treewide: kmalloc() -> kmalloc_array()

[mirror_ubuntu-eoan-kernel.git] / fs / nfsd / nfs4recover.c

/*
*  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 <crypto/hash.h>
#include <linux/file.h>
#include <linux/slab.h>
#include <linux/namei.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 nfsd_net *);
};

/* Globals */
static char user_recovery_dirname[PATH_MAX] = "/var/lib/nfs/v4recovery";

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

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

        new->fsuid = GLOBAL_ROOT_UID;
        new->fsgid = GLOBAL_ROOT_GID;
        *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';
}

static int
nfs4_make_rec_clidname(char *dname, const struct xdr_netobj *clname)
{
        struct xdr_netobj cksum;
        struct crypto_shash *tfm;
        int status;

        dprintk("NFSD: nfs4_make_rec_clidname for %.*s\n",
                        clname->len, clname->data);
        tfm = crypto_alloc_shash("md5", 0, 0);
        if (IS_ERR(tfm)) {
                status = PTR_ERR(tfm);
                goto out_no_tfm;
        }

        cksum.len = crypto_shash_digestsize(tfm);
        cksum.data = kmalloc(cksum.len, GFP_KERNEL);
        if (cksum.data == NULL) {
                status = -ENOMEM;
                goto out;
        }

        {
                SHASH_DESC_ON_STACK(desc, tfm);

                desc->tfm = tfm;
                desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;

                status = crypto_shash_digest(desc, clname->data, clname->len,
                                             cksum.data);
                shash_desc_zero(desc);
        }

        if (status)
                goto out;

        md5_to_hex(dname, cksum.data);

        status = 0;
out:
        kfree(cksum.data);
        crypto_free_shash(tfm);
out_no_tfm:
        return status;
}

/*
 * If we had an error generating the recdir name for the legacy tracker
 * then warn the admin. If the error doesn't appear to be transient,
 * then disable recovery tracking.
 */
static void
legacy_recdir_name_error(struct nfs4_client *clp, int error)
{
        printk(KERN_ERR "NFSD: unable to generate recoverydir "
                        "name (%d).\n", error);

        /*
         * if the algorithm just doesn't exist, then disable the recovery
         * tracker altogether. The crypto libs will generally return this if
         * FIPS is enabled as well.
         */
        if (error == -ENOENT) {
                printk(KERN_ERR "NFSD: disabling legacy clientid tracking. "
                        "Reboot recovery will not function correctly!\n");
                nfsd4_client_tracking_exit(clp->net);
        }
}

static void
nfsd4_create_clid_dir(struct nfs4_client *clp)
{
        const struct cred *original_cred;
        char dname[HEXDIR_LEN];
        struct dentry *dir, *dentry;
        struct nfs4_client_reclaim *crp;
        int status;
        struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);

        if (test_and_set_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags))
                return;
        if (!nn->rec_file)
                return;

        status = nfs4_make_rec_clidname(dname, &clp->cl_name);
        if (status)
                return legacy_recdir_name_error(clp, status);

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

        status = mnt_want_write_file(nn->rec_file);
        if (status)
                goto out_creds;

        dir = nn->rec_file->f_path.dentry;
        /* lock the parent */
        inode_lock(d_inode(dir));

        dentry = lookup_one_len(dname, dir, HEXDIR_LEN-1);
        if (IS_ERR(dentry)) {
                status = PTR_ERR(dentry);
                goto out_unlock;
        }
        if (d_really_is_positive(dentry))
                /*
                 * 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(d_inode(dir), dentry, S_IRWXU);
out_put:
        dput(dentry);
out_unlock:
        inode_unlock(d_inode(dir));
        if (status == 0) {
                if (nn->in_grace) {
                        crp = nfs4_client_to_reclaim(dname, nn);
                        if (crp)
                                crp->cr_clp = clp;
                }
                vfs_fsync(nn->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(nn->rec_file);
out_creds:
        nfs4_reset_creds(original_cred);
}

