stop_machine: fix race with return value (fixes Bug #11989)

[linux-2.6/zen-sources.git] / fs / lockd / host.c

/*
 * linux/fs/lockd/host.c
 *
 * Management for NLM peer hosts. The nlm_host struct is shared
 * between client and server implementation. The only reason to
 * do so is to reduce code bloat.
 *
 * Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
 */

#include <linux/types.h>
#include <linux/slab.h>
#include <linux/in.h>
#include <linux/in6.h>
#include <linux/sunrpc/clnt.h>
#include <linux/sunrpc/svc.h>
#include <linux/lockd/lockd.h>
#include <linux/lockd/sm_inter.h>
#include <linux/mutex.h>

#include <net/ipv6.h>

#define NLMDBG_FACILITY         NLMDBG_HOSTCACHE
#define NLM_HOST_NRHASH         32
#define NLM_HOST_REBIND         (60 * HZ)
#define NLM_HOST_EXPIRE         (300 * HZ)
#define NLM_HOST_COLLECT        (120 * HZ)

static struct hlist_head        nlm_hosts[NLM_HOST_NRHASH];
static unsigned long            next_gc;
static int                      nrhosts;
static DEFINE_MUTEX(nlm_host_mutex);

static void                     nlm_gc_hosts(void);
static struct nsm_handle        *nsm_find(const struct sockaddr *sap,
                                                const size_t salen,
                                                const char *hostname,
                                                const size_t hostname_len,
                                                const int create);

struct nlm_lookup_host_info {
        const int               server;         /* search for server|client */
        const struct sockaddr   *sap;           /* address to search for */
        const size_t            salen;          /* it's length */
        const unsigned short    protocol;       /* transport to search for*/
        const u32               version;        /* NLM version to search for */
        const char              *hostname;      /* remote's hostname */
        const size_t            hostname_len;   /* it's length */
        const struct sockaddr   *src_sap;       /* our address (optional) */
        const size_t            src_len;        /* it's length */
};

/*
 * Hash function must work well on big- and little-endian platforms
 */
static unsigned int __nlm_hash32(const __be32 n)
{
        unsigned int hash = (__force u32)n ^ ((__force u32)n >> 16);
        return hash ^ (hash >> 8);
}

static unsigned int __nlm_hash_addr4(const struct sockaddr *sap)
{
        const struct sockaddr_in *sin = (struct sockaddr_in *)sap;
        return __nlm_hash32(sin->sin_addr.s_addr);
}

static unsigned int __nlm_hash_addr6(const struct sockaddr *sap)
{
        const struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)sap;
        const struct in6_addr addr = sin6->sin6_addr;
        return __nlm_hash32(addr.s6_addr32[0]) ^
               __nlm_hash32(addr.s6_addr32[1]) ^
               __nlm_hash32(addr.s6_addr32[2]) ^
               __nlm_hash32(addr.s6_addr32[3]);
}

static unsigned int nlm_hash_address(const struct sockaddr *sap)
{
        unsigned int hash;

        switch (sap->sa_family) {
        case AF_INET:
                hash = __nlm_hash_addr4(sap);
                break;
        case AF_INET6:
                hash = __nlm_hash_addr6(sap);
                break;
        default:
                hash = 0;
        }
        return hash & (NLM_HOST_NRHASH - 1);
}

static void nlm_clear_port(struct sockaddr *sap)
{
        switch (sap->sa_family) {
        case AF_INET:
                ((struct sockaddr_in *)sap)->sin_port = 0;
                break;
        case AF_INET6:
                ((struct sockaddr_in6 *)sap)->sin6_port = 0;
                break;
        }
}

static void nlm_display_address(const struct sockaddr *sap,
                                char *buf, const size_t len)
{
        const struct sockaddr_in *sin = (struct sockaddr_in *)sap;
        const struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)sap;

        switch (sap->sa_family) {
        case AF_UNSPEC:
                snprintf(buf, len, "unspecified");
                break;
        case AF_INET:
                snprintf(buf, len, NIPQUAD_FMT, NIPQUAD(sin->sin_addr.s_addr));
                break;
        case AF_INET6:
                if (ipv6_addr_v4mapped(&sin6->sin6_addr))
                        snprintf(buf, len, NIPQUAD_FMT,
                                 NIPQUAD(sin6->sin6_addr.s6_addr32[3]));
                else
                        snprintf(buf, len, NIP6_FMT, NIP6(sin6->sin6_addr));
                break;
        default:
                snprintf(buf, len, "unsupported address family");
                break;
        }
}

