/*
*  Copyright (c) 2004 The Regents of the University of Michigan.
*  Copyright (c) 2012 Jeff Layton <jlayton@redhat.com>
*  All rights reserved.
*
*  Andy Adamson <andros@citi.umich.edu>
*
*  Redistribution and use in source and binary forms, with or without
*  modification, are permitted provided that the following conditions
*  are met:
*
*  1. Redistributions of source code must retain the above copyright
*     notice, this list of conditions and the following disclaimer.
*  2. Redistributions in binary form must reproduce the above copyright
*     notice, this list of conditions and the following disclaimer in the
*     documentation and/or other materials provided with the distribution.
*  3. Neither the name of the University nor the names of its
*     contributors may be used to endorse or promote products derived
*     from this software without specific prior written permission.
*
*  THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
*  WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
*  MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
*  DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
*  FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
*  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
*  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
*  BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
*  LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
*  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
*  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/

#include <linux/file.h>
#include <linux/slab.h>
#include <linux/namei.h>
#include <linux/crypto.h>
#include <linux/sched.h>
#include <linux/fs.h>
#include <linux/module.h>
#include <net/net_namespace.h>
#include <linux/sunrpc/rpc_pipe_fs.h>
#include <linux/sunrpc/clnt.h>
#include <linux/nfsd/cld.h>

#include "nfsd.h"
#include "state.h"
#include "vfs.h"
#include "netns.h"

#define NFSDDBG_FACILITY                NFSDDBG_PROC

/* Declarations */
struct nfsd4_client_tracking_ops {
        int (*init)(struct net *);
        void (*exit)(struct net *);
        void (*create)(struct nfs4_client *);
        void (*remove)(struct nfs4_client *);
        int (*check)(struct nfs4_client *);
        void (*grace_done)(struct net *, time_t);
};

/* Globals */
static struct file *rec_file;
static char user_recovery_dirname[PATH_MAX] = "/var/lib/nfs/v4recovery";
static struct nfsd4_client_tracking_ops *client_tracking_ops;

static int
nfs4_save_creds(const struct cred **original_creds)
{
        struct cred *new;

        new = prepare_creds();
        if (!new)
                return -ENOMEM;

        new->fsuid = 0;
        new->fsgid = 0;
        *original_creds = override_creds(new);
        put_cred(new);
        return 0;
}

static void
nfs4_reset_creds(const struct cred *original)
{
        revert_creds(original);
}

static void
md5_to_hex(char *out, char *md5)
{
        int i;

        for (i=0; i<16; i++) {
                unsigned char c = md5[i];

                *out++ = '0' + ((c&0xf0)>>4) + (c>=0xa0)*('a'-'9'-1);
                *out++ = '0' + (c&0x0f) + ((c&0x0f)>=0x0a)*('a'-'9'-1);
        }
        *out = '\0';
}

__be32
nfs4_make_rec_clidname(char *dname, struct xdr_netobj *clname)
{
        struct xdr_netobj cksum;
        struct hash_desc desc;
        struct scatterlist sg;
        __be32 status = nfserr_jukebox;

        dprintk("NFSD: nfs4_make_rec_clidname for %.*s\n",
                        clname->len, clname->data);
        desc.flags = CRYPTO_TFM_REQ_MAY_SLEEP;
        desc.tfm = crypto_alloc_hash("md5", 0, CRYPTO_ALG_ASYNC);
        if (IS_ERR(desc.tfm))
                goto out_no_tfm;
        cksum.len = crypto_hash_digestsize(desc.tfm);
        cksum.data = kmalloc(cksum.len, GFP_KERNEL);
        if (cksum.data == NULL)
                goto out;

        sg_init_one(&sg, clname->data, clname->len);

        if (crypto_hash_digest(&desc, &sg, sg.length, cksum.data))
                goto out;

        md5_to_hex(dname, cksum.data);

        status = nfs_ok;
out:
        kfree(cksum.data);
        crypto_free_hash(desc.tfm);
out_no_tfm:
        return status;
}

static void
nfsd4_create_clid_dir(struct nfs4_client *clp)
{
        const struct cred *original_cred;
        char *dname = clp->cl_recdir;
        struct dentry *dir, *dentry;
        int status;

        dprintk("NFSD: nfsd4_create_clid_dir for \"%s\"\n", dname);

