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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 "internal.h" | |
17 | ||
18 | atomic_t fscache_op_debug_id; | |
19 | EXPORT_SYMBOL(fscache_op_debug_id); | |
20 | ||
21 | /** | |
22 | * fscache_enqueue_operation - Enqueue an operation for processing | |
23 | * @op: The operation to enqueue | |
24 | * | |
25 | * Enqueue an operation for processing by the FS-Cache thread pool. | |
26 | * | |
27 | * This will get its own ref on the object. | |
28 | */ | |
29 | void fscache_enqueue_operation(struct fscache_operation *op) | |
30 | { | |
31 | _enter("{OBJ%x OP%x,%u}", | |
32 | op->object->debug_id, op->debug_id, atomic_read(&op->usage)); | |
33 | ||
34 | ASSERT(op->processor != NULL); | |
35 | ASSERTCMP(op->object->state, >=, FSCACHE_OBJECT_AVAILABLE); | |
36 | ASSERTCMP(atomic_read(&op->usage), >, 0); | |
37 | ||
38 | if (list_empty(&op->pend_link)) { | |
39 | switch (op->flags & FSCACHE_OP_TYPE) { | |
40 | case FSCACHE_OP_FAST: | |
41 | _debug("queue fast"); | |
42 | atomic_inc(&op->usage); | |
43 | if (!schedule_work(&op->fast_work)) | |
44 | fscache_put_operation(op); | |
45 | break; | |
46 | case FSCACHE_OP_SLOW: | |
47 | _debug("queue slow"); | |
48 | slow_work_enqueue(&op->slow_work); | |
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 | fscache_stat(&fscache_n_op_enqueue); | |
60 | } | |
61 | } | |
62 | EXPORT_SYMBOL(fscache_enqueue_operation); | |
63 | ||
64 | /* | |
65 | * start an op running | |
66 | */ | |
67 | static void fscache_run_op(struct fscache_object *object, | |
68 | struct fscache_operation *op) | |
69 | { | |
70 | object->n_in_progress++; | |
71 | if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags)) | |
72 | wake_up_bit(&op->flags, FSCACHE_OP_WAITING); | |
73 | if (op->processor) | |
74 | fscache_enqueue_operation(op); | |
75 | fscache_stat(&fscache_n_op_run); | |
76 | } | |
77 | ||
78 | /* | |
79 | * submit an exclusive operation for an object | |
80 | * - other ops are excluded from running simultaneously with this one | |
81 | * - this gets any extra refs it needs on an op | |
82 | */ | |
83 | int fscache_submit_exclusive_op(struct fscache_object *object, | |
84 | struct fscache_operation *op) | |
85 | { | |
86 | int ret; | |
87 | ||
88 | _enter("{OBJ%x OP%x},", object->debug_id, op->debug_id); | |
89 | ||
90 | spin_lock(&object->lock); | |
91 | ASSERTCMP(object->n_ops, >=, object->n_in_progress); | |
92 | ASSERTCMP(object->n_ops, >=, object->n_exclusive); | |
93 | ||
94 | ret = -ENOBUFS; | |
95 | if (fscache_object_is_active(object)) { | |
96 | op->object = object; | |
97 | object->n_ops++; | |
98 | object->n_exclusive++; /* reads and writes must wait */ | |
99 | ||
100 | if (object->n_ops > 0) { | |
101 | atomic_inc(&op->usage); | |
102 | list_add_tail(&op->pend_link, &object->pending_ops); | |
103 | fscache_stat(&fscache_n_op_pend); | |
104 | } else if (!list_empty(&object->pending_ops)) { | |
105 | atomic_inc(&op->usage); | |
106 | list_add_tail(&op->pend_link, &object->pending_ops); | |
107 | fscache_stat(&fscache_n_op_pend); | |
108 | fscache_start_operations(object); | |
109 | } else { | |
110 | ASSERTCMP(object->n_in_progress, ==, 0); | |
111 | fscache_run_op(object, op); | |
112 | } | |
113 | ||
114 | /* need to issue a new write op after this */ | |
115 | clear_bit(FSCACHE_OBJECT_PENDING_WRITE, &object->flags); | |
116 | ret = 0; | |
117 | } else if (object->state == FSCACHE_OBJECT_CREATING) { | |
118 | op->object = object; | |
119 | object->n_ops++; | |
120 | object->n_exclusive++; /* reads and writes must wait */ | |
121 | atomic_inc(&op->usage); | |
122 | list_add_tail(&op->pend_link, &object->pending_ops); | |
123 | fscache_stat(&fscache_n_op_pend); | |
