mqueue: sys_mq_open: do not call mnt_drop_write() if read-only

[linux-2.6/cjktty.git] / net / sunrpc / rpc_pipe.c

/*
 * 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 <linux/rcupdate.h>

#include <asm/ioctls.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>
#include <linux/nsproxy.h>
#include <linux/notifier.h>

#include "netns.h"
#include "sunrpc.h"

#define RPCDBG_FACILITY RPCDBG_DEBUG

#define NET_NAME(net)   ((net == &init_net) ? " (init_net)" : "")

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 BLOCKING_NOTIFIER_HEAD(rpc_pipefs_notifier_list);

int rpc_pipefs_notifier_register(struct notifier_block *nb)
{
        return blocking_notifier_chain_cond_register(&rpc_pipefs_notifier_list, nb);
}
EXPORT_SYMBOL_GPL(rpc_pipefs_notifier_register);

void rpc_pipefs_notifier_unregister(struct notifier_block *nb)
{
        blocking_notifier_chain_unregister(&rpc_pipefs_notifier_list, nb);
}
EXPORT_SYMBOL_GPL(rpc_pipefs_notifier_unregister);

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;

        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));

        if (waitq)
                wake_up(waitq);
}

static void
rpc_timeout_upcall_queue(struct work_struct *work)
{
        LIST_HEAD(free_list);
        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;
        if (pipe->nreaders == 0) {
                list_splice_init(&pipe->pipe, &free_list);
                pipe->pipelen = 0;
        }
        dentry = dget(pipe->dentry);
        spin_unlock(&pipe->lock);
        rpc_purge_list(dentry ? &RPC_I(dentry->d_inode)->waitq : NULL,
                        &free_list, destroy_msg, -ETIMEDOUT);
        dput(dentry);
}

ssize_t rpc_pipe_generic_upcall(struct file *filp, struct rpc_pipe_msg *msg,
                                char __user *dst, size_t buflen)
{
        char *data = (char *)msg->data + msg->copied;
        size_t mlen = min(msg->len - msg->copied, buflen);
        unsigned long left;

        left = copy_to_user(dst, data, mlen);
        if (left == mlen) {
                msg->errno = -EFAULT;
                return -EFAULT;
        }

        mlen -= left;
        msg->copied += mlen;
        msg->errno = 0;
        return mlen;
}
EXPORT_SYMBOL_GPL(rpc_pipe_generic_upcall);

/**
 * rpc_queue_upcall - queue an upcall message to userspace
 * @pipe: 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 rpc_pipe *pipe, struct rpc_pipe_msg *msg)
{
        int res = -EPIPE;
        struct dentry *dentry;

        spin_lock(&pipe->lock);
        if (pipe->nreaders) {
                list_add_tail(&msg->list, &pipe->pipe);
                pipe->pipelen += msg->len;
                res = 0;
        } else if (pipe->flags & RPC_PIPE_WAIT_FOR_OPEN) {
                if (list_empty(&pipe->pipe))
                        queue_delayed_work(rpciod_workqueue,
                                        &pipe->queue_timeout,
                                        RPC_UPCALL_TIMEOUT);
                list_add_tail(&msg->list, &pipe->pipe);
                pipe->pipelen += msg->len;
                res = 0;
        }
        dentry = dget(pipe->dentry);
        spin_unlock(&pipe->lock);
        if (dentry) {
                wake_up(&RPC_I(dentry->d_inode)->waitq);
                dput(dentry);
        }
        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_pipe *pipe = RPC_I(inode)->pipe;
        int need_release;
        LIST_HEAD(free_list);

        mutex_lock(&inode->i_mutex);
        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(&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);
        cancel_delayed_work_sync(&pipe->queue_timeout);
        rpc_inode_setowner(inode, NULL);
        RPC_I(inode)->pipe = 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_i_callback(struct rcu_head *head)
{
        struct inode *inode = container_of(head, struct inode, i_rcu);
        kmem_cache_free(rpc_inode_cachep, RPC_I(inode));
}

static void
rpc_destroy_inode(struct inode *inode)
{
        call_rcu(&inode->i_rcu, rpc_i_callback);
}

static int
rpc_pipe_open(struct inode *inode, struct file *filp)
{
        struct rpc_pipe *pipe;
        int first_open;
        int res = -ENXIO;

