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

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