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