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8b712842 CM |
1 | /* |
2 | * Copyright (C) 2007 Oracle. All rights reserved. | |
3 | * | |
4 | * This program is free software; you can redistribute it and/or | |
5 | * modify it under the terms of the GNU General Public | |
6 | * License v2 as published by the Free Software Foundation. | |
7 | * | |
8 | * This program is distributed in the hope that it will be useful, | |
9 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
10 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
11 | * General Public License for more details. | |
12 | * | |
13 | * You should have received a copy of the GNU General Public | |
14 | * License along with this program; if not, write to the | |
15 | * Free Software Foundation, Inc., 59 Temple Place - Suite 330, | |
16 | * Boston, MA 021110-1307, USA. | |
17 | */ | |
18 | ||
19 | #include <linux/kthread.h> | |
20 | #include <linux/list.h> | |
21 | #include <linux/spinlock.h> | |
b51912c9 CM |
22 | #include <linux/freezer.h> |
23 | #include <linux/ftrace.h> | |
8b712842 CM |
24 | #include "async-thread.h" |
25 | ||
4a69a410 CM |
26 | #define WORK_QUEUED_BIT 0 |
27 | #define WORK_DONE_BIT 1 | |
28 | #define WORK_ORDER_DONE_BIT 2 | |
29 | ||
8b712842 CM |
30 | /* |
31 | * container for the kthread task pointer and the list of pending work | |
32 | * One of these is allocated per thread. | |
33 | */ | |
34 | struct btrfs_worker_thread { | |
35d8ba66 CM |
35 | /* pool we belong to */ |
36 | struct btrfs_workers *workers; | |
37 | ||
8b712842 CM |
38 | /* list of struct btrfs_work that are waiting for service */ |
39 | struct list_head pending; | |
40 | ||
41 | /* list of worker threads from struct btrfs_workers */ | |
42 | struct list_head worker_list; | |
43 | ||
44 | /* kthread */ | |
45 | struct task_struct *task; | |
46 | ||
47 | /* number of things on the pending list */ | |
48 | atomic_t num_pending; | |
53863232 | 49 | |
4854ddd0 | 50 | unsigned long sequence; |
8b712842 CM |
51 | |
52 | /* protects the pending list. */ | |
53 | spinlock_t lock; | |
54 | ||
55 | /* set to non-zero when this thread is already awake and kicking */ | |
56 | int working; | |
35d8ba66 CM |
57 | |
58 | /* are we currently idle */ | |
59 | int idle; | |
8b712842 CM |
60 | }; |
61 | ||
35d8ba66 CM |
62 | /* |
63 | * helper function to move a thread onto the idle list after it | |
64 | * has finished some requests. | |
65 | */ | |
66 | static void check_idle_worker(struct btrfs_worker_thread *worker) | |
67 | { | |
68 | if (!worker->idle && atomic_read(&worker->num_pending) < | |
69 | worker->workers->idle_thresh / 2) { | |
70 | unsigned long flags; | |
71 | spin_lock_irqsave(&worker->workers->lock, flags); | |
72 | worker->idle = 1; | |
73 | list_move(&worker->worker_list, &worker->workers->idle_list); | |
74 | spin_unlock_irqrestore(&worker->workers->lock, flags); | |
75 | } | |
76 | } | |
77 | ||
78 | /* | |
79 | * helper function to move a thread off the idle list after new | |
80 | * pending work is added. | |
81 | */ | |
82 | static void check_busy_worker(struct btrfs_worker_thread *worker) | |
83 | { | |
84 | if (worker->idle && atomic_read(&worker->num_pending) >= | |
85 | worker->workers->idle_thresh) { | |
86 | unsigned long flags; | |
87 | spin_lock_irqsave(&worker->workers->lock, flags); | |
88 | worker->idle = 0; | |
89 | list_move_tail(&worker->worker_list, | |