        if (test_and_set_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags))
                return;
        if (!rec_file)
                return;
        status = nfs4_save_creds(&original_cred);
        if (status < 0)
                return;

        status = mnt_want_write_file(rec_file);
        if (status)
                return;

        dir = rec_file->f_path.dentry;
        /* lock the parent */
        mutex_lock(&dir->d_inode->i_mutex);

        dentry = lookup_one_len(dname, dir, HEXDIR_LEN-1);
        if (IS_ERR(dentry)) {
                status = PTR_ERR(dentry);
                goto out_unlock;
        }
        if (dentry->d_inode)
                /*
                 * In the 4.1 case, where we're called from
                 * reclaim_complete(), records from the previous reboot
                 * may still be left, so this is OK.
                 *
                 * In the 4.0 case, we should never get here; but we may
                 * as well be forgiving and just succeed silently.
                 */
                goto out_put;
        status = vfs_mkdir(dir->d_inode, dentry, S_IRWXU);
out_put:
        dput(dentry);
out_unlock:
        mutex_unlock(&dir->d_inode->i_mutex);
        if (status == 0)
                vfs_fsync(rec_file, 0);
        else
                printk(KERN_ERR "NFSD: failed to write recovery record"
                                " (err %d); please check that %s exists"
                                " and is writeable", status,
                                user_recovery_dirname);
        mnt_drop_write_file(rec_file);
        nfs4_reset_creds(original_cred);
}

typedef int (recdir_func)(struct dentry *, struct dentry *);

struct name_list {
        char name[HEXDIR_LEN];
        struct list_head list;
};

static int
nfsd4_build_namelist(void *arg, const char *name, int namlen,
                loff_t offset, u64 ino, unsigned int d_type)
{
        struct list_head *names = arg;
        struct name_list *entry;

        if (namlen != HEXDIR_LEN - 1)
                return 0;
        entry = kmalloc(sizeof(struct name_list), GFP_KERNEL);
        if (entry == NULL)
                return -ENOMEM;
        memcpy(entry->name, name, HEXDIR_LEN - 1);
        entry->name[HEXDIR_LEN - 1] = '\0';
        list_add(&entry->list, names);
        return 0;
}

static int
nfsd4_list_rec_dir(recdir_func *f)
{
        const struct cred *original_cred;
        struct dentry *dir = rec_file->f_path.dentry;
        LIST_HEAD(names);
        int status;

        status = nfs4_save_creds(&original_cred);
        if (status < 0)
                return status;

        status = vfs_llseek(rec_file, 0, SEEK_SET);
        if (status < 0) {
                nfs4_reset_creds(original_cred);
                return status;
        }

        status = vfs_readdir(rec_file, nfsd4_build_namelist, &names);
        mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_PARENT);
        while (!list_empty(&names)) {
                struct name_list *entry;
                entry = list_entry(names.next, struct name_list, list);
                if (!status) {
                        struct dentry *dentry;
                        dentry = lookup_one_len(entry->name, dir, HEXDIR_LEN-1);
                        if (IS_ERR(dentry)) {
                                status = PTR_ERR(dentry);
                                break;
                        }
                        status = f(dir, dentry);
                        dput(dentry);
                }
                list_del(&entry->list);
                kfree(entry);
        }
        mutex_unlock(&dir->d_inode->i_mutex);
        nfs4_reset_creds(original_cred);
        return status;
}

static int
nfsd4_unlink_clid_dir(char *name, int namlen)
{
        struct dentry *dir, *dentry;
        int status;

        dprintk("NFSD: nfsd4_unlink_clid_dir. name %.*s\n", namlen, name);

        dir = rec_file->f_path.dentry;
        mutex_lock_nested(&dir->d_inode->i_mutex, I_MUTEX_PARENT);
        dentry = lookup_one_len(name, dir, namlen);
        if (IS_ERR(dentry)) {
                status = PTR_ERR(dentry);
                goto out_unlock;
        }
        status = -ENOENT;
        if (!dentry->d_inode)
                goto out;
        status = vfs_rmdir(dir->d_inode, dentry);
out:
        dput(dentry);
out_unlock:
        mutex_unlock(&dir->d_inode->i_mutex);
        return status;
}

static void
nfsd4_remove_clid_dir(struct nfs4_client *clp)
{
        const struct cred *original_cred;
        int status;

        if (!rec_file || !test_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags))
                return;