124 | ret = 0; | |
125 | } else { | |
126 | /* not allowed to submit ops in any other state */ | |
127 | BUG(); | |
128 | } | |
129 | ||
130 | spin_unlock(&object->lock); | |
131 | return ret; | |
132 | } | |
133 | ||
134 | /* | |
135 | * report an unexpected submission | |
136 | */ | |
137 | static void fscache_report_unexpected_submission(struct fscache_object *object, | |
138 | struct fscache_operation *op, | |
139 | unsigned long ostate) | |
140 | { | |
141 | static bool once_only; | |
142 | struct fscache_operation *p; | |
143 | unsigned n; | |
144 | ||
145 | if (once_only) | |
146 | return; | |
147 | once_only = true; | |
148 | ||
149 | kdebug("unexpected submission OP%x [OBJ%x %s]", | |
150 | op->debug_id, object->debug_id, | |
151 | fscache_object_states[object->state]); | |
152 | kdebug("objstate=%s [%s]", | |
153 | fscache_object_states[object->state], | |
154 | fscache_object_states[ostate]); | |
155 | kdebug("objflags=%lx", object->flags); | |
156 | kdebug("objevent=%lx [%lx]", object->events, object->event_mask); | |
157 | kdebug("ops=%u inp=%u exc=%u", | |
158 | object->n_ops, object->n_in_progress, object->n_exclusive); | |
159 | ||
160 | if (!list_empty(&object->pending_ops)) { | |
161 | n = 0; | |
162 | list_for_each_entry(p, &object->pending_ops, pend_link) { | |
163 | ASSERTCMP(p->object, ==, object); | |
164 | kdebug("%p %p", op->processor, op->release); | |
165 | n++; | |
166 | } | |
167 | ||
168 | kdebug("n=%u", n); | |
169 | } | |
170 | ||
171 | dump_stack(); | |
172 | } | |
173 | ||
174 | /* | |
175 | * submit an operation for an object | |
176 | * - objects may be submitted only in the following states: | |
177 | * - during object creation (write ops may be submitted) | |
178 | * - whilst the object is active | |
179 | * - after an I/O error incurred in one of the two above states (op rejected) | |
180 | * - this gets any extra refs it needs on an op | |
181 | */ | |
182 | int fscache_submit_op(struct fscache_object *object, | |
183 | struct fscache_operation *op) | |
184 | { | |
185 | unsigned long ostate; | |
186 | int ret; | |
187 | ||
188 | _enter("{OBJ%x OP%x},{%u}", | |
189 | object->debug_id, op->debug_id, atomic_read(&op->usage)); | |
190 | ||
191 | ASSERTCMP(atomic_read(&op->usage), >, 0); | |
192 | ||
193 | spin_lock(&object->lock); | |
194 | ASSERTCMP(object->n_ops, >=, object->n_in_progress); | |
195 | ASSERTCMP(object->n_ops, >=, object->n_exclusive); | |
196 | ||
197 | ostate = object->state; | |
198 | smp_rmb(); | |
199 | ||
200 | if (fscache_object_is_active(object)) { | |
201 | op->object = object; | |
202 | object->n_ops++; | |
203 | ||
204 | if (object->n_exclusive > 0) { | |
205 | atomic_inc(&op->usage); | |
206 | list_add_tail(&op->pend_link, &object->pending_ops); | |
207 | fscache_stat(&fscache_n_op_pend); | |
208 | } else if (!list_empty(&object->pending_ops)) { | |
209 | atomic_inc(&op->usage); | |
210 | list_add_tail(&op->pend_link, &object->pending_ops); | |
211 | fscache_stat(&fscache_n_op_pend); | |
212 | fscache_start_operations(object); | |
213 | } else { | |
214 | ASSERTCMP(object->n_exclusive, ==, 0); | |
215 | fscache_run_op(object, op); | |
216 | } | |
217 | ret = 0; | |
218 | } else if (object->state == FSCACHE_OBJECT_CREATING) { | |
219 | op->object = object; | |
220 | object->n_ops++; | |
221 | atomic_inc(&op->usage); | |
222 | list_add_tail(&op->pend_link, &object->pending_ops); | |
223 | fscache_stat(&fscache_n_op_pend); | |
224 | ret = 0; | |
225 | } else if (!test_bit(FSCACHE_IOERROR, &object->cache->flags)) { | |
226 | fscache_report_unexpected_submission(object, op, ostate); | |
227 | ASSERT(!fscache_object_is_active(object)); | |
228 | ret = -ENOBUFS; | |
