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         volume->bdi.ra_pages    = VM_MAX_READAHEAD*1024/PAGE_SIZE;
 110         ret = bdi_setup_and_register(&volume->bdi, "afs");
 111         if (ret)
 112                 goto error_bdi;
 113
 114         init_rwsem(&volume->server_sem);
 115
 116         /* look up all the applicable server records */
 117         for (loop = 0; loop < 8; loop++) {
 118                 if (vlocation->vldb.srvtmask[loop] & (1 << volume->type)) {
 119                         server = afs_lookup_server(
 120                                volume->cell, &vlocation->vldb.servers[loop]);
 121                         if (IS_ERR(server)) {
 122                                 ret = PTR_ERR(server);
 123                                 goto error_discard;
 124                         }
 125
 126                         volume->servers[volume->nservers] = server;
 127                         volume->nservers++;
 128                 }
 129         }
 130
 131         /* attach the cache and volume location */
 132 #ifdef CONFIG_AFS_FSCACHE
 133         volume->cache = fscache_acquire_cookie(vlocation->cache,
 134                                                &afs_volume_cache_index_def,
 135                                                volume, true);
 136 #endif
 137         afs_get_vlocation(vlocation);
 138         volume->vlocation = vlocation;
 139
 140         vlocation->vols[volume->type] = volume;
 141
 142 success:
 143         _debug("kAFS selected %s volume %08x",
 144                afs_voltypes[volume->type], volume->vid);
 145         up_write(&params->cell->vl_sem);
 146         afs_put_vlocation(vlocation);
 147         _leave(" = %p", volume);
 148         return volume;
 149
 150         /* clean up */
 151 error_up:
 152         up_write(&params->cell->vl_sem);
 153 error:
 154         afs_put_vlocation(vlocation);
 155         _leave(" = %d", ret);
 156         return ERR_PTR(ret);
 157
 158 error_discard:
 159         bdi_destroy(&volume->bdi);
 160 error_bdi:
 161         up_write(&params->cell->vl_sem);
 162
 163         for (loop = volume->nservers - 1; loop >= 0; loop--)
 164                 afs_put_server(volume->servers[loop]);
 165
 166         kfree(volume);
 167         goto error;
 168 }
 169
 170 /*
 171  * destroy a volume record
 172  */
 173 void afs_put_volume(struct afs_volume *volume)
 174 {
 175         struct afs_vlocation *vlocation;
 176         int loop;
 177
 178         if (!volume)
 179                 return;
 180
 181         _enter("%p", volume);
 182
 183         ASSERTCMP(atomic_read(&volume->usage), >, 0);
 184
 185         vlocation = volume->vlocation;
 186
 187         /* to prevent a race, the decrement and the dequeue must be effectively
 188          * atomic */
 189         down_write(&vlocation->cell->vl_sem);
 190
 191         if (likely(!atomic_dec_and_test(&volume->usage))) {
 192                 up_write(&vlocation->cell->vl_sem);
 193                 _leave("");
 194                 return;
 195         }
 196
 197         vlocation->vols[volume->type] = NULL;
 198
 199         up_write(&vlocation->cell->vl_sem);
 200
 201         /* finish cleaning up the volume */
 202 #ifdef CONFIG_AFS_FSCACHE
 203         fscache_relinquish_cookie(volume->cache, 0);
 204 #endif
 205         afs_put_vlocation(vlocation);
 206
 207         for (loop = volume->nservers - 1; loop >= 0; loop--)
 208                 afs_put_server(volume->servers[loop]);
 209
 210         bdi_destroy(&volume->bdi);
 211         kfree(volume);
 212
 213         _leave(" [destroyed]");
 214 }
 215
 216 /*
 217  * pick a server to use to try accessing this volume
 218  * - returns with an elevated usage count on the server chosen
 219  */
 220 struct afs_server *afs_volume_pick_fileserver(struct afs_vnode *vnode)
 221 {
 222         struct afs_volume *volume = vnode->volume;
 223         struct afs_server *server;
 224         int ret, state, loop;
 225
 226         _enter("%s", volume->vlocation->vldb.name);
 227
 228         /* stick with the server we're already using if we can */
 229         if (vnode->server && vnode->server->fs_state == 0) {
 230                 afs_get_server(vnode->server);
 231                 _leave(" = %p [current]", vnode->server);
 232                 return vnode->server;
 233         }
 234
 235         down_read(&volume->server_sem);
 236
 237         /* handle the no-server case */
 238         if (volume->nservers == 0) {
 239                 ret = volume->rjservers ? -ENOMEDIUM : -ESTALE;
 240                 up_read(&volume->server_sem);
 241                 _leave(" = %d [no servers]", ret);
 242                 return ERR_PTR(ret);
 243         }
 244
 245         /* basically, just search the list for the first live server and use
 246          * that */
 247         ret = 0;
 248         for (loop = 0; loop < volume->nservers; loop++) {
 249                 server = volume->servers[loop];
 250                 state = server->fs_state;
 251
 252                 _debug("consider %d [%d]", loop, state);
 253
 254                 switch (state) {
 255                         /* found an apparently healthy server */
 256                 case 0:
 257                         afs_get_server(server);
 258                         up_read(&volume->server_sem);
 259                         _leave(" = %p (picked %08x)",
 260                                server, ntohl(server->addr.s_addr));
 261                         return server;
 262
 263                 case -ENETUNREACH:
