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   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/lockd/sm_inter.h>
  19 #include <linux/mutex.h>
  20
  21 #include <net/ipv6.h>
  22
  23 #define NLMDBG_FACILITY         NLMDBG_HOSTCACHE
  24 #define NLM_HOST_NRHASH         32
  25 #define NLM_HOST_REBIND         (60 * HZ)
  26 #define NLM_HOST_EXPIRE         (300 * HZ)
  27 #define NLM_HOST_COLLECT        (120 * HZ)
  28
  29 static struct hlist_head        nlm_hosts[NLM_HOST_NRHASH];
  30 static unsigned long            next_gc;
  31 static int                      nrhosts;
  32 static DEFINE_MUTEX(nlm_host_mutex);
  33
  34 static void                     nlm_gc_hosts(void);
  35 static struct nsm_handle        *nsm_find(const struct sockaddr *sap,
  36                                                 const size_t salen,
  37                                                 const char *hostname,
  38                                                 const size_t hostname_len,
  39                                                 const int create);
  40
  41 struct nlm_lookup_host_info {
  42         const int               server;         /* search for server|client */
  43         const struct sockaddr   *sap;           /* address to search for */
  44         const size_t            salen;          /* it's length */
  45         const unsigned short    protocol;       /* transport to search for*/
  46         const u32               version;        /* NLM version to search for */
  47         const char              *hostname;      /* remote's hostname */
  48         const size_t            hostname_len;   /* it's length */
  49         const struct sockaddr   *src_sap;       /* our address (optional) */
  50         const size_t            src_len;        /* it's length */
  51 };
  52
  53 /*
  54  * Hash function must work well on big- and little-endian platforms
  55  */
  56 static unsigned int __nlm_hash32(const __be32 n)
  57 {
  58         unsigned int hash = (__force u32)n ^ ((__force u32)n >> 16);
  59         return hash ^ (hash >> 8);
  60 }
  61
  62 static unsigned int __nlm_hash_addr4(const struct sockaddr *sap)
  63 {
  64         const struct sockaddr_in *sin = (struct sockaddr_in *)sap;
  65         return __nlm_hash32(sin->sin_addr.s_addr);
  66 }
  67
  68 static unsigned int __nlm_hash_addr6(const struct sockaddr *sap)
  69 {
  70         const struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)sap;
  71         const struct in6_addr addr = sin6->sin6_addr;
  72         return __nlm_hash32(addr.s6_addr32[0]) ^
  73                __nlm_hash32(addr.s6_addr32[1]) ^
  74                __nlm_hash32(addr.s6_addr32[2]) ^
  75                __nlm_hash32(addr.s6_addr32[3]);
  76 }
  77
  78 static unsigned int nlm_hash_address(const struct sockaddr *sap)
  79 {
  80         unsigned int hash;
  81
  82         switch (sap->sa_family) {
  83         case AF_INET:
  84                 hash = __nlm_hash_addr4(sap);
  85                 break;
  86         case AF_INET6:
  87                 hash = __nlm_hash_addr6(sap);
  88                 break;
  89         default:
  90                 hash = 0;
  91         }
  92         return hash & (NLM_HOST_NRHASH - 1);
  93 }
  94
  95 static void nlm_clear_port(struct sockaddr *sap)
  96 {
  97         switch (sap->sa_family) {
  98         case AF_INET:
  99                 ((struct sockaddr_in *)sap)->sin_port = 0;
 100                 break;
