fs/lockd/host.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * linux/fs/lockd/host.c
   4  *
   5  * Management for NLM peer hosts. The nlm_host struct is shared
   6  * between client and server implementation. The only reason to
   7  * do so is to reduce code bloat.
   8  *
   9  * Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
  10  */
  11
  12 #include <linux/types.h>
  13 #include <linux/slab.h>
  14 #include <linux/in.h>
  15 #include <linux/in6.h>
  16 #include <linux/sunrpc/clnt.h>
  17 #include <linux/sunrpc/addr.h>
  18 #include <linux/sunrpc/svc.h>
  19 #include <linux/lockd/lockd.h>
  20 #include <linux/mutex.h>
  21
  22 #include <linux/sunrpc/svc_xprt.h>
  23
  24 #include <net/ipv6.h>
  25
  26 #include "netns.h"
  27
  28 #define NLMDBG_FACILITY         NLMDBG_HOSTCACHE
  29 #define NLM_HOST_NRHASH         32
  30 #define NLM_HOST_REBIND         (60 * HZ)
  31 #define NLM_HOST_EXPIRE         (300 * HZ)
  32 #define NLM_HOST_COLLECT        (120 * HZ)
  33
  34 static struct hlist_head        nlm_server_hosts[NLM_HOST_NRHASH];
  35 static struct hlist_head        nlm_client_hosts[NLM_HOST_NRHASH];
  36
  37 #define for_each_host(host, chain, table) \
  38         for ((chain) = (table); \
  39              (chain) < (table) + NLM_HOST_NRHASH; ++(chain)) \
  40                 hlist_for_each_entry((host), (chain), h_hash)
  41
  42 #define for_each_host_safe(host, next, chain, table) \
  43         for ((chain) = (table); \
  44              (chain) < (table) + NLM_HOST_NRHASH; ++(chain)) \
  45                 hlist_for_each_entry_safe((host), (next), \
  46                                                 (chain), h_hash)
  47
  48 static unsigned long            nrhosts;
  49 static DEFINE_MUTEX(nlm_host_mutex);
  50
  51 static void                     nlm_gc_hosts(struct net *net);
  52
  53 struct nlm_lookup_host_info {
  54         const int               server;         /* search for server|client */
  55         const struct sockaddr   *sap;           /* address to search for */
  56         const size_t            salen;          /* it's length */
  57         const unsigned short    protocol;       /* transport to search for*/
  58         const u32               version;        /* NLM version to search for */
  59         const char              *hostname;      /* remote's hostname */
  60         const size_t            hostname_len;   /* it's length */
  61         const int               noresvport;     /* use non-priv port */
  62         struct net              *net;           /* network namespace to bind */
  63 };
  64
  65 /*
  66  * Hash function must work well on big- and little-endian platforms
  67  */
  68 static unsigned int __nlm_hash32(const __be32 n)
  69 {
  70         unsigned int hash = (__force u32)n ^ ((__force u32)n >> 16);
  71         return hash ^ (hash >> 8);
  72 }
  73
  74 static unsigned int __nlm_hash_addr4(const struct sockaddr *sap)
  75 {
  76         const struct sockaddr_in *sin = (struct sockaddr_in *)sap;
  77         return __nlm_hash32(sin->sin_addr.s_addr);
  78 }
  79
  80 static unsigned int __nlm_hash_addr6(const struct sockaddr *sap)
  81 {
  82         const struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)sap;
  83         const struct in6_addr addr = sin6->sin6_addr;
  84         return __nlm_hash32(addr.s6_addr32[0]) ^
  85                __nlm_hash32(addr.s6_addr32[1]) ^
  86                __nlm_hash32(addr.s6_addr32[2]) ^
  87                __nlm_hash32(addr.s6_addr32[3]);
  88 }
  89
  90 static unsigned int nlm_hash_address(const struct sockaddr *sap)
  91 {
  92         unsigned int hash;
  93
  94         switch (sap->sa_family) {
  95         case AF_INET:
  96                 hash = __nlm_hash_addr4(sap);
  97                 break;
  98         case AF_INET6:
  99                 hash = __nlm_hash_addr6(sap);
 100                 break;
 101         default:
 102                 hash = 0;
 103         }
 104         return hash & (NLM_HOST_NRHASH - 1);
 105 }
 106
 107 /*
 108  * Allocate and initialize an nlm_host.  Common to both client and server.
