// SPDX-License-Identifier: GPL-2.0-only
/*
 * linux/net/sunrpc/svc_xprt.c
 *
 * Author: Tom Tucker <tom@opengridcomputing.com>
 */

#include <linux/sched.h>
#include <linux/sched/mm.h>
#include <linux/errno.h>
#include <linux/freezer.h>
#include <linux/slab.h>
#include <net/sock.h>
#include <linux/sunrpc/addr.h>
#include <linux/sunrpc/stats.h>
#include <linux/sunrpc/svc_xprt.h>
#include <linux/sunrpc/svcsock.h>
#include <linux/sunrpc/xprt.h>
#include <linux/sunrpc/bc_xprt.h>
#include <linux/module.h>
#include <linux/netdevice.h>
#include <trace/events/sunrpc.h>

#define RPCDBG_FACILITY RPCDBG_SVCXPRT

static unsigned int svc_rpc_per_connection_limit __read_mostly;
module_param(svc_rpc_per_connection_limit, uint, 0644);


static struct svc_deferred_req *svc_deferred_dequeue(struct svc_xprt *xprt);
static int svc_deferred_recv(struct svc_rqst *rqstp);
static struct cache_deferred_req *svc_defer(struct cache_req *req);
static void svc_age_temp_xprts(struct timer_list *t);
static void svc_delete_xprt(struct svc_xprt *xprt);

/* apparently the "standard" is that clients close
 * idle connections after 5 minutes, servers after
 * 6 minutes
 *   http://nfsv4bat.org/Documents/ConnectAThon/1996/nfstcp.pdf
 */
static int svc_conn_age_period = 6*60;

/* List of registered transport classes */
static DEFINE_SPINLOCK(svc_xprt_class_lock);
static LIST_HEAD(svc_xprt_class_list);

/* SMP locking strategy:
 *
 *      svc_serv->sv_lock protects sv_tempsocks, sv_permsocks, sv_tmpcnt.
 *      when both need to be taken (rare), svc_serv->sv_lock is first.
 *      The "service mutex" protects svc_serv->sv_nrthread.
 *      svc_sock->sk_lock protects the svc_sock->sk_deferred list
 *             and the ->sk_info_authunix cache.
 *
 *      The XPT_BUSY bit in xprt->xpt_flags prevents a transport being
 *      enqueued multiply. During normal transport processing this bit
 *      is set by svc_xprt_enqueue and cleared by svc_xprt_received.
 *      Providers should not manipulate this bit directly.
 *
 *      Some flags can be set to certain values at any time
 *      providing that certain rules are followed:
 *
 *      XPT_CONN, XPT_DATA:
 *              - Can be set or cleared at any time.
 *              - After a set, svc_xprt_enqueue must be called to enqueue
 *                the transport for processing.
 *              - After a clear, the transport must be read/accepted.
 *                If this succeeds, it must be set again.
 *      XPT_CLOSE:
 *              - Can set at any time. It is never cleared.
 *      XPT_DEAD:
 *              - Can only be set while XPT_BUSY is held which ensures
 *                that no other thread will be using the transport or will
 *                try to set XPT_DEAD.
 */

/**
 * svc_reg_xprt_class - Register a server-side RPC transport class
 * @xcl: New transport class to be registered
 *
 * Returns zero on success; otherwise a negative errno is returned.
 */
int svc_reg_xprt_class(struct svc_xprt_class *xcl)
{
        struct svc_xprt_class *cl;
        int res = -EEXIST;

        INIT_LIST_HEAD(&xcl->xcl_list);
        spin_lock(&svc_xprt_class_lock);
        /* Make sure there isn't already a class with the same name */
        list_for_each_entry(cl, &svc_xprt_class_list, xcl_list) {
                if (strcmp(xcl->xcl_name, cl->xcl_name) == 0)
                        goto out;
        }
        list_add_tail(&xcl->xcl_list, &svc_xprt_class_list);
        res = 0;
out:
        spin_unlock(&svc_xprt_class_lock);
        return res;
}
EXPORT_SYMBOL_GPL(svc_reg_xprt_class);

/**
 * svc_unreg_xprt_class - Unregister a server-side RPC transport class
 * @xcl: Transport class to be unregistered
 *
 */
void svc_unreg_xprt_class(struct svc_xprt_class *xcl)
{
        spin_lock(&svc_xprt_class_lock);
        list_del_init(&xcl->xcl_list);
        spin_unlock(&svc_xprt_class_lock);
}
EXPORT_SYMBOL_GPL(svc_unreg_xprt_class);

/**
 * svc_print_xprts - Format the transport list for printing
 * @buf: target buffer for formatted address
 * @maxlen: length of target buffer
 *
 * Fills in @buf with a string containing a list of transport names, each name
 * terminated with '\n'. If the buffer is too small, some entries may be
 * missing, but it is guaranteed that all lines in the output buffer are
 * complete.
 *
 * Returns positive length of the filled-in string.
 */
int svc_print_xprts(char *buf, int maxlen)
{
        struct svc_xprt_class *xcl;
        char tmpstr[80];
        int len = 0;
        buf[0] = '\0';

        spin_lock(&svc_xprt_class_lock);
        list_for_each_entry(xcl, &svc_xprt_class_list, xcl_list) {
                int slen;

                slen = snprintf(tmpstr, sizeof(tmpstr), "%s %d\n",
                                xcl->xcl_name, xcl->xcl_max_payload);
                if (slen >= sizeof(tmpstr) || len + slen >= maxlen)
                        break;
                len += slen;
                strcat(buf, tmpstr);
        }
        spin_unlock(&svc_xprt_class_lock);

        return len;
}

/**
 * svc_xprt_deferred_close - Close a transport
 * @xprt: transport instance
 *
 * Used in contexts that need to defer the work of shutting down
 * the transport to an nfsd thread.
 */
void svc_xprt_deferred_close(struct svc_xprt *xprt)
{
        trace_svc_xprt_close(xprt);
        if (!test_and_set_bit(XPT_CLOSE, &xprt->xpt_flags))
                svc_xprt_enqueue(xprt);
}
EXPORT_SYMBOL_GPL(svc_xprt_deferred_close);

static void svc_xprt_free(struct kref *kref)
{
        struct svc_xprt *xprt =
                container_of(kref, struct svc_xprt, xpt_ref);
        struct module *owner = xprt->xpt_class->xcl_owner;
        if (test_bit(XPT_CACHE_AUTH, &xprt->xpt_flags))
                svcauth_unix_info_release(xprt);
        put_cred(xprt->xpt_cred);
        put_net_track(xprt->xpt_net, &xprt->ns_tracker);
        /* See comment on corresponding get in xs_setup_bc_tcp(): */
        if (xprt->xpt_bc_xprt)
                xprt_put(xprt->xpt_bc_xprt);
        if (xprt->xpt_bc_xps)
                xprt_switch_put(xprt->xpt_bc_xps);
        trace_svc_xprt_free(xprt);
        xprt->xpt_ops->xpo_free(xprt);
        module_put(owner);
}

void svc_xprt_put(struct svc_xprt *xprt)
{
        kref_put(&xprt->xpt_ref, svc_xprt_free);
}
EXPORT_SYMBOL_GPL(svc_xprt_put);

