fs/lockd/host.c

   1 /*
   2  * linux/fs/lockd/host.c
   3  *
   4  * Management for NLM peer hosts. The nlm_host struct is shared
   5  * between client and server implementation. The only reason to
   6  * do so is to reduce code bloat.
   7  *
   8  * Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
   9  */
  10
  11 #include <linux/types.h>
  12 #include <linux/slab.h>
  13 #include <linux/in.h>
  14 #include <linux/in6.h>
  15 #include <linux/sunrpc/clnt.h>
  16 #include <linux/sunrpc/svc.h>
  17 #include <linux/lockd/lockd.h>
  18 #include <linux/mutex.h>
  19
  20 #include <net/ipv6.h>
  21
  22 #define NLMDBG_FACILITY         NLMDBG_HOSTCACHE
  23 #define NLM_HOST_NRHASH         32
  24 #define NLM_HOST_REBIND         (60 * HZ)
  25 #define NLM_HOST_EXPIRE         (300 * HZ)
  26 #define NLM_HOST_COLLECT        (120 * HZ)
  27
  28 static struct hlist_head        nlm_hosts[NLM_HOST_NRHASH];
  29 static struct hlist_head        nlm_client_hosts[NLM_HOST_NRHASH];
  30
  31 #define for_each_host(host, pos, chain, table) \
  32         for ((chain) = (table); \
  33              (chain) < (table) + NLM_HOST_NRHASH; ++(chain)) \
  34                 hlist_for_each_entry((host), (pos), (chain), h_hash)
  35
  36 #define for_each_host_safe(host, pos, next, chain, table) \
  37         for ((chain) = (table); \
  38              (chain) < (table) + NLM_HOST_NRHASH; ++(chain)) \
  39                 hlist_for_each_entry_safe((host), (pos), (next), \
  40                                                 (chain), h_hash)
  41
  42 static unsigned long            next_gc;
  43 static int                      nrhosts;
  44 static DEFINE_MUTEX(nlm_host_mutex);
  45
  46 static void                     nlm_gc_hosts(void);
  47
  48 struct nlm_lookup_host_info {
  49         const int               server;         /* search for server|client */
  50         const struct sockaddr   *sap;           /* address to search for */
  51         const size_t            salen;          /* it's length */
  52         const unsigned short    protocol;       /* transport to search for*/
  53         const u32               version;        /* NLM version to search for */
  54         const char              *hostname;      /* remote's hostname */
  55         const size_t            hostname_len;   /* it's length */
  56         const struct sockaddr   *src_sap;       /* our address (optional) */
  57         const size_t            src_len;        /* it's length */
  58         const int               noresvport;     /* use non-priv port */
  59 };
  60
  61 /*
  62  * Hash function must work well on big- and little-endian platforms
  63  */
  64 static unsigned int __nlm_hash32(const __be32 n)
  65 {
  66         unsigned int hash = (__force u32)n ^ ((__force u32)n >> 16);
  67         return hash ^ (hash >> 8);
  68 }
  69
  70 static unsigned int __nlm_hash_addr4(const struct sockaddr *sap)
  71 {
  72         const struct sockaddr_in *sin = (struct sockaddr_in *)sap;
  73         return __nlm_hash32(sin->sin_addr.s_addr);
  74 }
  75
  76 static unsigned int __nlm_hash_addr6(const struct sockaddr *sap)
  77 {
  78         const struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)sap;
  79         const struct in6_addr addr = sin6->sin6_addr;
  80         return __nlm_hash32(addr.s6_addr32[0]) ^
  81                __nlm_hash32(addr.s6_addr32[1]) ^
  82                __nlm_hash32(addr.s6_addr32[2]) ^
  83                __nlm_hash32(addr.s6_addr32[3]);
  84 }
  85
  86 static unsigned int nlm_hash_address(const struct sockaddr *sap)
  87 {
  88         unsigned int hash;
  89
  90         switch (sap->sa_family) {
  91         case AF_INET:
  92                 hash = __nlm_hash_addr4(sap);
  93                 break;
  94         case AF_INET6:
  95                 hash = __nlm_hash_addr6(sap);
  96                 break;
  97         default:
  98                 hash = 0;
  99         }
 100         return hash & (NLM_HOST_NRHASH - 1);
 101 }
 102
 103 /*
 104  * Allocate and initialize an nlm_host.  Common to both client and server.
