NLM: Fix reclaim races
[linux-2.6.git] / 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/sched.h>
13 #include <linux/slab.h>
14 #include <linux/in.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
22 #define NLMDBG_FACILITY         NLMDBG_HOSTCACHE
23 #define NLM_HOST_MAX            64
24 #define NLM_HOST_NRHASH         32
25 #define NLM_ADDRHASH(addr)      (ntohl(addr) & (NLM_HOST_NRHASH-1))
26 #define NLM_HOST_REBIND         (60 * HZ)
27 #define NLM_HOST_EXPIRE         ((nrhosts > NLM_HOST_MAX)? 300 * HZ : 120 * HZ)
28 #define NLM_HOST_COLLECT        ((nrhosts > NLM_HOST_MAX)? 120 * HZ :  60 * HZ)
29 #define NLM_HOST_ADDR(sv)       (&(sv)->s_nlmclnt->cl_xprt->addr)
30
31 static struct nlm_host *        nlm_hosts[NLM_HOST_NRHASH];
32 static unsigned long            next_gc;
33 static int                      nrhosts;
34 static DEFINE_MUTEX(nlm_host_mutex);
35
36
37 static void                     nlm_gc_hosts(void);
38
39 /*
40  * Find an NLM server handle in the cache. If there is none, create it.
41  */
42 struct nlm_host *
43 nlmclnt_lookup_host(struct sockaddr_in *sin, int proto, int version)
44 {
45         return nlm_lookup_host(0, sin, proto, version);
46 }
47
48 /*
49  * Find an NLM client handle in the cache. If there is none, create it.
50  */
51 struct nlm_host *
52 nlmsvc_lookup_host(struct svc_rqst *rqstp)
53 {
54         return nlm_lookup_host(1, &rqstp->rq_addr,
55                                rqstp->rq_prot, rqstp->rq_vers);
56 }
57
58 /*
59  * Common host lookup routine for server & client
60  */
61 struct nlm_host *
62 nlm_lookup_host(int server, struct sockaddr_in *sin,
63                                         int proto, int version)
64 {
65         struct nlm_host *host, **hp;
66         u32             addr;
67         int             hash;
68
69         dprintk("lockd: nlm_lookup_host(%08x, p=%d, v=%d)\n",
70                         (unsigned)(sin? ntohl(sin->sin_addr.s_addr) : 0), proto, version);
71
72         hash = NLM_ADDRHASH(sin->sin_addr.s_addr);
73
74         /* Lock hash table */
75         mutex_lock(&nlm_host_mutex);
76
77         if (time_after_eq(jiffies, next_gc))
78                 nlm_gc_hosts();
79
80         for (hp = &nlm_hosts[hash]; (host = *hp) != 0; hp = &host->h_next) {
81                 if (host->h_proto != proto)
82                         continue;
83                 if (host->h_version != version)
84                         continue;
85                 if (host->h_server != server)
86                         continue;
87
88                 if (nlm_cmp_addr(&host->h_addr, sin)) {
89                         if (hp != nlm_hosts + hash) {
90                                 *hp = host->h_next;
91                                 host->h_next = nlm_hosts[hash];
92                                 nlm_hosts[hash] = host;
93                         }
94                         nlm_get_host(host);
95                         mutex_unlock(&nlm_host_mutex);
96                         return host;
97                 }
98         }
99
100         /* Ooops, no host found, create it */
101         dprintk("lockd: creating host entry\n");
102
103         if (!(host = (struct nlm_host *) kmalloc(sizeof(*host), GFP_KERNEL)))
104                 goto nohost;
105         memset(host, 0, sizeof(*host));
106
107         addr = sin->sin_addr.s_addr;
108         sprintf(host->h_name, "%u.%u.%u.%u", NIPQUAD(addr));
109
110         host->h_addr       = *sin;
111         host->h_addr.sin_port = 0;      /* ouch! */
112         host->h_version    = version;
113         host->h_proto      = proto;
114         host->h_rpcclnt    = NULL;
115         mutex_init(&host->h_mutex);
116         host->h_nextrebind = jiffies + NLM_HOST_REBIND;
117         host->h_expires    = jiffies + NLM_HOST_EXPIRE;
118         atomic_set(&host->h_count, 1);
119         init_waitqueue_head(&host->h_gracewait);
120         init_rwsem(&host->h_rwsem);
121         host->h_state      = 0;                 /* pseudo NSM state */
122         host->h_nsmstate   = 0;                 /* real NSM state */
123         host->h_server     = server;
124         host->h_next       = nlm_hosts[hash];
125         nlm_hosts[hash]    = host;
126         INIT_LIST_HEAD(&host->h_lockowners);
127         spin_lock_init(&host->h_lock);
128         INIT_LIST_HEAD(&host->h_granted);
129         INIT_LIST_HEAD(&host->h_reclaim);
130
131         if (++nrhosts > NLM_HOST_MAX)
132                 next_gc = 0;
133
134 nohost:
135         mutex_unlock(&nlm_host_mutex);
136         return host;
137 }
138
139 struct nlm_host *
140 nlm_find_client(void)
141 {
142         /* find a nlm_host for a client for which h_killed == 0.