 101         case AF_INET6:
 102                 ((struct sockaddr_in6 *)sap)->sin6_port = 0;
 103                 break;
 104         }
 105 }
 106
 107 static void nlm_display_address(const struct sockaddr *sap,
 108                                 char *buf, const size_t len)
 109 {
 110         const struct sockaddr_in *sin = (struct sockaddr_in *)sap;
 111         const struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)sap;
 112
 113         switch (sap->sa_family) {
 114         case AF_UNSPEC:
 115                 snprintf(buf, len, "unspecified");
 116                 break;
 117         case AF_INET:
 118                 snprintf(buf, len, NIPQUAD_FMT, NIPQUAD(sin->sin_addr.s_addr));
 119                 break;
 120         case AF_INET6:
 121                 if (ipv6_addr_v4mapped(&sin6->sin6_addr))
 122                         snprintf(buf, len, NIPQUAD_FMT,
 123                                  NIPQUAD(sin6->sin6_addr.s6_addr32[3]));
 124                 else
 125                         snprintf(buf, len, NIP6_FMT, NIP6(sin6->sin6_addr));
 126                 break;
 127         default:
 128                 snprintf(buf, len, "unsupported address family");
 129                 break;
 130         }
 131 }
 132
 133 /*
 134  * Common host lookup routine for server & client
 135  */
 136 static struct nlm_host *nlm_lookup_host(struct nlm_lookup_host_info *ni)
 137 {
 138         struct hlist_head *chain;
 139         struct hlist_node *pos;
 140         struct nlm_host *host;
 141         struct nsm_handle *nsm = NULL;
 142
 143         mutex_lock(&nlm_host_mutex);
 144
 145         if (time_after_eq(jiffies, next_gc))
 146                 nlm_gc_hosts();
 147
 148         /* We may keep several nlm_host objects for a peer, because each
 149          * nlm_host is identified by
 150          * (address, protocol, version, server/client)
 151          * We could probably simplify this a little by putting all those
 152          * different NLM rpc_clients into one single nlm_host object.
 153          * This would allow us to have one nlm_host per address.
 154          */
 155         chain = &nlm_hosts[nlm_hash_address(ni->sap)];
 156         hlist_for_each_entry(host, pos, chain, h_hash) {
 157                 if (!nlm_cmp_addr(nlm_addr(host), ni->sap))
 158                         continue;
 159
 160                 /* See if we have an NSM handle for this client */
 161                 if (!nsm)
 162                         nsm = host->h_nsmhandle;
 163
 164                 if (host->h_proto != ni->protocol)
 165                         continue;
 166                 if (host->h_version != ni->version)
 167                         continue;
 168                 if (host->h_server != ni->server)
 169                         continue;
 170                 if (!nlm_cmp_addr(nlm_srcaddr(host), ni->src_sap))
 171                         continue;
 172
 173                 /* Move to head of hash chain. */
 174                 hlist_del(&host->h_hash);
 175                 hlist_add_head(&host->h_hash, chain);
 176
 177                 nlm_get_host(host);
 178                 dprintk("lockd: nlm_lookup_host found host %s (%s)\n",
 179                                 host->h_name, host->h_addrbuf);
 180                 goto out;
 181         }
 182
 183         /*
 184          * The host wasn't in our hash table.  If we don't
 185          * have an NSM handle for it yet, create one.