/*
 * Called by transport drivers to initialize the transport independent
 * portion of the transport instance.
 */
void svc_xprt_init(struct net *net, struct svc_xprt_class *xcl,
                   struct svc_xprt *xprt, struct svc_serv *serv)
{
        memset(xprt, 0, sizeof(*xprt));
        xprt->xpt_class = xcl;
        xprt->xpt_ops = xcl->xcl_ops;
        kref_init(&xprt->xpt_ref);
        xprt->xpt_server = serv;
        INIT_LIST_HEAD(&xprt->xpt_list);
        INIT_LIST_HEAD(&xprt->xpt_deferred);
        INIT_LIST_HEAD(&xprt->xpt_users);
        mutex_init(&xprt->xpt_mutex);
        spin_lock_init(&xprt->xpt_lock);
        set_bit(XPT_BUSY, &xprt->xpt_flags);
        xprt->xpt_net = get_net_track(net, &xprt->ns_tracker, GFP_ATOMIC);
        strcpy(xprt->xpt_remotebuf, "uninitialized");
}
EXPORT_SYMBOL_GPL(svc_xprt_init);

/**
 * svc_xprt_received - start next receiver thread
 * @xprt: controlling transport
 *
 * The caller must hold the XPT_BUSY bit and must
 * not thereafter touch transport data.
 *
 * Note: XPT_DATA only gets cleared when a read-attempt finds no (or
 * insufficient) data.
 */
void svc_xprt_received(struct svc_xprt *xprt)
{
        if (!test_bit(XPT_BUSY, &xprt->xpt_flags)) {
                WARN_ONCE(1, "xprt=0x%p already busy!", xprt);
                return;
        }

        /* As soon as we clear busy, the xprt could be closed and
         * 'put', so we need a reference to call svc_xprt_enqueue with:
         */
        svc_xprt_get(xprt);
        smp_mb__before_atomic();
        clear_bit(XPT_BUSY, &xprt->xpt_flags);
        svc_xprt_enqueue(xprt);
        svc_xprt_put(xprt);
}
EXPORT_SYMBOL_GPL(svc_xprt_received);

void svc_add_new_perm_xprt(struct svc_serv *serv, struct svc_xprt *new)
{
        clear_bit(XPT_TEMP, &new->xpt_flags);
        spin_lock_bh(&serv->sv_lock);
        list_add(&new->xpt_list, &serv->sv_permsocks);
        spin_unlock_bh(&serv->sv_lock);
        svc_xprt_received(new);
}

static int _svc_xprt_create(struct svc_serv *serv, const char *xprt_name,
                            struct net *net, struct sockaddr *sap,
                            size_t len, int flags, const struct cred *cred)
{
        struct svc_xprt_class *xcl;

        spin_lock(&svc_xprt_class_lock);
        list_for_each_entry(xcl, &svc_xprt_class_list, xcl_list) {
                struct svc_xprt *newxprt;
                unsigned short newport;

                if (strcmp(xprt_name, xcl->xcl_name))
                        continue;

                if (!try_module_get(xcl->xcl_owner))
                        goto err;

                spin_unlock(&svc_xprt_class_lock);
                newxprt = xcl->xcl_ops->xpo_create(serv, net, sap, len, flags);
                if (IS_ERR(newxprt)) {
                        trace_svc_xprt_create_err(serv->sv_programs->pg_name,
                                                  xcl->xcl_name, sap, len,
                                                  newxprt);
                        module_put(xcl->xcl_owner);
                        return PTR_ERR(newxprt);
                }
                newxprt->xpt_cred = get_cred(cred);
                svc_add_new_perm_xprt(serv, newxprt);
                newport = svc_xprt_local_port(newxprt);
                return newport;
        }
 err:
        spin_unlock(&svc_xprt_class_lock);
        /* This errno is exposed to user space.  Provide a reasonable
         * perror msg for a bad transport. */
        return -EPROTONOSUPPORT;
}

/**
 * svc_xprt_create_from_sa - Add a new listener to @serv from socket address
 * @serv: target RPC service
 * @xprt_name: transport class name
 * @net: network namespace
 * @sap: socket address pointer
 * @flags: SVC_SOCK flags
 * @cred: credential to bind to this transport
 *
 * Return local xprt port on success or %-EPROTONOSUPPORT on failure
 */
int svc_xprt_create_from_sa(struct svc_serv *serv, const char *xprt_name,
                            struct net *net, struct sockaddr *sap,
                            int flags, const struct cred *cred)
{
        size_t len;
        int err;

        switch (sap->sa_family) {
        case AF_INET:
                len = sizeof(struct sockaddr_in);
                break;
#if IS_ENABLED(CONFIG_IPV6)
        case AF_INET6:
                len = sizeof(struct sockaddr_in6);
                break;
#endif
        default:
                return -EAFNOSUPPORT;
        }

        err = _svc_xprt_create(serv, xprt_name, net, sap, len, flags, cred);
        if (err == -EPROTONOSUPPORT) {
                request_module("svc%s", xprt_name);
                err = _svc_xprt_create(serv, xprt_name, net, sap, len, flags,
                                       cred);
        }

        return err;
}
EXPORT_SYMBOL_GPL(svc_xprt_create_from_sa);

/**
 * svc_xprt_create - Add a new listener to @serv
 * @serv: target RPC service
 * @xprt_name: transport class name
 * @net: network namespace
 * @family: network address family
 * @port: listener port
 * @flags: SVC_SOCK flags
 * @cred: credential to bind to this transport
 *
 * Return local xprt port on success or %-EPROTONOSUPPORT on failure
 */
int svc_xprt_create(struct svc_serv *serv, const char *xprt_name,
                    struct net *net, const int family,
                    const unsigned short port, int flags,
                    const struct cred *cred)
{
        struct sockaddr_in sin = {
                .sin_family             = AF_INET,
                .sin_addr.s_addr        = htonl(INADDR_ANY),
                .sin_port               = htons(port),
        };
#if IS_ENABLED(CONFIG_IPV6)
        struct sockaddr_in6 sin6 = {
                .sin6_family            = AF_INET6,
                .sin6_addr              = IN6ADDR_ANY_INIT,
                .sin6_port              = htons(port),
        };
#endif
        struct sockaddr *sap;

        switch (family) {
        case PF_INET:
                sap = (struct sockaddr *)&sin;
                break;
#if IS_ENABLED(CONFIG_IPV6)
        case PF_INET6:
                sap = (struct sockaddr *)&sin6;
                break;
#endif
        default:
                return -EAFNOSUPPORT;
        }

        return svc_xprt_create_from_sa(serv, xprt_name, net, sap, flags, cred);
}
EXPORT_SYMBOL_GPL(svc_xprt_create);

