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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         const int               noresvport;     /* use non-priv port */
  52 };
  53
  54 /*
  55  * Hash function must work well on big- and little-endian platforms
  56  */
  57 static unsigned int __nlm_hash32(const __be32 n)
  58 {
  59         unsigned int hash = (__force u32)n ^ ((__force u32)n >> 16);
  60         return hash ^ (hash >> 8);
  61 }
  62
  63 static unsigned int __nlm_hash_addr4(const struct sockaddr *sap)
  64 {
  65         const struct sockaddr_in *sin = (struct sockaddr_in *)sap;
  66         return __nlm_hash32(sin->sin_addr.s_addr);
  67 }
  68
  69 static unsigned int __nlm_hash_addr6(const struct sockaddr *sap)
  70 {
  71         const struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)sap;
  72         const struct in6_addr addr = sin6->sin6_addr;
  73         return __nlm_hash32(addr.s6_addr32[0]) ^
  74                __nlm_hash32(addr.s6_addr32[1]) ^
  75                __nlm_hash32(addr.s6_addr32[2]) ^
  76                __nlm_hash32(addr.s6_addr32[3]);
  77 }
  78
  79 static unsigned int nlm_hash_address(const struct sockaddr *sap)
  80 {
  81         unsigned int hash;
  82
  83         switch (sap->sa_family) {
  84         case AF_INET:
  85                 hash = __nlm_hash_addr4(sap);
  86                 break;
  87         case AF_INET6:
  88                 hash = __nlm_hash_addr6(sap);
  89                 break;
  90         default:
  91                 hash = 0;
  92         }
  93         return hash & (NLM_HOST_NRHASH - 1);
  94 }
  95
  96 static void nlm_clear_port(struct sockaddr *sap)
  97 {
  98         switch (sap->sa_family) {
  99         case AF_INET:
 100                 ((struct sockaddr_in *)sap)->sin_port = 0;
 101                 break;
 102         case AF_INET6:
 103                 ((struct sockaddr_in6 *)sap)->sin6_port = 0;
 104                 break;
 105         }
 106 }
 107
 108 static void nlm_display_address(const struct sockaddr *sap,
 109                                 char *buf, const size_t len)
 110 {
 111         const struct sockaddr_in *sin = (struct sockaddr_in *)sap;
 112         const struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *)sap;
 113
 114         switch (sap->sa_family) {
 115         case AF_INET:
 116                 snprintf(buf, len, "%pI4", &sin->sin_addr.s_addr);
 117                 break;
 118         case AF_INET6:
 119                 if (ipv6_addr_v4mapped(&sin6->sin6_addr))
 120                         snprintf(buf, len, "%pI4",
 121                                  &sin6->sin6_addr.s6_addr32[3]);
 122                 else
 123                         snprintf(buf, len, "%pI6", &sin6->sin6_addr);
 124                 break;
 125         default:
 126                 snprintf(buf, len, "unsupported address family");
 127                 break;
 128         }
 129 }
 130
 131 /*
 132  * Common host lookup routine for server & client
 133  */
 134 static struct nlm_host *nlm_lookup_host(struct nlm_lookup_host_info *ni)
 135 {
 136         struct hlist_head *chain;
 137         struct hlist_node *pos;
 138         struct nlm_host *host;
 139         struct nsm_handle *nsm = NULL;
 140
 141         mutex_lock(&nlm_host_mutex);
 142
 143         if (time_after_eq(jiffies, next_gc))
 144                 nlm_gc_hosts();
 145
 146         /* We may keep several nlm_host objects for a peer, because each
 147          * nlm_host is identified by
 148          * (address, protocol, version, server/client)
 149          * We could probably simplify this a little by putting all those
 150          * different NLM rpc_clients into one single nlm_host object.
 151          * This would allow us to have one nlm_host per address.
