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object.c
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1 /* FS-Cache object state machine handler
2  *
3  * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
4  * Written by David Howells ([email protected])
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  * See Documentation/filesystems/caching/object.txt for a description of the
12  * object state machine and the in-kernel representations.
13  */
14 
15 #define FSCACHE_DEBUG_LEVEL COOKIE
16 #include <linux/module.h>
17 #include "internal.h"
18 
19 const char *fscache_object_states[FSCACHE_OBJECT__NSTATES] = {
20  [FSCACHE_OBJECT_INIT] = "OBJECT_INIT",
21  [FSCACHE_OBJECT_LOOKING_UP] = "OBJECT_LOOKING_UP",
22  [FSCACHE_OBJECT_CREATING] = "OBJECT_CREATING",
23  [FSCACHE_OBJECT_AVAILABLE] = "OBJECT_AVAILABLE",
24  [FSCACHE_OBJECT_ACTIVE] = "OBJECT_ACTIVE",
25  [FSCACHE_OBJECT_UPDATING] = "OBJECT_UPDATING",
26  [FSCACHE_OBJECT_DYING] = "OBJECT_DYING",
27  [FSCACHE_OBJECT_LC_DYING] = "OBJECT_LC_DYING",
28  [FSCACHE_OBJECT_ABORT_INIT] = "OBJECT_ABORT_INIT",
29  [FSCACHE_OBJECT_RELEASING] = "OBJECT_RELEASING",
30  [FSCACHE_OBJECT_RECYCLING] = "OBJECT_RECYCLING",
31  [FSCACHE_OBJECT_WITHDRAWING] = "OBJECT_WITHDRAWING",
32  [FSCACHE_OBJECT_DEAD] = "OBJECT_DEAD",
33 };
34 EXPORT_SYMBOL(fscache_object_states);
35 
36 const char fscache_object_states_short[FSCACHE_OBJECT__NSTATES][5] = {
37  [FSCACHE_OBJECT_INIT] = "INIT",
38  [FSCACHE_OBJECT_LOOKING_UP] = "LOOK",
39  [FSCACHE_OBJECT_CREATING] = "CRTN",
40  [FSCACHE_OBJECT_AVAILABLE] = "AVBL",
41  [FSCACHE_OBJECT_ACTIVE] = "ACTV",
42  [FSCACHE_OBJECT_UPDATING] = "UPDT",
43  [FSCACHE_OBJECT_DYING] = "DYNG",
44  [FSCACHE_OBJECT_LC_DYING] = "LCDY",
45  [FSCACHE_OBJECT_ABORT_INIT] = "ABTI",
46  [FSCACHE_OBJECT_RELEASING] = "RELS",
47  [FSCACHE_OBJECT_RECYCLING] = "RCYC",
48  [FSCACHE_OBJECT_WITHDRAWING] = "WTHD",
49  [FSCACHE_OBJECT_DEAD] = "DEAD",
50 };
51 
52 static int fscache_get_object(struct fscache_object *);
53 static void fscache_put_object(struct fscache_object *);
54 static void fscache_initialise_object(struct fscache_object *);
55 static void fscache_lookup_object(struct fscache_object *);
56 static void fscache_object_available(struct fscache_object *);
57 static void fscache_release_object(struct fscache_object *);
58 static void fscache_withdraw_object(struct fscache_object *);
59 static void fscache_enqueue_dependents(struct fscache_object *);
60 static void fscache_dequeue_object(struct fscache_object *);
61 
62 /*
63  * we need to notify the parent when an op completes that we had outstanding
64  * upon it
65  */
66 static inline void fscache_done_parent_op(struct fscache_object *object)
67 {
68  struct fscache_object *parent = object->parent;
69 
70  _enter("OBJ%x {OBJ%x,%x}",
71  object->debug_id, parent->debug_id, parent->n_ops);
72 
73  spin_lock_nested(&parent->lock, 1);
74  parent->n_ops--;
75  parent->n_obj_ops--;
76  if (parent->n_ops == 0)
77  fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
78  spin_unlock(&parent->lock);
79 }
80 
81 /*
82  * process events that have been sent to an object's state machine
83  * - initiates parent lookup
84  * - does object lookup
85  * - does object creation
86  * - does object recycling and retirement
87  * - does object withdrawal
88  */
89 static void fscache_object_state_machine(struct fscache_object *object)
