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

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  1 /* FS-Cache worker operation management routines
  2  *
  3  * Copyright (C) 2008 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/operations.txt
 12  */
 13 
 14 #define FSCACHE_DEBUG_LEVEL OPERATION
 15 #include <linux/module.h>
 16 #include <linux/seq_file.h>
 17 #include <linux/slab.h>
 18 #include "internal.h"
 19 
 20 atomic_t fscache_op_debug_id;
 21 EXPORT_SYMBOL(fscache_op_debug_id);
 22 
 23 static void fscache_operation_dummy_cancel(struct fscache_operation *op)
 24 {
 25 }
 26 
 27 /**
 28  * fscache_operation_init - Do basic initialisation of an operation
 29  * @op: The operation to initialise
 30  * @release: The release function to assign
 31  *
 32  * Do basic initialisation of an operation.  The caller must still set flags,
 33  * object and processor if needed.
 34  */
 35 void fscache_operation_init(struct fscache_cookie *cookie,
 36                             struct fscache_operation *op,
 37                             fscache_operation_processor_t processor,
 38                             fscache_operation_cancel_t cancel,
 39                             fscache_operation_release_t release)
 40 {
 41         INIT_WORK(&op->work, fscache_op_work_func);
 42         atomic_set(&op->usage, 1);
 43         op->state = FSCACHE_OP_ST_INITIALISED;
 44         op->debug_id = atomic_inc_return(&fscache_op_debug_id);
 45         op->processor = processor;
 46         op->cancel = cancel ?: fscache_operation_dummy_cancel;
 47         op->release = release;
 48         INIT_LIST_HEAD(&op->pend_link);
 49         fscache_stat(&fscache_n_op_initialised);
 50         trace_fscache_op(cookie, op, fscache_op_init);
 51 }
 52 EXPORT_SYMBOL(fscache_operation_init);
 53 
 54 /**
 55  * fscache_enqueue_operation - Enqueue an operation for processing
 56  * @op: The operation to enqueue
 57  *
 58  * Enqueue an operation for processing by the FS-Cache thread pool.
 59  *
 60  * This will get its own ref on the object.
 61  */
 62 void fscache_enqueue_operation(struct fscache_operation *op)
 63 {
 64         struct fscache_cookie *cookie = op->object->cookie;
 65         
 66         _enter("{OBJ%x OP%x,%u}",
 67                op->object->debug_id, op->debug_id, atomic_read(&op->usage));
 68 
 69         ASSERT(list_empty(&op->pend_link));
 70         ASSERT(op->processor != NULL);
 71         ASSERT(fscache_object_is_available(op->object));
 72         ASSERTCMP(atomic_read(&op->usage), >, 0);
 73         ASSERTCMP(op->state, ==, FSCACHE_OP_ST_IN_PROGRESS);
 74 
 75         fscache_stat(&fscache_n_op_enqueue);
 76         switch (op->flags & FSCACHE_OP_TYPE) {
 77         case FSCACHE_OP_ASYNC:
 78                 trace_fscache_op(cookie, op, fscache_op_enqueue_async);
 79                 _debug("queue async");
 80                 atomic_inc(&op->usage);
 81                 if (!queue_work(fscache_op_wq, &op->work))
 82                         fscache_put_operation(op);
 83                 break;
 84         case FSCACHE_OP_MYTHREAD:
 85                 trace_fscache_op(cookie, op, fscache_op_enqueue_mythread);
 86                 _debug("queue for caller's attention");
 87                 break;
 88         default:
 89                 pr_err("Unexpected op type %lx", op->flags);
 90                 BUG();
 91                 break;
 92         }
 93 }
 94 EXPORT_SYMBOL(fscache_enqueue_operation);
 95 
 96 /*
 97  * start an op running
 98  */
 99 static void fscache_run_op(struct fscache_object *object,
100                            struct fscache_operation *op)
101 {
102         ASSERTCMP(op->state, ==, FSCACHE_OP_ST_PENDING);
103 
104         op->state = FSCACHE_OP_ST_IN_PROGRESS;
105         object->n_in_progress++;
106         if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
107                 wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
108         if (op->processor)
109                 fscache_enqueue_operation(op);
110         else
111                 trace_fscache_op(object->cookie, op, fscache_op_run);
112         fscache_stat(&fscache_n_op_run);