/*
 * Common host lookup routine for server & client
 */
static struct nlm_host *nlm_lookup_host(struct nlm_lookup_host_info *ni)
{
        struct hlist_head *chain;
        struct hlist_node *pos;
        struct nlm_host *host;
        struct nsm_handle *nsm = NULL;

        mutex_lock(&nlm_host_mutex);

        if (time_after_eq(jiffies, next_gc))
                nlm_gc_hosts();

        /* We may keep several nlm_host objects for a peer, because each
         * nlm_host is identified by
         * (address, protocol, version, server/client)
         * We could probably simplify this a little by putting all those
         * different NLM rpc_clients into one single nlm_host object.
         * This would allow us to have one nlm_host per address.
         */
        chain = &nlm_hosts[nlm_hash_address(ni->sap)];
        hlist_for_each_entry(host, pos, chain, h_hash) {
                if (!nlm_cmp_addr(nlm_addr(host), ni->sap))
                        continue;

                /* See if we have an NSM handle for this client */
                if (!nsm)
                        nsm = host->h_nsmhandle;

                if (host->h_proto != ni->protocol)
                        continue;
                if (host->h_version != ni->version)
                        continue;
                if (host->h_server != ni->server)
                        continue;
                if (!nlm_cmp_addr(nlm_srcaddr(host), ni->src_sap))
                        continue;

                /* Move to head of hash chain. */
                hlist_del(&host->h_hash);
                hlist_add_head(&host->h_hash, chain);

                nlm_get_host(host);
                dprintk("lockd: nlm_lookup_host found host %s (%s)\n",
                                host->h_name, host->h_addrbuf);
                goto out;
        }

        /*
         * The host wasn't in our hash table.  If we don't
         * have an NSM handle for it yet, create one.
         */
        if (nsm)
                atomic_inc(&nsm->sm_count);
        else {
                host = NULL;
                nsm = nsm_find(ni->sap, ni->salen,
                                ni->hostname, ni->hostname_len, 1);
                if (!nsm) {
                        dprintk("lockd: nlm_lookup_host failed; "
                                "no nsm handle\n");
                        goto out;
                }
        }

        host = kzalloc(sizeof(*host), GFP_KERNEL);
        if (!host) {
                nsm_release(nsm);
                dprintk("lockd: nlm_lookup_host failed; no memory\n");
                goto out;
        }
        host->h_name       = nsm->sm_name;
        memcpy(nlm_addr(host), ni->sap, ni->salen);
        host->h_addrlen = ni->salen;
        nlm_clear_port(nlm_addr(host));
        memcpy(nlm_srcaddr(host), ni->src_sap, ni->src_len);
        host->h_version    = ni->version;
        host->h_proto      = ni->protocol;
        host->h_rpcclnt    = NULL;
        mutex_init(&host->h_mutex);
        host->h_nextrebind = jiffies + NLM_HOST_REBIND;
        host->h_expires    = jiffies + NLM_HOST_EXPIRE;
        atomic_set(&host->h_count, 1);
        init_waitqueue_head(&host->h_gracewait);
        init_rwsem(&host->h_rwsem);
        host->h_state      = 0;                 /* pseudo NSM state */
        host->h_nsmstate   = 0;                 /* real NSM state */
        host->h_nsmhandle  = nsm;
        host->h_server     = ni->server;
        hlist_add_head(&host->h_hash, chain);
        INIT_LIST_HEAD(&host->h_lockowners);
        spin_lock_init(&host->h_lock);
        INIT_LIST_HEAD(&host->h_granted);
        INIT_LIST_HEAD(&host->h_reclaim);

