// SPDX-License-Identifier: GPL-2.0
/*
 * Central processing for nfsd.
 *
 * Authors:     Olaf Kirch (okir@monad.swb.de)
 *
 * Copyright (C) 1995, 1996, 1997 Olaf Kirch <okir@monad.swb.de>
 */

#include <linux/sched/signal.h>
#include <linux/freezer.h>
#include <linux/module.h>
#include <linux/fs_struct.h>
#include <linux/swap.h>
#include <linux/siphash.h>

#include <linux/sunrpc/stats.h>
#include <linux/sunrpc/svcsock.h>
#include <linux/sunrpc/svc_xprt.h>
#include <linux/lockd/bind.h>
#include <linux/nfsacl.h>
#include <linux/seq_file.h>
#include <linux/inetdevice.h>
#include <net/addrconf.h>
#include <net/ipv6.h>
#include <net/net_namespace.h>
#include "nfsd.h"
#include "cache.h"
#include "vfs.h"
#include "netns.h"
#include "filecache.h"

#include "trace.h"

#define NFSDDBG_FACILITY        NFSDDBG_SVC

extern struct svc_program       nfsd_program;
static int                      nfsd(void *vrqstp);
#if defined(CONFIG_NFSD_V2_ACL) || defined(CONFIG_NFSD_V3_ACL)
static int                      nfsd_acl_rpcbind_set(struct net *,
                                                     const struct svc_program *,
                                                     u32, int,
                                                     unsigned short,
                                                     unsigned short);
static __be32                   nfsd_acl_init_request(struct svc_rqst *,
                                                const struct svc_program *,
                                                struct svc_process_info *);
#endif
static int                      nfsd_rpcbind_set(struct net *,
                                                 const struct svc_program *,
                                                 u32, int,
                                                 unsigned short,
                                                 unsigned short);
static __be32                   nfsd_init_request(struct svc_rqst *,
                                                const struct svc_program *,
                                                struct svc_process_info *);

/*
 * nfsd_mutex protects nn->nfsd_serv -- both the pointer itself and some members
 * of the svc_serv struct such as ->sv_temp_socks and ->sv_permsocks.
 *
 * If (out side the lock) nn->nfsd_serv is non-NULL, then it must point to a
 * properly initialised 'struct svc_serv' with ->sv_nrthreads > 0 (unless
 * nn->keep_active is set).  That number of nfsd threads must
 * exist and each must be listed in ->sp_all_threads in some entry of
 * ->sv_pools[].
 *
 * Each active thread holds a counted reference on nn->nfsd_serv, as does
 * the nn->keep_active flag and various transient calls to svc_get().
 *
 * Finally, the nfsd_mutex also protects some of the global variables that are
 * accessed when nfsd starts and that are settable via the write_* routines in
 * nfsctl.c. In particular:
 *
 *      user_recovery_dirname
 *      user_lease_time
 *      nfsd_versions
 */
DEFINE_MUTEX(nfsd_mutex);

/*
 * nfsd_drc_lock protects nfsd_drc_max_pages and nfsd_drc_pages_used.
 * nfsd_drc_max_pages limits the total amount of memory available for
 * version 4.1 DRC caches.
 * nfsd_drc_pages_used tracks the current version 4.1 DRC memory usage.
 */
DEFINE_SPINLOCK(nfsd_drc_lock);
unsigned long   nfsd_drc_max_mem;
unsigned long   nfsd_drc_mem_used;

#if defined(CONFIG_NFSD_V2_ACL) || defined(CONFIG_NFSD_V3_ACL)
static struct svc_stat  nfsd_acl_svcstats;
static const struct svc_version *nfsd_acl_version[] = {
        [2] = &nfsd_acl_version2,
        [3] = &nfsd_acl_version3,
};

#define NFSD_ACL_MINVERS            2
#define NFSD_ACL_NRVERS         ARRAY_SIZE(nfsd_acl_version)

static struct svc_program       nfsd_acl_program = {
        .pg_prog                = NFS_ACL_PROGRAM,
        .pg_nvers               = NFSD_ACL_NRVERS,
        .pg_vers                = nfsd_acl_version,
        .pg_name                = "nfsacl",
        .pg_class               = "nfsd",
        .pg_stats               = &nfsd_acl_svcstats,
        .pg_authenticate        = &svc_set_client,
        .pg_init_request        = nfsd_acl_init_request,
        .pg_rpcbind_set         = nfsd_acl_rpcbind_set,
};

static struct svc_stat  nfsd_acl_svcstats = {
        .program        = &nfsd_acl_program,
};
#endif /* defined(CONFIG_NFSD_V2_ACL) || defined(CONFIG_NFSD_V3_ACL) */

static const struct svc_version *nfsd_version[] = {
        [2] = &nfsd_version2,
        [3] = &nfsd_version3,
#if defined(CONFIG_NFSD_V4)
        [4] = &nfsd_version4,
#endif
};