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

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

struct nfs4_dir_ctx {
        struct dir_context ctx;
        struct list_head names;
};

static int
nfsd4_build_namelist(struct dir_context *__ctx, const char *name, int namlen,
                loff_t offset, u64 ino, unsigned int d_type)
{
        struct nfs4_dir_ctx *ctx =
                container_of(__ctx, struct nfs4_dir_ctx, ctx);
        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, &ctx->names);
        return 0;
}

static int
nfsd4_list_rec_dir(recdir_func *f, struct nfsd_net *nn)
{
        const struct cred *original_cred;
        struct dentry *dir = nn->rec_file->f_path.dentry;
        struct nfs4_dir_ctx ctx = {
                .ctx.actor = nfsd4_build_namelist,
                .names = LIST_HEAD_INIT(ctx.names)
        };
        struct name_list *entry, *tmp;
        int status;

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

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

        status = iterate_dir(nn->rec_file, &ctx.ctx);
        inode_lock_nested(d_inode(dir), I_MUTEX_PARENT);

        list_for_each_entry_safe(entry, tmp, &ctx.names, 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, nn);
                        dput(dentry);
                }
                list_del(&entry->list);
                kfree(entry);
        }
        inode_unlock(d_inode(dir));
        nfs4_reset_creds(original_cred);

        list_for_each_entry_safe(entry, tmp, &ctx.names, list) {
                dprintk("NFSD: %s. Left entry %s\n", __func__, entry->name);
                list_del(&entry->list);
                kfree(entry);
        }
        return status;
}

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

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

        dir = nn->rec_file->f_path.dentry;
        inode_lock_nested(d_inode(dir), I_MUTEX_PARENT);
        dentry = lookup_one_len(name, dir, namlen);
        if (IS_ERR(dentry)) {
                status = PTR_ERR(dentry);
                goto out_unlock;
        }
        status = -ENOENT;
        if (d_really_is_negative(dentry))
                goto out;
        status = vfs_rmdir(d_inode(dir), dentry);
out:
        dput(dentry);
out_unlock:
        inode_unlock(d_inode(dir));
        return status;
}

static void
nfsd4_remove_clid_dir(struct nfs4_client *clp)
{
        const struct cred *original_cred;
        struct nfs4_client_reclaim *crp;
        char dname[HEXDIR_LEN];
        int status;
        struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);

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

        status = nfs4_make_rec_clidname(dname, &clp->cl_name);
        if (status)
                return legacy_recdir_name_error(clp, status);

        status = mnt_want_write_file(nn->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_drop_write;

        status = nfsd4_unlink_clid_dir(dname, HEXDIR_LEN-1, nn);
        nfs4_reset_creds(original_cred);
        if (status == 0) {
                vfs_fsync(nn->rec_file, 0);
                if (nn->in_grace) {
                        /* remove reclaim record */
                        crp = nfsd4_find_reclaim_client(dname, nn);
                        if (crp)
                                nfs4_remove_reclaim_record(crp, nn);
                }
        }
out_drop_write:
        mnt_drop_write_file(nn->rec_file);
out:
        if (status)
                printk("NFSD: Failed to remove expired client state directory"
                                " %.*s\n", HEXDIR_LEN, dname);
}

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

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

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

static void
nfsd4_recdir_purge_old(struct nfsd_net *nn)
{
        int status;

        nn->in_grace = false;
        if (!nn->rec_file)
                return;
        status = mnt_want_write_file(nn->rec_file);
        if (status)
                goto out;
        status = nfsd4_list_rec_dir(purge_old, nn);
        if (status == 0)
                vfs_fsync(nn->rec_file, 0);
        mnt_drop_write_file(nn->rec_file);
out:
        nfs4_release_reclaim(nn);
        if (status)
                printk("nfsd4: failed to purge old clients from recovery"
                        " directory %pD\n", nn->rec_file);
}

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

static int
nfsd4_recdir_load(struct net *net) {
        int status;
        struct nfsd_net *nn =  net_generic(net, nfsd_net_id);

        if (!nn->rec_file)
                return 0;

        status = nfsd4_list_rec_dir(load_recdir, nn);
        if (status)
                printk("nfsd4: failed loading clients from recovery"
                        " directory %pD\n", nn->rec_file);
        return status;
}

