[PATCH 0/4] SUNRPC: several fixes around PipeFS objects

[PATCH 0/4] SUNRPC: several fixes around PipeFS objects

[Stanislav Kinsbursky]

First two pathes fixes lockdep warnings and next two - dereferencing of
released pipe data on eventfd close.

The following series consists of:

---

Stanislav Kinsbursky (4):
      SUNRPC: replace per-net client lock by rw mutex
      NFS: replace per-net client lock by mutex
      SUNRPC: check RPC inode's pipe reference before dereferencing
      SUNRPC: move waitq from RPC pipe to RPC inode


 fs/nfs/client.c                    |   36 +++++++++---------
 fs/nfs/idmap.c                     |    4 +-
 fs/nfs/netns.h                     |    2 +
 include/linux/sunrpc/rpc_pipe_fs.h |    2 +
 net/sunrpc/clnt.c                  |   16 ++++----
 net/sunrpc/netns.h                 |    2 +
 net/sunrpc/rpc_pipe.c              |   71 +++++++++++++++++++++++-------------
 net/sunrpc/sunrpc_syms.c           |    2 +
 8 files changed, 77 insertions(+), 58 deletions(-)

[PATCH 1/4] SUNRPC: replace per-net client lock by rw mutex

[Stanislav Kinsbursky]

Lockdep is sad otherwise, because inode mutex is taken on PipeFS dentry
creation, which can be called on mount notification, where this per-net client
lock is taken on clients list walk.

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

---
 net/sunrpc/clnt.c        |   16 ++++++++--------
 net/sunrpc/netns.h       |    2 +-
 net/sunrpc/sunrpc_syms.c |    2 +-
 3 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/net/sunrpc/clnt.c b/net/sunrpc/clnt.c
index bb7ed2f3..2d3a547 100644
--- a/net/sunrpc/clnt.c
+++ b/net/sunrpc/clnt.c
@@ -83,18 +83,18 @@ static void rpc_register_client(struct rpc_clnt *clnt)
 {
 	struct sunrpc_net *sn = net_generic(clnt->cl_xprt->xprt_net, sunrpc_net_id);
 
-	spin_lock(&sn->rpc_client_lock);
+	down_write(&sn->rpc_client_lock);
 	list_add(&clnt->cl_clients, &sn->all_clients);
-	spin_unlock(&sn->rpc_client_lock);
+	up_write(&sn->rpc_client_lock);
 }
 
 static void rpc_unregister_client(struct rpc_clnt *clnt)
 {
 	struct sunrpc_net *sn = net_generic(clnt->cl_xprt->xprt_net, sunrpc_net_id);
 
-	spin_lock(&sn->rpc_client_lock);
+	down_write(&sn->rpc_client_lock);
 	list_del(&clnt->cl_clients);
-	spin_unlock(&sn->rpc_client_lock);
+	up_write(&sn->rpc_client_lock);
 }
 
 static void __rpc_clnt_remove_pipedir(struct rpc_clnt *clnt)
@@ -212,13 +212,13 @@ static int rpc_pipefs_event(struct notifier_block *nb, unsigned long event,
 	int error = 0;
 	struct sunrpc_net *sn = net_generic(sb->s_fs_info, sunrpc_net_id);
 
-	spin_lock(&sn->rpc_client_lock);
+	down_read(&sn->rpc_client_lock);
 	list_for_each_entry(clnt, &sn->all_clients, cl_clients) {
 		error = __rpc_pipefs_event(clnt, event, sb);
 		if (error)
 			break;
 	}
-	spin_unlock(&sn->rpc_client_lock);
+	up_read(&sn->rpc_client_lock);
 	return error;
 }
 
@@ -1947,7 +1947,7 @@ void rpc_show_tasks(struct net *net)
 	int header = 0;
 	struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
 
