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TOMOYO Linux Cross Reference
Linux/fs/afs/server.c

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  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                 _leave(" = %p{%d}", server, atomic_read(&server->usage));
 95         } else {
 96                 _leave(" = NULL [nomem]");
 97         }
 98         return server;
 99 }
100 
101 /*
102  * get an FS-server record for a cell
103  */
104 struct afs_server *afs_lookup_server(struct afs_cell *cell,
105                                      const struct in_addr *addr)
106 {
107         struct afs_server *server, *candidate;
108 
109         _enter("%p,%pI4", cell, &addr->s_addr);
110 
111         /* quick scan of the list to see if we already have the server */
112         read_lock(&cell->servers_lock);
113 
114         list_for_each_entry(server, &cell->servers, link) {
115                 if (server->addr.s_addr == addr->s_addr)
116                         goto found_server_quickly;
117         }
118         read_unlock(&cell->servers_lock);
119 
120         candidate = afs_alloc_server(cell, addr);
121         if (!candidate) {
122                 _leave(" = -ENOMEM");
123                 return ERR_PTR(-ENOMEM);
124         }
125 
126         write_lock(&cell->servers_lock);
127 
128         /* check the cell's server list again */
129         list_for_each_entry(server, &cell->servers, link) {
130                 if (server->addr.s_addr == addr->s_addr)
131                         goto found_server;
132         }
133 
134         _debug("new");
135         server = candidate;
136         if (afs_install_server(server) < 0)
137                 goto server_in_two_cells;
138 
139         afs_get_cell(cell);
140         list_add_tail(&server->link, &cell->servers);
141 
142         write_unlock(&cell->servers_lock);
143         _leave(" = %p{%d}", server, atomic_read(&server->usage));
144         return server;
145 
146         /* found a matching server quickly */
147 found_server_quickly:
148         _debug("found quickly");
149         afs_get_server(server);
150         read_unlock(&cell->servers_lock);
151 no_longer_unused:
152         if (!list_empty(&server->grave)) {
153                 spin_lock(&afs_server_graveyard_lock);
154                 list_del_init(&server->grave);
155                 spin_unlock(&afs_server_graveyard_lock);
156         }
157         _leave(" = %p{%d}", server, atomic_read(&server->usage));
158         return server;
159 
160         /* found a matching server on the second pass */
161 found_server:
162         _debug("found");
163         afs_get_server(server);
164         write_unlock(&cell->servers_lock);
165         kfree(candidate);
166         goto no_longer_unused;
167 
168         /* found a server that seems to be in two cells */
169 server_in_two_cells:
170         write_unlock(&cell->servers_lock);
171         kfree(candidate);
172         printk(KERN_NOTICE "kAFS: Server %pI4 appears to be in two cells\n",
173                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("%pI4", &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                 queue_delayed_work(afs_wq, &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                         mod_delayed_work(afs_wq, &afs_server_reaper, delay);
289                         break;
290                 }
291 
292                 write_lock(&server->cell->servers_lock);
293                 write_lock(&afs_servers_lock);
294                 if (atomic_read(&server->usage) > 0) {
295                         list_del_init(&server->grave);
296                 } else {
297                         list_move_tail(&server->grave, &corpses);
298                         list_del_init(&server->link);
299                         rb_erase(&server->master_rb, &afs_servers);
300                 }
301                 write_unlock(&afs_servers_lock);
302                 write_unlock(&server->cell->servers_lock);
303         }
304 
305         spin_unlock(&afs_server_graveyard_lock);
306 
307         /* now reap the corpses we've extracted */
308         while (!list_empty(&corpses)) {
309                 server = list_entry(corpses.next, struct afs_server, grave);
310                 list_del(&server->grave);
311                 afs_destroy_server(server);
312         }
313 }
314 
315 /*
316  * discard all the server records for rmmod
317  */
318 void __exit afs_purge_servers(void)
319 {
320         afs_server_timeout = 0;
321         mod_delayed_work(afs_wq, &afs_server_reaper, 0);
322 }
323 

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