git.oblomov.eu Git - linux-2.6/blob - 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/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 (ni->server &&
 171                     !nlm_cmp_addr(nlm_srcaddr(host), ni->src_sap))
 172                         continue;
 173
 174                 /* Move to head of hash chain. */
 175                 hlist_del(&host->h_hash);
 176                 hlist_add_head(&host->h_hash, chain);
 177
 178                 nlm_get_host(host);
 179                 dprintk("lockd: nlm_lookup_host found host %s (%s)\n",
 180                                 host->h_name, host->h_addrbuf);
 181                 goto out;
 182         }
 183
 184         /*
 185          * The host wasn't in our hash table.  If we don't
 186          * have an NSM handle for it yet, create one.
 187          */
 188         if (nsm)
 189                 atomic_inc(&nsm->sm_count);
 190         else {
 191                 host = NULL;
 192                 nsm = nsm_find(ni->sap, ni->salen,
 193                                 ni->hostname, ni->hostname_len, 1);
 194                 if (!nsm) {
 195                         dprintk("lockd: nlm_lookup_host failed; "
 196                                 "no nsm handle\n");
 197                         goto out;
 198                 }
 199         }
 200
 201         host = kzalloc(sizeof(*host), GFP_KERNEL);
 202         if (!host) {
 203                 nsm_release(nsm);
 204                 dprintk("lockd: nlm_lookup_host failed; no memory\n");
 205                 goto out;
 206         }
 207         host->h_name       = nsm->sm_name;
 208         memcpy(nlm_addr(host), ni->sap, ni->salen);
 209         host->h_addrlen = ni->salen;
 210         nlm_clear_port(nlm_addr(host));
 211         memcpy(nlm_srcaddr(host), ni->src_sap, ni->src_len);
 212         host->h_version    = ni->version;
 213         host->h_proto      = ni->protocol;
 214         host->h_rpcclnt    = NULL;
 215         mutex_init(&host->h_mutex);
 216         host->h_nextrebind = jiffies + NLM_HOST_REBIND;
 217         host->h_expires    = jiffies + NLM_HOST_EXPIRE;
 218         atomic_set(&host->h_count, 1);
 219         init_waitqueue_head(&host->h_gracewait);
 220         init_rwsem(&host->h_rwsem);
 221         host->h_state      = 0;                 /* pseudo NSM state */
 222         host->h_nsmstate   = 0;                 /* real NSM state */
 223         host->h_nsmhandle  = nsm;
 224         host->h_server     = ni->server;
 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         nlm_display_address((struct sockaddr *)&host->h_addr,
 234                                 host->h_addrbuf, sizeof(host->h_addrbuf));
 235         nlm_display_address((struct sockaddr *)&host->h_srcaddr,
 236                                 host->h_srcaddrbuf, sizeof(host->h_srcaddrbuf));
 237
 238         dprintk("lockd: nlm_lookup_host created host %s\n",
 239                         host->h_name);
 240
 241 out:
 242         mutex_unlock(&nlm_host_mutex);
 243         return host;
 244 }
 245
 246 /*
 247  * Destroy a host
 248  */
 249 static void
 250 nlm_destroy_host(struct nlm_host *host)
 251 {
 252         struct rpc_clnt *clnt;
 253
 254         BUG_ON(!list_empty(&host->h_lockowners));
 255         BUG_ON(atomic_read(&host->h_count));
 256
 257         /*
 258          * Release NSM handle and unmonitor host.
 259          */
 260         nsm_unmonitor(host);
 261
 262         clnt = host->h_rpcclnt;
 263         if (clnt != NULL)
 264                 rpc_shutdown_client(clnt);
 265         kfree(host);
 266 }
 267
 268 /**
 269  * nlmclnt_lookup_host - Find an NLM host handle matching a remote server
 270  * @sap: network address of server
 271  * @salen: length of server address
 272  * @protocol: transport protocol to use
 273  * @version: NLM protocol version
 274  * @hostname: '\0'-terminated hostname of server
 275  *
 276  * Returns an nlm_host structure that matches the passed-in
 277  * [server address, transport protocol, NLM version, server hostname].
 278  * If one doesn't already exist in the host cache, a new handle is
 279  * created and returned.
