, 52 insertions(+), 67 deletions(-)

diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index 60f7e4e..78970a1 100644
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -593,22 +593,6 @@ void nfs_mark_client_ready(struct nfs_client *clp, int state)
 }
 
 /*
- * With sessions, the client is not marked ready until after a
- * successful EXCHANGE_ID and CREATE_SESSION.
- *
- * Map errors cl_cons_state errors to EPROTONOSUPPORT to indicate
- * other versions of NFS can be tried.
- */
-int nfs4_check_client_ready(struct nfs_client *clp)
-{
-	if (!nfs4_has_session(clp))
-		return 0;
-	if (clp->cl_cons_state < NFS_CS_READY)
-		return -EPROTONOSUPPORT;
-	return 0;
-}
-
-/*
  * Initialise the timeout values for a connection
  */
 static void nfs_init_timeout_values(struct rpc_timeout *to, int proto,
diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
index b777bda..00b66de 100644
--- a/fs/nfs/internal.h
+++ b/fs/nfs/internal.h
@@ -168,7 +168,6 @@ extern struct nfs_server *nfs_clone_server(struct nfs_server *,
 					   struct nfs_fattr *,
 					   rpc_authflavor_t);
 extern void nfs_mark_client_ready(struct nfs_client *clp, int state);
-extern int nfs4_check_client_ready(struct nfs_client *clp);
 extern struct nfs_client *nfs4_set_ds_client(struct nfs_client* mds_clp,
 					     const struct sockaddr *ds_addr,
 					     int ds_addrlen, int ds_proto);
@@ -237,7 +236,7 @@ extern const u32 nfs41_maxwrite_overhead;
 extern struct rpc_procinfo nfs4_procedures[];
 #endif
 
-extern int nfs4_init_ds_session(struct nfs_client *clp);
+extern int nfs4_init_ds_session(struct nfs_client *, unsigned long);
 
 /* proc.c */
 void nfs_close_context(struct nfs_open_context *ctx, int is_sync);
diff --git a/fs/nfs/nfs4filelayoutdev.c b/fs/nfs/nfs4filelayoutdev.c
index c9cff9a..0764c98 100644
--- a/fs/nfs/nfs4filelayoutdev.c
+++ b/fs/nfs/nfs4filelayoutdev.c
@@ -176,28 +176,7 @@ nfs4_ds_connect(struct nfs_server *mds_srv, struct nfs4_pnfs_ds *ds)
 		goto out;
 	}
 
-	if ((clp->cl_exchange_flags & EXCHGID4_FLAG_MASK_PNFS) != 0) {
-		if (!is_ds_client(clp)) {
-			status = -ENODEV;
-			goto out_put;
-		}
-		ds->ds_clp = clp;
-		dprintk("%s [existing] server=%s\n", __func__,
-			ds->ds_remotestr);
-		goto out;
-	}
-
-	/*
-	 * Do not set NFS_CS_CHECK_LEASE_TIME instead set the DS lease to
-	 * be equal to the MDS lease. Renewal is scheduled in create_session.
-	 */
-	spin_lock(&mds_srv->nfs_client->cl_lock);
-	clp->cl_lease_time = mds_srv->nfs_client->cl_lease_time;
-	spin_unlock(&mds_srv->nfs_client->cl_lock);
-	clp->cl_last_renewal = jiffies;
-
-	/* New nfs_client */
-	status = nfs4_init_ds_session(clp);
+	status = nfs4_init_ds_session(clp, mds_srv->nfs_client->cl_lease_time);
 	if (status)
 		goto out_put;
 
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 99650aa..272c4ad 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -5605,53 +5605,76 @@ int nfs4_proc_destroy_session(struct nfs4_session *session)
 	return status;
 }
 
+/*
+ * With sessions, the client is not marked ready until after a
+ * successful EXCHANGE_ID and CREATE_SESSION.
+ *
+ * Map errors cl_cons_state errors to EPROTONOSUPPORT to indicate
+ * other versions of NFS can be tried.
+ */
+static int nfs41_check_session_ready(struct nfs_client *clp)
+{
+	int ret;
+	
+	ret = nfs4_client_recover_expired_lease(clp);
+	if (ret)
+		return ret;
+	if (clp->cl_cons_state < NFS_CS_READY)
+		return -EPROTONOSUPPORT;
+	return 0;
+}
+
 int nfs4_init_session(struct nfs_server *server)
 {
 	struct nfs_client *clp = server->nfs_client;
 	struct nfs4_session *session;
 	unsigned int rsize, wsize;
-	int ret;
 
 	if (!nfs4_has_session(clp))
 		return 0;
 
 	session = clp->cl_session;
-	if (!test_and_clear_bit(NFS4_SESSION_INITING, &session->session_state))
-		return 0;
+	spin_lock(&clp->cl_lock);
+	if (test_and_clear_bit(NFS4_SESSION_INITING, &session->session_state)) {
 