 105  */
 106 static struct nlm_host *nlm_alloc_host(struct nlm_lookup_host_info *ni,
 107                                        struct nsm_handle *nsm)
 108 {
 109         struct nlm_host *host = NULL;
 110         unsigned long now = jiffies;
 111
 112         if (nsm != NULL)
 113                 atomic_inc(&nsm->sm_count);
 114         else {
 115                 host = NULL;
 116                 nsm = nsm_get_handle(ni->sap, ni->salen,
 117                                         ni->hostname, ni->hostname_len);
 118                 if (unlikely(nsm == NULL)) {
 119                         dprintk("lockd: %s failed; no nsm handle\n",
 120                                 __func__);
 121                         goto out;
 122                 }
 123         }
 124
 125         host = kmalloc(sizeof(*host), GFP_KERNEL);
 126         if (unlikely(host == NULL)) {
 127                 dprintk("lockd: %s failed; no memory\n", __func__);
 128                 nsm_release(nsm);
 129                 goto out;
 130         }
 131
 132         memcpy(nlm_addr(host), ni->sap, ni->salen);
 133         host->h_addrlen    = ni->salen;
 134         rpc_set_port(nlm_addr(host), 0);
 135         host->h_srcaddrlen = 0;
 136
 137         host->h_rpcclnt    = NULL;
 138         host->h_name       = nsm->sm_name;
 139         host->h_version    = ni->version;
 140         host->h_proto      = ni->protocol;
 141         host->h_reclaiming = 0;
 142         host->h_server     = ni->server;
 143         host->h_noresvport = ni->noresvport;
 144         host->h_inuse      = 0;
 145         init_waitqueue_head(&host->h_gracewait);
 146         init_rwsem(&host->h_rwsem);
 147         host->h_state      = 0;
 148         host->h_nsmstate   = 0;
 149         host->h_pidcount   = 0;
 150         atomic_set(&host->h_count, 1);
 151         mutex_init(&host->h_mutex);
 152         host->h_nextrebind = now + NLM_HOST_REBIND;
 153         host->h_expires    = now + NLM_HOST_EXPIRE;
 154         INIT_LIST_HEAD(&host->h_lockowners);
 155         spin_lock_init(&host->h_lock);
 156         INIT_LIST_HEAD(&host->h_granted);
 157         INIT_LIST_HEAD(&host->h_reclaim);
 158         host->h_nsmhandle  = nsm;
 159         host->h_addrbuf    = nsm->sm_addrbuf;
 160
 161 out:
 162         return host;
 163 }
 164
 165 /*
 166  * Common host lookup routine for server & client
 167  */
 168 static struct nlm_host *nlm_lookup_host(struct nlm_lookup_host_info *ni)
 169 {
 170         struct hlist_head *chain;
 171         struct hlist_node *pos;
 172         struct nlm_host *host;
 173         struct nsm_handle *nsm = NULL;
 174
 175         mutex_lock(&nlm_host_mutex);
 176
 177         if (time_after_eq(jiffies, next_gc))
 178                 nlm_gc_hosts();
 179
 180         /* We may keep several nlm_host objects for a peer, because each
 181          * nlm_host is identified by
 182          * (address, protocol, version, server/client)
 183          * We could probably simplify this a little by putting all those
 184          * different NLM rpc_clients into one single nlm_host object.
 185          * This would allow us to have one nlm_host per address.