        status = mnt_want_write_file(rec_file);
        if (status)
                goto out;
        clear_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags);

        status = nfs4_save_creds(&original_cred);
        if (status < 0)
                goto out;

        status = nfsd4_unlink_clid_dir(clp->cl_recdir, HEXDIR_LEN-1);
        nfs4_reset_creds(original_cred);
        if (status == 0)
                vfs_fsync(rec_file, 0);
        mnt_drop_write_file(rec_file);
out:
        if (status)
                printk("NFSD: Failed to remove expired client state directory"
                                " %.*s\n", HEXDIR_LEN, clp->cl_recdir);
}

static int
purge_old(struct dentry *parent, struct dentry *child)
{
        int status;

        if (nfs4_has_reclaimed_state(child->d_name.name, false))
                return 0;

        status = vfs_rmdir(parent->d_inode, child);
        if (status)
                printk("failed to remove client recovery directory %s\n",
                                child->d_name.name);
        /* Keep trying, success or failure: */
        return 0;
}

static void
nfsd4_recdir_purge_old(struct net *net, time_t boot_time)
{
        int status;

        if (!rec_file)
                return;
        status = mnt_want_write_file(rec_file);
        if (status)
                goto out;
        status = nfsd4_list_rec_dir(purge_old);
        if (status == 0)
                vfs_fsync(rec_file, 0);
        mnt_drop_write_file(rec_file);
out:
        if (status)
                printk("nfsd4: failed to purge old clients from recovery"
                        " directory %s\n", rec_file->f_path.dentry->d_name.name);
}

static int
load_recdir(struct dentry *parent, struct dentry *child)
{
        if (child->d_name.len != HEXDIR_LEN - 1) {
                printk("nfsd4: illegal name %s in recovery directory\n",
                                child->d_name.name);
                /* Keep trying; maybe the others are OK: */
                return 0;
        }
        nfs4_client_to_reclaim(child->d_name.name);
        return 0;
}

static int
nfsd4_recdir_load(void) {
        int status;

        if (!rec_file)
                return 0;

        status = nfsd4_list_rec_dir(load_recdir);
        if (status)
                printk("nfsd4: failed loading clients from recovery"
                        " directory %s\n", rec_file->f_path.dentry->d_name.name);
        return status;
}

/*
 * Hold reference to the recovery directory.
 */

static int
nfsd4_init_recdir(void)
{
        const struct cred *original_cred;
        int status;

        printk("NFSD: Using %s as the NFSv4 state recovery directory\n",
                        user_recovery_dirname);

        BUG_ON(rec_file);

        status = nfs4_save_creds(&original_cred);
        if (status < 0) {
                printk("NFSD: Unable to change credentials to find recovery"
                       " directory: error %d\n",
                       status);
                return status;
        }

        rec_file = filp_open(user_recovery_dirname, O_RDONLY | O_DIRECTORY, 0);
        if (IS_ERR(rec_file)) {
                printk("NFSD: unable to find recovery directory %s\n",
                                user_recovery_dirname);
                status = PTR_ERR(rec_file);
                rec_file = NULL;
        }

        nfs4_reset_creds(original_cred);
        return status;
}

static int
nfsd4_load_reboot_recovery_data(struct net *net)
{
        int status;

        /* XXX: The legacy code won't work in a container */
        if (net != &init_net) {
                WARN(1, KERN_ERR "NFSD: attempt to initialize legacy client "
                        "tracking in a container!\n");
                return -EINVAL;
        }

        nfs4_lock_state();
        status = nfsd4_init_recdir();
        if (!status)
                status = nfsd4_recdir_load();
        nfs4_unlock_state();
        if (status)
                printk(KERN_ERR "NFSD: Failure reading reboot recovery data\n");
        return status;
}

static void
nfsd4_shutdown_recdir(void)
{
        if (!rec_file)
                return;
        fput(rec_file);
        rec_file = NULL;
}

static void
nfsd4_legacy_tracking_exit(struct net *net)
{
        nfs4_release_reclaim();
        nfsd4_shutdown_recdir();
}