 109  */
 110 static struct nlm_host *nlm_alloc_host(struct nlm_lookup_host_info *ni,
 111                                        struct nsm_handle *nsm)
 112 {
 113         struct nlm_host *host = NULL;
 114         unsigned long now = jiffies;
 115
 116         if (nsm != NULL)
 117                 refcount_inc(&nsm->sm_count);
 118         else {
 119                 host = NULL;
 120                 nsm = nsm_get_handle(ni->net, ni->sap, ni->salen,
 121                                         ni->hostname, ni->hostname_len);
 122                 if (unlikely(nsm == NULL)) {
 123                         dprintk("lockd: %s failed; no nsm handle\n",
 124                                 __func__);
 125                         goto out;
 126                 }
 127         }
 128
 129         host = kmalloc(sizeof(*host), GFP_KERNEL);
 130         if (unlikely(host == NULL)) {
 131                 dprintk("lockd: %s failed; no memory\n", __func__);
 132                 nsm_release(nsm);
 133                 goto out;
 134         }
 135
 136         memcpy(nlm_addr(host), ni->sap, ni->salen);
 137         host->h_addrlen    = ni->salen;
 138         rpc_set_port(nlm_addr(host), 0);
 139         host->h_srcaddrlen = 0;
 140
 141         host->h_rpcclnt    = NULL;
 142         host->h_name       = nsm->sm_name;
 143         host->h_version    = ni->version;
 144         host->h_proto      = ni->protocol;
 145         host->h_reclaiming = 0;
 146         host->h_server     = ni->server;
 147         host->h_noresvport = ni->noresvport;
 148         host->h_inuse      = 0;
 149         init_waitqueue_head(&host->h_gracewait);
 150         init_rwsem(&host->h_rwsem);
 151         host->h_state      = 0;
 152         host->h_nsmstate   = 0;
 153         host->h_pidcount   = 0;
 154         refcount_set(&host->h_count, 1);
 155         mutex_init(&host->h_mutex);
 156         host->h_nextrebind = now + NLM_HOST_REBIND;
 157         host->h_expires    = now + NLM_HOST_EXPIRE;
 158         INIT_LIST_HEAD(&host->h_lockowners);
 159         spin_lock_init(&host->h_lock);
 160         INIT_LIST_HEAD(&host->h_granted);
 161         INIT_LIST_HEAD(&host->h_reclaim);
 162         host->h_nsmhandle  = nsm;
 163         host->h_addrbuf    = nsm->sm_addrbuf;
 164         host->net          = ni->net;
 165         strlcpy(host->nodename, utsname()->nodename, sizeof(host->nodename));
 166
 167 out:
 168         return host;
 169 }
 170
 171 /*
 172  * Destroy an nlm_host and free associated resources
 173  *
 174  * Caller must hold nlm_host_mutex.
 175  */
 176 static void nlm_destroy_host_locked(struct nlm_host *host)
 177 {
 178         struct rpc_clnt *clnt;
 179         struct lockd_net *ln = net_generic(host->net, lockd_net_id);
 180
 181         dprintk("lockd: destroy host %s\n", host->h_name);
 182
 183         hlist_del_init(&host->h_hash);
 184
 185         nsm_unmonitor(host);
 186         nsm_release(host->h_nsmhandle);
 187
 188         clnt = host->h_rpcclnt;
 189         if (clnt != NULL)
 190                 rpc_shutdown_client(clnt);
 191         kfree(host);
 192
 193         ln->nrhosts--;
 194         nrhosts--;
 195 }
 196
 197 /**
 198  * nlmclnt_lookup_host - Find an NLM host handle matching a remote server
 199  * @sap: network address of server
 200  * @salen: length of server address
 201  * @protocol: transport protocol to use
 202  * @version: NLM protocol version
 203  * @hostname: '\0'-terminated hostname of server
 204  * @noresvport: 1 if non-privileged port should be used
 205  *
 206  * Returns an nlm_host structure that matches the passed-in
 207  * [server address, transport protocol, NLM version, server hostname].
 208  * If one doesn't already exist in the host cache, a new handle is
 209  * created and returned.
