1 | // SPDX-License-Identifier: GPL-2.0 |
2 | /* |
3 | * Copyright (C) 2007 Oracle. All rights reserved. |
4 | * Copyright (C) 2014 Fujitsu. All rights reserved. |
5 | */ |
6 | |
7 | #include <linux/kthread.h> |
8 | #include <linux/slab.h> |
9 | #include <linux/list.h> |
10 | #include <linux/spinlock.h> |
11 | #include <linux/freezer.h> |
12 | #include <trace/events/btrfs.h> |
13 | #include "async-thread.h" |
14 | |
15 | enum { |
16 | WORK_DONE_BIT, |
17 | WORK_ORDER_DONE_BIT, |
18 | }; |
19 | |
20 | #define NO_THRESHOLD (-1) |
21 | #define DFT_THRESHOLD (32) |
22 | |
23 | struct btrfs_workqueue { |
24 | struct workqueue_struct *normal_wq; |
25 | |
26 | /* File system this workqueue services */ |
27 | struct btrfs_fs_info *fs_info; |
28 | |
29 | /* List head pointing to ordered work list */ |
30 | struct list_head ordered_list; |
31 | |
32 | /* Spinlock for ordered_list */ |
33 | spinlock_t list_lock; |
34 | |
35 | /* Thresholding related variants */ |
36 | atomic_t pending; |
37 | |
38 | /* Up limit of concurrency workers */ |
39 | int limit_active; |
40 | |
41 | /* Current number of concurrency workers */ |
42 | int current_active; |
43 | |
44 | /* Threshold to change current_active */ |
45 | int thresh; |
46 | unsigned int count; |
47 | spinlock_t thres_lock; |
48 | }; |
49 | |
50 | struct btrfs_fs_info * __pure btrfs_workqueue_owner(const struct btrfs_workqueue *wq) |
51 | { |
52 | return wq->fs_info; |
53 | } |
54 | |
55 | struct btrfs_fs_info * __pure btrfs_work_owner(const struct btrfs_work *work) |
56 | { |
57 | return work->wq->fs_info; |
58 | } |
59 | |
60 | bool btrfs_workqueue_normal_congested(const struct btrfs_workqueue *wq) |
61 | { |
62 | /* |
63 | * We could compare wq->pending with num_online_cpus() |
64 | * to support "thresh == NO_THRESHOLD" case, but it requires |
65 | * moving up atomic_inc/dec in thresh_queue/exec_hook. Let's |
66 | * postpone it until someone needs the support of that case. |
67 | */ |
68 | if (wq->thresh == NO_THRESHOLD) |
69 | return false; |
70 | |
71 | return atomic_read(v: &wq->pending) > wq->thresh * 2; |
72 | } |
73 | |
74 | static void btrfs_init_workqueue(struct btrfs_workqueue *wq, |
75 | struct btrfs_fs_info *fs_info) |
76 | { |
77 | wq->fs_info = fs_info; |
78 | atomic_set(v: &wq->pending, i: 0); |
79 | INIT_LIST_HEAD(list: &wq->ordered_list); |
80 | spin_lock_init(&wq->list_lock); |
81 | spin_lock_init(&wq->thres_lock); |
82 | } |
83 | |
84 | struct btrfs_workqueue *btrfs_alloc_workqueue(struct btrfs_fs_info *fs_info, |
85 | const char *name, unsigned int flags, |
86 | int limit_active, int thresh) |
87 | { |
88 | struct btrfs_workqueue *ret = kzalloc(size: sizeof(*ret), GFP_KERNEL); |
89 | |
90 | if (!ret) |
91 | return NULL; |
92 | |
93 | btrfs_init_workqueue(wq: ret, fs_info); |
94 | |
95 | ret->limit_active = limit_active; |
96 | if (thresh == 0) |
97 | thresh = DFT_THRESHOLD; |
98 | /* For low threshold, disabling threshold is a better choice */ |
99 | if (thresh < DFT_THRESHOLD) { |
100 | ret->current_active = limit_active; |
101 | ret->thresh = NO_THRESHOLD; |
102 | } else { |
103 | /* |
104 | * For threshold-able wq, let its concurrency grow on demand. |
105 | * Use minimal max_active at alloc time to reduce resource |
106 | * usage. |
107 | */ |
108 | ret->current_active = 1; |
109 | ret->thresh = thresh; |
110 | } |
111 | |
112 | ret->normal_wq = alloc_workqueue(fmt: "btrfs-%s" , flags, max_active: ret->current_active, |
113 | name); |
114 | if (!ret->normal_wq) { |
115 | kfree(objp: ret); |
116 | return NULL; |
117 | } |
118 | |
119 | trace_btrfs_workqueue_alloc(wq: ret, name); |
120 | return ret; |
121 | } |
122 | |
123 | struct btrfs_workqueue *btrfs_alloc_ordered_workqueue( |
124 | struct btrfs_fs_info *fs_info, const char *name, |
125 | unsigned int flags) |
126 | { |
127 | struct btrfs_workqueue *ret; |
128 | |
129 | ret = kzalloc(size: sizeof(*ret), GFP_KERNEL); |
130 | if (!ret) |
131 | return NULL; |
132 | |
133 | btrfs_init_workqueue(wq: ret, fs_info); |
134 | |
135 | /* Ordered workqueues don't allow @max_active adjustments. */ |
136 | ret->limit_active = 1; |
137 | ret->current_active = 1; |
138 | ret->thresh = NO_THRESHOLD; |