#define NFSD_MINVERS            2
#define NFSD_NRVERS             ARRAY_SIZE(nfsd_version)

struct svc_program              nfsd_program = {
#if defined(CONFIG_NFSD_V2_ACL) || defined(CONFIG_NFSD_V3_ACL)
        .pg_next                = &nfsd_acl_program,
#endif
        .pg_prog                = NFS_PROGRAM,          /* program number */
        .pg_nvers               = NFSD_NRVERS,          /* nr of entries in nfsd_version */
        .pg_vers                = nfsd_version,         /* version table */
        .pg_name                = "nfsd",               /* program name */
        .pg_class               = "nfsd",               /* authentication class */
        .pg_stats               = &nfsd_svcstats,       /* version table */
        .pg_authenticate        = &svc_set_client,      /* export authentication */
        .pg_init_request        = nfsd_init_request,
        .pg_rpcbind_set         = nfsd_rpcbind_set,
};

static bool
nfsd_support_version(int vers)
{
        if (vers >= NFSD_MINVERS && vers < NFSD_NRVERS)
                return nfsd_version[vers] != NULL;
        return false;
}

static bool *
nfsd_alloc_versions(void)
{
        bool *vers = kmalloc_array(NFSD_NRVERS, sizeof(bool), GFP_KERNEL);
        unsigned i;

        if (vers) {
                /* All compiled versions are enabled by default */
                for (i = 0; i < NFSD_NRVERS; i++)
                        vers[i] = nfsd_support_version(i);
        }
        return vers;
}

static bool *
nfsd_alloc_minorversions(void)
{
        bool *vers = kmalloc_array(NFSD_SUPPORTED_MINOR_VERSION + 1,
                        sizeof(bool), GFP_KERNEL);
        unsigned i;

        if (vers) {
                /* All minor versions are enabled by default */
                for (i = 0; i <= NFSD_SUPPORTED_MINOR_VERSION; i++)
                        vers[i] = nfsd_support_version(4);
        }
        return vers;
}

void
nfsd_netns_free_versions(struct nfsd_net *nn)
{
        kfree(nn->nfsd_versions);
        kfree(nn->nfsd4_minorversions);
        nn->nfsd_versions = NULL;
        nn->nfsd4_minorversions = NULL;
}

static void
nfsd_netns_init_versions(struct nfsd_net *nn)
{
        if (!nn->nfsd_versions) {
                nn->nfsd_versions = nfsd_alloc_versions();
                nn->nfsd4_minorversions = nfsd_alloc_minorversions();
                if (!nn->nfsd_versions || !nn->nfsd4_minorversions)
                        nfsd_netns_free_versions(nn);
        }
}

int nfsd_vers(struct nfsd_net *nn, int vers, enum vers_op change)
{
        if (vers < NFSD_MINVERS || vers >= NFSD_NRVERS)
                return 0;
        switch(change) {
        case NFSD_SET:
                if (nn->nfsd_versions)
                        nn->nfsd_versions[vers] = nfsd_support_version(vers);
                break;
        case NFSD_CLEAR:
                nfsd_netns_init_versions(nn);
                if (nn->nfsd_versions)
                        nn->nfsd_versions[vers] = false;
                break;
        case NFSD_TEST:
                if (nn->nfsd_versions)
                        return nn->nfsd_versions[vers];
                fallthrough;
        case NFSD_AVAIL:
                return nfsd_support_version(vers);
        }
        return 0;
}

static void
nfsd_adjust_nfsd_versions4(struct nfsd_net *nn)
{
        unsigned i;

        for (i = 0; i <= NFSD_SUPPORTED_MINOR_VERSION; i++) {
                if (nn->nfsd4_minorversions[i])
                        return;
        }
        nfsd_vers(nn, 4, NFSD_CLEAR);
}

int nfsd_minorversion(struct nfsd_net *nn, u32 minorversion, enum vers_op change)
{
        if (minorversion > NFSD_SUPPORTED_MINOR_VERSION &&
            change != NFSD_AVAIL)
                return -1;

        switch(change) {
        case NFSD_SET:
                if (nn->nfsd4_minorversions) {
                        nfsd_vers(nn, 4, NFSD_SET);
                        nn->nfsd4_minorversions[minorversion] =
                                nfsd_vers(nn, 4, NFSD_TEST);
                }
                break;
        case NFSD_CLEAR:
                nfsd_netns_init_versions(nn);
                if (nn->nfsd4_minorversions) {
                        nn->nfsd4_minorversions[minorversion] = false;
                        nfsd_adjust_nfsd_versions4(nn);
                }
                break;
        case NFSD_TEST:
                if (nn->nfsd4_minorversions)
                        return nn->nfsd4_minorversions[minorversion];
                return nfsd_vers(nn, 4, NFSD_TEST);
        case NFSD_AVAIL:
                return minorversion <= NFSD_SUPPORTED_MINOR_VERSION &&
                        nfsd_vers(nn, 4, NFSD_AVAIL);
        }
        return 0;
}

