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TOMOYO Linux Cross Reference
Linux/fs/afs/callback.c

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  1 /*
  2  * Copyright (c) 2002, 2007 Red Hat, Inc. All rights reserved.
  3  *
  4  * This software may be freely redistributed under the terms of the
  5  * GNU General Public License.
  6  *
  7  * You should have received a copy of the GNU General Public License
  8  * along with this program; if not, write to the Free Software
  9  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 10  *
 11  * Authors: David Woodhouse <dwmw2@infradead.org>
 12  *          David Howells <dhowells@redhat.com>
 13  *
 14  */
 15 
 16 #include <linux/kernel.h>
 17 #include <linux/module.h>
 18 #include <linux/init.h>
 19 #include <linux/circ_buf.h>
 20 #include <linux/sched.h>
 21 #include "internal.h"
 22 
 23 #if 0
 24 unsigned afs_vnode_update_timeout = 10;
 25 #endif  /*  0  */
 26 
 27 #define afs_breakring_space(server) \
 28         CIRC_SPACE((server)->cb_break_head, (server)->cb_break_tail,    \
 29                    ARRAY_SIZE((server)->cb_break))
 30 
 31 //static void afs_callback_updater(struct work_struct *);
 32 
 33 static struct workqueue_struct *afs_callback_update_worker;
 34 
 35 /*
 36  * allow the fileserver to request callback state (re-)initialisation
 37  */
 38 void afs_init_callback_state(struct afs_server *server)
 39 {
 40         struct afs_vnode *vnode;
 41 
 42         _enter("{%p}", server);
 43 
 44         spin_lock(&server->cb_lock);
 45 
 46         /* kill all the promises on record from this server */
 47         while (!RB_EMPTY_ROOT(&server->cb_promises)) {
 48                 vnode = rb_entry(server->cb_promises.rb_node,
 49                                  struct afs_vnode, cb_promise);
 50                 _debug("UNPROMISE { vid=%x:%u uq=%u}",
 51                        vnode->fid.vid, vnode->fid.vnode, vnode->fid.unique);
 52                 rb_erase(&vnode->cb_promise, &server->cb_promises);
 53                 vnode->cb_promised = false;
 54         }
 55 
 56         spin_unlock(&server->cb_lock);
 57         _leave("");
 58 }
 59 
 60 /*
 61  * handle the data invalidation side of a callback being broken
 62  */
 63 void afs_broken_callback_work(struct work_struct *work)
 64 {
 65         struct afs_vnode *vnode =
 66                 container_of(work, struct afs_vnode, cb_broken_work);
 67 
 68         _enter("");
 69 
 70         if (test_bit(AFS_VNODE_DELETED, &vnode->flags))
 71                 return;
 72 
 73         /* we're only interested in dealing with a broken callback on *this*
 74          * vnode and only if no-one else has dealt with it yet */
 75         if (!mutex_trylock(&vnode->validate_lock))
 76                 return; /* someone else is dealing with it */
 77 
 78         if (test_bit(AFS_VNODE_CB_BROKEN, &vnode->flags)) {
 79                 if (S_ISDIR(vnode->vfs_inode.i_mode))
 80                         afs_clear_permits(vnode);
 81 
 82                 if (afs_vnode_fetch_status(vnode, NULL, NULL) < 0)
 83                         goto out;
 84 
 85                 if (test_bit(AFS_VNODE_DELETED, &vnode->flags))
 86                         goto out;
 87 
 88                 /* if the vnode's data version number changed then its contents
 89                  * are different */
 90                 if (test_and_clear_bit(AFS_VNODE_ZAP_DATA, &vnode->flags))
 91                         afs_zap_data(vnode);
 92         }
 93 
 94 out:
 95         mutex_unlock(&vnode->validate_lock);
 96 
 97         /* avoid the potential race whereby the mutex_trylock() in this
 98          * function happens again between the clear_bit() and the
 99          * mutex_unlock() */
100         if (test_bit(AFS_VNODE_CB_BROKEN, &vnode->flags)) {
101                 _debug("requeue");
102                 queue_work(afs_callback_update_worker, &vnode->cb_broken_work);
103         }
104         _leave("");
105 }
106 
107 /*
108  * actually break a callback
109  */
110 static void afs_break_callback(struct afs_server *server,
111                                struct afs_vnode *vnode)
112 {
113         _enter("");
114 
115         set_bit(AFS_VNODE_CB_BROKEN, &vnode->flags);
