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 AFS_CACHING_SUPPORT
 128         cachefs_acquire_cookie(vlocation->cache,
 129                                &afs_vnode_cache_index_def,
 130                                volume,
 131                                &volume->cache);
 132 #endif
 133
 134         afs_get_vlocation(vlocation);
 135         volume->vlocation = vlocation;
 136
 137         vlocation->vols[volume->type] = volume;
 138
 139 success:
 140         _debug("kAFS selected %s volume %08x",
 141                afs_voltypes[volume->type], volume->vid);
 142         up_write(&params->cell->vl_sem);
 143         afs_put_vlocation(vlocation);
 144         _leave(" = %p", volume);
 145         return volume;
 146
 147         /* clean up */
 148 error_up:
 149         up_write(&params->cell->vl_sem);
 150 error:
 151         afs_put_vlocation(vlocation);
 152         _leave(" = %d", ret);
 153         return ERR_PTR(ret);
 154
 155 error_discard:
 156         up_write(&params->cell->vl_sem);
 157
 158         for (loop = volume->nservers - 1; loop >= 0; loop--)
 159                 afs_put_server(volume->servers[loop]);
 160
 161         kfree(volume);
 162         goto error;
 163 }
 164
 165 /*
 166  * destroy a volume record
 167  */
 168 void afs_put_volume(struct afs_volume *volume)
 169 {
 170         struct afs_vlocation *vlocation;
 171         int loop;
 172
 173         if (!volume)
 174                 return;
 175
 176         _enter("%p", volume);
 177
 178         ASSERTCMP(atomic_read(&volume->usage), >, 0);
 179
 180         vlocation = volume->vlocation;
 181
 182         /* to prevent a race, the decrement and the dequeue must be effectively
 183          * atomic */
 184         down_write(&vlocation->cell->vl_sem);
 185
 186         if (likely(!atomic_dec_and_test(&volume->usage))) {
 187                 up_write(&vlocation->cell->vl_sem);
 188                 _leave("");
 189                 return;
 190         }
 191
 192         vlocation->vols[volume->type] = NULL;
 193
 194         up_write(&vlocation->cell->vl_sem);
 195
 196         /* finish cleaning up the volume */
 197 #ifdef AFS_CACHING_SUPPORT
 198         cachefs_relinquish_cookie(volume->cache, 0);
 199 #endif
 200         afs_put_vlocation(vlocation);
 201
 202         for (loop = volume->nservers - 1; loop >= 0; loop--)
 203                 afs_put_server(volume->servers[loop]);
 204
 205         kfree(volume);
 206
 207         _leave(" [destroyed]");
 208 }
 209
 210 /*
 211  * pick a server to use to try accessing this volume
 212  * - returns with an elevated usage count on the server chosen
 213  */
 214 struct afs_server *afs_volume_pick_fileserver(struct afs_vnode *vnode)
 215 {
 216         struct afs_volume *volume = vnode->volume;
 217         struct afs_server *server;
 218         int ret, state, loop;
 219
 220         _enter("%s", volume->vlocation->vldb.name);
 221
 222         /* stick with the server we're already using if we can */
 223         if (vnode->server && vnode->server->fs_state == 0) {
 224                 afs_get_server(vnode->server);
 225                 _leave(" = %p [current]", vnode->server);
 226                 return vnode->server;
 227         }
 228
 229         down_read(&volume->server_sem);
 230
 231         /* handle the no-server case */
 232         if (volume->nservers == 0) {
 233                 ret = volume->rjservers ? -ENOMEDIUM : -ESTALE;
 234                 up_read(&volume->server_sem);
 235                 _leave(" = %d [no servers]", ret);
 236                 return ERR_PTR(ret);
 237         }
 238
 239         /* basically, just search the list for the first live server and use
 240          * that */
 241         ret = 0;
 242         for (loop = 0; loop < volume->nservers; loop++) {
 243                 server = volume->servers[loop];
 244                 state = server->fs_state;
 245
 246                 _debug("consider %d [%d]", loop, state);
 247
 248                 switch (state) {
 249                         /* found an apparently healthy server */
 250                 case 0:
 251                         afs_get_server(server);
 252                         up_read(&volume->server_sem);
 253                         _leave(" = %p (picked %08x)",
 254                                server, ntohl(server->addr.s_addr));
 255                         return server;
 256
 257                 case -ENETUNREACH:
 258                         if (ret == 0)
 259                                 ret = state;
 260                         break;
 261
 262                 case -EHOSTUNREACH:
 263                         if (ret == 0 ||
 264                             ret == -ENETUNREACH)
 265                                 ret = state;
 266                         break;
 267
 268                 case -ECONNREFUSED:
 269                         if (ret == 0 ||
 270                             ret == -ENETUNREACH ||
 271                             ret == -EHOSTUNREACH)