-	rsize = server->rsize;
-	if (rsize == 0)
-		rsize = NFS_MAX_FILE_IO_SIZE;
-	wsize = server->wsize;
-	if (wsize == 0)
-		wsize = NFS_MAX_FILE_IO_SIZE;
+		rsize = server->rsize;
+		if (rsize == 0)
+			rsize = NFS_MAX_FILE_IO_SIZE;
+		wsize = server->wsize;
+		if (wsize == 0)
+			wsize = NFS_MAX_FILE_IO_SIZE;
 
-	session->fc_attrs.max_rqst_sz = wsize + nfs41_maxwrite_overhead;
-	session->fc_attrs.max_resp_sz = rsize + nfs41_maxread_overhead;
+		session->fc_attrs.max_rqst_sz = wsize + nfs41_maxwrite_overhead;
+		session->fc_attrs.max_resp_sz = rsize + nfs41_maxread_overhead;
+	}
+	spin_unlock(&clp->cl_lock);
 
-	ret = nfs4_recover_expired_lease(server);
-	if (!ret)
-		ret = nfs4_check_client_ready(clp);
-	return ret;
+	return nfs41_check_session_ready(clp);
 }
 
-int nfs4_init_ds_session(struct nfs_client *clp)
+int nfs4_init_ds_session(struct nfs_client *clp, unsigned long lease_time)
 {
 	struct nfs4_session *session = clp->cl_session;
 	int ret;
 
-	if (!test_and_clear_bit(NFS4_SESSION_INITING, &session->session_state))
-		return 0;
-
-	ret = nfs4_client_recover_expired_lease(clp);
-	if (!ret)
-		/* Test for the DS role */
-		if (!is_ds_client(clp))
-			ret = -ENODEV;
-	if (!ret)
-		ret = nfs4_check_client_ready(clp);
-	return ret;
+	spin_lock(&clp->cl_lock);
+	if (test_and_clear_bit(NFS4_SESSION_INITING, &session->session_state)) {
+		/*
+		 * Do not set NFS_CS_CHECK_LEASE_TIME instead set the
+		 * DS lease to be equal to the MDS lease.
+		 */
+		clp->cl_lease_time = lease_time;
+		clp->cl_last_renewal = jiffies;
+	}
+	spin_unlock(&clp->cl_lock);
 
+	ret = nfs41_check_session_ready(clp);
+	if (ret)
+		return ret;
+	/* Test for the DS role */
+	if (!is_ds_client(clp))
+		return -ENODEV;
+	return 0;
 }
 EXPORT_SYMBOL_GPL(nfs4_init_ds_session);
 
-- 
1.7.7.6

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

[Trond Myklebust]

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,
-- 
1.7.7.6

[PATCH 3/3] NFS: Add memory barriers to the nfs_client->cl_cons_state initialisation

[Trond Myklebust]

Ensure that a process that uses the nfs_client->cl_cons_state test
for whether the initialisation process is finished does not read
stale data.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
---
 fs/nfs/client.c |    5 +++++
 fs/nfs/idmap.c  |    1 +
 2 files changed, 6 insertions(+), 0 deletions(-)

diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index e6070ea..4be85f9 100644
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -456,6 +456,8 @@ static bool nfs4_cb_match_client(const struct sockaddr *addr,
 	    clp->cl_cons_state == NFS_CS_SESSION_INITING))
 		return false;
 
+	smp_rmb();
+
 	/* Match the version and minorversion */
 	if (clp->rpc_ops->version != 4 ||
 	    clp->cl_minorversion != minorversion)
@@ -587,6 +589,8 @@ found_client:
 		return ERR_PTR(error);
 	}
 
