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Linux/fs/afs/volume.c

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  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 }
402 

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