 152          */
 153         chain = &nlm_hosts[nlm_hash_address(ni->sap)];
 154         hlist_for_each_entry(host, pos, chain, h_hash) {
 155                 if (!nlm_cmp_addr(nlm_addr(host), ni->sap))
 156                         continue;
 157
 158                 /* See if we have an NSM handle for this client */
 159                 if (!nsm)
 160                         nsm = host->h_nsmhandle;
 161
 162                 if (host->h_proto != ni->protocol)
 163                         continue;
 164                 if (host->h_version != ni->version)
 165                         continue;
 166                 if (host->h_server != ni->server)
 167                         continue;
 168                 if (ni->server &&
 169                     !nlm_cmp_addr(nlm_srcaddr(host), ni->src_sap))
 170                         continue;
 171
 172                 /* Move to head of hash chain. */
 173                 hlist_del(&host->h_hash);
 174                 hlist_add_head(&host->h_hash, chain);
 175
 176                 nlm_get_host(host);
 177                 dprintk("lockd: nlm_lookup_host found host %s (%s)\n",
 178                                 host->h_name, host->h_addrbuf);
 179                 goto out;
 180         }
 181
 182         /*
 183          * The host wasn't in our hash table.  If we don't
 184          * have an NSM handle for it yet, create one.
 185          */
 186         if (nsm)
 187                 atomic_inc(&nsm->sm_count);
 188         else {
 189                 host = NULL;
 190                 nsm = nsm_find(ni->sap, ni->salen,
 191                                 ni->hostname, ni->hostname_len, 1);
 192                 if (!nsm) {
 193                         dprintk("lockd: nlm_lookup_host failed; "
 194                                 "no nsm handle\n");
 195                         goto out;
 196                 }
 197         }
 198
 199         host = kzalloc(sizeof(*host), GFP_KERNEL);
 200         if (!host) {
 201                 nsm_release(nsm);
 202                 dprintk("lockd: nlm_lookup_host failed; no memory\n");
 203                 goto out;
 204         }
 205         host->h_name       = nsm->sm_name;
 206         host->h_addrbuf    = nsm->sm_addrbuf;
 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         host->h_noresvport = ni->noresvport;
 225         hlist_add_head(&host->h_hash, chain);
 226         INIT_LIST_HEAD(&host->h_lockowners);
 227         spin_lock_init(&host->h_lock);
 228         INIT_LIST_HEAD(&host->h_granted);
 229         INIT_LIST_HEAD(&host->h_reclaim);
 230
 231         nrhosts++;
 232
 233         dprintk("lockd: nlm_lookup_host created host %s\n",
 234                         host->h_name);
 235
 236 out:
 237         mutex_unlock(&nlm_host_mutex);
 238         return host;
 239 }
 240
 241 /*
 242  * Destroy a host
 243  */
 244 static void
 245 nlm_destroy_host(struct nlm_host *host)
 246 {
 247         struct rpc_clnt *clnt;
 248
 249         BUG_ON(!list_empty(&host->h_lockowners));
 250         BUG_ON(atomic_read(&host->h_count));
 251
 252         /*
 253          * Release NSM handle and unmonitor host.
 254          */
 255         nsm_unmonitor(host);
 256
 257         clnt = host->h_rpcclnt;
 258         if (clnt != NULL)
 259                 rpc_shutdown_client(clnt);
 260         kfree(host);
 261 }
 262
 263 /**
 264  * nlmclnt_lookup_host - Find an NLM host handle matching a remote server
 265  * @sap: network address of server
 266  * @salen: length of server address
 267  * @protocol: transport protocol to use
 268  * @version: NLM protocol version
 269  * @hostname: '\0'-terminated hostname of server
 270  * @noresvport: 1 if non-privileged port should be used
 271  *
 272  * Returns an nlm_host structure that matches the passed-in
 273  * [server address, transport protocol, NLM version, server hostname].
 274  * If one doesn't already exist in the host cache, a new handle is
 275  * created and returned.