+	smp_rmb();
+
 	BUG_ON(clp->cl_cons_state != NFS_CS_READY);
 
 	dprintk("--> nfs_get_client() = %p [share]\n", clp);
@@ -598,6 +602,7 @@ found_client:
  */
 void nfs_mark_client_ready(struct nfs_client *clp, int state)
 {
+	smp_wmb();
 	clp->cl_cons_state = state;
 	wake_up_all(&nfs_client_active_wq);
 }
diff --git a/fs/nfs/idmap.c b/fs/nfs/idmap.c
index 6ca949b..7d4e8dd 100644
--- a/fs/nfs/idmap.c
+++ b/fs/nfs/idmap.c
@@ -548,6 +548,7 @@ restart:
 		/* Skip nfs_clients that failed to initialise */
 		if (clp->cl_cons_state < 0)
 			continue;
+		smp_rmb();
 		if (clp->rpc_ops != &nfs_v4_clientops)
 			continue;
 		cl_dentry = clp->cl_idmap->idmap_pipe->dentry;
-- 
1.7.7.6

Re: [PATCH 1/3] NFSv4.1: Fix session initialisation races

[Adamson, Andy]

On May 23, 2012, at 1:32 PM, Trond Myklebust wrote:

> Session initialisation is not complete until the lease manager
> has run. We need to ensure that both nfs4_init_session and
> nfs4_init_ds_session do so, and that they check for any resulting
> errors in clp->cl_cons_state.
> 
> Only after this is done, can nfs4_ds_connect check the contents
> of clp->cl_exchange_flags.
> 
> Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
> Cc: Andy Adamson <andros@netapp.com>
> ---
> fs/nfs/client.c            |   16 ---------
> fs/nfs/internal.h          |    3 +-
> fs/nfs/nfs4filelayoutdev.c |   23 +------------
> fs/nfs/nfs4proc.c          |   77 ++++++++++++++++++++++++++++---------------
> 4 files changed, 52 insertions(+), 67 deletions(-)
> 
> diff --git a/fs/nfs/client.c b/fs/nfs/client.c
> index 60f7e4e..78970a1 100644
> --- a/fs/nfs/client.c
> +++ b/fs/nfs/client.c
> @@ -593,22 +593,6 @@ void nfs_mark_client_ready(struct nfs_client *clp, int state)
> }
> 
> /*
> - * With sessions, the client is not marked ready until after a
> - * successful EXCHANGE_ID and CREATE_SESSION.
> - *
> - * Map errors cl_cons_state errors to EPROTONOSUPPORT to indicate
> - * other versions of NFS can be tried.
> - */
> -int nfs4_check_client_ready(struct nfs_client *clp)
> -{
> -	if (!nfs4_has_session(clp))
> -		return 0;
> -	if (clp->cl_cons_state < NFS_CS_READY)
> -		return -EPROTONOSUPPORT;
> -	return 0;
> -}
> -
> -/*
>  * Initialise the timeout values for a connection
>  */
> static void nfs_init_timeout_values(struct rpc_timeout *to, int proto,
> diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
> index b777bda..00b66de 100644
> --- a/fs/nfs/internal.h
> +++ b/fs/nfs/internal.h
> @@ -168,7 +168,6 @@ extern struct nfs_server *nfs_clone_server(struct nfs_server *,
> 					   struct nfs_fattr *,
> 					   rpc_authflavor_t);
> extern void nfs_mark_client_ready(struct nfs_client *clp, int state);
> -extern int nfs4_check_client_ready(struct nfs_client *clp);
> extern struct nfs_client *nfs4_set_ds_client(struct nfs_client* mds_clp,
> 					     const struct sockaddr *ds_addr,
> 					     int ds_addrlen, int ds_proto);
> @@ -237,7 +236,7 @@ extern const u32 nfs41_maxwrite_overhead;
> extern struct rpc_procinfo nfs4_procedures[];
> #endif
> 
> -extern int nfs4_init_ds_session(struct nfs_client *clp);
> +extern int nfs4_init_ds_session(struct nfs_client *, unsigned long);
> 
> /* proc.c */
> void nfs_close_context(struct nfs_open_context *ctx, int is_sync);
> diff --git a/fs/nfs/nfs4filelayoutdev.c b/fs/nfs/nfs4filelayoutdev.c
> index c9cff9a..0764c98 100644
> --- a/fs/nfs/nfs4filelayoutdev.c
> +++ b/fs/nfs/nfs4filelayoutdev.c
> @@ -176,28 +176,7 @@ nfs4_ds_connect(struct nfs_server *mds_srv, struct nfs4_pnfs_ds *ds)
> 		goto out;
> 	}
> 
> -	if ((clp->cl_exchange_flags & EXCHGID4_FLAG_MASK_PNFS) != 0) {
> -		if (!is_ds_client(clp)) {