 280  */
 281 struct nlm_host *nlmclnt_lookup_host(const struct sockaddr *sap,
 282                                      const size_t salen,
 283                                      const unsigned short protocol,
 284                                      const u32 version, const char *hostname)
 285 {
 286         const struct sockaddr source = {
 287                 .sa_family      = AF_UNSPEC,
 288         };
 289         struct nlm_lookup_host_info ni = {
 290                 .server         = 0,
 291                 .sap            = sap,
 292                 .salen          = salen,
 293                 .protocol       = protocol,
 294                 .version        = version,
 295                 .hostname       = hostname,
 296                 .hostname_len   = strlen(hostname),
 297                 .src_sap        = &source,
 298                 .src_len        = sizeof(source),
 299         };
 300
 301         dprintk("lockd: %s(host='%s', vers=%u, proto=%s)\n", __func__,
 302                         (hostname ? hostname : "<none>"), version,
 303                         (protocol == IPPROTO_UDP ? "udp" : "tcp"));
 304
 305         return nlm_lookup_host(&ni);
 306 }
 307
 308 /**
 309  * nlmsvc_lookup_host - Find an NLM host handle matching a remote client
 310  * @rqstp: incoming NLM request
 311  * @hostname: name of client host
 312  * @hostname_len: length of client hostname
 313  *
 314  * Returns an nlm_host structure that matches the [client address,
 315  * transport protocol, NLM version, client hostname] of the passed-in
 316  * NLM request.  If one doesn't already exist in the host cache, a
 317  * new handle is created and returned.
 318  *
 319  * Before possibly creating a new nlm_host, construct a sockaddr
 320  * for a specific source address in case the local system has
 321  * multiple network addresses.  The family of the address in
 322  * rq_daddr is guaranteed to be the same as the family of the
 323  * address in rq_addr, so it's safe to use the same family for
 324  * the source address.
 325  */
 326 struct nlm_host *nlmsvc_lookup_host(const struct svc_rqst *rqstp,
 327                                     const char *hostname,
 328                                     const size_t hostname_len)
 329 {
 330         struct sockaddr_in sin = {
 331                 .sin_family     = AF_INET,
 332         };
 333         struct sockaddr_in6 sin6 = {
 334                 .sin6_family    = AF_INET6,
 335         };
 336         struct nlm_lookup_host_info ni = {
 337                 .server         = 1,
 338                 .sap            = svc_addr(rqstp),
 339                 .salen          = rqstp->rq_addrlen,
 340                 .protocol       = rqstp->rq_prot,
 341                 .version        = rqstp->rq_vers,
 342                 .hostname       = hostname,
 343                 .hostname_len   = hostname_len,
 344                 .src_len        = rqstp->rq_addrlen,
 345         };
 346
 347         dprintk("lockd: %s(host='%*s', vers=%u, proto=%s)\n", __func__,
 348                         (int)hostname_len, hostname, rqstp->rq_vers,
 349                         (rqstp->rq_prot == IPPROTO_UDP ? "udp" : "tcp"));
 350
 351         switch (ni.sap->sa_family) {
 352         case AF_INET:
 353                 sin.sin_addr.s_addr = rqstp->rq_daddr.addr.s_addr;
 354                 ni.src_sap = (struct sockaddr *)&sin;
 355                 break;
 356         case AF_INET6:
 357                 ipv6_addr_copy(&sin6.sin6_addr, &rqstp->rq_daddr.addr6);
 358                 ni.src_sap = (struct sockaddr *)&sin6;
 359                 break;
 360         default:
 361                 return NULL;
 362         }
 363
 364         return nlm_lookup_host(&ni);
 365 }
 366
 367 /*
 368  * Create the NLM RPC client for an NLM peer
 369  */
 370 struct rpc_clnt *
 371 nlm_bind_host(struct nlm_host *host)
 372 {
 373         struct rpc_clnt *clnt;
 374
 375         dprintk("lockd: nlm_bind_host %s (%s), my addr=%s\n",
 376                         host->h_name, host->h_addrbuf, host->h_srcaddrbuf);
 377
 378         /* Lock host handle */