-	spin_lock(&sn->rpc_client_lock);
+	down_read(&sn->rpc_client_lock);
 	list_for_each_entry(clnt, &sn->all_clients, cl_clients) {
 		spin_lock(&clnt->cl_lock);
 		list_for_each_entry(task, &clnt->cl_tasks, tk_task) {
@@ -1959,6 +1959,6 @@ void rpc_show_tasks(struct net *net)
 		}
 		spin_unlock(&clnt->cl_lock);
 	}
-	spin_unlock(&sn->rpc_client_lock);
+	up_read(&sn->rpc_client_lock);
 }
 #endif
diff --git a/net/sunrpc/netns.h b/net/sunrpc/netns.h
index ce7bd44..88f4b2e 100644
--- a/net/sunrpc/netns.h
+++ b/net/sunrpc/netns.h
@@ -17,7 +17,7 @@ struct sunrpc_net {
 	struct mutex pipefs_sb_lock;
 
 	struct list_head all_clients;
-	spinlock_t rpc_client_lock;
+	struct rw_semaphore rpc_client_lock;
 
 	struct rpc_clnt *rpcb_local_clnt;
 	struct rpc_clnt *rpcb_local_clnt4;
diff --git a/net/sunrpc/sunrpc_syms.c b/net/sunrpc/sunrpc_syms.c
index 21d106e..57fa75f 100644
--- a/net/sunrpc/sunrpc_syms.c
+++ b/net/sunrpc/sunrpc_syms.c
@@ -49,7 +49,7 @@ static __net_init int sunrpc_init_net(struct net *net)
 
 	rpc_pipefs_init_net(net);
 	INIT_LIST_HEAD(&sn->all_clients);
-	spin_lock_init(&sn->rpc_client_lock);
+	init_rwsem(&sn->rpc_client_lock);
 	spin_lock_init(&sn->rpcb_clnt_lock);
 	return 0;
 

[PATCH 2/4] NFS: replace per-net client lock by mutex

[Stanislav Kinsbursky]

Lockdep is sad otherwise, because inode mutex is taken on PipeFS dentry
creation, which can be called on mount notification, where this per-net client
lock is taken on clients list walk.

Note: I used simple mutex instead of rw semaphore because of
nfs_put_client->atomic_dec_and_mutex_lock() call. Probably, there is a better
solution here.

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

---
 fs/nfs/client.c |   36 ++++++++++++++++++------------------
 fs/nfs/idmap.c  |    4 ++--
 fs/nfs/netns.h  |    2 +-
 3 files changed, 21 insertions(+), 21 deletions(-)

diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index 8563585..d15269f 100644
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -72,9 +72,9 @@ static int nfs_get_cb_ident_idr(struct nfs_client *clp, int minorversion)
 retry:
 	if (!idr_pre_get(&nn->cb_ident_idr, GFP_KERNEL))
 		return -ENOMEM;
-	spin_lock(&nn->nfs_client_lock);
+	mutex_lock(&nn->nfs_client_lock);
 	ret = idr_get_new(&nn->cb_ident_idr, clp, &clp->cl_cb_ident);
-	spin_unlock(&nn->nfs_client_lock);
+	mutex_unlock(&nn->nfs_client_lock);
 	if (ret == -EAGAIN)
 		goto retry;
 	return ret;
@@ -321,10 +321,10 @@ void nfs_put_client(struct nfs_client *clp)
 	dprintk("--> nfs_put_client({%d})\n", atomic_read(&clp->cl_count));
 	nn = net_generic(clp->net, nfs_net_id);
 
-	if (atomic_dec_and_lock(&clp->cl_count, &nn->nfs_client_lock)) {
+	if (atomic_dec_and_mutex_lock(&clp->cl_count, &nn->nfs_client_lock)) {
 		list_del(&clp->cl_share_link);
 		nfs_cb_idr_remove_locked(clp);
-		spin_unlock(&nn->nfs_client_lock);
+		mutex_unlock(&nn->nfs_client_lock);
 
 		BUG_ON(!list_empty(&clp->cl_superblocks));
 
@@ -519,7 +519,7 @@ nfs_get_client(const struct nfs_client_initdata *cl_init,
 
 	/* see if the client already exists */
 	do {
-		spin_lock(&nn->nfs_client_lock);
+		mutex_lock(&nn->nfs_client_lock);
 
 		clp = nfs_match_client(cl_init);
 		if (clp)
@@ -527,7 +527,7 @@ nfs_get_client(const struct nfs_client_initdata *cl_init,
 		if (new)
 			goto install_client;
 
