1 /* AFS server record management
2 *
3 * Copyright (C) 2002, 2007 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
10 */
11
12 #include <linux/sched.h>
13 #include <linux/slab.h>
14 #include "internal.h"
15
16 static unsigned afs_server_timeout = 10; /* server timeout in seconds */
17
18 static void afs_reap_server(struct work_struct *);
19
20 /* tree of all the servers, indexed by IP address */
21 static struct rb_root afs_servers = RB_ROOT;
22 static DEFINE_RWLOCK(afs_servers_lock);
23
24 /* LRU list of all the servers not currently in use */
25 static LIST_HEAD(afs_server_graveyard);
26 static DEFINE_SPINLOCK(afs_server_graveyard_lock);
27 static DECLARE_DELAYED_WORK(afs_server_reaper, afs_reap_server);
28
29 /*
30 * install a server record in the master tree
31 */
32 static int afs_install_server(struct afs_server *server)
33 {
34 struct afs_server *xserver;
35 struct rb_node **pp, *p;
36 int ret;
37
38 _enter("%p", server);
39
40 write_lock(&afs_servers_lock);
41
42 ret = -EEXIST;
43 pp = &afs_servers.rb_node;
44 p = NULL;
45 while (*pp) {
46 p = *pp;
47 _debug("- consider %p", p);
48 xserver = rb_entry(p, struct afs_server, master_rb);
49 if (server->addr.s_addr < xserver->addr.s_addr)
50 pp = &(*pp)->rb_left;
51 else if (server->addr.s_addr > xserver->addr.s_addr)
52 pp = &(*pp)->rb_right;
53 else
54 goto error;
55 }
56
57 rb_link_node(&server->master_rb, p, pp);
58 rb_insert_color(&server->master_rb, &afs_servers);
59 ret = 0;
60
61 error:
62 write_unlock(&afs_servers_lock);
63 return ret;
64 }
65
66 /*
67 * allocate a new server record
68 */
69 static struct afs_server *afs_alloc_server(struct afs_cell *cell,
70 const struct in_addr *addr)
71 {
72 struct afs_server *server;
73
74 _enter("");
75
76 server = kzalloc(sizeof(struct afs_server), GFP_KERNEL);
77 if (server) {
78 atomic_set(&server->usage, 1);
79 server->cell = cell;
80
81 INIT_LIST_HEAD(&server->link);
82 INIT_LIST_HEAD(&server->grave);
83 init_rwsem(&server->sem);
84 spin_lock_init(&server->fs_lock);
85 server->fs_vnodes = RB_ROOT;
86 server->cb_promises = RB_ROOT;
87 spin_lock_init(&server->cb_lock);
88 init_waitqueue_head(&server->cb_break_waitq);
89 INIT_DELAYED_WORK(&server->cb_break_work,
90 afs_dispatch_give_up_callbacks);
91
92 memcpy(&server->addr, addr, sizeof(struct in_addr));
93 server->addr.s_addr = addr->s_addr;
94 }
95
96 _leave(" = %p{%d}", server, atomic_read(&server->usage));
97 return server;
98 }
99
100 /*
101 * get an FS-server record for a cell
102 */
103 struct afs_server *afs_lookup_server(struct afs_cell *cell,
104 const struct in_addr *addr)
105 {
106 struct afs_server *server, *candidate;
107
108 _enter("%p,"NIPQUAD_FMT, cell, NIPQUAD(addr->s_addr));
109
110 /* quick scan of the list to see if we already have the server */
111 read_lock(&cell->servers_lock);
112
113 list_for_each_entry(server, &cell->servers, link) {
114 if (server->addr.s_addr == addr->s_addr)
115 goto found_server_quickly;
116 }
117 read_unlock(&cell->servers_lock);
118
119 candidate = afs_alloc_server(cell, addr);
120 if (!candidate) {
121 _leave(" = -ENOMEM");
122 return ERR_PTR(-ENOMEM);
123 }
124
125 write_lock(&cell->servers_lock);
126
127 /* check the cell's server list again */
128 list_for_each_entry(server, &cell->servers, link) {
129 if (server->addr.s_addr == addr->s_addr)
130 goto found_server;
131 }
132
133 _debug("new");
134 server = candidate;
135 if (afs_install_server(server) < 0)
136 goto server_in_two_cells;
137
138 afs_get_cell(cell);
139 list_add_tail(&server->link, &cell->servers);
140
141 write_unlock(&cell->servers_lock);
142 _leave(" = %p{%d}", server, atomic_read(&server->usage));
143 return server;
144
145 /* found a matching server quickly */
146 found_server_quickly:
147 _debug("found quickly");
148 afs_get_server(server);
149 read_unlock(&cell->servers_lock);
150 no_longer_unused:
151 if (!list_empty(&server->grave)) {
152 spin_lock(&afs_server_graveyard_lock);
153 list_del_init(&server->grave);
154 spin_unlock(&afs_server_graveyard_lock);
155 }
156 _leave(" = %p{%d}", server, atomic_read(&server->usage));
157 return server;
158
159 /* found a matching server on the second pass */
160 found_server:
161 _debug("found");
162 afs_get_server(server);
163 write_unlock(&cell->servers_lock);
164 kfree(candidate);
165 goto no_longer_unused;
