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Linux/fs/afs/cell.c

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  1 /* AFS cell and server record management
  2  *
  3  * Copyright (C) 2002 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/module.h>
 13 #include <linux/slab.h>
 14 #include <linux/key.h>
 15 #include <linux/ctype.h>
 16 #include <linux/dns_resolver.h>
 17 #include <linux/sched.h>
 18 #include <keys/rxrpc-type.h>
 19 #include "internal.h"
 20 
 21 DECLARE_RWSEM(afs_proc_cells_sem);
 22 LIST_HEAD(afs_proc_cells);
 23 
 24 static LIST_HEAD(afs_cells);
 25 static DEFINE_RWLOCK(afs_cells_lock);
 26 static DECLARE_RWSEM(afs_cells_sem); /* add/remove serialisation */
 27 static DECLARE_WAIT_QUEUE_HEAD(afs_cells_freeable_wq);
 28 static struct afs_cell *afs_cell_root;
 29 
 30 /*
 31  * allocate a cell record and fill in its name, VL server address list and
 32  * allocate an anonymous key
 33  */
 34 static struct afs_cell *afs_cell_alloc(const char *name, unsigned namelen,
 35                                        char *vllist)
 36 {
 37         struct afs_cell *cell;
 38         struct key *key;
 39         char keyname[4 + AFS_MAXCELLNAME + 1], *cp, *dp, *next;
 40         char  *dvllist = NULL, *_vllist = NULL;
 41         char  delimiter = ':';
 42         int ret;
 43 
 44         _enter("%*.*s,%s", namelen, namelen, name ?: "", vllist);
 45 
 46         BUG_ON(!name); /* TODO: want to look up "this cell" in the cache */
 47 
 48         if (namelen > AFS_MAXCELLNAME) {
 49                 _leave(" = -ENAMETOOLONG");
 50                 return ERR_PTR(-ENAMETOOLONG);
 51         }
 52 
 53         /* allocate and initialise a cell record */
 54         cell = kzalloc(sizeof(struct afs_cell) + namelen + 1, GFP_KERNEL);
 55         if (!cell) {
 56                 _leave(" = -ENOMEM");
 57                 return ERR_PTR(-ENOMEM);
 58         }
 59 
 60         memcpy(cell->name, name, namelen);
 61         cell->name[namelen] = 0;
 62 
 63         atomic_set(&cell->usage, 1);
 64         INIT_LIST_HEAD(&cell->link);
 65         rwlock_init(&cell->servers_lock);
 66         INIT_LIST_HEAD(&cell->servers);
 67         init_rwsem(&cell->vl_sem);
 68         INIT_LIST_HEAD(&cell->vl_list);
 69         spin_lock_init(&cell->vl_lock);
 70 
 71         /* if the ip address is invalid, try dns query */
 72         if (!vllist || strlen(vllist) < 7) {
 73                 ret = dns_query("afsdb", name, namelen, "ipv4", &dvllist, NULL);
 74                 if (ret < 0) {
 75                         if (ret == -ENODATA || ret == -EAGAIN || ret == -ENOKEY)
 76                                 /* translate these errors into something
 77                                  * userspace might understand */
 78                                 ret = -EDESTADDRREQ;
 79                         _leave(" = %d", ret);
 80                         return ERR_PTR(ret);
 81                 }
 82                 _vllist = dvllist;
 83 
 84                 /* change the delimiter for user-space reply */
 85                 delimiter = ',';
 86 
 87         } else {
 88                 _vllist = vllist;
 89         }
 90 
 91         /* fill in the VL server list from the rest of the string */
 92         do {
 93                 unsigned a, b, c, d;
 94 
 95                 next = strchr(_vllist, delimiter);
 96                 if (next)
 97                         *next++ = 0;
 98 
 99                 if (sscanf(_vllist, "%u.%u.%u.%u", &a, &b, &c, &d) != 4)
100                         goto bad_address;
101 
102                 if (a > 255 || b > 255 || c > 255 || d > 255)
103                         goto bad_address;
104 
105                 cell->vl_addrs[cell->vl_naddrs++].s_addr =
106                         htonl((a << 24) | (b << 16) | (c << 8) | d);
107 
108         } while (cell->vl_naddrs < AFS_CELL_MAX_ADDRS && (_vllist = next));
109 
110         /* create a key to represent an anonymous user */