-		spin_unlock(&nn->nfs_client_lock);
+		mutex_unlock(&nn->nfs_client_lock);
 
 		new = nfs_alloc_client(cl_init);
 	} while (!IS_ERR(new));
@@ -539,7 +539,7 @@ nfs_get_client(const struct nfs_client_initdata *cl_init,
 install_client:
 	clp = new;
 	list_add(&clp->cl_share_link, &nn->nfs_client_list);
-	spin_unlock(&nn->nfs_client_lock);
+	mutex_unlock(&nn->nfs_client_lock);
 
 	error = cl_init->rpc_ops->init_client(clp, timeparms, ip_addr,
 					      authflavour, noresvport);
@@ -554,7 +554,7 @@ install_client:
 	 * - make sure it's ready before returning
 	 */
 found_client:
-	spin_unlock(&nn->nfs_client_lock);
+	mutex_unlock(&nn->nfs_client_lock);
 
 	if (new)
 		nfs_free_client(new);
@@ -1045,11 +1045,11 @@ static void nfs_server_insert_lists(struct nfs_server *server)
 	struct nfs_client *clp = server->nfs_client;
 	struct nfs_net *nn = net_generic(clp->net, nfs_net_id);
 
-	spin_lock(&nn->nfs_client_lock);
+	mutex_lock(&nn->nfs_client_lock);
 	list_add_tail_rcu(&server->client_link, &clp->cl_superblocks);
 	list_add_tail(&server->master_link, &nn->nfs_volume_list);
 	clear_bit(NFS_CS_STOP_RENEW, &clp->cl_res_state);
-	spin_unlock(&nn->nfs_client_lock);
+	mutex_unlock(&nn->nfs_client_lock);
 
 }
 
@@ -1061,12 +1061,12 @@ static void nfs_server_remove_lists(struct nfs_server *server)
 	if (clp == NULL)
 		return;
 	nn = net_generic(clp->net, nfs_net_id);
-	spin_lock(&nn->nfs_client_lock);
+	mutex_lock(&nn->nfs_client_lock);
 	list_del_rcu(&server->client_link);
 	if (list_empty(&clp->cl_superblocks))
 		set_bit(NFS_CS_STOP_RENEW, &clp->cl_res_state);
 	list_del(&server->master_link);
-	spin_unlock(&nn->nfs_client_lock);
+	mutex_unlock(&nn->nfs_client_lock);
 
 	synchronize_rcu();
 }
@@ -1220,11 +1220,11 @@ nfs4_find_client_ident(struct net *net, int cb_ident)
 	struct nfs_client *clp;
 	struct nfs_net *nn = net_generic(net, nfs_net_id);
 
-	spin_lock(&nn->nfs_client_lock);
+	mutex_lock(&nn->nfs_client_lock);
 	clp = idr_find(&nn->cb_ident_idr, cb_ident);
 	if (clp)
 		atomic_inc(&clp->cl_count);
-	spin_unlock(&nn->nfs_client_lock);
+	mutex_unlock(&nn->nfs_client_lock);
 	return clp;
 }
 
@@ -1243,7 +1243,7 @@ nfs4_find_client_sessionid(struct net *net, const struct sockaddr *addr,
 	struct nfs_client *clp;
 	struct nfs_net *nn = net_generic(net, nfs_net_id);
 
-	spin_lock(&nn->nfs_client_lock);
+	mutex_lock(&nn->nfs_client_lock);
 	list_for_each_entry(clp, &nn->nfs_client_list, cl_share_link) {
 		if (nfs4_cb_match_client(addr, clp, 1) == false)
 			continue;
@@ -1257,10 +1257,10 @@ nfs4_find_client_sessionid(struct net *net, const struct sockaddr *addr,
 			continue;
 
 		atomic_inc(&clp->cl_count);
-		spin_unlock(&nn->nfs_client_lock);
+		mutex_unlock(&nn->nfs_client_lock);
 		return clp;
 	}
-	spin_unlock(&nn->nfs_client_lock);
+	mutex_unlock(&nn->nfs_client_lock);
 	return NULL;
 }
 
@@ -1781,7 +1781,7 @@ void nfs_clients_init(struct net *net)
 #ifdef CONFIG_NFS_V4
 	idr_init(&nn->cb_ident_idr);
 #endif
-	spin_lock_init(&nn->nfs_client_lock);
+	mutex_init(&nn->nfs_client_lock);
 }
 
 #ifdef CONFIG_PROC_FS
diff --git a/fs/nfs/idmap.c b/fs/nfs/idmap.c
index b5c6d8e..98b0b6b 100644
--- a/fs/nfs/idmap.c
+++ b/fs/nfs/idmap.c
@@ -561,7 +561,7 @@ static int rpc_pipefs_event(struct notifier_block *nb, unsigned long event,
 	struct nfs_client *clp;
 	int error = 0;
 