90 {
91  enum fscache_object_state new_state;
92  struct fscache_cookie *cookie;
93 
94  ASSERT(object != NULL);
95 
96  _enter("{OBJ%x,%s,%lx}",
97  object->debug_id, fscache_object_states[object->state],
98  object->events);
99 
100  switch (object->state) {
101  /* wait for the parent object to become ready */
102  case FSCACHE_OBJECT_INIT:
103  object->event_mask =
104  ULONG_MAX & ~(1 << FSCACHE_OBJECT_EV_CLEARED);
105  fscache_initialise_object(object);
106  goto done;
107 
108  /* look up the object metadata on disk */
109  case FSCACHE_OBJECT_LOOKING_UP:
110  fscache_lookup_object(object);
111  goto lookup_transit;
112 
113  /* create the object metadata on disk */
114  case FSCACHE_OBJECT_CREATING:
115  fscache_lookup_object(object);
116  goto lookup_transit;
117 
118  /* handle an object becoming available; start pending
119  * operations and queue dependent operations for processing */
120  case FSCACHE_OBJECT_AVAILABLE:
121  fscache_object_available(object);
122  goto active_transit;
123 
124  /* normal running state */
125  case FSCACHE_OBJECT_ACTIVE:
126  goto active_transit;
127 
128  /* update the object metadata on disk */
129  case FSCACHE_OBJECT_UPDATING:
130  clear_bit(FSCACHE_OBJECT_EV_UPDATE, &object->events);
131  fscache_stat(&fscache_n_updates_run);
132  fscache_stat(&fscache_n_cop_update_object);
133  object->cache->ops->update_object(object);
134  fscache_stat_d(&fscache_n_cop_update_object);
135  goto active_transit;
136 
137  /* handle an object dying during lookup or creation */
138  case FSCACHE_OBJECT_LC_DYING:
139  object->event_mask &= ~(1 << FSCACHE_OBJECT_EV_UPDATE);
140  fscache_stat(&fscache_n_cop_lookup_complete);
141  object->cache->ops->lookup_complete(object);
142  fscache_stat_d(&fscache_n_cop_lookup_complete);
143 
144  spin_lock(&object->lock);
145  object->state = FSCACHE_OBJECT_DYING;
146  cookie = object->cookie;
147  if (cookie) {
148  if (test_and_clear_bit(FSCACHE_COOKIE_LOOKING_UP,
149  &cookie->flags))
150  wake_up_bit(&cookie->flags,
151  FSCACHE_COOKIE_LOOKING_UP);
152  if (test_and_clear_bit(FSCACHE_COOKIE_CREATING,
153  &cookie->flags))
154  wake_up_bit(&cookie->flags,
155  FSCACHE_COOKIE_CREATING);
156  }
157  spin_unlock(&object->lock);
158 
159  fscache_done_parent_op(object);
160 
161  /* wait for completion of all active operations on this object
162  * and the death of all child objects of this object */
163  case FSCACHE_OBJECT_DYING:
164  dying:
165  clear_bit(FSCACHE_OBJECT_EV_CLEARED, &object->events);
166  spin_lock(&object->lock);
167  _debug("dying OBJ%x {%d,%d}",
168  object->debug_id, object->n_ops, object->n_children);
169  if (object->n_ops == 0 && object->n_children == 0) {
170  object->event_mask &=
171  ~(1 << FSCACHE_OBJECT_EV_CLEARED);
172  object->event_mask |=
173  (1 << FSCACHE_OBJECT_EV_WITHDRAW) |
174  (1 << FSCACHE_OBJECT_EV_RETIRE) |
175  (1 << FSCACHE_OBJECT_EV_RELEASE) |
176  (1 << FSCACHE_OBJECT_EV_ERROR);
177  } else {
178  object->event_mask &=
179  ~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
180  (1 << FSCACHE_OBJECT_EV_RETIRE) |
181  (1 << FSCACHE_OBJECT_EV_RELEASE) |
182  (1 << FSCACHE_OBJECT_EV_ERROR));
183  object->event_mask |=
184  1 << FSCACHE_OBJECT_EV_CLEARED;
185  }
186  spin_unlock(&object->lock);
187  fscache_enqueue_dependents(object);
188  fscache_start_operations(object);
189  goto terminal_transit;
190 