/*
 * Copy the local and remote xprt addresses to the rqstp structure
 */
void svc_xprt_copy_addrs(struct svc_rqst *rqstp, struct svc_xprt *xprt)
{
        memcpy(&rqstp->rq_addr, &xprt->xpt_remote, xprt->xpt_remotelen);
        rqstp->rq_addrlen = xprt->xpt_remotelen;

        /*
         * Destination address in request is needed for binding the
         * source address in RPC replies/callbacks later.
         */
        memcpy(&rqstp->rq_daddr, &xprt->xpt_local, xprt->xpt_locallen);
        rqstp->rq_daddrlen = xprt->xpt_locallen;
}
EXPORT_SYMBOL_GPL(svc_xprt_copy_addrs);

/**
 * svc_print_addr - Format rq_addr field for printing
 * @rqstp: svc_rqst struct containing address to print
 * @buf: target buffer for formatted address
 * @len: length of target buffer
 *
 */
char *svc_print_addr(struct svc_rqst *rqstp, char *buf, size_t len)
{
        return __svc_print_addr(svc_addr(rqstp), buf, len);
}
EXPORT_SYMBOL_GPL(svc_print_addr);

static bool svc_xprt_slots_in_range(struct svc_xprt *xprt)
{
        unsigned int limit = svc_rpc_per_connection_limit;
        int nrqsts = atomic_read(&xprt->xpt_nr_rqsts);

        return limit == 0 || (nrqsts >= 0 && nrqsts < limit);
}

static bool svc_xprt_reserve_slot(struct svc_rqst *rqstp, struct svc_xprt *xprt)
{
        if (!test_bit(RQ_DATA, &rqstp->rq_flags)) {
                if (!svc_xprt_slots_in_range(xprt))
                        return false;
                atomic_inc(&xprt->xpt_nr_rqsts);
                set_bit(RQ_DATA, &rqstp->rq_flags);
        }
        return true;
}

static void svc_xprt_release_slot(struct svc_rqst *rqstp)
{
        struct svc_xprt *xprt = rqstp->rq_xprt;
        if (test_and_clear_bit(RQ_DATA, &rqstp->rq_flags)) {
                atomic_dec(&xprt->xpt_nr_rqsts);
                smp_wmb(); /* See smp_rmb() in svc_xprt_ready() */
                svc_xprt_enqueue(xprt);
        }
}

static bool svc_xprt_ready(struct svc_xprt *xprt)
{
        unsigned long xpt_flags;

        /*
         * If another cpu has recently updated xpt_flags,
         * sk_sock->flags, xpt_reserved, or xpt_nr_rqsts, we need to
         * know about it; otherwise it's possible that both that cpu and
         * this one could call svc_xprt_enqueue() without either
         * svc_xprt_enqueue() recognizing that the conditions below
         * are satisfied, and we could stall indefinitely:
         */
        smp_rmb();
        xpt_flags = READ_ONCE(xprt->xpt_flags);

        trace_svc_xprt_enqueue(xprt, xpt_flags);
        if (xpt_flags & BIT(XPT_BUSY))
                return false;
        if (xpt_flags & (BIT(XPT_CONN) | BIT(XPT_CLOSE) | BIT(XPT_HANDSHAKE)))
                return true;
        if (xpt_flags & (BIT(XPT_DATA) | BIT(XPT_DEFERRED))) {
                if (xprt->xpt_ops->xpo_has_wspace(xprt) &&
                    svc_xprt_slots_in_range(xprt))
                        return true;
                trace_svc_xprt_no_write_space(xprt);
                return false;
        }
        return false;
}

/**
 * svc_xprt_enqueue - Queue a transport on an idle nfsd thread
 * @xprt: transport with data pending
 *
 */
void svc_xprt_enqueue(struct svc_xprt *xprt)
{
        struct svc_pool *pool;

        if (!svc_xprt_ready(xprt))
                return;

        /* Mark transport as busy. It will remain in this state until
         * the provider calls svc_xprt_received. We update XPT_BUSY
         * atomically because it also guards against trying to enqueue
         * the transport twice.
         */
        if (test_and_set_bit(XPT_BUSY, &xprt->xpt_flags))
                return;

        pool = svc_pool_for_cpu(xprt->xpt_server);

        percpu_counter_inc(&pool->sp_sockets_queued);
        xprt->xpt_qtime = ktime_get();
        lwq_enqueue(&xprt->xpt_ready, &pool->sp_xprts);

        svc_pool_wake_idle_thread(pool);
}
EXPORT_SYMBOL_GPL(svc_xprt_enqueue);

/*
 * Dequeue the first transport, if there is one.
 */
static struct svc_xprt *svc_xprt_dequeue(struct svc_pool *pool)
{
        struct svc_xprt *xprt = NULL;

        xprt = lwq_dequeue(&pool->sp_xprts, struct svc_xprt, xpt_ready);
        if (xprt)
                svc_xprt_get(xprt);
        return xprt;
}

/**
 * svc_reserve - change the space reserved for the reply to a request.
 * @rqstp:  The request in question
 * @space: new max space to reserve
 *
 * Each request reserves some space on the output queue of the transport
 * to make sure the reply fits.  This function reduces that reserved
 * space to be the amount of space used already, plus @space.
 *
 */
void svc_reserve(struct svc_rqst *rqstp, int space)
{
        struct svc_xprt *xprt = rqstp->rq_xprt;

        space += rqstp->rq_res.head[0].iov_len;

        if (xprt && space < rqstp->rq_reserved) {
                atomic_sub((rqstp->rq_reserved - space), &xprt->xpt_reserved);
                rqstp->rq_reserved = space;
                smp_wmb(); /* See smp_rmb() in svc_xprt_ready() */
                svc_xprt_enqueue(xprt);
        }
}
EXPORT_SYMBOL_GPL(svc_reserve);

static void free_deferred(struct svc_xprt *xprt, struct svc_deferred_req *dr)
{
        if (!dr)
                return;

        xprt->xpt_ops->xpo_release_ctxt(xprt, dr->xprt_ctxt);
        kfree(dr);
}

static void svc_xprt_release(struct svc_rqst *rqstp)
{
        struct svc_xprt *xprt = rqstp->rq_xprt;

        xprt->xpt_ops->xpo_release_ctxt(xprt, rqstp->rq_xprt_ctxt);
        rqstp->rq_xprt_ctxt = NULL;

        free_deferred(xprt, rqstp->rq_deferred);
        rqstp->rq_deferred = NULL;

        svc_rqst_release_pages(rqstp);
        rqstp->rq_res.page_len = 0;
        rqstp->rq_res.page_base = 0;