> -			status = -ENODEV;
> -			goto out_put;
> -		}
> -		ds->ds_clp = clp;
> -		dprintk("%s [existing] server=%s\n", __func__,
> -			ds->ds_remotestr);
> -		goto out;
> -	}
> -
> -	/*
> -	 * Do not set NFS_CS_CHECK_LEASE_TIME instead set the DS lease to
> -	 * be equal to the MDS lease. Renewal is scheduled in create_session.
> -	 */
> -	spin_lock(&mds_srv->nfs_client->cl_lock);
> -	clp->cl_lease_time = mds_srv->nfs_client->cl_lease_time;
> -	spin_unlock(&mds_srv->nfs_client->cl_lock);
> -	clp->cl_last_renewal = jiffies;
> -
> -	/* New nfs_client */
> -	status = nfs4_init_ds_session(clp);
> +	status = nfs4_init_ds_session(clp, mds_srv->nfs_client->cl_lease_time);
> 	if (status)
> 		goto out_put;
> 
> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
> index 99650aa..272c4ad 100644
> --- a/fs/nfs/nfs4proc.c
> +++ b/fs/nfs/nfs4proc.c
> @@ -5605,53 +5605,76 @@ int nfs4_proc_destroy_session(struct nfs4_session *session)
> 	return status;
> }
> 
> +/*
> + * With sessions, the client is not marked ready until after a
> + * successful EXCHANGE_ID and CREATE_SESSION.
> + *
> + * Map errors cl_cons_state errors to EPROTONOSUPPORT to indicate
> + * other versions of NFS can be tried.
> + */
> +static int nfs41_check_session_ready(struct nfs_client *clp)
> +{
> +	int ret;
> +	
> +	ret = nfs4_client_recover_expired_lease(clp);
> +	if (ret)
> +		return ret;
> +	if (clp->cl_cons_state < NFS_CS_READY)
> +		return -EPROTONOSUPPORT;
> +	return 0;
> +}
> +
> int nfs4_init_session(struct nfs_server *server)
> {
> 	struct nfs_client *clp = server->nfs_client;
> 	struct nfs4_session *session;
> 	unsigned int rsize, wsize;
> -	int ret;
> 
> 	if (!nfs4_has_session(clp))
> 		return 0;
> 
> 	session = clp->cl_session;
> -	if (!test_and_clear_bit(NFS4_SESSION_INITING, &session->session_state))
> -		return 0;
> +	spin_lock(&clp->cl_lock);
> +	if (test_and_clear_bit(NFS4_SESSION_INITING, &session->session_state)) {
> 
> -	rsize = server->rsize;
> -	if (rsize == 0)
> -		rsize = NFS_MAX_FILE_IO_SIZE;
> -	wsize = server->wsize;
> -	if (wsize == 0)
> -		wsize = NFS_MAX_FILE_IO_SIZE;
> +		rsize = server->rsize;
> +		if (rsize == 0)
> +			rsize = NFS_MAX_FILE_IO_SIZE;
> +		wsize = server->wsize;
> +		if (wsize == 0)
> +			wsize = NFS_MAX_FILE_IO_SIZE;
> 
> -	session->fc_attrs.max_rqst_sz = wsize + nfs41_maxwrite_overhead;
> -	session->fc_attrs.max_resp_sz = rsize + nfs41_maxread_overhead;
> +		session->fc_attrs.max_rqst_sz = wsize + nfs41_maxwrite_overhead;
> +		session->fc_attrs.max_resp_sz = rsize + nfs41_maxread_overhead;
> +	}
> +	spin_unlock(&clp->cl_lock);
> 
> -	ret = nfs4_recover_expired_lease(server);
> -	if (!ret)
> -		ret = nfs4_check_client_ready(clp);
> -	return ret;
> +	return nfs41_check_session_ready(clp);
> }
> 
> -int nfs4_init_ds_session(struct nfs_client *clp)
> +int nfs4_init_ds_session(struct nfs_client *clp, unsigned long lease_time)
> {
> 	struct nfs4_session *session = clp->cl_session;
> 	int ret;
> 
> -	if (!test_and_clear_bit(NFS4_SESSION_INITING, &session->session_state))
> -		return 0;
> -
> -	ret = nfs4_client_recover_expired_lease(clp);
> -	if (!ret)
> -		/* Test for the DS role */
> -		if (!is_ds_client(clp))
> -			ret = -ENODEV;
> -	if (!ret)
> -		ret = nfs4_check_client_ready(clp);
> -	return ret;
> +	spin_lock(&clp->cl_lock);
> +	if (test_and_clear_bit(NFS4_SESSION_INITING, &session->session_state)) {
> +		/*
> +		 * Do not set NFS_CS_CHECK_LEASE_TIME instead set the
> +		 * DS lease to be equal to the MDS lease.
> +		 */
> +		clp->cl_lease_time = lease_time;
> +		clp->cl_last_renewal = jiffies;
> +	}
> +	spin_unlock(&clp->cl_lock);
> 
> +	ret = nfs41_check_session_ready(clp);