111         memcpy(keyname, "afs@", 4);
112         dp = keyname + 4;
113         cp = cell->name;
114         do {
115                 *dp++ = toupper(*cp);
116         } while (*cp++);
117 
118         key = rxrpc_get_null_key(keyname);
119         if (IS_ERR(key)) {
120                 _debug("no key");
121                 ret = PTR_ERR(key);
122                 goto error;
123         }
124         cell->anonymous_key = key;
125 
126         _debug("anon key %p{%x}",
127                cell->anonymous_key, key_serial(cell->anonymous_key));
128 
129         _leave(" = %p", cell);
130         return cell;
131 
132 bad_address:
133         printk(KERN_ERR "kAFS: bad VL server IP address\n");
134         ret = -EINVAL;
135 error:
136         key_put(cell->anonymous_key);
137         kfree(dvllist);
138         kfree(cell);
139         _leave(" = %d", ret);
140         return ERR_PTR(ret);
141 }
142 
143 /*
144  * afs_cell_crate() - create a cell record
145  * @name:       is the name of the cell.
146  * @namsesz:    is the strlen of the cell name.
147  * @vllist:     is a colon separated list of IP addresses in "a.b.c.d" format.
148  * @retref:     is T to return the cell reference when the cell exists.
149  */
150 struct afs_cell *afs_cell_create(const char *name, unsigned namesz,
151                                  char *vllist, bool retref)
152 {
153         struct afs_cell *cell;
154         int ret;
155 
156         _enter("%*.*s,%s", namesz, namesz, name ?: "", vllist);
157 
158         down_write(&afs_cells_sem);
159         read_lock(&afs_cells_lock);
160         list_for_each_entry(cell, &afs_cells, link) {
161                 if (strncasecmp(cell->name, name, namesz) == 0)
162                         goto duplicate_name;
163         }
164         read_unlock(&afs_cells_lock);
165 
166         cell = afs_cell_alloc(name, namesz, vllist);
167         if (IS_ERR(cell)) {
168                 _leave(" = %ld", PTR_ERR(cell));
169                 up_write(&afs_cells_sem);
170                 return cell;
171         }
172 
173         /* add a proc directory for this cell */
174         ret = afs_proc_cell_setup(cell);
175         if (ret < 0)
176                 goto error;
177 
178 #ifdef CONFIG_AFS_FSCACHE
179         /* put it up for caching (this never returns an error) */
180         cell->cache = fscache_acquire_cookie(afs_cache_netfs.primary_index,
181                                              &afs_cell_cache_index_def,
182                                              cell);
183 #endif
184 
185         /* add to the cell lists */
186         write_lock(&afs_cells_lock);
187         list_add_tail(&cell->link, &afs_cells);
188         write_unlock(&afs_cells_lock);
189 
190         down_write(&afs_proc_cells_sem);
191         list_add_tail(&cell->proc_link, &afs_proc_cells);
192         up_write(&afs_proc_cells_sem);
193         up_write(&afs_cells_sem);
194 
195         _leave(" = %p", cell);
196         return cell;
197 
198 error:
199         up_write(&afs_cells_sem);
200         key_put(cell->anonymous_key);
201         kfree(cell);
202         _leave(" = %d", ret);
203         return ERR_PTR(ret);
204 
205 duplicate_name:
206         if (retref && !IS_ERR(cell))
207                 afs_get_cell(cell);
208 
209         read_unlock(&afs_cells_lock);
210         up_write(&afs_cells_sem);
211 
212         if (retref) {
213                 _leave(" = %p", cell);
214                 return cell;
215         }
216 
217         _leave(" = -EEXIST");
218         return ERR_PTR(-EEXIST);
219 }
220 
221 /*
222  * set the root cell information
223  * - can be called with a module parameter string
224  * - can be called from a write to /proc/fs/afs/rootcell
225  */
226 int afs_cell_init(char *rootcell)
227 {
228         struct afs_cell *old_root, *new_root;
229         char *cp;
230 
231         _enter("");
232 
233         if (!rootcell) {
234                 /* module is loaded with no parameters, or built statically.
