fs/afs/volume.c

   1 /* AFS volume 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/kernel.h>
  13 #include <linux/module.h>
  14 #include <linux/init.h>
  15 #include <linux/slab.h>
  16 #include <linux/fs.h>
  17 #include <linux/pagemap.h>
  18 #include <linux/sched.h>
  19 #include "internal.h"
  20
  21 static const char *afs_voltypes[] = { "R/W", "R/O", "BAK" };
  22
  23 /*
  24  * lookup a volume by name
  25  * - this can be one of the following:
  26  *      "%[cell:]volume[.]"             R/W volume
  27  *      "#[cell:]volume[.]"             R/O or R/W volume (rwparent=0),
  28  *                                       or R/W (rwparent=1) volume
  29  *      "%[cell:]volume.readonly"       R/O volume
  30  *      "#[cell:]volume.readonly"       R/O volume
  31  *      "%[cell:]volume.backup"         Backup volume
  32  *      "#[cell:]volume.backup"         Backup volume
  33  *
  34  * The cell name is optional, and defaults to the current cell.
  35  *
  36  * See "The Rules of Mount Point Traversal" in Chapter 5 of the AFS SysAdmin
  37  * Guide
  38  * - Rule 1: Explicit type suffix forces access of that type or nothing
  39  *           (no suffix, then use Rule 2 & 3)
  40  * - Rule 2: If parent volume is R/O, then mount R/O volume by preference, R/W
  41  *           if not available
  42  * - Rule 3: If parent volume is R/W, then only mount R/W volume unless
  43  *           explicitly told otherwise
  44  */
  45 struct afs_volume *afs_volume_lookup(struct afs_mount_params *params)
  46 {
  47         struct afs_vlocation *vlocation = NULL;
  48         struct afs_volume *volume = NULL;
  49         struct afs_server *server = NULL;
  50         char srvtmask;
  51         int ret, loop;
  52
  53         _enter("{%*.*s,%d}",
  54                params->volnamesz, params->volnamesz, params->volname, params->rwpath);
  55
  56         /* lookup the volume location record */
  57         vlocation = afs_vlocation_lookup(params->cell, params->key,
  58                                          params->volname, params->volnamesz);
  59         if (IS_ERR(vlocation)) {
  60                 ret = PTR_ERR(vlocation);
  61                 vlocation = NULL;
  62                 goto error;
  63         }
  64
  65         /* make the final decision on the type we want */
  66         ret = -ENOMEDIUM;
  67         if (params->force && !(vlocation->vldb.vidmask & (1 << params->type)))
  68                 goto error;
  69
  70         srvtmask = 0;
  71         for (loop = 0; loop < vlocation->vldb.nservers; loop++)
  72                 srvtmask |= vlocation->vldb.srvtmask[loop];
  73
  74         if (params->force) {
  75                 if (!(srvtmask & (1 << params->type)))
  76                         goto error;
  77         } else if (srvtmask & AFS_VOL_VTM_RO) {
  78                 params->type = AFSVL_ROVOL;
  79         } else if (srvtmask & AFS_VOL_VTM_RW) {
  80                 params->type = AFSVL_RWVOL;
  81         } else {
  82                 goto error;
  83         }
  84
  85         down_write(&params->cell->vl_sem);
  86
  87         /* is the volume already active? */
  88         if (vlocation->vols[params->type]) {
  89                 /* yes - re-use it */
  90                 volume = vlocation->vols[params->type];
  91                 afs_get_volume(volume);
  92                 goto success;
  93         }
  94
  95         /* create a new volume record */
  96         _debug("creating new volume record");
  97
  98         ret = -ENOMEM;
  99         volume = kzalloc(sizeof(struct afs_volume), GFP_KERNEL);
 100         if (!volume)
 101                 goto error_up;
 102
 103         atomic_set(&volume->usage, 1);
 104         volume->type            = params->type;
 105         volume->type_force      = params->force;
 106         volume->cell            = params->cell;
 107         volume->vid             = vlocation->vldb.vid[params->type];
 108
 109         init_rwsem(&volume->server_sem);
 110
 111         /* look up all the applicable server records */
 112         for (loop = 0; loop < 8; loop++) {
 113                 if (vlocation->vldb.srvtmask[loop] & (1 << volume->type)) {
 114                         server = afs_lookup_server(
 115                                volume->cell, &vlocation->vldb.servers[loop]);
 116                         if (IS_ERR(server)) {
 117                                 ret = PTR_ERR(server);
 118                                 goto error_discard;
 119                         }
 120
 121                         volume->servers[volume->nservers] = server;
 122                         volume->nservers++;
 123                 }
 124         }
 125
 126         /* attach the cache and volume location */
 127 #ifdef CONFIG_AFS_FSCACHE
 128         volume->cache = fscache_acquire_cookie(vlocation->cache,
 129                                                &afs_volume_cache_index_def,