 210  */
 211 struct nlm_host *nlmclnt_lookup_host(const struct sockaddr *sap,
 212                                      const size_t salen,
 213                                      const unsigned short protocol,
 214                                      const u32 version,
 215                                      const char *hostname,
 216                                      int noresvport,
 217                                      struct net *net)
 218 {
 219         struct nlm_lookup_host_info ni = {
 220                 .server         = 0,
 221                 .sap            = sap,
 222                 .salen          = salen,
 223                 .protocol       = protocol,
 224                 .version        = version,
 225                 .hostname       = hostname,
 226                 .hostname_len   = strlen(hostname),
 227                 .noresvport     = noresvport,
 228                 .net            = net,
 229         };
 230         struct hlist_head *chain;
 231         struct nlm_host *host;
 232         struct nsm_handle *nsm = NULL;
 233         struct lockd_net *ln = net_generic(net, lockd_net_id);
 234
 235         dprintk("lockd: %s(host='%s', vers=%u, proto=%s)\n", __func__,
 236                         (hostname ? hostname : "<none>"), version,
 237                         (protocol == IPPROTO_UDP ? "udp" : "tcp"));
 238
 239         mutex_lock(&nlm_host_mutex);
 240
 241         chain = &nlm_client_hosts[nlm_hash_address(sap)];
 242         hlist_for_each_entry(host, chain, h_hash) {
 243                 if (host->net != net)
 244                         continue;
 245                 if (!rpc_cmp_addr(nlm_addr(host), sap))
 246                         continue;
 247
 248                 /* Same address. Share an NSM handle if we already have one */
 249                 if (nsm == NULL)
 250                         nsm = host->h_nsmhandle;
 251
 252                 if (host->h_proto != protocol)
 253                         continue;
 254                 if (host->h_version != version)
 255                         continue;
 256
 257                 nlm_get_host(host);
 258                 dprintk("lockd: %s found host %s (%s)\n", __func__,
 259                         host->h_name, host->h_addrbuf);
 260                 goto out;
 261         }
 262
 263         host = nlm_alloc_host(&ni, nsm);
 264         if (unlikely(host == NULL))
 265                 goto out;
 266
 267         hlist_add_head(&host->h_hash, chain);
 268         ln->nrhosts++;
 269         nrhosts++;
 270
 271         dprintk("lockd: %s created host %s (%s)\n", __func__,
 272                 host->h_name, host->h_addrbuf);
 273
 274 out:
 275         mutex_unlock(&nlm_host_mutex);
 276         return host;
 277 }
 278
 279 /**
 280  * nlmclnt_release_host - release client nlm_host
 281  * @host: nlm_host to release
 282  *
 283  */
 284 void nlmclnt_release_host(struct nlm_host *host)
 285 {
 286         if (host == NULL)
 287                 return;
 288
 289         dprintk("lockd: release client host %s\n", host->h_name);
 290
 291         WARN_ON_ONCE(host->h_server);
 292
 293         if (refcount_dec_and_test(&host->h_count)) {
 294                 WARN_ON_ONCE(!list_empty(&host->h_lockowners));
 295                 WARN_ON_ONCE(!list_empty(&host->h_granted));
 296                 WARN_ON_ONCE(!list_empty(&host->h_reclaim));
 297
 298                 mutex_lock(&nlm_host_mutex);
 299                 nlm_destroy_host_locked(host);
 300                 mutex_unlock(&nlm_host_mutex);
 301         }
 302 }
 303
 304 /**
 305  * nlmsvc_lookup_host - Find an NLM host handle matching a remote client
 306  * @rqstp: incoming NLM request
 307  * @hostname: name of client host
 308  * @hostname_len: length of client hostname
 309  *
 310  * Returns an nlm_host structure that matches the [client address,
 311  * transport protocol, NLM version, client hostname] of the passed-in
 312  * NLM request.  If one doesn't already exist in the host cache, a
 313  * new handle is created and returned.
 314  *
 315  * Before possibly creating a new nlm_host, construct a sockaddr
 316  * for a specific source address in case the local system has
 317  * multiple network addresses.  The family of the address in
 318  * rq_daddr is guaranteed to be the same as the family of the
 319  * address in rq_addr, so it's safe to use the same family for
 320  * the source address.