235                  * - in the future we might initialize cell DB here.
236                  */
237                 _leave(" = 0 [no root]");
238                 return 0;
239         }
240 
241         cp = strchr(rootcell, ':');
242         if (!cp)
243                 _debug("kAFS: no VL server IP addresses specified");
244         else
245                 *cp++ = 0;
246 
247         /* allocate a cell record for the root cell */
248         new_root = afs_cell_create(rootcell, strlen(rootcell), cp, false);
249         if (IS_ERR(new_root)) {
250                 _leave(" = %ld", PTR_ERR(new_root));
251                 return PTR_ERR(new_root);
252         }
253 
254         /* install the new cell */
255         write_lock(&afs_cells_lock);
256         old_root = afs_cell_root;
257         afs_cell_root = new_root;
258         write_unlock(&afs_cells_lock);
259         afs_put_cell(old_root);
260 
261         _leave(" = 0");
262         return 0;
263 }
264 
265 /*
266  * lookup a cell record
267  */
268 struct afs_cell *afs_cell_lookup(const char *name, unsigned namesz,
269                                  bool dns_cell)
270 {
271         struct afs_cell *cell;
272 
273         _enter("\"%*.*s\",", namesz, namesz, name ?: "");
274 
275         down_read(&afs_cells_sem);
276         read_lock(&afs_cells_lock);
277 
278         if (name) {
279                 /* if the cell was named, look for it in the cell record list */
280                 list_for_each_entry(cell, &afs_cells, link) {
281                         if (strncmp(cell->name, name, namesz) == 0) {
282                                 afs_get_cell(cell);
283                                 goto found;
284                         }
285                 }
286                 cell = ERR_PTR(-ENOENT);
287                 if (dns_cell)
288                         goto create_cell;
289         found:
290                 ;
291         } else {
292                 cell = afs_cell_root;
293                 if (!cell) {
294                         /* this should not happen unless user tries to mount
295                          * when root cell is not set. Return an impossibly
296                          * bizarre errno to alert the user. Things like
297                          * ENOENT might be "more appropriate" but they happen
298                          * for other reasons.
