/*
 * linux/fs/lockd/clntproc.c
 *
 * RPC procedures for the client side NLM implementation
 *
 * Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
 */

#include <linux/module.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/fs.h>
#include <linux/nfs_fs.h>
#include <linux/utsname.h>
#include <linux/freezer.h>
#include <linux/sunrpc/clnt.h>
#include <linux/sunrpc/svc.h>
#include <linux/lockd/lockd.h>

#define NLMDBG_FACILITY         NLMDBG_CLIENT
#define NLMCLNT_GRACE_WAIT      (5*HZ)
#define NLMCLNT_POLL_TIMEOUT    (30*HZ)
#define NLMCLNT_MAX_RETRIES     3

static int      nlmclnt_test(struct nlm_rqst *, struct file_lock *);
static int      nlmclnt_lock(struct nlm_rqst *, struct file_lock *);
static int      nlmclnt_unlock(struct nlm_rqst *, struct file_lock *);
static int      nlm_stat_to_errno(__be32 stat);
static void     nlmclnt_locks_init_private(struct file_lock *fl, struct nlm_host *host);
static int      nlmclnt_cancel(struct nlm_host *, int , struct file_lock *);

static const struct rpc_call_ops nlmclnt_unlock_ops;
static const struct rpc_call_ops nlmclnt_cancel_ops;

/*
 * Cookie counter for NLM requests
 */
static atomic_t nlm_cookie = ATOMIC_INIT(0x1234);

void nlmclnt_next_cookie(struct nlm_cookie *c)
{
        u32     cookie = atomic_inc_return(&nlm_cookie);

        memcpy(c->data, &cookie, 4);
        c->len=4;
}

static struct nlm_lockowner *nlm_get_lockowner(struct nlm_lockowner *lockowner)
{
        atomic_inc(&lockowner->count);
        return lockowner;
}

static void nlm_put_lockowner(struct nlm_lockowner *lockowner)
{
        if (!atomic_dec_and_lock(&lockowner->count, &lockowner->host->h_lock))
                return;
        list_del(&lockowner->list);
        spin_unlock(&lockowner->host->h_lock);
        nlmclnt_release_host(lockowner->host);
        kfree(lockowner);
}

static inline int nlm_pidbusy(struct nlm_host *host, uint32_t pid)
{
        struct nlm_lockowner *lockowner;
        list_for_each_entry(lockowner, &host->h_lockowners, list) {
                if (lockowner->pid == pid)
                        return -EBUSY;
        }
        return 0;
}

static inline uint32_t __nlm_alloc_pid(struct nlm_host *host)
{
        uint32_t res;
        do {
                res = host->h_pidcount++;
        } while (nlm_pidbusy(host, res) < 0);
        return res;
}

static struct nlm_lockowner *__nlm_find_lockowner(struct nlm_host *host, fl_owner_t owner)
{
        struct nlm_lockowner *lockowner;
        list_for_each_entry(lockowner, &host->h_lockowners, list) {
                if (lockowner->owner != owner)
                        continue;
                return nlm_get_lockowner(lockowner);
        }
        return NULL;
}

static struct nlm_lockowner *nlm_find_lockowner(struct nlm_host *host, fl_owner_t owner)
{
        struct nlm_lockowner *res, *new = NULL;

        spin_lock(&host->h_lock);
        res = __nlm_find_lockowner(host, owner);
        if (res == NULL) {
                spin_unlock(&host->h_lock);
                new = kmalloc(sizeof(*new), GFP_KERNEL);
                spin_lock(&host->h_lock);
                res = __nlm_find_lockowner(host, owner);
                if (res == NULL && new != NULL) {
                        res = new;
                        atomic_set(&new->count, 1);
                        new->owner = owner;
                        new->pid = __nlm_alloc_pid(host);
                        new->host = nlm_get_host(host);
                        list_add(&new->list, &host->h_lockowners);
                        new = NULL;
                }
        }
        spin_unlock(&host->h_lock);
        kfree(new);
        return res;
}