90 | &worker->workers->worker_list); | |
91 | spin_unlock_irqrestore(&worker->workers->lock, flags); | |
92 | } | |
93 | } | |
94 | ||
4a69a410 CM |
95 | static noinline int run_ordered_completions(struct btrfs_workers *workers, |
96 | struct btrfs_work *work) | |
97 | { | |
98 | unsigned long flags; | |
99 | ||
100 | if (!workers->ordered) | |
101 | return 0; | |
102 | ||
103 | set_bit(WORK_DONE_BIT, &work->flags); | |
104 | ||
105 | spin_lock_irqsave(&workers->lock, flags); | |
106 | ||
d397712b | 107 | while (!list_empty(&workers->order_list)) { |
4a69a410 CM |
108 | work = list_entry(workers->order_list.next, |
109 | struct btrfs_work, order_list); | |
110 | ||
111 | if (!test_bit(WORK_DONE_BIT, &work->flags)) | |
112 | break; | |
113 | ||
114 | /* we are going to call the ordered done function, but | |
115 | * we leave the work item on the list as a barrier so | |
116 | * that later work items that are done don't have their | |
117 | * functions called before this one returns | |
118 | */ | |
119 | if (test_and_set_bit(WORK_ORDER_DONE_BIT, &work->flags)) | |
120 | break; | |
121 | ||
122 | spin_unlock_irqrestore(&workers->lock, flags); | |
123 | ||
124 | work->ordered_func(work); | |
125 | ||
126 | /* now take the lock again and call the freeing code */ | |
127 | spin_lock_irqsave(&workers->lock, flags); | |
128 | list_del(&work->order_list); | |
129 | work->ordered_free(work); | |
130 | } | |
131 | ||
132 | spin_unlock_irqrestore(&workers->lock, flags); | |
133 | return 0; | |
134 | } | |
135 | ||
8b712842 CM |
136 | /* |
137 | * main loop for servicing work items | |
138 | */ | |
139 | static int worker_loop(void *arg) | |
140 | { | |
141 | struct btrfs_worker_thread *worker = arg; | |
142 | struct list_head *cur; | |
143 | struct btrfs_work *work; | |
144 | do { | |
145 | spin_lock_irq(&worker->lock); | |
b51912c9 | 146 | again_locked: |
d397712b | 147 | while (!list_empty(&worker->pending)) { |
8b712842 CM |
148 | cur = worker->pending.next; |
149 | work = list_entry(cur, struct btrfs_work, list); | |
150 | list_del(&work->list); | |
4a69a410 | 151 | clear_bit(WORK_QUEUED_BIT, &work->flags); |
8b712842 CM |
152 | |
153 | work->worker = worker; | |
154 | spin_unlock_irq(&worker->lock); | |
155 | ||
156 | work->func(work); | |
157 | ||
158 | atomic_dec(&worker->num_pending); | |
4a69a410 CM |
159 | /* |
160 | * unless this is an ordered work queue, | |
161 | * 'work' was probably freed by func above. | |
162 | */ | |
163 | run_ordered_completions(worker->workers, work); | |
164 | ||
8b712842 | 165 | spin_lock_irq(&worker->lock); |
35d8ba66 | 166 | check_idle_worker(worker); |
4a69a410 | 167 | |
8b712842 | 168 | } |
8b712842 | 169 | if (freezing(current)) { |
b51912c9 CM |
170 | worker->working = 0; |
171 | spin_unlock_irq(&worker->lock); | |
8b712842 CM |
172 | refrigerator(); |
173 | } else { | |
8b712842 | 174 | spin_unlock_irq(&worker->lock); |
b51912c9 CM |
175 | if (!kthread_should_stop()) { |
176 | cpu_relax(); | |
177 | /* | |
178 | * we've dropped the lock, did someone else | |
179 | * jump_in? | |
180 | */ | |
181 | smp_mb(); | |
182 | if (!list_empty(&worker->pending)) | |
183 | continue; | |
184 | ||
185 | /* | |
186 | * this short schedule allows more work to | |
187 | * come in without the queue functions | |
188 | * needing to go through wake_up_process() | |
189 | * | |
190 | * worker->working is still 1, so nobody | |
