ACPI: thinkpad-acpi: use killable instead of interruptible mutexes

[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / net / sunrpc / clnt.c

/*
 *  linux/net/sunrpc/clnt.c
 *
 *  This file contains the high-level RPC interface.
 *  It is modeled as a finite state machine to support both synchronous
 *  and asynchronous requests.
 *
 *  -   RPC header generation and argument serialization.
 *  -   Credential refresh.
 *  -   TCP connect handling.
 *  -   Retry of operation when it is suspected the operation failed because
 *      of uid squashing on the server, or when the credentials were stale
 *      and need to be refreshed, or when a packet was damaged in transit.
 *      This may be have to be moved to the VFS layer.
 *
 *  NB: BSD uses a more intelligent approach to guessing when a request
 *  or reply has been lost by keeping the RTO estimate for each procedure.
 *  We currently make do with a constant timeout value.
 *
 *  Copyright (C) 1992,1993 Rick Sladkey <jrs@world.std.com>
 *  Copyright (C) 1995,1996 Olaf Kirch <okir@monad.swb.de>
 */

#include <asm/system.h>

#include <linux/module.h>
#include <linux/types.h>
#include <linux/kallsyms.h>
#include <linux/mm.h>
#include <linux/slab.h>
#include <linux/smp_lock.h>
#include <linux/utsname.h>
#include <linux/workqueue.h>
#include <linux/in6.h>

#include <linux/sunrpc/clnt.h>
#include <linux/sunrpc/rpc_pipe_fs.h>
#include <linux/sunrpc/metrics.h>


#ifdef RPC_DEBUG
# define RPCDBG_FACILITY        RPCDBG_CALL
#endif

#define dprint_status(t)                                        \
        dprintk("RPC: %5u %s (status %d)\n", t->tk_pid,         \
                        __func__, t->tk_status)

/*
 * All RPC clients are linked into this list
 */
static LIST_HEAD(all_clients);
static DEFINE_SPINLOCK(rpc_client_lock);

static DECLARE_WAIT_QUEUE_HEAD(destroy_wait);


static void     call_start(struct rpc_task *task);
static void     call_reserve(struct rpc_task *task);
static void     call_reserveresult(struct rpc_task *task);
static void     call_allocate(struct rpc_task *task);
static void     call_decode(struct rpc_task *task);
static void     call_bind(struct rpc_task *task);
static void     call_bind_status(struct rpc_task *task);
static void     call_transmit(struct rpc_task *task);
static void     call_status(struct rpc_task *task);
static void     call_transmit_status(struct rpc_task *task);
static void     call_refresh(struct rpc_task *task);
static void     call_refreshresult(struct rpc_task *task);
static void     call_timeout(struct rpc_task *task);
static void     call_connect(struct rpc_task *task);
static void     call_connect_status(struct rpc_task *task);

static __be32   *rpc_encode_header(struct rpc_task *task);
static __be32   *rpc_verify_header(struct rpc_task *task);
static int      rpc_ping(struct rpc_clnt *clnt, int flags);

static void rpc_register_client(struct rpc_clnt *clnt)
{
        spin_lock(&rpc_client_lock);
        list_add(&clnt->cl_clients, &all_clients);
        spin_unlock(&rpc_client_lock);
}

static void rpc_unregister_client(struct rpc_clnt *clnt)
{
        spin_lock(&rpc_client_lock);
        list_del(&clnt->cl_clients);
        spin_unlock(&rpc_client_lock);
}

static int
rpc_setup_pipedir(struct rpc_clnt *clnt, char *dir_name)
{
        static uint32_t clntid;
        int error;

        clnt->cl_vfsmnt = ERR_PTR(-ENOENT);
        clnt->cl_dentry = ERR_PTR(-ENOENT);
        if (dir_name == NULL)
                return 0;

        clnt->cl_vfsmnt = rpc_get_mount();
        if (IS_ERR(clnt->cl_vfsmnt))
                return PTR_ERR(clnt->cl_vfsmnt);

        for (;;) {
                snprintf(clnt->cl_pathname, sizeof(clnt->cl_pathname),
                                "%s/clnt%x", dir_name,
                                (unsigned int)clntid++);
                clnt->cl_pathname[sizeof(clnt->cl_pathname) - 1] = '\0';
                clnt->cl_dentry = rpc_mkdir(clnt->cl_pathname, clnt);
                if (!IS_ERR(clnt->cl_dentry))
                        return 0;
                error = PTR_ERR(clnt->cl_dentry);
                if (error != -EEXIST) {
                        printk(KERN_INFO "RPC: Couldn't create pipefs entry %s, error %d\n",
                                        clnt->cl_pathname, error);
                        rpc_put_mount();
                        return error;
                }
        }
}

static struct rpc_clnt * rpc_new_client(const struct rpc_create_args *args, struct rpc_xprt *xprt)
{
        struct rpc_program      *program = args->program;
        struct rpc_version      *version;
        struct rpc_clnt         *clnt = NULL;
        struct rpc_auth         *auth;
        int err;
        size_t len;

        /* sanity check the name before trying to print it */
        err = -EINVAL;
        len = strlen(args->servername);
        if (len > RPC_MAXNETNAMELEN)
                goto out_no_rpciod;
        len++;

        dprintk("RPC:       creating %s client for %s (xprt %p)\n",
                        program->name, args->servername, xprt);

        err = rpciod_up();
        if (err)
                goto out_no_rpciod;
        err = -EINVAL;
        if (!xprt)
                goto out_no_xprt;

        if (args->version >= program->nrvers)
                goto out_err;
        version = program->version[args->version];
        if (version == NULL)
                goto out_err;

        err = -ENOMEM;
        clnt = kzalloc(sizeof(*clnt), GFP_KERNEL);
        if (!clnt)
                goto out_err;
        clnt->cl_parent = clnt;

        clnt->cl_server = clnt->cl_inline_name;
        if (len > sizeof(clnt->cl_inline_name)) {
                char *buf = kmalloc(len, GFP_KERNEL);
                if (buf != NULL)
                        clnt->cl_server = buf;
                else
                        len = sizeof(clnt->cl_inline_name);
        }
        strlcpy(clnt->cl_server, args->servername, len);