If I read the code correctly, on an existing client,  this call needlessly waits for the state manager to finish whatever it is doing. As the state manager could be operating on a different file system than the DS belongs to,  and recovering a bunch of state,  it might be worth while to avoid.  That was the intention of checking the cl_exchange_flags in nfs4_ds_connect.
In fact, on an existing client, nfs4_init_ds_session does not need to be called.

-->Andy

> +	if (ret)
> +		return ret;
> +	/* Test for the DS role */
> +	if (!is_ds_client(clp))
> +		return -ENODEV;
> +	return 0;
> }
> EXPORT_SYMBOL_GPL(nfs4_init_ds_session);
> 
> -- 
> 1.7.7.6
> 

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

[Stanislav Kinsbursky]

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,

Re: [PATCH 1/3] NFSv4.1: Fix session initialisation races

[Myklebust, Trond]

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b20NCnd3dy5uZXRhcHAuY29tDQoNCg==

Re: [PATCH 1/3] NFSv4.1: Fix session initialisation races

[Myklebust, Trond]

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Re: [PATCH 1/3] NFSv4.1: Fix session initialisation races

[Adamson, Andy]

On May 23, 2012, at 3:20 PM, Myklebust, Trond wrote:

> On Wed, 2012-05-23 at 19:14 +0000, Myklebust, Trond wrote:
>> On Wed, 2012-05-23 at 18:37 +0000, Adamson, Andy wrote:
>>> 
>>> On May 23, 2012, at 1:32 PM, Trond Myklebust wrote:
>>> 
>>>> Session initialisation is not complete until the lease manager
>>>> has run. We need to ensure that both nfs4_init_session and
>>>> nfs4_init_ds_session do so, and that they check for any resulting
>>>> errors in clp->cl_cons_state.
>>>> 
>>>> Only after this is done, can nfs4_ds_connect check the contents
>>>> of clp->cl_exchange_flags.
>>>> 
>>>> Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
>>>> Cc: Andy Adamson <andros@netapp.com>
>>>> ---
>>>> fs/nfs/client.c            |   16 ---------
>>>> fs/nfs/internal.h          |    3 +-
>>>> fs/nfs/nfs4filelayoutdev.c |   23 +------------
>>>> fs/nfs/nfs4proc.c          |   77 ++++++++++++++++++++++++++++---------------
>>>> 4 files changed, 52 insertions(+), 67 deletions(-)
>>>> 
>>>> diff --git a/fs/nfs/client.c b/fs/nfs/client.c
>>>> index 60f7e4e..78970a1 100644
>>>> --- a/fs/nfs/client.c
>>>> +++ b/fs/nfs/client.c
>>>> @@ -593,22 +593,6 @@ void nfs_mark_client_ready(struct nfs_client *clp, int state)
>>>> }
>>>> 
>>>> /*
>>>> - * With sessions, the client is not marked ready until after a
>>>> - * successful EXCHANGE_ID and CREATE_SESSION.
>>>> - *
>>>> - * Map errors cl_cons_state errors to EPROTONOSUPPORT to indicate
>>>> - * other versions of NFS can be tried.
>>>> - */
>>>> -int nfs4_check_client_ready(struct nfs_client *clp)
>>>> -{
>>>> -	if (!nfs4_has_session(clp))
>>>> -		return 0;
>>>> -	if (clp->cl_cons_state < NFS_CS_READY)
>>>> -		return -EPROTONOSUPPORT;
>>>> -	return 0;
>>>> -}
>>>> -
>>>> -/*
>>>> * Initialise the timeout values for a connection
>>>> */
>>>> static void nfs_init_timeout_values(struct rpc_timeout *to, int proto,
>>>> diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
>>>> index b777bda..00b66de 100644
>>>> --- a/fs/nfs/internal.h
>>>> +++ b/fs/nfs/internal.h
>>>> @@ -168,7 +168,6 @@ extern struct nfs_server *nfs_clone_server(struct nfs_server *,