191 | * is going to try and wake us up | |
192 | */ | |
193 | schedule_timeout(1); | |
194 | smp_mb(); | |
195 | if (!list_empty(&worker->pending)) | |
196 | continue; | |
197 | ||
198 | /* still no more work?, sleep for real */ | |
199 | spin_lock_irq(&worker->lock); | |
200 | set_current_state(TASK_INTERRUPTIBLE); | |
201 | if (!list_empty(&worker->pending)) | |
202 | goto again_locked; | |
203 | ||
204 | /* | |
205 | * this makes sure we get a wakeup when someone | |
206 | * adds something new to the queue | |
207 | */ | |
208 | worker->working = 0; | |
209 | spin_unlock_irq(&worker->lock); | |
210 | ||
0df49b91 | 211 | schedule(); |
b51912c9 | 212 | } |
8b712842 CM |
213 | __set_current_state(TASK_RUNNING); |
214 | } | |
215 | } while (!kthread_should_stop()); | |
216 | return 0; | |
217 | } | |
218 | ||
219 | /* | |
220 | * this will wait for all the worker threads to shutdown | |
221 | */ | |
222 | int btrfs_stop_workers(struct btrfs_workers *workers) | |
223 | { | |
224 | struct list_head *cur; | |
225 | struct btrfs_worker_thread *worker; | |
226 | ||
35d8ba66 | 227 | list_splice_init(&workers->idle_list, &workers->worker_list); |
d397712b | 228 | while (!list_empty(&workers->worker_list)) { |
8b712842 CM |
229 | cur = workers->worker_list.next; |
230 | worker = list_entry(cur, struct btrfs_worker_thread, | |
231 | worker_list); | |
232 | kthread_stop(worker->task); | |
233 | list_del(&worker->worker_list); | |
234 | kfree(worker); | |
235 | } | |
236 | return 0; | |
237 | } | |
238 | ||
239 | /* | |
240 | * simple init on struct btrfs_workers | |
241 | */ | |
5443be45 | 242 | void btrfs_init_workers(struct btrfs_workers *workers, char *name, int max) |
8b712842 CM |
243 | { |
244 | workers->num_workers = 0; | |
245 | INIT_LIST_HEAD(&workers->worker_list); | |
35d8ba66 | 246 | INIT_LIST_HEAD(&workers->idle_list); |
4a69a410 | 247 | INIT_LIST_HEAD(&workers->order_list); |
8b712842 CM |
248 | spin_lock_init(&workers->lock); |
249 | workers->max_workers = max; | |
61b49440 | 250 | workers->idle_thresh = 32; |
5443be45 | 251 | workers->name = name; |
4a69a410 | 252 | workers->ordered = 0; |
8b712842 CM |
253 | } |
254 | ||
255 | /* | |
256 | * starts new worker threads. This does not enforce the max worker | |
257 | * count in case you need to temporarily go past it. | |
258 | */ | |
259 | int btrfs_start_workers(struct btrfs_workers *workers, int num_workers) | |
260 | { | |
261 | struct btrfs_worker_thread *worker; | |
262 | int ret = 0; | |
263 | int i; | |
264 | ||
265 | for (i = 0; i < num_workers; i++) { | |
266 | worker = kzalloc(sizeof(*worker), GFP_NOFS); | |
267 | if (!worker) { | |
268 | ret = -ENOMEM; | |
269 | goto fail; | |
270 | } | |
271 | ||
272 | INIT_LIST_HEAD(&worker->pending); | |
273 | INIT_LIST_HEAD(&worker->worker_list); | |
274 | spin_lock_init(&worker->lock); | |
275 | atomic_set(&worker->num_pending, 0); | |
5443be45 CM |
276 | worker->task = kthread_run(worker_loop, worker, |
277 | "btrfs-%s-%d", workers->name, | |
278 | workers->num_workers + i); | |
35d8ba66 | 279 | worker->workers = workers; |
8b712842 | 280 | if (IS_ERR(worker->task)) { |
3bf10418 | 281 | kfree(worker); |
8b712842 CM |
282 | ret = PTR_ERR(worker->task); |
283 | goto fail; | |
284 | } | |
285 | ||
286 | spin_lock_irq(&workers->lock); | |
35d8ba66 | 287 | list_add_tail(&worker->worker_list, &workers->idle_list); |
4854ddd0 | 288 | worker->idle = 1; |
8b712842 CM |