191  /* handle an abort during initialisation */
192  case FSCACHE_OBJECT_ABORT_INIT:
193  _debug("handle abort init %lx", object->events);
194  object->event_mask &= ~(1 << FSCACHE_OBJECT_EV_UPDATE);
195 
196  spin_lock(&object->lock);
197  fscache_dequeue_object(object);
198 
199  object->state = FSCACHE_OBJECT_DYING;
200  if (test_and_clear_bit(FSCACHE_COOKIE_CREATING,
201  &object->cookie->flags))
202  wake_up_bit(&object->cookie->flags,
203  FSCACHE_COOKIE_CREATING);
204  spin_unlock(&object->lock);
205  goto dying;
206 
207  /* handle the netfs releasing an object and possibly marking it
208  * obsolete too */
209  case FSCACHE_OBJECT_RELEASING:
210  case FSCACHE_OBJECT_RECYCLING:
211  object->event_mask &=
212  ~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
213  (1 << FSCACHE_OBJECT_EV_RETIRE) |
214  (1 << FSCACHE_OBJECT_EV_RELEASE) |
215  (1 << FSCACHE_OBJECT_EV_ERROR));
216  fscache_release_object(object);
217  spin_lock(&object->lock);
218  object->state = FSCACHE_OBJECT_DEAD;
219  spin_unlock(&object->lock);
220  fscache_stat(&fscache_n_object_dead);
221  goto terminal_transit;
222 
223  /* handle the parent cache of this object being withdrawn from
224  * active service */
225  case FSCACHE_OBJECT_WITHDRAWING:
226  object->event_mask &=
227  ~((1 << FSCACHE_OBJECT_EV_WITHDRAW) |
228  (1 << FSCACHE_OBJECT_EV_RETIRE) |
229  (1 << FSCACHE_OBJECT_EV_RELEASE) |
230  (1 << FSCACHE_OBJECT_EV_ERROR));
231  fscache_withdraw_object(object);
232  spin_lock(&object->lock);
233  object->state = FSCACHE_OBJECT_DEAD;
234  spin_unlock(&object->lock);
235  fscache_stat(&fscache_n_object_dead);
236  goto terminal_transit;
237 
238  /* complain about the object being woken up once it is
239  * deceased */
240  case FSCACHE_OBJECT_DEAD:
241  printk(KERN_ERR "FS-Cache:"
242  " Unexpected event in dead state %lx\n",
243  object->events & object->event_mask);
244  BUG();
245 
246  default:
247  printk(KERN_ERR "FS-Cache: Unknown object state %u\n",
248  object->state);
249  BUG();
250  }
251 
252  /* determine the transition from a lookup state */
253 lookup_transit:
254  switch (fls(object->events & object->event_mask) - 1) {
255  case FSCACHE_OBJECT_EV_WITHDRAW:
256  case FSCACHE_OBJECT_EV_RETIRE:
257  case FSCACHE_OBJECT_EV_RELEASE:
258  case FSCACHE_OBJECT_EV_ERROR:
259  new_state = FSCACHE_OBJECT_LC_DYING;
260  goto change_state;
261  case FSCACHE_OBJECT_EV_REQUEUE:
262  goto done;
263  case -1:
264  goto done; /* sleep until event */
265  default:
266  goto unsupported_event;
267  }
268 
269  /* determine the transition from an active state */
270 active_transit:
271  switch (fls(object->events & object->event_mask) - 1) {
272  case FSCACHE_OBJECT_EV_WITHDRAW:
273  case FSCACHE_OBJECT_EV_RETIRE:
274  case FSCACHE_OBJECT_EV_RELEASE:
275  case FSCACHE_OBJECT_EV_ERROR:
276  new_state = FSCACHE_OBJECT_DYING;
277  goto change_state;
278  case FSCACHE_OBJECT_EV_UPDATE:
279  new_state = FSCACHE_OBJECT_UPDATING;
280  goto change_state;
281  case -1:
282  new_state = FSCACHE_OBJECT_ACTIVE;
283  goto change_state; /* sleep until event */
284  default:
285  goto unsupported_event;
286  }
287 
288  /* determine the transition from a terminal state */
289 terminal_transit:
290  switch (fls(object->events & object->event_mask) - 1) {
291  case FSCACHE_OBJECT_EV_WITHDRAW:
292  new_state = FSCACHE_OBJECT_WITHDRAWING;
293  goto change_state;
294  case FSCACHE_OBJECT_EV_RETIRE:
295  new_state = FSCACHE_OBJECT_RECYCLING;
296  goto change_state;
297  case FSCACHE_OBJECT_EV_RELEASE:
298  new_state = FSCACHE_OBJECT_RELEASING;
299  goto change_state;
300  case FSCACHE_OBJECT_EV_ERROR:
301  new_state = FSCACHE_OBJECT_WITHDRAWING;
302  goto change_state;
303  case FSCACHE_OBJECT_EV_CLEARED:
304  new_state = FSCACHE_OBJECT_DYING;
305  goto change_state;
306  case -1:
307  goto done; /* sleep until event */
308  default:
309  goto unsupported_event;
310  }
311 
312 change_state:
313  spin_lock(&object->lock);
314  object->state = new_state;
315  spin_unlock(&object->lock);
316 
317 done:
318  _leave(" [->%s]", fscache_object_states[object->state]);
319  return;
320 
321 unsupported_event:
322  printk(KERN_ERR "FS-Cache:"
323  " Unsupported event %lx [mask %lx] in state %s\n",
324  object->events, object->event_mask,
325  fscache_object_states[object->state]);
326  BUG();
327 }
328 
329 /*
330  * execute an object
331  */
332 void fscache_object_work_func(struct work_struct *work)
333 {
334  struct fscache_object *object =
335  container_of(work, struct fscache_object, work);
336  unsigned long start;
337 
338  _enter("{OBJ%x}", object->debug_id);
339 
340  start = jiffies;
341  fscache_object_state_machine(object);
342  fscache_hist(fscache_objs_histogram, start);
343  if (object->events & object->event_mask)
344  fscache_enqueue_object(object);
345  clear_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
346  fscache_put_object(object);
347 }
348 EXPORT_SYMBOL(fscache_object_work_func);
349 
350 /*
351  * initialise an object
352  * - check the specified object's parent to see if we can make use of it
353  * immediately to do a creation
354  * - we may need to start the process of creating a parent and we need to wait
355  * for the parent's lookup and creation to complete if it's not there yet
356  * - an object's cookie is pinned until we clear FSCACHE_COOKIE_CREATING on the
357  * leaf-most cookies of the object and all its children
358  */
359 static void fscache_initialise_object(struct fscache_object *object)
360 {
361  struct fscache_object *parent;
362 
363  _enter("");
364  ASSERT(object->cookie != NULL);
365  ASSERT(object->cookie->parent != NULL);
366 
367  if (object->events & ((1 << FSCACHE_OBJECT_EV_ERROR) |
368  (1 << FSCACHE_OBJECT_EV_RELEASE) |
369  (1 << FSCACHE_OBJECT_EV_RETIRE) |
370  (1 << FSCACHE_OBJECT_EV_WITHDRAW))) {
371  _debug("abort init %lx", object->events);
372  spin_lock(&object->lock);
373  object->state = FSCACHE_OBJECT_ABORT_INIT;
374  spin_unlock(&object->lock);
375  return;
376  }
377 
378  spin_lock(&object->cookie->lock);
379  spin_lock_nested(&object->cookie->parent->lock, 1);
380 
381  parent = object->parent;
382  if (!parent) {
383  _debug("no parent");
384  set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
385  } else {
386  spin_lock(&object->lock);
387  spin_lock_nested(&parent->lock, 1);
388  _debug("parent %s", fscache_object_states[parent->state]);
389 
390  if (parent->state >= FSCACHE_OBJECT_DYING) {
391  _debug("bad parent");
392  set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
393  } else if (parent->state < FSCACHE_OBJECT_AVAILABLE) {
394  _debug("wait");
395 
396  /* we may get woken up in this state by child objects
397  * binding on to us, so we need to make sure we don't
398  * add ourself to the list multiple times */