 186          */
 187         chain = &nlm_hosts[nlm_hash_address(ni->sap)];
 188         hlist_for_each_entry(host, pos, chain, h_hash) {
 189                 if (!rpc_cmp_addr(nlm_addr(host), ni->sap))
 190                         continue;
 191
 192                 /* See if we have an NSM handle for this client */
 193                 if (!nsm)
 194                         nsm = host->h_nsmhandle;
 195
 196                 if (host->h_proto != ni->protocol)
 197                         continue;
 198                 if (host->h_version != ni->version)
 199                         continue;
 200                 if (host->h_server != ni->server)
 201                         continue;
 202                 if (ni->server && ni->src_len != 0 &&
 203                     !rpc_cmp_addr(nlm_srcaddr(host), ni->src_sap))
 204                         continue;
 205
 206                 /* Move to head of hash chain. */
 207                 hlist_del(&host->h_hash);
 208                 hlist_add_head(&host->h_hash, chain);
 209
 210                 nlm_get_host(host);
 211                 dprintk("lockd: nlm_lookup_host found host %s (%s)\n",
 212                                 host->h_name, host->h_addrbuf);
 213                 goto out;
 214         }
 215
 216         host = nlm_alloc_host(ni, nsm);
 217         if (unlikely(host == NULL))
 218                 goto out;
 219
 220         memcpy(nlm_srcaddr(host), ni->src_sap, ni->src_len);
 221         host->h_srcaddrlen = ni->src_len;
 222         hlist_add_head(&host->h_hash, chain);
 223
 224         nrhosts++;
 225
 226         dprintk("lockd: nlm_lookup_host created host %s\n",
 227                         host->h_name);
 228
 229 out:
 230         mutex_unlock(&nlm_host_mutex);
 231         return host;
 232 }
 233
 234 /*
 235  * Destroy an nlm_host and free associated resources
 236  *
 237  * Caller must hold nlm_host_mutex.
 238  */
 239 static void nlm_destroy_host_locked(struct nlm_host *host)
 240 {
 241         struct rpc_clnt *clnt;
 242
 243         dprintk("lockd: destroy host %s\n", host->h_name);
 244
 245         BUG_ON(!list_empty(&host->h_lockowners));
 246         BUG_ON(atomic_read(&host->h_count));
 247
 248         hlist_del_init(&host->h_hash);
 249
 250         nsm_unmonitor(host);
 251         nsm_release(host->h_nsmhandle);
 252
 253         clnt = host->h_rpcclnt;
 254         if (clnt != NULL)
 255                 rpc_shutdown_client(clnt);
 256         kfree(host);
 257
 258         nrhosts--;
 259 }
 260
 261 /**
 262  * nlmclnt_lookup_host - Find an NLM host handle matching a remote server
 263  * @sap: network address of server
 264  * @salen: length of server address
 265  * @protocol: transport protocol to use
 266  * @version: NLM protocol version
 267  * @hostname: '\0'-terminated hostname of server
 268  * @noresvport: 1 if non-privileged port should be used
 269  *
 270  * Returns an nlm_host structure that matches the passed-in
 271  * [server address, transport protocol, NLM version, server hostname].
 272  * If one doesn't already exist in the host cache, a new handle is
 273  * created and returned.