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

static int
nfsd4_init_recdir(struct net *net)
{
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);
        const struct cred *original_cred;
        int status;

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

        BUG_ON(nn->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;
        }

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

        nfs4_reset_creds(original_cred);
        if (!status)
                nn->in_grace = true;
        return status;
}

static void
nfsd4_shutdown_recdir(struct net *net)
{
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);

        if (!nn->rec_file)
                return;
        fput(nn->rec_file);
        nn->rec_file = NULL;
}

static int
nfs4_legacy_state_init(struct net *net)
{
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);
        int i;

        nn->reclaim_str_hashtbl = kmalloc_array(CLIENT_HASH_SIZE,
                                                sizeof(struct list_head),
                                                GFP_KERNEL);
        if (!nn->reclaim_str_hashtbl)
                return -ENOMEM;

        for (i = 0; i < CLIENT_HASH_SIZE; i++)
                INIT_LIST_HEAD(&nn->reclaim_str_hashtbl[i]);
        nn->reclaim_str_hashtbl_size = 0;

        return 0;
}

static void
nfs4_legacy_state_shutdown(struct net *net)
{
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);

        kfree(nn->reclaim_str_hashtbl);
}

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

        status = nfsd4_init_recdir(net);
        if (status)
                return status;

        status = nfsd4_recdir_load(net);
        if (status)
                nfsd4_shutdown_recdir(net);

        return status;
}

static int
nfsd4_legacy_tracking_init(struct net *net)
{
        int status;

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

        status = nfs4_legacy_state_init(net);
        if (status)
                return status;

        status = nfsd4_load_reboot_recovery_data(net);
        if (status)
                goto err;
        return 0;

err:
        nfs4_legacy_state_shutdown(net);
        return status;
}

static void
nfsd4_legacy_tracking_exit(struct net *net)
{
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);

        nfs4_release_reclaim(nn);
        nfsd4_shutdown_recdir(net);
        nfs4_legacy_state_shutdown(net);
}

/*
 * 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 (d_is_dir(path.dentry)) {
                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)
{
        int status;
        char dname[HEXDIR_LEN];
        struct nfs4_client_reclaim *crp;
        struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);

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

        status = nfs4_make_rec_clidname(dname, &clp->cl_name);
        if (status) {
                legacy_recdir_name_error(clp, status);
                return status;
        }

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

        return -ENOENT;
}

static const struct nfsd4_client_tracking_ops nfsd4_legacy_tracking_ops = {
        .init           = nfsd4_legacy_tracking_init,
        .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();

        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(file_inode(filp)->i_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;
        struct nfsd_net *nn = net_generic(clp->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;
        struct nfsd_net *nn = net_generic(clp->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;
        struct nfsd_net *nn = net_generic(clp->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 nfsd_net *nn)
{
        int ret;
        struct cld_upcall *cup;
        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)nn->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 const 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,
};

/* upcall via usermodehelper */
static char cltrack_prog[PATH_MAX] = "/sbin/nfsdcltrack";
module_param_string(cltrack_prog, cltrack_prog, sizeof(cltrack_prog),
                        S_IRUGO|S_IWUSR);
MODULE_PARM_DESC(cltrack_prog, "Path to the nfsdcltrack upcall program");

static bool cltrack_legacy_disable;
module_param(cltrack_legacy_disable, bool, S_IRUGO|S_IWUSR);
MODULE_PARM_DESC(cltrack_legacy_disable,
                "Disable legacy recoverydir conversion. Default: false");

#define LEGACY_TOPDIR_ENV_PREFIX "NFSDCLTRACK_LEGACY_TOPDIR="
#define LEGACY_RECDIR_ENV_PREFIX "NFSDCLTRACK_LEGACY_RECDIR="
#define HAS_SESSION_ENV_PREFIX "NFSDCLTRACK_CLIENT_HAS_SESSION="
#define GRACE_START_ENV_PREFIX "NFSDCLTRACK_GRACE_START="

static char *
nfsd4_cltrack_legacy_topdir(void)
{
        int copied;
        size_t len;
        char *result;

        if (cltrack_legacy_disable)
                return NULL;