/*
 * Maximum number of nfsd processes
 */
#define NFSD_MAXSERVS           8192

int nfsd_nrthreads(struct net *net)
{
        int rv = 0;
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);

        mutex_lock(&nfsd_mutex);
        if (nn->nfsd_serv)
                rv = nn->nfsd_serv->sv_nrthreads;
        mutex_unlock(&nfsd_mutex);
        return rv;
}

static int nfsd_init_socks(struct net *net, const struct cred *cred)
{
        int error;
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);

        if (!list_empty(&nn->nfsd_serv->sv_permsocks))
                return 0;

        error = svc_xprt_create(nn->nfsd_serv, "udp", net, PF_INET, NFS_PORT,
                                SVC_SOCK_DEFAULTS, cred);
        if (error < 0)
                return error;

        error = svc_xprt_create(nn->nfsd_serv, "tcp", net, PF_INET, NFS_PORT,
                                SVC_SOCK_DEFAULTS, cred);
        if (error < 0)
                return error;

        return 0;
}

static int nfsd_users = 0;

static int nfsd_startup_generic(void)
{
        int ret;

        if (nfsd_users++)
                return 0;

        ret = nfsd_file_cache_init();
        if (ret)
                goto dec_users;

        ret = nfs4_state_start();
        if (ret)
                goto out_file_cache;
        return 0;

out_file_cache:
        nfsd_file_cache_shutdown();
dec_users:
        nfsd_users--;
        return ret;
}

static void nfsd_shutdown_generic(void)
{
        if (--nfsd_users)
                return;

        nfs4_state_shutdown();
        nfsd_file_cache_shutdown();
}

static bool nfsd_needs_lockd(struct nfsd_net *nn)
{
        return nfsd_vers(nn, 2, NFSD_TEST) || nfsd_vers(nn, 3, NFSD_TEST);
}

/**
 * nfsd_copy_write_verifier - Atomically copy a write verifier
 * @verf: buffer in which to receive the verifier cookie
 * @nn: NFS net namespace
 *
 * This function provides a wait-free mechanism for copying the
 * namespace's write verifier without tearing it.
 */
void nfsd_copy_write_verifier(__be32 verf[2], struct nfsd_net *nn)
{
        int seq = 0;

        do {
                read_seqbegin_or_lock(&nn->writeverf_lock, &seq);
                memcpy(verf, nn->writeverf, sizeof(*verf));
        } while (need_seqretry(&nn->writeverf_lock, seq));
        done_seqretry(&nn->writeverf_lock, seq);
}

static void nfsd_reset_write_verifier_locked(struct nfsd_net *nn)
{
        struct timespec64 now;
        u64 verf;

        /*
         * Because the time value is hashed, y2038 time_t overflow
         * is irrelevant in this usage.
         */
        ktime_get_raw_ts64(&now);
        verf = siphash_2u64(now.tv_sec, now.tv_nsec, &nn->siphash_key);
        memcpy(nn->writeverf, &verf, sizeof(nn->writeverf));
}

/**
 * nfsd_reset_write_verifier - Generate a new write verifier
 * @nn: NFS net namespace
 *
 * This function updates the ->writeverf field of @nn. This field
 * contains an opaque cookie that, according to Section 18.32.3 of
 * RFC 8881, "the client can use to determine whether a server has
 * changed instance state (e.g., server restart) between a call to
 * WRITE and a subsequent call to either WRITE or COMMIT.  This
 * cookie MUST be unchanged during a single instance of the NFSv4.1
 * server and MUST be unique between instances of the NFSv4.1
 * server."
 */
void nfsd_reset_write_verifier(struct nfsd_net *nn)
{
        write_seqlock(&nn->writeverf_lock);
        nfsd_reset_write_verifier_locked(nn);
        write_sequnlock(&nn->writeverf_lock);
}

static int nfsd_startup_net(struct net *net, const struct cred *cred)
{
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);
        int ret;

        if (nn->nfsd_net_up)
                return 0;

        ret = nfsd_startup_generic();
        if (ret)
                return ret;
        ret = nfsd_init_socks(net, cred);
        if (ret)
                goto out_socks;

        if (nfsd_needs_lockd(nn) && !nn->lockd_up) {
                ret = lockd_up(net, cred);
                if (ret)
                        goto out_socks;
                nn->lockd_up = true;
        }

        ret = nfsd_file_cache_start_net(net);
        if (ret)
                goto out_lockd;
        ret = nfs4_state_start_net(net);
        if (ret)
                goto out_filecache;