 186          */
 187         if (nsm)
 188                 atomic_inc(&nsm->sm_count);
 189         else {
 190                 host = NULL;
 191                 nsm = nsm_find(ni->sap, ni->salen,
 192                                 ni->hostname, ni->hostname_len, 1);
 193                 if (!nsm) {
 194                         dprintk("lockd: nlm_lookup_host failed; "
 195                                 "no nsm handle\n");
 196                         goto out;
 197                 }
 198         }
 199
 200         host = kzalloc(sizeof(*host), GFP_KERNEL);
 201         if (!host) {
 202                 nsm_release(nsm);
 203                 dprintk("lockd: nlm_lookup_host failed; no memory\n");
 204                 goto out;
 205         }
 206         host->h_name       = nsm->sm_name;
 207         memcpy(nlm_addr(host), ni->sap, ni->salen);
 208         host->h_addrlen = ni->salen;
 209         nlm_clear_port(nlm_addr(host));
 210         memcpy(nlm_srcaddr(host), ni->src_sap, ni->src_len);
 211         host->h_version    = ni->version;
 212         host->h_proto      = ni->protocol;
 213         host->h_rpcclnt    = NULL;
 214         mutex_init(&host->h_mutex);
 215         host->h_nextrebind = jiffies + NLM_HOST_REBIND;
 216         host->h_expires    = jiffies + NLM_HOST_EXPIRE;
 217         atomic_set(&host->h_count, 1);
 218         init_waitqueue_head(&host->h_gracewait);
 219         init_rwsem(&host->h_rwsem);
 220         host->h_state      = 0;                 /* pseudo NSM state */
 221         host->h_nsmstate   = 0;                 /* real NSM state */
 222         host->h_nsmhandle  = nsm;
 223         host->h_server     = ni->server;
 224         hlist_add_head(&host->h_hash, chain);
 225         INIT_LIST_HEAD(&host->h_lockowners);
 226         spin_lock_init(&host->h_lock);
 227         INIT_LIST_HEAD(&host->h_granted);
 228         INIT_LIST_HEAD(&host->h_reclaim);
 229
 230         nrhosts++;
 231
 232         nlm_display_address((struct sockaddr *)&host->h_addr,
 233                                 host->h_addrbuf, sizeof(host->h_addrbuf));
 234         nlm_display_address((struct sockaddr *)&host->h_srcaddr,
 235                                 host->h_srcaddrbuf, sizeof(host->h_srcaddrbuf));
 236
 237         dprintk("lockd: nlm_lookup_host created host %s\n",
 238                         host->h_name);
 239
 240 out:
 241         mutex_unlock(&nlm_host_mutex);
 242         return host;
 243 }
 244
 245 /*
 246  * Destroy a host
 247  */
 248 static void
 249 nlm_destroy_host(struct nlm_host *host)
 250 {
 251         struct rpc_clnt *clnt;
 252
 253         BUG_ON(!list_empty(&host->h_lockowners));
 254         BUG_ON(atomic_read(&host->h_count));
 255
 256         /*
 257          * Release NSM handle and unmonitor host.
 258          */
 259         nsm_unmonitor(host);
 260
 261         clnt = host->h_rpcclnt;
 262         if (clnt != NULL)
 263                 rpc_shutdown_client(clnt);
 264         kfree(host);
 265 }
 266
 267 /**
 268  * nlmclnt_lookup_host - Find an NLM host handle matching a remote server
 269  * @sap: network address of server
 270  * @salen: length of server address
 271  * @protocol: transport protocol to use
 272  * @version: NLM protocol version
 273  * @hostname: '\0'-terminated hostname of server
 274  *
 275  * Returns an nlm_host structure that matches the passed-in
 276  * [server address, transport protocol, NLM version, server hostname].
 277  * If one doesn't already exist in the host cache, a new handle is
 278  * created and returned.
 279  */
 280 struct nlm_host *nlmclnt_lookup_host(const struct sockaddr *sap,
 281                                      const size_t salen,
 282                                      const unsigned short protocol,
 283                                      const u32 version, const char *hostname)
 284 {
 285         const struct sockaddr source = {
 286                 .sa_family      = AF_UNSPEC,
 287         };
 288         struct nlm_lookup_host_info ni = {
 289                 .server         = 0,
 290                 .sap            = sap,
 291                 .salen          = salen,
 292                 .protocol       = protocol,
 293                 .version        = version,
 294                 .hostname       = hostname,
 295                 .hostname_len   = strlen(hostname),
 296                 .src_sap        = &source,
 297                 .src_len        = sizeof(source),
 298         };
 299
 300         dprintk("lockd: %s(host='%s', vers=%u, proto=%s)\n", __func__,
 301                         (hostname ? hostname : "<none>"), version,
 302                         (protocol == IPPROTO_UDP ? "udp" : "tcp"));
 303
 304         return nlm_lookup_host(&ni);
 305 }
 306
 307 /**
 308  * nlmsvc_lookup_host - Find an NLM host handle matching a remote client
 309  * @rqstp: incoming NLM request
 310  * @hostname: name of client host
 311  * @hostname_len: length of client hostname
 312  *
 313  * Returns an nlm_host structure that matches the [client address,
 314  * transport protocol, NLM version, client hostname] of the passed-in
 315  * NLM request.  If one doesn't already exist in the host cache, a
 316  * new handle is created and returned.