143          * and return it
144          */
145         int hash;
146         mutex_lock(&nlm_host_mutex);
147         for (hash = 0 ; hash < NLM_HOST_NRHASH; hash++) {
148                 struct nlm_host *host, **hp;
149                 for (hp = &nlm_hosts[hash]; (host = *hp) != 0; hp = &host->h_next) {
150                         if (host->h_server &&
151                             host->h_killed == 0) {
152                                 nlm_get_host(host);
153                                 mutex_unlock(&nlm_host_mutex);
154                                 return host;
155                         }
156                 }
157         }
158         mutex_unlock(&nlm_host_mutex);
159         return NULL;
160 }
161
162                                 
163 /*
164  * Create the NLM RPC client for an NLM peer
165  */
166 struct rpc_clnt *
167 nlm_bind_host(struct nlm_host *host)
168 {
169         struct rpc_clnt *clnt;
170         struct rpc_xprt *xprt;
171
172         dprintk("lockd: nlm_bind_host(%08x)\n",
173                         (unsigned)ntohl(host->h_addr.sin_addr.s_addr));
174
175         /* Lock host handle */
176         mutex_lock(&host->h_mutex);
177
178         /* If we've already created an RPC client, check whether
179          * RPC rebind is required
180          */
181         if ((clnt = host->h_rpcclnt) != NULL) {
182                 xprt = clnt->cl_xprt;
183                 if (time_after_eq(jiffies, host->h_nextrebind)) {
184                         rpc_force_rebind(clnt);
185                         host->h_nextrebind = jiffies + NLM_HOST_REBIND;
186                         dprintk("lockd: next rebind in %ld jiffies\n",
187                                         host->h_nextrebind - jiffies);
188                 }
189         } else {
190                 xprt = xprt_create_proto(host->h_proto, &host->h_addr, NULL);
191                 if (IS_ERR(xprt))
192                         goto forgetit;
193
194                 xprt_set_timeout(&xprt->timeout, 5, nlmsvc_timeout);
195                 xprt->resvport = 1;     /* NLM requires a reserved port */
196
197                 /* Existing NLM servers accept AUTH_UNIX only */
198                 clnt = rpc_new_client(xprt, host->h_name, &nlm_program,
199                                         host->h_version, RPC_AUTH_UNIX);
200                 if (IS_ERR(clnt))
201                         goto forgetit;
202                 clnt->cl_autobind = 1;  /* turn on pmap queries */
203                 clnt->cl_softrtry = 1; /* All queries are soft */
204
205                 host->h_rpcclnt = clnt;
206         }
207
208         mutex_unlock(&host->h_mutex);
209         return clnt;
210
211 forgetit:
212         printk("lockd: couldn't create RPC handle for %s\n", host->h_name);
213         mutex_unlock(&host->h_mutex);
214         return NULL;
215 }
216
217 /*
218  * Force a portmap lookup of the remote lockd port
219  */
220 void
221 nlm_rebind_host(struct nlm_host *host)
222 {
223         dprintk("lockd: rebind host %s\n", host->h_name);
224         if (host->h_rpcclnt && time_after_eq(jiffies, host->h_nextrebind)) {
225                 rpc_force_rebind(host->h_rpcclnt);
226                 host->h_nextrebind = jiffies + NLM_HOST_REBIND;
227         }
228 }
229
230 /*
231  * Increment NLM host count
232  */
233 struct nlm_host * nlm_get_host(struct nlm_host *host)
234 {
235         if (host) {
236                 dprintk("lockd: get host %s\n", host->h_name);
237                 atomic_inc(&host->h_count);
238                 host->h_expires = jiffies + NLM_HOST_EXPIRE;
239         }
240         return host;
241 }
242
243 /*
244  * Release NLM host after use
245  */
246 void nlm_release_host(struct nlm_host *host)
247 {
248         if (host != NULL) {
249                 dprintk("lockd: release host %s\n", host->h_name);
250                 BUG_ON(atomic_read(&host->h_count) < 0);
251                 if (atomic_dec_and_test(&host->h_count)) {
252                         BUG_ON(!list_empty(&host->h_lockowners));
253                         BUG_ON(!list_empty(&host->h_granted));
254                         BUG_ON(!list_empty(&host->h_reclaim));
255                 }
256         }
257 }
258
259 /*
260  * Shut down the hosts module.