 276  */
 277 struct nlm_host *nlmclnt_lookup_host(const struct sockaddr *sap,
 278                                      const size_t salen,
 279                                      const unsigned short protocol,
 280                                      const u32 version,
 281                                      const char *hostname,
 282                                      int noresvport)
 283 {
 284         const struct sockaddr source = {
 285                 .sa_family      = AF_UNSPEC,
 286         };
 287         struct nlm_lookup_host_info ni = {
 288                 .server         = 0,
 289                 .sap            = sap,
 290                 .salen          = salen,
 291                 .protocol       = protocol,
 292                 .version        = version,
 293                 .hostname       = hostname,
 294                 .hostname_len   = strlen(hostname),
 295                 .src_sap        = &source,
 296                 .src_len        = sizeof(source),
 297                 .noresvport     = noresvport,
 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)\n",
 375                         host->h_name, host->h_addrbuf);
 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                 if (host->h_noresvport)
 420                         args.flags |= RPC_CLNT_CREATE_NONPRIVPORT;
 421
 422                 clnt = rpc_create(&args);
 423                 if (!IS_ERR(clnt))
 424                         host->h_rpcclnt = clnt;
 425                 else {
 426                         printk("lockd: couldn't create RPC handle for %s\n", host->h_name);
 427                         clnt = NULL;
 428                 }
 429         }
 430
 431         mutex_unlock(&host->h_mutex);
 432         return clnt;
 433 }
 434
 435 /*
 436  * Force a portmap lookup of the remote lockd port
 437  */
 438 void
 439 nlm_rebind_host(struct nlm_host *host)
 440 {
 441         dprintk("lockd: rebind host %s\n", host->h_name);
 442         if (host->h_rpcclnt && time_after_eq(jiffies, host->h_nextrebind)) {
 443                 rpc_force_rebind(host->h_rpcclnt);
 444                 host->h_nextrebind = jiffies + NLM_HOST_REBIND;
 445         }
 446 }
 447
 448 /*
 449  * Increment NLM host count
 450  */
 451 struct nlm_host * nlm_get_host(struct nlm_host *host)
 452 {
 453         if (host) {
 454                 dprintk("lockd: get host %s\n", host->h_name);
 455                 atomic_inc(&host->h_count);
 456                 host->h_expires = jiffies + NLM_HOST_EXPIRE;
 457         }
 458         return host;
 459 }
 460
 461 /*
 462  * Release NLM host after use
 463  */
 464 void nlm_release_host(struct nlm_host *host)
 465 {
 466         if (host != NULL) {
 467                 dprintk("lockd: release host %s\n", host->h_name);
 468                 BUG_ON(atomic_read(&host->h_count) < 0);
 469                 if (atomic_dec_and_test(&host->h_count)) {
 470                         BUG_ON(!list_empty(&host->h_lockowners));
 471                         BUG_ON(!list_empty(&host->h_granted));
 472                         BUG_ON(!list_empty(&host->h_reclaim));
 473                 }
 474         }
 475 }
 476
 477 /*
 478  * We were notified that the host indicated by address &sin
 479  * has rebooted.
 480  * Release all resources held by that peer.
 481  */
 482 void nlm_host_rebooted(const struct sockaddr_in *sin,
 483                                 const char *hostname,
 484                                 unsigned int hostname_len,
 485                                 u32 new_state)
 486 {
 487         struct hlist_head *chain;
 488         struct hlist_node *pos;
 489         struct nsm_handle *nsm;
 490         struct nlm_host *host;
 491
 492         nsm = nsm_find((struct sockaddr *)sin, sizeof(*sin),
 493                         hostname, hostname_len, 0);
 494         if (nsm == NULL) {
 495                 dprintk("lockd: never saw rebooted peer '%.*s' before\n",
 496                                 hostname_len, hostname);
 497                 return;
 498         }
 499
 500         dprintk("lockd: nlm_host_rebooted(%.*s, %s)\n",
 501                         hostname_len, hostname, nsm->sm_addrbuf);
 502
 503         /* When reclaiming locks on this peer, make sure that
 504          * we set up a new notification */
 505         nsm->sm_monitored = 0;
 506
 507         /* Mark all hosts tied to this NSM state as having rebooted.