399  if (list_empty(&object->dep_link)) {
400  fscache_stat(&fscache_n_cop_grab_object);
401  object->cache->ops->grab_object(object);
402  fscache_stat_d(&fscache_n_cop_grab_object);
403  list_add(&object->dep_link,
404  &parent->dependents);
405 
406  /* fscache_acquire_non_index_cookie() uses this
407  * to wake the chain up */
408  if (parent->state == FSCACHE_OBJECT_INIT)
409  fscache_enqueue_object(parent);
410  }
411  } else {
412  _debug("go");
413  parent->n_ops++;
414  parent->n_obj_ops++;
415  object->lookup_jif = jiffies;
416  object->state = FSCACHE_OBJECT_LOOKING_UP;
417  set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
418  }
419 
420  spin_unlock(&parent->lock);
421  spin_unlock(&object->lock);
422  }
423 
424  spin_unlock(&object->cookie->parent->lock);
425  spin_unlock(&object->cookie->lock);
426  _leave("");
427 }
428 
429 /*
430  * look an object up in the cache from which it was allocated
431  * - we hold an "access lock" on the parent object, so the parent object cannot
432  * be withdrawn by either party till we've finished
433  * - an object's cookie is pinned until we clear FSCACHE_COOKIE_CREATING on the
434  * leaf-most cookies of the object and all its children
435  */
436 static void fscache_lookup_object(struct fscache_object *object)
437 {
438  struct fscache_cookie *cookie = object->cookie;
439  struct fscache_object *parent;
440  int ret;
441 
442  _enter("");
443 
444  parent = object->parent;
445  ASSERT(parent != NULL);
446  ASSERTCMP(parent->n_ops, >, 0);
447  ASSERTCMP(parent->n_obj_ops, >, 0);
448 
449  /* make sure the parent is still available */
450  ASSERTCMP(parent->state, >=, FSCACHE_OBJECT_AVAILABLE);
451 
452  if (parent->state >= FSCACHE_OBJECT_DYING ||
453  test_bit(FSCACHE_IOERROR, &object->cache->flags)) {
454  _debug("unavailable");
455  set_bit(FSCACHE_OBJECT_EV_WITHDRAW, &object->events);
456  _leave("");
457  return;
458  }
459 
460  _debug("LOOKUP \"%s/%s\" in \"%s\"",
461  parent->cookie->def->name, cookie->def->name,
462  object->cache->tag->name);
463 
464  fscache_stat(&fscache_n_object_lookups);
465  fscache_stat(&fscache_n_cop_lookup_object);
466  ret = object->cache->ops->lookup_object(object);
467  fscache_stat_d(&fscache_n_cop_lookup_object);
468 
469  if (test_bit(FSCACHE_OBJECT_EV_ERROR, &object->events))
470  set_bit(FSCACHE_COOKIE_UNAVAILABLE, &cookie->flags);
471 
472  if (ret == -ETIMEDOUT) {
473  /* probably stuck behind another object, so move this one to
474  * the back of the queue */
475  fscache_stat(&fscache_n_object_lookups_timed_out);
476  set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
477  }
478 
479  _leave("");
480 }
481 
489 void fscache_object_lookup_negative(struct fscache_object *object)
490 {
491  struct fscache_cookie *cookie = object->cookie;
492 
493  _enter("{OBJ%x,%s}",
494  object->debug_id, fscache_object_states[object->state]);
495 
496  spin_lock(&object->lock);
497  if (object->state == FSCACHE_OBJECT_LOOKING_UP) {
498  fscache_stat(&fscache_n_object_lookups_negative);
499 
500  /* transit here to allow write requests to begin stacking up
501  * and read requests to begin returning ENODATA */
502  object->state = FSCACHE_OBJECT_CREATING;
503  spin_unlock(&object->lock);
504 
505  set_bit(FSCACHE_COOKIE_PENDING_FILL, &cookie->flags);
506  set_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
507 
508  _debug("wake up lookup %p", &cookie->flags);