/*
 * Initialize arguments for TEST/LOCK/UNLOCK/CANCEL calls
 */
static void nlmclnt_setlockargs(struct nlm_rqst *req, struct file_lock *fl)
{
        struct nlm_args *argp = &req->a_args;
        struct nlm_lock *lock = &argp->lock;
        char *nodename = req->a_host->h_rpcclnt->cl_nodename;

        nlmclnt_next_cookie(&argp->cookie);
        memcpy(&lock->fh, NFS_FH(file_inode(fl->fl_file)), sizeof(struct nfs_fh));
        lock->caller  = nodename;
        lock->oh.data = req->a_owner;
        lock->oh.len  = snprintf(req->a_owner, sizeof(req->a_owner), "%u@%s",
                                (unsigned int)fl->fl_u.nfs_fl.owner->pid,
                                nodename);
        lock->svid = fl->fl_u.nfs_fl.owner->pid;
        lock->fl.fl_start = fl->fl_start;
        lock->fl.fl_end = fl->fl_end;
        lock->fl.fl_type = fl->fl_type;
}

static void nlmclnt_release_lockargs(struct nlm_rqst *req)
{
        WARN_ON_ONCE(req->a_args.lock.fl.fl_ops != NULL);
}

/**
 * nlmclnt_proc - Perform a single client-side lock request
 * @host: address of a valid nlm_host context representing the NLM server
 * @cmd: fcntl-style file lock operation to perform
 * @fl: address of arguments for the lock operation
 *
 */
int nlmclnt_proc(struct nlm_host *host, int cmd, struct file_lock *fl)
{
        struct nlm_rqst         *call;
        int                     status;

        call = nlm_alloc_call(host);
        if (call == NULL)
                return -ENOMEM;

        nlmclnt_locks_init_private(fl, host);
        if (!fl->fl_u.nfs_fl.owner) {
                /* lockowner allocation has failed */
                nlmclnt_release_call(call);
                return -ENOMEM;
        }
        /* Set up the argument struct */
        nlmclnt_setlockargs(call, fl);

        if (IS_SETLK(cmd) || IS_SETLKW(cmd)) {
                if (fl->fl_type != F_UNLCK) {
                        call->a_args.block = IS_SETLKW(cmd) ? 1 : 0;
                        status = nlmclnt_lock(call, fl);
                } else
                        status = nlmclnt_unlock(call, fl);
        } else if (IS_GETLK(cmd))
                status = nlmclnt_test(call, fl);
        else
                status = -EINVAL;
        fl->fl_ops->fl_release_private(fl);
        fl->fl_ops = NULL;

        dprintk("lockd: clnt proc returns %d\n", status);
        return status;
}
EXPORT_SYMBOL_GPL(nlmclnt_proc);

/*
 * Allocate an NLM RPC call struct
 */
struct nlm_rqst *nlm_alloc_call(struct nlm_host *host)
{
        struct nlm_rqst *call;

        for(;;) {
                call = kzalloc(sizeof(*call), GFP_KERNEL);
                if (call != NULL) {
                        atomic_set(&call->a_count, 1);
                        locks_init_lock(&call->a_args.lock.fl);
                        locks_init_lock(&call->a_res.lock.fl);
                        call->a_host = nlm_get_host(host);
                        return call;
                }
                if (signalled())
                        break;
                printk("nlm_alloc_call: failed, waiting for memory\n");
                schedule_timeout_interruptible(5*HZ);
        }
        return NULL;
}

void nlmclnt_release_call(struct nlm_rqst *call)
{
        if (!atomic_dec_and_test(&call->a_count))
                return;
        nlmclnt_release_host(call->a_host);
        nlmclnt_release_lockargs(call);
        kfree(call);
}

static void nlmclnt_rpc_release(void *data)
{
        nlmclnt_release_call(data);
}

static int nlm_wait_on_grace(wait_queue_head_t *queue)
{
        DEFINE_WAIT(wait);
        int status = -EINTR;

        prepare_to_wait(queue, &wait, TASK_INTERRUPTIBLE);
        if (!signalled ()) {
                schedule_timeout(NLMCLNT_GRACE_WAIT);
                try_to_freeze();
                if (!signalled ())
                        status = 0;
        }
        finish_wait(queue, &wait);
        return status;
}