#ifdef CONFIG_NFSD_V4_2_INTER_SSC
        nfsd4_ssc_init_umount_work(nn);
#endif
        nn->nfsd_net_up = true;
        return 0;

out_filecache:
        nfsd_file_cache_shutdown_net(net);
out_lockd:
        if (nn->lockd_up) {
                lockd_down(net);
                nn->lockd_up = false;
        }
out_socks:
        nfsd_shutdown_generic();
        return ret;
}

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

        nfsd_file_cache_shutdown_net(net);
        nfs4_state_shutdown_net(net);
        if (nn->lockd_up) {
                lockd_down(net);
                nn->lockd_up = false;
        }
        nn->nfsd_net_up = false;
        nfsd_shutdown_generic();
}

static DEFINE_SPINLOCK(nfsd_notifier_lock);
static int nfsd_inetaddr_event(struct notifier_block *this, unsigned long event,
        void *ptr)
{
        struct in_ifaddr *ifa = (struct in_ifaddr *)ptr;
        struct net_device *dev = ifa->ifa_dev->dev;
        struct net *net = dev_net(dev);
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);
        struct sockaddr_in sin;

        if (event != NETDEV_DOWN || !nn->nfsd_serv)
                goto out;

        spin_lock(&nfsd_notifier_lock);
        if (nn->nfsd_serv) {
                dprintk("nfsd_inetaddr_event: removed %pI4\n", &ifa->ifa_local);
                sin.sin_family = AF_INET;
                sin.sin_addr.s_addr = ifa->ifa_local;
                svc_age_temp_xprts_now(nn->nfsd_serv, (struct sockaddr *)&sin);
        }
        spin_unlock(&nfsd_notifier_lock);

out:
        return NOTIFY_DONE;
}

static struct notifier_block nfsd_inetaddr_notifier = {
        .notifier_call = nfsd_inetaddr_event,
};

#if IS_ENABLED(CONFIG_IPV6)
static int nfsd_inet6addr_event(struct notifier_block *this,
        unsigned long event, void *ptr)
{
        struct inet6_ifaddr *ifa = (struct inet6_ifaddr *)ptr;
        struct net_device *dev = ifa->idev->dev;
        struct net *net = dev_net(dev);
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);
        struct sockaddr_in6 sin6;

        if (event != NETDEV_DOWN || !nn->nfsd_serv)
                goto out;

        spin_lock(&nfsd_notifier_lock);
        if (nn->nfsd_serv) {
                dprintk("nfsd_inet6addr_event: removed %pI6\n", &ifa->addr);
                sin6.sin6_family = AF_INET6;
                sin6.sin6_addr = ifa->addr;
                if (ipv6_addr_type(&sin6.sin6_addr) & IPV6_ADDR_LINKLOCAL)
                        sin6.sin6_scope_id = ifa->idev->dev->ifindex;
                svc_age_temp_xprts_now(nn->nfsd_serv, (struct sockaddr *)&sin6);
        }
        spin_unlock(&nfsd_notifier_lock);

out:
        return NOTIFY_DONE;
}

static struct notifier_block nfsd_inet6addr_notifier = {
        .notifier_call = nfsd_inet6addr_event,
};
#endif

/* Only used under nfsd_mutex, so this atomic may be overkill: */
static atomic_t nfsd_notifier_refcount = ATOMIC_INIT(0);

static void nfsd_last_thread(struct svc_serv *serv, struct net *net)
{
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);

        /* check if the notifier still has clients */
        if (atomic_dec_return(&nfsd_notifier_refcount) == 0) {
                unregister_inetaddr_notifier(&nfsd_inetaddr_notifier);
#if IS_ENABLED(CONFIG_IPV6)
                unregister_inet6addr_notifier(&nfsd_inet6addr_notifier);
#endif
        }

