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TOMOYO Linux Cross Reference
Linux/fs/fscache/object.c

Version: ~ [ linux-5.2-rc1 ] ~ [ linux-5.1.2 ] ~ [ linux-5.0.16 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.43 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.119 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.176 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.179 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.19.8 ] ~ [ linux-3.18.139 ] ~ [ linux-3.17.8 ] ~ [ linux-3.16.67 ] ~ [ linux-3.15.10 ] ~ [ linux-3.14.79 ] ~ [ linux-3.13.11 ] ~ [ linux-3.12.74 ] ~ [ linux-3.11.10 ] ~ [ linux-3.10.108 ] ~ [ linux-3.9.11 ] ~ [ linux-3.8.13 ] ~ [ linux-3.7.10 ] ~ [ linux-3.6.11 ] ~ [ linux-3.5.7 ] ~ [ linux-3.4.113 ] ~ [ linux-3.3.8 ] ~ [ linux-3.2.102 ] ~ [ linux-3.1.10 ] ~ [ linux-3.0.101 ] ~ [ linux-2.6.39.4 ] ~ [ linux-2.6.38.8 ] ~ [ linux-2.6.37.6 ] ~ [ linux-2.6.36.4 ] ~ [ linux-2.6.35.14 ] ~ [ linux-2.6.34.15 ] ~ [ linux-2.6.33.20 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
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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 (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  * 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 
482 /**
483  * fscache_object_lookup_negative - Note negative cookie lookup
484  * @object: Object pointing to cookie to mark
485  *
486  * Note negative lookup, permitting those waiting to read data from an already
487  * existing backing object to continue as there's no data for them to read.
488  */
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 
523 /**
524  * fscache_obtained_object - Note successful object lookup or creation
525  * @object: Object pointing to cookie to mark
526  *
527  * Note successful lookup and/or creation, permitting those waiting to write
528  * data to a backing object to continue.
529  *
530  * Note that after calling this, an object's cookie may be relinquished by the
531  * netfs, and so must be accessed with object lock held.
532  */
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 
771 /**
772  * fscache_object_sleep_till_congested - Sleep until object wq is congested
773  * @timoutp: Scheduler sleep timeout
774  *
775  * Allow an object handler to sleep until the object workqueue is congested.
776  *
777  * The caller must set up a wake up event before calling this and must have set
778  * the appropriate sleep mode (such as TASK_UNINTERRUPTIBLE) and tested its own
779  * condition before calling this function as no test is made here.
780  *
781  * %true is returned if the object wq is congested, %false otherwise.
782  */
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 
850 /**
851  * fscache_check_aux - Ask the netfs whether an object on disk is still valid
852  * @object: The object to ask about
853  * @data: The auxiliary data for the object
854  * @datalen: The size of the auxiliary data
855  *
856  * This function consults the netfs about the coherency state of an object
857  */
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);
893 

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