lockd: fix race in nlm_release()

[linux-2.6/kmemtrace.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/sunrpc/clnt.h>
#include <linux/sunrpc/svc.h>
#include <linux/lockd/lockd.h>
#include <linux/lockd/sm_inter.h>
#include <linux/mutex.h>


#define NLMDBG_FACILITY         NLMDBG_HOSTCACHE
#define NLM_HOST_NRHASH         32
#define NLM_ADDRHASH(addr)      (ntohl(addr) & (NLM_HOST_NRHASH-1))
#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_in *,
                                        const char *, unsigned int, int);
static struct nsm_handle *      nsm_find(const struct sockaddr_in *sin,
                                         const char *hostname,
                                         unsigned int hostname_len);

/*
 * Common host lookup routine for server & client
 */
static struct nlm_host *
nlm_lookup_host(int server, const struct sockaddr_in *sin,
                int proto, int version, const char *hostname,
                unsigned int hostname_len,
                const struct sockaddr_in *ssin)
{
        struct hlist_head *chain;
        struct hlist_node *pos;
        struct nlm_host *host;
        struct nsm_handle *nsm = NULL;
        int             hash;

        dprintk("lockd: nlm_lookup_host("NIPQUAD_FMT"->"NIPQUAD_FMT
                        ", p=%d, v=%d, my role=%s, name=%.*s)\n",
                        NIPQUAD(ssin->sin_addr.s_addr),
                        NIPQUAD(sin->sin_addr.s_addr), proto, version,
                        server? "server" : "client",
                        hostname_len,
                        hostname? hostname : "<none>");


        hash = NLM_ADDRHASH(sin->sin_addr.s_addr);

        /* Lock hash table */
        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[hash];
        hlist_for_each_entry(host, pos, chain, h_hash) {
                if (!nlm_cmp_addr(&host->h_addr, sin))
                        continue;

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

                if (host->h_proto != proto)
                        continue;
                if (host->h_version != version)
                        continue;
                if (host->h_server != server)
                        continue;
                if (!nlm_cmp_addr(&host->h_saddr, ssin))
                        continue;

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

                nlm_get_host(host);
                goto out;
        }
        if (nsm)
                atomic_inc(&nsm->sm_count);

        host = NULL;

        /* Sadly, the host isn't in our hash table yet. See if
         * we have an NSM handle for it. If not, create one.
         */
        if (!nsm && !(nsm = nsm_find(sin, hostname, hostname_len)))
                goto out;

        host = kzalloc(sizeof(*host), GFP_KERNEL);
        if (!host) {
                nsm_release(nsm);
                goto out;
        }
        host->h_name       = nsm->sm_name;
        host->h_addr       = *sin;
        host->h_addr.sin_port = 0;      /* ouch! */
        host->h_saddr      = *ssin;
        host->h_version    = version;
        host->h_proto      = proto;
        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     = 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++;
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);
}

/*
 * Find an NLM server handle in the cache. If there is none, create it.
 */
struct nlm_host *
nlmclnt_lookup_host(const struct sockaddr_in *sin, int proto, int version,
                        const char *hostname, unsigned int hostname_len)
{
        struct sockaddr_in ssin = {0};

        return nlm_lookup_host(0, sin, proto, version,
                               hostname, hostname_len, &ssin);
}

/*
 * Find an NLM client handle in the cache. If there is none, create it.
 */
struct nlm_host *
nlmsvc_lookup_host(struct svc_rqst *rqstp,
                        const char *hostname, unsigned int hostname_len)
{
        struct sockaddr_in ssin = {0};

        ssin.sin_addr = rqstp->rq_daddr.addr;
        return nlm_lookup_host(1, svc_addr_in(rqstp),
                               rqstp->rq_prot, rqstp->rq_vers,
                               hostname, hostname_len, &ssin);
}

/*
 * 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("NIPQUAD_FMT"->"NIPQUAD_FMT")\n",
                        NIPQUAD(host->h_saddr.sin_addr),
                        NIPQUAD(host->h_addr.sin_addr));

        /* 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 %ld 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        = (struct sockaddr *)&host->h_addr,
                        .addrsize       = sizeof(host->h_addr),
                        .saddress       = (struct sockaddr *)&host->h_saddr,
                        .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;

        dprintk("lockd: nlm_host_rebooted(%s, %u.%u.%u.%u)\n",
                        hostname, NIPQUAD(sin->sin_addr));

        /* Find the NSM handle for this peer */
        if (!(nsm = __nsm_find(sin, hostname, hostname_len, 0)))
                return;

        /* 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_MUTEX(nsm_mutex);

static struct nsm_handle *
__nsm_find(const struct sockaddr_in *sin,
                const char *hostname, unsigned int hostname_len,
                int create)
{
        struct nsm_handle *nsm = NULL;
        struct list_head *pos;

        if (!sin)
                return NULL;

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

        mutex_lock(&nsm_mutex);
        list_for_each(pos, &nsm_handles) {
                nsm = list_entry(pos, struct nsm_handle, sm_link);

                if (hostname && nsm_use_hostnames) {
                        if (strlen(nsm->sm_name) != hostname_len
                         || memcmp(nsm->sm_name, hostname, hostname_len))
                                continue;
                } else if (!nlm_cmp_addr(&nsm->sm_addr, sin))
                        continue;
                atomic_inc(&nsm->sm_count);
                goto out;
        }

        if (!create) {
                nsm = NULL;
                goto out;
        }

        nsm = kzalloc(sizeof(*nsm) + hostname_len + 1, GFP_KERNEL);
        if (nsm != NULL) {
                nsm->sm_addr = *sin;
                nsm->sm_name = (char *) (nsm + 1);
                memcpy(nsm->sm_name, hostname, hostname_len);
                nsm->sm_name[hostname_len] = '\0';
                atomic_set(&nsm->sm_count, 1);

                list_add(&nsm->sm_link, &nsm_handles);
        }

out:
        mutex_unlock(&nsm_mutex);
        return nsm;
}

static struct nsm_handle *
nsm_find(const struct sockaddr_in *sin, const char *hostname,
         unsigned int hostname_len)
{
        return __nsm_find(sin, hostname, hostname_len, 1);
}

/*
 * Release an NSM handle
 */
void
nsm_release(struct nsm_handle *nsm)
{
        if (!nsm)
                return;
        mutex_lock(&nsm_mutex);
        if (atomic_dec_and_test(&nsm->sm_count)) {
                list_del(&nsm->sm_link);
                kfree(nsm);
        }
        mutex_unlock(&nsm_mutex);
}