        /* Reset response buffer and release
         * the reservation.
         * But first, check that enough space was reserved
         * for the reply, otherwise we have a bug!
         */
        if ((rqstp->rq_res.len) >  rqstp->rq_reserved)
                printk(KERN_ERR "RPC request reserved %d but used %d\n",
                       rqstp->rq_reserved,
                       rqstp->rq_res.len);

        rqstp->rq_res.head[0].iov_len = 0;
        svc_reserve(rqstp, 0);
        svc_xprt_release_slot(rqstp);
        rqstp->rq_xprt = NULL;
        svc_xprt_put(xprt);
}

/**
 * svc_wake_up - Wake up a service thread for non-transport work
 * @serv: RPC service
 *
 * Some svc_serv's will have occasional work to do, even when a xprt is not
 * waiting to be serviced. This function is there to "kick" a task in one of
 * those services so that it can wake up and do that work. Note that we only
 * bother with pool 0 as we don't need to wake up more than one thread for
 * this purpose.
 */
void svc_wake_up(struct svc_serv *serv)
{
        struct svc_pool *pool = &serv->sv_pools[0];

        set_bit(SP_TASK_PENDING, &pool->sp_flags);
        svc_pool_wake_idle_thread(pool);
}
EXPORT_SYMBOL_GPL(svc_wake_up);

int svc_port_is_privileged(struct sockaddr *sin)
{
        switch (sin->sa_family) {
        case AF_INET:
                return ntohs(((struct sockaddr_in *)sin)->sin_port)
                        < PROT_SOCK;
        case AF_INET6:
                return ntohs(((struct sockaddr_in6 *)sin)->sin6_port)
                        < PROT_SOCK;
        default:
                return 0;
        }
}

/*
 * Make sure that we don't have too many connections that have not yet
 * demonstrated that they have access to the NFS server. If we have,
 * something must be dropped. It's not clear what will happen if we allow
 * "too many" connections, but when dealing with network-facing software,
 * we have to code defensively. Here we do that by imposing hard limits.
 *
 * There's no point in trying to do random drop here for DoS
 * prevention. The NFS clients does 1 reconnect in 15 seconds. An
 * attacker can easily beat that.
 *
 * The only somewhat efficient mechanism would be if drop old
 * connections from the same IP first. But right now we don't even
 * record the client IP in svc_sock.
 */
static void svc_check_conn_limits(struct svc_serv *serv)
{
        if (serv->sv_tmpcnt > XPT_MAX_TMP_CONN) {
                struct svc_xprt *xprt = NULL, *xprti;
                spin_lock_bh(&serv->sv_lock);
                if (!list_empty(&serv->sv_tempsocks)) {
                        /*
                         * Always select the oldest connection. It's not fair,
                         * but nor is life.
                         */
                        list_for_each_entry_reverse(xprti, &serv->sv_tempsocks,
                                                    xpt_list) {
                                if (!test_bit(XPT_PEER_VALID, &xprti->xpt_flags)) {
                                        xprt = xprti;
                                        set_bit(XPT_CLOSE, &xprt->xpt_flags);
                                        svc_xprt_get(xprt);
                                        break;
                                }
                        }
                }
                spin_unlock_bh(&serv->sv_lock);

                if (xprt) {
                        svc_xprt_enqueue(xprt);
                        svc_xprt_put(xprt);
                }
        }
}

static bool svc_alloc_arg(struct svc_rqst *rqstp)
{
        struct xdr_buf *arg = &rqstp->rq_arg;
        unsigned long pages, filled, ret;

        pages = rqstp->rq_maxpages;
        for (filled = 0; filled < pages; filled = ret) {
                ret = alloc_pages_bulk(GFP_KERNEL, pages, rqstp->rq_pages);
                if (ret > filled)
                        /* Made progress, don't sleep yet */
                        continue;

                set_current_state(TASK_IDLE);
                if (svc_thread_should_stop(rqstp)) {
                        set_current_state(TASK_RUNNING);
                        return false;
                }
                trace_svc_alloc_arg_err(pages, ret);
                memalloc_retry_wait(GFP_KERNEL);
        }
        rqstp->rq_page_end = &rqstp->rq_pages[pages];
        rqstp->rq_pages[pages] = NULL; /* this might be seen in nfsd_splice_actor() */

        /* Make arg->head point to first page and arg->pages point to rest */
        arg->head[0].iov_base = page_address(rqstp->rq_pages[0]);
        arg->head[0].iov_len = PAGE_SIZE;
        arg->pages = rqstp->rq_pages + 1;
        arg->page_base = 0;
        /* save at least one page for response */
        arg->page_len = (pages-2)*PAGE_SIZE;
        arg->len = (pages-1)*PAGE_SIZE;
        arg->tail[0].iov_len = 0;

        rqstp->rq_xid = xdr_zero;
        return true;
}

static bool
svc_thread_should_sleep(struct svc_rqst *rqstp)
{
        struct svc_pool         *pool = rqstp->rq_pool;

        /* did someone call svc_wake_up? */
        if (test_bit(SP_TASK_PENDING, &pool->sp_flags))
                return false;

        /* was a socket queued? */
        if (!lwq_empty(&pool->sp_xprts))
                return false;

        /* are we shutting down? */
        if (svc_thread_should_stop(rqstp))
                return false;

#if defined(CONFIG_SUNRPC_BACKCHANNEL)
        if (svc_is_backchannel(rqstp)) {
                if (!lwq_empty(&rqstp->rq_server->sv_cb_list))
                        return false;
        }
#endif

        return true;
}

static bool svc_schedule_timeout(long timeo)
{
        return schedule_timeout(timeo ? timeo : MAX_SCHEDULE_TIMEOUT) == 0;
}

static bool svc_thread_wait_for_work(struct svc_rqst *rqstp, long timeo)
{
        struct svc_pool *pool = rqstp->rq_pool;
        bool did_timeout = false;

        if (svc_thread_should_sleep(rqstp)) {
                set_current_state(TASK_IDLE | TASK_FREEZABLE);
                llist_add(&rqstp->rq_idle, &pool->sp_idle_threads);
                if (likely(svc_thread_should_sleep(rqstp)))
                        did_timeout = svc_schedule_timeout(timeo);

                while (!llist_del_first_this(&pool->sp_idle_threads,
                                             &rqstp->rq_idle)) {
                        /* Work just became available.  This thread can only
                         * handle it after removing rqstp from the idle
                         * list. If that attempt failed, some other thread
                         * must have queued itself after finding no
                         * work to do, so that thread has taken responsibly
                         * for this new work.  This thread can safely sleep
                         * until woken again.
                         */
                        did_timeout = svc_schedule_timeout(timeo);
                        set_current_state(TASK_IDLE | TASK_FREEZABLE);
                }
                __set_current_state(TASK_RUNNING);
        } else {
                cond_resched();
        }
        try_to_freeze();
        return did_timeout;
}