        clnt->cl_xprt     = xprt;
        clnt->cl_procinfo = version->procs;
        clnt->cl_maxproc  = version->nrprocs;
        clnt->cl_protname = program->name;
        clnt->cl_prog     = args->prognumber ? : program->number;
        clnt->cl_vers     = version->number;
        clnt->cl_stats    = program->stats;
        clnt->cl_metrics  = rpc_alloc_iostats(clnt);
        err = -ENOMEM;
        if (clnt->cl_metrics == NULL)
                goto out_no_stats;
        clnt->cl_program  = program;
        INIT_LIST_HEAD(&clnt->cl_tasks);
        spin_lock_init(&clnt->cl_lock);

        if (!xprt_bound(clnt->cl_xprt))
                clnt->cl_autobind = 1;

        clnt->cl_timeout = xprt->timeout;
        if (args->timeout != NULL) {
                memcpy(&clnt->cl_timeout_default, args->timeout,
                                sizeof(clnt->cl_timeout_default));
                clnt->cl_timeout = &clnt->cl_timeout_default;
        }

        clnt->cl_rtt = &clnt->cl_rtt_default;
        rpc_init_rtt(&clnt->cl_rtt_default, clnt->cl_timeout->to_initval);

        kref_init(&clnt->cl_kref);

        err = rpc_setup_pipedir(clnt, program->pipe_dir_name);
        if (err < 0)
                goto out_no_path;

        auth = rpcauth_create(args->authflavor, clnt);
        if (IS_ERR(auth)) {
                printk(KERN_INFO "RPC: Couldn't create auth handle (flavor %u)\n",
                                args->authflavor);
                err = PTR_ERR(auth);
                goto out_no_auth;
        }

        /* save the nodename */
        clnt->cl_nodelen = strlen(init_utsname()->nodename);
        if (clnt->cl_nodelen > UNX_MAXNODENAME)
                clnt->cl_nodelen = UNX_MAXNODENAME;
        memcpy(clnt->cl_nodename, init_utsname()->nodename, clnt->cl_nodelen);
        rpc_register_client(clnt);
        return clnt;

out_no_auth:
        if (!IS_ERR(clnt->cl_dentry)) {
                rpc_rmdir(clnt->cl_dentry);
                rpc_put_mount();
        }
out_no_path:
        rpc_free_iostats(clnt->cl_metrics);
out_no_stats:
        if (clnt->cl_server != clnt->cl_inline_name)
                kfree(clnt->cl_server);
        kfree(clnt);
out_err:
        xprt_put(xprt);
out_no_xprt:
        rpciod_down();
out_no_rpciod:
        return ERR_PTR(err);
}

/*
 * rpc_create - create an RPC client and transport with one call
 * @args: rpc_clnt create argument structure
 *
 * Creates and initializes an RPC transport and an RPC client.
 *
 * It can ping the server in order to determine if it is up, and to see if
 * it supports this program and version.  RPC_CLNT_CREATE_NOPING disables
 * this behavior so asynchronous tasks can also use rpc_create.
 */
struct rpc_clnt *rpc_create(struct rpc_create_args *args)
{
        struct rpc_xprt *xprt;
        struct rpc_clnt *clnt;
        struct xprt_create xprtargs = {
                .ident = args->protocol,
                .srcaddr = args->saddress,
                .dstaddr = args->address,
                .addrlen = args->addrsize,
        };
        char servername[48];

        /*
         * If the caller chooses not to specify a hostname, whip
         * up a string representation of the passed-in address.
         */
        if (args->servername == NULL) {
                servername[0] = '\0';
                switch (args->address->sa_family) {
                case AF_INET: {
                        struct sockaddr_in *sin =
                                        (struct sockaddr_in *)args->address;
                        snprintf(servername, sizeof(servername), NIPQUAD_FMT,
                                 NIPQUAD(sin->sin_addr.s_addr));
                        break;
                }
                case AF_INET6: {
                        struct sockaddr_in6 *sin =
                                        (struct sockaddr_in6 *)args->address;
                        snprintf(servername, sizeof(servername), NIP6_FMT,
                                 NIP6(sin->sin6_addr));
                        break;
                }
                default:
                        /* caller wants default server name, but
                         * address family isn't recognized. */
                        return ERR_PTR(-EINVAL);
                }
                args->servername = servername;
        }

        xprt = xprt_create_transport(&xprtargs);
        if (IS_ERR(xprt))
                return (struct rpc_clnt *)xprt;

        /*
         * By default, kernel RPC client connects from a reserved port.
         * CAP_NET_BIND_SERVICE will not be set for unprivileged requesters,
         * but it is always enabled for rpciod, which handles the connect
         * operation.
         */
        xprt->resvport = 1;
        if (args->flags & RPC_CLNT_CREATE_NONPRIVPORT)
                xprt->resvport = 0;

        clnt = rpc_new_client(args, xprt);
        if (IS_ERR(clnt))
                return clnt;

        if (!(args->flags & RPC_CLNT_CREATE_NOPING)) {
                int err = rpc_ping(clnt, RPC_TASK_SOFT);
                if (err != 0) {
                        rpc_shutdown_client(clnt);
                        return ERR_PTR(err);
                }
        }

        clnt->cl_softrtry = 1;
        if (args->flags & RPC_CLNT_CREATE_HARDRTRY)
                clnt->cl_softrtry = 0;

        if (args->flags & RPC_CLNT_CREATE_AUTOBIND)
                clnt->cl_autobind = 1;
        if (args->flags & RPC_CLNT_CREATE_DISCRTRY)
                clnt->cl_discrtry = 1;
        if (!(args->flags & RPC_CLNT_CREATE_QUIET))
                clnt->cl_chatty = 1;

        return clnt;
}
EXPORT_SYMBOL_GPL(rpc_create);