/*
 * Generic NLM call
 */
static int
nlmclnt_call(struct rpc_cred *cred, struct nlm_rqst *req, u32 proc)
{
        struct nlm_host *host = req->a_host;
        struct rpc_clnt *clnt;
        struct nlm_args *argp = &req->a_args;
        struct nlm_res  *resp = &req->a_res;
        struct rpc_message msg = {
                .rpc_argp       = argp,
                .rpc_resp       = resp,
                .rpc_cred       = cred,
        };
        int             status;

        dprintk("lockd: call procedure %d on %s\n",
                        (int)proc, host->h_name);

        do {
                if (host->h_reclaiming && !argp->reclaim)
                        goto in_grace_period;

                /* If we have no RPC client yet, create one. */
                if ((clnt = nlm_bind_host(host)) == NULL)
                        return -ENOLCK;
                msg.rpc_proc = &clnt->cl_procinfo[proc];

                /* Perform the RPC call. If an error occurs, try again */
                if ((status = rpc_call_sync(clnt, &msg, 0)) < 0) {
                        dprintk("lockd: rpc_call returned error %d\n", -status);
                        switch (status) {
                        case -EPROTONOSUPPORT:
                                status = -EINVAL;
                                break;
                        case -ECONNREFUSED:
                        case -ETIMEDOUT:
                        case -ENOTCONN:
                                nlm_rebind_host(host);
                                status = -EAGAIN;
                                break;
                        case -ERESTARTSYS:
                                return signalled () ? -EINTR : status;
                        default:
                                break;
                        }
                        break;
                } else
                if (resp->status == nlm_lck_denied_grace_period) {
                        dprintk("lockd: server in grace period\n");
                        if (argp->reclaim) {
                                printk(KERN_WARNING
                                     "lockd: spurious grace period reject?!\n");
                                return -ENOLCK;
                        }
                } else {
                        if (!argp->reclaim) {
                                /* We appear to be out of the grace period */
                                wake_up_all(&host->h_gracewait);
                        }
                        dprintk("lockd: server returns status %d\n",
                                ntohl(resp->status));
                        return 0;       /* Okay, call complete */
                }

in_grace_period:
                /*
                 * The server has rebooted and appears to be in the grace
                 * period during which locks are only allowed to be
                 * reclaimed.
                 * We can only back off and try again later.
                 */
                status = nlm_wait_on_grace(&host->h_gracewait);
        } while (status == 0);

        return status;
}

/*
 * Generic NLM call, async version.
 */
static struct rpc_task *__nlm_async_call(struct nlm_rqst *req, u32 proc, struct rpc_message *msg, const struct rpc_call_ops *tk_ops)
{
        struct nlm_host *host = req->a_host;
        struct rpc_clnt *clnt;
        struct rpc_task_setup task_setup_data = {
                .rpc_message = msg,
                .callback_ops = tk_ops,
                .callback_data = req,
                .flags = RPC_TASK_ASYNC,
        };

        dprintk("lockd: call procedure %d on %s (async)\n",
                        (int)proc, host->h_name);

        /* If we have no RPC client yet, create one. */
        clnt = nlm_bind_host(host);
        if (clnt == NULL)
                goto out_err;
        msg->rpc_proc = &clnt->cl_procinfo[proc];
        task_setup_data.rpc_client = clnt;

        /* bootstrap and kick off the async RPC call */
        return rpc_run_task(&task_setup_data);
out_err:
        tk_ops->rpc_release(req);
        return ERR_PTR(-ENOLCK);
}

static int nlm_do_async_call(struct nlm_rqst *req, u32 proc, struct rpc_message *msg, const struct rpc_call_ops *tk_ops)
{
        struct rpc_task *task;

        task = __nlm_async_call(req, proc, msg, tk_ops);
        if (IS_ERR(task))
                return PTR_ERR(task);
        rpc_put_task(task);
        return 0;
}