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

static int
rpc_pipe_release(struct inode *inode, struct file *filp)
{
        struct rpc_pipe *pipe;
        struct rpc_pipe_msg *msg;
        int last_close;

        mutex_lock(&inode->i_mutex);
        pipe = RPC_I(inode)->pipe;
        if (pipe == NULL)
                goto out;
        msg = filp->private_data;
        if (msg != NULL) {
                spin_lock(&pipe->lock);
                msg->errno = -EAGAIN;
                list_del_init(&msg->list);
                spin_unlock(&pipe->lock);
                pipe->ops->destroy_msg(msg);
        }
        if (filp->f_mode & FMODE_WRITE)
                pipe->nwriters --;
        if (filp->f_mode & FMODE_READ) {
                pipe->nreaders --;
                if (pipe->nreaders == 0) {
                        LIST_HEAD(free_list);
                        spin_lock(&pipe->lock);
                        list_splice_init(&pipe->pipe, &free_list);
                        pipe->pipelen = 0;
                        spin_unlock(&pipe->lock);
                        rpc_purge_list(&RPC_I(inode)->waitq, &free_list,
                                        pipe->ops->destroy_msg, -EAGAIN);
                }
        }
        last_close = pipe->nwriters == 0 && pipe->nreaders == 0;
        if (last_close && pipe->ops->release_pipe)
                pipe->ops->release_pipe(inode);
out:
        mutex_unlock(&inode->i_mutex);
        return 0;
}

static ssize_t
rpc_pipe_read(struct file *filp, char __user *buf, size_t len, loff_t *offset)
{
        struct inode *inode = file_inode(filp);
        struct rpc_pipe *pipe;
        struct rpc_pipe_msg *msg;
        int res = 0;

        mutex_lock(&inode->i_mutex);
        pipe = RPC_I(inode)->pipe;
        if (pipe == NULL) {
                res = -EPIPE;
                goto out_unlock;
        }
        msg = filp->private_data;
        if (msg == NULL) {
                spin_lock(&pipe->lock);
                if (!list_empty(&pipe->pipe)) {
                        msg = list_entry(pipe->pipe.next,
                                        struct rpc_pipe_msg,
                                        list);
                        list_move(&msg->list, &pipe->in_upcall);
                        pipe->pipelen -= msg->len;
                        filp->private_data = msg;
                        msg->copied = 0;
                }
                spin_unlock(&pipe->lock);
                if (msg == NULL)
                        goto out_unlock;
        }
        /* NOTE: it is up to the callback to update msg->copied */
        res = pipe->ops->upcall(filp, msg, buf, len);
        if (res < 0 || msg->len == msg->copied) {
                filp->private_data = NULL;
                spin_lock(&pipe->lock);
                list_del_init(&msg->list);
                spin_unlock(&pipe->lock);
                pipe->ops->destroy_msg(msg);
        }
out_unlock:
        mutex_unlock(&inode->i_mutex);
        return res;
}

static ssize_t
rpc_pipe_write(struct file *filp, const char __user *buf, size_t len, loff_t *offset)
{
        struct inode *inode = file_inode(filp);
        int res;

        mutex_lock(&inode->i_mutex);
        res = -EPIPE;
        if (RPC_I(inode)->pipe != NULL)
                res = RPC_I(inode)->pipe->ops->downcall(filp, buf, len);
        mutex_unlock(&inode->i_mutex);
        return res;
}

static unsigned int
rpc_pipe_poll(struct file *filp, struct poll_table_struct *wait)
{
        struct inode *inode = file_inode(filp);
        struct rpc_inode *rpci = RPC_I(inode);
        unsigned int mask = POLLOUT | POLLWRNORM;

        poll_wait(filp, &rpci->waitq, wait);

        mutex_lock(&inode->i_mutex);
        if (rpci->pipe == NULL)
                mask |= POLLERR | POLLHUP;
        else if (filp->private_data || !list_empty(&rpci->pipe->pipe))
                mask |= POLLIN | POLLRDNORM;
        mutex_unlock(&inode->i_mutex);
        return mask;
}

static long
rpc_pipe_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
        struct inode *inode = file_inode(filp);
        struct rpc_pipe *pipe;
        int len;

        switch (cmd) {
        case FIONREAD:
                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;
                        msg = filp->private_data;
                        len += msg->len - msg->copied;
                }
                spin_unlock(&pipe->lock);
                mutex_unlock(&inode->i_mutex);
                return put_user(len, (int __user *)arg);
        default:
                return -EINVAL;
        }
}

