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