113 }
114 
115 /*
116  * report an unexpected submission
117  */
118 static void fscache_report_unexpected_submission(struct fscache_object *object,
119                                                  struct fscache_operation *op,
120                                                  const struct fscache_state *ostate)
121 {
122         static bool once_only;
123         struct fscache_operation *p;
124         unsigned n;
125 
126         if (once_only)
127                 return;
128         once_only = true;
129 
130         kdebug("unexpected submission OP%x [OBJ%x %s]",
131                op->debug_id, object->debug_id, object->state->name);
132         kdebug("objstate=%s [%s]", object->state->name, ostate->name);
133         kdebug("objflags=%lx", object->flags);
134         kdebug("objevent=%lx [%lx]", object->events, object->event_mask);
135         kdebug("ops=%u inp=%u exc=%u",
136                object->n_ops, object->n_in_progress, object->n_exclusive);
137 
138         if (!list_empty(&object->pending_ops)) {
139                 n = 0;
140                 list_for_each_entry(p, &object->pending_ops, pend_link) {
141                         ASSERTCMP(p->object, ==, object);
142                         kdebug("%p %p", op->processor, op->release);
143                         n++;
144                 }
145 
146                 kdebug("n=%u", n);
147         }
148 
149         dump_stack();
150 }
151 
152 /*
153  * submit an exclusive operation for an object
154  * - other ops are excluded from running simultaneously with this one
155  * - this gets any extra refs it needs on an op
156  */
157 int fscache_submit_exclusive_op(struct fscache_object *object,
158                                 struct fscache_operation *op)
159 {
160         const struct fscache_state *ostate;
161         unsigned long flags;
162         int ret;
163 
164         _enter("{OBJ%x OP%x},", object->debug_id, op->debug_id);
165 
166         trace_fscache_op(object->cookie, op, fscache_op_submit_ex);
167 
168         ASSERTCMP(op->state, ==, FSCACHE_OP_ST_INITIALISED);
169         ASSERTCMP(atomic_read(&op->usage), >, 0);
170 
171         spin_lock(&object->lock);
172         ASSERTCMP(object->n_ops, >=, object->n_in_progress);
173         ASSERTCMP(object->n_ops, >=, object->n_exclusive);
174         ASSERT(list_empty(&op->pend_link));
175 
176         ostate = object->state;
177         smp_rmb();
178 
179         op->state = FSCACHE_OP_ST_PENDING;
180         flags = READ_ONCE(object->flags);
181         if (unlikely(!(flags & BIT(FSCACHE_OBJECT_IS_LIVE)))) {
182                 fscache_stat(&fscache_n_op_rejected);
183                 op->cancel(op);
184                 op->state = FSCACHE_OP_ST_CANCELLED;
185                 ret = -ENOBUFS;
186         } else if (unlikely(fscache_cache_is_broken(object))) {
187                 op->cancel(op);
188                 op->state = FSCACHE_OP_ST_CANCELLED;
189                 ret = -EIO;
190         } else if (flags & BIT(FSCACHE_OBJECT_IS_AVAILABLE)) {
191                 op->object = object;
192                 object->n_ops++;
193                 object->n_exclusive++;  /* reads and writes must wait */
194 
195                 if (object->n_in_progress > 0) {
196                         atomic_inc(&op->usage);
197                         list_add_tail(&op->pend_link, &object->pending_ops);
198                         fscache_stat(&fscache_n_op_pend);
199                 } else if (!list_empty(&object->pending_ops)) {
200                         atomic_inc(&op->usage);
201                         list_add_tail(&op->pend_link, &object->pending_ops);
202                         fscache_stat(&fscache_n_op_pend);
203                         fscache_start_operations(object);
204                 } else {
205                         ASSERTCMP(object->n_in_progress, ==, 0);
206                         fscache_run_op(object, op);
207                 }
208 
209                 /* need to issue a new write op after this */
210                 clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags);
211                 ret = 0;
