SUNRPC: fix pipe->ops cleanup on pipe dentry unlink

This patch looks late due to GSS AUTH patches sent already. But it fixes a flaw
in RPC PipeFS pipes handling.
I've added this patch in the series, because this series related to pipes. But
it should be a part of previous series named "SUNPRC: cleanup PipeFS for
network-namespace-aware users".

Pipe dentry can be created and destroyed many times during pipe life cycle.
This actually means, that we can't set pipe->ops to NULL in rpc_close_pipes()
and use this variable as a flag, indicating, that pipe's dentry is unlinking.
To follow this restriction, this patch replaces "pipe->ops = NULL" assignment
and checks for NULL with "pipe->dentry = NULL" assignment and checks for
NULL respectively.
This patch also removes check for non-NULL pipe->ops (or pipe->dentry) in
rpc_close_pipes() because it always non-NULL now.

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

1 files changed, 20 insertions, 31 deletions

diff --git a/net/sunrpc/rpc_pipe.c b/net/sunrpc/rpc_pipe.c
index 910de4169a8d..6b417fcabdbf 100644
--- a/net/sunrpc/rpc_pipe.c
+++ b/net/sunrpc/rpc_pipe.c
@@ -86,10 +86,6 @@ rpc_timeout_upcall_queue(struct work_struct *work)
         void (*destroy_msg)(struct rpc_pipe_msg *);
 
         spin_lock(&pipe->lock);
-        if (pipe->ops == NULL) {
-                spin_unlock(&pipe->lock);
-                return;
-        }
         destroy_msg = pipe->ops->destroy_msg;
         if (pipe->nreaders == 0) {
                 list_splice_init(&pipe->pipe, &free_list);
@@ -135,8 +131,6 @@ rpc_queue_upcall(struct rpc_pipe *pipe, struct rpc_pipe_msg *msg)
         int res = -EPIPE;
 
         spin_lock(&pipe->lock);
-        if (pipe->ops == NULL)
-                goto out;
         if (pipe->nreaders) {
                 list_add_tail(&msg->list, &pipe->pipe);
                 pipe->pipelen += msg->len;
@@ -150,7 +144,6 @@ rpc_queue_upcall(struct rpc_pipe *pipe, struct rpc_pipe_msg *msg)
                 pipe->pipelen += msg->len;
                 res = 0;
         }
-out:
         spin_unlock(&pipe->lock);
         wake_up(&pipe->waitq);
         return res;
@@ -167,27 +160,23 @@ static void
 rpc_close_pipes(struct inode *inode)
 {
         struct rpc_pipe *pipe = RPC_I(inode)->pipe;
-        const struct rpc_pipe_ops *ops;
         int need_release;
+        LIST_HEAD(free_list);
 
         mutex_lock(&inode->i_mutex);
-        ops = pipe->ops;
-        if (ops != NULL) {
-                LIST_HEAD(free_list);
-                spin_lock(&pipe->lock);
-                need_release = pipe->nreaders != 0 || pipe->nwriters != 0;
-                pipe->nreaders = 0;
-                list_splice_init(&pipe->in_upcall, &free_list);
-                list_splice_init(&pipe->pipe, &free_list);
-                pipe->pipelen = 0;
-                pipe->ops = NULL;
-                spin_unlock(&pipe->lock);
-                rpc_purge_list(pipe, &free_list, ops->destroy_msg, -EPIPE);
-                pipe->nwriters = 0;
-                if (need_release && ops->release_pipe)
-                        ops->release_pipe(inode);
-                cancel_delayed_work_sync(&pipe->queue_timeout);
-        }
+        spin_lock(&pipe->lock);
+        need_release = pipe->nreaders != 0 || pipe->nwriters != 0;
+        pipe->nreaders = 0;
+        list_splice_init(&pipe->in_upcall, &free_list);
+        list_splice_init(&pipe->pipe, &free_list);
+        pipe->pipelen = 0;
+        pipe->dentry = NULL;
+        spin_unlock(&pipe->lock);
+        rpc_purge_list(pipe, &free_list, pipe->ops->destroy_msg, -EPIPE);
+        pipe->nwriters = 0;
+        if (need_release && pipe->ops->release_pipe)
+                pipe->ops->release_pipe(inode);
+        cancel_delayed_work_sync(&pipe->queue_timeout);
         rpc_inode_setowner(inode, NULL);
         mutex_unlock(&inode->i_mutex);
 }
@@ -223,7 +212,7 @@ rpc_pipe_open(struct inode *inode, struct file *filp)
         int res = -ENXIO;
 
         mutex_lock(&inode->i_mutex);
-        if (pipe->ops == NULL)
+        if (pipe->dentry == NULL)
                 goto out;
         first_open = pipe->nreaders == 0 && pipe->nwriters == 0;
         if (first_open && pipe->ops->open_pipe) {
@@ -249,7 +238,7 @@ rpc_pipe_release(struct inode *inode, struct file *filp)
         int last_close;
 
         mutex_lock(&inode->i_mutex);
-        if (pipe->ops == NULL)
+        if (pipe->dentry == NULL)
                 goto out;
         msg = filp->private_data;
         if (msg != NULL) {
@@ -290,7 +279,7 @@ rpc_pipe_read(struct file *filp, char __user *buf, size_t len, loff_t *offset)
         int res = 0;
 
         mutex_lock(&inode->i_mutex);
-        if (pipe->ops == NULL) {
+        if (pipe->dentry == NULL) {
                 res = -EPIPE;
                 goto out_unlock;
         }
@@ -333,7 +322,7 @@ rpc_pipe_write(struct file *filp, const char __user *buf, size_t len, loff_t *of
 
         mutex_lock(&inode->i_mutex);
         res = -EPIPE;
-        if (pipe->ops != NULL)
+        if (pipe->dentry != NULL)
                 res = pipe->ops->downcall(filp, buf, len);
         mutex_unlock(&inode->i_mutex);
         return res;
@@ -348,7 +337,7 @@ rpc_pipe_poll(struct file *filp, struct poll_table_struct *wait)
         poll_wait(filp, &pipe->waitq, wait);
 
         mask = POLLOUT | POLLWRNORM;
-        if (pipe->ops == NULL)
+        if (pipe->dentry == NULL)
                 mask |= POLLERR | POLLHUP;
         if (filp->private_data || !list_empty(&pipe->pipe))
                 mask |= POLLIN | POLLRDNORM;
@@ -365,7 +354,7 @@ rpc_pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
         switch (cmd) {
         case FIONREAD:
                 spin_lock(&pipe->lock);
-                if (pipe->ops == NULL) {
+                if (pipe->dentry == NULL) {
                         spin_unlock(&pipe->lock);
                         return -EPIPE;
                 }