261  * Note that this routine is called only at server shutdown time.
262  */
263 void
264 nlm_shutdown_hosts(void)
265 {
266         struct nlm_host *host;
267         int             i;
268
269         dprintk("lockd: shutting down host module\n");
270         mutex_lock(&nlm_host_mutex);
271
272         /* First, make all hosts eligible for gc */
273         dprintk("lockd: nuking all hosts...\n");
274         for (i = 0; i < NLM_HOST_NRHASH; i++) {
275                 for (host = nlm_hosts[i]; host; host = host->h_next)
276                         host->h_expires = jiffies - 1;
277         }
278
279         /* Then, perform a garbage collection pass */
280         nlm_gc_hosts();
281         mutex_unlock(&nlm_host_mutex);
282
283         /* complain if any hosts are left */
284         if (nrhosts) {
285                 printk(KERN_WARNING "lockd: couldn't shutdown host module!\n");
286                 dprintk("lockd: %d hosts left:\n", nrhosts);
287                 for (i = 0; i < NLM_HOST_NRHASH; i++) {
288                         for (host = nlm_hosts[i]; host; host = host->h_next) {
289                                 dprintk("       %s (cnt %d use %d exp %ld)\n",
290                                         host->h_name, atomic_read(&host->h_count),
291                                         host->h_inuse, host->h_expires);
292                         }
293                 }
294         }
295 }
296
297 /*
298  * Garbage collect any unused NLM hosts.
299  * This GC combines reference counting for async operations with
300  * mark & sweep for resources held by remote clients.
301  */
302 static void
303 nlm_gc_hosts(void)
304 {
305         struct nlm_host **q, *host;
306         struct rpc_clnt *clnt;
307         int             i;
308
309         dprintk("lockd: host garbage collection\n");
310         for (i = 0; i < NLM_HOST_NRHASH; i++) {
311                 for (host = nlm_hosts[i]; host; host = host->h_next)
312                         host->h_inuse = 0;
313         }
314
315         /* Mark all hosts that hold locks, blocks or shares */
316         nlmsvc_mark_resources();
317
318         for (i = 0; i < NLM_HOST_NRHASH; i++) {
319                 q = &nlm_hosts[i];
320                 while ((host = *q) != NULL) {
321                         if (atomic_read(&host->h_count) || host->h_inuse
322                          || time_before(jiffies, host->h_expires)) {
323                                 dprintk("nlm_gc_hosts skipping %s (cnt %d use %d exp %ld)\n",
324                                         host->h_name, atomic_read(&host->h_count),
325                                         host->h_inuse, host->h_expires);
326                                 q = &host->h_next;
327                                 continue;
328                         }
329                         dprintk("lockd: delete host %s\n", host->h_name);
330                         *q = host->h_next;
331                         /* Don't unmonitor hosts that have been invalidated */
332                         if (host->h_monitored && !host->h_killed)
333                                 nsm_unmonitor(host);
334                         if ((clnt = host->h_rpcclnt) != NULL) {
335                                 if (atomic_read(&clnt->cl_users)) {
336                                         printk(KERN_WARNING
337                                                 "lockd: active RPC handle\n");
338                                         clnt->cl_dead = 1;
339                                 } else {
340                                         rpc_destroy_client(host->h_rpcclnt);
341                                 }
342                         }
343                         kfree(host);
344                         nrhosts--;
345                 }
346         }
347
348         next_gc = jiffies + NLM_HOST_COLLECT;
349 }
350