509  smp_mb__before_clear_bit();
510  clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
511  smp_mb__after_clear_bit();
512  wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
513  set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
514  } else {
515  ASSERTCMP(object->state, ==, FSCACHE_OBJECT_CREATING);
516  spin_unlock(&object->lock);
517  }
518 
519  _leave("");
520 }
521 EXPORT_SYMBOL(fscache_object_lookup_negative);
522 
533 void fscache_obtained_object(struct fscache_object *object)
534 {
535  struct fscache_cookie *cookie = object->cookie;
536 
537  _enter("{OBJ%x,%s}",
538  object->debug_id, fscache_object_states[object->state]);
539 
540  /* if we were still looking up, then we must have a positive lookup
541  * result, in which case there may be data available */
542  spin_lock(&object->lock);
543  if (object->state == FSCACHE_OBJECT_LOOKING_UP) {
544  fscache_stat(&fscache_n_object_lookups_positive);
545 
546  clear_bit(FSCACHE_COOKIE_NO_DATA_YET, &cookie->flags);
547 
548  object->state = FSCACHE_OBJECT_AVAILABLE;
549  spin_unlock(&object->lock);
550 
551  smp_mb__before_clear_bit();
552  clear_bit(FSCACHE_COOKIE_LOOKING_UP, &cookie->flags);
553  smp_mb__after_clear_bit();
554  wake_up_bit(&cookie->flags, FSCACHE_COOKIE_LOOKING_UP);
555  set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
556  } else {
557  ASSERTCMP(object->state, ==, FSCACHE_OBJECT_CREATING);
558  fscache_stat(&fscache_n_object_created);
559 
560  object->state = FSCACHE_OBJECT_AVAILABLE;
561  spin_unlock(&object->lock);
562  set_bit(FSCACHE_OBJECT_EV_REQUEUE, &object->events);
563  smp_wmb();
564  }
565 
566  if (test_and_clear_bit(FSCACHE_COOKIE_CREATING, &cookie->flags))
567  wake_up_bit(&cookie->flags, FSCACHE_COOKIE_CREATING);
568 
569  _leave("");
570 }
571 EXPORT_SYMBOL(fscache_obtained_object);
572 
573 /*
574  * handle an object that has just become available
575  */
576 static void fscache_object_available(struct fscache_object *object)
577 {
578  _enter("{OBJ%x}", object->debug_id);
579 
580  spin_lock(&object->lock);
581 
582  if (object->cookie &&
583  test_and_clear_bit(FSCACHE_COOKIE_CREATING, &object->cookie->flags))
584  wake_up_bit(&object->cookie->flags, FSCACHE_COOKIE_CREATING);
585 
586  fscache_done_parent_op(object);
587  if (object->n_in_progress == 0) {
588  if (object->n_ops > 0) {
589  ASSERTCMP(object->n_ops, >=, object->n_obj_ops);
590  ASSERTIF(object->n_ops > object->n_obj_ops,
591  !list_empty(&object->pending_ops));
592  fscache_start_operations(object);
593  } else {
594  ASSERT(list_empty(&object->pending_ops));
595  }
596  }
597  spin_unlock(&object->lock);
598 
599  fscache_stat(&fscache_n_cop_lookup_complete);
600  object->cache->ops->lookup_complete(object);
601  fscache_stat_d(&fscache_n_cop_lookup_complete);
602  fscache_enqueue_dependents(object);
603 
604  fscache_hist(fscache_obj_instantiate_histogram, object->lookup_jif);
605  fscache_stat(&fscache_n_object_avail);
606 
607  _leave("");
608 }
609 
610 /*
611  * drop an object's attachments
612  */
613 static void fscache_drop_object(struct fscache_object *object)
614 {
615  struct fscache_object *parent = object->parent;
616  struct fscache_cache *cache = object->cache;
617 
618  _enter("{OBJ%x,%d}", object->debug_id, object->n_children);
619 
620  ASSERTCMP(object->cookie, ==, NULL);
621  ASSERT(hlist_unhashed(&object->cookie_link));