static void svc_add_new_temp_xprt(struct svc_serv *serv, struct svc_xprt *newxpt)
{
        spin_lock_bh(&serv->sv_lock);
        set_bit(XPT_TEMP, &newxpt->xpt_flags);
        list_add(&newxpt->xpt_list, &serv->sv_tempsocks);
        serv->sv_tmpcnt++;
        if (serv->sv_temptimer.function == NULL) {
                /* setup timer to age temp transports */
                serv->sv_temptimer.function = svc_age_temp_xprts;
                mod_timer(&serv->sv_temptimer,
                          jiffies + svc_conn_age_period * HZ);
        }
        spin_unlock_bh(&serv->sv_lock);
        svc_xprt_received(newxpt);
}

static void svc_handle_xprt(struct svc_rqst *rqstp, struct svc_xprt *xprt)
{
        struct svc_serv *serv = rqstp->rq_server;
        int len = 0;

        if (test_bit(XPT_CLOSE, &xprt->xpt_flags)) {
                if (test_and_clear_bit(XPT_KILL_TEMP, &xprt->xpt_flags))
                        xprt->xpt_ops->xpo_kill_temp_xprt(xprt);
                svc_delete_xprt(xprt);
                /* Leave XPT_BUSY set on the dead xprt: */
                goto out;
        }
        if (test_bit(XPT_LISTENER, &xprt->xpt_flags)) {
                struct svc_xprt *newxpt;
                /*
                 * We know this module_get will succeed because the
                 * listener holds a reference too
                 */
                __module_get(xprt->xpt_class->xcl_owner);
                svc_check_conn_limits(xprt->xpt_server);
                newxpt = xprt->xpt_ops->xpo_accept(xprt);
                if (newxpt) {
                        newxpt->xpt_cred = get_cred(xprt->xpt_cred);
                        svc_add_new_temp_xprt(serv, newxpt);
                        trace_svc_xprt_accept(newxpt, serv->sv_name);
                } else {
                        module_put(xprt->xpt_class->xcl_owner);
                }
                svc_xprt_received(xprt);
        } else if (test_bit(XPT_HANDSHAKE, &xprt->xpt_flags)) {
                xprt->xpt_ops->xpo_handshake(xprt);
                svc_xprt_received(xprt);
        } else if (svc_xprt_reserve_slot(rqstp, xprt)) {
                /* XPT_DATA|XPT_DEFERRED case: */
                rqstp->rq_deferred = svc_deferred_dequeue(xprt);
                if (rqstp->rq_deferred)
                        len = svc_deferred_recv(rqstp);
                else
                        len = xprt->xpt_ops->xpo_recvfrom(rqstp);
                rqstp->rq_reserved = serv->sv_max_mesg;
                atomic_add(rqstp->rq_reserved, &xprt->xpt_reserved);
                if (len <= 0)
                        goto out;

                trace_svc_xdr_recvfrom(&rqstp->rq_arg);

                clear_bit(XPT_OLD, &xprt->xpt_flags);

                rqstp->rq_chandle.defer = svc_defer;

                if (serv->sv_stats)
                        serv->sv_stats->netcnt++;
                percpu_counter_inc(&rqstp->rq_pool->sp_messages_arrived);
                rqstp->rq_stime = ktime_get();
                svc_process(rqstp);
        } else
                svc_xprt_received(xprt);

out:
        rqstp->rq_res.len = 0;
        svc_xprt_release(rqstp);
}

static void svc_thread_wake_next(struct svc_rqst *rqstp)
{
        if (!svc_thread_should_sleep(rqstp))
                /* More work pending after I dequeued some,
                 * wake another worker
                 */
                svc_pool_wake_idle_thread(rqstp->rq_pool);
}

/**
 * svc_recv - Receive and process the next request on any transport
 * @rqstp: an idle RPC service thread
 * @timeo: timeout (in jiffies) (0 means infinite timeout)
 *
 * This code is carefully organised not to touch any cachelines in
 * the shared svc_serv structure, only cachelines in the local
 * svc_pool.
 *
 * If the timeout is 0, then the sleep will never time out.
 *
 * Returns -ETIMEDOUT if idle for an extended period
 *         -EBUSY if there is more work to do than available threads
 *         0 otherwise.
 */
int svc_recv(struct svc_rqst *rqstp, long timeo)
{
        struct svc_pool *pool = rqstp->rq_pool;
        bool did_timeout;
        int ret = 0;

        if (!svc_alloc_arg(rqstp))
                return ret;

        did_timeout = svc_thread_wait_for_work(rqstp, timeo);

        if (did_timeout && svc_thread_should_sleep(rqstp) &&
            pool->sp_nrthrmin && pool->sp_nrthreads > pool->sp_nrthrmin)
                ret = -ETIMEDOUT;

        clear_bit(SP_TASK_PENDING, &pool->sp_flags);

        if (svc_thread_should_stop(rqstp)) {
                svc_thread_wake_next(rqstp);
                return ret;
        }

        rqstp->rq_xprt = svc_xprt_dequeue(pool);
        if (rqstp->rq_xprt) {
                struct svc_xprt *xprt = rqstp->rq_xprt;

                svc_thread_wake_next(rqstp);
                /* Normally we will wait up to 5 seconds for any required
                 * cache information to be provided.  When there are no
                 * idle threads, we reduce the wait time.
                 */
                if (pool->sp_idle_threads.first) {
                        rqstp->rq_chandle.thread_wait = 5 * HZ;
                } else {
                        rqstp->rq_chandle.thread_wait = 1 * HZ;
                        /*
                         * No idle threads: signal -EBUSY so the caller
                         * can consider spawning another thread. Use
                         * SP_TASK_STARTING to limit this signal to one
                         * thread at a time; the caller clears this flag
                         * after starting a new thread.
                         */
                        if (!did_timeout && timeo &&
                            !test_and_set_bit(SP_TASK_STARTING,
                                              &pool->sp_flags))
                                ret = -EBUSY;
                }

                trace_svc_xprt_dequeue(rqstp);
                svc_handle_xprt(rqstp, xprt);
        }

#if defined(CONFIG_SUNRPC_BACKCHANNEL)
        if (svc_is_backchannel(rqstp)) {
                struct svc_serv *serv = rqstp->rq_server;
                struct rpc_rqst *req;

                req = lwq_dequeue(&serv->sv_cb_list,
                                  struct rpc_rqst, rq_bc_list);
                if (req) {
                        svc_thread_wake_next(rqstp);
                        svc_process_bc(req, rqstp);
                }
        }
#endif
        return ret;
}
EXPORT_SYMBOL_GPL(svc_recv);

/**
 * svc_send - Return reply to client
 * @rqstp: RPC transaction context
 *
 */
void svc_send(struct svc_rqst *rqstp)
{
        struct svc_xprt *xprt;
        struct xdr_buf  *xb;
        int status;

        xprt = rqstp->rq_xprt;