 508          * We run the loop repeatedly, because we drop the host table
 509          * lock for this.
 510          * To avoid processing a host several times, we match the nsmstate.
 511          */
 512 again:  mutex_lock(&nlm_host_mutex);
 513         for (chain = nlm_hosts; chain < nlm_hosts + NLM_HOST_NRHASH; ++chain) {
 514                 hlist_for_each_entry(host, pos, chain, h_hash) {
 515                         if (host->h_nsmhandle == nsm
 516                          && host->h_nsmstate != new_state) {
 517                                 host->h_nsmstate = new_state;
 518                                 host->h_state++;
 519
 520                                 nlm_get_host(host);
 521                                 mutex_unlock(&nlm_host_mutex);
 522
 523                                 if (host->h_server) {
 524                                         /* We're server for this guy, just ditch
 525                                          * all the locks he held. */
 526                                         nlmsvc_free_host_resources(host);
 527                                 } else {
 528                                         /* He's the server, initiate lock recovery. */
 529                                         nlmclnt_recovery(host);
 530                                 }
 531
 532                                 nlm_release_host(host);
 533                                 goto again;
 534                         }
 535                 }
 536         }
 537
 538         mutex_unlock(&nlm_host_mutex);
 539 }
 540
 541 /*
 542  * Shut down the hosts module.
 543  * Note that this routine is called only at server shutdown time.
 544  */
 545 void
 546 nlm_shutdown_hosts(void)
 547 {
 548         struct hlist_head *chain;
 549         struct hlist_node *pos;
 550         struct nlm_host *host;
 551
 552         dprintk("lockd: shutting down host module\n");
 553         mutex_lock(&nlm_host_mutex);
 554
 555         /* First, make all hosts eligible for gc */
 556         dprintk("lockd: nuking all hosts...\n");
 557         for (chain = nlm_hosts; chain < nlm_hosts + NLM_HOST_NRHASH; ++chain) {
 558                 hlist_for_each_entry(host, pos, chain, h_hash) {
 559                         host->h_expires = jiffies - 1;
 560                         if (host->h_rpcclnt) {
 561                                 rpc_shutdown_client(host->h_rpcclnt);
 562                                 host->h_rpcclnt = NULL;
 563                         }
 564                 }
 565         }
 566
 567         /* Then, perform a garbage collection pass */
 568         nlm_gc_hosts();
 569         mutex_unlock(&nlm_host_mutex);
 570
 571         /* complain if any hosts are left */
 572         if (nrhosts) {
 573                 printk(KERN_WARNING "lockd: couldn't shutdown host module!\n");
 574                 dprintk("lockd: %d hosts left:\n", nrhosts);
 575                 for (chain = nlm_hosts; chain < nlm_hosts + NLM_HOST_NRHASH; ++chain) {
 576                         hlist_for_each_entry(host, pos, chain, h_hash) {
 577                                 dprintk("       %s (cnt %d use %d exp %ld)\n",
 578                                         host->h_name, atomic_read(&host->h_count),
 579                                         host->h_inuse, host->h_expires);
 580                         }
 581                 }
 582         }
 583 }
 584
 585 /*
 586  * Garbage collect any unused NLM hosts.
 587  * This GC combines reference counting for async operations with
 588  * mark & sweep for resources held by remote clients.