229 | } else { | |
230 | ret = -ENOBUFS; | |
231 | } | |
232 | ||
233 | spin_unlock(&object->lock); | |
234 | return ret; | |
235 | } | |
236 | ||
237 | /* | |
238 | * queue an object for withdrawal on error, aborting all following asynchronous | |
239 | * operations | |
240 | */ | |
241 | void fscache_abort_object(struct fscache_object *object) | |
242 | { | |
243 | _enter("{OBJ%x}", object->debug_id); | |
244 | ||
245 | fscache_raise_event(object, FSCACHE_OBJECT_EV_ERROR); | |
246 | } | |
247 | ||
248 | /* | |
249 | * jump start the operation processing on an object | |
250 | * - caller must hold object->lock | |
251 | */ | |
252 | void fscache_start_operations(struct fscache_object *object) | |
253 | { | |
254 | struct fscache_operation *op; | |
255 | bool stop = false; | |
256 | ||
257 | while (!list_empty(&object->pending_ops) && !stop) { | |
258 | op = list_entry(object->pending_ops.next, | |
259 | struct fscache_operation, pend_link); | |
260 | ||
261 | if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags)) { | |
262 | if (object->n_in_progress > 0) | |
263 | break; | |
264 | stop = true; | |
265 | } | |
266 | list_del_init(&op->pend_link); | |
267 | object->n_in_progress++; | |
268 | ||
269 | if (test_and_clear_bit(FSCACHE_OP_WAITING, &op->flags)) | |
270 | wake_up_bit(&op->flags, FSCACHE_OP_WAITING); | |
271 | if (op->processor) | |
272 | fscache_enqueue_operation(op); | |
273 | ||
274 | /* the pending queue was holding a ref on the object */ | |
275 | fscache_put_operation(op); | |
276 | } | |
277 | ||
278 | ASSERTCMP(object->n_in_progress, <=, object->n_ops); | |
279 | ||
280 | _debug("woke %d ops on OBJ%x", | |
281 | object->n_in_progress, object->debug_id); | |
282 | } | |
283 | ||
284 | /* | |
285 | * release an operation | |
286 | * - queues pending ops if this is the last in-progress op | |
287 | */ | |
288 | void fscache_put_operation(struct fscache_operation *op) | |
289 | { | |
290 | struct fscache_object *object; | |
291 | struct fscache_cache *cache; | |
292 | ||
293 | _enter("{OBJ%x OP%x,%d}", | |
294 | op->object->debug_id, op->debug_id, atomic_read(&op->usage)); | |
295 | ||
296 | ASSERTCMP(atomic_read(&op->usage), >, 0); | |
297 | ||
298 | if (!atomic_dec_and_test(&op->usage)) | |
299 | return; | |
300 | ||
301 | _debug("PUT OP"); | |
302 | if (test_and_set_bit(FSCACHE_OP_DEAD, &op->flags)) | |
303 | BUG(); | |
304 | ||
305 | fscache_stat(&fscache_n_op_release); | |
306 | ||
307 | if (op->release) { | |
308 | op->release(op); | |
309 | op->release = NULL; | |
310 | } | |
311 | ||
312 | object = op->object; | |
313 | ||
314 | /* now... we may get called with the object spinlock held, so we | |
315 | * complete the cleanup here only if we can immediately acquire the | |
316 | * lock, and defer it otherwise */ | |
317 | if (!spin_trylock(&object->lock)) { | |
318 | _debug("defer put"); | |
319 | fscache_stat(&fscache_n_op_deferred_release); | |
320 | ||
321 | cache = object->cache; | |
322 | spin_lock(&cache->op_gc_list_lock); | |
323 | list_add_tail(&op->pend_link, &cache->op_gc_list); | |
324 | spin_unlock(&cache->op_gc_list_lock); | |
325 | schedule_work(&cache->op_gc); | |
326 | _leave(" [defer]"); | |
327 | return; | |
328 | } | |
329 | ||
330 | if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags)) { | |
331 | ASSERTCMP(object->n_exclusive, >, 0); | |
332 | object->n_exclusive--; | |
333 | } | |
334 | ||
335 | ASSERTCMP(object->n_in_progress, >, 0); | |
336 | object->n_in_progress--; | |
337 | if (object->n_in_progress == 0) | |
338 | fscache_start_operations(object); | |
339 | ||
340 | ASSERTCMP(object->n_ops, >, 0); | |
341 | object->n_ops--; | |
342 | if (object->n_ops == 0) | |