        /* calculate over-all length */
        xb = &rqstp->rq_res;
        xb->len = xb->head[0].iov_len +
                xb->page_len +
                xb->tail[0].iov_len;
        trace_svc_xdr_sendto(rqstp->rq_xid, xb);
        trace_svc_stats_latency(rqstp);

        status = xprt->xpt_ops->xpo_sendto(rqstp);

        trace_svc_send(rqstp, status);
}

/*
 * Timer function to close old temporary transports, using
 * a mark-and-sweep algorithm.
 */
static void svc_age_temp_xprts(struct timer_list *t)
{
        struct svc_serv *serv = timer_container_of(serv, t, sv_temptimer);
        struct svc_xprt *xprt;
        struct list_head *le, *next;

        dprintk("svc_age_temp_xprts\n");

        if (!spin_trylock_bh(&serv->sv_lock)) {
                /* busy, try again 1 sec later */
                dprintk("svc_age_temp_xprts: busy\n");
                mod_timer(&serv->sv_temptimer, jiffies + HZ);
                return;
        }

        list_for_each_safe(le, next, &serv->sv_tempsocks) {
                xprt = list_entry(le, struct svc_xprt, xpt_list);

                /* First time through, just mark it OLD. Second time
                 * through, close it. */
                if (!test_and_set_bit(XPT_OLD, &xprt->xpt_flags))
                        continue;
                if (kref_read(&xprt->xpt_ref) > 1 ||
                    test_bit(XPT_BUSY, &xprt->xpt_flags))
                        continue;
                list_del_init(le);
                set_bit(XPT_CLOSE, &xprt->xpt_flags);
                dprintk("queuing xprt %p for closing\n", xprt);

                /* a thread will dequeue and close it soon */
                svc_xprt_enqueue(xprt);
        }
        spin_unlock_bh(&serv->sv_lock);

        mod_timer(&serv->sv_temptimer, jiffies + svc_conn_age_period * HZ);
}

/* Close temporary transports whose xpt_local matches server_addr immediately
 * instead of waiting for them to be picked up by the timer.
 *
 * This is meant to be called from a notifier_block that runs when an ip
 * address is deleted.
 */
void svc_age_temp_xprts_now(struct svc_serv *serv, struct sockaddr *server_addr)
{
        struct svc_xprt *xprt;
        struct list_head *le, *next;
        LIST_HEAD(to_be_closed);

        spin_lock_bh(&serv->sv_lock);
        list_for_each_safe(le, next, &serv->sv_tempsocks) {
                xprt = list_entry(le, struct svc_xprt, xpt_list);
                if (rpc_cmp_addr(server_addr, (struct sockaddr *)
                                &xprt->xpt_local)) {
                        dprintk("svc_age_temp_xprts_now: found %p\n", xprt);
                        list_move(le, &to_be_closed);
                }
        }
        spin_unlock_bh(&serv->sv_lock);

        while (!list_empty(&to_be_closed)) {
                le = to_be_closed.next;
                list_del_init(le);
                xprt = list_entry(le, struct svc_xprt, xpt_list);
                set_bit(XPT_CLOSE, &xprt->xpt_flags);
                set_bit(XPT_KILL_TEMP, &xprt->xpt_flags);
                dprintk("svc_age_temp_xprts_now: queuing xprt %p for closing\n",
                                xprt);
                svc_xprt_enqueue(xprt);
        }
}
EXPORT_SYMBOL_GPL(svc_age_temp_xprts_now);

static void call_xpt_users(struct svc_xprt *xprt)
{
        struct svc_xpt_user *u;

        spin_lock(&xprt->xpt_lock);
        while (!list_empty(&xprt->xpt_users)) {
                u = list_first_entry(&xprt->xpt_users, struct svc_xpt_user, list);
                list_del_init(&u->list);
                u->callback(u);
        }
        spin_unlock(&xprt->xpt_lock);
}

/*
 * Remove a dead transport
 */
static void svc_delete_xprt(struct svc_xprt *xprt)
{
        struct svc_serv *serv = xprt->xpt_server;
        struct svc_deferred_req *dr;

        /* unregister with rpcbind for when transport type is TCP or UDP.
         */
        if (test_bit(XPT_RPCB_UNREG, &xprt->xpt_flags)) {
                struct svc_sock *svsk = container_of(xprt, struct svc_sock,
                                                     sk_xprt);
                struct socket *sock = svsk->sk_sock;

                if (svc_register(serv, xprt->xpt_net, sock->sk->sk_family,
                                 sock->sk->sk_protocol, 0) < 0)
                        pr_warn("failed to unregister %s with rpcbind\n",
                                xprt->xpt_class->xcl_name);
        }

        if (test_and_set_bit(XPT_DEAD, &xprt->xpt_flags))
                return;

        trace_svc_xprt_detach(xprt);
        xprt->xpt_ops->xpo_detach(xprt);
        if (xprt->xpt_bc_xprt)
                xprt->xpt_bc_xprt->ops->close(xprt->xpt_bc_xprt);

        spin_lock_bh(&serv->sv_lock);
        list_del_init(&xprt->xpt_list);
        if (test_bit(XPT_TEMP, &xprt->xpt_flags) &&
            !test_bit(XPT_PEER_VALID, &xprt->xpt_flags))
                serv->sv_tmpcnt--;
        spin_unlock_bh(&serv->sv_lock);

        while ((dr = svc_deferred_dequeue(xprt)) != NULL)
                free_deferred(xprt, dr);

        call_xpt_users(xprt);
        svc_xprt_put(xprt);
}

/**
 * svc_xprt_close - Close a client connection
 * @xprt: transport to disconnect
 *
 */
void svc_xprt_close(struct svc_xprt *xprt)
{
        trace_svc_xprt_close(xprt);
        set_bit(XPT_CLOSE, &xprt->xpt_flags);
        if (test_and_set_bit(XPT_BUSY, &xprt->xpt_flags))
                /* someone else will have to effect the close */
                return;
        /*
         * We expect svc_close_xprt() to work even when no threads are
         * running (e.g., while configuring the server before starting
         * any threads), so if the transport isn't busy, we delete
         * it ourself:
         */
        svc_delete_xprt(xprt);
}
EXPORT_SYMBOL_GPL(svc_xprt_close);

static int svc_close_list(struct svc_serv *serv, struct list_head *xprt_list, struct net *net)
{
        struct svc_xprt *xprt;
        int ret = 0;

        spin_lock_bh(&serv->sv_lock);
        list_for_each_entry(xprt, xprt_list, xpt_list) {
                if (xprt->xpt_net != net)
                        continue;
                ret++;
                set_bit(XPT_CLOSE, &xprt->xpt_flags);
                svc_xprt_enqueue(xprt);
        }
        spin_unlock_bh(&serv->sv_lock);
        return ret;
}

static void svc_clean_up_xprts(struct svc_serv *serv, struct net *net)
{
        struct svc_xprt *xprt;
        int i;

        for (i = 0; i < serv->sv_nrpools; i++) {
                struct svc_pool *pool = &serv->sv_pools[i];
                struct llist_node *q, **t1, *t2;

                q = lwq_dequeue_all(&pool->sp_xprts);
                lwq_for_each_safe(xprt, t1, t2, &q, xpt_ready) {
                        if (xprt->xpt_net == net) {
                                set_bit(XPT_CLOSE, &xprt->xpt_flags);
                                svc_delete_xprt(xprt);
                                xprt = NULL;
                        }
                }

                if (q)
                        lwq_enqueue_batch(q, &pool->sp_xprts);
        }
}