 274  */
 275 struct nlm_host *nlmclnt_lookup_host(const struct sockaddr *sap,
 276                                      const size_t salen,
 277                                      const unsigned short protocol,
 278                                      const u32 version,
 279                                      const char *hostname,
 280                                      int noresvport)
 281 {
 282         struct nlm_lookup_host_info ni = {
 283                 .server         = 0,
 284                 .sap            = sap,
 285                 .salen          = salen,
 286                 .protocol       = protocol,
 287                 .version        = version,
 288                 .hostname       = hostname,
 289                 .hostname_len   = strlen(hostname),
 290                 .noresvport     = noresvport,
 291         };
 292         struct hlist_head *chain;
 293         struct hlist_node *pos;
 294         struct nlm_host *host;
 295         struct nsm_handle *nsm = NULL;
 296
 297         dprintk("lockd: %s(host='%s', vers=%u, proto=%s)\n", __func__,
 298                         (hostname ? hostname : "<none>"), version,
 299                         (protocol == IPPROTO_UDP ? "udp" : "tcp"));
 300
 301         mutex_lock(&nlm_host_mutex);
 302
 303         chain = &nlm_client_hosts[nlm_hash_address(sap)];
 304         hlist_for_each_entry(host, pos, chain, h_hash) {
 305                 if (!rpc_cmp_addr(nlm_addr(host), sap))
 306                         continue;
 307
 308                 /* Same address. Share an NSM handle if we already have one */
 309                 if (nsm == NULL)
 310                         nsm = host->h_nsmhandle;
 311
 312                 if (host->h_proto != protocol)
 313                         continue;
 314                 if (host->h_version != version)
 315                         continue;
 316
 317                 nlm_get_host(host);
 318                 dprintk("lockd: %s found host %s (%s)\n", __func__,
 319                         host->h_name, host->h_addrbuf);
 320                 goto out;
 321         }
 322
 323         host = nlm_alloc_host(&ni, nsm);
 324         if (unlikely(host == NULL))
 325                 goto out;
 326
 327         hlist_add_head(&host->h_hash, chain);
 328         nrhosts++;
 329
 330         dprintk("lockd: %s created host %s (%s)\n", __func__,
 331                 host->h_name, host->h_addrbuf);
 332
 333 out:
 334         mutex_unlock(&nlm_host_mutex);
 335         return host;
 336 }
 337
 338 /**
 339  * nlmclnt_release_host - release client nlm_host
 340  * @host: nlm_host to release
 341  *
 342  */
 343 void nlmclnt_release_host(struct nlm_host *host)
 344 {
 345         if (host == NULL)
 346                 return;
 347
 348         dprintk("lockd: release client host %s\n", host->h_name);
 349
 350         BUG_ON(atomic_read(&host->h_count) < 0);
 351         BUG_ON(host->h_server);
 352
 353         if (atomic_dec_and_test(&host->h_count)) {
 354                 BUG_ON(!list_empty(&host->h_lockowners));
 355                 BUG_ON(!list_empty(&host->h_granted));
 356                 BUG_ON(!list_empty(&host->h_reclaim));
 357
 358                 mutex_lock(&nlm_host_mutex);
 359                 nlm_destroy_host_locked(host);
 360                 mutex_unlock(&nlm_host_mutex);
 361         }
 362 }
 363
 364 /**
 365  * nlmsvc_lookup_host - Find an NLM host handle matching a remote client
 366  * @rqstp: incoming NLM request
 367  * @hostname: name of client host
 368  * @hostname_len: length of client hostname
 369  *
 370  * Returns an nlm_host structure that matches the [client address,
 371  * transport protocol, NLM version, client hostname] of the passed-in
 372  * NLM request.  If one doesn't already exist in the host cache, a
 373  * new handle is created and returned.
 374  *
 375  * Before possibly creating a new nlm_host, construct a sockaddr
 376  * for a specific source address in case the local system has
 377  * multiple network addresses.  The family of the address in
 378  * rq_daddr is guaranteed to be the same as the family of the
 379  * address in rq_addr, so it's safe to use the same family for
 380  * the source address.