343 | fscache_raise_event(object, FSCACHE_OBJECT_EV_CLEARED); | |
344 | ||
345 | spin_unlock(&object->lock); | |
346 | ||
347 | kfree(op); | |
348 | _leave(" [done]"); | |
349 | } | |
350 | EXPORT_SYMBOL(fscache_put_operation); | |
351 | ||
352 | /* | |
353 | * garbage collect operations that have had their release deferred | |
354 | */ | |
355 | void fscache_operation_gc(struct work_struct *work) | |
356 | { | |
357 | struct fscache_operation *op; | |
358 | struct fscache_object *object; | |
359 | struct fscache_cache *cache = | |
360 | container_of(work, struct fscache_cache, op_gc); | |
361 | int count = 0; | |
362 | ||
363 | _enter(""); | |
364 | ||
365 | do { | |
366 | spin_lock(&cache->op_gc_list_lock); | |
367 | if (list_empty(&cache->op_gc_list)) { | |
368 | spin_unlock(&cache->op_gc_list_lock); | |
369 | break; | |
370 | } | |
371 | ||
372 | op = list_entry(cache->op_gc_list.next, | |
373 | struct fscache_operation, pend_link); | |
374 | list_del(&op->pend_link); | |
375 | spin_unlock(&cache->op_gc_list_lock); | |
376 | ||
377 | object = op->object; | |
378 | ||
379 | _debug("GC DEFERRED REL OBJ%x OP%x", | |
380 | object->debug_id, op->debug_id); | |
381 | fscache_stat(&fscache_n_op_gc); | |
382 | ||
383 | ASSERTCMP(atomic_read(&op->usage), ==, 0); | |
384 | ||
385 | spin_lock(&object->lock); | |
386 | if (test_bit(FSCACHE_OP_EXCLUSIVE, &op->flags)) { | |
387 | ASSERTCMP(object->n_exclusive, >, 0); | |
388 | object->n_exclusive--; | |
389 | } | |
390 | ||
391 | ASSERTCMP(object->n_in_progress, >, 0); | |
392 | object->n_in_progress--; | |
393 | if (object->n_in_progress == 0) | |
394 | fscache_start_operations(object); | |
395 | ||
396 | ASSERTCMP(object->n_ops, >, 0); | |
397 | object->n_ops--; | |
398 | if (object->n_ops == 0) | |
399 | fscache_raise_event(object, FSCACHE_OBJECT_EV_CLEARED); | |
400 | ||
401 | spin_unlock(&object->lock); | |
402 | ||
403 | } while (count++ < 20); | |
404 | ||
405 | if (!list_empty(&cache->op_gc_list)) | |
406 | schedule_work(&cache->op_gc); | |
407 | ||
408 | _leave(""); | |
409 | } | |
410 | ||
411 | /* | |
412 | * allow the slow work item processor to get a ref on an operation | |
413 | */ | |
414 | static int fscache_op_get_ref(struct slow_work *work) | |
415 | { | |
416 | struct fscache_operation *op = | |
417 | container_of(work, struct fscache_operation, slow_work); | |
418 | ||
419 | atomic_inc(&op->usage); | |
420 | return 0; | |
421 | } | |
422 | ||
423 | /* | |
424 | * allow the slow work item processor to discard a ref on an operation | |
425 | */ | |
426 | static void fscache_op_put_ref(struct slow_work *work) | |
427 | { | |
428 | struct fscache_operation *op = | |
429 | container_of(work, struct fscache_operation, slow_work); | |
430 | ||
431 | fscache_put_operation(op); | |
432 | } | |
433 | ||
434 | /* | |
435 | * execute an operation using the slow thread pool to provide processing context | |
436 | * - the caller holds a ref to this object, so we don't need to hold one | |
437 | */ | |
438 | static void fscache_op_execute(struct slow_work *work) | |
439 | { | |
440 | struct fscache_operation *op = | |
441 | container_of(work, struct fscache_operation, slow_work); | |
442 | unsigned long start; | |
443 | ||
444 | _enter("{OBJ%x OP%x,%d}", | |
445 | op->object->debug_id, op->debug_id, atomic_read(&op->usage)); | |
446 | ||
447 | ASSERT(op->processor != NULL); | |
448 | start = jiffies; | |
449 | op->processor(op); | |
450 | fscache_hist(fscache_ops_histogram, start); | |
451 | ||
452 | _leave(""); | |
453 | } | |
454 | ||
455 | const struct slow_work_ops fscache_op_slow_work_ops = { | |
456 | .get_ref = fscache_op_get_ref, | |
457 | .put_ref = fscache_op_put_ref, | |
458 | .execute = fscache_op_execute, | |
459 | }; |