        /*
         * write_ports can create the server without actually starting
         * any threads--if we get shut down before any threads are
         * started, then nfsd_last_thread will be run before any of this
         * other initialization has been done except the rpcb information.
         */
        svc_rpcb_cleanup(serv, net);
        if (!nn->nfsd_net_up)
                return;

        nfsd_shutdown_net(net);
        pr_info("nfsd: last server has exited, flushing export cache\n");
        nfsd_export_flush(net);
}

void nfsd_reset_versions(struct nfsd_net *nn)
{
        int i;

        for (i = 0; i < NFSD_NRVERS; i++)
                if (nfsd_vers(nn, i, NFSD_TEST))
                        return;

        for (i = 0; i < NFSD_NRVERS; i++)
                if (i != 4)
                        nfsd_vers(nn, i, NFSD_SET);
                else {
                        int minor = 0;
                        while (nfsd_minorversion(nn, minor, NFSD_SET) >= 0)
                                minor++;
                }
}

/*
 * Each session guarantees a negotiated per slot memory cache for replies
 * which in turn consumes memory beyond the v2/v3/v4.0 server. A dedicated
 * NFSv4.1 server might want to use more memory for a DRC than a machine
 * with mutiple services.
 *
 * Impose a hard limit on the number of pages for the DRC which varies
 * according to the machines free pages. This is of course only a default.
 *
 * For now this is a #defined shift which could be under admin control
 * in the future.
 */
static void set_max_drc(void)
{
        #define NFSD_DRC_SIZE_SHIFT     7
        nfsd_drc_max_mem = (nr_free_buffer_pages()
                                        >> NFSD_DRC_SIZE_SHIFT) * PAGE_SIZE;
        nfsd_drc_mem_used = 0;
        dprintk("%s nfsd_drc_max_mem %lu \n", __func__, nfsd_drc_max_mem);
}

static int nfsd_get_default_max_blksize(void)
{
        struct sysinfo i;
        unsigned long long target;
        unsigned long ret;

        si_meminfo(&i);
        target = (i.totalram - i.totalhigh) << PAGE_SHIFT;
        /*
         * Aim for 1/4096 of memory per thread This gives 1MB on 4Gig
         * machines, but only uses 32K on 128M machines.  Bottom out at
         * 8K on 32M and smaller.  Of course, this is only a default.
         */
        target >>= 12;

        ret = NFSSVC_MAXBLKSIZE;
        while (ret > target && ret >= 8*1024*2)
                ret /= 2;
        return ret;
}

void nfsd_shutdown_threads(struct net *net)
{
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);
        struct svc_serv *serv;

        mutex_lock(&nfsd_mutex);
        serv = nn->nfsd_serv;
        if (serv == NULL) {
                mutex_unlock(&nfsd_mutex);
                return;
        }

        svc_get(serv);
        /* Kill outstanding nfsd threads */
        svc_set_num_threads(serv, NULL, 0);
        nfsd_put(net);
        mutex_unlock(&nfsd_mutex);
}

bool i_am_nfsd(void)
{
        return kthread_func(current) == nfsd;
}

int nfsd_create_serv(struct net *net)
{
        int error;
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);
        struct svc_serv *serv;

        WARN_ON(!mutex_is_locked(&nfsd_mutex));
        if (nn->nfsd_serv) {
                svc_get(nn->nfsd_serv);
                return 0;
        }
        if (nfsd_max_blksize == 0)
                nfsd_max_blksize = nfsd_get_default_max_blksize();
        nfsd_reset_versions(nn);
        serv = svc_create_pooled(&nfsd_program, nfsd_max_blksize, nfsd);
        if (serv == NULL)
                return -ENOMEM;

        serv->sv_maxconn = nn->max_connections;
        error = svc_bind(serv, net);
        if (error < 0) {
                /* NOT nfsd_put() as notifiers (see below) haven't
                 * been set up yet.
                 */
                svc_put(serv);
                return error;
        }
        spin_lock(&nfsd_notifier_lock);
        nn->nfsd_serv = serv;
        spin_unlock(&nfsd_notifier_lock);

        set_max_drc();
        /* check if the notifier is already set */
        if (atomic_inc_return(&nfsd_notifier_refcount) == 1) {
                register_inetaddr_notifier(&nfsd_inetaddr_notifier);
#if IS_ENABLED(CONFIG_IPV6)
                register_inet6addr_notifier(&nfsd_inet6addr_notifier);
#endif
        }
        nfsd_reset_write_verifier(nn);
        return 0;
}

int nfsd_nrpools(struct net *net)
{
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);

        if (nn->nfsd_serv == NULL)
                return 0;
        else
                return nn->nfsd_serv->sv_nrpools;
}

int nfsd_get_nrthreads(int n, int *nthreads, struct net *net)
{
        int i = 0;
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);

        if (nn->nfsd_serv != NULL) {
                for (i = 0; i < nn->nfsd_serv->sv_nrpools && i < n; i++)
                        nthreads[i] = nn->nfsd_serv->sv_pools[i].sp_nrthreads;
        }

        return 0;
}

/* This is the callback for kref_put() below.
 * There is no code here as the first thing to be done is
 * call svc_shutdown_net(), but we cannot get the 'net' from
 * the kref.  So do all the work when kref_put returns true.
 */
static void nfsd_noop(struct kref *ref)
{
}