 321  */
 322 struct nlm_host *nlmsvc_lookup_host(const struct svc_rqst *rqstp,
 323                                     const char *hostname,
 324                                     const size_t hostname_len)
 325 {
 326         struct hlist_head *chain;
 327         struct nlm_host *host = NULL;
 328         struct nsm_handle *nsm = NULL;
 329         struct sockaddr *src_sap = svc_daddr(rqstp);
 330         size_t src_len = rqstp->rq_daddrlen;
 331         struct net *net = SVC_NET(rqstp);
 332         struct nlm_lookup_host_info ni = {
 333                 .server         = 1,
 334                 .sap            = svc_addr(rqstp),
 335                 .salen          = rqstp->rq_addrlen,
 336                 .protocol       = rqstp->rq_prot,
 337                 .version        = rqstp->rq_vers,
 338                 .hostname       = hostname,
 339                 .hostname_len   = hostname_len,
 340                 .net            = net,
 341         };
 342         struct lockd_net *ln = net_generic(net, lockd_net_id);
 343
 344         dprintk("lockd: %s(host='%.*s', vers=%u, proto=%s)\n", __func__,
 345                         (int)hostname_len, hostname, rqstp->rq_vers,
 346                         (rqstp->rq_prot == IPPROTO_UDP ? "udp" : "tcp"));
 347
 348         mutex_lock(&nlm_host_mutex);
 349
 350         if (time_after_eq(jiffies, ln->next_gc))
 351                 nlm_gc_hosts(net);
 352
 353         chain = &nlm_server_hosts[nlm_hash_address(ni.sap)];
 354         hlist_for_each_entry(host, chain, h_hash) {
 355                 if (host->net != net)
 356                         continue;
 357                 if (!rpc_cmp_addr(nlm_addr(host), ni.sap))
 358                         continue;
 359
 360                 /* Same address. Share an NSM handle if we already have one */
 361                 if (nsm == NULL)
 362                         nsm = host->h_nsmhandle;
 363
 364                 if (host->h_proto != ni.protocol)
 365                         continue;
 366                 if (host->h_version != ni.version)
 367                         continue;
 368                 if (!rpc_cmp_addr(nlm_srcaddr(host), src_sap))
 369                         continue;
 370
 371                 /* Move to head of hash chain. */
 372                 hlist_del(&host->h_hash);
 373                 hlist_add_head(&host->h_hash, chain);
 374
 375                 nlm_get_host(host);
 376                 dprintk("lockd: %s found host %s (%s)\n",
 377                         __func__, host->h_name, host->h_addrbuf);
 378                 goto out;
 379         }
 380
 381         host = nlm_alloc_host(&ni, nsm);
 382         if (unlikely(host == NULL))
 383                 goto out;
 384
 385         memcpy(nlm_srcaddr(host), src_sap, src_len);
 386         host->h_srcaddrlen = src_len;
 387         hlist_add_head(&host->h_hash, chain);
 388         ln->nrhosts++;
 389         nrhosts++;
 390
 391         refcount_inc(&host->h_count);
 392
 393         dprintk("lockd: %s created host %s (%s)\n",
 394                 __func__, host->h_name, host->h_addrbuf);
 395
 396 out:
 397         mutex_unlock(&nlm_host_mutex);
 398         return host;
 399 }
 400
 401 /**
 402  * nlmsvc_release_host - release server nlm_host
 403  * @host: nlm_host to release
 404  *
 405  * Host is destroyed later in nlm_gc_host().
 406  */
 407 void nlmsvc_release_host(struct nlm_host *host)
 408 {
 409         if (host == NULL)
 410                 return;
 411
 412         dprintk("lockd: release server host %s\n", host->h_name);
 413
 414         WARN_ON_ONCE(!host->h_server);
 415         refcount_dec(&host->h_count);
 416 }
 417
 418 /*
 419  * Create the NLM RPC client for an NLM peer
 420  */
 421 struct rpc_clnt *
 422 nlm_bind_host(struct nlm_host *host)
 423 {
 424         struct rpc_clnt *clnt;
 425
 426         dprintk("lockd: nlm_bind_host %s (%s)\n",
 427                         host->h_name, host->h_addrbuf);
 428
 429         /* Lock host handle */
 430         mutex_lock(&host->h_mutex);
 431
 432         /* If we've already created an RPC client, check whether
 433          * RPC rebind is required
 434          */
 435         if ((clnt = host->h_rpcclnt) != NULL) {
 436                 if (time_after_eq(jiffies, host->h_nextrebind)) {
 437                         rpc_force_rebind(clnt);
 438                         host->h_nextrebind = jiffies + NLM_HOST_REBIND;
 439                         dprintk("lockd: next rebind in %lu jiffies\n",
 440                                         host->h_nextrebind - jiffies);
 441                 }
 442         } else {
 443                 unsigned long increment = nlmsvc_timeout;
 444                 struct rpc_timeout timeparms = {
 445                         .to_initval     = increment,
 446                         .to_increment   = increment,
 447                         .to_maxval      = increment * 6UL,
 448                         .to_retries     = 5U,
 449                 };
 450                 struct rpc_create_args args = {
 451                         .net            = host->net,
 452                         .protocol       = host->h_proto,
 453                         .address        = nlm_addr(host),
 454                         .addrsize       = host->h_addrlen,
 455                         .timeout        = &timeparms,
 456                         .servername     = host->h_name,
 457                         .program        = &nlm_program,
 458                         .version        = host->h_version,
 459                         .authflavor     = RPC_AUTH_UNIX,
 460                         .flags          = (RPC_CLNT_CREATE_NOPING |
 461                                            RPC_CLNT_CREATE_AUTOBIND),
 462                 };
 463
 464                 /*
 465                  * lockd retries server side blocks automatically so we want
 466                  * those to be soft RPC calls. Client side calls need to be
 467                  * hard RPC tasks.