 317  *
 318  * Before possibly creating a new nlm_host, construct a sockaddr
 319  * for a specific source address in case the local system has
 320  * multiple network addresses.  The family of the address in
 321  * rq_daddr is guaranteed to be the same as the family of the
 322  * address in rq_addr, so it's safe to use the same family for
 323  * the source address.
 324  */
 325 struct nlm_host *nlmsvc_lookup_host(const struct svc_rqst *rqstp,
 326                                     const char *hostname,
 327                                     const size_t hostname_len)
 328 {
 329         struct sockaddr_in sin = {
 330                 .sin_family     = AF_INET,
 331         };
 332         struct sockaddr_in6 sin6 = {
 333                 .sin6_family    = AF_INET6,
 334         };
 335         struct nlm_lookup_host_info ni = {
 336                 .server         = 1,
 337                 .sap            = svc_addr(rqstp),
 338                 .salen          = rqstp->rq_addrlen,
 339                 .protocol       = rqstp->rq_prot,
 340                 .version        = rqstp->rq_vers,
 341                 .hostname       = hostname,
 342                 .hostname_len   = hostname_len,
 343                 .src_len        = rqstp->rq_addrlen,
 344         };
 345
 346         dprintk("lockd: %s(host='%*s', vers=%u, proto=%s)\n", __func__,
 347                         (int)hostname_len, hostname, rqstp->rq_vers,
 348                         (rqstp->rq_prot == IPPROTO_UDP ? "udp" : "tcp"));
 349
 350         switch (ni.sap->sa_family) {
 351         case AF_INET:
 352                 sin.sin_addr.s_addr = rqstp->rq_daddr.addr.s_addr;
 353                 ni.src_sap = (struct sockaddr *)&sin;
 354                 break;
 355         case AF_INET6:
 356                 ipv6_addr_copy(&sin6.sin6_addr, &rqstp->rq_daddr.addr6);
 357                 ni.src_sap = (struct sockaddr *)&sin6;
 358                 break;
 359         default:
 360                 return NULL;
 361         }
 362
 363         return nlm_lookup_host(&ni);
 364 }
 365
 366 /*
 367  * Create the NLM RPC client for an NLM peer
 368  */
 369 struct rpc_clnt *
 370 nlm_bind_host(struct nlm_host *host)
 371 {
 372         struct rpc_clnt *clnt;
 373
 374         dprintk("lockd: nlm_bind_host %s (%s), my addr=%s\n",
 375                         host->h_name, host->h_addrbuf, host->h_srcaddrbuf);
 376
 377         /* Lock host handle */
 378         mutex_lock(&host->h_mutex);
 379
 380         /* If we've already created an RPC client, check whether
 381          * RPC rebind is required
 382          */
 383         if ((clnt = host->h_rpcclnt) != NULL) {
 384                 if (time_after_eq(jiffies, host->h_nextrebind)) {
 385                         rpc_force_rebind(clnt);
 386                         host->h_nextrebind = jiffies + NLM_HOST_REBIND;
 387                         dprintk("lockd: next rebind in %lu jiffies\n",
 388                                         host->h_nextrebind - jiffies);
 389                 }
 390         } else {
 391                 unsigned long increment = nlmsvc_timeout;
 392                 struct rpc_timeout timeparms = {
 393                         .to_initval     = increment,
 394                         .to_increment   = increment,
 395                         .to_maxval      = increment * 6UL,
 396                         .to_retries     = 5U,
 397                 };
 398                 struct rpc_create_args args = {
 399                         .protocol       = host->h_proto,
 400                         .address        = nlm_addr(host),
 401                         .addrsize       = host->h_addrlen,
 402                         .saddress       = nlm_srcaddr(host),
 403                         .timeout        = &timeparms,
 404                         .servername     = host->h_name,
 405                         .program        = &nlm_program,
 406                         .version        = host->h_version,
 407                         .authflavor     = RPC_AUTH_UNIX,
 408                         .flags          = (RPC_CLNT_CREATE_NOPING |
 409                                            RPC_CLNT_CREATE_AUTOBIND),
 410                 };
 411
 412                 /*
 413                  * lockd retries server side blocks automatically so we want
 414                  * those to be soft RPC calls. Client side calls need to be
 415                  * hard RPC tasks.