/*
 * NLM asynchronous call.
 */
int nlm_async_call(struct nlm_rqst *req, u32 proc, const struct rpc_call_ops *tk_ops)
{
        struct rpc_message msg = {
                .rpc_argp       = &req->a_args,
                .rpc_resp       = &req->a_res,
        };
        return nlm_do_async_call(req, proc, &msg, tk_ops);
}

int nlm_async_reply(struct nlm_rqst *req, u32 proc, const struct rpc_call_ops *tk_ops)
{
        struct rpc_message msg = {
                .rpc_argp       = &req->a_res,
        };
        return nlm_do_async_call(req, proc, &msg, tk_ops);
}

/*
 * NLM client asynchronous call.
 *
 * Note that although the calls are asynchronous, and are therefore
 *      guaranteed to complete, we still always attempt to wait for
 *      completion in order to be able to correctly track the lock
 *      state.
 */
static int nlmclnt_async_call(struct rpc_cred *cred, struct nlm_rqst *req, u32 proc, const struct rpc_call_ops *tk_ops)
{
        struct rpc_message msg = {
                .rpc_argp       = &req->a_args,
                .rpc_resp       = &req->a_res,
                .rpc_cred       = cred,
        };
        struct rpc_task *task;
        int err;

        task = __nlm_async_call(req, proc, &msg, tk_ops);
        if (IS_ERR(task))
                return PTR_ERR(task);
        err = rpc_wait_for_completion_task(task);
        rpc_put_task(task);
        return err;
}

/*
 * TEST for the presence of a conflicting lock
 */
static int
nlmclnt_test(struct nlm_rqst *req, struct file_lock *fl)
{
        int     status;

        status = nlmclnt_call(nfs_file_cred(fl->fl_file), req, NLMPROC_TEST);
        if (status < 0)
                goto out;

        switch (req->a_res.status) {
                case nlm_granted:
                        fl->fl_type = F_UNLCK;
                        break;
                case nlm_lck_denied:
                        /*
                         * Report the conflicting lock back to the application.
                         */
                        fl->fl_start = req->a_res.lock.fl.fl_start;
                        fl->fl_end = req->a_res.lock.fl.fl_end;
                        fl->fl_type = req->a_res.lock.fl.fl_type;
                        fl->fl_pid = 0;
                        break;
                default:
                        status = nlm_stat_to_errno(req->a_res.status);
        }
out:
        nlmclnt_release_call(req);
        return status;
}

static void nlmclnt_locks_copy_lock(struct file_lock *new, struct file_lock *fl)
{
        spin_lock(&fl->fl_u.nfs_fl.owner->host->h_lock);
        new->fl_u.nfs_fl.state = fl->fl_u.nfs_fl.state;
        new->fl_u.nfs_fl.owner = nlm_get_lockowner(fl->fl_u.nfs_fl.owner);
        list_add_tail(&new->fl_u.nfs_fl.list, &fl->fl_u.nfs_fl.owner->host->h_granted);
        spin_unlock(&fl->fl_u.nfs_fl.owner->host->h_lock);
}

static void nlmclnt_locks_release_private(struct file_lock *fl)
{
        spin_lock(&fl->fl_u.nfs_fl.owner->host->h_lock);
        list_del(&fl->fl_u.nfs_fl.list);
        spin_unlock(&fl->fl_u.nfs_fl.owner->host->h_lock);
        nlm_put_lockowner(fl->fl_u.nfs_fl.owner);
}

static const struct file_lock_operations nlmclnt_lock_ops = {
        .fl_copy_lock = nlmclnt_locks_copy_lock,
        .fl_release_private = nlmclnt_locks_release_private,
};

static void nlmclnt_locks_init_private(struct file_lock *fl, struct nlm_host *host)
{
        fl->fl_u.nfs_fl.state = 0;
        fl->fl_u.nfs_fl.owner = nlm_find_lockowner(host, fl->fl_owner);
        INIT_LIST_HEAD(&fl->fl_u.nfs_fl.list);
        fl->fl_ops = &nlmclnt_lock_ops;
}

static int do_vfs_lock(struct file_lock *fl)
{
        int res = 0;
        switch (fl->fl_flags & (FL_POSIX|FL_FLOCK)) {
                case FL_POSIX:
                        res = posix_lock_file_wait(fl->fl_file, fl);
                        break;
                case FL_FLOCK:
                        res = flock_lock_file_wait(fl->fl_file, fl);
                        break;
                default:
                        BUG();
        }
        return res;
}