212         } else if (flags & BIT(FSCACHE_OBJECT_IS_LOOKED_UP)) {
213                 op->object = object;
214                 object->n_ops++;
215                 object->n_exclusive++;  /* reads and writes must wait */
216                 atomic_inc(&op->usage);
217                 list_add_tail(&op->pend_link, &object->pending_ops);
218                 fscache_stat(&fscache_n_op_pend);
219                 ret = 0;
220         } else if (flags & BIT(FSCACHE_OBJECT_KILLED_BY_CACHE)) {
221                 op->cancel(op);
222                 op->state = FSCACHE_OP_ST_CANCELLED;
223                 ret = -ENOBUFS;
224         } else {
225                 fscache_report_unexpected_submission(object, op, ostate);
226                 op->cancel(op);
227                 op->state = FSCACHE_OP_ST_CANCELLED;
228                 ret = -ENOBUFS;
229         }
230 
231         spin_unlock(&object->lock);
232         return ret;
233 }
234 
235 /*
236  * submit an operation for an object
237  * - objects may be submitted only in the following states:
238  *   - during object creation (write ops may be submitted)
239  *   - whilst the object is active
240  *   - after an I/O error incurred in one of the two above states (op rejected)
241  * - this gets any extra refs it needs on an op
242  */
243 int fscache_submit_op(struct fscache_object *object,
244                       struct fscache_operation *op)
245 {
246         const struct fscache_state *ostate;
247         unsigned long flags;
248         int ret;
249 
250         _enter("{OBJ%x OP%x},{%u}",
251                object->debug_id, op->debug_id, atomic_read(&op->usage));
252 
253         trace_fscache_op(object->cookie, op, fscache_op_submit);
254 
255         ASSERTCMP(op->state, ==, FSCACHE_OP_ST_INITIALISED);
256         ASSERTCMP(atomic_read(&op->usage), >, 0);
257 
258         spin_lock(&object->lock);
259         ASSERTCMP(object->n_ops, >=, object->n_in_progress);
260         ASSERTCMP(object->n_ops, >=, object->n_exclusive);
261         ASSERT(list_empty(&op->pend_link));
262 
263         ostate = object->state;
264         smp_rmb();
265 
266         op->state = FSCACHE_OP_ST_PENDING;
267         flags = READ_ONCE(object->flags);
268         if (unlikely(!(flags & BIT(FSCACHE_OBJECT_IS_LIVE)))) {
269                 fscache_stat(&fscache_n_op_rejected);
270                 op->cancel(op);
271                 op->state = FSCACHE_OP_ST_CANCELLED;
272                 ret = -ENOBUFS;
273         } else if (unlikely(fscache_cache_is_broken(object))) {
274                 op->cancel(op);
275                 op->state = FSCACHE_OP_ST_CANCELLED;
276                 ret = -EIO;
277         } else if (flags & BIT(FSCACHE_OBJECT_IS_AVAILABLE)) {
278                 op->object = object;
279                 object->n_ops++;
280 
281                 if (object->n_exclusive > 0) {
282                         atomic_inc(&op->usage);
283                         list_add_tail(&op->pend_link, &object->pending_ops);
284                         fscache_stat(&fscache_n_op_pend);
285                 } else if (!list_empty(&object->pending_ops)) {
286                         atomic_inc(&op->usage);
287                         list_add_tail(&op->pend_link, &object->pending_ops);
288                         fscache_stat(&fscache_n_op_pend);
289                         fscache_start_operations(object);
290                 } else {
291                         ASSERTCMP(object->n_exclusive, ==, 0);
292                         fscache_run_op(object, op);
293                 }
294                 ret = 0;
295         } else if (flags & BIT(FSCACHE_OBJECT_IS_LOOKED_UP)) {
296                 op->object = object;
297                 object->n_ops++;
298                 atomic_inc(&op->usage);
299                 list_add_tail(&op->pend_link, &object->pending_ops);
300                 fscache_stat(&fscache_n_op_pend);
301                 ret = 0;
302         } else if (flags & BIT(FSCACHE_OBJECT_KILLED_BY_CACHE)) {
303                 op->cancel(op);
304                 op->state = FSCACHE_OP_ST_CANCELLED;
305                 ret = -ENOBUFS;
306         } else {