        nrhosts++;

        nlm_display_address((struct sockaddr *)&host->h_addr,
                                host->h_addrbuf, sizeof(host->h_addrbuf));
        nlm_display_address((struct sockaddr *)&host->h_srcaddr,
                                host->h_srcaddrbuf, sizeof(host->h_srcaddrbuf));

        dprintk("lockd: nlm_lookup_host created host %s\n",
                        host->h_name);

out:
        mutex_unlock(&nlm_host_mutex);
        return host;
}

/*
 * Destroy a host
 */
static void
nlm_destroy_host(struct nlm_host *host)
{
        struct rpc_clnt *clnt;

        BUG_ON(!list_empty(&host->h_lockowners));
        BUG_ON(atomic_read(&host->h_count));

        /*
         * Release NSM handle and unmonitor host.
         */
        nsm_unmonitor(host);

        clnt = host->h_rpcclnt;
        if (clnt != NULL)
                rpc_shutdown_client(clnt);
        kfree(host);
}

/**
 * nlmclnt_lookup_host - Find an NLM host handle matching a remote server
 * @sap: network address of server
 * @salen: length of server address
 * @protocol: transport protocol to use
 * @version: NLM protocol version
 * @hostname: '\0'-terminated hostname of server
 *
 * Returns an nlm_host structure that matches the passed-in
 * [server address, transport protocol, NLM version, server hostname].
 * If one doesn't already exist in the host cache, a new handle is
 * created and returned.
 */
struct nlm_host *nlmclnt_lookup_host(const struct sockaddr *sap,
                                     const size_t salen,
                                     const unsigned short protocol,
                                     const u32 version, const char *hostname)
{
        const struct sockaddr source = {
                .sa_family      = AF_UNSPEC,
        };
        struct nlm_lookup_host_info ni = {
                .server         = 0,
                .sap            = sap,
                .salen          = salen,
                .protocol       = protocol,
                .version        = version,
                .hostname       = hostname,
                .hostname_len   = strlen(hostname),
                .src_sap        = &source,
                .src_len        = sizeof(source),
        };

        dprintk("lockd: %s(host='%s', vers=%u, proto=%s)\n", __func__,
                        (hostname ? hostname : "<none>"), version,
                        (protocol == IPPROTO_UDP ? "udp" : "tcp"));

        return nlm_lookup_host(&ni);
}

/**
 * nlmsvc_lookup_host - Find an NLM host handle matching a remote client
 * @rqstp: incoming NLM request
 * @hostname: name of client host
 * @hostname_len: length of client hostname
 *
 * Returns an nlm_host structure that matches the [client address,
 * transport protocol, NLM version, client hostname] of the passed-in
 * NLM request.  If one doesn't already exist in the host cache, a
 * new handle is created and returned.
 *
 * Before possibly creating a new nlm_host, construct a sockaddr
 * for a specific source address in case the local system has
 * multiple network addresses.  The family of the address in
 * rq_daddr is guaranteed to be the same as the family of the
 * address in rq_addr, so it's safe to use the same family for
 * the source address.
 */
struct nlm_host *nlmsvc_lookup_host(const struct svc_rqst *rqstp,
                                    const char *hostname,
                                    const size_t hostname_len)
{
        struct sockaddr_in sin = {
                .sin_family     = AF_INET,
        };
        struct sockaddr_in6 sin6 = {
                .sin6_family    = AF_INET6,
        };
        struct nlm_lookup_host_info ni = {
                .server         = 1,
                .sap            = svc_addr(rqstp),
                .salen          = rqstp->rq_addrlen,
                .protocol       = rqstp->rq_prot,
                .version        = rqstp->rq_vers,
                .hostname       = hostname,
                .hostname_len   = hostname_len,
                .src_len        = rqstp->rq_addrlen,
        };