/*
 * This function clones the RPC client structure. It allows us to share the
 * same transport while varying parameters such as the authentication
 * flavour.
 */
struct rpc_clnt *
rpc_clone_client(struct rpc_clnt *clnt)
{
        struct rpc_clnt *new;
        int err = -ENOMEM;

        new = kmemdup(clnt, sizeof(*new), GFP_KERNEL);
        if (!new)
                goto out_no_clnt;
        new->cl_parent = clnt;
        /* Turn off autobind on clones */
        new->cl_autobind = 0;
        INIT_LIST_HEAD(&new->cl_tasks);
        spin_lock_init(&new->cl_lock);
        rpc_init_rtt(&new->cl_rtt_default, clnt->cl_timeout->to_initval);
        new->cl_metrics = rpc_alloc_iostats(clnt);
        if (new->cl_metrics == NULL)
                goto out_no_stats;
        kref_init(&new->cl_kref);
        err = rpc_setup_pipedir(new, clnt->cl_program->pipe_dir_name);
        if (err != 0)
                goto out_no_path;
        if (new->cl_auth)
                atomic_inc(&new->cl_auth->au_count);
        xprt_get(clnt->cl_xprt);
        kref_get(&clnt->cl_kref);
        rpc_register_client(new);
        rpciod_up();
        return new;
out_no_path:
        rpc_free_iostats(new->cl_metrics);
out_no_stats:
        kfree(new);
out_no_clnt:
        dprintk("RPC:       %s: returned error %d\n", __func__, err);
        return ERR_PTR(err);
}
EXPORT_SYMBOL_GPL(rpc_clone_client);

/*
 * Properly shut down an RPC client, terminating all outstanding
 * requests.
 */
void rpc_shutdown_client(struct rpc_clnt *clnt)
{
        dprintk("RPC:       shutting down %s client for %s\n",
                        clnt->cl_protname, clnt->cl_server);

        while (!list_empty(&clnt->cl_tasks)) {
                rpc_killall_tasks(clnt);
                wait_event_timeout(destroy_wait,
                        list_empty(&clnt->cl_tasks), 1*HZ);
        }

        rpc_release_client(clnt);
}
EXPORT_SYMBOL_GPL(rpc_shutdown_client);

/*
 * Free an RPC client
 */
static void
rpc_free_client(struct kref *kref)
{
        struct rpc_clnt *clnt = container_of(kref, struct rpc_clnt, cl_kref);

        dprintk("RPC:       destroying %s client for %s\n",
                        clnt->cl_protname, clnt->cl_server);
        if (!IS_ERR(clnt->cl_dentry)) {
                rpc_rmdir(clnt->cl_dentry);
                rpc_put_mount();
        }
        if (clnt->cl_parent != clnt) {
                rpc_release_client(clnt->cl_parent);
                goto out_free;
        }
        if (clnt->cl_server != clnt->cl_inline_name)
                kfree(clnt->cl_server);
out_free:
        rpc_unregister_client(clnt);
        rpc_free_iostats(clnt->cl_metrics);
        clnt->cl_metrics = NULL;
        xprt_put(clnt->cl_xprt);
        rpciod_down();
        kfree(clnt);
}

/*
 * Free an RPC client
 */
static void
rpc_free_auth(struct kref *kref)
{
        struct rpc_clnt *clnt = container_of(kref, struct rpc_clnt, cl_kref);

        if (clnt->cl_auth == NULL) {
                rpc_free_client(kref);
                return;
        }

        /*
         * Note: RPCSEC_GSS may need to send NULL RPC calls in order to
         *       release remaining GSS contexts. This mechanism ensures
         *       that it can do so safely.
         */
        kref_init(kref);
        rpcauth_release(clnt->cl_auth);
        clnt->cl_auth = NULL;
        kref_put(kref, rpc_free_client);
}

/*
 * Release reference to the RPC client
 */
void
rpc_release_client(struct rpc_clnt *clnt)
{
        dprintk("RPC:       rpc_release_client(%p)\n", clnt);

        if (list_empty(&clnt->cl_tasks))
                wake_up(&destroy_wait);
        kref_put(&clnt->cl_kref, rpc_free_auth);
}

/**
 * rpc_bind_new_program - bind a new RPC program to an existing client
 * @old: old rpc_client
 * @program: rpc program to set
 * @vers: rpc program version
 *
 * Clones the rpc client and sets up a new RPC program. This is mainly
 * of use for enabling different RPC programs to share the same transport.
 * The Sun NFSv2/v3 ACL protocol can do this.
 */
struct rpc_clnt *rpc_bind_new_program(struct rpc_clnt *old,
                                      struct rpc_program *program,
                                      u32 vers)
{
        struct rpc_clnt *clnt;
        struct rpc_version *version;
        int err;

        BUG_ON(vers >= program->nrvers || !program->version[vers]);
        version = program->version[vers];
        clnt = rpc_clone_client(old);
        if (IS_ERR(clnt))
                goto out;
        clnt->cl_procinfo = version->procs;
        clnt->cl_maxproc  = version->nrprocs;
        clnt->cl_protname = program->name;
        clnt->cl_prog     = program->number;
        clnt->cl_vers     = version->number;
        clnt->cl_stats    = program->stats;
        err = rpc_ping(clnt, RPC_TASK_SOFT);
        if (err != 0) {
                rpc_shutdown_client(clnt);
                clnt = ERR_PTR(err);
        }
out:
        return clnt;
}
EXPORT_SYMBOL_GPL(rpc_bind_new_program);

/*
 * Default callback for async RPC calls
 */
static void
rpc_default_callback(struct rpc_task *task, void *data)
{
}

static const struct rpc_call_ops rpc_default_ops = {
        .rpc_call_done = rpc_default_callback,
};

/**
 * rpc_run_task - Allocate a new RPC task, then run rpc_execute against it
 * @task_setup_data: pointer to task initialisation data
 */
struct rpc_task *rpc_run_task(const struct rpc_task_setup *task_setup_data)
{
        struct rpc_task *task, *ret;

        task = rpc_new_task(task_setup_data);
        if (task == NULL) {
                rpc_release_calldata(task_setup_data->callback_ops,
                                task_setup_data->callback_data);
                ret = ERR_PTR(-ENOMEM);
                goto out;
        }

        if (task->tk_status != 0) {
                ret = ERR_PTR(task->tk_status);
                rpc_put_task(task);
                goto out;
        }
        atomic_inc(&task->tk_count);
        rpc_execute(task);
        ret = task;
out:
        return ret;
}
EXPORT_SYMBOL_GPL(rpc_run_task);

/**
 * rpc_call_sync - Perform a synchronous RPC call
 * @clnt: pointer to RPC client
 * @msg: RPC call parameters
 * @flags: RPC call flags
 */
int rpc_call_sync(struct rpc_clnt *clnt, const struct rpc_message *msg, int flags)
{
        struct rpc_task *task;
        struct rpc_task_setup task_setup_data = {
                .rpc_client = clnt,
                .rpc_message = msg,
                .callback_ops = &rpc_default_ops,
                .flags = flags,
        };
        int status;