 468                  */
 469                 if (!host->h_server)
 470                         args.flags |= RPC_CLNT_CREATE_HARDRTRY;
 471                 if (host->h_noresvport)
 472                         args.flags |= RPC_CLNT_CREATE_NONPRIVPORT;
 473                 if (host->h_srcaddrlen)
 474                         args.saddress = nlm_srcaddr(host);
 475
 476                 clnt = rpc_create(&args);
 477                 if (!IS_ERR(clnt))
 478                         host->h_rpcclnt = clnt;
 479                 else {
 480                         printk("lockd: couldn't create RPC handle for %s\n", host->h_name);
 481                         clnt = NULL;
 482                 }
 483         }
 484
 485         mutex_unlock(&host->h_mutex);
 486         return clnt;
 487 }
 488
 489 /*
 490  * Force a portmap lookup of the remote lockd port
 491  */
 492 void
 493 nlm_rebind_host(struct nlm_host *host)
 494 {
 495         dprintk("lockd: rebind host %s\n", host->h_name);
 496         if (host->h_rpcclnt && time_after_eq(jiffies, host->h_nextrebind)) {
 497                 rpc_force_rebind(host->h_rpcclnt);
 498                 host->h_nextrebind = jiffies + NLM_HOST_REBIND;
 499         }
 500 }
 501
 502 /*
 503  * Increment NLM host count
 504  */
 505 struct nlm_host * nlm_get_host(struct nlm_host *host)
 506 {
 507         if (host) {
 508                 dprintk("lockd: get host %s\n", host->h_name);
 509                 refcount_inc(&host->h_count);
 510                 host->h_expires = jiffies + NLM_HOST_EXPIRE;
 511         }
 512         return host;
 513 }
 514
 515 static struct nlm_host *next_host_state(struct hlist_head *cache,
 516                                         struct nsm_handle *nsm,
 517                                         const struct nlm_reboot *info)
 518 {
 519         struct nlm_host *host;
 520         struct hlist_head *chain;
 521
 522         mutex_lock(&nlm_host_mutex);
 523         for_each_host(host, chain, cache) {
 524                 if (host->h_nsmhandle == nsm
 525                     && host->h_nsmstate != info->state) {
 526                         host->h_nsmstate = info->state;
 527                         host->h_state++;
 528
 529                         nlm_get_host(host);
 530                         mutex_unlock(&nlm_host_mutex);
 531                         return host;
 532                 }
 533         }
 534
 535         mutex_unlock(&nlm_host_mutex);
 536         return NULL;
 537 }
 538
 539 /**
 540  * nlm_host_rebooted - Release all resources held by rebooted host
 541  * @net:  network namespace
 542  * @info: pointer to decoded results of NLM_SM_NOTIFY call
 543  *
 544  * We were notified that the specified host has rebooted.  Release
 545  * all resources held by that peer.
 546  */
 547 void nlm_host_rebooted(const struct net *net, const struct nlm_reboot *info)
 548 {
 549         struct nsm_handle *nsm;
 550         struct nlm_host *host;
 551
 552         nsm = nsm_reboot_lookup(net, info);
 553         if (unlikely(nsm == NULL))
 554                 return;
 555
 556         /* Mark all hosts tied to this NSM state as having rebooted.
 557          * We run the loop repeatedly, because we drop the host table
 558          * lock for this.
 559          * To avoid processing a host several times, we match the nsmstate.