307                 fscache_report_unexpected_submission(object, op, ostate);
308                 ASSERT(!fscache_object_is_active(object));
309                 op->cancel(op);
310                 op->state = FSCACHE_OP_ST_CANCELLED;
311                 ret = -ENOBUFS;
312         }
313 
314         spin_unlock(&object->lock);
315         return ret;
316 }
317 
318 /*
319  * queue an object for withdrawal on error, aborting all following asynchronous
320  * operations
321  */
322 void fscache_abort_object(struct fscache_object *object)
323 {
324         _enter("{OBJ%x}", object->debug_id);
325 
326         fscache_raise_event(object, FSCACHE_OBJECT_EV_ERROR);
327 }
328 
329 /*
330  * Jump start the operation processing on an object.  The caller must hold
331  * object->lock.
332  */
333 void fscache_start_operations(struct fscache_object *object)
334 {
335         struct fscache_operation *op;
336         bool stop = false;
337 
338         while (!list_empty(&object->pending_ops) && !stop) {
339                 op = list_entry(object->pending_ops.next,
340                                 struct fscache_operation, pend_link);
341 
342                 if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags)) {
343                         if (object->n_in_progress > 0)
344                                 break;
345                         stop = true;
346                 }
347                 list_del_init(&op->pend_link);
348                 fscache_run_op(object, op);
349 
350                 /* the pending queue was holding a ref on the object */
351                 fscache_put_operation(op);
352         }
353 
354         ASSERTCMP(object->n_in_progress, <=, object->n_ops);
355 
356         _debug("woke %d ops on OBJ%x",
357                object->n_in_progress, object->debug_id);
358 }
359 
360 /*
361  * cancel an operation that's pending on an object
362  */
363 int fscache_cancel_op(struct fscache_operation *op,
364                       bool cancel_in_progress_op)
365 {
366         struct fscache_object *object = op->object;
367         bool put = false;
368         int ret;
369 
370         _enter("OBJ%x OP%x}", op->object->debug_id, op->debug_id);
371 
372         trace_fscache_op(object->cookie, op, fscache_op_cancel);
373 
374         ASSERTCMP(op->state, >=, FSCACHE_OP_ST_PENDING);
375         ASSERTCMP(op->state, !=, FSCACHE_OP_ST_CANCELLED);
376         ASSERTCMP(atomic_read(&op->usage), >, 0);
377 
378         spin_lock(&object->lock);
379 
380         ret = -EBUSY;
381         if (op->state == FSCACHE_OP_ST_PENDING) {
382                 ASSERT(!list_empty(&op->pend_link));
383                 list_del_init(&op->pend_link);
384                 put = true;
385 
386                 fscache_stat(&fscache_n_op_cancelled);
387                 op->cancel(op);
388                 op->state = FSCACHE_OP_ST_CANCELLED;
389                 if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
390                         object->n_exclusive--;
391                 if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
392                         wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
393                 ret = 0;
394         } else if (op->state == FSCACHE_OP_ST_IN_PROGRESS && cancel_in_progress_op) {
395                 ASSERTCMP(object->n_in_progress, >, 0);
396                 if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
397                         object->n_exclusive--;
398                 object->n_in_progress--;
399                 if (object->n_in_progress == 0)
400                         fscache_start_operations(object);
401 
402                 fscache_stat(&fscache_n_op_cancelled);
403                 op->cancel(op);
404                 op->state = FSCACHE_OP_ST_CANCELLED;
405                 if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
406                         object->n_exclusive--;
407                 if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
408                         wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
409                 ret = 0;
410         }
411 
412         if (put)