/*
 * LOCK: Try to create a lock
 *
 *                      Programmer Harassment Alert
 *
 * When given a blocking lock request in a sync RPC call, the HPUX lockd
 * will faithfully return LCK_BLOCKED but never cares to notify us when
 * the lock could be granted. This way, our local process could hang
 * around forever waiting for the callback.
 *
 *  Solution A: Implement busy-waiting
 *  Solution B: Use the async version of the call (NLM_LOCK_{MSG,RES})
 *
 * For now I am implementing solution A, because I hate the idea of
 * re-implementing lockd for a third time in two months. The async
 * calls shouldn't be too hard to do, however.
 *
 * This is one of the lovely things about standards in the NFS area:
 * they're so soft and squishy you can't really blame HP for doing this.
 */
static int
nlmclnt_lock(struct nlm_rqst *req, struct file_lock *fl)
{
        struct rpc_cred *cred = nfs_file_cred(fl->fl_file);
        struct nlm_host *host = req->a_host;
        struct nlm_res  *resp = &req->a_res;
        struct nlm_wait *block = NULL;
        unsigned char fl_flags = fl->fl_flags;
        unsigned char fl_type;
        int status = -ENOLCK;

        if (nsm_monitor(host) < 0)
                goto out;
        req->a_args.state = nsm_local_state;

        fl->fl_flags |= FL_ACCESS;
        status = do_vfs_lock(fl);
        fl->fl_flags = fl_flags;
        if (status < 0)
                goto out;

        block = nlmclnt_prepare_block(host, fl);
again:
        /*
         * Initialise resp->status to a valid non-zero value,
         * since 0 == nlm_lck_granted
         */
        resp->status = nlm_lck_blocked;
        for(;;) {
                /* Reboot protection */
                fl->fl_u.nfs_fl.state = host->h_state;
                status = nlmclnt_call(cred, req, NLMPROC_LOCK);
                if (status < 0)
                        break;
                /* Did a reclaimer thread notify us of a server reboot? */
                if (resp->status ==  nlm_lck_denied_grace_period)
                        continue;
                if (resp->status != nlm_lck_blocked)
                        break;
                /* Wait on an NLM blocking lock */
                status = nlmclnt_block(block, req, NLMCLNT_POLL_TIMEOUT);
                if (status < 0)
                        break;
                if (resp->status != nlm_lck_blocked)
                        break;
        }

        /* if we were interrupted while blocking, then cancel the lock request
         * and exit
         */
        if (resp->status == nlm_lck_blocked) {
                if (!req->a_args.block)
                        goto out_unlock;
                if (nlmclnt_cancel(host, req->a_args.block, fl) == 0)
                        goto out_unblock;
        }

        if (resp->status == nlm_granted) {
                down_read(&host->h_rwsem);
                /* Check whether or not the server has rebooted */
                if (fl->fl_u.nfs_fl.state != host->h_state) {
                        up_read(&host->h_rwsem);
                        goto again;
                }
                /* Ensure the resulting lock will get added to granted list */
                fl->fl_flags |= FL_SLEEP;
                if (do_vfs_lock(fl) < 0)
                        printk(KERN_WARNING "%s: VFS is out of sync with lock manager!\n", __func__);
                up_read(&host->h_rwsem);
                fl->fl_flags = fl_flags;
                status = 0;
        }
        if (status < 0)
                goto out_unlock;
        /*
         * EAGAIN doesn't make sense for sleeping locks, and in some
         * cases NLM_LCK_DENIED is returned for a permanent error.  So
         * turn it into an ENOLCK.
         */
        if (resp->status == nlm_lck_denied && (fl_flags & FL_SLEEP))
                status = -ENOLCK;
        else
                status = nlm_stat_to_errno(resp->status);
out_unblock:
        nlmclnt_finish_block(block);
out:
        nlmclnt_release_call(req);
        return status;
out_unlock:
        /* Fatal error: ensure that we remove the lock altogether */
        dprintk("lockd: lock attempt ended in fatal error.\n"
                "       Attempting to unlock.\n");
        nlmclnt_finish_block(block);
        fl_type = fl->fl_type;
        fl->fl_type = F_UNLCK;
        down_read(&host->h_rwsem);
        do_vfs_lock(fl);
        up_read(&host->h_rwsem);
        fl->fl_type = fl_type;
        fl->fl_flags = fl_flags;
        nlmclnt_async_call(cred, req, NLMPROC_UNLOCK, &nlmclnt_unlock_ops);
        return status;
}