289 | workers->num_workers++; |
290 | spin_unlock_irq(&workers->lock); | |
291 | } | |
292 | return 0; | |
293 | fail: | |
294 | btrfs_stop_workers(workers); | |
295 | return ret; | |
296 | } | |
297 | ||
298 | /* | |
299 | * run through the list and find a worker thread that doesn't have a lot | |
300 | * to do right now. This can return null if we aren't yet at the thread | |
301 | * count limit and all of the threads are busy. | |
302 | */ | |
303 | static struct btrfs_worker_thread *next_worker(struct btrfs_workers *workers) | |
304 | { | |
305 | struct btrfs_worker_thread *worker; | |
306 | struct list_head *next; | |
8b712842 CM |
307 | int enforce_min = workers->num_workers < workers->max_workers; |
308 | ||
8b712842 | 309 | /* |
35d8ba66 CM |
310 | * if we find an idle thread, don't move it to the end of the |
311 | * idle list. This improves the chance that the next submission | |
312 | * will reuse the same thread, and maybe catch it while it is still | |
313 | * working | |
8b712842 | 314 | */ |
35d8ba66 CM |
315 | if (!list_empty(&workers->idle_list)) { |
316 | next = workers->idle_list.next; | |
8b712842 CM |
317 | worker = list_entry(next, struct btrfs_worker_thread, |
318 | worker_list); | |
35d8ba66 | 319 | return worker; |
8b712842 | 320 | } |
35d8ba66 CM |
321 | if (enforce_min || list_empty(&workers->worker_list)) |
322 | return NULL; | |
323 | ||
8b712842 | 324 | /* |
35d8ba66 | 325 | * if we pick a busy task, move the task to the end of the list. |
d352ac68 CM |
326 | * hopefully this will keep things somewhat evenly balanced. |
327 | * Do the move in batches based on the sequence number. This groups | |
328 | * requests submitted at roughly the same time onto the same worker. | |
8b712842 | 329 | */ |
35d8ba66 CM |
330 | next = workers->worker_list.next; |
331 | worker = list_entry(next, struct btrfs_worker_thread, worker_list); | |
4854ddd0 CM |
332 | atomic_inc(&worker->num_pending); |
333 | worker->sequence++; | |
d352ac68 | 334 | |
53863232 | 335 | if (worker->sequence % workers->idle_thresh == 0) |
4854ddd0 | 336 | list_move_tail(next, &workers->worker_list); |
8b712842 CM |
337 | return worker; |
338 | } | |
339 | ||
d352ac68 CM |
340 | /* |
341 | * selects a worker thread to take the next job. This will either find | |
342 | * an idle worker, start a new worker up to the max count, or just return | |
343 | * one of the existing busy workers. | |
344 | */ | |
8b712842 CM |
345 | static struct btrfs_worker_thread *find_worker(struct btrfs_workers *workers) |
346 | { | |
347 | struct btrfs_worker_thread *worker; | |
348 | unsigned long flags; | |
349 | ||
350 | again: | |
351 | spin_lock_irqsave(&workers->lock, flags); | |
352 | worker = next_worker(workers); | |
353 | spin_unlock_irqrestore(&workers->lock, flags); | |
354 | ||
355 | if (!worker) { | |
356 | spin_lock_irqsave(&workers->lock, flags); | |
357 | if (workers->num_workers >= workers->max_workers) { | |
35d8ba66 | 358 | struct list_head *fallback = NULL; |
8b712842 CM |
359 | /* |
360 | * we have failed to find any workers, just | |
361 | * return the force one | |
362 | */ | |
35d8ba66 CM |
363 | if (!list_empty(&workers->worker_list)) |
364 | fallback = workers->worker_list.next; | |
365 | if (!list_empty(&workers->idle_list)) | |
366 | fallback = workers->idle_list.next; | |
367 | BUG_ON(!fallback); | |
368 | worker = list_entry(fallback, | |
8b712842 CM |