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

        if (kref_put(&nn->nfsd_serv->sv_refcnt, nfsd_noop)) {
                svc_xprt_destroy_all(nn->nfsd_serv, net);
                nfsd_last_thread(nn->nfsd_serv, net);
                svc_destroy(&nn->nfsd_serv->sv_refcnt);
                spin_lock(&nfsd_notifier_lock);
                nn->nfsd_serv = NULL;
                spin_unlock(&nfsd_notifier_lock);
        }
}

int nfsd_set_nrthreads(int n, int *nthreads, struct net *net)
{
        int i = 0;
        int tot = 0;
        int err = 0;
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);

        WARN_ON(!mutex_is_locked(&nfsd_mutex));

        if (nn->nfsd_serv == NULL || n <= 0)
                return 0;

        if (n > nn->nfsd_serv->sv_nrpools)
                n = nn->nfsd_serv->sv_nrpools;

        /* enforce a global maximum number of threads */
        tot = 0;
        for (i = 0; i < n; i++) {
                nthreads[i] = min(nthreads[i], NFSD_MAXSERVS);
                tot += nthreads[i];
        }
        if (tot > NFSD_MAXSERVS) {
                /* total too large: scale down requested numbers */
                for (i = 0; i < n && tot > 0; i++) {
                        int new = nthreads[i] * NFSD_MAXSERVS / tot;
                        tot -= (nthreads[i] - new);
                        nthreads[i] = new;
                }
                for (i = 0; i < n && tot > 0; i++) {
                        nthreads[i]--;
                        tot--;
                }
        }

        /*
         * There must always be a thread in pool 0; the admin
         * can't shut down NFS completely using pool_threads.
         */
        if (nthreads[0] == 0)
                nthreads[0] = 1;

        /* apply the new numbers */
        svc_get(nn->nfsd_serv);
        for (i = 0; i < n; i++) {
                err = svc_set_num_threads(nn->nfsd_serv,
                                          &nn->nfsd_serv->sv_pools[i],
                                          nthreads[i]);
                if (err)
                        break;
        }
        nfsd_put(net);
        return err;
}

/*
 * Adjust the number of threads and return the new number of threads.
 * This is also the function that starts the server if necessary, if
 * this is the first time nrservs is nonzero.
 */
int
nfsd_svc(int nrservs, struct net *net, const struct cred *cred)
{
        int     error;
        bool    nfsd_up_before;
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);

        mutex_lock(&nfsd_mutex);
        dprintk("nfsd: creating service\n");

        nrservs = max(nrservs, 0);
        nrservs = min(nrservs, NFSD_MAXSERVS);
        error = 0;

        if (nrservs == 0 && nn->nfsd_serv == NULL)
                goto out;

        strlcpy(nn->nfsd_name, utsname()->nodename,
                sizeof(nn->nfsd_name));

        error = nfsd_create_serv(net);
        if (error)
                goto out;

        nfsd_up_before = nn->nfsd_net_up;

        error = nfsd_startup_net(net, cred);
        if (error)
                goto out_put;
        error = svc_set_num_threads(nn->nfsd_serv, NULL, nrservs);
        if (error)
                goto out_shutdown;
        error = nn->nfsd_serv->sv_nrthreads;
out_shutdown:
        if (error < 0 && !nfsd_up_before)
                nfsd_shutdown_net(net);
out_put:
        /* Threads now hold service active */
        if (xchg(&nn->keep_active, 0))
                nfsd_put(net);
        nfsd_put(net);
out:
        mutex_unlock(&nfsd_mutex);
        return error;
}

#if defined(CONFIG_NFSD_V2_ACL) || defined(CONFIG_NFSD_V3_ACL)
static bool
nfsd_support_acl_version(int vers)
{
        if (vers >= NFSD_ACL_MINVERS && vers < NFSD_ACL_NRVERS)
                return nfsd_acl_version[vers] != NULL;
        return false;
}

static int
nfsd_acl_rpcbind_set(struct net *net, const struct svc_program *progp,
                     u32 version, int family, unsigned short proto,
                     unsigned short port)
{
        if (!nfsd_support_acl_version(version) ||
            !nfsd_vers(net_generic(net, nfsd_net_id), version, NFSD_TEST))
                return 0;
        return svc_generic_rpcbind_set(net, progp, version, family,
                        proto, port);
}