 379         mutex_lock(&host->h_mutex);
 380
 381         /* If we've already created an RPC client, check whether
 382          * RPC rebind is required
 383          */
 384         if ((clnt = host->h_rpcclnt) != NULL) {
 385                 if (time_after_eq(jiffies, host->h_nextrebind)) {
 386                         rpc_force_rebind(clnt);
 387                         host->h_nextrebind = jiffies + NLM_HOST_REBIND;
 388                         dprintk("lockd: next rebind in %lu jiffies\n",
 389                                         host->h_nextrebind - jiffies);
 390                 }
 391         } else {
 392                 unsigned long increment = nlmsvc_timeout;
 393                 struct rpc_timeout timeparms = {
 394                         .to_initval     = increment,
 395                         .to_increment   = increment,
 396                         .to_maxval      = increment * 6UL,
 397                         .to_retries     = 5U,
 398                 };
 399                 struct rpc_create_args args = {
 400                         .protocol       = host->h_proto,
 401                         .address        = nlm_addr(host),
 402                         .addrsize       = host->h_addrlen,
 403                         .saddress       = nlm_srcaddr(host),
 404                         .timeout        = &timeparms,
 405                         .servername     = host->h_name,
 406                         .program        = &nlm_program,
 407                         .version        = host->h_version,
 408                         .authflavor     = RPC_AUTH_UNIX,
 409                         .flags          = (RPC_CLNT_CREATE_NOPING |
 410                                            RPC_CLNT_CREATE_AUTOBIND),
 411                 };
 412
 413                 /*
 414                  * lockd retries server side blocks automatically so we want
 415                  * those to be soft RPC calls. Client side calls need to be
 416                  * hard RPC tasks.
 417                  */
 418                 if (!host->h_server)
 419                         args.flags |= RPC_CLNT_CREATE_HARDRTRY;
 420
 421                 clnt = rpc_create(&args);
 422                 if (!IS_ERR(clnt))
 423                         host->h_rpcclnt = clnt;
 424                 else {
 425                         printk("lockd: couldn't create RPC handle for %s\n", host->h_name);
 426                         clnt = NULL;
 427                 }
 428         }
 429
 430         mutex_unlock(&host->h_mutex);
 431         return clnt;
 432 }
 433
 434 /*
 435  * Force a portmap lookup of the remote lockd port
 436  */
 437 void
 438 nlm_rebind_host(struct nlm_host *host)
 439 {
 440         dprintk("lockd: rebind host %s\n", host->h_name);
 441         if (host->h_rpcclnt && time_after_eq(jiffies, host->h_nextrebind)) {
 442                 rpc_force_rebind(host->h_rpcclnt);
 443                 host->h_nextrebind = jiffies + NLM_HOST_REBIND;
 444         }
 445 }
 446
 447 /*
 448  * Increment NLM host count
 449  */
 450 struct nlm_host * nlm_get_host(struct nlm_host *host)
 451 {
 452         if (host) {
 453                 dprintk("lockd: get host %s\n", host->h_name);
 454                 atomic_inc(&host->h_count);
 455                 host->h_expires = jiffies + NLM_HOST_EXPIRE;
 456         }
 457         return host;
 458 }
 459
 460 /*
 461  * Release NLM host after use
 462  */
 463 void nlm_release_host(struct nlm_host *host)
 464 {
 465         if (host != NULL) {
 466                 dprintk("lockd: release host %s\n", host->h_name);
 467                 BUG_ON(atomic_read(&host->h_count) < 0);
 468                 if (atomic_dec_and_test(&host->h_count)) {
 469                         BUG_ON(!list_empty(&host->h_lockowners));
 470                         BUG_ON(!list_empty(&host->h_granted));
 471                         BUG_ON(!list_empty(&host->h_reclaim));
 472                 }
 473         }
 474 }
 475
 476 /*
 477  * We were notified that the host indicated by address &sin
 478  * has rebooted.
 479  * Release all resources held by that peer.