622 
623  spin_lock(&cache->object_list_lock);
624  list_del_init(&object->cache_link);
625  spin_unlock(&cache->object_list_lock);
626 
627  fscache_stat(&fscache_n_cop_drop_object);
628  cache->ops->drop_object(object);
629  fscache_stat_d(&fscache_n_cop_drop_object);
630 
631  if (parent) {
632  _debug("release parent OBJ%x {%d}",
633  parent->debug_id, parent->n_children);
634 
635  spin_lock(&parent->lock);
636  parent->n_children--;
637  if (parent->n_children == 0)
638  fscache_raise_event(parent, FSCACHE_OBJECT_EV_CLEARED);
639  spin_unlock(&parent->lock);
640  object->parent = NULL;
641  }
642 
643  /* this just shifts the object release to the work processor */
644  fscache_put_object(object);
645 
646  _leave("");
647 }
648 
649 /*
650  * release or recycle an object that the netfs has discarded
651  */
652 static void fscache_release_object(struct fscache_object *object)
653 {
654  _enter("");
655 
656  fscache_drop_object(object);
657 }
658 
659 /*
660  * withdraw an object from active service
661  */
662 static void fscache_withdraw_object(struct fscache_object *object)
663 {
664  struct fscache_cookie *cookie;
665  bool detached;
666 
667  _enter("");
668 
669  spin_lock(&object->lock);
670  cookie = object->cookie;
671  if (cookie) {
672  /* need to get the cookie lock before the object lock, starting
673  * from the object pointer */
674  atomic_inc(&cookie->usage);
675  spin_unlock(&object->lock);
676 
677  detached = false;
678  spin_lock(&cookie->lock);
679  spin_lock(&object->lock);
680 
681  if (object->cookie == cookie) {
682  hlist_del_init(&object->cookie_link);
683  object->cookie = NULL;
684  detached = true;
685  }
686  spin_unlock(&cookie->lock);
687  fscache_cookie_put(cookie);
688  if (detached)
689  fscache_cookie_put(cookie);
690  }
691 
692  spin_unlock(&object->lock);
693 
694  fscache_drop_object(object);
695 }
696 
697 /*
698  * withdraw an object from active service at the behest of the cache
699  * - need break the links to a cached object cookie
700  * - called under two situations:
701  * (1) recycler decides to reclaim an in-use object
702  * (2) a cache is unmounted
703  * - have to take care as the cookie can be being relinquished by the netfs
704  * simultaneously
705  * - the object is pinned by the caller holding a refcount on it
706  */
707 void fscache_withdrawing_object(struct fscache_cache *cache,
708  struct fscache_object *object)
709 {
710  bool enqueue = false;
711 
712  _enter(",OBJ%x", object->debug_id);
713 
714  spin_lock(&object->lock);
715  if (object->state < FSCACHE_OBJECT_WITHDRAWING) {
716  object->state = FSCACHE_OBJECT_WITHDRAWING;
717  enqueue = true;
718  }
719  spin_unlock(&object->lock);
720 
721  if (enqueue)
722  fscache_enqueue_object(object);
723 
724  _leave("");
725 }
726 
727 /*
728  * get a ref on an object
729  */
730 static int fscache_get_object(struct fscache_object *object)
731 {
732  int ret;
733 
734  fscache_stat(&fscache_n_cop_grab_object);
735  ret = object->cache->ops->grab_object(object) ? 0 : -EAGAIN;
736  fscache_stat_d(&fscache_n_cop_grab_object);
737  return ret;
738 }
739 
740 /*
741  * discard a ref on a work item
742  */
743 static void fscache_put_object(struct fscache_object *object)
744 {
745  fscache_stat(&fscache_n_cop_put_object);
746  object->cache->ops->put_object(object);
747  fscache_stat_d(&fscache_n_cop_put_object);
748 }