/*
 * Change the NFSv4 recovery directory to recdir.
 */
int
nfs4_reset_recoverydir(char *recdir)
{
        int status;
        struct path path;

        status = kern_path(recdir, LOOKUP_FOLLOW, &path);
        if (status)
                return status;
        status = -ENOTDIR;
        if (S_ISDIR(path.dentry->d_inode->i_mode)) {
                strcpy(user_recovery_dirname, recdir);
                status = 0;
        }
        path_put(&path);
        return status;
}

char *
nfs4_recoverydir(void)
{
        return user_recovery_dirname;
}

static int
nfsd4_check_legacy_client(struct nfs4_client *clp)
{
        /* did we already find that this client is stable? */
        if (test_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags))
                return 0;

        /* look for it in the reclaim hashtable otherwise */
        if (nfsd4_find_reclaim_client(clp)) {
                set_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags);
                return 0;
        }

        return -ENOENT;
}

static struct nfsd4_client_tracking_ops nfsd4_legacy_tracking_ops = {
        .init           = nfsd4_load_reboot_recovery_data,
        .exit           = nfsd4_legacy_tracking_exit,
        .create         = nfsd4_create_clid_dir,
        .remove         = nfsd4_remove_clid_dir,
        .check          = nfsd4_check_legacy_client,
        .grace_done     = nfsd4_recdir_purge_old,
};

/* Globals */
#define NFSD_PIPE_DIR           "nfsd"
#define NFSD_CLD_PIPE           "cld"

/* per-net-ns structure for holding cld upcall info */
struct cld_net {
        struct rpc_pipe         *cn_pipe;
        spinlock_t               cn_lock;
        struct list_head         cn_list;
        unsigned int             cn_xid;
};

struct cld_upcall {
        struct list_head         cu_list;
        struct cld_net          *cu_net;
        struct task_struct      *cu_task;
        struct cld_msg           cu_msg;
};

static int
__cld_pipe_upcall(struct rpc_pipe *pipe, struct cld_msg *cmsg)
{
        int ret;
        struct rpc_pipe_msg msg;

        memset(&msg, 0, sizeof(msg));
        msg.data = cmsg;
        msg.len = sizeof(*cmsg);

        /*
         * Set task state before we queue the upcall. That prevents
         * wake_up_process in the downcall from racing with schedule.
         */
        set_current_state(TASK_UNINTERRUPTIBLE);
        ret = rpc_queue_upcall(pipe, &msg);
        if (ret < 0) {
                set_current_state(TASK_RUNNING);
                goto out;
        }

        schedule();
        set_current_state(TASK_RUNNING);

        if (msg.errno < 0)
                ret = msg.errno;
out:
        return ret;
}

static int
cld_pipe_upcall(struct rpc_pipe *pipe, struct cld_msg *cmsg)
{
        int ret;

        /*
         * -EAGAIN occurs when pipe is closed and reopened while there are
         *  upcalls queued.
         */
        do {
                ret = __cld_pipe_upcall(pipe, cmsg);
        } while (ret == -EAGAIN);

        return ret;
}

static ssize_t
cld_pipe_downcall(struct file *filp, const char __user *src, size_t mlen)
{
        struct cld_upcall *tmp, *cup;
        struct cld_msg __user *cmsg = (struct cld_msg __user *)src;
        uint32_t xid;
        struct nfsd_net *nn = net_generic(filp->f_dentry->d_sb->s_fs_info,
                                                nfsd_net_id);
        struct cld_net *cn = nn->cld_net;

        if (mlen != sizeof(*cmsg)) {
                dprintk("%s: got %zu bytes, expected %zu\n", __func__, mlen,
                        sizeof(*cmsg));
                return -EINVAL;
        }

        /* copy just the xid so we can try to find that */
        if (copy_from_user(&xid, &cmsg->cm_xid, sizeof(xid)) != 0) {
                dprintk("%s: error when copying xid from userspace", __func__);
                return -EFAULT;
        }

        /* walk the list and find corresponding xid */
        cup = NULL;
        spin_lock(&cn->cn_lock);
        list_for_each_entry(tmp, &cn->cn_list, cu_list) {
                if (get_unaligned(&tmp->cu_msg.cm_xid) == xid) {
                        cup = tmp;
                        list_del_init(&cup->cu_list);
                        break;
                }
        }
        spin_unlock(&cn->cn_lock);

