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