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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         }
  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,%pI4", cell, &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: Server %pI4 appears to be in two cells\n",
 172                addr);
 173         _leave(" = -EEXIST");
 174         return ERR_PTR(-EEXIST);
 175 }
 176
 177 /*
 178  * look up a server by its IP address
 179  */
 180 struct afs_server *afs_find_server(const struct in_addr *_addr)
 181 {
 182         struct afs_server *server = NULL;
 183         struct rb_node *p;
 184         struct in_addr addr = *_addr;
 185
 186         _enter("%pI4", &addr.s_addr);
 187
 188         read_lock(&afs_servers_lock);
 189
 190         p = afs_servers.rb_node;
 191         while (p) {
 192                 server = rb_entry(p, struct afs_server, master_rb);
 193
 194                 _debug("- consider %p", p);
 195
 196                 if (addr.s_addr < server->addr.s_addr) {
 197                         p = p->rb_left;
 198                 } else if (addr.s_addr > server->addr.s_addr) {
 199                         p = p->rb_right;
 200                 } else {
 201                         afs_get_server(server);
 202                         goto found;
 203                 }
 204         }
 205
 206         server = NULL;
 207 found:
 208         read_unlock(&afs_servers_lock);
 209         ASSERTIFCMP(server, server->addr.s_addr, ==, addr.s_addr);
 210         _leave(" = %p", server);
 211         return server;
 212 }
 213
 214 /*
 215  * destroy a server record
 216  * - removes from the cell list
 217  */
 218 void afs_put_server(struct afs_server *server)
 219 {
 220         if (!server)
 221                 return;
 222
 223         _enter("%p{%d}", server, atomic_read(&server->usage));
 224
 225         _debug("PUT SERVER %d", atomic_read(&server->usage));
 226
 227         ASSERTCMP(atomic_read(&server->usage), >, 0);
 228
 229         if (likely(!atomic_dec_and_test(&server->usage))) {
 230                 _leave("");
 231                 return;
 232         }
 233
 234         afs_flush_callback_breaks(server);
 235
 236         spin_lock(&afs_server_graveyard_lock);
 237         if (atomic_read(&server->usage) == 0) {
 238                 list_move_tail(&server->grave, &afs_server_graveyard);
 239                 server->time_of_death = get_seconds();
 240                 schedule_delayed_work(&afs_server_reaper,
 241                                       afs_server_timeout * HZ);
 242         }
 243         spin_unlock(&afs_server_graveyard_lock);
 244         _leave(" [dead]");
 245 }
 246
 247 /*
 248  * destroy a dead server
 249  */
 250 static void afs_destroy_server(struct afs_server *server)
 251 {
 252         _enter("%p", server);
 253
 254         ASSERTIF(server->cb_break_head != server->cb_break_tail,
 255                  delayed_work_pending(&server->cb_break_work));
 256
 257         ASSERTCMP(server->fs_vnodes.rb_node, ==, NULL);
 258         ASSERTCMP(server->cb_promises.rb_node, ==, NULL);
 259         ASSERTCMP(server->cb_break_head, ==, server->cb_break_tail);
 260         ASSERTCMP(atomic_read(&server->cb_break_n), ==, 0);
 261
 262         afs_put_cell(server->cell);
 263         kfree(server);
 264 }
 265
 266 /*
 267  * reap dead server records
 268  */
 269 static void afs_reap_server(struct work_struct *work)
 270 {
 271         LIST_HEAD(corpses);
 272         struct afs_server *server;
 273         unsigned long delay, expiry;
 274         time_t now;
 275
 276         now = get_seconds();
 277         spin_lock(&afs_server_graveyard_lock);
 278
 279         while (!list_empty(&afs_server_graveyard)) {
 280                 server = list_entry(afs_server_graveyard.next,
 281                                     struct afs_server, grave);
 282
 283                 /* the queue is ordered most dead first */
 284                 expiry = server->time_of_death + afs_server_timeout;
 285                 if (expiry > now) {
 286                         delay = (expiry - now) * HZ;
 287                         if (!schedule_delayed_work(&afs_server_reaper, delay)) {
 288                                 cancel_delayed_work(&afs_server_reaper);
 289                                 schedule_delayed_work(&afs_server_reaper,
 290                                                       delay);
 291                         }
 292                         break;
 293                 }
 294
 295                 write_lock(&server->cell->servers_lock);
 296                 write_lock(&afs_servers_lock);
 297                 if (atomic_read(&server->usage) > 0) {
 298                         list_del_init(&server->grave);
 299                 } else {
 300                         list_move_tail(&server->grave, &corpses);
 301                         list_del_init(&server->link);
 302                         rb_erase(&server->master_rb, &afs_servers);
 303                 }
 304                 write_unlock(&afs_servers_lock);
 305                 write_unlock(&server->cell->servers_lock);
 306         }
 307
 308         spin_unlock(&afs_server_graveyard_lock);
 309
 310         /* now reap the corpses we've extracted */
 311         while (!list_empty(&corpses)) {
 312                 server = list_entry(corpses.next, struct afs_server, grave);
 313                 list_del(&server->grave);
 314                 afs_destroy_server(server);
 315         }
 316 }
 317
 318 /*
 319  * discard all the server records for rmmod
 320  */
 321 void __exit afs_purge_servers(void)
 322 {
 323         afs_server_timeout = 0;
 324         cancel_delayed_work(&afs_server_reaper);
 325         schedule_delayed_work(&afs_server_reaper, 0);
 326 }