/*
 * RECLAIM: Try to reclaim a lock
 */
int
nlmclnt_reclaim(struct nlm_host *host, struct file_lock *fl,
                struct nlm_rqst *req)
{
        int             status;

        memset(req, 0, sizeof(*req));
        locks_init_lock(&req->a_args.lock.fl);
        locks_init_lock(&req->a_res.lock.fl);
        req->a_host  = host;

        /* Set up the argument struct */
        nlmclnt_setlockargs(req, fl);
        req->a_args.reclaim = 1;

        status = nlmclnt_call(nfs_file_cred(fl->fl_file), req, NLMPROC_LOCK);
        if (status >= 0 && req->a_res.status == nlm_granted)
                return 0;

        printk(KERN_WARNING "lockd: failed to reclaim lock for pid %d "
                                "(errno %d, status %d)\n", fl->fl_pid,
                                status, ntohl(req->a_res.status));

        /*
         * FIXME: This is a serious failure. We can
         *
         *  a.  Ignore the problem
         *  b.  Send the owning process some signal (Linux doesn't have
         *      SIGLOST, though...)
         *  c.  Retry the operation
         *
         * Until someone comes up with a simple implementation
         * for b or c, I'll choose option a.
         */

        return -ENOLCK;
}

/*
 * UNLOCK: remove an existing lock
 */
static int
nlmclnt_unlock(struct nlm_rqst *req, struct file_lock *fl)
{
        struct nlm_host *host = req->a_host;
        struct nlm_res  *resp = &req->a_res;
        int status;
        unsigned char fl_flags = fl->fl_flags;

        /*
         * Note: the server is supposed to either grant us the unlock
         * request, or to deny it with NLM_LCK_DENIED_GRACE_PERIOD. In either
         * case, we want to unlock.
         */
        fl->fl_flags |= FL_EXISTS;
        down_read(&host->h_rwsem);
        status = do_vfs_lock(fl);
        up_read(&host->h_rwsem);
        fl->fl_flags = fl_flags;
        if (status == -ENOENT) {
                status = 0;
                goto out;
        }

        atomic_inc(&req->a_count);
        status = nlmclnt_async_call(nfs_file_cred(fl->fl_file), req,
                        NLMPROC_UNLOCK, &nlmclnt_unlock_ops);
        if (status < 0)
                goto out;

        if (resp->status == nlm_granted)
                goto out;

        if (resp->status != nlm_lck_denied_nolocks)
                printk("lockd: unexpected unlock status: %d\n",
                        ntohl(resp->status));
        /* What to do now? I'm out of my depth... */
        status = -ENOLCK;
out:
        nlmclnt_release_call(req);
        return status;
}

static void nlmclnt_unlock_callback(struct rpc_task *task, void *data)
{
        struct nlm_rqst *req = data;
        u32 status = ntohl(req->a_res.status);

        if (RPC_ASSASSINATED(task))
                goto die;

        if (task->tk_status < 0) {
                dprintk("lockd: unlock failed (err = %d)\n", -task->tk_status);
                switch (task->tk_status) {
                case -EACCES:
                case -EIO:
                        goto die;
                default:
                        goto retry_rebind;
                }
        }
        if (status == NLM_LCK_DENIED_GRACE_PERIOD) {
                rpc_delay(task, NLMCLNT_GRACE_WAIT);
                goto retry_unlock;
        }
        if (status != NLM_LCK_GRANTED)
                printk(KERN_WARNING "lockd: unexpected unlock status: %d\n", status);
die:
        return;
 retry_rebind:
        nlm_rebind_host(req->a_host);
 retry_unlock:
        rpc_restart_call(task);
}

static const struct rpc_call_ops nlmclnt_unlock_ops = {
        .rpc_call_done = nlmclnt_unlock_callback,
        .rpc_release = nlmclnt_rpc_release,
};