749 
750 /*
751  * enqueue an object for metadata-type processing
752  */
753 void fscache_enqueue_object(struct fscache_object *object)
754 {
755  _enter("{OBJ%x}", object->debug_id);
756 
757  if (fscache_get_object(object) >= 0) {
758  wait_queue_head_t *cong_wq =
759  &get_cpu_var(fscache_object_cong_wait);
760 
761  if (queue_work(fscache_object_wq, &object->work)) {
762  if (fscache_object_congested())
763  wake_up(cong_wq);
764  } else
765  fscache_put_object(object);
766 
767  put_cpu_var(fscache_object_cong_wait);
768  }
769 }
770 
783 bool fscache_object_sleep_till_congested(signed long *timeoutp)
784 {
785  wait_queue_head_t *cong_wq = &__get_cpu_var(fscache_object_cong_wait);
786  DEFINE_WAIT(wait);
787 
788  if (fscache_object_congested())
789  return true;
790 
791  add_wait_queue_exclusive(cong_wq, &wait);
792  if (!fscache_object_congested())
793  *timeoutp = schedule_timeout(*timeoutp);
794  finish_wait(cong_wq, &wait);
795 
796  return fscache_object_congested();
797 }
798 EXPORT_SYMBOL_GPL(fscache_object_sleep_till_congested);
799 
800 /*
801  * enqueue the dependents of an object for metadata-type processing
802  * - the caller must hold the object's lock
803  * - this may cause an already locked object to wind up being processed again
804  */
805 static void fscache_enqueue_dependents(struct fscache_object *object)
806 {
807  struct fscache_object *dep;
808 
809  _enter("{OBJ%x}", object->debug_id);
810 
811  if (list_empty(&object->dependents))
812  return;
813 
814  spin_lock(&object->lock);
815 
816  while (!list_empty(&object->dependents)) {
817  dep = list_entry(object->dependents.next,
818  struct fscache_object, dep_link);
819  list_del_init(&dep->dep_link);
820 
821 
822  /* sort onto appropriate lists */
823  fscache_enqueue_object(dep);
824  fscache_put_object(dep);
825 
826  if (!list_empty(&object->dependents))
827  cond_resched_lock(&object->lock);
828  }
829 
830  spin_unlock(&object->lock);
831 }
832 
833 /*
834  * remove an object from whatever queue it's waiting on
835  * - the caller must hold object->lock
836  */
837 void fscache_dequeue_object(struct fscache_object *object)
838 {
839  _enter("{OBJ%x}", object->debug_id);
840 
841  if (!list_empty(&object->dep_link)) {
842  spin_lock(&object->parent->lock);
843  list_del_init(&object->dep_link);
844  spin_unlock(&object->parent->lock);
845  }
846 
847  _leave("");
848 }
849 
858 enum fscache_checkaux fscache_check_aux(struct fscache_object *object,
859  const void *data, uint16_t datalen)
860 {
861  enum fscache_checkaux result;
862 
863  if (!object->cookie->def->check_aux) {
864  fscache_stat(&fscache_n_checkaux_none);
865  return FSCACHE_CHECKAUX_OKAY;
866  }
867 
868  result = object->cookie->def->check_aux(object->cookie->netfs_data,
869  data, datalen);
870  switch (result) {
871  /* entry okay as is */
872  case FSCACHE_CHECKAUX_OKAY:
873  fscache_stat(&fscache_n_checkaux_okay);
874  break;
875 
876  /* entry requires update */
877  case FSCACHE_CHECKAUX_NEEDS_UPDATE:
878  fscache_stat(&fscache_n_checkaux_update);
879  break;
880 
881  /* entry requires deletion */
882  case FSCACHE_CHECKAUX_OBSOLETE:
883  fscache_stat(&fscache_n_checkaux_obsolete);
884  break;
885 
886  default:
887  BUG();
888  }
889 
890  return result;
891 }
892 EXPORT_SYMBOL(fscache_check_aux);
Generated on Thu Jan 10 2013 13:32:11 for Linux Kernel by   doxygen 1.8.2