/**
 * svc_xprt_destroy_all - Destroy transports associated with @serv
 * @serv: RPC service to be shut down
 * @net: target network namespace
 * @unregister: true if it is OK to unregister the destroyed xprts
 *
 * Server threads may still be running (especially in the case where the
 * service is still running in other network namespaces).
 *
 * So we shut down sockets the same way we would on a running server, by
 * setting XPT_CLOSE, enqueuing, and letting a thread pick it up to do
 * the close.  In the case there are no such other threads,
 * threads running, svc_clean_up_xprts() does a simple version of a
 * server's main event loop, and in the case where there are other
 * threads, we may need to wait a little while and then check again to
 * see if they're done.
 */
void svc_xprt_destroy_all(struct svc_serv *serv, struct net *net,
                          bool unregister)
{
        int delay = 0;

        while (svc_close_list(serv, &serv->sv_permsocks, net) +
               svc_close_list(serv, &serv->sv_tempsocks, net)) {

                svc_clean_up_xprts(serv, net);
                msleep(delay++);
        }

        if (unregister)
                svc_rpcb_cleanup(serv, net);
}
EXPORT_SYMBOL_GPL(svc_xprt_destroy_all);

/*
 * Handle defer and revisit of requests
 */

static void svc_revisit(struct cache_deferred_req *dreq, int too_many)
{
        struct svc_deferred_req *dr =
                container_of(dreq, struct svc_deferred_req, handle);
        struct svc_xprt *xprt = dr->xprt;

        spin_lock(&xprt->xpt_lock);
        set_bit(XPT_DEFERRED, &xprt->xpt_flags);
        if (too_many || test_bit(XPT_DEAD, &xprt->xpt_flags)) {
                spin_unlock(&xprt->xpt_lock);
                trace_svc_defer_drop(dr);
                free_deferred(xprt, dr);
                svc_xprt_put(xprt);
                return;
        }
        dr->xprt = NULL;
        list_add(&dr->handle.recent, &xprt->xpt_deferred);
        spin_unlock(&xprt->xpt_lock);
        trace_svc_defer_queue(dr);
        svc_xprt_enqueue(xprt);
        svc_xprt_put(xprt);
}

/*
 * Save the request off for later processing. The request buffer looks
 * like this:
 *
 * <xprt-header><rpc-header><rpc-pagelist><rpc-tail>
 *
 * This code can only handle requests that consist of an xprt-header
 * and rpc-header.
 */
static struct cache_deferred_req *svc_defer(struct cache_req *req)
{
        struct svc_rqst *rqstp = container_of(req, struct svc_rqst, rq_chandle);
        struct svc_deferred_req *dr;

        if (rqstp->rq_arg.page_len || !test_bit(RQ_USEDEFERRAL, &rqstp->rq_flags))
                return NULL; /* if more than a page, give up FIXME */
        if (rqstp->rq_deferred) {
                dr = rqstp->rq_deferred;
                rqstp->rq_deferred = NULL;
        } else {
                size_t skip;
                size_t size;
                /* FIXME maybe discard if size too large */
                size = sizeof(struct svc_deferred_req) + rqstp->rq_arg.len;
                dr = kmalloc(size, GFP_KERNEL);
                if (dr == NULL)
                        return NULL;

                dr->handle.owner = rqstp->rq_server;
                dr->prot = rqstp->rq_prot;
                memcpy(&dr->addr, &rqstp->rq_addr, rqstp->rq_addrlen);
                dr->addrlen = rqstp->rq_addrlen;
                dr->daddr = rqstp->rq_daddr;
                dr->argslen = rqstp->rq_arg.len >> 2;

                /* back up head to the start of the buffer and copy */
                skip = rqstp->rq_arg.len - rqstp->rq_arg.head[0].iov_len;
                memcpy(dr->args, rqstp->rq_arg.head[0].iov_base - skip,
                       dr->argslen << 2);
        }
        dr->xprt_ctxt = rqstp->rq_xprt_ctxt;
        rqstp->rq_xprt_ctxt = NULL;
        trace_svc_defer(rqstp);
        svc_xprt_get(rqstp->rq_xprt);
        dr->xprt = rqstp->rq_xprt;
        set_bit(RQ_DROPME, &rqstp->rq_flags);

        dr->handle.revisit = svc_revisit;
        return &dr->handle;
}

/*
 * recv data from a deferred request into an active one
 */
static noinline int svc_deferred_recv(struct svc_rqst *rqstp)
{
        struct svc_deferred_req *dr = rqstp->rq_deferred;

        trace_svc_defer_recv(dr);

        /* setup iov_base past transport header */
        rqstp->rq_arg.head[0].iov_base = dr->args;
        /* The iov_len does not include the transport header bytes */
        rqstp->rq_arg.head[0].iov_len = dr->argslen << 2;
        rqstp->rq_arg.page_len = 0;
        /* The rq_arg.len includes the transport header bytes */
        rqstp->rq_arg.len     = dr->argslen << 2;
        rqstp->rq_prot        = dr->prot;
        memcpy(&rqstp->rq_addr, &dr->addr, dr->addrlen);
        rqstp->rq_addrlen     = dr->addrlen;
        /* Save off transport header len in case we get deferred again */
        rqstp->rq_daddr       = dr->daddr;
        rqstp->rq_respages    = rqstp->rq_pages;
        rqstp->rq_xprt_ctxt   = dr->xprt_ctxt;

        dr->xprt_ctxt = NULL;
        svc_xprt_received(rqstp->rq_xprt);
        return dr->argslen << 2;
}


static struct svc_deferred_req *svc_deferred_dequeue(struct svc_xprt *xprt)
{
        struct svc_deferred_req *dr = NULL;

        if (!test_bit(XPT_DEFERRED, &xprt->xpt_flags))
                return NULL;
        spin_lock(&xprt->xpt_lock);
        if (!list_empty(&xprt->xpt_deferred)) {
                dr = list_entry(xprt->xpt_deferred.next,
                                struct svc_deferred_req,
                                handle.recent);
                list_del_init(&dr->handle.recent);
        } else
                clear_bit(XPT_DEFERRED, &xprt->xpt_flags);
        spin_unlock(&xprt->xpt_lock);
        return dr;
}