        BUG_ON(flags & RPC_TASK_ASYNC);

        task = rpc_run_task(&task_setup_data);
        if (IS_ERR(task))
                return PTR_ERR(task);
        status = task->tk_status;
        rpc_put_task(task);
        return status;
}
EXPORT_SYMBOL_GPL(rpc_call_sync);

/**
 * rpc_call_async - Perform an asynchronous RPC call
 * @clnt: pointer to RPC client
 * @msg: RPC call parameters
 * @flags: RPC call flags
 * @tk_ops: RPC call ops
 * @data: user call data
 */
int
rpc_call_async(struct rpc_clnt *clnt, const struct rpc_message *msg, int flags,
               const struct rpc_call_ops *tk_ops, void *data)
{
        struct rpc_task *task;
        struct rpc_task_setup task_setup_data = {
                .rpc_client = clnt,
                .rpc_message = msg,
                .callback_ops = tk_ops,
                .callback_data = data,
                .flags = flags|RPC_TASK_ASYNC,
        };

        task = rpc_run_task(&task_setup_data);
        if (IS_ERR(task))
                return PTR_ERR(task);
        rpc_put_task(task);
        return 0;
}
EXPORT_SYMBOL_GPL(rpc_call_async);

void
rpc_call_start(struct rpc_task *task)
{
        task->tk_action = call_start;
}
EXPORT_SYMBOL_GPL(rpc_call_start);

/**
 * rpc_peeraddr - extract remote peer address from clnt's xprt
 * @clnt: RPC client structure
 * @buf: target buffer
 * @bufsize: length of target buffer
 *
 * Returns the number of bytes that are actually in the stored address.
 */
size_t rpc_peeraddr(struct rpc_clnt *clnt, struct sockaddr *buf, size_t bufsize)
{
        size_t bytes;
        struct rpc_xprt *xprt = clnt->cl_xprt;

        bytes = sizeof(xprt->addr);
        if (bytes > bufsize)
                bytes = bufsize;
        memcpy(buf, &clnt->cl_xprt->addr, bytes);
        return xprt->addrlen;
}
EXPORT_SYMBOL_GPL(rpc_peeraddr);

/**
 * rpc_peeraddr2str - return remote peer address in printable format
 * @clnt: RPC client structure
 * @format: address format
 *
 */
const char *rpc_peeraddr2str(struct rpc_clnt *clnt,
                             enum rpc_display_format_t format)
{
        struct rpc_xprt *xprt = clnt->cl_xprt;

        if (xprt->address_strings[format] != NULL)
                return xprt->address_strings[format];
        else
                return "unprintable";
}
EXPORT_SYMBOL_GPL(rpc_peeraddr2str);

void
rpc_setbufsize(struct rpc_clnt *clnt, unsigned int sndsize, unsigned int rcvsize)
{
        struct rpc_xprt *xprt = clnt->cl_xprt;
        if (xprt->ops->set_buffer_size)
                xprt->ops->set_buffer_size(xprt, sndsize, rcvsize);
}
EXPORT_SYMBOL_GPL(rpc_setbufsize);

/*
 * Return size of largest payload RPC client can support, in bytes
 *
 * For stream transports, this is one RPC record fragment (see RFC
 * 1831), as we don't support multi-record requests yet.  For datagram
 * transports, this is the size of an IP packet minus the IP, UDP, and
 * RPC header sizes.
 */
size_t rpc_max_payload(struct rpc_clnt *clnt)
{
        return clnt->cl_xprt->max_payload;
}
EXPORT_SYMBOL_GPL(rpc_max_payload);

/**
 * rpc_force_rebind - force transport to check that remote port is unchanged
 * @clnt: client to rebind
 *
 */
void rpc_force_rebind(struct rpc_clnt *clnt)
{
        if (clnt->cl_autobind)
                xprt_clear_bound(clnt->cl_xprt);
}
EXPORT_SYMBOL_GPL(rpc_force_rebind);

/*
 * Restart an (async) RPC call. Usually called from within the
 * exit handler.
 */
void
rpc_restart_call(struct rpc_task *task)
{
        if (RPC_ASSASSINATED(task))
                return;

        task->tk_action = call_start;
}
EXPORT_SYMBOL_GPL(rpc_restart_call);

#ifdef RPC_DEBUG
static const char *rpc_proc_name(const struct rpc_task *task)
{
        const struct rpc_procinfo *proc = task->tk_msg.rpc_proc;

        if (proc) {
                if (proc->p_name)
                        return proc->p_name;
                else
                        return "NULL";
        } else
                return "no proc";
}
#endif

/*
 * 0.  Initial state
 *
 *     Other FSM states can be visited zero or more times, but
 *     this state is visited exactly once for each RPC.
 */
static void
call_start(struct rpc_task *task)
{
        struct rpc_clnt *clnt = task->tk_client;

        dprintk("RPC: %5u call_start %s%d proc %s (%s)\n", task->tk_pid,
                        clnt->cl_protname, clnt->cl_vers,
                        rpc_proc_name(task),
                        (RPC_IS_ASYNC(task) ? "async" : "sync"));

        /* Increment call count */
        task->tk_msg.rpc_proc->p_count++;
        clnt->cl_stats->rpccnt++;
        task->tk_action = call_reserve;
}

/*
 * 1.   Reserve an RPC call slot
 */
static void
call_reserve(struct rpc_task *task)
{
        dprint_status(task);

        if (!rpcauth_uptodatecred(task)) {
                task->tk_action = call_refresh;
                return;
        }

        task->tk_status  = 0;
        task->tk_action  = call_reserveresult;
        xprt_reserve(task);
}

/*
 * 1b.  Grok the result of xprt_reserve()
 */
static void
call_reserveresult(struct rpc_task *task)
{
        int status = task->tk_status;

        dprint_status(task);

        /*
         * After a call to xprt_reserve(), we must have either
         * a request slot or else an error status.
         */
        task->tk_status = 0;
        if (status >= 0) {
                if (task->tk_rqstp) {
                        task->tk_action = call_allocate;
                        return;
                }

                printk(KERN_ERR "%s: status=%d, but no request slot, exiting\n",
                                __func__, status);
                rpc_exit(task, -EIO);
                return;
        }