static const struct file_operations rpc_pipe_fops = {
        .owner          = THIS_MODULE,
        .llseek         = no_llseek,
        .read           = rpc_pipe_read,
        .write          = rpc_pipe_write,
        .poll           = rpc_pipe_poll,
        .unlocked_ioctl = rpc_pipe_ioctl,
        .open           = rpc_pipe_open,
        .release        = rpc_pipe_release,
};

static int
rpc_show_info(struct seq_file *m, void *v)
{
        struct rpc_clnt *clnt = m->private;

        rcu_read_lock();
        seq_printf(m, "RPC server: %s\n",
                        rcu_dereference(clnt->cl_xprt)->servername);
        seq_printf(m, "service: %s (%d) version %d\n", clnt->cl_protname,
                        clnt->cl_prog, clnt->cl_vers);
        seq_printf(m, "address: %s\n", rpc_peeraddr2str(clnt, RPC_DISPLAY_ADDR));
        seq_printf(m, "protocol: %s\n", rpc_peeraddr2str(clnt, RPC_DISPLAY_PROTO));
        seq_printf(m, "port: %s\n", rpc_peeraddr2str(clnt, RPC_DISPLAY_PORT));
        rcu_read_unlock();
        return 0;
}

static int
rpc_info_open(struct inode *inode, struct file *file)
{
        struct rpc_clnt *clnt = NULL;
        int ret = single_open(file, rpc_show_info, NULL);

        if (!ret) {
                struct seq_file *m = file->private_data;

                spin_lock(&file->f_path.dentry->d_lock);
                if (!d_unhashed(file->f_path.dentry))
                        clnt = RPC_I(inode)->private;
                if (clnt != NULL && atomic_inc_not_zero(&clnt->cl_count)) {
                        spin_unlock(&file->f_path.dentry->d_lock);
                        m->private = clnt;
                } else {
                        spin_unlock(&file->f_path.dentry->d_lock);
                        single_release(inode, file);
                        ret = -EINVAL;
                }
        }
        return ret;
}

static int
rpc_info_release(struct inode *inode, struct file *file)
{
        struct seq_file *m = file->private_data;
        struct rpc_clnt *clnt = (struct rpc_clnt *)m->private;

        if (clnt)
                rpc_release_client(clnt);
        return single_release(inode, file);
}

static const struct file_operations rpc_info_operations = {
        .owner          = THIS_MODULE,
        .open           = rpc_info_open,
        .read           = seq_read,
        .llseek         = seq_lseek,
        .release        = rpc_info_release,
};


/*
 * Description of fs contents.
 */
struct rpc_filelist {
        const char *name;
        const struct file_operations *i_fop;
        umode_t mode;
};

static int rpc_delete_dentry(const struct dentry *dentry)
{
        return 1;
}

static const struct dentry_operations rpc_dentry_operations = {
        .d_delete = rpc_delete_dentry,
};

static struct inode *
rpc_get_inode(struct super_block *sb, umode_t mode)
{
        struct inode *inode = new_inode(sb);
        if (!inode)
                return NULL;
        inode->i_ino = get_next_ino();
        inode->i_mode = mode;
        inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
        switch (mode & S_IFMT) {
        case S_IFDIR:
                inode->i_fop = &simple_dir_operations;
                inode->i_op = &simple_dir_inode_operations;
                inc_nlink(inode);
        default:
                break;
        }
        return inode;
}

static int __rpc_create_common(struct inode *dir, struct dentry *dentry,
                               umode_t mode,
                               const struct file_operations *i_fop,
                               void *private)
{
        struct inode *inode;

        d_drop(dentry);
        inode = rpc_get_inode(dir->i_sb, mode);
        if (!inode)
                goto out_err;
        inode->i_ino = iunique(dir->i_sb, 100);
        if (i_fop)
                inode->i_fop = i_fop;
        if (private)
                rpc_inode_setowner(inode, private);
        d_add(dentry, inode);
        return 0;
out_err:
        printk(KERN_WARNING "%s: %s failed to allocate inode for dentry %s\n",
                        __FILE__, __func__, dentry->d_name.name);
        dput(dentry);
        return -ENOMEM;
}

static int __rpc_create(struct inode *dir, struct dentry *dentry,
                        umode_t mode,
                        const struct file_operations *i_fop,
                        void *private)
{
        int err;