static __be32
nfsd_acl_init_request(struct svc_rqst *rqstp,
                      const struct svc_program *progp,
                      struct svc_process_info *ret)
{
        struct nfsd_net *nn = net_generic(SVC_NET(rqstp), nfsd_net_id);
        int i;

        if (likely(nfsd_support_acl_version(rqstp->rq_vers) &&
            nfsd_vers(nn, rqstp->rq_vers, NFSD_TEST)))
                return svc_generic_init_request(rqstp, progp, ret);

        ret->mismatch.lovers = NFSD_ACL_NRVERS;
        for (i = NFSD_ACL_MINVERS; i < NFSD_ACL_NRVERS; i++) {
                if (nfsd_support_acl_version(rqstp->rq_vers) &&
                    nfsd_vers(nn, i, NFSD_TEST)) {
                        ret->mismatch.lovers = i;
                        break;
                }
        }
        if (ret->mismatch.lovers == NFSD_ACL_NRVERS)
                return rpc_prog_unavail;
        ret->mismatch.hivers = NFSD_ACL_MINVERS;
        for (i = NFSD_ACL_NRVERS - 1; i >= NFSD_ACL_MINVERS; i--) {
                if (nfsd_support_acl_version(rqstp->rq_vers) &&
                    nfsd_vers(nn, i, NFSD_TEST)) {
                        ret->mismatch.hivers = i;
                        break;
                }
        }
        return rpc_prog_mismatch;
}
#endif

static int
nfsd_rpcbind_set(struct net *net, const struct svc_program *progp,
                 u32 version, int family, unsigned short proto,
                 unsigned short port)
{
        if (!nfsd_vers(net_generic(net, nfsd_net_id), version, NFSD_TEST))
                return 0;
        return svc_generic_rpcbind_set(net, progp, version, family,
                        proto, port);
}

static __be32
nfsd_init_request(struct svc_rqst *rqstp,
                  const struct svc_program *progp,
                  struct svc_process_info *ret)
{
        struct nfsd_net *nn = net_generic(SVC_NET(rqstp), nfsd_net_id);
        int i;

        if (likely(nfsd_vers(nn, rqstp->rq_vers, NFSD_TEST)))
                return svc_generic_init_request(rqstp, progp, ret);

        ret->mismatch.lovers = NFSD_NRVERS;
        for (i = NFSD_MINVERS; i < NFSD_NRVERS; i++) {
                if (nfsd_vers(nn, i, NFSD_TEST)) {
                        ret->mismatch.lovers = i;
                        break;
                }
        }
        if (ret->mismatch.lovers == NFSD_NRVERS)
                return rpc_prog_unavail;
        ret->mismatch.hivers = NFSD_MINVERS;
        for (i = NFSD_NRVERS - 1; i >= NFSD_MINVERS; i--) {
                if (nfsd_vers(nn, i, NFSD_TEST)) {
                        ret->mismatch.hivers = i;
                        break;
                }
        }
        return rpc_prog_mismatch;
}

/*
 * This is the NFS server kernel thread
 */
static int
nfsd(void *vrqstp)
{
        struct svc_rqst *rqstp = (struct svc_rqst *) vrqstp;
        struct svc_xprt *perm_sock = list_entry(rqstp->rq_server->sv_permsocks.next, typeof(struct svc_xprt), xpt_list);
        struct net *net = perm_sock->xpt_net;
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);
        int err;

        /* At this point, the thread shares current->fs
         * with the init process. We need to create files with the
         * umask as defined by the client instead of init's umask. */
        if (unshare_fs_struct() < 0) {
                printk("Unable to start nfsd thread: out of memory\n");
                goto out;
        }

        current->fs->umask = 0;

        /*
         * thread is spawned with all signals set to SIG_IGN, re-enable
         * the ones that will bring down the thread
         */
        allow_signal(SIGKILL);
        allow_signal(SIGHUP);
        allow_signal(SIGINT);
        allow_signal(SIGQUIT);

        atomic_inc(&nfsdstats.th_cnt);

        set_freezable();

        /*
         * The main request loop
         */
        for (;;) {
                /* Update sv_maxconn if it has changed */
                rqstp->rq_server->sv_maxconn = nn->max_connections;

                /*
                 * Find a socket with data available and call its
                 * recvfrom routine.
                 */
                while ((err = svc_recv(rqstp, 60*60*HZ)) == -EAGAIN)
                        ;
                if (err == -EINTR)
                        break;
                validate_process_creds();
                svc_process(rqstp);
                validate_process_creds();
        }

        /* Clear signals before calling svc_exit_thread() */
        flush_signals(current);

        atomic_dec(&nfsdstats.th_cnt);

out:
        /* Take an extra ref so that the svc_put in svc_exit_thread()
         * doesn't call svc_destroy()
         */
        svc_get(nn->nfsd_serv);