 416                  */
 417                 if (!host->h_server)
 418                         args.flags |= RPC_CLNT_CREATE_HARDRTRY;
 419
 420                 clnt = rpc_create(&args);
 421                 if (!IS_ERR(clnt))
 422                         host->h_rpcclnt = clnt;
 423                 else {
 424                         printk("lockd: couldn't create RPC handle for %s\n", host->h_name);
 425                         clnt = NULL;
 426                 }
 427         }
 428
 429         mutex_unlock(&host->h_mutex);
 430         return clnt;
 431 }
 432
 433 /*
 434  * Force a portmap lookup of the remote lockd port
 435  */
 436 void
 437 nlm_rebind_host(struct nlm_host *host)
 438 {
 439         dprintk("lockd: rebind host %s\n", host->h_name);
 440         if (host->h_rpcclnt && time_after_eq(jiffies, host->h_nextrebind)) {
 441                 rpc_force_rebind(host->h_rpcclnt);
 442                 host->h_nextrebind = jiffies + NLM_HOST_REBIND;
 443         }
 444 }
 445
 446 /*
 447  * Increment NLM host count
 448  */
 449 struct nlm_host * nlm_get_host(struct nlm_host *host)
 450 {
 451         if (host) {
 452                 dprintk("lockd: get host %s\n", host->h_name);
 453                 atomic_inc(&host->h_count);
 454                 host->h_expires = jiffies + NLM_HOST_EXPIRE;
 455         }
 456         return host;
 457 }
 458
 459 /*
 460  * Release NLM host after use
 461  */
 462 void nlm_release_host(struct nlm_host *host)
 463 {
 464         if (host != NULL) {
 465                 dprintk("lockd: release host %s\n", host->h_name);
 466                 BUG_ON(atomic_read(&host->h_count) < 0);
 467                 if (atomic_dec_and_test(&host->h_count)) {
 468                         BUG_ON(!list_empty(&host->h_lockowners));
 469                         BUG_ON(!list_empty(&host->h_granted));
 470                         BUG_ON(!list_empty(&host->h_reclaim));
 471                 }
 472         }
 473 }
 474
 475 /*
 476  * We were notified that the host indicated by address &sin
 477  * has rebooted.
 478  * Release all resources held by that peer.
 479  */
 480 void nlm_host_rebooted(const struct sockaddr_in *sin,
 481                                 const char *hostname,
 482                                 unsigned int hostname_len,
 483                                 u32 new_state)
 484 {
 485         struct hlist_head *chain;
 486         struct hlist_node *pos;
 487         struct nsm_handle *nsm;
 488         struct nlm_host *host;
 489
 490         nsm = nsm_find((struct sockaddr *)sin, sizeof(*sin),
 491                         hostname, hostname_len, 0);
 492         if (nsm == NULL) {
 493                 dprintk("lockd: never saw rebooted peer '%.*s' before\n",
 494                                 hostname_len, hostname);
 495                 return;
 496         }
 497
 498         dprintk("lockd: nlm_host_rebooted(%.*s, %s)\n",
 499                         hostname_len, hostname, nsm->sm_addrbuf);
 500
 501         /* When reclaiming locks on this peer, make sure that
 502          * we set up a new notification */
 503         nsm->sm_monitored = 0;
 504
 505         /* Mark all hosts tied to this NSM state as having rebooted.