        err = __rpc_create_common(dir, dentry, S_IFREG | mode, i_fop, private);
        if (err)
                return err;
        fsnotify_create(dir, dentry);
        return 0;
}

static int __rpc_mkdir(struct inode *dir, struct dentry *dentry,
                       umode_t mode,
                       const struct file_operations *i_fop,
                       void *private)
{
        int err;

        err = __rpc_create_common(dir, dentry, S_IFDIR | mode, i_fop, private);
        if (err)
                return err;
        inc_nlink(dir);
        fsnotify_mkdir(dir, dentry);
        return 0;
}

static void
init_pipe(struct rpc_pipe *pipe)
{
        pipe->nreaders = 0;
        pipe->nwriters = 0;
        INIT_LIST_HEAD(&pipe->in_upcall);
        INIT_LIST_HEAD(&pipe->in_downcall);
        INIT_LIST_HEAD(&pipe->pipe);
        pipe->pipelen = 0;
        INIT_DELAYED_WORK(&pipe->queue_timeout,
                            rpc_timeout_upcall_queue);
        pipe->ops = NULL;
        spin_lock_init(&pipe->lock);
        pipe->dentry = NULL;
}

void rpc_destroy_pipe_data(struct rpc_pipe *pipe)
{
        kfree(pipe);
}
EXPORT_SYMBOL_GPL(rpc_destroy_pipe_data);

struct rpc_pipe *rpc_mkpipe_data(const struct rpc_pipe_ops *ops, int flags)
{
        struct rpc_pipe *pipe;

        pipe = kzalloc(sizeof(struct rpc_pipe), GFP_KERNEL);
        if (!pipe)
                return ERR_PTR(-ENOMEM);
        init_pipe(pipe);
        pipe->ops = ops;
        pipe->flags = flags;
        return pipe;
}
EXPORT_SYMBOL_GPL(rpc_mkpipe_data);

static int __rpc_mkpipe_dentry(struct inode *dir, struct dentry *dentry,
                               umode_t mode,
                               const struct file_operations *i_fop,
                               void *private,
                               struct rpc_pipe *pipe)
{
        struct rpc_inode *rpci;
        int err;

        err = __rpc_create_common(dir, dentry, S_IFIFO | mode, i_fop, private);
        if (err)
                return err;
        rpci = RPC_I(dentry->d_inode);
        rpci->private = private;
        rpci->pipe = pipe;
        fsnotify_create(dir, dentry);
        return 0;
}

static int __rpc_rmdir(struct inode *dir, struct dentry *dentry)
{
        int ret;

        dget(dentry);
        ret = simple_rmdir(dir, dentry);
        d_delete(dentry);
        dput(dentry);
        return ret;
}

int rpc_rmdir(struct dentry *dentry)
{
        struct dentry *parent;
        struct inode *dir;
        int error;

        parent = dget_parent(dentry);
        dir = parent->d_inode;
        mutex_lock_nested(&dir->i_mutex, I_MUTEX_PARENT);
        error = __rpc_rmdir(dir, dentry);
        mutex_unlock(&dir->i_mutex);
        dput(parent);
        return error;
}
EXPORT_SYMBOL_GPL(rpc_rmdir);

static int __rpc_unlink(struct inode *dir, struct dentry *dentry)
{
        int ret;

        dget(dentry);
        ret = simple_unlink(dir, dentry);
        d_delete(dentry);
        dput(dentry);
        return ret;
}

static int __rpc_rmpipe(struct inode *dir, struct dentry *dentry)
{
        struct inode *inode = dentry->d_inode;

        rpc_close_pipes(inode);
        return __rpc_unlink(dir, dentry);
}

static struct dentry *__rpc_lookup_create_exclusive(struct dentry *parent,
                                          struct qstr *name)
{
        struct dentry *dentry;

        dentry = d_lookup(parent, name);
        if (!dentry) {
                dentry = d_alloc(parent, name);
                if (!dentry)
                        return ERR_PTR(-ENOMEM);
        }
        if (dentry->d_inode == NULL) {
                d_set_d_op(dentry, &rpc_dentry_operations);
                return dentry;
        }
        dput(dentry);
        return ERR_PTR(-EEXIST);
}