/*
 * Cancel a blocked lock request.
 * We always use an async RPC call for this in order not to hang a
 * process that has been Ctrl-C'ed.
 */
static int nlmclnt_cancel(struct nlm_host *host, int block, struct file_lock *fl)
{
        struct nlm_rqst *req;
        int status;

        dprintk("lockd: blocking lock attempt was interrupted by a signal.\n"
                "       Attempting to cancel lock.\n");

        req = nlm_alloc_call(host);
        if (!req)
                return -ENOMEM;
        req->a_flags = RPC_TASK_ASYNC;

        nlmclnt_setlockargs(req, fl);
        req->a_args.block = block;

        atomic_inc(&req->a_count);
        status = nlmclnt_async_call(nfs_file_cred(fl->fl_file), req,
                        NLMPROC_CANCEL, &nlmclnt_cancel_ops);
        if (status == 0 && req->a_res.status == nlm_lck_denied)
                status = -ENOLCK;
        nlmclnt_release_call(req);
        return status;
}

static void nlmclnt_cancel_callback(struct rpc_task *task, void *data)
{
        struct nlm_rqst *req = data;
        u32 status = ntohl(req->a_res.status);

        if (RPC_ASSASSINATED(task))
                goto die;

        if (task->tk_status < 0) {
                dprintk("lockd: CANCEL call error %d, retrying.\n",
                                        task->tk_status);
                goto retry_cancel;
        }

        dprintk("lockd: cancel status %u (task %u)\n",
                        status, task->tk_pid);

        switch (status) {
        case NLM_LCK_GRANTED:
        case NLM_LCK_DENIED_GRACE_PERIOD:
        case NLM_LCK_DENIED:
                /* Everything's good */
                break;
        case NLM_LCK_DENIED_NOLOCKS:
                dprintk("lockd: CANCEL failed (server has no locks)\n");
                goto retry_cancel;
        default:
                printk(KERN_NOTICE "lockd: weird return %d for CANCEL call\n",
                        status);
        }

die:
        return;

retry_cancel:
        /* Don't ever retry more than 3 times */
        if (req->a_retries++ >= NLMCLNT_MAX_RETRIES)
                goto die;
        nlm_rebind_host(req->a_host);
        rpc_restart_call(task);
        rpc_delay(task, 30 * HZ);
}

static const struct rpc_call_ops nlmclnt_cancel_ops = {
        .rpc_call_done = nlmclnt_cancel_callback,
        .rpc_release = nlmclnt_rpc_release,
};

/*
 * Convert an NLM status code to a generic kernel errno
 */
static int
nlm_stat_to_errno(__be32 status)
{
        switch(ntohl(status)) {
        case NLM_LCK_GRANTED:
                return 0;
        case NLM_LCK_DENIED:
                return -EAGAIN;
        case NLM_LCK_DENIED_NOLOCKS:
        case NLM_LCK_DENIED_GRACE_PERIOD:
                return -ENOLCK;
        case NLM_LCK_BLOCKED:
                printk(KERN_NOTICE "lockd: unexpected status NLM_BLOCKED\n");
                return -ENOLCK;
#ifdef CONFIG_LOCKD_V4
        case NLM_DEADLCK:
                return -EDEADLK;
        case NLM_ROFS:
                return -EROFS;
        case NLM_STALE_FH:
                return -ESTALE;
        case NLM_FBIG:
                return -EOVERFLOW;
        case NLM_FAILED:
                return -ENOLCK;
#endif
        }
        printk(KERN_NOTICE "lockd: unexpected server status %d\n",
                 ntohl(status));
        return -ENOLCK;
}