        /*
         * Even though there was an error, we may have acquired
         * a request slot somehow.  Make sure not to leak it.
         */
        if (task->tk_rqstp) {
                printk(KERN_ERR "%s: status=%d, request allocated anyway\n",
                                __func__, status);
                xprt_release(task);
        }

        switch (status) {
        case -EAGAIN:   /* woken up; retry */
                task->tk_action = call_reserve;
                return;
        case -EIO:      /* probably a shutdown */
                break;
        default:
                printk(KERN_ERR "%s: unrecognized error %d, exiting\n",
                                __func__, status);
                break;
        }
        rpc_exit(task, status);
}

/*
 * 2.   Allocate the buffer. For details, see sched.c:rpc_malloc.
 *      (Note: buffer memory is freed in xprt_release).
 */
static void
call_allocate(struct rpc_task *task)
{
        unsigned int slack = task->tk_msg.rpc_cred->cr_auth->au_cslack;
        struct rpc_rqst *req = task->tk_rqstp;
        struct rpc_xprt *xprt = task->tk_xprt;
        struct rpc_procinfo *proc = task->tk_msg.rpc_proc;

        dprint_status(task);

        task->tk_status = 0;
        task->tk_action = call_bind;

        if (req->rq_buffer)
                return;

        if (proc->p_proc != 0) {
                BUG_ON(proc->p_arglen == 0);
                if (proc->p_decode != NULL)
                        BUG_ON(proc->p_replen == 0);
        }

        /*
         * Calculate the size (in quads) of the RPC call
         * and reply headers, and convert both values
         * to byte sizes.
         */
        req->rq_callsize = RPC_CALLHDRSIZE + (slack << 1) + proc->p_arglen;
        req->rq_callsize <<= 2;
        req->rq_rcvsize = RPC_REPHDRSIZE + slack + proc->p_replen;
        req->rq_rcvsize <<= 2;

        req->rq_buffer = xprt->ops->buf_alloc(task,
                                        req->rq_callsize + req->rq_rcvsize);
        if (req->rq_buffer != NULL)
                return;

        dprintk("RPC: %5u rpc_buffer allocation failed\n", task->tk_pid);

        if (RPC_IS_ASYNC(task) || !signalled()) {
                task->tk_action = call_allocate;
                rpc_delay(task, HZ>>4);
                return;
        }

        rpc_exit(task, -ERESTARTSYS);
}

static inline int
rpc_task_need_encode(struct rpc_task *task)
{
        return task->tk_rqstp->rq_snd_buf.len == 0;
}

static inline void
rpc_task_force_reencode(struct rpc_task *task)
{
        task->tk_rqstp->rq_snd_buf.len = 0;
}

static inline void
rpc_xdr_buf_init(struct xdr_buf *buf, void *start, size_t len)
{
        buf->head[0].iov_base = start;
        buf->head[0].iov_len = len;
        buf->tail[0].iov_len = 0;
        buf->page_len = 0;
        buf->flags = 0;
        buf->len = 0;
        buf->buflen = len;
}

/*
 * 3.   Encode arguments of an RPC call
 */
static void
rpc_xdr_encode(struct rpc_task *task)
{
        struct rpc_rqst *req = task->tk_rqstp;
        kxdrproc_t      encode;
        __be32          *p;

        dprint_status(task);

        rpc_xdr_buf_init(&req->rq_snd_buf,
                         req->rq_buffer,
                         req->rq_callsize);
        rpc_xdr_buf_init(&req->rq_rcv_buf,
                         (char *)req->rq_buffer + req->rq_callsize,
                         req->rq_rcvsize);

        p = rpc_encode_header(task);
        if (p == NULL) {
                printk(KERN_INFO "RPC: couldn't encode RPC header, exit EIO\n");
                rpc_exit(task, -EIO);
                return;
        }

        encode = task->tk_msg.rpc_proc->p_encode;
        if (encode == NULL)
                return;

        task->tk_status = rpcauth_wrap_req(task, encode, req, p,
                        task->tk_msg.rpc_argp);
}

/*
 * 4.   Get the server port number if not yet set
 */
static void
call_bind(struct rpc_task *task)
{
        struct rpc_xprt *xprt = task->tk_xprt;

        dprint_status(task);

        task->tk_action = call_connect;
        if (!xprt_bound(xprt)) {
                task->tk_action = call_bind_status;
                task->tk_timeout = xprt->bind_timeout;
                xprt->ops->rpcbind(task);
        }
}

/*
 * 4a.  Sort out bind result
 */
static void
call_bind_status(struct rpc_task *task)
{
        int status = -EIO;

        if (task->tk_status >= 0) {
                dprint_status(task);
                task->tk_status = 0;
                task->tk_action = call_connect;
                return;
        }

        switch (task->tk_status) {
        case -ENOMEM:
                dprintk("RPC: %5u rpcbind out of memory\n", task->tk_pid);
                rpc_delay(task, HZ >> 2);
                goto retry_timeout;
        case -EACCES:
                dprintk("RPC: %5u remote rpcbind: RPC program/version "
                                "unavailable\n", task->tk_pid);
                /* fail immediately if this is an RPC ping */
                if (task->tk_msg.rpc_proc->p_proc == 0) {
                        status = -EOPNOTSUPP;
                        break;
                }
                rpc_delay(task, 3*HZ);
                goto retry_timeout;
        case -ETIMEDOUT:
                dprintk("RPC: %5u rpcbind request timed out\n",
                                task->tk_pid);
                goto retry_timeout;
        case -EPFNOSUPPORT:
                /* server doesn't support any rpcbind version we know of */
                dprintk("RPC: %5u remote rpcbind service unavailable\n",
                                task->tk_pid);
                break;
        case -EPROTONOSUPPORT:
                dprintk("RPC: %5u remote rpcbind version unavailable, retrying\n",
                                task->tk_pid);
                task->tk_status = 0;
                task->tk_action = call_bind;
                return;
        default:
                dprintk("RPC: %5u unrecognized rpcbind error (%d)\n",
                                task->tk_pid, -task->tk_status);
        }

        rpc_exit(task, status);
        return;

retry_timeout:
        task->tk_action = call_timeout;
}

/*
 * 4b.  Connect to the RPC server
 */
static void
call_connect(struct rpc_task *task)
{
        struct rpc_xprt *xprt = task->tk_xprt;

        dprintk("RPC: %5u call_connect xprt %p %s connected\n",
                        task->tk_pid, xprt,
                        (xprt_connected(xprt) ? "is" : "is not"));

        task->tk_action = call_transmit;
        if (!xprt_connected(xprt)) {
                task->tk_action = call_connect_status;
                if (task->tk_status < 0)
                        return;
                xprt_connect(task);
        }
}