 560          */
 561         while ((host = next_host_state(nlm_server_hosts, nsm, info)) != NULL) {
 562                 nlmsvc_free_host_resources(host);
 563                 nlmsvc_release_host(host);
 564         }
 565         while ((host = next_host_state(nlm_client_hosts, nsm, info)) != NULL) {
 566                 nlmclnt_recovery(host);
 567                 nlmclnt_release_host(host);
 568         }
 569
 570         nsm_release(nsm);
 571 }
 572
 573 static void nlm_complain_hosts(struct net *net)
 574 {
 575         struct hlist_head *chain;
 576         struct nlm_host *host;
 577
 578         if (net) {
 579                 struct lockd_net *ln = net_generic(net, lockd_net_id);
 580
 581                 if (ln->nrhosts == 0)
 582                         return;
 583                 pr_warn("lockd: couldn't shutdown host module for net %x!\n",
 584                         net->ns.inum);
 585                 dprintk("lockd: %lu hosts left in net %x:\n", ln->nrhosts,
 586                         net->ns.inum);
 587         } else {
 588                 if (nrhosts == 0)
 589                         return;
 590                 printk(KERN_WARNING "lockd: couldn't shutdown host module!\n");
 591                 dprintk("lockd: %lu hosts left:\n", nrhosts);
 592         }
 593
 594         for_each_host(host, chain, nlm_server_hosts) {
 595                 if (net && host->net != net)
 596                         continue;
 597                 dprintk("       %s (cnt %d use %d exp %ld net %x)\n",
 598                         host->h_name, refcount_read(&host->h_count),
 599                         host->h_inuse, host->h_expires, host->net->ns.inum);
 600         }
 601 }
 602
 603 void
 604 nlm_shutdown_hosts_net(struct net *net)
 605 {
 606         struct hlist_head *chain;
 607         struct nlm_host *host;
 608
 609         mutex_lock(&nlm_host_mutex);
 610
 611         /* First, make all hosts eligible for gc */
 612         dprintk("lockd: nuking all hosts in net %x...\n",
 613                 net ? net->ns.inum : 0);
 614         for_each_host(host, chain, nlm_server_hosts) {
 615                 if (net && host->net != net)
 616                         continue;
 617                 host->h_expires = jiffies - 1;
 618                 if (host->h_rpcclnt) {
 619                         rpc_shutdown_client(host->h_rpcclnt);
 620                         host->h_rpcclnt = NULL;
 621                 }
 622         }
 623
 624         /* Then, perform a garbage collection pass */
 625         nlm_gc_hosts(net);
 626         nlm_complain_hosts(net);
 627         mutex_unlock(&nlm_host_mutex);
 628 }
 629
 630 /*
 631  * Shut down the hosts module.
 632  * Note that this routine is called only at server shutdown time.
 633  */
 634 void
 635 nlm_shutdown_hosts(void)
 636 {
 637         dprintk("lockd: shutting down host module\n");
 638         nlm_shutdown_hosts_net(NULL);
 639 }
 640
 641 /*
 642  * Garbage collect any unused NLM hosts.
 643  * This GC combines reference counting for async operations with
 644  * mark & sweep for resources held by remote clients.
 645  */
 646 static void
 647 nlm_gc_hosts(struct net *net)
 648 {
 649         struct hlist_head *chain;
 650         struct hlist_node *next;
 651         struct nlm_host *host;
 652
 653         dprintk("lockd: host garbage collection for net %x\n",
 654                 net ? net->ns.inum : 0);
 655         for_each_host(host, chain, nlm_server_hosts) {
 656                 if (net && host->net != net)
 657                         continue;
 658                 host->h_inuse = 0;
 659         }
 660
 661         /* Mark all hosts that hold locks, blocks or shares */
 662         nlmsvc_mark_resources(net);
 663
 664         for_each_host_safe(host, next, chain, nlm_server_hosts) {
 665                 if (net && host->net != net)
 666                         continue;
 667                 if (host->h_inuse || time_before(jiffies, host->h_expires)) {
 668                         dprintk("nlm_gc_hosts skipping %s "
 669                                 "(cnt %d use %d exp %ld net %x)\n",
 670                                 host->h_name, refcount_read(&host->h_count),
 671                                 host->h_inuse, host->h_expires,
 672                                 host->net->ns.inum);
 673                         continue;
 674                 }
 675                 if (refcount_dec_if_one(&host->h_count))
 676                         nlm_destroy_host_locked(host);
 677         }
 678
 679         if (net) {
 680                 struct lockd_net *ln = net_generic(net, lockd_net_id);
 681
 682                 ln->next_gc = jiffies + NLM_HOST_COLLECT;
 683         }
 684 }