369 | struct btrfs_worker_thread, worker_list); |
370 | spin_unlock_irqrestore(&workers->lock, flags); | |
371 | } else { | |
372 | spin_unlock_irqrestore(&workers->lock, flags); | |
373 | /* we're below the limit, start another worker */ | |
374 | btrfs_start_workers(workers, 1); | |
375 | goto again; | |
376 | } | |
377 | } | |
378 | return worker; | |
379 | } | |
380 | ||
381 | /* | |
382 | * btrfs_requeue_work just puts the work item back on the tail of the list | |
383 | * it was taken from. It is intended for use with long running work functions | |
384 | * that make some progress and want to give the cpu up for others. | |
385 | */ | |
386 | int btrfs_requeue_work(struct btrfs_work *work) | |
387 | { | |
388 | struct btrfs_worker_thread *worker = work->worker; | |
389 | unsigned long flags; | |
a6837051 | 390 | int wake = 0; |
8b712842 | 391 | |
4a69a410 | 392 | if (test_and_set_bit(WORK_QUEUED_BIT, &work->flags)) |
8b712842 CM |
393 | goto out; |
394 | ||
395 | spin_lock_irqsave(&worker->lock, flags); | |
8b712842 | 396 | list_add_tail(&work->list, &worker->pending); |
b51912c9 | 397 | atomic_inc(&worker->num_pending); |
75ccf47d CM |
398 | |
399 | /* by definition we're busy, take ourselves off the idle | |
400 | * list | |
401 | */ | |
402 | if (worker->idle) { | |
403 | spin_lock_irqsave(&worker->workers->lock, flags); | |
404 | worker->idle = 0; | |
405 | list_move_tail(&worker->worker_list, | |
406 | &worker->workers->worker_list); | |
407 | spin_unlock_irqrestore(&worker->workers->lock, flags); | |
408 | } | |
a6837051 CM |
409 | if (!worker->working) { |
410 | wake = 1; | |
411 | worker->working = 1; | |
412 | } | |
75ccf47d | 413 | |
8b712842 | 414 | spin_unlock_irqrestore(&worker->lock, flags); |
a6837051 CM |
415 | if (wake) |
416 | wake_up_process(worker->task); | |
8b712842 | 417 | out: |
a6837051 | 418 | |
8b712842 CM |
419 | return 0; |
420 | } | |
421 | ||
422 | /* | |
423 | * places a struct btrfs_work into the pending queue of one of the kthreads | |
424 | */ | |
425 | int btrfs_queue_worker(struct btrfs_workers *workers, struct btrfs_work *work) | |
426 | { | |
427 | struct btrfs_worker_thread *worker; | |
428 | unsigned long flags; | |
429 | int wake = 0; | |
430 | ||
431 | /* don't requeue something already on a list */ | |
4a69a410 | 432 | if (test_and_set_bit(WORK_QUEUED_BIT, &work->flags)) |
8b712842 CM |
433 | goto out; |
434 | ||
435 | worker = find_worker(workers); | |
4a69a410 CM |
436 | if (workers->ordered) { |
437 | spin_lock_irqsave(&workers->lock, flags); | |
438 | list_add_tail(&work->order_list, &workers->order_list); | |
439 | spin_unlock_irqrestore(&workers->lock, flags); | |
440 | } else { | |
441 | INIT_LIST_HEAD(&work->order_list); | |
442 | } | |
8b712842 CM |
443 | |
444 | spin_lock_irqsave(&worker->lock, flags); | |
a6837051 | 445 | |
b51912c9 | 446 | list_add_tail(&work->list, &worker->pending); |
8b712842 | 447 | atomic_inc(&worker->num_pending); |
35d8ba66 | 448 | check_busy_worker(worker); |
8b712842 CM |
449 | |
450 | /* | |
451 | * avoid calling into wake_up_process if this thread has already | |
452 | * been kicked | |
453 | */ | |
454 | if (!worker->working) | |
455 | wake = 1; | |
456 | worker->working = 1; | |
457 | ||
458 | spin_unlock_irqrestore(&worker->lock, flags); | |
459 | ||
460 | if (wake) | |
461 | wake_up_process(worker->task); | |
462 | out: | |
463 | return 0; | |
464 | } |