-	spin_lock(&nn->nfs_client_lock);
+	mutex_lock(&nn->nfs_client_lock);
 	list_for_each_entry(clp, &nn->nfs_client_list, cl_share_link) {
 		if (clp->rpc_ops != &nfs_v4_clientops)
 			continue;
@@ -569,7 +569,7 @@ static int rpc_pipefs_event(struct notifier_block *nb, unsigned long event,
 		if (error)
 			break;
 	}
-	spin_unlock(&nn->nfs_client_lock);
+	mutex_unlock(&nn->nfs_client_lock);
 	return error;
 }
 
diff --git a/fs/nfs/netns.h b/fs/nfs/netns.h
index 7baad89..24d0bc3 100644
--- a/fs/nfs/netns.h
+++ b/fs/nfs/netns.h
@@ -12,7 +12,7 @@ struct nfs_net {
 #ifdef CONFIG_NFS_V4
 	struct idr cb_ident_idr; /* Protected by nfs_client_lock */
 #endif
-	spinlock_t nfs_client_lock;
+	struct mutex nfs_client_lock;
 };
 
 extern int nfs_net_id;

Re: [PATCH 2/4] NFS: replace per-net client lock by mutex

[Myklebust, Trond]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset="utf-8", Size: 1062 bytes --]

On Mon, 2012-02-27 at 17:49 +0400, Stanislav Kinsbursky wrote:
> Lockdep is sad otherwise, because inode mutex is taken on PipeFS dentry
> creation, which can be called on mount notification, where this per-net client
> lock is taken on clients list walk.
> 
> Note: I used simple mutex instead of rw semaphore because of
> nfs_put_client->atomic_dec_and_mutex_lock() call. Probably, there is a better
> solution here.
> 
> Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
> 

This is overkill... We end up blocking NFSv4 callbacks while the
rpc_pipefs notifier runs through the nfs_clients creating or destroying
idmapper dentries.

Surely the rpc_pipefs_event() can take a reference to the nfs_client and
then drop the spin_lock if it sees that it needs to create or destroy a
dentry?

-- 
Trond Myklebust
Linux NFS client maintainer

NetApp
Trond.Myklebust@netapp.com
www.netapp.com

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Re: [PATCH 2/4] NFS: replace per-net client lock by mutex

[Stanislav Kinsbursky]

27.02.2012 19:00, Myklebust, Trond пишет:
> On Mon, 2012-02-27 at 17:49 +0400, Stanislav Kinsbursky wrote:
>> Lockdep is sad otherwise, because inode mutex is taken on PipeFS dentry
>> creation, which can be called on mount notification, where this per-net client
>> lock is taken on clients list walk.
>>
>> Note: I used simple mutex instead of rw semaphore because of
>> nfs_put_client->atomic_dec_and_mutex_lock() call. Probably, there is a better
>> solution here.
>>
>> Signed-off-by: Stanislav Kinsbursky<skinsbursky@parallels.com>
>>
>
> This is overkill... We end up blocking NFSv4 callbacks while the
> rpc_pipefs notifier runs through the nfs_clients creating or destroying
> idmapper dentries.
>
> Surely the rpc_pipefs_event() can take a reference to the nfs_client and
> then drop the spin_lock if it sees that it needs to create or destroy a
> dentry?
>

Sure, thanks for notice.
Looks like this logic also works to SUNRPC clients.
I'll send updated version soon.

-- 
Best regards,
Stanislav Kinsbursky

[PATCH 3/4] SUNRPC: check RPC inode's pipe reference before dereferencing

[Stanislav Kinsbursky]

There are 2 tightly bound objects: pipe data (created for kernel needs, has
reference to dentry, which depends on PipeFS mount/umount) and PipeFS
dentry/inode pair (created on mount for user-space needs). They both
independently may have or have not a valid reference to each other.
This means, that we have to make sure, that pipe->dentry reference is valid on
upcalls, and dentry->pipe reference is valid on downcalls. The latter check is
absent - my fault.
IOW, PipeFS dentry can be opened by some process (rpc.idmapd for example), but
it's pipe data can belong to NFS mount, which was unmounted already and thus
pipe data was destroyed.
To fix this, pipe reference have to be set to NULL on rpc_unlink() and checked
on PipeFS file operations instead of pipe->dentry check.