139 | |
140 | ret->normal_wq = alloc_ordered_workqueue("btrfs-%s" , flags, name); |
141 | if (!ret->normal_wq) { |
142 | kfree(objp: ret); |
143 | return NULL; |
144 | } |
145 | |
146 | trace_btrfs_workqueue_alloc(wq: ret, name); |
147 | return ret; |
148 | } |
149 | |
150 | /* |
151 | * Hook for threshold which will be called in btrfs_queue_work. |
152 | * This hook WILL be called in IRQ handler context, |
153 | * so workqueue_set_max_active MUST NOT be called in this hook |
154 | */ |
155 | static inline void thresh_queue_hook(struct btrfs_workqueue *wq) |
156 | { |
157 | if (wq->thresh == NO_THRESHOLD) |
158 | return; |
159 | atomic_inc(v: &wq->pending); |
160 | } |
161 | |
162 | /* |
163 | * Hook for threshold which will be called before executing the work, |
164 | * This hook is called in kthread content. |
165 | * So workqueue_set_max_active is called here. |
166 | */ |
167 | static inline void thresh_exec_hook(struct btrfs_workqueue *wq) |
168 | { |
169 | int new_current_active; |
170 | long pending; |
171 | int need_change = 0; |
172 | |
173 | if (wq->thresh == NO_THRESHOLD) |
174 | return; |
175 | |
176 | atomic_dec(v: &wq->pending); |
177 | spin_lock(lock: &wq->thres_lock); |
178 | /* |
179 | * Use wq->count to limit the calling frequency of |
180 | * workqueue_set_max_active. |
181 | */ |
182 | wq->count++; |
183 | wq->count %= (wq->thresh / 4); |
184 | if (!wq->count) |
185 | goto out; |
186 | new_current_active = wq->current_active; |
187 | |
188 | /* |
189 | * pending may be changed later, but it's OK since we really |
190 | * don't need it so accurate to calculate new_max_active. |
191 | */ |
192 | pending = atomic_read(v: &wq->pending); |
193 | if (pending > wq->thresh) |
194 | new_current_active++; |
195 | if (pending < wq->thresh / 2) |
196 | new_current_active--; |
197 | new_current_active = clamp_val(new_current_active, 1, wq->limit_active); |
198 | if (new_current_active != wq->current_active) { |
199 | need_change = 1; |
200 | wq->current_active = new_current_active; |
201 | } |
202 | out: |
203 | spin_unlock(lock: &wq->thres_lock); |
204 | |
205 | if (need_change) { |
206 | workqueue_set_max_active(wq: wq->normal_wq, max_active: wq->current_active); |
207 | } |
208 | } |
209 | |
210 | static void run_ordered_work(struct btrfs_workqueue *wq, |
211 | struct btrfs_work *self) |
212 | { |
213 | struct list_head *list = &wq->ordered_list; |
214 | struct btrfs_work *work; |
215 | spinlock_t *lock = &wq->list_lock; |
216 | unsigned long flags; |
217 | bool free_self = false; |
218 | |
219 | while (1) { |
220 | spin_lock_irqsave(lock, flags); |
221 | if (list_empty(head: list)) |
222 | break; |
223 | work = list_entry(list->next, struct btrfs_work, |
224 | ordered_list); |
225 | if (!test_bit(WORK_DONE_BIT, &work->flags)) |
226 | break; |
227 | /* |
228 | * Orders all subsequent loads after reading WORK_DONE_BIT, |
229 | * paired with the smp_mb__before_atomic in btrfs_work_helper |
230 | * this guarantees that the ordered function will see all |
231 | * updates from ordinary work function. |
232 | */ |
233 | smp_rmb(); |
234 | |
235 | /* |
236 | * we are going to call the ordered done function, but |
237 | * we leave the work item on the list as a barrier so |
238 | * that later work items that are done don't have their |
239 | * functions called before this one returns |
240 | */ |
241 | if (test_and_set_bit(nr: WORK_ORDER_DONE_BIT, addr: &work->flags)) |
242 | break; |
243 | trace_btrfs_ordered_sched(work); |
244 | spin_unlock_irqrestore(lock, flags); |
245 | work->ordered_func(work, false); |
246 | |
247 | /* now take the lock again and drop our item from the list */ |
248 | spin_lock_irqsave(lock, flags); |
249 | list_del(entry: &work->ordered_list); |
250 | spin_unlock_irqrestore(lock, flags); |
251 | |
252 | if (work == self) { |
253 | /* |
254 | * This is the work item that the worker is currently |
255 | * executing. |
256 | * |
257 | * The kernel workqueue code guarantees non-reentrancy |
258 | * of work items. I.e., if a work item with the same |
259 | * address and work function is queued twice, the second |
260 | * execution is blocked until the first one finishes. A |