 480  */
 481 void nlm_host_rebooted(const struct sockaddr_in *sin,
 482                                 const char *hostname,
 483                                 unsigned int hostname_len,
 484                                 u32 new_state)
 485 {
 486         struct hlist_head *chain;
 487         struct hlist_node *pos;
 488         struct nsm_handle *nsm;
 489         struct nlm_host *host;
 490
 491         nsm = nsm_find((struct sockaddr *)sin, sizeof(*sin),
 492                         hostname, hostname_len, 0);
 493         if (nsm == NULL) {
 494                 dprintk("lockd: never saw rebooted peer '%.*s' before\n",
 495                                 hostname_len, hostname);
 496                 return;
 497         }
 498
 499         dprintk("lockd: nlm_host_rebooted(%.*s, %s)\n",
 500                         hostname_len, hostname, nsm->sm_addrbuf);
 501
 502         /* When reclaiming locks on this peer, make sure that
 503          * we set up a new notification */
 504         nsm->sm_monitored = 0;
 505
 506         /* Mark all hosts tied to this NSM state as having rebooted.
 507          * We run the loop repeatedly, because we drop the host table
 508          * lock for this.
 509          * To avoid processing a host several times, we match the nsmstate.
 510          */
 511 again:  mutex_lock(&nlm_host_mutex);
 512         for (chain = nlm_hosts; chain < nlm_hosts + NLM_HOST_NRHASH; ++chain) {
 513                 hlist_for_each_entry(host, pos, chain, h_hash) {
 514                         if (host->h_nsmhandle == nsm
 515                          && host->h_nsmstate != new_state) {
 516                                 host->h_nsmstate = new_state;
 517                                 host->h_state++;
 518
 519                                 nlm_get_host(host);
 520                                 mutex_unlock(&nlm_host_mutex);
 521
 522                                 if (host->h_server) {
 523                                         /* We're server for this guy, just ditch
 524                                          * all the locks he held. */
 525                                         nlmsvc_free_host_resources(host);
 526                                 } else {
 527                                         /* He's the server, initiate lock recovery. */
 528                                         nlmclnt_recovery(host);
 529                                 }
 530
 531                                 nlm_release_host(host);
 532                                 goto again;
 533                         }
 534                 }
 535         }
 536
 537         mutex_unlock(&nlm_host_mutex);
 538 }
 539
 540 /*
 541  * Shut down the hosts module.
 542  * Note that this routine is called only at server shutdown time.
 543  */
 544 void
 545 nlm_shutdown_hosts(void)
 546 {
 547         struct hlist_head *chain;
 548         struct hlist_node *pos;
 549         struct nlm_host *host;
 550
 551         dprintk("lockd: shutting down host module\n");
 552         mutex_lock(&nlm_host_mutex);
 553
 554         /* First, make all hosts eligible for gc */
 555         dprintk("lockd: nuking all hosts...\n");
 556         for (chain = nlm_hosts; chain < nlm_hosts + NLM_HOST_NRHASH; ++chain) {
 557                 hlist_for_each_entry(host, pos, chain, h_hash) {
 558                         host->h_expires = jiffies - 1;
 559                         if (host->h_rpcclnt) {
 560                                 rpc_shutdown_client(host->h_rpcclnt);
 561                                 host->h_rpcclnt = NULL;
 562                         }
 563                 }
 564         }
 565
 566         /* Then, perform a garbage collection pass */
 567         nlm_gc_hosts();
 568         mutex_unlock(&nlm_host_mutex);
 569
 570         /* complain if any hosts are left */
 571         if (nrhosts) {
 572                 printk(KERN_WARNING "lockd: couldn't shutdown host module!\n");
 573                 dprintk("lockd: %d hosts left:\n", nrhosts);
 574                 for (chain = nlm_hosts; chain < nlm_hosts + NLM_HOST_NRHASH; ++chain) {
 575                         hlist_for_each_entry(host, pos, chain, h_hash) {
 576                                 dprintk("       %s (cnt %d use %d exp %ld)\n",
 577                                         host->h_name, atomic_read(&host->h_count),
 578                                         host->h_inuse, host->h_expires);
 579                         }
 580                 }
 581         }
 582 }
 583
 584 /*
 585  * Garbage collect any unused NLM hosts.
 586  * This GC combines reference counting for async operations with
 587  * mark & sweep for resources held by remote clients.