Note: PipeFS "poll" file operation will be updated in next patch, because it's
logic is more complicated.

Signed-off-by: Stanislav Kinsbursky <skinsbursky-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>

---
 net/sunrpc/rpc_pipe.c |   32 +++++++++++++++++++-------------
 1 files changed, 19 insertions(+), 13 deletions(-)

diff --git a/net/sunrpc/rpc_pipe.c b/net/sunrpc/rpc_pipe.c
index 6873c9b..b67b2ae 100644
--- a/net/sunrpc/rpc_pipe.c
+++ b/net/sunrpc/rpc_pipe.c
@@ -174,6 +174,7 @@ rpc_close_pipes(struct inode *inode)
 		pipe->ops->release_pipe(inode);
 	cancel_delayed_work_sync(&pipe->queue_timeout);
 	rpc_inode_setowner(inode, NULL);
+	RPC_I(inode)->pipe = NULL;
 	mutex_unlock(&inode->i_mutex);
 }
 
@@ -203,12 +204,13 @@ rpc_destroy_inode(struct inode *inode)
 static int
 rpc_pipe_open(struct inode *inode, struct file *filp)
 {
-	struct rpc_pipe *pipe = RPC_I(inode)->pipe;
+	struct rpc_pipe *pipe;
 	int first_open;
 	int res = -ENXIO;
 
 	mutex_lock(&inode->i_mutex);
-	if (pipe->dentry == NULL)
+	pipe = RPC_I(inode)->pipe;
+	if (pipe == NULL)
 		goto out;
 	first_open = pipe->nreaders == 0 && pipe->nwriters == 0;
 	if (first_open && pipe->ops->open_pipe) {
@@ -229,12 +231,13 @@ out:
 static int
 rpc_pipe_release(struct inode *inode, struct file *filp)
 {
-	struct rpc_pipe *pipe = RPC_I(inode)->pipe;
+	struct rpc_pipe *pipe;
 	struct rpc_pipe_msg *msg;
 	int last_close;
 
 	mutex_lock(&inode->i_mutex);
-	if (pipe->dentry == NULL)
+	pipe = RPC_I(inode)->pipe;
+	if (pipe == NULL)
 		goto out;
 	msg = filp->private_data;
 	if (msg != NULL) {
@@ -270,12 +273,13 @@ static ssize_t
 rpc_pipe_read(struct file *filp, char __user *buf, size_t len, loff_t *offset)
 {
 	struct inode *inode = filp->f_path.dentry->d_inode;
-	struct rpc_pipe *pipe = RPC_I(inode)->pipe;
+	struct rpc_pipe *pipe;
 	struct rpc_pipe_msg *msg;
 	int res = 0;
 
 	mutex_lock(&inode->i_mutex);
-	if (pipe->dentry == NULL) {
+	pipe = RPC_I(inode)->pipe;
+	if (pipe == NULL) {
 		res = -EPIPE;
 		goto out_unlock;
 	}
@@ -313,13 +317,12 @@ static ssize_t
 rpc_pipe_write(struct file *filp, const char __user *buf, size_t len, loff_t *offset)
 {
 	struct inode *inode = filp->f_path.dentry->d_inode;
-	struct rpc_pipe *pipe = RPC_I(inode)->pipe;
 	int res;
 
 	mutex_lock(&inode->i_mutex);
 	res = -EPIPE;
-	if (pipe->dentry != NULL)
-		res = pipe->ops->downcall(filp, buf, len);
+	if (RPC_I(inode)->pipe != NULL)
+		res = RPC_I(inode)->pipe->ops->downcall(filp, buf, len);
 	mutex_unlock(&inode->i_mutex);
 	return res;
 }
@@ -344,16 +347,18 @@ static long
 rpc_pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 {
 	struct inode *inode = filp->f_path.dentry->d_inode;
-	struct rpc_pipe *pipe = RPC_I(inode)->pipe;
+	struct rpc_pipe *pipe;
 	int len;
 
 	switch (cmd) {
 	case FIONREAD:
-		spin_lock(&pipe->lock);
-		if (pipe->dentry == NULL) {
-			spin_unlock(&pipe->lock);
+		mutex_lock(&inode->i_mutex);
+		pipe = RPC_I(inode)->pipe;
+		if (pipe == NULL) {
+			mutex_unlock(&inode->i_mutex);
 			return -EPIPE;
 		}
+		spin_lock(&pipe->lock);
 		len = pipe->pipelen;
 		if (filp->private_data) {
 			struct rpc_pipe_msg *msg;
@@ -361,6 +366,7 @@ rpc_pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 			len += msg->len - msg->copied;
 		}
 		spin_unlock(&pipe->lock);
+		mutex_unlock(&inode->i_mutex);
 		return put_user(len, (int __user *)arg);
 	default:
 		return -EINVAL;