        len = strlen(LEGACY_TOPDIR_ENV_PREFIX) +
                strlen(nfs4_recoverydir()) + 1;

        result = kmalloc(len, GFP_KERNEL);
        if (!result)
                return result;

        copied = snprintf(result, len, LEGACY_TOPDIR_ENV_PREFIX "%s",
                                nfs4_recoverydir());
        if (copied >= len) {
                /* just return nothing if output was truncated */
                kfree(result);
                return NULL;
        }

        return result;
}

static char *
nfsd4_cltrack_legacy_recdir(const struct xdr_netobj *name)
{
        int copied;
        size_t len;
        char *result;

        if (cltrack_legacy_disable)
                return NULL;

        /* +1 is for '/' between "topdir" and "recdir" */
        len = strlen(LEGACY_RECDIR_ENV_PREFIX) +
                strlen(nfs4_recoverydir()) + 1 + HEXDIR_LEN;

        result = kmalloc(len, GFP_KERNEL);
        if (!result)
                return result;

        copied = snprintf(result, len, LEGACY_RECDIR_ENV_PREFIX "%s/",
                                nfs4_recoverydir());
        if (copied > (len - HEXDIR_LEN)) {
                /* just return nothing if output will be truncated */
                kfree(result);
                return NULL;
        }

        copied = nfs4_make_rec_clidname(result + copied, name);
        if (copied) {
                kfree(result);
                return NULL;
        }

        return result;
}

static char *
nfsd4_cltrack_client_has_session(struct nfs4_client *clp)
{
        int copied;
        size_t len;
        char *result;

        /* prefix + Y/N character + terminating NULL */
        len = strlen(HAS_SESSION_ENV_PREFIX) + 1 + 1;

        result = kmalloc(len, GFP_KERNEL);
        if (!result)
                return result;

        copied = snprintf(result, len, HAS_SESSION_ENV_PREFIX "%c",
                                clp->cl_minorversion ? 'Y' : 'N');
        if (copied >= len) {
                /* just return nothing if output was truncated */
                kfree(result);
                return NULL;
        }

        return result;
}

static char *
nfsd4_cltrack_grace_start(time_t grace_start)
{
        int copied;
        size_t len;
        char *result;

        /* prefix + max width of int64_t string + terminating NULL */
        len = strlen(GRACE_START_ENV_PREFIX) + 22 + 1;

        result = kmalloc(len, GFP_KERNEL);
        if (!result)
                return result;

        copied = snprintf(result, len, GRACE_START_ENV_PREFIX "%ld",
                                grace_start);
        if (copied >= len) {
                /* just return nothing if output was truncated */
                kfree(result);
                return NULL;
        }

        return result;
}

static int
nfsd4_umh_cltrack_upcall(char *cmd, char *arg, char *env0, char *env1)
{
        char *envp[3];
        char *argv[4];
        int ret;

        if (unlikely(!cltrack_prog[0])) {
                dprintk("%s: cltrack_prog is disabled\n", __func__);
                return -EACCES;
        }

        dprintk("%s: cmd: %s\n", __func__, cmd);
        dprintk("%s: arg: %s\n", __func__, arg ? arg : "(null)");
        dprintk("%s: env0: %s\n", __func__, env0 ? env0 : "(null)");
        dprintk("%s: env1: %s\n", __func__, env1 ? env1 : "(null)");

        envp[0] = env0;
        envp[1] = env1;
        envp[2] = NULL;

        argv[0] = (char *)cltrack_prog;
        argv[1] = cmd;
        argv[2] = arg;
        argv[3] = NULL;

        ret = call_usermodehelper(argv[0], argv, envp, UMH_WAIT_PROC);
        /*
         * Disable the upcall mechanism if we're getting an ENOENT or EACCES
         * error. The admin can re-enable it on the fly by using sysfs
         * once the problem has been fixed.
         */
        if (ret == -ENOENT || ret == -EACCES) {
                dprintk("NFSD: %s was not found or isn't executable (%d). "
                        "Setting cltrack_prog to blank string!",
                        cltrack_prog, ret);
                cltrack_prog[0] = '\0';
        }
        dprintk("%s: %s return value: %d\n", __func__, cltrack_prog, ret);

        return ret;
}

static char *
bin_to_hex_dup(const unsigned char *src, int srclen)
{
        int i;
        char *buf, *hex;