        dprintk("lockd: %s(host='%*s', vers=%u, proto=%s)\n", __func__,
                        (int)hostname_len, hostname, rqstp->rq_vers,
                        (rqstp->rq_prot == IPPROTO_UDP ? "udp" : "tcp"));

        switch (ni.sap->sa_family) {
        case AF_INET:
                sin.sin_addr.s_addr = rqstp->rq_daddr.addr.s_addr;
                ni.src_sap = (struct sockaddr *)&sin;
                break;
        case AF_INET6:
                ipv6_addr_copy(&sin6.sin6_addr, &rqstp->rq_daddr.addr6);
                ni.src_sap = (struct sockaddr *)&sin6;
                break;
        default:
                return NULL;
        }

        return nlm_lookup_host(&ni);
}

/*
 * Create the NLM RPC client for an NLM peer
 */
struct rpc_clnt *
nlm_bind_host(struct nlm_host *host)
{
        struct rpc_clnt *clnt;

        dprintk("lockd: nlm_bind_host %s (%s), my addr=%s\n",
                        host->h_name, host->h_addrbuf, host->h_srcaddrbuf);

        /* Lock host handle */
        mutex_lock(&host->h_mutex);

        /* If we've already created an RPC client, check whether
         * RPC rebind is required
         */
        if ((clnt = host->h_rpcclnt) != NULL) {
                if (time_after_eq(jiffies, host->h_nextrebind)) {
                        rpc_force_rebind(clnt);
                        host->h_nextrebind = jiffies + NLM_HOST_REBIND;
                        dprintk("lockd: next rebind in %lu jiffies\n",
                                        host->h_nextrebind - jiffies);
                }
        } else {
                unsigned long increment = nlmsvc_timeout;
                struct rpc_timeout timeparms = {
                        .to_initval     = increment,
                        .to_increment   = increment,
                        .to_maxval      = increment * 6UL,
                        .to_retries     = 5U,
                };
                struct rpc_create_args args = {
                        .protocol       = host->h_proto,
                        .address        = nlm_addr(host),
                        .addrsize       = host->h_addrlen,
                        .saddress       = nlm_srcaddr(host),
                        .timeout        = &timeparms,
                        .servername     = host->h_name,
                        .program        = &nlm_program,
                        .version        = host->h_version,
                        .authflavor     = RPC_AUTH_UNIX,
                        .flags          = (RPC_CLNT_CREATE_NOPING |
                                           RPC_CLNT_CREATE_AUTOBIND),
                };

                /*
                 * lockd retries server side blocks automatically so we want
                 * those to be soft RPC calls. Client side calls need to be
                 * hard RPC tasks.
                 */
                if (!host->h_server)
                        args.flags |= RPC_CLNT_CREATE_HARDRTRY;

                clnt = rpc_create(&args);
                if (!IS_ERR(clnt))
                        host->h_rpcclnt = clnt;
                else {
                        printk("lockd: couldn't create RPC handle for %s\n", host->h_name);
                        clnt = NULL;
                }
        }

        mutex_unlock(&host->h_mutex);
        return clnt;
}

/*
 * Force a portmap lookup of the remote lockd port
 */
void
nlm_rebind_host(struct nlm_host *host)
{
        dprintk("lockd: rebind host %s\n", host->h_name);
        if (host->h_rpcclnt && time_after_eq(jiffies, host->h_nextrebind)) {
                rpc_force_rebind(host->h_rpcclnt);
                host->h_nextrebind = jiffies + NLM_HOST_REBIND;
        }
}

/*
 * Increment NLM host count
 */
struct nlm_host * nlm_get_host(struct nlm_host *host)
{
        if (host) {
                dprintk("lockd: get host %s\n", host->h_name);
                atomic_inc(&host->h_count);
                host->h_expires = jiffies + NLM_HOST_EXPIRE;
        }
        return host;
}