 381  */
 382 struct nlm_host *nlmsvc_lookup_host(const struct svc_rqst *rqstp,
 383                                     const char *hostname,
 384                                     const size_t hostname_len)
 385 {
 386         struct hlist_head *chain;
 387         struct hlist_node *pos;
 388         struct nlm_host *host = NULL;
 389         struct nsm_handle *nsm = NULL;
 390         struct sockaddr_in sin = {
 391                 .sin_family     = AF_INET,
 392         };
 393         struct sockaddr_in6 sin6 = {
 394                 .sin6_family    = AF_INET6,
 395         };
 396         struct nlm_lookup_host_info ni = {
 397                 .server         = 1,
 398                 .sap            = svc_addr(rqstp),
 399                 .salen          = rqstp->rq_addrlen,
 400                 .protocol       = rqstp->rq_prot,
 401                 .version        = rqstp->rq_vers,
 402                 .hostname       = hostname,
 403                 .hostname_len   = hostname_len,
 404                 .src_len        = rqstp->rq_addrlen,
 405         };
 406
 407         dprintk("lockd: %s(host='%*s', vers=%u, proto=%s)\n", __func__,
 408                         (int)hostname_len, hostname, rqstp->rq_vers,
 409                         (rqstp->rq_prot == IPPROTO_UDP ? "udp" : "tcp"));
 410
 411         mutex_lock(&nlm_host_mutex);
 412
 413         switch (ni.sap->sa_family) {
 414         case AF_INET:
 415                 sin.sin_addr.s_addr = rqstp->rq_daddr.addr.s_addr;
 416                 ni.src_sap = (struct sockaddr *)&sin;
 417                 break;
 418         case AF_INET6:
 419                 ipv6_addr_copy(&sin6.sin6_addr, &rqstp->rq_daddr.addr6);
 420                 ni.src_sap = (struct sockaddr *)&sin6;
 421                 break;
 422         default:
 423                 dprintk("lockd: %s failed; unrecognized address family\n",
 424                         __func__);
 425                 goto out;
 426         }
 427
 428         if (time_after_eq(jiffies, next_gc))
 429                 nlm_gc_hosts();
 430
 431         chain = &nlm_hosts[nlm_hash_address(ni.sap)];
 432         hlist_for_each_entry(host, pos, chain, h_hash) {
 433                 if (!rpc_cmp_addr(nlm_addr(host), ni.sap))
 434                         continue;
 435
 436                 /* Same address. Share an NSM handle if we already have one */
 437                 if (nsm == NULL)
 438                         nsm = host->h_nsmhandle;
 439
 440                 if (host->h_proto != ni.protocol)
 441                         continue;
 442                 if (host->h_version != ni.version)
 443                         continue;
 444                 if (!rpc_cmp_addr(nlm_srcaddr(host), ni.src_sap))
 445                         continue;
 446
 447                 /* Move to head of hash chain. */
 448                 hlist_del(&host->h_hash);
 449                 hlist_add_head(&host->h_hash, chain);
 450
 451                 nlm_get_host(host);
 452                 dprintk("lockd: %s found host %s (%s)\n",
 453                         __func__, host->h_name, host->h_addrbuf);
 454                 goto out;
 455         }
 456
 457         host = nlm_alloc_host(&ni, nsm);
 458         if (unlikely(host == NULL))
 459                 goto out;
 460
 461         memcpy(nlm_srcaddr(host), ni.src_sap, ni.src_len);
 462         host->h_srcaddrlen = ni.src_len;
 463         hlist_add_head(&host->h_hash, chain);
 464         nrhosts++;
 465
 466         dprintk("lockd: %s created host %s (%s)\n",
 467                 __func__, host->h_name, host->h_addrbuf);
 468
 469 out:
 470         mutex_unlock(&nlm_host_mutex);
 471         return host;
 472 }
 473
 474 /**
 475  * nlmsvc_release_host - release server nlm_host
 476  * @host: nlm_host to release
 477  *
 478  * Host is destroyed later in nlm_gc_host().