/*
 * FIXME: This probably has races.
 */
static void __rpc_depopulate(struct dentry *parent,
                             const struct rpc_filelist *files,
                             int start, int eof)
{
        struct inode *dir = parent->d_inode;
        struct dentry *dentry;
        struct qstr name;
        int i;

        for (i = start; i < eof; i++) {
                name.name = files[i].name;
                name.len = strlen(files[i].name);
                name.hash = full_name_hash(name.name, name.len);
                dentry = d_lookup(parent, &name);

                if (dentry == NULL)
                        continue;
                if (dentry->d_inode == NULL)
                        goto next;
                switch (dentry->d_inode->i_mode & S_IFMT) {
                        default:
                                BUG();
                        case S_IFREG:
                                __rpc_unlink(dir, dentry);
                                break;
                        case S_IFDIR:
                                __rpc_rmdir(dir, dentry);
                }
next:
                dput(dentry);
        }
}

static void rpc_depopulate(struct dentry *parent,
                           const struct rpc_filelist *files,
                           int start, int eof)
{
        struct inode *dir = parent->d_inode;

        mutex_lock_nested(&dir->i_mutex, I_MUTEX_CHILD);
        __rpc_depopulate(parent, files, start, eof);
        mutex_unlock(&dir->i_mutex);
}

static int rpc_populate(struct dentry *parent,
                        const struct rpc_filelist *files,
                        int start, int eof,
                        void *private)
{
        struct inode *dir = parent->d_inode;
        struct dentry *dentry;
        int i, err;

        mutex_lock(&dir->i_mutex);
        for (i = start; i < eof; i++) {
                struct qstr q;

                q.name = files[i].name;
                q.len = strlen(files[i].name);
                q.hash = full_name_hash(q.name, q.len);
                dentry = __rpc_lookup_create_exclusive(parent, &q);
                err = PTR_ERR(dentry);
                if (IS_ERR(dentry))
                        goto out_bad;
                switch (files[i].mode & S_IFMT) {
                        default:
                                BUG();
                        case S_IFREG:
                                err = __rpc_create(dir, dentry,
                                                files[i].mode,
                                                files[i].i_fop,
                                                private);
                                break;
                        case S_IFDIR:
                                err = __rpc_mkdir(dir, dentry,
                                                files[i].mode,
                                                NULL,
                                                private);
                }
                if (err != 0)
                        goto out_bad;
        }
        mutex_unlock(&dir->i_mutex);
        return 0;
out_bad:
        __rpc_depopulate(parent, files, start, eof);
        mutex_unlock(&dir->i_mutex);
        printk(KERN_WARNING "%s: %s failed to populate directory %s\n",
                        __FILE__, __func__, parent->d_name.name);
        return err;
}

static struct dentry *rpc_mkdir_populate(struct dentry *parent,
                struct qstr *name, umode_t mode, void *private,
                int (*populate)(struct dentry *, void *), void *args_populate)
{
        struct dentry *dentry;
        struct inode *dir = parent->d_inode;
        int error;

        mutex_lock_nested(&dir->i_mutex, I_MUTEX_PARENT);
        dentry = __rpc_lookup_create_exclusive(parent, name);
        if (IS_ERR(dentry))
                goto out;
        error = __rpc_mkdir(dir, dentry, mode, NULL, private);
        if (error != 0)
                goto out_err;
        if (populate != NULL) {
                error = populate(dentry, args_populate);
                if (error)
                        goto err_rmdir;
        }
out:
        mutex_unlock(&dir->i_mutex);
        return dentry;
err_rmdir:
        __rpc_rmdir(dir, dentry);
out_err:
        dentry = ERR_PTR(error);
        goto out;
}

static int rpc_rmdir_depopulate(struct dentry *dentry,
                void (*depopulate)(struct dentry *))
{
        struct dentry *parent;
        struct inode *dir;
        int error;

        parent = dget_parent(dentry);
        dir = parent->d_inode;
        mutex_lock_nested(&dir->i_mutex, I_MUTEX_PARENT);
        if (depopulate != NULL)
                depopulate(dentry);
        error = __rpc_rmdir(dir, dentry);
        mutex_unlock(&dir->i_mutex);
        dput(parent);
        return error;
}