        /* Release the thread */
        svc_exit_thread(rqstp);

        /* We need to drop a ref, but may not drop the last reference
         * without holding nfsd_mutex, and we cannot wait for nfsd_mutex as that
         * could deadlock with nfsd_shutdown_threads() waiting for us.
         * So three options are:
         * - drop a non-final reference,

         * - get the mutex without waiting
         * - sleep briefly andd try the above again
         */
        while (!svc_put_not_last(nn->nfsd_serv)) {
                if (mutex_trylock(&nfsd_mutex)) {
                        nfsd_put(net);
                        mutex_unlock(&nfsd_mutex);
                        break;
                }
                msleep(20);
        }

        return 0;
}

/**
 * nfsd_dispatch - Process an NFS or NFSACL Request
 * @rqstp: incoming request
 * @statp: pointer to location of accept_stat field in RPC Reply buffer
 *
 * This RPC dispatcher integrates the NFS server's duplicate reply cache.
 *
 * Return values:
 *  %0: Processing complete; do not send a Reply
 *  %1: Processing complete; send Reply in rqstp->rq_res
 */
int nfsd_dispatch(struct svc_rqst *rqstp, __be32 *statp)
{
        const struct svc_procedure *proc = rqstp->rq_procinfo;

        /*
         * Give the xdr decoder a chance to change this if it wants
         * (necessary in the NFSv4.0 compound case)
         */
        rqstp->rq_cachetype = proc->pc_cachetype;

        svcxdr_init_decode(rqstp);
        if (!proc->pc_decode(rqstp, &rqstp->rq_arg_stream))
                goto out_decode_err;

        switch (nfsd_cache_lookup(rqstp)) {
        case RC_DOIT:
                break;
        case RC_REPLY:
                goto out_cached_reply;
        case RC_DROPIT:
                goto out_dropit;
        }

        /*
         * Need to grab the location to store the status, as
         * NFSv4 does some encoding while processing
         */
        svcxdr_init_encode(rqstp);

        *statp = proc->pc_func(rqstp);
        if (*statp == rpc_drop_reply || test_bit(RQ_DROPME, &rqstp->rq_flags))
                goto out_update_drop;

        if (!proc->pc_encode(rqstp, &rqstp->rq_res_stream))
                goto out_encode_err;

        nfsd_cache_update(rqstp, rqstp->rq_cachetype, statp + 1);
out_cached_reply:
        return 1;

out_decode_err:
        trace_nfsd_garbage_args_err(rqstp);
        *statp = rpc_garbage_args;
        return 1;

out_update_drop:
        nfsd_cache_update(rqstp, RC_NOCACHE, NULL);
out_dropit:
        return 0;

out_encode_err:
        trace_nfsd_cant_encode_err(rqstp);
        nfsd_cache_update(rqstp, RC_NOCACHE, NULL);
        *statp = rpc_system_err;
        return 1;
}

/**
 * nfssvc_decode_voidarg - Decode void arguments
 * @rqstp: Server RPC transaction context
 * @xdr: XDR stream positioned at arguments to decode
 *
 * Return values:
 *   %false: Arguments were not valid
 *   %true: Decoding was successful
 */
bool nfssvc_decode_voidarg(struct svc_rqst *rqstp, struct xdr_stream *xdr)
{
        return true;
}

/**
 * nfssvc_encode_voidres - Encode void results
 * @rqstp: Server RPC transaction context
 * @xdr: XDR stream into which to encode results
 *
 * Return values:
 *   %false: Local error while encoding
 *   %true: Encoding was successful
 */
bool nfssvc_encode_voidres(struct svc_rqst *rqstp, struct xdr_stream *xdr)
{
        return true;
}

int nfsd_pool_stats_open(struct inode *inode, struct file *file)
{
        int ret;
        struct nfsd_net *nn = net_generic(inode->i_sb->s_fs_info, nfsd_net_id);

        mutex_lock(&nfsd_mutex);
        if (nn->nfsd_serv == NULL) {
                mutex_unlock(&nfsd_mutex);
                return -ENODEV;
        }
        svc_get(nn->nfsd_serv);
        ret = svc_pool_stats_open(nn->nfsd_serv, file);
        mutex_unlock(&nfsd_mutex);
        return ret;
}

int nfsd_pool_stats_release(struct inode *inode, struct file *file)
{
        int ret = seq_release(inode, file);
        struct net *net = inode->i_sb->s_fs_info;

        mutex_lock(&nfsd_mutex);
        nfsd_put(net);
        mutex_unlock(&nfsd_mutex);
        return ret;
}