166
167 /* found a server that seems to be in two cells */
168 server_in_two_cells:
169 write_unlock(&cell->servers_lock);
170 kfree(candidate);
171 printk(KERN_NOTICE "kAFS:"
172 " Server "NIPQUAD_FMT" appears to be in two cells\n",
173 NIPQUAD(*addr));
174 _leave(" = -EEXIST");
175 return ERR_PTR(-EEXIST);
176 }
177
178 /*
179 * look up a server by its IP address
180 */
181 struct afs_server *afs_find_server(const struct in_addr *_addr)
182 {
183 struct afs_server *server = NULL;
184 struct rb_node *p;
185 struct in_addr addr = *_addr;
186
187 _enter(NIPQUAD_FMT, NIPQUAD(addr.s_addr));
188
189 read_lock(&afs_servers_lock);
190
191 p = afs_servers.rb_node;
192 while (p) {
193 server = rb_entry(p, struct afs_server, master_rb);
194
195 _debug("- consider %p", p);
196
197 if (addr.s_addr < server->addr.s_addr) {
198 p = p->rb_left;
199 } else if (addr.s_addr > server->addr.s_addr) {
200 p = p->rb_right;
201 } else {
202 afs_get_server(server);
203 goto found;
204 }
205 }
206
207 server = NULL;
208 found:
209 read_unlock(&afs_servers_lock);
210 ASSERTIFCMP(server, server->addr.s_addr, ==, addr.s_addr);
211 _leave(" = %p", server);
212 return server;
213 }
214
215 /*
216 * destroy a server record
217 * - removes from the cell list
218 */
219 void afs_put_server(struct afs_server *server)
220 {
221 if (!server)
222 return;
223
224 _enter("%p{%d}", server, atomic_read(&server->usage));
225
226 _debug("PUT SERVER %d", atomic_read(&server->usage));
227
228 ASSERTCMP(atomic_read(&server->usage), >, 0);
229
230 if (likely(!atomic_dec_and_test(&server->usage))) {
231 _leave("");
232 return;
233 }
234
235 afs_flush_callback_breaks(server);
236
237 spin_lock(&afs_server_graveyard_lock);
238 if (atomic_read(&server->usage) == 0) {
239 list_move_tail(&server->grave, &afs_server_graveyard);
240 server->time_of_death = get_seconds();
241 schedule_delayed_work(&afs_server_reaper,
242 afs_server_timeout * HZ);
243 }
244 spin_unlock(&afs_server_graveyard_lock);
245 _leave(" [dead]");
246 }
247
248 /*
249 * destroy a dead server
250 */
251 static void afs_destroy_server(struct afs_server *server)
252 {
253 _enter("%p", server);
254
255 ASSERTIF(server->cb_break_head != server->cb_break_tail,
256 delayed_work_pending(&server->cb_break_work));
257
258 ASSERTCMP(server->fs_vnodes.rb_node, ==, NULL);
259 ASSERTCMP(server->cb_promises.rb_node, ==, NULL);
260 ASSERTCMP(server->cb_break_head, ==, server->cb_break_tail);
261 ASSERTCMP(atomic_read(&server->cb_break_n), ==, 0);
262
263 afs_put_cell(server->cell);
264 kfree(server);
265 }
266
267 /*
268 * reap dead server records
269 */
270 static void afs_reap_server(struct work_struct *work)
271 {
272 LIST_HEAD(corpses);
273 struct afs_server *server;
274 unsigned long delay, expiry;
275 time_t now;
276
277 now = get_seconds();
278 spin_lock(&afs_server_graveyard_lock);
279
280 while (!list_empty(&afs_server_graveyard)) {
281 server = list_entry(afs_server_graveyard.next,
282 struct afs_server, grave);
283
284 /* the queue is ordered most dead first */
285 expiry = server->time_of_death + afs_server_timeout;
286 if (expiry > now) {
287 delay = (expiry - now) * HZ;
288 if (!schedule_delayed_work(&afs_server_reaper, delay)) {
289 cancel_delayed_work(&afs_server_reaper);
290 schedule_delayed_work(&afs_server_reaper,
291 delay);
292 }
293 break;
294 }
295
296 write_lock(&server->cell->servers_lock);
297 write_lock(&afs_servers_lock);
298 if (atomic_read(&server->usage) > 0) {
299 list_del_init(&server->grave);
300 } else {
301 list_move_tail(&server->grave, &corpses);
302 list_del_init(&server->link);
303 rb_erase(&server->master_rb, &afs_servers);
304 }
305 write_unlock(&afs_servers_lock);
306 write_unlock(&server->cell->servers_lock);
307 }
308
309 spin_unlock(&afs_server_graveyard_lock);
310
311 /* now reap the corpses we've extracted */
312 while (!list_empty(&corpses)) {
313 server = list_entry(corpses.next, struct afs_server, grave);
314 list_del(&server->grave);
315 afs_destroy_server(server);
316 }
317 }
318
319 /*
320 * discard all the server records for rmmod
321 */
322 void __exit afs_purge_servers(void)
323 {
324 afs_server_timeout = 0;
325 cancel_delayed_work(&afs_server_reaper);
326 schedule_delayed_work(&afs_server_reaper, 0);
327 }
328
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