413                 fscache_put_operation(op);
414         spin_unlock(&object->lock);
415         _leave(" = %d", ret);
416         return ret;
417 }
418 
419 /*
420  * Cancel all pending operations on an object
421  */
422 void fscache_cancel_all_ops(struct fscache_object *object)
423 {
424         struct fscache_operation *op;
425 
426         _enter("OBJ%x", object->debug_id);
427 
428         spin_lock(&object->lock);
429 
430         while (!list_empty(&object->pending_ops)) {
431                 op = list_entry(object->pending_ops.next,
432                                 struct fscache_operation, pend_link);
433                 fscache_stat(&fscache_n_op_cancelled);
434                 list_del_init(&op->pend_link);
435 
436                 trace_fscache_op(object->cookie, op, fscache_op_cancel_all);
437 
438                 ASSERTCMP(op->state, ==, FSCACHE_OP_ST_PENDING);
439                 op->cancel(op);
440                 op->state = FSCACHE_OP_ST_CANCELLED;
441 
442                 if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
443                         object->n_exclusive--;
444                 if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags))
445                         wake_up_bit(&op->flags, FSCACHE_OP_WAITING);
446                 fscache_put_operation(op);
447                 cond_resched_lock(&object->lock);
448         }
449 
450         spin_unlock(&object->lock);
451         _leave("");
452 }
453 
454 /*
455  * Record the completion or cancellation of an in-progress operation.
456  */
457 void fscache_op_complete(struct fscache_operation *op, bool cancelled)
458 {
459         struct fscache_object *object = op->object;
460 
461         _enter("OBJ%x", object->debug_id);
462 
463         ASSERTCMP(op->state, ==, FSCACHE_OP_ST_IN_PROGRESS);
464         ASSERTCMP(object->n_in_progress, >, 0);
465         ASSERTIFCMP(test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags),
466                     object->n_exclusive, >, 0);
467         ASSERTIFCMP(test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags),
468                     object->n_in_progress, ==, 1);
469 
470         spin_lock(&object->lock);
471 
472         if (!cancelled) {
473                 trace_fscache_op(object->cookie, op, fscache_op_completed);
474                 op->state = FSCACHE_OP_ST_COMPLETE;
475         } else {
476                 op->cancel(op);
477                 trace_fscache_op(object->cookie, op, fscache_op_cancelled);
478                 op->state = FSCACHE_OP_ST_CANCELLED;
479         }
480 
481         if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags))
482                 object->n_exclusive--;
483         object->n_in_progress--;
484         if (object->n_in_progress == 0)
485                 fscache_start_operations(object);
486 
487         spin_unlock(&object->lock);
488         _leave("");
489 }
490 EXPORT_SYMBOL(fscache_op_complete);
491 
492 /*
493  * release an operation
494  * - queues pending ops if this is the last in-progress op
495  */
496 void fscache_put_operation(struct fscache_operation *op)
497 {
498         struct fscache_object *object;
499         struct fscache_cache *cache;
500 
501         _enter("{OBJ%x OP%x,%d}",
502                op->object->debug_id, op->debug_id, atomic_read(&op->usage));
503 
504         ASSERTCMP(atomic_read(&op->usage), >, 0);
505 
506         if (!atomic_dec_and_test(&op->usage))
507                 return;
508 
509         trace_fscache_op(op->object ? op->object->cookie : NULL, op, fscache_op_put);
510 
511         _debug("PUT OP");
512         ASSERTIFCMP(op->state != FSCACHE_OP_ST_INITIALISED &&
513                     op->state != FSCACHE_OP_ST_COMPLETE,
514                     op->state, ==, FSCACHE_OP_ST_CANCELLED);
515 
516         fscache_stat(&fscache_n_op_release);
517 
518         if (op->release) {
519                 op->release(op);
520                 op->release = NULL;
521         }
522         op->state = FSCACHE_OP_ST_DEAD;
523 
524         object = op->object;
525         if (likely(object)) {
526                 if (test_bit(FSCACHE_OP_DEC_READ_CNT, &op->flags))