/**
 * rpc_mkpipe - make an rpc_pipefs file for kernel<->userspace communication
 * @parent: dentry of directory to create new "pipe" in
 * @name: name of pipe
 * @private: private data to associate with the pipe, for the caller's use
 * @pipe: &rpc_pipe containing input parameters
 *
 * Data is made available for userspace to read by calls to
 * rpc_queue_upcall().  The actual reads will result in calls to
 * @ops->upcall, which will be called with the file pointer,
 * message, and userspace buffer to copy to.
 *
 * Writes can come at any time, and do not necessarily have to be
 * responses to upcalls.  They will result in calls to @msg->downcall.
 *
 * The @private argument passed here will be available to all these methods
 * from the file pointer, via RPC_I(file_inode(file))->private.
 */
struct dentry *rpc_mkpipe_dentry(struct dentry *parent, const char *name,
                                 void *private, struct rpc_pipe *pipe)
{
        struct dentry *dentry;
        struct inode *dir = parent->d_inode;
        umode_t umode = S_IFIFO | S_IRUSR | S_IWUSR;
        struct qstr q;
        int err;

        if (pipe->ops->upcall == NULL)
                umode &= ~S_IRUGO;
        if (pipe->ops->downcall == NULL)
                umode &= ~S_IWUGO;

        q.name = name;
        q.len = strlen(name);
        q.hash = full_name_hash(q.name, q.len),

        mutex_lock_nested(&dir->i_mutex, I_MUTEX_PARENT);
        dentry = __rpc_lookup_create_exclusive(parent, &q);
        if (IS_ERR(dentry))
                goto out;
        err = __rpc_mkpipe_dentry(dir, dentry, umode, &rpc_pipe_fops,
                                  private, pipe);
        if (err)
                goto out_err;
out:
        mutex_unlock(&dir->i_mutex);
        return dentry;
out_err:
        dentry = ERR_PTR(err);
        printk(KERN_WARNING "%s: %s() failed to create pipe %s/%s (errno = %d)\n",
                        __FILE__, __func__, parent->d_name.name, name,
                        err);
        goto out;
}
EXPORT_SYMBOL_GPL(rpc_mkpipe_dentry);

/**
 * rpc_unlink - remove a pipe
 * @dentry: dentry for the pipe, as returned from rpc_mkpipe
 *
 * After this call, lookups will no longer find the pipe, and any
 * attempts to read or write using preexisting opens of the pipe will
 * return -EPIPE.
 */
int
rpc_unlink(struct dentry *dentry)
{
        struct dentry *parent;
        struct inode *dir;
        int error = 0;

        parent = dget_parent(dentry);
        dir = parent->d_inode;
        mutex_lock_nested(&dir->i_mutex, I_MUTEX_PARENT);
        error = __rpc_rmpipe(dir, dentry);
        mutex_unlock(&dir->i_mutex);
        dput(parent);
        return error;
}
EXPORT_SYMBOL_GPL(rpc_unlink);

enum {
        RPCAUTH_info,
        RPCAUTH_EOF
};

static const struct rpc_filelist authfiles[] = {
        [RPCAUTH_info] = {
                .name = "info",
                .i_fop = &rpc_info_operations,
                .mode = S_IFREG | S_IRUSR,
        },
};

static int rpc_clntdir_populate(struct dentry *dentry, void *private)
{
        return rpc_populate(dentry,
                            authfiles, RPCAUTH_info, RPCAUTH_EOF,
                            private);
}

static void rpc_clntdir_depopulate(struct dentry *dentry)
{
        rpc_depopulate(dentry, authfiles, RPCAUTH_info, RPCAUTH_EOF);
}

/**
 * rpc_create_client_dir - Create a new rpc_client directory in rpc_pipefs
 * @dentry: dentry from the rpc_pipefs root to the new directory
 * @name: &struct qstr for the name
 * @rpc_client: rpc client to associate with this directory
 *
 * This creates a directory at the given @path associated with
 * @rpc_clnt, which will contain a file named "info" with some basic
 * information about the client, together with any "pipes" that may
 * later be created using rpc_mkpipe().
 */
struct dentry *rpc_create_client_dir(struct dentry *dentry,
                                   struct qstr *name,
                                   struct rpc_clnt *rpc_client)
{
        return rpc_mkdir_populate(dentry, name, S_IRUGO | S_IXUGO, NULL,
                        rpc_clntdir_populate, rpc_client);
}