 588  */
 589 static void
 590 nlm_gc_hosts(void)
 591 {
 592         struct hlist_head *chain;
 593         struct hlist_node *pos, *next;
 594         struct nlm_host *host;
 595
 596         dprintk("lockd: host garbage collection\n");
 597         for (chain = nlm_hosts; chain < nlm_hosts + NLM_HOST_NRHASH; ++chain) {
 598                 hlist_for_each_entry(host, pos, chain, h_hash)
 599                         host->h_inuse = 0;
 600         }
 601
 602         /* Mark all hosts that hold locks, blocks or shares */
 603         nlmsvc_mark_resources();
 604
 605         for (chain = nlm_hosts; chain < nlm_hosts + NLM_HOST_NRHASH; ++chain) {
 606                 hlist_for_each_entry_safe(host, pos, next, chain, h_hash) {
 607                         if (atomic_read(&host->h_count) || host->h_inuse
 608                          || time_before(jiffies, host->h_expires)) {
 609                                 dprintk("nlm_gc_hosts skipping %s (cnt %d use %d exp %ld)\n",
 610                                         host->h_name, atomic_read(&host->h_count),
 611                                         host->h_inuse, host->h_expires);
 612                                 continue;
 613                         }
 614                         dprintk("lockd: delete host %s\n", host->h_name);
 615                         hlist_del_init(&host->h_hash);
 616
 617                         nlm_destroy_host(host);
 618                         nrhosts--;
 619                 }
 620         }
 621
 622         next_gc = jiffies + NLM_HOST_COLLECT;
 623 }
 624
 625
 626 /*
 627  * Manage NSM handles
 628  */
 629 static LIST_HEAD(nsm_handles);
 630 static DEFINE_SPINLOCK(nsm_lock);
 631
 632 static struct nsm_handle *nsm_find(const struct sockaddr *sap,
 633                                    const size_t salen,
 634                                    const char *hostname,
 635                                    const size_t hostname_len,
 636                                    const int create)
 637 {
 638         struct nsm_handle *nsm = NULL;
 639         struct nsm_handle *pos;
 640
 641         if (!sap)
 642                 return NULL;
 643
 644         if (hostname && memchr(hostname, '/', hostname_len) != NULL) {
 645                 if (printk_ratelimit()) {
 646                         printk(KERN_WARNING "Invalid hostname \"%.*s\" "
 647                                             "in NFS lock request\n",
 648                                 (int)hostname_len, hostname);
 649                 }
 650                 return NULL;
 651         }
 652
 653 retry:
 654         spin_lock(&nsm_lock);
 655         list_for_each_entry(pos, &nsm_handles, sm_link) {
 656
 657                 if (hostname && nsm_use_hostnames) {
 658                         if (strlen(pos->sm_name) != hostname_len
 659                          || memcmp(pos->sm_name, hostname, hostname_len))
 660                                 continue;
 661                 } else if (!nlm_cmp_addr(nsm_addr(pos), sap))
 662                         continue;
 663                 atomic_inc(&pos->sm_count);
 664                 kfree(nsm);
 665                 nsm = pos;
 666                 goto found;
 667         }
 668         if (nsm) {
 669                 list_add(&nsm->sm_link, &nsm_handles);
 670                 goto found;
 671         }
 672         spin_unlock(&nsm_lock);
 673
 674         if (!create)
 675                 return NULL;
 676
 677         nsm = kzalloc(sizeof(*nsm) + hostname_len + 1, GFP_KERNEL);
 678         if (nsm == NULL)
 679                 return NULL;
 680
 681         memcpy(nsm_addr(nsm), sap, salen);
 682         nsm->sm_addrlen = salen;
 683         nsm->sm_name = (char *) (nsm + 1);
 684         memcpy(nsm->sm_name, hostname, hostname_len);
 685         nsm->sm_name[hostname_len] = '\0';
 686         nlm_display_address((struct sockaddr *)&nsm->sm_addr,
 687                                 nsm->sm_addrbuf, sizeof(nsm->sm_addrbuf));
 688         atomic_set(&nsm->sm_count, 1);
 689         goto retry;
 690
 691 found:
 692         spin_unlock(&nsm_lock);
 693         return nsm;
 694 }
 695
 696 /*
 697  * Release an NSM handle
 698  */
 699 void
 700 nsm_release(struct nsm_handle *nsm)
 701 {
 702         if (!nsm)
 703                 return;
 704         if (atomic_dec_and_lock(&nsm->sm_count, &nsm_lock)) {
 705                 list_del(&nsm->sm_link);
 706                 spin_unlock(&nsm_lock);
 707                 kfree(nsm);
 708         }
 709 }