        /* +1 for terminating NULL */
        buf = kmalloc((srclen * 2) + 1, GFP_KERNEL);
        if (!buf)
                return buf;

        hex = buf;
        for (i = 0; i < srclen; i++) {
                sprintf(hex, "%2.2x", *src++);
                hex += 2;
        }
        return buf;
}

static int
nfsd4_umh_cltrack_init(struct net *net)
{
        int ret;
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);
        char *grace_start = nfsd4_cltrack_grace_start(nn->boot_time);

        /* XXX: The usermode helper s not working in container yet. */
        if (net != &init_net) {
                pr_warn("NFSD: attempt to initialize umh client tracking in a container ignored.\n");
                kfree(grace_start);
                return -EINVAL;
        }

        ret = nfsd4_umh_cltrack_upcall("init", NULL, grace_start, NULL);
        kfree(grace_start);
        return ret;
}

static void
nfsd4_cltrack_upcall_lock(struct nfs4_client *clp)
{
        wait_on_bit_lock(&clp->cl_flags, NFSD4_CLIENT_UPCALL_LOCK,
                         TASK_UNINTERRUPTIBLE);
}

static void
nfsd4_cltrack_upcall_unlock(struct nfs4_client *clp)
{
        smp_mb__before_atomic();
        clear_bit(NFSD4_CLIENT_UPCALL_LOCK, &clp->cl_flags);
        smp_mb__after_atomic();
        wake_up_bit(&clp->cl_flags, NFSD4_CLIENT_UPCALL_LOCK);
}

static void
nfsd4_umh_cltrack_create(struct nfs4_client *clp)
{
        char *hexid, *has_session, *grace_start;
        struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);

        /*
         * With v4.0 clients, there's little difference in outcome between a
         * create and check operation, and we can end up calling into this
         * function multiple times per client (once for each openowner). So,
         * for v4.0 clients skip upcalling once the client has been recorded
         * on stable storage.
         *
         * For v4.1+ clients, the outcome of the two operations is different,
         * so we must ensure that we upcall for the create operation. v4.1+
         * clients call this on RECLAIM_COMPLETE though, so we should only end
         * up doing a single create upcall per client.
         */
        if (clp->cl_minorversion == 0 &&
            test_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags))
                return;

        hexid = bin_to_hex_dup(clp->cl_name.data, clp->cl_name.len);
        if (!hexid) {
                dprintk("%s: can't allocate memory for upcall!\n", __func__);
                return;
        }

        has_session = nfsd4_cltrack_client_has_session(clp);
        grace_start = nfsd4_cltrack_grace_start(nn->boot_time);

        nfsd4_cltrack_upcall_lock(clp);
        if (!nfsd4_umh_cltrack_upcall("create", hexid, has_session, grace_start))
                set_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags);
        nfsd4_cltrack_upcall_unlock(clp);

        kfree(has_session);
        kfree(grace_start);
        kfree(hexid);
}

static void
nfsd4_umh_cltrack_remove(struct nfs4_client *clp)
{
        char *hexid;

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

        hexid = bin_to_hex_dup(clp->cl_name.data, clp->cl_name.len);
        if (!hexid) {
                dprintk("%s: can't allocate memory for upcall!\n", __func__);
                return;
        }

        nfsd4_cltrack_upcall_lock(clp);
        if (test_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags) &&
            nfsd4_umh_cltrack_upcall("remove", hexid, NULL, NULL) == 0)
                clear_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags);
        nfsd4_cltrack_upcall_unlock(clp);

        kfree(hexid);
}

static int
nfsd4_umh_cltrack_check(struct nfs4_client *clp)
{
        int ret;
        char *hexid, *has_session, *legacy;

        if (test_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags))
                return 0;

        hexid = bin_to_hex_dup(clp->cl_name.data, clp->cl_name.len);
        if (!hexid) {
                dprintk("%s: can't allocate memory for upcall!\n", __func__);
                return -ENOMEM;
        }