261 | * work item may be freed and recycled with the same |
262 | * work function; the workqueue code assumes that the |
263 | * original work item cannot depend on the recycled work |
264 | * item in that case (see find_worker_executing_work()). |
265 | * |
266 | * Note that different types of Btrfs work can depend on |
267 | * each other, and one type of work on one Btrfs |
268 | * filesystem may even depend on the same type of work |
269 | * on another Btrfs filesystem via, e.g., a loop device. |
270 | * Therefore, we must not allow the current work item to |
271 | * be recycled until we are really done, otherwise we |
272 | * break the above assumption and can deadlock. |
273 | */ |
274 | free_self = true; |
275 | } else { |
276 | /* |
277 | * We don't want to call the ordered free functions with |
278 | * the lock held. |
279 | */ |
280 | work->ordered_func(work, true); |
281 | /* NB: work must not be dereferenced past this point. */ |
282 | trace_btrfs_all_work_done(fs_info: wq->fs_info, wtag: work); |
283 | } |
284 | } |
285 | spin_unlock_irqrestore(lock, flags); |
286 | |
287 | if (free_self) { |
288 | self->ordered_func(self, true); |
289 | /* NB: self must not be dereferenced past this point. */ |
290 | trace_btrfs_all_work_done(fs_info: wq->fs_info, wtag: self); |
291 | } |
292 | } |
293 | |
294 | static void btrfs_work_helper(struct work_struct *normal_work) |
295 | { |
296 | struct btrfs_work *work = container_of(normal_work, struct btrfs_work, |
297 | normal_work); |
298 | struct btrfs_workqueue *wq = work->wq; |
299 | int need_order = 0; |
300 | |
301 | /* |
302 | * We should not touch things inside work in the following cases: |
303 | * 1) after work->func() if it has no ordered_func(..., true) to free |
304 | * Since the struct is freed in work->func(). |
305 | * 2) after setting WORK_DONE_BIT |
306 | * The work may be freed in other threads almost instantly. |
307 | * So we save the needed things here. |
308 | */ |
309 | if (work->ordered_func) |
310 | need_order = 1; |
311 | |
312 | trace_btrfs_work_sched(work); |
313 | thresh_exec_hook(wq); |
314 | work->func(work); |
315 | if (need_order) { |
316 | /* |
317 | * Ensures all memory accesses done in the work function are |
318 | * ordered before setting the WORK_DONE_BIT. Ensuring the thread |
319 | * which is going to executed the ordered work sees them. |
320 | * Pairs with the smp_rmb in run_ordered_work. |
321 | */ |
322 | smp_mb__before_atomic(); |
323 | set_bit(nr: WORK_DONE_BIT, addr: &work->flags); |
324 | run_ordered_work(wq, self: work); |
325 | } else { |
326 | /* NB: work must not be dereferenced past this point. */ |
327 | trace_btrfs_all_work_done(fs_info: wq->fs_info, wtag: work); |
328 | } |
329 | } |
330 | |
331 | void btrfs_init_work(struct btrfs_work *work, btrfs_func_t func, |
332 | btrfs_ordered_func_t ordered_func) |
333 | { |
334 | work->func = func; |
335 | work->ordered_func = ordered_func; |
336 | INIT_WORK(&work->normal_work, btrfs_work_helper); |
337 | INIT_LIST_HEAD(list: &work->ordered_list); |
338 | work->flags = 0; |
339 | } |
340 | |
341 | void btrfs_queue_work(struct btrfs_workqueue *wq, struct btrfs_work *work) |
342 | { |
343 | unsigned long flags; |
344 | |
345 | work->wq = wq; |
346 | thresh_queue_hook(wq); |
347 | if (work->ordered_func) { |
348 | spin_lock_irqsave(&wq->list_lock, flags); |
349 | list_add_tail(new: &work->ordered_list, head: &wq->ordered_list); |
350 | spin_unlock_irqrestore(lock: &wq->list_lock, flags); |
351 | } |
352 | trace_btrfs_work_queued(work); |
353 | queue_work(wq: wq->normal_wq, work: &work->normal_work); |
354 | } |
355 | |
356 | void btrfs_destroy_workqueue(struct btrfs_workqueue *wq) |
357 | { |
358 | if (!wq) |
359 | return; |
360 | destroy_workqueue(wq: wq->normal_wq); |
361 | trace_btrfs_workqueue_destroy(wq); |
362 | kfree(objp: wq); |
363 | } |
364 | |
365 | void btrfs_workqueue_set_max(struct btrfs_workqueue *wq, int limit_active) |
366 | { |
367 | if (wq) |
368 | wq->limit_active = limit_active; |
369 | } |
370 | |
371 | void btrfs_flush_workqueue(struct btrfs_workqueue *wq) |
372 | { |
373 | flush_workqueue(wq->normal_wq); |
374 | } |
375 | |