 506          * We run the loop repeatedly, because we drop the host table
 507          * lock for this.
 508          * To avoid processing a host several times, we match the nsmstate.
 509          */
 510 again:  mutex_lock(&nlm_host_mutex);
 511         for (chain = nlm_hosts; chain < nlm_hosts + NLM_HOST_NRHASH; ++chain) {
 512                 hlist_for_each_entry(host, pos, chain, h_hash) {
 513                         if (host->h_nsmhandle == nsm
 514                          && host->h_nsmstate != new_state) {
 515                                 host->h_nsmstate = new_state;
 516                                 host->h_state++;
 517
 518                                 nlm_get_host(host);
 519                                 mutex_unlock(&nlm_host_mutex);
 520
 521                                 if (host->h_server) {
 522                                         /* We're server for this guy, just ditch
 523                                          * all the locks he held. */
 524                                         nlmsvc_free_host_resources(host);
 525                                 } else {
 526                                         /* He's the server, initiate lock recovery. */
 527                                         nlmclnt_recovery(host);
 528                                 }
 529
 530                                 nlm_release_host(host);
 531                                 goto again;
 532                         }
 533                 }
 534         }
 535
 536         mutex_unlock(&nlm_host_mutex);
 537 }
 538
 539 /*
 540  * Shut down the hosts module.
 541  * Note that this routine is called only at server shutdown time.
 542  */
 543 void
 544 nlm_shutdown_hosts(void)
 545 {
 546         struct hlist_head *chain;
 547         struct hlist_node *pos;
 548         struct nlm_host *host;
 549
 550         dprintk("lockd: shutting down host module\n");
 551         mutex_lock(&nlm_host_mutex);
 552
 553         /* First, make all hosts eligible for gc */
 554         dprintk("lockd: nuking all hosts...\n");
 555         for (chain = nlm_hosts; chain < nlm_hosts + NLM_HOST_NRHASH; ++chain) {
 556                 hlist_for_each_entry(host, pos, chain, h_hash) {
 557                         host->h_expires = jiffies - 1;
 558                         if (host->h_rpcclnt) {
 559                                 rpc_shutdown_client(host->h_rpcclnt);
 560                                 host->h_rpcclnt = NULL;
 561                         }
 562                 }
 563         }
 564
 565         /* Then, perform a garbage collection pass */
 566         nlm_gc_hosts();
 567         mutex_unlock(&nlm_host_mutex);
 568
 569         /* complain if any hosts are left */
 570         if (nrhosts) {
 571                 printk(KERN_WARNING "lockd: couldn't shutdown host module!\n");
 572                 dprintk("lockd: %d hosts left:\n", nrhosts);
 573                 for (chain = nlm_hosts; chain < nlm_hosts + NLM_HOST_NRHASH; ++chain) {
 574                         hlist_for_each_entry(host, pos, chain, h_hash) {
 575                                 dprintk("       %s (cnt %d use %d exp %ld)\n",
 576                                         host->h_name, atomic_read(&host->h_count),
 577                                         host->h_inuse, host->h_expires);
 578                         }
 579                 }
 580         }
 581 }
 582
 583 /*
 584  * Garbage collect any unused NLM hosts.
 585  * This GC combines reference counting for async operations with
 586  * mark & sweep for resources held by remote clients.