        has_session = nfsd4_cltrack_client_has_session(clp);
        legacy = nfsd4_cltrack_legacy_recdir(&clp->cl_name);

        nfsd4_cltrack_upcall_lock(clp);
        if (test_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags)) {
                ret = 0;
        } else {
                ret = nfsd4_umh_cltrack_upcall("check", hexid, has_session, legacy);
                if (ret == 0)
                        set_bit(NFSD4_CLIENT_STABLE, &clp->cl_flags);
        }
        nfsd4_cltrack_upcall_unlock(clp);
        kfree(has_session);
        kfree(legacy);
        kfree(hexid);

        return ret;
}

static void
nfsd4_umh_cltrack_grace_done(struct nfsd_net *nn)
{
        char *legacy;
        char timestr[22]; /* FIXME: better way to determine max size? */

        sprintf(timestr, "%ld", nn->boot_time);
        legacy = nfsd4_cltrack_legacy_topdir();
        nfsd4_umh_cltrack_upcall("gracedone", timestr, legacy, NULL);
        kfree(legacy);
}

static const struct nfsd4_client_tracking_ops nfsd4_umh_tracking_ops = {
        .init           = nfsd4_umh_cltrack_init,
        .exit           = NULL,
        .create         = nfsd4_umh_cltrack_create,
        .remove         = nfsd4_umh_cltrack_remove,
        .check          = nfsd4_umh_cltrack_check,
        .grace_done     = nfsd4_umh_cltrack_grace_done,
};

int
nfsd4_client_tracking_init(struct net *net)
{
        int status;
        struct path path;
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);

        /* just run the init if it the method is already decided */
        if (nn->client_tracking_ops)
                goto do_init;

        /*
         * First, try a UMH upcall. It should succeed or fail quickly, so
         * there's little harm in trying that first.
         */
        nn->client_tracking_ops = &nfsd4_umh_tracking_ops;
        status = nn->client_tracking_ops->init(net);
        if (!status)
                return status;

        /*
         * See if the recoverydir exists and is a directory. If it is,
         * then use the legacy ops.
         */
        nn->client_tracking_ops = &nfsd4_legacy_tracking_ops;
        status = kern_path(nfs4_recoverydir(), LOOKUP_FOLLOW, &path);
        if (!status) {
                status = d_is_dir(path.dentry);
                path_put(&path);
                if (status)
                        goto do_init;
        }

        /* Finally, try to use nfsdcld */
        nn->client_tracking_ops = &nfsd4_cld_tracking_ops;
        printk(KERN_WARNING "NFSD: the nfsdcld client tracking upcall will be "
                        "removed in 3.10. Please transition to using "
                        "nfsdcltrack.\n");
do_init:
        status = nn->client_tracking_ops->init(net);
        if (status) {
                printk(KERN_WARNING "NFSD: Unable to initialize client "
                                    "recovery tracking! (%d)\n", status);
                nn->client_tracking_ops = NULL;
        }
        return status;
}

void
nfsd4_client_tracking_exit(struct net *net)
{
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);

        if (nn->client_tracking_ops) {
                if (nn->client_tracking_ops->exit)
                        nn->client_tracking_ops->exit(net);
                nn->client_tracking_ops = NULL;
        }
}

void
nfsd4_client_record_create(struct nfs4_client *clp)
{
        struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);

        if (nn->client_tracking_ops)
                nn->client_tracking_ops->create(clp);
}

void
nfsd4_client_record_remove(struct nfs4_client *clp)
{
        struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);

        if (nn->client_tracking_ops)
                nn->client_tracking_ops->remove(clp);
}

int
nfsd4_client_record_check(struct nfs4_client *clp)
{
        struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);

        if (nn->client_tracking_ops)
                return nn->client_tracking_ops->check(clp);

        return -EOPNOTSUPP;
}

void
nfsd4_record_grace_done(struct nfsd_net *nn)
{
        if (nn->client_tracking_ops)
                nn->client_tracking_ops->grace_done(nn);
}

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);
}