299                          */
300                         cell = ERR_PTR(-EDESTADDRREQ);
301                 } else {
302                         afs_get_cell(cell);
303                 }
304 
305         }
306 
307         read_unlock(&afs_cells_lock);
308         up_read(&afs_cells_sem);
309         _leave(" = %p", cell);
310         return cell;
311 
312 create_cell:
313         read_unlock(&afs_cells_lock);
314         up_read(&afs_cells_sem);
315 
316         cell = afs_cell_create(name, namesz, NULL, true);
317 
318         _leave(" = %p", cell);
319         return cell;
320 }
321 
322 #if 0
323 /*
324  * try and get a cell record
325  */
326 struct afs_cell *afs_get_cell_maybe(struct afs_cell *cell)
327 {
328         write_lock(&afs_cells_lock);
329 
330         if (cell && !list_empty(&cell->link))
331                 afs_get_cell(cell);
332         else
333                 cell = NULL;
334 
335         write_unlock(&afs_cells_lock);
336         return cell;
337 }
338 #endif  /*  0  */
339 
340 /*
341  * destroy a cell record
342  */
343 void afs_put_cell(struct afs_cell *cell)
344 {
345         if (!cell)
346                 return;
347 
348         _enter("%p{%d,%s}", cell, atomic_read(&cell->usage), cell->name);
349 
350         ASSERTCMP(atomic_read(&cell->usage), >, 0);
351 
352         /* to prevent a race, the decrement and the dequeue must be effectively
353          * atomic */
354         write_lock(&afs_cells_lock);
355 
356         if (likely(!atomic_dec_and_test(&cell->usage))) {
357                 write_unlock(&afs_cells_lock);
358                 _leave("");
359                 return;
360         }
361 
362         ASSERT(list_empty(&cell->servers));
363         ASSERT(list_empty(&cell->vl_list));
364 
365         write_unlock(&afs_cells_lock);
366 
367         wake_up(&afs_cells_freeable_wq);
368 
369         _leave(" [unused]");
370 }
371 
372 /*
373  * destroy a cell record
374  * - must be called with the afs_cells_sem write-locked
375  * - cell->link should have been broken by the caller
376  */
377 static void afs_cell_destroy(struct afs_cell *cell)
378 {
379         _enter("%p{%d,%s}", cell, atomic_read(&cell->usage), cell->name);
380 
381         ASSERTCMP(atomic_read(&cell->usage), >=, 0);
382         ASSERT(list_empty(&cell->link));
383 
384         /* wait for everyone to stop using the cell */
385         if (atomic_read(&cell->usage) > 0) {
386                 DECLARE_WAITQUEUE(myself, current);
387 
388                 _debug("wait for cell %s", cell->name);
389                 set_current_state(TASK_UNINTERRUPTIBLE);
390                 add_wait_queue(&afs_cells_freeable_wq, &myself);
391 
392                 while (atomic_read(&cell->usage) > 0) {
393                         schedule();
394                         set_current_state(TASK_UNINTERRUPTIBLE);
395                 }
396 
397                 remove_wait_queue(&afs_cells_freeable_wq, &myself);
398                 set_current_state(TASK_RUNNING);
399         }
400 
401         _debug("cell dead");
402         ASSERTCMP(atomic_read(&cell->usage), ==, 0);
403         ASSERT(list_empty(&cell->servers));
404         ASSERT(list_empty(&cell->vl_list));
405 
406         afs_proc_cell_remove(cell);
407 
408         down_write(&afs_proc_cells_sem);
409         list_del_init(&cell->proc_link);
410         up_write(&afs_proc_cells_sem);
411 
412 #ifdef CONFIG_AFS_FSCACHE
413         fscache_relinquish_cookie(cell->cache, 0);
414 #endif
415         key_put(cell->anonymous_key);
416         kfree(cell);
417 
418         _leave(" [destroyed]");
419 }
420 
421 /*
422  * purge in-memory cell database on module unload or afs_init() failure
423  * - the timeout daemon is stopped before calling this
424  */
425 void afs_cell_purge(void)
426 {
427         struct afs_cell *cell;
428 
429         _enter("");
430 
431         afs_put_cell(afs_cell_root);
432 
433         down_write(&afs_cells_sem);
434 
435         while (!list_empty(&afs_cells)) {
436                 cell = NULL;
437 
438                 /* remove the next cell from the front of the list */
439                 write_lock(&afs_cells_lock);
440 
441                 if (!list_empty(&afs_cells)) {
442                         cell = list_entry(afs_cells.next,
443                                           struct afs_cell, link);
444                         list_del_init(&cell->link);
445                 }
446 
447                 write_unlock(&afs_cells_lock);
448 
449                 if (cell) {
450                         _debug("PURGING CELL %s (%d)",
451                                cell->name, atomic_read(&cell->usage));
452 
453                         /* now the cell should be left with no references */
454                         afs_cell_destroy(cell);
455                 }
456         }
457 
458         up_write(&afs_cells_sem);
459         _leave("");
460 }
461 

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