>>>> 					   struct nfs_fattr *,
>>>> 					   rpc_authflavor_t);
>>>> extern void nfs_mark_client_ready(struct nfs_client *clp, int state);
>>>> -extern int nfs4_check_client_ready(struct nfs_client *clp);
>>>> extern struct nfs_client *nfs4_set_ds_client(struct nfs_client* mds_clp,
>>>> 					     const struct sockaddr *ds_addr,
>>>> 					     int ds_addrlen, int ds_proto);
>>>> @@ -237,7 +236,7 @@ extern const u32 nfs41_maxwrite_overhead;
>>>> extern struct rpc_procinfo nfs4_procedures[];
>>>> #endif
>>>> 
>>>> -extern int nfs4_init_ds_session(struct nfs_client *clp);
>>>> +extern int nfs4_init_ds_session(struct nfs_client *, unsigned long);
>>>> 
>>>> /* proc.c */
>>>> void nfs_close_context(struct nfs_open_context *ctx, int is_sync);
>>>> diff --git a/fs/nfs/nfs4filelayoutdev.c b/fs/nfs/nfs4filelayoutdev.c
>>>> index c9cff9a..0764c98 100644
>>>> --- a/fs/nfs/nfs4filelayoutdev.c
>>>> +++ b/fs/nfs/nfs4filelayoutdev.c
>>>> @@ -176,28 +176,7 @@ nfs4_ds_connect(struct nfs_server *mds_srv, struct nfs4_pnfs_ds *ds)
>>>> 		goto out;
>>>> 	}
>>>> 
>>>> -	if ((clp->cl_exchange_flags & EXCHGID4_FLAG_MASK_PNFS) != 0) {
>>>> -		if (!is_ds_client(clp)) {
>>>> -			status = -ENODEV;
>>>> -			goto out_put;
>>>> -		}
>>>> -		ds->ds_clp = clp;
>>>> -		dprintk("%s [existing] server=%s\n", __func__,
>>>> -			ds->ds_remotestr);
>>>> -		goto out;
>>>> -	}
>>>> -
>>>> -	/*
>>>> -	 * Do not set NFS_CS_CHECK_LEASE_TIME instead set the DS lease to
>>>> -	 * be equal to the MDS lease. Renewal is scheduled in create_session.
>>>> -	 */
>>>> -	spin_lock(&mds_srv->nfs_client->cl_lock);
>>>> -	clp->cl_lease_time = mds_srv->nfs_client->cl_lease_time;
>>>> -	spin_unlock(&mds_srv->nfs_client->cl_lock);
>>>> -	clp->cl_last_renewal = jiffies;
>>>> -
>>>> -	/* New nfs_client */
>>>> -	status = nfs4_init_ds_session(clp);
>>>> +	status = nfs4_init_ds_session(clp, mds_srv->nfs_client->cl_lease_time);
>>>> 	if (status)
>>>> 		goto out_put;
>>>> 
>>>> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
>>>> index 99650aa..272c4ad 100644
>>>> --- a/fs/nfs/nfs4proc.c
>>>> +++ b/fs/nfs/nfs4proc.c
>>>> @@ -5605,53 +5605,76 @@ int nfs4_proc_destroy_session(struct nfs4_session *session)
>>>> 	return status;
>>>> }
>>>> 
>>>> +/*
>>>> + * With sessions, the client is not marked ready until after a
>>>> + * successful EXCHANGE_ID and CREATE_SESSION.
>>>> + *
>>>> + * Map errors cl_cons_state errors to EPROTONOSUPPORT to indicate
>>>> + * other versions of NFS can be tried.
>>>> + */
>>>> +static int nfs41_check_session_ready(struct nfs_client *clp)
>>>> +{
>>>> +	int ret;
>>>> +	
>>>> +	ret = nfs4_client_recover_expired_lease(clp);
>>>> +	if (ret)
>>>> +		return ret;
>>>> +	if (clp->cl_cons_state < NFS_CS_READY)
>>>> +		return -EPROTONOSUPPORT;
>>>> +	return 0;
>>>> +}
>>>> +
>>>> int nfs4_init_session(struct nfs_server *server)
>>>> {
>>>> 	struct nfs_client *clp = server->nfs_client;
>>>> 	struct nfs4_session *session;
>>>> 	unsigned int rsize, wsize;
>>>> -	int ret;
>>>> 
>>>> 	if (!nfs4_has_session(clp))
>>>> 		return 0;
>>>> 
>>>> 	session = clp->cl_session;
>>>> -	if (!test_and_clear_bit(NFS4_SESSION_INITING, &session->session_state))
>>>> -		return 0;
>>>> +	spin_lock(&clp->cl_lock);
>>>> +	if (test_and_clear_bit(NFS4_SESSION_INITING, &session->session_state)) {
>>>> 
>>>> -	rsize = server->rsize;