 272                                 ret = state;
 273                         break;
 274
 275                 default:
 276                 case -EREMOTEIO:
 277                         if (ret == 0 ||
 278                             ret == -ENETUNREACH ||
 279                             ret == -EHOSTUNREACH ||
 280                             ret == -ECONNREFUSED)
 281                                 ret = state;
 282                         break;
 283                 }
 284         }
 285
 286         /* no available servers
 287          * - TODO: handle the no active servers case better
 288          */
 289         up_read(&volume->server_sem);
 290         _leave(" = %d", ret);
 291         return ERR_PTR(ret);
 292 }
 293
 294 /*
 295  * release a server after use
 296  * - releases the ref on the server struct that was acquired by picking
 297  * - records result of using a particular server to access a volume
 298  * - return 0 to try again, 1 if okay or to issue error
 299  * - the caller must release the server struct if result was 0
 300  */
 301 int afs_volume_release_fileserver(struct afs_vnode *vnode,
 302                                   struct afs_server *server,
 303                                   int result)
 304 {
 305         struct afs_volume *volume = vnode->volume;
 306         unsigned loop;
 307
 308         _enter("%s,%08x,%d",
 309                volume->vlocation->vldb.name, ntohl(server->addr.s_addr),
 310                result);
 311
 312         switch (result) {
 313                 /* success */
 314         case 0:
 315                 server->fs_act_jif = jiffies;
 316                 server->fs_state = 0;
 317                 _leave("");
 318                 return 1;
 319
 320                 /* the fileserver denied all knowledge of the volume */
 321         case -ENOMEDIUM:
 322                 server->fs_act_jif = jiffies;
 323                 down_write(&volume->server_sem);
 324
 325                 /* firstly, find where the server is in the active list (if it
 326                  * is) */
 327                 for (loop = 0; loop < volume->nservers; loop++)
 328                         if (volume->servers[loop] == server)
 329                                 goto present;
 330
 331                 /* no longer there - may have been discarded by another op */
 332                 goto try_next_server_upw;
 333
 334         present:
 335                 volume->nservers--;
 336                 memmove(&volume->servers[loop],
 337                         &volume->servers[loop + 1],
 338                         sizeof(volume->servers[loop]) *
 339                         (volume->nservers - loop));
 340                 volume->servers[volume->nservers] = NULL;
 341                 afs_put_server(server);
 342                 volume->rjservers++;
 343
 344                 if (volume->nservers > 0)
 345                         /* another server might acknowledge its existence */
 346                         goto try_next_server_upw;
 347
 348                 /* handle the case where all the fileservers have rejected the
 349                  * volume
 350                  * - TODO: try asking the fileservers for volume information
 351                  * - TODO: contact the VL server again to see if the volume is
 352                  *         no longer registered
 353                  */
 354                 up_write(&volume->server_sem);
 355                 afs_put_server(server);
 356                 _leave(" [completely rejected]");
 357                 return 1;
 358
 359                 /* problem reaching the server */
 360         case -ENETUNREACH:
 361         case -EHOSTUNREACH:
 362         case -ECONNREFUSED:
 363         case -ETIME:
 364         case -ETIMEDOUT:
 365         case -EREMOTEIO:
 366                 /* mark the server as dead
 367                  * TODO: vary dead timeout depending on error
 368                  */
 369                 spin_lock(&server->fs_lock);
 370                 if (!server->fs_state) {
 371                         server->fs_dead_jif = jiffies + HZ * 10;
 372                         server->fs_state = result;
 373                         printk("kAFS: SERVER DEAD state=%d\n", result);
 374                 }
 375                 spin_unlock(&server->fs_lock);
 376                 goto try_next_server;
 377
 378                 /* miscellaneous error */
 379         default:
 380                 server->fs_act_jif = jiffies;
 381         case -ENOMEM:
 382         case -ENONET:
 383                 /* tell the caller to accept the result */
 384                 afs_put_server(server);
 385                 _leave(" [local failure]");
 386                 return 1;
 387         }
 388
 389         /* tell the caller to loop around and try the next server */
 390 try_next_server_upw:
 391         up_write(&volume->server_sem);
 392 try_next_server:
 393         afs_put_server(server);
 394         _leave(" [try next server]");
 395         return 0;
 396 }