 264                         if (ret == 0)
 265                                 ret = state;
 266                         break;
 267
 268                 case -EHOSTUNREACH:
 269                         if (ret == 0 ||
 270                             ret == -ENETUNREACH)
 271                                 ret = state;
 272                         break;
 273
 274                 case -ECONNREFUSED:
 275                         if (ret == 0 ||
 276                             ret == -ENETUNREACH ||
 277                             ret == -EHOSTUNREACH)
 278                                 ret = state;
 279                         break;
 280
 281                 default:
 282                 case -EREMOTEIO:
 283                         if (ret == 0 ||
 284                             ret == -ENETUNREACH ||
 285                             ret == -EHOSTUNREACH ||
 286                             ret == -ECONNREFUSED)
 287                                 ret = state;
 288                         break;
 289                 }
 290         }
 291
 292         /* no available servers
 293          * - TODO: handle the no active servers case better
 294          */
 295         up_read(&volume->server_sem);
 296         _leave(" = %d", ret);
 297         return ERR_PTR(ret);
 298 }
 299
 300 /*
 301  * release a server after use
 302  * - releases the ref on the server struct that was acquired by picking
 303  * - records result of using a particular server to access a volume
 304  * - return 0 to try again, 1 if okay or to issue error
 305  * - the caller must release the server struct if result was 0
 306  */
 307 int afs_volume_release_fileserver(struct afs_vnode *vnode,
 308                                   struct afs_server *server,
 309                                   int result)
 310 {
 311         struct afs_volume *volume = vnode->volume;
 312         unsigned loop;
 313
 314         _enter("%s,%08x,%d",
 315                volume->vlocation->vldb.name, ntohl(server->addr.s_addr),
 316                result);
 317
 318         switch (result) {
 319                 /* success */
 320         case 0:
 321                 server->fs_act_jif = jiffies;
 322                 server->fs_state = 0;
 323                 _leave("");
 324                 return 1;
 325
 326                 /* the fileserver denied all knowledge of the volume */
 327         case -ENOMEDIUM:
 328                 server->fs_act_jif = jiffies;
 329                 down_write(&volume->server_sem);
 330
 331                 /* firstly, find where the server is in the active list (if it
 332                  * is) */
 333                 for (loop = 0; loop < volume->nservers; loop++)
 334                         if (volume->servers[loop] == server)
 335                                 goto present;
 336
 337                 /* no longer there - may have been discarded by another op */
 338                 goto try_next_server_upw;
 339
 340         present:
 341                 volume->nservers--;
 342                 memmove(&volume->servers[loop],
 343                         &volume->servers[loop + 1],
 344                         sizeof(volume->servers[loop]) *
 345                         (volume->nservers - loop));
 346                 volume->servers[volume->nservers] = NULL;
 347                 afs_put_server(server);
 348                 volume->rjservers++;
 349
 350                 if (volume->nservers > 0)
 351                         /* another server might acknowledge its existence */
 352                         goto try_next_server_upw;
 353
 354                 /* handle the case where all the fileservers have rejected the
 355                  * volume
 356                  * - TODO: try asking the fileservers for volume information
 357                  * - TODO: contact the VL server again to see if the volume is
 358                  *         no longer registered
 359                  */
 360                 up_write(&volume->server_sem);
 361                 afs_put_server(server);
 362                 _leave(" [completely rejected]");
 363                 return 1;
 364
 365                 /* problem reaching the server */
 366         case -ENETUNREACH:
 367         case -EHOSTUNREACH:
 368         case -ECONNREFUSED:
 369         case -ETIME:
 370         case -ETIMEDOUT:
 371         case -EREMOTEIO:
 372                 /* mark the server as dead
 373                  * TODO: vary dead timeout depending on error
 374                  */
 375                 spin_lock(&server->fs_lock);
 376                 if (!server->fs_state) {
 377                         server->fs_dead_jif = jiffies + HZ * 10;
 378                         server->fs_state = result;
 379                         printk("kAFS: SERVER DEAD state=%d\n", result);
 380                 }
 381                 spin_unlock(&server->fs_lock);
 382                 goto try_next_server;
 383
 384                 /* miscellaneous error */
 385         default:
 386                 server->fs_act_jif = jiffies;
 387         case -ENOMEM:
 388         case -ENONET:
 389                 /* tell the caller to accept the result */
 390                 afs_put_server(server);
 391                 _leave(" [local failure]");
 392                 return 1;
 393         }
 394
 395         /* tell the caller to loop around and try the next server */
 396 try_next_server_upw:
 397         up_write(&volume->server_sem);
 398 try_next_server:
 399         afs_put_server(server);
 400         _leave(" [try next server]");
 401         return 0;
 402 }