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[PATCH 4/4] SUNRPC: move waitq from RPC pipe to RPC inode

[Stanislav Kinsbursky]

Currently, wait queue, used for polling of RPC pipe changes from user-space,
is a part of RPC pipe. But the pipe data itself can be released on NFS umount
prior to dentry-inode pair, connected to it (is case of this pair is open by
some process).
This is not a problem for almost all pipe users, because all PipeFS file
operations checks pipe reference prior to using it.
Except evenfd. This thing registers itself with "poll" file operation and thus
has a reference to pipe wait queue. This leads to oopses on destroying eventfd
after NFS umount (like rpc_idmapd do) since not pipe data left to the point
already.
The solution is to wait queue from pipe data to internal RPC inode data. This
looks more logical, because this wiat queue used only for user-space processes,
which already holds inode reference.

Note: upcalls have to get pipe->dentry prior to dereferecing wait queue to make
sure, that mount point won't disappear from underneath us.

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

---
 include/linux/sunrpc/rpc_pipe_fs.h |    2 +-
 net/sunrpc/rpc_pipe.c              |   39 ++++++++++++++++++++++++------------
 2 files changed, 27 insertions(+), 14 deletions(-)

diff --git a/include/linux/sunrpc/rpc_pipe_fs.h b/include/linux/sunrpc/rpc_pipe_fs.h
index 426ce6e..a7b422b 100644
--- a/include/linux/sunrpc/rpc_pipe_fs.h
+++ b/include/linux/sunrpc/rpc_pipe_fs.h
@@ -28,7 +28,6 @@ struct rpc_pipe {
 	int pipelen;
 	int nreaders;
 	int nwriters;
-	wait_queue_head_t waitq;
 #define RPC_PIPE_WAIT_FOR_OPEN	1
 	int flags;
 	struct delayed_work queue_timeout;
@@ -41,6 +40,7 @@ struct rpc_inode {
 	struct inode vfs_inode;
 	void *private;
 	struct rpc_pipe *pipe;
+	wait_queue_head_t waitq;
 };
 
 static inline struct rpc_inode *
diff --git a/net/sunrpc/rpc_pipe.c b/net/sunrpc/rpc_pipe.c
index b67b2ae..ac9ee15 100644
--- a/net/sunrpc/rpc_pipe.c
+++ b/net/sunrpc/rpc_pipe.c
@@ -57,7 +57,7 @@ void rpc_pipefs_notifier_unregister(struct notifier_block *nb)
 }
 EXPORT_SYMBOL_GPL(rpc_pipefs_notifier_unregister);
 
-static void rpc_purge_list(struct rpc_pipe *pipe, struct list_head *head,
+static void rpc_purge_list(wait_queue_head_t *waitq, struct list_head *head,
 		void (*destroy_msg)(struct rpc_pipe_msg *), int err)
 {
 	struct rpc_pipe_msg *msg;
@@ -70,7 +70,7 @@ static void rpc_purge_list(struct rpc_pipe *pipe, struct list_head *head,
 		msg->errno = err;
 		destroy_msg(msg);
 	} while (!list_empty(head));
-	wake_up(&pipe->waitq);
+	wake_up(waitq);
 }
 
 static void
@@ -80,6 +80,7 @@ rpc_timeout_upcall_queue(struct work_struct *work)
 	struct rpc_pipe *pipe =
 		container_of(work, struct rpc_pipe, queue_timeout.work);
 	void (*destroy_msg)(struct rpc_pipe_msg *);
+	struct dentry *dentry;
 
 	spin_lock(&pipe->lock);
 	destroy_msg = pipe->ops->destroy_msg;
@@ -87,8 +88,13 @@ rpc_timeout_upcall_queue(struct work_struct *work)
 		list_splice_init(&pipe->pipe, &free_list);
 		pipe->pipelen = 0;
 	}
+	dentry = dget(pipe->dentry);
 	spin_unlock(&pipe->lock);
-	rpc_purge_list(pipe, &free_list, destroy_msg, -ETIMEDOUT);
+	if (dentry) {
+		rpc_purge_list(&RPC_I(dentry->d_inode)->waitq,
+			       &free_list, destroy_msg, -ETIMEDOUT);
+		dput(dentry);
+	}
 }
 