 479  */
 480 void nlmsvc_release_host(struct nlm_host *host)
 481 {
 482         if (host == NULL)
 483                 return;
 484
 485         dprintk("lockd: release server host %s\n", host->h_name);
 486
 487         BUG_ON(atomic_read(&host->h_count) < 0);
 488         BUG_ON(!host->h_server);
 489         atomic_dec(&host->h_count);
 490 }
 491
 492 /*
 493  * Create the NLM RPC client for an NLM peer
 494  */
 495 struct rpc_clnt *
 496 nlm_bind_host(struct nlm_host *host)
 497 {
 498         struct rpc_clnt *clnt;
 499
 500         dprintk("lockd: nlm_bind_host %s (%s)\n",
 501                         host->h_name, host->h_addrbuf);
 502
 503         /* Lock host handle */
 504         mutex_lock(&host->h_mutex);
 505
 506         /* If we've already created an RPC client, check whether
 507          * RPC rebind is required
 508          */
 509         if ((clnt = host->h_rpcclnt) != NULL) {
 510                 if (time_after_eq(jiffies, host->h_nextrebind)) {
 511                         rpc_force_rebind(clnt);
 512                         host->h_nextrebind = jiffies + NLM_HOST_REBIND;
 513                         dprintk("lockd: next rebind in %lu jiffies\n",
 514                                         host->h_nextrebind - jiffies);
 515                 }
 516         } else {
 517                 unsigned long increment = nlmsvc_timeout;
 518                 struct rpc_timeout timeparms = {
 519                         .to_initval     = increment,
 520                         .to_increment   = increment,
 521                         .to_maxval      = increment * 6UL,
 522                         .to_retries     = 5U,
 523                 };
 524                 struct rpc_create_args args = {
 525                         .net            = &init_net,
 526                         .protocol       = host->h_proto,
 527                         .address        = nlm_addr(host),
 528                         .addrsize       = host->h_addrlen,
 529                         .timeout        = &timeparms,
 530                         .servername     = host->h_name,
 531                         .program        = &nlm_program,
 532                         .version        = host->h_version,
 533                         .authflavor     = RPC_AUTH_UNIX,
 534                         .flags          = (RPC_CLNT_CREATE_NOPING |
 535                                            RPC_CLNT_CREATE_AUTOBIND),
 536                 };
 537
 538                 /*
 539                  * lockd retries server side blocks automatically so we want
 540                  * those to be soft RPC calls. Client side calls need to be
 541                  * hard RPC tasks.
 542                  */
 543                 if (!host->h_server)
 544                         args.flags |= RPC_CLNT_CREATE_HARDRTRY;
 545                 if (host->h_noresvport)
 546                         args.flags |= RPC_CLNT_CREATE_NONPRIVPORT;
 547                 if (host->h_srcaddrlen)
 548                         args.saddress = nlm_srcaddr(host);
 549
 550                 clnt = rpc_create(&args);
 551                 if (!IS_ERR(clnt))
 552                         host->h_rpcclnt = clnt;
 553                 else {
 554                         printk("lockd: couldn't create RPC handle for %s\n", host->h_name);
 555                         clnt = NULL;
 556                 }
 557         }
 558
 559         mutex_unlock(&host->h_mutex);
 560         return clnt;
 561 }
 562
 563 /*
 564  * Force a portmap lookup of the remote lockd port
 565  */
 566 void
 567 nlm_rebind_host(struct nlm_host *host)
 568 {
 569         dprintk("lockd: rebind host %s\n", host->h_name);
 570         if (host->h_rpcclnt && time_after_eq(jiffies, host->h_nextrebind)) {
 571                 rpc_force_rebind(host->h_rpcclnt);
 572                 host->h_nextrebind = jiffies + NLM_HOST_REBIND;
 573         }
 574 }
 575
 576 /*
 577  * Increment NLM host count
 578  */
 579 struct nlm_host * nlm_get_host(struct nlm_host *host)
 580 {
 581         if (host) {
 582                 dprintk("lockd: get host %s\n", host->h_name);
 583                 atomic_inc(&host->h_count);
 584                 host->h_expires = jiffies + NLM_HOST_EXPIRE;
 585         }
 586         return host;
 587 }
 588
 589 static struct nlm_host *next_host_state(struct hlist_head *cache,
 590                                         struct nsm_handle *nsm,
 591                                         const struct nlm_reboot *info)
 592 {
 593         struct nlm_host *host = NULL;
 594         struct hlist_head *chain;
 595         struct hlist_node *pos;
 596
 597         mutex_lock(&nlm_host_mutex);
 598         for_each_host(host, pos, chain, cache) {
 599                 if (host->h_nsmhandle == nsm
 600                     && host->h_nsmstate != info->state) {
 601                         host->h_nsmstate = info->state;
 602                         host->h_state++;
 603
 604                         nlm_get_host(host);
 605                         mutex_unlock(&nlm_host_mutex);
 606                         goto out;
 607                 }
 608         }
 609 out:
 610         mutex_unlock(&nlm_host_mutex);
 611         return host;
 612 }
 613
 614 /**
 615  * nlm_host_rebooted - Release all resources held by rebooted host
 616  * @info: pointer to decoded results of NLM_SM_NOTIFY call
 617  *
 618  * We were notified that the specified host has rebooted.  Release
 619  * all resources held by that peer.