 589  */
 590 static void
 591 nlm_gc_hosts(void)
 592 {
 593         struct hlist_head *chain;
 594         struct hlist_node *pos, *next;
 595         struct nlm_host *host;
 596
 597         dprintk("lockd: host garbage collection\n");
 598         for (chain = nlm_hosts; chain < nlm_hosts + NLM_HOST_NRHASH; ++chain) {
 599                 hlist_for_each_entry(host, pos, chain, h_hash)
 600                         host->h_inuse = 0;
 601         }
 602
 603         /* Mark all hosts that hold locks, blocks or shares */
 604         nlmsvc_mark_resources();
 605
 606         for (chain = nlm_hosts; chain < nlm_hosts + NLM_HOST_NRHASH; ++chain) {
 607                 hlist_for_each_entry_safe(host, pos, next, chain, h_hash) {
 608                         if (atomic_read(&host->h_count) || host->h_inuse
 609                          || time_before(jiffies, host->h_expires)) {
 610                                 dprintk("nlm_gc_hosts skipping %s (cnt %d use %d exp %ld)\n",
 611                                         host->h_name, atomic_read(&host->h_count),
 612                                         host->h_inuse, host->h_expires);
 613                                 continue;
 614                         }
 615                         dprintk("lockd: delete host %s\n", host->h_name);
 616                         hlist_del_init(&host->h_hash);
 617
 618                         nlm_destroy_host(host);
 619                         nrhosts--;
 620                 }
 621         }
 622
 623         next_gc = jiffies + NLM_HOST_COLLECT;
 624 }
 625
 626
 627 /*
 628  * Manage NSM handles
 629  */
 630 static LIST_HEAD(nsm_handles);
 631 static DEFINE_SPINLOCK(nsm_lock);
 632
 633 static struct nsm_handle *nsm_find(const struct sockaddr *sap,
 634                                    const size_t salen,
 635                                    const char *hostname,
 636                                    const size_t hostname_len,
 637                                    const int create)
 638 {
 639         struct nsm_handle *nsm = NULL;
 640         struct nsm_handle *pos;
 641
 642         if (!sap)
 643                 return NULL;
 644
 645         if (hostname && memchr(hostname, '/', hostname_len) != NULL) {
 646                 if (printk_ratelimit()) {
 647                         printk(KERN_WARNING "Invalid hostname \"%.*s\" "
 648                                             "in NFS lock request\n",
 649                                 (int)hostname_len, hostname);
 650                 }
 651                 return NULL;
 652         }
 653
 654 retry:
 655         spin_lock(&nsm_lock);
 656         list_for_each_entry(pos, &nsm_handles, sm_link) {
 657
 658                 if (hostname && nsm_use_hostnames) {
 659                         if (strlen(pos->sm_name) != hostname_len
 660                          || memcmp(pos->sm_name, hostname, hostname_len))
 661                                 continue;
 662                 } else if (!nlm_cmp_addr(nsm_addr(pos), sap))
 663                         continue;
 664                 atomic_inc(&pos->sm_count);
 665                 kfree(nsm);
 666                 nsm = pos;
 667                 goto found;
 668         }
 669         if (nsm) {
 670                 list_add(&nsm->sm_link, &nsm_handles);
 671                 goto found;
 672         }
 673         spin_unlock(&nsm_lock);
 674
 675         if (!create)
 676                 return NULL;
 677
 678         nsm = kzalloc(sizeof(*nsm) + hostname_len + 1, GFP_KERNEL);
 679         if (nsm == NULL)
 680                 return NULL;
 681
 682         memcpy(nsm_addr(nsm), sap, salen);
 683         nsm->sm_addrlen = salen;
 684         nsm->sm_name = (char *) (nsm + 1);
 685         memcpy(nsm->sm_name, hostname, hostname_len);
 686         nsm->sm_name[hostname_len] = '\0';
 687         nlm_display_address((struct sockaddr *)&nsm->sm_addr,
 688                                 nsm->sm_addrbuf, sizeof(nsm->sm_addrbuf));
 689         atomic_set(&nsm->sm_count, 1);
 690         goto retry;
 691
 692 found:
 693         spin_unlock(&nsm_lock);
 694         return nsm;
 695 }
 696
 697 /*
 698  * Release an NSM handle
 699  */
 700 void
 701 nsm_release(struct nsm_handle *nsm)
 702 {
 703         if (!nsm)
 704                 return;
 705         if (atomic_dec_and_lock(&nsm->sm_count, &nsm_lock)) {
 706                 list_del(&nsm->sm_link);
 707                 spin_unlock(&nsm_lock);
 708                 kfree(nsm);
 709         }
 710 }