/*
 * Release NLM host after use
 */
void nlm_release_host(struct nlm_host *host)
{
        if (host != NULL) {
                dprintk("lockd: release host %s\n", host->h_name);
                BUG_ON(atomic_read(&host->h_count) < 0);
                if (atomic_dec_and_test(&host->h_count)) {
                        BUG_ON(!list_empty(&host->h_lockowners));
                        BUG_ON(!list_empty(&host->h_granted));
                        BUG_ON(!list_empty(&host->h_reclaim));
                }
        }
}

/*
 * We were notified that the host indicated by address &sin
 * has rebooted.
 * Release all resources held by that peer.
 */
void nlm_host_rebooted(const struct sockaddr_in *sin,
                                const char *hostname,
                                unsigned int hostname_len,
                                u32 new_state)
{
        struct hlist_head *chain;
        struct hlist_node *pos;
        struct nsm_handle *nsm;
        struct nlm_host *host;

        nsm = nsm_find((struct sockaddr *)sin, sizeof(*sin),
                        hostname, hostname_len, 0);
        if (nsm == NULL) {
                dprintk("lockd: never saw rebooted peer '%.*s' before\n",
                                hostname_len, hostname);
                return;
        }

        dprintk("lockd: nlm_host_rebooted(%.*s, %s)\n",
                        hostname_len, hostname, nsm->sm_addrbuf);

        /* When reclaiming locks on this peer, make sure that
         * we set up a new notification */
        nsm->sm_monitored = 0;

        /* Mark all hosts tied to this NSM state as having rebooted.
         * We run the loop repeatedly, because we drop the host table
         * lock for this.
         * To avoid processing a host several times, we match the nsmstate.
         */
again:  mutex_lock(&nlm_host_mutex);
        for (chain = nlm_hosts; chain < nlm_hosts + NLM_HOST_NRHASH; ++chain) {
                hlist_for_each_entry(host, pos, chain, h_hash) {
                        if (host->h_nsmhandle == nsm
                         && host->h_nsmstate != new_state) {
                                host->h_nsmstate = new_state;
                                host->h_state++;

                                nlm_get_host(host);
                                mutex_unlock(&nlm_host_mutex);

                                if (host->h_server) {
                                        /* We're server for this guy, just ditch
                                         * all the locks he held. */
                                        nlmsvc_free_host_resources(host);
                                } else {
                                        /* He's the server, initiate lock recovery. */
                                        nlmclnt_recovery(host);
                                }

                                nlm_release_host(host);
                                goto again;
                        }
                }
        }

        mutex_unlock(&nlm_host_mutex);
}

/*
 * Shut down the hosts module.
 * Note that this routine is called only at server shutdown time.
 */
void
nlm_shutdown_hosts(void)
{
        struct hlist_head *chain;
        struct hlist_node *pos;
        struct nlm_host *host;

        dprintk("lockd: shutting down host module\n");
        mutex_lock(&nlm_host_mutex);

        /* First, make all hosts eligible for gc */
        dprintk("lockd: nuking all hosts...\n");
        for (chain = nlm_hosts; chain < nlm_hosts + NLM_HOST_NRHASH; ++chain) {
                hlist_for_each_entry(host, pos, chain, h_hash) {
                        host->h_expires = jiffies - 1;
                        if (host->h_rpcclnt) {
                                rpc_shutdown_client(host->h_rpcclnt);
                                host->h_rpcclnt = NULL;
                        }
                }
        }

        /* Then, perform a garbage collection pass */
        nlm_gc_hosts();
        mutex_unlock(&nlm_host_mutex);

        /* complain if any hosts are left */
        if (nrhosts) {
                printk(KERN_WARNING "lockd: couldn't shutdown host module!\n");
                dprintk("lockd: %d hosts left:\n", nrhosts);
                for (chain = nlm_hosts; chain < nlm_hosts + NLM_HOST_NRHASH; ++chain) {
                        hlist_for_each_entry(host, pos, chain, h_hash) {
                                dprintk("       %s (cnt %d use %d exp %ld)\n",
                                        host->h_name, atomic_read(&host->h_count),
                                        host->h_inuse, host->h_expires);
                        }
                }
        }
}