/**
 * rpc_remove_client_dir - Remove a directory created with rpc_create_client_dir()
 * @dentry: dentry for the pipe
 */
int rpc_remove_client_dir(struct dentry *dentry)
{
        return rpc_rmdir_depopulate(dentry, rpc_clntdir_depopulate);
}

static const struct rpc_filelist cache_pipefs_files[3] = {
        [0] = {
                .name = "channel",
                .i_fop = &cache_file_operations_pipefs,
                .mode = S_IFREG|S_IRUSR|S_IWUSR,
        },
        [1] = {
                .name = "content",
                .i_fop = &content_file_operations_pipefs,
                .mode = S_IFREG|S_IRUSR,
        },
        [2] = {
                .name = "flush",
                .i_fop = &cache_flush_operations_pipefs,
                .mode = S_IFREG|S_IRUSR|S_IWUSR,
        },
};

static int rpc_cachedir_populate(struct dentry *dentry, void *private)
{
        return rpc_populate(dentry,
                            cache_pipefs_files, 0, 3,
                            private);
}

static void rpc_cachedir_depopulate(struct dentry *dentry)
{
        rpc_depopulate(dentry, cache_pipefs_files, 0, 3);
}

struct dentry *rpc_create_cache_dir(struct dentry *parent, struct qstr *name,
                                    umode_t umode, struct cache_detail *cd)
{
        return rpc_mkdir_populate(parent, name, umode, NULL,
                        rpc_cachedir_populate, cd);
}

void rpc_remove_cache_dir(struct dentry *dentry)
{
        rpc_rmdir_depopulate(dentry, rpc_cachedir_depopulate);
}

/*
 * populate the filesystem
 */
static const struct super_operations s_ops = {
        .alloc_inode    = rpc_alloc_inode,
        .destroy_inode  = rpc_destroy_inode,
        .statfs         = simple_statfs,
};

#define RPCAUTH_GSSMAGIC 0x67596969

/*
 * We have a single directory with 1 node in it.
 */
enum {
        RPCAUTH_lockd,
        RPCAUTH_mount,
        RPCAUTH_nfs,
        RPCAUTH_portmap,
        RPCAUTH_statd,
        RPCAUTH_nfsd4_cb,
        RPCAUTH_cache,
        RPCAUTH_nfsd,
        RPCAUTH_RootEOF
};

static const struct rpc_filelist files[] = {
        [RPCAUTH_lockd] = {
                .name = "lockd",
                .mode = S_IFDIR | S_IRUGO | S_IXUGO,
        },
        [RPCAUTH_mount] = {
                .name = "mount",
                .mode = S_IFDIR | S_IRUGO | S_IXUGO,
        },
        [RPCAUTH_nfs] = {
                .name = "nfs",
                .mode = S_IFDIR | S_IRUGO | S_IXUGO,
        },
        [RPCAUTH_portmap] = {
                .name = "portmap",
                .mode = S_IFDIR | S_IRUGO | S_IXUGO,
        },
        [RPCAUTH_statd] = {
                .name = "statd",
                .mode = S_IFDIR | S_IRUGO | S_IXUGO,
        },
        [RPCAUTH_nfsd4_cb] = {
                .name = "nfsd4_cb",
                .mode = S_IFDIR | S_IRUGO | S_IXUGO,
        },
        [RPCAUTH_cache] = {
                .name = "cache",
                .mode = S_IFDIR | S_IRUGO | S_IXUGO,
        },
        [RPCAUTH_nfsd] = {
                .name = "nfsd",
                .mode = S_IFDIR | S_IRUGO | S_IXUGO,
        },
};

/*
 * This call can be used only in RPC pipefs mount notification hooks.
 */
struct dentry *rpc_d_lookup_sb(const struct super_block *sb,
                               const unsigned char *dir_name)
{
        struct qstr dir = QSTR_INIT(dir_name, strlen(dir_name));

        dir.hash = full_name_hash(dir.name, dir.len);
        return d_lookup(sb->s_root, &dir);
}
EXPORT_SYMBOL_GPL(rpc_d_lookup_sb);

void rpc_pipefs_init_net(struct net *net)
{
        struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);

        mutex_init(&sn->pipefs_sb_lock);
}

/*
 * This call will be used for per network namespace operations calls.
 * Note: Function will be returned with pipefs_sb_lock taken if superblock was
 * found. This lock have to be released by rpc_put_sb_net() when all operations
 * will be completed.
 */
struct super_block *rpc_get_sb_net(const struct net *net)
{
        struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);

        mutex_lock(&sn->pipefs_sb_lock);
        if (sn->pipefs_sb)
                return sn->pipefs_sb;
        mutex_unlock(&sn->pipefs_sb_lock);
        return NULL;
}
EXPORT_SYMBOL_GPL(rpc_get_sb_net);

void rpc_put_sb_net(const struct net *net)
{
        struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);