527                         atomic_dec(&object->n_reads);
528                 if (test_bit(FSCACHE_OP_UNUSE_COOKIE, &op->flags))
529                         fscache_unuse_cookie(object);
530 
531                 /* now... we may get called with the object spinlock held, so we
532                  * complete the cleanup here only if we can immediately acquire the
533                  * lock, and defer it otherwise */
534                 if (!spin_trylock(&object->lock)) {
535                         _debug("defer put");
536                         fscache_stat(&fscache_n_op_deferred_release);
537 
538                         cache = object->cache;
539                         spin_lock(&cache->op_gc_list_lock);
540                         list_add_tail(&op->pend_link, &cache->op_gc_list);
541                         spin_unlock(&cache->op_gc_list_lock);
542                         schedule_work(&cache->op_gc);
543                         _leave(" [defer]");
544                         return;
545                 }
546 
547                 ASSERTCMP(object->n_ops, >, 0);
548                 object->n_ops--;
549                 if (object->n_ops == 0)
550                         fscache_raise_event(object, FSCACHE_OBJECT_EV_CLEARED);
551 
552                 spin_unlock(&object->lock);
553         }
554 
555         kfree(op);
556         _leave(" [done]");
557 }
558 EXPORT_SYMBOL(fscache_put_operation);
559 
560 /*
561  * garbage collect operations that have had their release deferred
562  */
563 void fscache_operation_gc(struct work_struct *work)
564 {
565         struct fscache_operation *op;
566         struct fscache_object *object;
567         struct fscache_cache *cache =
568                 container_of(work, struct fscache_cache, op_gc);
569         int count = 0;
570 
571         _enter("");
572 
573         do {
574                 spin_lock(&cache->op_gc_list_lock);
575                 if (list_empty(&cache->op_gc_list)) {
576                         spin_unlock(&cache->op_gc_list_lock);
577                         break;
578                 }
579 
580                 op = list_entry(cache->op_gc_list.next,
581                                 struct fscache_operation, pend_link);
582                 list_del(&op->pend_link);
583                 spin_unlock(&cache->op_gc_list_lock);
584 
585                 object = op->object;
586                 trace_fscache_op(object->cookie, op, fscache_op_gc);
587 
588                 spin_lock(&object->lock);
589 
590                 _debug("GC DEFERRED REL OBJ%x OP%x",
591                        object->debug_id, op->debug_id);
592                 fscache_stat(&fscache_n_op_gc);
593 
594                 ASSERTCMP(atomic_read(&op->usage), ==, 0);
595                 ASSERTCMP(op->state, ==, FSCACHE_OP_ST_DEAD);
596 
597                 ASSERTCMP(object->n_ops, >, 0);
598                 object->n_ops--;
599                 if (object->n_ops == 0)
600                         fscache_raise_event(object, FSCACHE_OBJECT_EV_CLEARED);
601 
602                 spin_unlock(&object->lock);
603                 kfree(op);
604 
605         } while (count++ < 20);
606 
607         if (!list_empty(&cache->op_gc_list))
608                 schedule_work(&cache->op_gc);
609 
610         _leave("");
611 }
612 
613 /*
614  * execute an operation using fs_op_wq to provide processing context -
615  * the caller holds a ref to this object, so we don't need to hold one
616  */
617 void fscache_op_work_func(struct work_struct *work)
618 {
619         struct fscache_operation *op =
620                 container_of(work, struct fscache_operation, work);
621         unsigned long start;
622 
623         _enter("{OBJ%x OP%x,%d}",
624                op->object->debug_id, op->debug_id, atomic_read(&op->usage));
625 
626         trace_fscache_op(op->object->cookie, op, fscache_op_work);
627 
628         ASSERT(op->processor != NULL);
629         start = jiffies;
630         op->processor(op);
631         fscache_hist(fscache_ops_histogram, start);
632         fscache_put_operation(op);
633 
634         _leave("");
635 }
636 

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