/*
 * 4c.  Sort out connect result
 */
static void
call_connect_status(struct rpc_task *task)
{
        struct rpc_clnt *clnt = task->tk_client;
        int status = task->tk_status;

        dprint_status(task);

        task->tk_status = 0;
        if (status >= 0) {
                clnt->cl_stats->netreconn++;
                task->tk_action = call_transmit;
                return;
        }

        /* Something failed: remote service port may have changed */
        rpc_force_rebind(clnt);

        switch (status) {
        case -ENOTCONN:
        case -EAGAIN:
                task->tk_action = call_bind;
                if (!RPC_IS_SOFT(task))
                        return;
                /* if soft mounted, test if we've timed out */
        case -ETIMEDOUT:
                task->tk_action = call_timeout;
                return;
        }
        rpc_exit(task, -EIO);
}

/*
 * 5.   Transmit the RPC request, and wait for reply
 */
static void
call_transmit(struct rpc_task *task)
{
        dprint_status(task);

        task->tk_action = call_status;
        if (task->tk_status < 0)
                return;
        task->tk_status = xprt_prepare_transmit(task);
        if (task->tk_status != 0)
                return;
        task->tk_action = call_transmit_status;
        /* Encode here so that rpcsec_gss can use correct sequence number. */
        if (rpc_task_need_encode(task)) {
                BUG_ON(task->tk_rqstp->rq_bytes_sent != 0);
                rpc_xdr_encode(task);
                /* Did the encode result in an error condition? */
                if (task->tk_status != 0) {
                        /* Was the error nonfatal? */
                        if (task->tk_status == -EAGAIN)
                                rpc_delay(task, HZ >> 4);
                        else
                                rpc_exit(task, task->tk_status);
                        return;
                }
        }
        xprt_transmit(task);
        if (task->tk_status < 0)
                return;
        /*
         * On success, ensure that we call xprt_end_transmit() before sleeping
         * in order to allow access to the socket to other RPC requests.
         */
        call_transmit_status(task);
        if (task->tk_msg.rpc_proc->p_decode != NULL)
                return;
        task->tk_action = rpc_exit_task;
        rpc_wake_up_queued_task(&task->tk_xprt->pending, task);
}

/*
 * 5a.  Handle cleanup after a transmission
 */
static void
call_transmit_status(struct rpc_task *task)
{
        task->tk_action = call_status;
        /*
         * Special case: if we've been waiting on the socket's write_space()
         * callback, then don't call xprt_end_transmit().
         */
        if (task->tk_status == -EAGAIN)
                return;
        xprt_end_transmit(task);
        rpc_task_force_reencode(task);
}

/*
 * 6.   Sort out the RPC call status
 */
static void
call_status(struct rpc_task *task)
{
        struct rpc_clnt *clnt = task->tk_client;
        struct rpc_rqst *req = task->tk_rqstp;
        int             status;

        if (req->rq_received > 0 && !req->rq_bytes_sent)
                task->tk_status = req->rq_received;

        dprint_status(task);

        status = task->tk_status;
        if (status >= 0) {
                task->tk_action = call_decode;
                return;
        }

        task->tk_status = 0;
        switch(status) {
        case -EHOSTDOWN:
        case -EHOSTUNREACH:
        case -ENETUNREACH:
                /*
                 * Delay any retries for 3 seconds, then handle as if it
                 * were a timeout.
                 */
                rpc_delay(task, 3*HZ);
        case -ETIMEDOUT:
                task->tk_action = call_timeout;
                if (task->tk_client->cl_discrtry)
                        xprt_conditional_disconnect(task->tk_xprt,
                                        req->rq_connect_cookie);
                break;
        case -ECONNREFUSED:
        case -ENOTCONN:
                rpc_force_rebind(clnt);
                task->tk_action = call_bind;
                break;
        case -EAGAIN:
                task->tk_action = call_transmit;
                break;
        case -EIO:
                /* shutdown or soft timeout */
                rpc_exit(task, status);
                break;
        default:
                if (clnt->cl_chatty)
                        printk("%s: RPC call returned error %d\n",
                               clnt->cl_protname, -status);
                rpc_exit(task, status);
        }
}

/*
 * 6a.  Handle RPC timeout
 *      We do not release the request slot, so we keep using the
 *      same XID for all retransmits.
 */
static void
call_timeout(struct rpc_task *task)
{
        struct rpc_clnt *clnt = task->tk_client;

        if (xprt_adjust_timeout(task->tk_rqstp) == 0) {
                dprintk("RPC: %5u call_timeout (minor)\n", task->tk_pid);
                goto retry;
        }

        dprintk("RPC: %5u call_timeout (major)\n", task->tk_pid);
        task->tk_timeouts++;

        if (RPC_IS_SOFT(task)) {
                if (clnt->cl_chatty)
                        printk(KERN_NOTICE "%s: server %s not responding, timed out\n",
                                clnt->cl_protname, clnt->cl_server);
                rpc_exit(task, -EIO);
                return;
        }

        if (!(task->tk_flags & RPC_CALL_MAJORSEEN)) {
                task->tk_flags |= RPC_CALL_MAJORSEEN;
                if (clnt->cl_chatty)
                        printk(KERN_NOTICE "%s: server %s not responding, still trying\n",
                        clnt->cl_protname, clnt->cl_server);
        }
        rpc_force_rebind(clnt);
        /*
         * Did our request time out due to an RPCSEC_GSS out-of-sequence
         * event? RFC2203 requires the server to drop all such requests.
         */
        rpcauth_invalcred(task);

retry:
        clnt->cl_stats->rpcretrans++;
        task->tk_action = call_bind;
        task->tk_status = 0;
}

/*
 * 7.   Decode the RPC reply
 */
static void
call_decode(struct rpc_task *task)
{
        struct rpc_clnt *clnt = task->tk_client;
        struct rpc_rqst *req = task->tk_rqstp;
        kxdrproc_t      decode = task->tk_msg.rpc_proc->p_decode;
        __be32          *p;

        dprintk("RPC: %5u call_decode (status %d)\n",
                        task->tk_pid, task->tk_status);

        if (task->tk_flags & RPC_CALL_MAJORSEEN) {
                if (clnt->cl_chatty)
                        printk(KERN_NOTICE "%s: server %s OK\n",
                                clnt->cl_protname, clnt->cl_server);
                task->tk_flags &= ~RPC_CALL_MAJORSEEN;
        }

