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