 130                                                volume, true);
 131 #endif
 132         afs_get_vlocation(vlocation);
 133         volume->vlocation = vlocation;
 134
 135         vlocation->vols[volume->type] = volume;
 136
 137 success:
 138         _debug("kAFS selected %s volume %08x",
 139                afs_voltypes[volume->type], volume->vid);
 140         up_write(&params->cell->vl_sem);
 141         afs_put_vlocation(vlocation);
 142         _leave(" = %p", volume);
 143         return volume;
 144
 145         /* clean up */
 146 error_up:
 147         up_write(&params->cell->vl_sem);
 148 error:
 149         afs_put_vlocation(vlocation);
 150         _leave(" = %d", ret);
 151         return ERR_PTR(ret);
 152
 153 error_discard:
 154         up_write(&params->cell->vl_sem);
 155
 156         for (loop = volume->nservers - 1; loop >= 0; loop--)
 157                 afs_put_server(volume->servers[loop]);
 158
 159         kfree(volume);
 160         goto error;
 161 }
 162
 163 /*
 164  * destroy a volume record
 165  */
 166 void afs_put_volume(struct afs_volume *volume)
 167 {
 168         struct afs_vlocation *vlocation;
 169         int loop;
 170
 171         if (!volume)
 172                 return;
 173
 174         _enter("%p", volume);
 175
 176         ASSERTCMP(atomic_read(&volume->usage), >, 0);
 177
 178         vlocation = volume->vlocation;
 179
 180         /* to prevent a race, the decrement and the dequeue must be effectively
 181          * atomic */
 182         down_write(&vlocation->cell->vl_sem);
 183
 184         if (likely(!atomic_dec_and_test(&volume->usage))) {
 185                 up_write(&vlocation->cell->vl_sem);
 186                 _leave("");
 187                 return;
 188         }
 189
 190         vlocation->vols[volume->type] = NULL;
 191
 192         up_write(&vlocation->cell->vl_sem);
 193
 194         /* finish cleaning up the volume */
 195 #ifdef CONFIG_AFS_FSCACHE
 196         fscache_relinquish_cookie(volume->cache, 0);
 197 #endif
 198         afs_put_vlocation(vlocation);
 199
 200         for (loop = volume->nservers - 1; loop >= 0; loop--)
 201                 afs_put_server(volume->servers[loop]);
 202
 203         kfree(volume);
 204
 205         _leave(" [destroyed]");
 206 }
 207
 208 /*
 209  * pick a server to use to try accessing this volume
 210  * - returns with an elevated usage count on the server chosen
 211  */
 212 struct afs_server *afs_volume_pick_fileserver(struct afs_vnode *vnode)
 213 {
 214         struct afs_volume *volume = vnode->volume;
 215         struct afs_server *server;
 216         int ret, state, loop;
 217
 218         _enter("%s", volume->vlocation->vldb.name);
 219
 220         /* stick with the server we're already using if we can */
 221         if (vnode->server && vnode->server->fs_state == 0) {
 222                 afs_get_server(vnode->server);
 223                 _leave(" = %p [current]", vnode->server);
 224                 return vnode->server;
 225         }
 226
 227         down_read(&volume->server_sem);
 228
 229         /* handle the no-server case */
 230         if (volume->nservers == 0) {
 231                 ret = volume->rjservers ? -ENOMEDIUM : -ESTALE;
 232                 up_read(&volume->server_sem);
 233                 _leave(" = %d [no servers]", ret);
 234                 return ERR_PTR(ret);
 235         }
 236
 237         /* basically, just search the list for the first live server and use
 238          * that */
 239         ret = 0;
 240         for (loop = 0; loop < volume->nservers; loop++) {
 241                 server = volume->servers[loop];
 242                 state = server->fs_state;
 243
 244                 _debug("consider %d [%d]", loop, state);
 245
 246                 switch (state) {
 247                         /* found an apparently healthy server */
 248                 case 0:
 249                         afs_get_server(server);
 250                         up_read(&volume->server_sem);
 251                         _leave(" = %p (picked %08x)",
 252                                server, ntohl(server->addr.s_addr));
 253                         return server;
 254
 255                 case -ENETUNREACH:
 256                         if (ret == 0)
 257                                 ret = state;
 258                         break;
 259
 260                 case -EHOSTUNREACH:
 261                         if (ret == 0 ||
 262                             ret == -ENETUNREACH)
 263                                 ret = state;
 264                         break;
 265
 266                 case -ECONNREFUSED:
 267                         if (ret == 0 ||
 268                             ret == -ENETUNREACH ||
 269                             ret == -EHOSTUNREACH)
 270                                 ret = state;
 271                         break;
 272
 273                 default:
 274                 case -EREMOTEIO:
 275                         if (ret == 0 ||
 276                             ret == -ENETUNREACH ||
 277                             ret == -EHOSTUNREACH ||
 278                             ret == -ECONNREFUSED)
 279                                 ret = state;
 280                         break;
 281                 }
 282         }
 283
 284         /* no available servers
 285          * - TODO: handle the no active servers case better
 286          */
 287         up_read(&volume->server_sem);
 288         _leave(" = %d", ret);
 289         return ERR_PTR(ret);
 290 }
 291
 292 /*
 293  * release a server after use
 294  * - releases the ref on the server struct that was acquired by picking
 295  * - records result of using a particular server to access a volume
 296  * - return 0 to try again, 1 if okay or to issue error
 297  * - the caller must release the server struct if result was 0
 298  */
 299 int afs_volume_release_fileserver(struct afs_vnode *vnode,
 300                                   struct afs_server *server,
 301                                   int result)
 302 {
 303         struct afs_volume *volume = vnode->volume;
 304         unsigned loop;
 305
 306         _enter("%s,%08x,%d",
 307                volume->vlocation->vldb.name, ntohl(server->addr.s_addr),
 308                result);
 309
 310         switch (result) {
 311                 /* success */
 312         case 0:
 313                 server->fs_act_jif = jiffies;
 314                 server->fs_state = 0;
 315                 _leave("");
 316                 return 1;
 317
 318                 /* the fileserver denied all knowledge of the volume */
 319         case -ENOMEDIUM:
 320                 server->fs_act_jif = jiffies;
 321                 down_write(&volume->server_sem);
 322
 323                 /* firstly, find where the server is in the active list (if it
 324                  * is) */
 325                 for (loop = 0; loop < volume->nservers; loop++)
 326                         if (volume->servers[loop] == server)
 327                                 goto present;
 328
 329                 /* no longer there - may have been discarded by another op */
 330                 goto try_next_server_upw;
 331
 332         present:
 333                 volume->nservers--;
 334                 memmove(&volume->servers[loop],
 335                         &volume->servers[loop + 1],
 336                         sizeof(volume->servers[loop]) *
 337                         (volume->nservers - loop));
 338                 volume->servers[volume->nservers] = NULL;
 339                 afs_put_server(server);
 340                 volume->rjservers++;
 341
 342                 if (volume->nservers > 0)
 343                         /* another server might acknowledge its existence */
 344                         goto try_next_server_upw;
 345
 346                 /* handle the case where all the fileservers have rejected the
 347                  * volume
 348                  * - TODO: try asking the fileservers for volume information
 349                  * - TODO: contact the VL server again to see if the volume is
 350                  *         no longer registered
 351                  */
 352                 up_write(&volume->server_sem);
 353                 afs_put_server(server);
 354                 _leave(" [completely rejected]");
 355                 return 1;
 356
 357                 /* problem reaching the server */
 358         case -ENETUNREACH:
 359         case -EHOSTUNREACH:
 360         case -ECONNREFUSED:
 361         case -ETIME:
 362         case -ETIMEDOUT:
 363         case -EREMOTEIO:
 364                 /* mark the server as dead
 365                  * TODO: vary dead timeout depending on error
 366                  */
 367                 spin_lock(&server->fs_lock);
 368                 if (!server->fs_state) {
 369                         server->fs_dead_jif = jiffies + HZ * 10;
 370                         server->fs_state = result;
 371                         printk("kAFS: SERVER DEAD state=%d\n", result);
 372                 }
 373                 spin_unlock(&server->fs_lock);
 374                 goto try_next_server;
 375
 376                 /* miscellaneous error */
 377         default:
 378                 server->fs_act_jif = jiffies;
 379         case -ENOMEM:
 380         case -ENONET:
 381                 /* tell the caller to accept the result */
 382                 afs_put_server(server);
 383                 _leave(" [local failure]");
 384                 return 1;
 385         }
 386
 387         /* tell the caller to loop around and try the next server */
 388 try_next_server_upw:
 389         up_write(&volume->server_sem);
 390 try_next_server:
 391         afs_put_server(server);
 392         _leave(" [try next server]");
 393         return 0;
 394 }