        /*
         * Ensure that we see all writes made by xprt_complete_rqst()
         * before it changed req->rq_received.
         */
        smp_rmb();
        req->rq_rcv_buf.len = req->rq_private_buf.len;

        /* Check that the softirq receive buffer is valid */
        WARN_ON(memcmp(&req->rq_rcv_buf, &req->rq_private_buf,
                                sizeof(req->rq_rcv_buf)) != 0);

        if (req->rq_rcv_buf.len < 12) {
                if (!RPC_IS_SOFT(task)) {
                        task->tk_action = call_bind;
                        clnt->cl_stats->rpcretrans++;
                        goto out_retry;
                }
                dprintk("RPC:       %s: too small RPC reply size (%d bytes)\n",
                                clnt->cl_protname, task->tk_status);
                task->tk_action = call_timeout;
                goto out_retry;
        }

        p = rpc_verify_header(task);
        if (IS_ERR(p)) {
                if (p == ERR_PTR(-EAGAIN))
                        goto out_retry;
                return;
        }

        task->tk_action = rpc_exit_task;

        if (decode) {
                task->tk_status = rpcauth_unwrap_resp(task, decode, req, p,
                                                      task->tk_msg.rpc_resp);
        }
        dprintk("RPC: %5u call_decode result %d\n", task->tk_pid,
                        task->tk_status);
        return;
out_retry:
        task->tk_status = 0;
        /* Note: rpc_verify_header() may have freed the RPC slot */
        if (task->tk_rqstp == req) {
                req->rq_received = req->rq_rcv_buf.len = 0;
                if (task->tk_client->cl_discrtry)
                        xprt_conditional_disconnect(task->tk_xprt,
                                        req->rq_connect_cookie);
        }
}

/*
 * 8.   Refresh the credentials if rejected by the server
 */
static void
call_refresh(struct rpc_task *task)
{
        dprint_status(task);

        task->tk_action = call_refreshresult;
        task->tk_status = 0;
        task->tk_client->cl_stats->rpcauthrefresh++;
        rpcauth_refreshcred(task);
}

/*
 * 8a.  Process the results of a credential refresh
 */
static void
call_refreshresult(struct rpc_task *task)
{
        int status = task->tk_status;

        dprint_status(task);

        task->tk_status = 0;
        task->tk_action = call_reserve;
        if (status >= 0 && rpcauth_uptodatecred(task))
                return;
        if (status == -EACCES) {
                rpc_exit(task, -EACCES);
                return;
        }
        task->tk_action = call_refresh;
        if (status != -ETIMEDOUT)
                rpc_delay(task, 3*HZ);
        return;
}

static __be32 *
rpc_encode_header(struct rpc_task *task)
{
        struct rpc_clnt *clnt = task->tk_client;
        struct rpc_rqst *req = task->tk_rqstp;
        __be32          *p = req->rq_svec[0].iov_base;

        /* FIXME: check buffer size? */

        p = xprt_skip_transport_header(task->tk_xprt, p);
        *p++ = req->rq_xid;             /* XID */
        *p++ = htonl(RPC_CALL);         /* CALL */
        *p++ = htonl(RPC_VERSION);      /* RPC version */
        *p++ = htonl(clnt->cl_prog);    /* program number */
        *p++ = htonl(clnt->cl_vers);    /* program version */
        *p++ = htonl(task->tk_msg.rpc_proc->p_proc);    /* procedure */
        p = rpcauth_marshcred(task, p);
        req->rq_slen = xdr_adjust_iovec(&req->rq_svec[0], p);
        return p;
}

static __be32 *
rpc_verify_header(struct rpc_task *task)
{
        struct kvec *iov = &task->tk_rqstp->rq_rcv_buf.head[0];
        int len = task->tk_rqstp->rq_rcv_buf.len >> 2;
        __be32  *p = iov->iov_base;
        u32 n;
        int error = -EACCES;

        if ((task->tk_rqstp->rq_rcv_buf.len & 3) != 0) {
                /* RFC-1014 says that the representation of XDR data must be a
                 * multiple of four bytes
                 * - if it isn't pointer subtraction in the NFS client may give
                 *   undefined results
                 */
                dprintk("RPC: %5u %s: XDR representation not a multiple of"
                       " 4 bytes: 0x%x\n", task->tk_pid, __func__,
                       task->tk_rqstp->rq_rcv_buf.len);
                goto out_eio;
        }
        if ((len -= 3) < 0)
                goto out_overflow;
        p += 1; /* skip XID */

