/*
 * net/sunrpc/rpc_pipe.c
 *
 * Userland/kernel interface for rpcauth_gss.
 * Code shamelessly plagiarized from fs/nfsd/nfsctl.c
 * and fs/sysfs/inode.c
 *
 * Copyright (c) 2002, Trond Myklebust <trond.myklebust@fys.uio.no>
 *
 */
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/pagemap.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/fsnotify.h>
#include <linux/kernel.h>

#include <asm/ioctls.h>
#include <linux/fs.h>
#include <linux/poll.h>
#include <linux/wait.h>
#include <linux/seq_file.h>

#include <linux/sunrpc/clnt.h>
#include <linux/workqueue.h>
#include <linux/sunrpc/rpc_pipe_fs.h>
#include <linux/sunrpc/cache.h>

static struct vfsmount *rpc_mount __read_mostly;
static int rpc_mount_count;

static struct file_system_type rpc_pipe_fs_type;


static struct kmem_cache *rpc_inode_cachep __read_mostly;

#define RPC_UPCALL_TIMEOUT (30*HZ)

static void rpc_purge_list(struct rpc_inode *rpci, struct list_head *head,
		void (*destroy_msg)(struct rpc_pipe_msg *), int err)
{
	struct rpc_pipe_msg *msg;

	if (list_empty(head))
		return;
	do {
		msg = list_entry(head->next, struct rpc_pipe_msg, list);
		list_del_init(&msg->list);
		msg->errno = err;
		destroy_msg(msg);
	} while (!list_empty(head));
	wake_up(&rpci->waitq);
}

static void
rpc_timeout_upcall_queue(struct work_struct *work)
{
	LIST_HEAD(free_list);
	struct rpc_inode *rpci =
		container_of(work, struct rpc_inode, queue_timeout.work);
	struct inode *inode = &rpci->vfs_inode;
	void (*destroy_msg)(struct rpc_pipe_msg *);

	spin_lock(&inode->i_lock);
	if (rpci->ops == NULL) {
		spin_unlock(&inode->i_lock);
		return;
	}
	destroy_msg = rpci->ops->destroy_msg;
	if (rpci->nreaders == 0) {
		list_splice_init(&rpci->pipe, &free_list);
		rpci->pipelen = 0;
	}
	spin_unlock(&inode->i_lock);
	rpc_purge_list(rpci, &free_list, destroy_msg, -ETIMEDOUT);
}

/**
 * rpc_queue_upcall - queue an upcall message to userspace
 * @inode: inode of upcall pipe on which to queue given message
 * @msg: message to queue
 *
 * Call with an @inode created by rpc_mkpipe() to queue an upcall.
 * A userspace process may then later read the upcall by performing a
 * read on an open file for this inode.  It is up to the caller to
 * initialize the fields of @msg (other than @msg->list) appropriately.
 */
int
rpc_queue_upcall(struct inode *inode, struct rpc_pipe_msg *msg)
{
	struct rpc_inode *rpci = RPC_I(inode);
	int res = -EPIPE;

	spin_lock(&inode->i_lock);
	if (rpci->ops == NULL)
		goto out;
	if (rpci->nreaders) {
		list_add_tail(&msg->list, &rpci->pipe);
		rpci->pipelen += msg->len;
		res = 0;
	} else if (rpci->flags & RPC_PIPE_WAIT_FOR_OPEN) {
		if (list_empty(&rpci->pipe))
			queue_delayed_work(rpciod_workqueue,
					&rpci->queue_timeout,
					RPC_UPCALL_TIMEOUT);
		list_add_tail(&msg->list, &rpci->pipe);
		rpci->pipelen += msg->len;
		res = 0;
	}
out:
	spin_unlock(&inode->i_lock);
	wake_up(&rpci->waitq);
	return res;
}
EXPORT_SYMBOL_GPL(rpc_queue_upcall);

static inline void
rpc_inode_setowner(struct inode *inode, void *private)
{
	RPC_I(inode)->private = private;
}

static void
rpc_close_pipes(struct inode *inode)
{
	struct rpc_inode *rpci = RPC_I(inode);
	const struct rpc_pipe_ops *ops;
	int need_release;

	mutex_lock(&inode->i_mutex);
	ops = rpci->ops;
	if (ops != NULL) {
		LIST_HEAD(free_list);
		spin_lock(&inode->i_lock);
		need_release = rpci->nreaders != 0 || rpci->nwriters != 0;
		rpci->nreaders = 0;
		list_splice_init(&rpci->in_upcall, &free_list);
		list_splice_init(&rpci->pipe, &free_list);
		rpci->pipelen = 0;
		rpci->ops = NULL;
		spin_unlock(&inode->i_lock);
		rpc_purge_list(rpci, &free_list, ops->destroy_msg, -EPIPE);
		rpci->nwriters = 0;
		if (need_release && ops->release_pipe)
			ops->release_pipe(inode);
		cancel_delayed_work_sync(&rpci->queue_timeout);
	}
	rpc_inode_setowner(inode, NULL);
	mutex_unlock(&inode->i_mutex);
}

static struct inode *
rpc_alloc_inode(struct super_block *sb)
{
	struct rpc_inode *rpci;
	rpci = (struct rpc_inode *)kmem_cache_alloc(rpc_inode_cachep, GFP_KERNEL);
	if (!rpci)
		return NULL;
	return &rpci->vfs_inode;
}

static void
rpc_destroy_inode(struct inode *inode)
{
	kmem_cache_free(rpc_inode_cachep, RPC_I(inode));
}

static int
rpc_pipe_open(struct inode *inode, struct file *filp)
{
	struct rpc_inode *rpci = RPC_I(inode);
	int first_open;
	int res = -ENXIO;

	mutex_lock(&inode->i_mutex);
	if (rpci->ops == NULL)
		goto out;
	first_open = rpci->nreaders == 0 && rpci->nwriters == 0;
	if (first_open && rpci->ops->open_pipe) {
		res = rpci->ops->open_pipe(inode);
		if (res)
			goto out;
	}
	if (filp->f_mode & FMODE_READ)
		rpci->nreaders++;
	if (filp->f_mode & FMODE_WRITE)
		rpci->nwriters++;
	res = 0;
out:
	mutex_unlock(&inode->i_mutex);
	return res;
}

static int