/**
 * svc_find_listener - find an RPC transport instance
 * @serv: pointer to svc_serv to search
 * @xcl_name: C string containing transport's class name
 * @net: owner net pointer
 * @sa: sockaddr containing address
 *
 * Return the transport instance pointer for the endpoint accepting
 * connections/peer traffic from the specified transport class,
 * and matching sockaddr.
 */
struct svc_xprt *svc_find_listener(struct svc_serv *serv, const char *xcl_name,
                                   struct net *net, const struct sockaddr *sa)
{
        struct svc_xprt *xprt;
        struct svc_xprt *found = NULL;

        spin_lock_bh(&serv->sv_lock);
        list_for_each_entry(xprt, &serv->sv_permsocks, xpt_list) {
                if (xprt->xpt_net != net)
                        continue;
                if (strcmp(xprt->xpt_class->xcl_name, xcl_name))
                        continue;
                if (!rpc_cmp_addr_port(sa, (struct sockaddr *)&xprt->xpt_local))
                        continue;
                found = xprt;
                svc_xprt_get(xprt);
                break;
        }
        spin_unlock_bh(&serv->sv_lock);
        return found;
}
EXPORT_SYMBOL_GPL(svc_find_listener);

/**
 * svc_find_xprt - find an RPC transport instance
 * @serv: pointer to svc_serv to search
 * @xcl_name: C string containing transport's class name
 * @net: owner net pointer
 * @af: Address family of transport's local address
 * @port: transport's IP port number
 *
 * Return the transport instance pointer for the endpoint accepting
 * connections/peer traffic from the specified transport class,
 * address family and port.
 *
 * Specifying 0 for the address family or port is effectively a
 * wild-card, and will result in matching the first transport in the
 * service's list that has a matching class name.
 */
struct svc_xprt *svc_find_xprt(struct svc_serv *serv, const char *xcl_name,
                               struct net *net, const sa_family_t af,
                               const unsigned short port)
{
        struct svc_xprt *xprt;
        struct svc_xprt *found = NULL;

        /* Sanity check the args */
        if (serv == NULL || xcl_name == NULL)
                return found;

        spin_lock_bh(&serv->sv_lock);
        list_for_each_entry(xprt, &serv->sv_permsocks, xpt_list) {
                if (xprt->xpt_net != net)
                        continue;
                if (strcmp(xprt->xpt_class->xcl_name, xcl_name))
                        continue;
                if (af != AF_UNSPEC && af != xprt->xpt_local.ss_family)
                        continue;
                if (port != 0 && port != svc_xprt_local_port(xprt))
                        continue;
                found = xprt;
                svc_xprt_get(xprt);
                break;
        }
        spin_unlock_bh(&serv->sv_lock);
        return found;
}
EXPORT_SYMBOL_GPL(svc_find_xprt);

static int svc_one_xprt_name(const struct svc_xprt *xprt,
                             char *pos, int remaining)
{
        int len;

        len = snprintf(pos, remaining, "%s %u\n",
                        xprt->xpt_class->xcl_name,
                        svc_xprt_local_port(xprt));
        if (len >= remaining)
                return -ENAMETOOLONG;
        return len;
}

/**
 * svc_xprt_names - format a buffer with a list of transport names
 * @serv: pointer to an RPC service
 * @buf: pointer to a buffer to be filled in
 * @buflen: length of buffer to be filled in
 *
 * Fills in @buf with a string containing a list of transport names,
 * each name terminated with '\n'.
 *
 * Returns positive length of the filled-in string on success; otherwise
 * a negative errno value is returned if an error occurs.
 */
int svc_xprt_names(struct svc_serv *serv, char *buf, const int buflen)
{
        struct svc_xprt *xprt;
        int len, totlen;
        char *pos;

        /* Sanity check args */
        if (!serv)
                return 0;

        spin_lock_bh(&serv->sv_lock);

        pos = buf;
        totlen = 0;
        list_for_each_entry(xprt, &serv->sv_permsocks, xpt_list) {
                len = svc_one_xprt_name(xprt, pos, buflen - totlen);
                if (len < 0) {
                        *buf = '\0';
                        totlen = len;
                }
                if (len <= 0)
                        break;

                pos += len;
                totlen += len;
        }

        spin_unlock_bh(&serv->sv_lock);
        return totlen;
}
EXPORT_SYMBOL_GPL(svc_xprt_names);

/*----------------------------------------------------------------------------*/

static void *svc_pool_stats_start(struct seq_file *m, loff_t *pos)
{
        unsigned int pidx = (unsigned int)*pos;
        struct svc_info *si = m->private;

        dprintk("svc_pool_stats_start, *pidx=%u\n", pidx);

        mutex_lock(si->mutex);

        if (!pidx)
                return SEQ_START_TOKEN;
        if (!si->serv)
                return NULL;
        return pidx > si->serv->sv_nrpools ? NULL
                : &si->serv->sv_pools[pidx - 1];
}

static void *svc_pool_stats_next(struct seq_file *m, void *p, loff_t *pos)
{
        struct svc_pool *pool = p;
        struct svc_info *si = m->private;
        struct svc_serv *serv = si->serv;

        dprintk("svc_pool_stats_next, *pos=%llu\n", *pos);

        if (!serv) {
                pool = NULL;
        } else if (p == SEQ_START_TOKEN) {
                pool = &serv->sv_pools[0];
        } else {
                unsigned int pidx = (pool - &serv->sv_pools[0]);
                if (pidx < serv->sv_nrpools-1)
                        pool = &serv->sv_pools[pidx+1];
                else
                        pool = NULL;
        }
        ++*pos;
        return pool;
}

static void svc_pool_stats_stop(struct seq_file *m, void *p)
{
        struct svc_info *si = m->private;

        mutex_unlock(si->mutex);
}

static int svc_pool_stats_show(struct seq_file *m, void *p)
{
        struct svc_pool *pool = p;

        if (p == SEQ_START_TOKEN) {
                seq_puts(m, "# pool packets-arrived sockets-enqueued threads-woken threads-timedout\n");
                return 0;
        }

        seq_printf(m, "%u %llu %llu %llu 0\n",
                   pool->sp_id,
                   percpu_counter_sum_positive(&pool->sp_messages_arrived),
                   percpu_counter_sum_positive(&pool->sp_sockets_queued),
                   percpu_counter_sum_positive(&pool->sp_threads_woken));

        return 0;
}

static const struct seq_operations svc_pool_stats_seq_ops = {
        .start  = svc_pool_stats_start,
        .next   = svc_pool_stats_next,
        .stop   = svc_pool_stats_stop,
        .show   = svc_pool_stats_show,
};

int svc_pool_stats_open(struct svc_info *info, struct file *file)
{
        struct seq_file *seq;
        int err;

        err = seq_open(file, &svc_pool_stats_seq_ops);
        if (err)
                return err;
        seq = file->private_data;
        seq->private = info;

        return 0;
}
EXPORT_SYMBOL(svc_pool_stats_open);

/*----------------------------------------------------------------------------*/