        /* couldn't find upcall? */
        if (!cup) {
                dprintk("%s: couldn't find upcall -- xid=%u\n", __func__, xid);
                return -EINVAL;
        }

        if (copy_from_user(&cup->cu_msg, src, mlen) != 0)
                return -EFAULT;

        wake_up_process(cup->cu_task);
        return mlen;
}

static void
cld_pipe_destroy_msg(struct rpc_pipe_msg *msg)
{
        struct cld_msg *cmsg = msg->data;
        struct cld_upcall *cup = container_of(cmsg, struct cld_upcall,
                                                 cu_msg);

        /* errno >= 0 means we got a downcall */
        if (msg->errno >= 0)
                return;

        wake_up_process(cup->cu_task);
}

static const struct rpc_pipe_ops cld_upcall_ops = {
        .upcall         = rpc_pipe_generic_upcall,
        .downcall       = cld_pipe_downcall,
        .destroy_msg    = cld_pipe_destroy_msg,
};

static struct dentry *
nfsd4_cld_register_sb(struct super_block *sb, struct rpc_pipe *pipe)
{
        struct dentry *dir, *dentry;

        dir = rpc_d_lookup_sb(sb, NFSD_PIPE_DIR);
        if (dir == NULL)
                return ERR_PTR(-ENOENT);
        dentry = rpc_mkpipe_dentry(dir, NFSD_CLD_PIPE, NULL, pipe);
        dput(dir);
        return dentry;
}

static void
nfsd4_cld_unregister_sb(struct rpc_pipe *pipe)
{
        if (pipe->dentry)
                rpc_unlink(pipe->dentry);
}

static struct dentry *
nfsd4_cld_register_net(struct net *net, struct rpc_pipe *pipe)
{
        struct super_block *sb;
        struct dentry *dentry;

        sb = rpc_get_sb_net(net);
        if (!sb)
                return NULL;
        dentry = nfsd4_cld_register_sb(sb, pipe);
        rpc_put_sb_net(net);
        return dentry;
}

static void
nfsd4_cld_unregister_net(struct net *net, struct rpc_pipe *pipe)
{
        struct super_block *sb;

        sb = rpc_get_sb_net(net);
        if (sb) {
                nfsd4_cld_unregister_sb(pipe);
                rpc_put_sb_net(net);
        }
}

/* Initialize rpc_pipefs pipe for communication with client tracking daemon */
static int
nfsd4_init_cld_pipe(struct net *net)
{
        int ret;
        struct dentry *dentry;
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);
        struct cld_net *cn;

        if (nn->cld_net)
                return 0;

        cn = kzalloc(sizeof(*cn), GFP_KERNEL);
        if (!cn) {
                ret = -ENOMEM;
                goto err;
        }

        cn->cn_pipe = rpc_mkpipe_data(&cld_upcall_ops, RPC_PIPE_WAIT_FOR_OPEN);
        if (IS_ERR(cn->cn_pipe)) {
                ret = PTR_ERR(cn->cn_pipe);
                goto err;
        }
        spin_lock_init(&cn->cn_lock);
        INIT_LIST_HEAD(&cn->cn_list);

        dentry = nfsd4_cld_register_net(net, cn->cn_pipe);
        if (IS_ERR(dentry)) {
                ret = PTR_ERR(dentry);
                goto err_destroy_data;
        }

        cn->cn_pipe->dentry = dentry;
        nn->cld_net = cn;
        return 0;

err_destroy_data:
        rpc_destroy_pipe_data(cn->cn_pipe);
err:
        kfree(cn);
        printk(KERN_ERR "NFSD: unable to create nfsdcld upcall pipe (%d)\n",
                        ret);
        return ret;
}

static void
nfsd4_remove_cld_pipe(struct net *net)
{
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);
        struct cld_net *cn = nn->cld_net;

        nfsd4_cld_unregister_net(net, cn->cn_pipe);
        rpc_destroy_pipe_data(cn->cn_pipe);
        kfree(nn->cld_net);
        nn->cld_net = NULL;
}

static struct cld_upcall *
alloc_cld_upcall(struct cld_net *cn)
{
        struct cld_upcall *new, *tmp;

        new = kzalloc(sizeof(*new), GFP_KERNEL);
        if (!new)
                return new;