/*
 * Garbage collect any unused NLM hosts.
 * This GC combines reference counting for async operations with
 * mark & sweep for resources held by remote clients.
 */
static void
nlm_gc_hosts(void)
{
        struct hlist_head *chain;
        struct hlist_node *pos, *next;
        struct nlm_host *host;

        dprintk("lockd: host garbage collection\n");
        for (chain = nlm_hosts; chain < nlm_hosts + NLM_HOST_NRHASH; ++chain) {
                hlist_for_each_entry(host, pos, chain, h_hash)
                        host->h_inuse = 0;
        }

        /* Mark all hosts that hold locks, blocks or shares */
        nlmsvc_mark_resources();

        for (chain = nlm_hosts; chain < nlm_hosts + NLM_HOST_NRHASH; ++chain) {
                hlist_for_each_entry_safe(host, pos, next, chain, h_hash) {
                        if (atomic_read(&host->h_count) || host->h_inuse
                         || time_before(jiffies, host->h_expires)) {
                                dprintk("nlm_gc_hosts skipping %s (cnt %d use %d exp %ld)\n",
                                        host->h_name, atomic_read(&host->h_count),
                                        host->h_inuse, host->h_expires);
                                continue;
                        }
                        dprintk("lockd: delete host %s\n", host->h_name);
                        hlist_del_init(&host->h_hash);

                        nlm_destroy_host(host);
                        nrhosts--;
                }
        }

        next_gc = jiffies + NLM_HOST_COLLECT;
}


/*
 * Manage NSM handles
 */
static LIST_HEAD(nsm_handles);
static DEFINE_SPINLOCK(nsm_lock);

static struct nsm_handle *nsm_find(const struct sockaddr *sap,
                                   const size_t salen,
                                   const char *hostname,
                                   const size_t hostname_len,
                                   const int create)
{
        struct nsm_handle *nsm = NULL;
        struct nsm_handle *pos;

        if (!sap)
                return NULL;

        if (hostname && memchr(hostname, '/', hostname_len) != NULL) {
                if (printk_ratelimit()) {
                        printk(KERN_WARNING "Invalid hostname \"%.*s\" "
                                            "in NFS lock request\n",
                                (int)hostname_len, hostname);
                }
                return NULL;
        }

retry:
        spin_lock(&nsm_lock);
        list_for_each_entry(pos, &nsm_handles, sm_link) {

                if (hostname && nsm_use_hostnames) {
                        if (strlen(pos->sm_name) != hostname_len
                         || memcmp(pos->sm_name, hostname, hostname_len))
                                continue;
                } else if (!nlm_cmp_addr(nsm_addr(pos), sap))
                        continue;
                atomic_inc(&pos->sm_count);
                kfree(nsm);
                nsm = pos;
                goto found;
        }
        if (nsm) {
                list_add(&nsm->sm_link, &nsm_handles);
                goto found;
        }
        spin_unlock(&nsm_lock);

        if (!create)
                return NULL;

        nsm = kzalloc(sizeof(*nsm) + hostname_len + 1, GFP_KERNEL);
        if (nsm == NULL)
                return NULL;

        memcpy(nsm_addr(nsm), sap, salen);
        nsm->sm_addrlen = salen;
        nsm->sm_name = (char *) (nsm + 1);
        memcpy(nsm->sm_name, hostname, hostname_len);
        nsm->sm_name[hostname_len] = '\0';
        nlm_display_address((struct sockaddr *)&nsm->sm_addr,
                                nsm->sm_addrbuf, sizeof(nsm->sm_addrbuf));
        atomic_set(&nsm->sm_count, 1);
        goto retry;

found:
        spin_unlock(&nsm_lock);
        return nsm;
}

/*
 * Release an NSM handle
 */
void
nsm_release(struct nsm_handle *nsm)
{
        if (!nsm)
                return;
        if (atomic_dec_and_lock(&nsm->sm_count, &nsm_lock)) {
                list_del(&nsm->sm_link);
                spin_unlock(&nsm_lock);
                kfree(nsm);
        }
}