116 
117         if (vnode->cb_promised) {
118                 spin_lock(&vnode->lock);
119 
120                 _debug("break callback");
121 
122                 spin_lock(&server->cb_lock);
123                 if (vnode->cb_promised) {
124                         rb_erase(&vnode->cb_promise, &server->cb_promises);
125                         vnode->cb_promised = false;
126                 }
127                 spin_unlock(&server->cb_lock);
128 
129                 queue_work(afs_callback_update_worker, &vnode->cb_broken_work);
130                 if (list_empty(&vnode->granted_locks) &&
131                     !list_empty(&vnode->pending_locks))
132                         afs_lock_may_be_available(vnode);
133                 spin_unlock(&vnode->lock);
134         }
135 }
136 
137 /*
138  * allow the fileserver to explicitly break one callback
139  * - happens when
140  *   - the backing file is changed
141  *   - a lock is released
142  */
143 static void afs_break_one_callback(struct afs_server *server,
144                                    struct afs_fid *fid)
145 {
146         struct afs_vnode *vnode;
147         struct rb_node *p;
148 
149         _debug("find");
150         spin_lock(&server->fs_lock);
151         p = server->fs_vnodes.rb_node;
152         while (p) {
153                 vnode = rb_entry(p, struct afs_vnode, server_rb);
154                 if (fid->vid < vnode->fid.vid)
155                         p = p->rb_left;
156                 else if (fid->vid > vnode->fid.vid)
157                         p = p->rb_right;
158                 else if (fid->vnode < vnode->fid.vnode)
159                         p = p->rb_left;
160                 else if (fid->vnode > vnode->fid.vnode)
161                         p = p->rb_right;
162                 else if (fid->unique < vnode->fid.unique)
163                         p = p->rb_left;
164                 else if (fid->unique > vnode->fid.unique)
165                         p = p->rb_right;
166                 else
167                         goto found;
168         }
169 
170         /* not found so we just ignore it (it may have moved to another
171          * server) */
172 not_available:
173         _debug("not avail");
174         spin_unlock(&server->fs_lock);
175         _leave("");
176         return;
177 
178 found:
179         _debug("found");
180         ASSERTCMP(server, ==, vnode->server);
181 
182         if (!igrab(AFS_VNODE_TO_I(vnode)))
183                 goto not_available;
184         spin_unlock(&server->fs_lock);
185 
186         afs_break_callback(server, vnode);
187         iput(&vnode->vfs_inode);
188         _leave("");
189 }
190 
191 /*
192  * allow the fileserver to break callback promises
193  */
194 void afs_break_callbacks(struct afs_server *server, size_t count,
195                          struct afs_callback callbacks[])
196 {
197         _enter("%p,%zu,", server, count);
198 
199         ASSERT(server != NULL);
200         ASSERTCMP(count, <=, AFSCBMAX);
201 
202         for (; count > 0; callbacks++, count--) {
203                 _debug("- Fid { vl=%08x n=%u u=%u }  CB { v=%u x=%u t=%u }",
204                        callbacks->fid.vid,
205                        callbacks->fid.vnode,
206                        callbacks->fid.unique,
207                        callbacks->version,
208                        callbacks->expiry,
209                        callbacks->type
210                        );
211                 afs_break_one_callback(server, &callbacks->fid);
212         }
213 
214         _leave("");
215         return;
216 }
217 
218 /*
219  * record the callback for breaking
220  * - the caller must hold server->cb_lock
221  */
222 static void afs_do_give_up_callback(struct afs_server *server,
223                                     struct afs_vnode *vnode)
224 {
225         struct afs_callback *cb;
226 
227         _enter("%p,%p", server, vnode);
228 
229         cb = &server->cb_break[server->cb_break_head];
230         cb->fid         = vnode->fid;
231         cb->version     = vnode->cb_version;
232         cb->expiry      = vnode->cb_expiry;
233         cb->type        = vnode->cb_type;
234         smp_wmb();
235         server->cb_break_head =