        /* FIXME: hard cap on number in flight? */
restart_search:
        spin_lock(&cn->cn_lock);
        list_for_each_entry(tmp, &cn->cn_list, cu_list) {
                if (tmp->cu_msg.cm_xid == cn->cn_xid) {
                        cn->cn_xid++;
                        spin_unlock(&cn->cn_lock);
                        goto restart_search;
                }
        }
        new->cu_task = current;
        new->cu_msg.cm_vers = CLD_UPCALL_VERSION;
        put_unaligned(cn->cn_xid++, &new->cu_msg.cm_xid);
        new->cu_net = cn;
        list_add(&new->cu_list, &cn->cn_list);
        spin_unlock(&cn->cn_lock);

        dprintk("%s: allocated xid %u\n", __func__, new->cu_msg.cm_xid);

        return new;
}

static void
free_cld_upcall(struct cld_upcall *victim)
{
        struct cld_net *cn = victim->cu_net;

        spin_lock(&cn->cn_lock);
        list_del(&victim->cu_list);
        spin_unlock(&cn->cn_lock);
        kfree(victim);
}

/* Ask daemon to create a new record */
static void
nfsd4_cld_create(struct nfs4_client *clp)
{
        int ret;
        struct cld_upcall *cup;
        /* FIXME: determine net from clp */
        struct nfsd_net *nn = net_generic(&init_net, nfsd_net_id);
        struct cld_net *cn = nn->cld_net;

        /* Don't upcall if it's already stored */
        if (test_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags))
                return;

        cup = alloc_cld_upcall(cn);
        if (!cup) {
                ret = -ENOMEM;
                goto out_err;
        }

        cup->cu_msg.cm_cmd = Cld_Create;
        cup->cu_msg.cm_u.cm_name.cn_len = clp->cl_name.len;
        memcpy(cup->cu_msg.cm_u.cm_name.cn_id, clp->cl_name.data,
                        clp->cl_name.len);

        ret = cld_pipe_upcall(cn->cn_pipe, &cup->cu_msg);
        if (!ret) {
                ret = cup->cu_msg.cm_status;
                set_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags);
        }

        free_cld_upcall(cup);
out_err:
        if (ret)
                printk(KERN_ERR "NFSD: Unable to create client "
                                "record on stable storage: %d\n", ret);
}

/* Ask daemon to create a new record */
static void
nfsd4_cld_remove(struct nfs4_client *clp)
{
        int ret;
        struct cld_upcall *cup;
        /* FIXME: determine net from clp */
        struct nfsd_net *nn = net_generic(&init_net, nfsd_net_id);
        struct cld_net *cn = nn->cld_net;

        /* Don't upcall if it's already removed */
        if (!test_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags))
                return;

        cup = alloc_cld_upcall(cn);
        if (!cup) {
                ret = -ENOMEM;
                goto out_err;
        }

        cup->cu_msg.cm_cmd = Cld_Remove;
        cup->cu_msg.cm_u.cm_name.cn_len = clp->cl_name.len;
        memcpy(cup->cu_msg.cm_u.cm_name.cn_id, clp->cl_name.data,
                        clp->cl_name.len);

        ret = cld_pipe_upcall(cn->cn_pipe, &cup->cu_msg);
        if (!ret) {
                ret = cup->cu_msg.cm_status;
                clear_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags);
        }

        free_cld_upcall(cup);
out_err:
        if (ret)
                printk(KERN_ERR "NFSD: Unable to remove client "
                                "record from stable storage: %d\n", ret);
}

/* Check for presence of a record, and update its timestamp */
static int
nfsd4_cld_check(struct nfs4_client *clp)
{
        int ret;
        struct cld_upcall *cup;
        /* FIXME: determine net from clp */
        struct nfsd_net *nn = net_generic(&init_net, nfsd_net_id);
        struct cld_net *cn = nn->cld_net;

        /* Don't upcall if one was already stored during this grace pd */
        if (test_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags))
                return 0;

        cup = alloc_cld_upcall(cn);
        if (!cup) {
                printk(KERN_ERR "NFSD: Unable to check client record on "
                                "stable storage: %d\n", -ENOMEM);
                return -ENOMEM;
        }

        cup->cu_msg.cm_cmd = Cld_Check;
        cup->cu_msg.cm_u.cm_name.cn_len = clp->cl_name.len;
        memcpy(cup->cu_msg.cm_u.cm_name.cn_id, clp->cl_name.data,
                        clp->cl_name.len);

        ret = cld_pipe_upcall(cn->cn_pipe, &cup->cu_msg);
        if (!ret) {
                ret = cup->cu_msg.cm_status;
                set_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags);
        }