        WARN_ON(sn->pipefs_sb == NULL);
        mutex_unlock(&sn->pipefs_sb_lock);
}
EXPORT_SYMBOL_GPL(rpc_put_sb_net);

static int
rpc_fill_super(struct super_block *sb, void *data, int silent)
{
        struct inode *inode;
        struct dentry *root;
        struct net *net = data;
        struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);
        int err;

        sb->s_blocksize = PAGE_CACHE_SIZE;
        sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
        sb->s_magic = RPCAUTH_GSSMAGIC;
        sb->s_op = &s_ops;
        sb->s_time_gran = 1;

        inode = rpc_get_inode(sb, S_IFDIR | S_IRUGO | S_IXUGO);
        sb->s_root = root = d_make_root(inode);
        if (!root)
                return -ENOMEM;
        if (rpc_populate(root, files, RPCAUTH_lockd, RPCAUTH_RootEOF, NULL))
                return -ENOMEM;
        dprintk("RPC:       sending pipefs MOUNT notification for net %p%s\n",
                net, NET_NAME(net));
        sn->pipefs_sb = sb;
        err = blocking_notifier_call_chain(&rpc_pipefs_notifier_list,
                                           RPC_PIPEFS_MOUNT,
                                           sb);
        if (err)
                goto err_depopulate;
        sb->s_fs_info = get_net(net);
        return 0;

err_depopulate:
        blocking_notifier_call_chain(&rpc_pipefs_notifier_list,
                                           RPC_PIPEFS_UMOUNT,
                                           sb);
        sn->pipefs_sb = NULL;
        __rpc_depopulate(root, files, RPCAUTH_lockd, RPCAUTH_RootEOF);
        return err;
}

static struct dentry *
rpc_mount(struct file_system_type *fs_type,
                int flags, const char *dev_name, void *data)
{
        return mount_ns(fs_type, flags, current->nsproxy->net_ns, rpc_fill_super);
}

static void rpc_kill_sb(struct super_block *sb)
{
        struct net *net = sb->s_fs_info;
        struct sunrpc_net *sn = net_generic(net, sunrpc_net_id);

        mutex_lock(&sn->pipefs_sb_lock);
        if (sn->pipefs_sb != sb) {
                mutex_unlock(&sn->pipefs_sb_lock);
                goto out;
        }
        sn->pipefs_sb = NULL;
        mutex_unlock(&sn->pipefs_sb_lock);
        dprintk("RPC:       sending pipefs UMOUNT notification for net %p%s\n",
                net, NET_NAME(net));
        blocking_notifier_call_chain(&rpc_pipefs_notifier_list,
                                           RPC_PIPEFS_UMOUNT,
                                           sb);
        put_net(net);
out:
        kill_litter_super(sb);
}

static struct file_system_type rpc_pipe_fs_type = {
        .owner          = THIS_MODULE,
        .name           = "rpc_pipefs",
        .mount          = rpc_mount,
        .kill_sb        = rpc_kill_sb,
};
MODULE_ALIAS_FS("rpc_pipefs");
MODULE_ALIAS("rpc_pipefs");

static void
init_once(void *foo)
{
        struct rpc_inode *rpci = (struct rpc_inode *) foo;

        inode_init_once(&rpci->vfs_inode);
        rpci->private = NULL;
        rpci->pipe = NULL;
        init_waitqueue_head(&rpci->waitq);
}

int register_rpc_pipefs(void)
{
        int err;

        rpc_inode_cachep = kmem_cache_create("rpc_inode_cache",
                                sizeof(struct rpc_inode),
                                0, (SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT|
                                                SLAB_MEM_SPREAD),
                                init_once);
        if (!rpc_inode_cachep)
                return -ENOMEM;
        err = rpc_clients_notifier_register();
        if (err)
                goto err_notifier;
        err = register_filesystem(&rpc_pipe_fs_type);
        if (err)
                goto err_register;
        return 0;

err_register:
        rpc_clients_notifier_unregister();
err_notifier:
        kmem_cache_destroy(rpc_inode_cachep);
        return err;
}

void unregister_rpc_pipefs(void)
{
        rpc_clients_notifier_unregister();
        kmem_cache_destroy(rpc_inode_cachep);
        unregister_filesystem(&rpc_pipe_fs_type);
}