 620  */
 621 void nlm_host_rebooted(const struct nlm_reboot *info)
 622 {
 623         struct nsm_handle *nsm;
 624         struct nlm_host *host;
 625
 626         nsm = nsm_reboot_lookup(info);
 627         if (unlikely(nsm == NULL))
 628                 return;
 629
 630         /* Mark all hosts tied to this NSM state as having rebooted.
 631          * We run the loop repeatedly, because we drop the host table
 632          * lock for this.
 633          * To avoid processing a host several times, we match the nsmstate.
 634          */
 635         while ((host = next_host_state(nlm_hosts, nsm, info)) != NULL) {
 636                 nlmsvc_free_host_resources(host);
 637                 nlmsvc_release_host(host);
 638         }
 639         while ((host = next_host_state(nlm_client_hosts, nsm, info)) != NULL) {
 640                 nlmclnt_recovery(host);
 641                 nlmclnt_release_host(host);
 642         }
 643
 644         nsm_release(nsm);
 645 }
 646
 647 /*
 648  * Shut down the hosts module.
 649  * Note that this routine is called only at server shutdown time.
 650  */
 651 void
 652 nlm_shutdown_hosts(void)
 653 {
 654         struct hlist_head *chain;
 655         struct hlist_node *pos;
 656         struct nlm_host *host;
 657
 658         dprintk("lockd: shutting down host module\n");
 659         mutex_lock(&nlm_host_mutex);
 660
 661         /* First, make all hosts eligible for gc */
 662         dprintk("lockd: nuking all hosts...\n");
 663         for_each_host(host, pos, chain, nlm_hosts) {
 664                 host->h_expires = jiffies - 1;
 665                 if (host->h_rpcclnt) {
 666                         rpc_shutdown_client(host->h_rpcclnt);
 667                         host->h_rpcclnt = NULL;
 668                 }
 669         }
 670
 671         /* Then, perform a garbage collection pass */
 672         nlm_gc_hosts();
 673         mutex_unlock(&nlm_host_mutex);
 674
 675         /* complain if any hosts are left */
 676         if (nrhosts) {
 677                 printk(KERN_WARNING "lockd: couldn't shutdown host module!\n");
 678                 dprintk("lockd: %d hosts left:\n", nrhosts);
 679                 for_each_host(host, pos, chain, nlm_hosts) {
 680                         dprintk("       %s (cnt %d use %d exp %ld)\n",
 681                                 host->h_name, atomic_read(&host->h_count),
 682                                 host->h_inuse, host->h_expires);
 683                 }
 684         }
 685 }
 686
 687 /*
 688  * Garbage collect any unused NLM hosts.
 689  * This GC combines reference counting for async operations with
 690  * mark & sweep for resources held by remote clients.
 691  */
 692 static void
 693 nlm_gc_hosts(void)
 694 {
 695         struct hlist_head *chain;
 696         struct hlist_node *pos, *next;
 697         struct nlm_host *host;
 698
 699         dprintk("lockd: host garbage collection\n");
 700         for_each_host(host, pos, chain, nlm_hosts)
 701                 host->h_inuse = 0;
 702
 703         /* Mark all hosts that hold locks, blocks or shares */
 704         nlmsvc_mark_resources();
 705
 706         for_each_host_safe(host, pos, next, chain, nlm_hosts) {
 707                 if (atomic_read(&host->h_count) || host->h_inuse
 708                  || time_before(jiffies, host->h_expires)) {
 709                         dprintk("nlm_gc_hosts skipping %s "
 710                                 "(cnt %d use %d exp %ld)\n",
 711                                 host->h_name, atomic_read(&host->h_count),
 712                                 host->h_inuse, host->h_expires);
 713                         continue;
 714                 }
 715                 nlm_destroy_host_locked(host);
 716         }
 717
 718         next_gc = jiffies + NLM_HOST_COLLECT;
 719 }