 ssize_t rpc_pipe_generic_upcall(struct file *filp, struct rpc_pipe_msg *msg,
@@ -125,6 +131,7 @@ int
 rpc_queue_upcall(struct rpc_pipe *pipe, struct rpc_pipe_msg *msg)
 {
 	int res = -EPIPE;
+	struct dentry *dentry;
 
 	spin_lock(&pipe->lock);
 	if (pipe->nreaders) {
@@ -140,8 +147,12 @@ rpc_queue_upcall(struct rpc_pipe *pipe, struct rpc_pipe_msg *msg)
 		pipe->pipelen += msg->len;
 		res = 0;
 	}
+	dentry = dget(pipe->dentry);
 	spin_unlock(&pipe->lock);
-	wake_up(&pipe->waitq);
+	if (dentry) {
+		wake_up(&RPC_I(dentry->d_inode)->waitq);
+		dput(dentry);
+	}
 	return res;
 }
 EXPORT_SYMBOL_GPL(rpc_queue_upcall);
@@ -168,7 +179,7 @@ rpc_close_pipes(struct inode *inode)
 	pipe->pipelen = 0;
 	pipe->dentry = NULL;
 	spin_unlock(&pipe->lock);
-	rpc_purge_list(pipe, &free_list, pipe->ops->destroy_msg, -EPIPE);
+	rpc_purge_list(&RPC_I(inode)->waitq, &free_list, pipe->ops->destroy_msg, -EPIPE);
 	pipe->nwriters = 0;
 	if (need_release && pipe->ops->release_pipe)
 		pipe->ops->release_pipe(inode);
@@ -257,7 +268,7 @@ rpc_pipe_release(struct inode *inode, struct file *filp)
 			list_splice_init(&pipe->pipe, &free_list);
 			pipe->pipelen = 0;
 			spin_unlock(&pipe->lock);
-			rpc_purge_list(pipe, &free_list,
+			rpc_purge_list(&RPC_I(inode)->waitq, &free_list,
 					pipe->ops->destroy_msg, -EAGAIN);
 		}
 	}
@@ -330,16 +341,18 @@ rpc_pipe_write(struct file *filp, const char __user *buf, size_t len, loff_t *of
 static unsigned int
 rpc_pipe_poll(struct file *filp, struct poll_table_struct *wait)
 {
-	struct rpc_pipe *pipe = RPC_I(filp->f_path.dentry->d_inode)->pipe;
-	unsigned int mask = 0;
+	struct inode *inode = filp->f_path.dentry->d_inode;
+	struct rpc_inode *rpci = RPC_I(inode);
+	unsigned int mask = POLLOUT | POLLWRNORM;
 
-	poll_wait(filp, &pipe->waitq, wait);
+	poll_wait(filp, &rpci->waitq, wait);
 
-	mask = POLLOUT | POLLWRNORM;
-	if (pipe->dentry == NULL)
+	mutex_lock(&inode->i_mutex);
+	if (rpci->pipe == NULL)
 		mask |= POLLERR | POLLHUP;
-	if (filp->private_data || !list_empty(&pipe->pipe))
+	else if (filp->private_data || !list_empty(&rpci->pipe->pipe))
 		mask |= POLLIN | POLLRDNORM;
+	mutex_unlock(&inode->i_mutex);
 	return mask;
 }
 
@@ -543,7 +556,6 @@ init_pipe(struct rpc_pipe *pipe)
 	INIT_LIST_HEAD(&pipe->in_downcall);
 	INIT_LIST_HEAD(&pipe->pipe);
 	pipe->pipelen = 0;
-	init_waitqueue_head(&pipe->waitq);
 	INIT_DELAYED_WORK(&pipe->queue_timeout,
 			    rpc_timeout_upcall_queue);
 	pipe->ops = NULL;
@@ -1165,6 +1177,7 @@ init_once(void *foo)
 	inode_init_once(&rpci->vfs_inode);
 	rpci->private = NULL;
 	rpci->pipe = NULL;
+	init_waitqueue_head(&rpci->waitq);
 }
 
 int register_rpc_pipefs(void)