        free_cld_upcall(cup);
        return ret;
}

static void
nfsd4_cld_grace_done(struct net *net, time_t boot_time)
{
        int ret;
        struct cld_upcall *cup;
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);
        struct cld_net *cn = nn->cld_net;

        cup = alloc_cld_upcall(cn);
        if (!cup) {
                ret = -ENOMEM;
                goto out_err;
        }

        cup->cu_msg.cm_cmd = Cld_GraceDone;
        cup->cu_msg.cm_u.cm_gracetime = (int64_t)boot_time;
        ret = cld_pipe_upcall(cn->cn_pipe, &cup->cu_msg);
        if (!ret)
                ret = cup->cu_msg.cm_status;

        free_cld_upcall(cup);
out_err:
        if (ret)
                printk(KERN_ERR "NFSD: Unable to end grace period: %d\n", ret);
}

static struct nfsd4_client_tracking_ops nfsd4_cld_tracking_ops = {
        .init           = nfsd4_init_cld_pipe,
        .exit           = nfsd4_remove_cld_pipe,
        .create         = nfsd4_cld_create,
        .remove         = nfsd4_cld_remove,
        .check          = nfsd4_cld_check,
        .grace_done     = nfsd4_cld_grace_done,
};

int
nfsd4_client_tracking_init(struct net *net)
{
        int status;
        struct path path;

        if (!client_tracking_ops) {
                client_tracking_ops = &nfsd4_cld_tracking_ops;
                status = kern_path(nfs4_recoverydir(), LOOKUP_FOLLOW, &path);
                if (!status) {
                        if (S_ISDIR(path.dentry->d_inode->i_mode))
                                client_tracking_ops =
                                                &nfsd4_legacy_tracking_ops;
                        path_put(&path);
                }
        }

        status = client_tracking_ops->init(net);
        if (status) {
                printk(KERN_WARNING "NFSD: Unable to initialize client "
                                    "recovery tracking! (%d)\n", status);
                client_tracking_ops = NULL;
        }
        return status;
}

void
nfsd4_client_tracking_exit(struct net *net)
{
        if (client_tracking_ops) {
                client_tracking_ops->exit(net);
                client_tracking_ops = NULL;
        }
}

void
nfsd4_client_record_create(struct nfs4_client *clp)
{
        if (client_tracking_ops)
                client_tracking_ops->create(clp);
}

void
nfsd4_client_record_remove(struct nfs4_client *clp)
{
        if (client_tracking_ops)
                client_tracking_ops->remove(clp);
}

int
nfsd4_client_record_check(struct nfs4_client *clp)
{
        if (client_tracking_ops)
                return client_tracking_ops->check(clp);

        return -EOPNOTSUPP;
}

void
nfsd4_record_grace_done(struct net *net, time_t boot_time)
{
        if (client_tracking_ops)
                client_tracking_ops->grace_done(net, boot_time);
}

static int
rpc_pipefs_event(struct notifier_block *nb, unsigned long event, void *ptr)
{
        struct super_block *sb = ptr;
        struct net *net = sb->s_fs_info;
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);
        struct cld_net *cn = nn->cld_net;

        struct dentry *dentry;
        int ret = 0;

        if (!try_module_get(THIS_MODULE))
                return 0;

        if (!cn) {
                module_put(THIS_MODULE);
                return 0;
        }

        switch (event) {
        case RPC_PIPEFS_MOUNT:
                dentry = nfsd4_cld_register_sb(sb, cn->cn_pipe);
                if (IS_ERR(dentry)) {
                        ret = PTR_ERR(dentry);
                        break;
                }
                cn->cn_pipe->dentry = dentry;
                break;
        case RPC_PIPEFS_UMOUNT:
                if (cn->cn_pipe->dentry)
                        nfsd4_cld_unregister_sb(cn->cn_pipe);
                break;
        default:
                ret = -ENOTSUPP;
                break;
        }
        module_put(THIS_MODULE);
        return ret;
}

static struct notifier_block nfsd4_cld_block = {
        .notifier_call = rpc_pipefs_event,
};

int
register_cld_notifier(void)
{
        return rpc_pipefs_notifier_register(&nfsd4_cld_block);
}

void
unregister_cld_notifier(void)
{
        rpc_pipefs_notifier_unregister(&nfsd4_cld_block);
}