        if ((n = ntohl(*p++)) != RPC_REPLY) {
                dprintk("RPC: %5u %s: not an RPC reply: %x\n",
                                task->tk_pid, __func__, n);
                goto out_garbage;
        }
        if ((n = ntohl(*p++)) != RPC_MSG_ACCEPTED) {
                if (--len < 0)
                        goto out_overflow;
                switch ((n = ntohl(*p++))) {
                        case RPC_AUTH_ERROR:
                                break;
                        case RPC_MISMATCH:
                                dprintk("RPC: %5u %s: RPC call version "
                                                "mismatch!\n",
                                                task->tk_pid, __func__);
                                error = -EPROTONOSUPPORT;
                                goto out_err;
                        default:
                                dprintk("RPC: %5u %s: RPC call rejected, "
                                                "unknown error: %x\n",
                                                task->tk_pid, __func__, n);
                                goto out_eio;
                }
                if (--len < 0)
                        goto out_overflow;
                switch ((n = ntohl(*p++))) {
                case RPC_AUTH_REJECTEDCRED:
                case RPC_AUTH_REJECTEDVERF:
                case RPCSEC_GSS_CREDPROBLEM:
                case RPCSEC_GSS_CTXPROBLEM:
                        if (!task->tk_cred_retry)
                                break;
                        task->tk_cred_retry--;
                        dprintk("RPC: %5u %s: retry stale creds\n",
                                        task->tk_pid, __func__);
                        rpcauth_invalcred(task);
                        /* Ensure we obtain a new XID! */
                        xprt_release(task);
                        task->tk_action = call_refresh;
                        goto out_retry;
                case RPC_AUTH_BADCRED:
                case RPC_AUTH_BADVERF:
                        /* possibly garbled cred/verf? */
                        if (!task->tk_garb_retry)
                                break;
                        task->tk_garb_retry--;
                        dprintk("RPC: %5u %s: retry garbled creds\n",
                                        task->tk_pid, __func__);
                        task->tk_action = call_bind;
                        goto out_retry;
                case RPC_AUTH_TOOWEAK:
                        printk(KERN_NOTICE "RPC: server %s requires stronger "
                               "authentication.\n", task->tk_client->cl_server);
                        break;
                default:
                        dprintk("RPC: %5u %s: unknown auth error: %x\n",
                                        task->tk_pid, __func__, n);
                        error = -EIO;
                }
                dprintk("RPC: %5u %s: call rejected %d\n",
                                task->tk_pid, __func__, n);
                goto out_err;
        }
        if (!(p = rpcauth_checkverf(task, p))) {
                dprintk("RPC: %5u %s: auth check failed\n",
                                task->tk_pid, __func__);
                goto out_garbage;               /* bad verifier, retry */
        }
        len = p - (__be32 *)iov->iov_base - 1;
        if (len < 0)
                goto out_overflow;
        switch ((n = ntohl(*p++))) {
        case RPC_SUCCESS:
                return p;
        case RPC_PROG_UNAVAIL:
                dprintk("RPC: %5u %s: program %u is unsupported by server %s\n",
                                task->tk_pid, __func__,
                                (unsigned int)task->tk_client->cl_prog,
                                task->tk_client->cl_server);
                error = -EPFNOSUPPORT;
                goto out_err;
        case RPC_PROG_MISMATCH:
                dprintk("RPC: %5u %s: program %u, version %u unsupported by "
                                "server %s\n", task->tk_pid, __func__,
                                (unsigned int)task->tk_client->cl_prog,
                                (unsigned int)task->tk_client->cl_vers,
                                task->tk_client->cl_server);
                error = -EPROTONOSUPPORT;
                goto out_err;
        case RPC_PROC_UNAVAIL:
                dprintk("RPC: %5u %s: proc %s unsupported by program %u, "
                                "version %u on server %s\n",
                                task->tk_pid, __func__,
                                rpc_proc_name(task),
                                task->tk_client->cl_prog,
                                task->tk_client->cl_vers,
                                task->tk_client->cl_server);
                error = -EOPNOTSUPP;
                goto out_err;
        case RPC_GARBAGE_ARGS:
                dprintk("RPC: %5u %s: server saw garbage\n",
                                task->tk_pid, __func__);
                break;                  /* retry */
        default:
                dprintk("RPC: %5u %s: server accept status: %x\n",
                                task->tk_pid, __func__, n);
                /* Also retry */
        }

out_garbage:
        task->tk_client->cl_stats->rpcgarbage++;
        if (task->tk_garb_retry) {
                task->tk_garb_retry--;
                dprintk("RPC: %5u %s: retrying\n",
                                task->tk_pid, __func__);
                task->tk_action = call_bind;
out_retry:
                return ERR_PTR(-EAGAIN);
        }
out_eio:
        error = -EIO;
out_err:
        rpc_exit(task, error);
        dprintk("RPC: %5u %s: call failed with error %d\n", task->tk_pid,
                        __func__, error);
        return ERR_PTR(error);
out_overflow:
        dprintk("RPC: %5u %s: server reply was truncated.\n", task->tk_pid,
                        __func__);
        goto out_garbage;
}

static int rpcproc_encode_null(void *rqstp, __be32 *data, void *obj)
{
        return 0;
}

static int rpcproc_decode_null(void *rqstp, __be32 *data, void *obj)
{
        return 0;
}

static struct rpc_procinfo rpcproc_null = {
        .p_encode = rpcproc_encode_null,
        .p_decode = rpcproc_decode_null,
};

static int rpc_ping(struct rpc_clnt *clnt, int flags)
{
        struct rpc_message msg = {
                .rpc_proc = &rpcproc_null,
        };
        int err;
        msg.rpc_cred = authnull_ops.lookup_cred(NULL, NULL, 0);
        err = rpc_call_sync(clnt, &msg, flags);
        put_rpccred(msg.rpc_cred);
        return err;
}

struct rpc_task *rpc_call_null(struct rpc_clnt *clnt, struct rpc_cred *cred, int flags)
{
        struct rpc_message msg = {
                .rpc_proc = &rpcproc_null,
                .rpc_cred = cred,
        };
        struct rpc_task_setup task_setup_data = {
                .rpc_client = clnt,
                .rpc_message = &msg,
                .callback_ops = &rpc_default_ops,
                .flags = flags,
        };
        return rpc_run_task(&task_setup_data);
}
EXPORT_SYMBOL_GPL(rpc_call_null);

#ifdef RPC_DEBUG
static void rpc_show_header(void)
{
        printk(KERN_INFO "-pid- flgs status -client- --rqstp- "
                "-timeout ---ops--\n");
}

static void rpc_show_task(const struct rpc_clnt *clnt,
                          const struct rpc_task *task)
{
        const char *rpc_waitq = "none";
        char *p, action[KSYM_SYMBOL_LEN];

        if (RPC_IS_QUEUED(task))
                rpc_waitq = rpc_qname(task->tk_waitqueue);

        /* map tk_action pointer to a function name; then trim off
         * the "+0x0 [sunrpc]" */
        sprint_symbol(action, (unsigned long)task->tk_action);
        p = strchr(action, '+');
        if (p)
                *p = '\0';

        printk(KERN_INFO "%5u %04x %6d %8p %8p %8ld %8p %sv%u %s a:%s q:%s\n",
                task->tk_pid, task->tk_flags, task->tk_status,
                clnt, task->tk_rqstp, task->tk_timeout, task->tk_ops,
                clnt->cl_protname, clnt->cl_vers, rpc_proc_name(task),
                action, rpc_waitq);
}

void rpc_show_tasks(void)
{
        struct rpc_clnt *clnt;
        struct rpc_task *task;
        int header = 0;

        spin_lock(&rpc_client_lock);
        list_for_each_entry(clnt, &all_clients, cl_clients) {
                spin_lock(&clnt->cl_lock);
                list_for_each_entry(task, &clnt->cl_tasks, tk_task) {
                        if (!header) {
                                rpc_show_header();
                                header++;
                        }
                        rpc_show_task(clnt, task);
                }
                spin_unlock(&clnt->cl_lock);
        }
        spin_unlock(&rpc_client_lock);
}
#endif