>>>> -	if (rsize == 0)
>>>> -		rsize = NFS_MAX_FILE_IO_SIZE;
>>>> -	wsize = server->wsize;
>>>> -	if (wsize == 0)
>>>> -		wsize = NFS_MAX_FILE_IO_SIZE;
>>>> +		rsize = server->rsize;
>>>> +		if (rsize == 0)
>>>> +			rsize = NFS_MAX_FILE_IO_SIZE;
>>>> +		wsize = server->wsize;
>>>> +		if (wsize == 0)
>>>> +			wsize = NFS_MAX_FILE_IO_SIZE;
>>>> 
>>>> -	session->fc_attrs.max_rqst_sz = wsize + nfs41_maxwrite_overhead;
>>>> -	session->fc_attrs.max_resp_sz = rsize + nfs41_maxread_overhead;
>>>> +		session->fc_attrs.max_rqst_sz = wsize + nfs41_maxwrite_overhead;
>>>> +		session->fc_attrs.max_resp_sz = rsize + nfs41_maxread_overhead;
>>>> +	}
>>>> +	spin_unlock(&clp->cl_lock);
>>>> 
>>>> -	ret = nfs4_recover_expired_lease(server);
>>>> -	if (!ret)
>>>> -		ret = nfs4_check_client_ready(clp);
>>>> -	return ret;
>>>> +	return nfs41_check_session_ready(clp);
>>>> }
>>>> 
>>>> -int nfs4_init_ds_session(struct nfs_client *clp)
>>>> +int nfs4_init_ds_session(struct nfs_client *clp, unsigned long lease_time)
>>>> {
>>>> 	struct nfs4_session *session = clp->cl_session;
>>>> 	int ret;
>>>> 
>>>> -	if (!test_and_clear_bit(NFS4_SESSION_INITING, &session->session_state))
>>>> -		return 0;
>>>> -
>>>> -	ret = nfs4_client_recover_expired_lease(clp);
>>>> -	if (!ret)
>>>> -		/* Test for the DS role */
>>>> -		if (!is_ds_client(clp))
>>>> -			ret = -ENODEV;
>>>> -	if (!ret)
>>>> -		ret = nfs4_check_client_ready(clp);
>>>> -	return ret;
>>>> +	spin_lock(&clp->cl_lock);
>>>> +	if (test_and_clear_bit(NFS4_SESSION_INITING, &session->session_state)) {
>>>> +		/*
>>>> +		 * Do not set NFS_CS_CHECK_LEASE_TIME instead set the
>>>> +		 * DS lease to be equal to the MDS lease.
>>>> +		 */
>>>> +		clp->cl_lease_time = lease_time;
>>>> +		clp->cl_last_renewal = jiffies;
>>>> +	}
>>>> +	spin_unlock(&clp->cl_lock);
>>>> 
>>>> +	ret = nfs41_check_session_ready(clp);
>>> 
>>> If I read the code correctly, on an existing client,  this call needlessly waits for the state manager to finish whatever it is doing. As the state manager could be operating on a different file system than the DS belongs to,  and recovering a bunch of state,  it might be worth while to avoid.  That was the intention of checking the cl_exchange_flags in nfs4_ds_connect.
>>> In fact, on an existing client, nfs4_init_ds_session does not need to be called.
>> 
>> Yes it does. Right now you have no guarantee that the state manager is
>> finished setting up the session, and so no guarantee that it will
>> succeed.
>> 
>> We can perhaps skip the call to nfs4_recover_expired_lease() if (and
>> only if) clp->cl_cons_state <= NFS_CS_READY, but otherwise it does need
>> to complete.
> 
> IOW: Something like the following change to nfs41_check_session_ready():
> 
> diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
> index 565105b..c856298 100644
> --- a/fs/nfs/nfs4proc.c
> +++ b/fs/nfs/nfs4proc.c
> @@ -5614,9 +5614,11 @@ static int nfs41_check_session_ready(struct nfs_client *clp)
> {
> 	int ret;
> 	
> -	ret = nfs4_client_recover_expired_lease(clp);
> -	if (ret)
> -		return ret;
> +	if (clp->cl_cons_state == NFS_CS_SESSION_INITING) {
> +		ret = nfs4_client_recover_expired_lease(clp);
> +		if (ret)
> +			return ret;
> +	}
> 	if (clp->cl_cons_state < NFS_CS_READY)
> 		return -EPROTONOSUPPORT;
> 	return 0;
> 