236                 (server->cb_break_head + 1) &
237                 (ARRAY_SIZE(server->cb_break) - 1);
238 
239         /* defer the breaking of callbacks to try and collect as many as
240          * possible to ship in one operation */
241         switch (atomic_inc_return(&server->cb_break_n)) {
242         case 1 ... AFSCBMAX - 1:
243                 queue_delayed_work(afs_callback_update_worker,
244                                    &server->cb_break_work, HZ * 2);
245                 break;
246         case AFSCBMAX:
247                 afs_flush_callback_breaks(server);
248                 break;
249         default:
250                 break;
251         }
252 
253         ASSERT(server->cb_promises.rb_node != NULL);
254         rb_erase(&vnode->cb_promise, &server->cb_promises);
255         vnode->cb_promised = false;
256         _leave("");
257 }
258 
259 /*
260  * discard the callback on a deleted item
261  */
262 void afs_discard_callback_on_delete(struct afs_vnode *vnode)
263 {
264         struct afs_server *server = vnode->server;
265 
266         _enter("%d", vnode->cb_promised);
267 
268         if (!vnode->cb_promised) {
269                 _leave(" [not promised]");
270                 return;
271         }
272 
273         ASSERT(server != NULL);
274 
275         spin_lock(&server->cb_lock);
276         if (vnode->cb_promised) {
277                 ASSERT(server->cb_promises.rb_node != NULL);
278                 rb_erase(&vnode->cb_promise, &server->cb_promises);
279                 vnode->cb_promised = false;
280         }
281         spin_unlock(&server->cb_lock);
282         _leave("");
283 }
284 
285 /*
286  * give up the callback registered for a vnode on the file server when the
287  * inode is being cleared
288  */
289 void afs_give_up_callback(struct afs_vnode *vnode)
290 {
291         struct afs_server *server = vnode->server;
292 
293         DECLARE_WAITQUEUE(myself, current);
294 
295         _enter("%d", vnode->cb_promised);
296 
297         _debug("GIVE UP INODE %p", &vnode->vfs_inode);
298 
299         if (!vnode->cb_promised) {
300                 _leave(" [not promised]");
301                 return;
302         }
303 
304         ASSERT(server != NULL);
305 
306         spin_lock(&server->cb_lock);
307         if (vnode->cb_promised && afs_breakring_space(server) == 0) {
308                 add_wait_queue(&server->cb_break_waitq, &myself);
309                 for (;;) {
310                         set_current_state(TASK_UNINTERRUPTIBLE);
311                         if (!vnode->cb_promised ||
312                             afs_breakring_space(server) != 0)
313                                 break;
314                         spin_unlock(&server->cb_lock);
315                         schedule();
316                         spin_lock(&server->cb_lock);
317                 }
318                 remove_wait_queue(&server->cb_break_waitq, &myself);
319                 __set_current_state(TASK_RUNNING);
320         }
321 
322         /* of course, it's always possible for the server to break this vnode's
323          * callback first... */
324         if (vnode->cb_promised)
325                 afs_do_give_up_callback(server, vnode);
326 
327         spin_unlock(&server->cb_lock);
328         _leave("");
329 }
330 
331 /*
332  * dispatch a deferred give up callbacks operation
333  */
334 void afs_dispatch_give_up_callbacks(struct work_struct *work)
335 {
336         struct afs_server *server =
337                 container_of(work, struct afs_server, cb_break_work.work);
338 
339         _enter("");
340 
341         /* tell the fileserver to discard the callback promises it has
342          * - in the event of ENOMEM or some other error, we just forget that we
343          *   had callbacks entirely, and the server will call us later to break
344          *   them
345          */
346         afs_fs_give_up_callbacks(server, &afs_async_call);
347 }
348 
349 /*
350  * flush the outstanding callback breaks on a server
351  */
352 void afs_flush_callback_breaks(struct afs_server *server)
353 {
354         mod_delayed_work(afs_callback_update_worker, &server->cb_break_work, 0);
355 }
356 
357 #if 0
358 /*
359  * update a bunch of callbacks
360  */