 587  */
 588 static void
 589 nlm_gc_hosts(void)
 590 {
 591         struct hlist_head *chain;
 592         struct hlist_node *pos, *next;
 593         struct nlm_host *host;
 594
 595         dprintk("lockd: host garbage collection\n");
 596         for (chain = nlm_hosts; chain < nlm_hosts + NLM_HOST_NRHASH; ++chain) {
 597                 hlist_for_each_entry(host, pos, chain, h_hash)
 598                         host->h_inuse = 0;
 599         }
 600
 601         /* Mark all hosts that hold locks, blocks or shares */
 602         nlmsvc_mark_resources();
 603
 604         for (chain = nlm_hosts; chain < nlm_hosts + NLM_HOST_NRHASH; ++chain) {
 605                 hlist_for_each_entry_safe(host, pos, next, chain, h_hash) {
 606                         if (atomic_read(&host->h_count) || host->h_inuse
 607                          || time_before(jiffies, host->h_expires)) {
 608                                 dprintk("nlm_gc_hosts skipping %s (cnt %d use %d exp %ld)\n",
 609                                         host->h_name, atomic_read(&host->h_count),
 610                                         host->h_inuse, host->h_expires);
 611                                 continue;
 612                         }
 613                         dprintk("lockd: delete host %s\n", host->h_name);
 614                         hlist_del_init(&host->h_hash);
 615
 616                         nlm_destroy_host(host);
 617                         nrhosts--;
 618                 }
 619         }
 620
 621         next_gc = jiffies + NLM_HOST_COLLECT;
 622 }
 623
 624
 625 /*
 626  * Manage NSM handles
 627  */
 628 static LIST_HEAD(nsm_handles);
 629 static DEFINE_SPINLOCK(nsm_lock);
 630
 631 static struct nsm_handle *nsm_find(const struct sockaddr *sap,
 632                                    const size_t salen,
 633                                    const char *hostname,
 634                                    const size_t hostname_len,
 635                                    const int create)
 636 {
 637         struct nsm_handle *nsm = NULL;
 638         struct nsm_handle *pos;
 639
 640         if (!sap)
 641                 return NULL;
 642
 643         if (hostname && memchr(hostname, '/', hostname_len) != NULL) {
 644                 if (printk_ratelimit()) {
 645                         printk(KERN_WARNING "Invalid hostname \"%.*s\" "
 646                                             "in NFS lock request\n",
 647                                 (int)hostname_len, hostname);
 648                 }
 649                 return NULL;
 650         }
 651
 652 retry:
 653         spin_lock(&nsm_lock);
 654         list_for_each_entry(pos, &nsm_handles, sm_link) {
 655
 656                 if (hostname && nsm_use_hostnames) {
 657                         if (strlen(pos->sm_name) != hostname_len
 658                          || memcmp(pos->sm_name, hostname, hostname_len))
 659                                 continue;
 660                 } else if (!nlm_cmp_addr(nsm_addr(pos), sap))
 661                         continue;
 662                 atomic_inc(&pos->sm_count);
 663                 kfree(nsm);
 664                 nsm = pos;
 665                 goto found;
 666         }
 667         if (nsm) {
 668                 list_add(&nsm->sm_link, &nsm_handles);
 669                 goto found;
 670         }
 671         spin_unlock(&nsm_lock);
 672
 673         if (!create)
 674                 return NULL;
 675
 676         nsm = kzalloc(sizeof(*nsm) + hostname_len + 1, GFP_KERNEL);
 677         if (nsm == NULL)
 678                 return NULL;
 679
 680         memcpy(nsm_addr(nsm), sap, salen);
 681         nsm->sm_addrlen = salen;
 682         nsm->sm_name = (char *) (nsm + 1);
 683         memcpy(nsm->sm_name, hostname, hostname_len);
 684         nsm->sm_name[hostname_len] = '\0';
 685         nlm_display_address((struct sockaddr *)&nsm->sm_addr,
 686                                 nsm->sm_addrbuf, sizeof(nsm->sm_addrbuf));
 687         atomic_set(&nsm->sm_count, 1);
 688         goto retry;
 689
 690 found:
 691         spin_unlock(&nsm_lock);
 692         return nsm;
 693 }
 694
 695 /*
 696  * Release an NSM handle
 697  */
 698 void
 699 nsm_release(struct nsm_handle *nsm)
 700 {
 701         if (!nsm)
 702                 return;
 703         if (atomic_dec_and_lock(&nsm->sm_count, &nsm_lock)) {
 704                 list_del(&nsm->sm_link);
 705                 spin_unlock(&nsm_lock);
 706                 kfree(nsm);
 707         }
 708 }