Yes - that addresses my concern. Nice cleanup of the ds connection code.

-->Andy

> 
> -- 
> Trond Myklebust
> Linux NFS client maintainer
> 
> NetApp
> Trond.Myklebust@netapp.com
> www.netapp.com
> 

Re: [PATCH 3/3] NFS: Add memory barriers to the nfs_client->cl_cons_state initialisation

[Stanislav Kinsbursky]

23.05.2012 21:32, Trond Myklebust написал:
> Ensure that a process that uses the nfs_client->cl_cons_state test
> for whether the initialisation process is finished does not read
> stale data.
>
> Signed-off-by: Trond Myklebust<Trond.Myklebust@netapp.com>
> ---
>   fs/nfs/client.c |    5 +++++
>   fs/nfs/idmap.c  |    1 +
>   2 files changed, 6 insertions(+), 0 deletions(-)
>
> diff --git a/fs/nfs/client.c b/fs/nfs/client.c
> index e6070ea..4be85f9 100644
> --- a/fs/nfs/client.c
> +++ b/fs/nfs/client.c
> @@ -456,6 +456,8 @@ static bool nfs4_cb_match_client(const struct sockaddr *addr,
>   	    clp->cl_cons_state == NFS_CS_SESSION_INITING))
>   		return false;
>
> +	smp_rmb();
> +
>   	/* Match the version and minorversion */
>   	if (clp->rpc_ops->version != 4 ||
>   	    clp->cl_minorversion != minorversion)
> @@ -587,6 +589,8 @@ found_client:
>   		return ERR_PTR(error);
>   	}
>
> +	smp_rmb();
> +
>   	BUG_ON(clp->cl_cons_state != NFS_CS_READY);
>
>   	dprintk("-->  nfs_get_client() = %p [share]\n", clp);
> @@ -598,6 +602,7 @@ found_client:
>    */
>   void nfs_mark_client_ready(struct nfs_client *clp, int state)
>   {
> +	smp_wmb();

BTW, why barrier is before assignment?

>   	clp->cl_cons_state = state;
>   	wake_up_all(&nfs_client_active_wq);
>   }
> diff --git a/fs/nfs/idmap.c b/fs/nfs/idmap.c
> index 6ca949b..7d4e8dd 100644
> --- a/fs/nfs/idmap.c
> +++ b/fs/nfs/idmap.c
> @@ -548,6 +548,7 @@ restart:
>   		/* Skip nfs_clients that failed to initialise */
>   		if (clp->cl_cons_state<  0)
>   			continue;
> +		smp_rmb();
>   		if (clp->rpc_ops !=&nfs_v4_clientops)
>   			continue;
>   		cl_dentry = clp->cl_idmap->idmap_pipe->dentry;

Re: [PATCH 3/3] NFS: Add memory barriers to the nfs_client->cl_cons_state initialisation

[Myklebust, Trond]

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