361 static void afs_callback_updater(struct work_struct *work)
362 {
363         struct afs_server *server;
364         struct afs_vnode *vnode, *xvnode;
365         time_t now;
366         long timeout;
367         int ret;
368 
369         server = container_of(work, struct afs_server, updater);
370 
371         _enter("");
372 
373         now = get_seconds();
374 
375         /* find the first vnode to update */
376         spin_lock(&server->cb_lock);
377         for (;;) {
378                 if (RB_EMPTY_ROOT(&server->cb_promises)) {
379                         spin_unlock(&server->cb_lock);
380                         _leave(" [nothing]");
381                         return;
382                 }
383 
384                 vnode = rb_entry(rb_first(&server->cb_promises),
385                                  struct afs_vnode, cb_promise);
386                 if (atomic_read(&vnode->usage) > 0)
387                         break;
388                 rb_erase(&vnode->cb_promise, &server->cb_promises);
389                 vnode->cb_promised = false;
390         }
391 
392         timeout = vnode->update_at - now;
393         if (timeout > 0) {
394                 queue_delayed_work(afs_vnode_update_worker,
395                                    &afs_vnode_update, timeout * HZ);
396                 spin_unlock(&server->cb_lock);
397                 _leave(" [nothing]");
398                 return;
399         }
400 
401         list_del_init(&vnode->update);
402         atomic_inc(&vnode->usage);
403         spin_unlock(&server->cb_lock);
404 
405         /* we can now perform the update */
406         _debug("update %s", vnode->vldb.name);
407         vnode->state = AFS_VL_UPDATING;
408         vnode->upd_rej_cnt = 0;
409         vnode->upd_busy_cnt = 0;
410 
411         ret = afs_vnode_update_record(vl, &vldb);
412         switch (ret) {
413         case 0:
414                 afs_vnode_apply_update(vl, &vldb);
415                 vnode->state = AFS_VL_UPDATING;
416                 break;
417         case -ENOMEDIUM:
418                 vnode->state = AFS_VL_VOLUME_DELETED;
419                 break;
420         default:
421                 vnode->state = AFS_VL_UNCERTAIN;
422                 break;
423         }
424 
425         /* and then reschedule */
426         _debug("reschedule");
427         vnode->update_at = get_seconds() + afs_vnode_update_timeout;
428 
429         spin_lock(&server->cb_lock);
430 
431         if (!list_empty(&server->cb_promises)) {
432                 /* next update in 10 minutes, but wait at least 1 second more
433                  * than the newest record already queued so that we don't spam
434                  * the VL server suddenly with lots of requests
435                  */
436                 xvnode = list_entry(server->cb_promises.prev,
437                                     struct afs_vnode, update);
438                 if (vnode->update_at <= xvnode->update_at)
439                         vnode->update_at = xvnode->update_at + 1;
440                 xvnode = list_entry(server->cb_promises.next,
441                                     struct afs_vnode, update);
442                 timeout = xvnode->update_at - now;
443                 if (timeout < 0)
444                         timeout = 0;
445         } else {
446                 timeout = afs_vnode_update_timeout;
447         }
448 
449         list_add_tail(&vnode->update, &server->cb_promises);
450 
451         _debug("timeout %ld", timeout);
452         queue_delayed_work(afs_vnode_update_worker,
453                            &afs_vnode_update, timeout * HZ);
454         spin_unlock(&server->cb_lock);
455         afs_put_vnode(vl);
456 }
457 #endif
458 
459 /*
460  * initialise the callback update process
461  */
462 int __init afs_callback_update_init(void)
463 {
464         afs_callback_update_worker =
465                 create_singlethread_workqueue("kafs_callbackd");
466         return afs_callback_update_worker ? 0 : -ENOMEM;
467 }
468 
469 /*
470  * shut down the callback update process
471  */
472 void afs_callback_update_kill(void)
473 {
474         destroy_workqueue(afs_callback_update_worker);
475 }
476 

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