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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 <trace/events/btrfs.h>
13#include "async-thread.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
74static 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(&wq->pending, 0);
79 INIT_LIST_HEAD(&wq->ordered_list);
80 spin_lock_init(&wq->list_lock);
81 spin_lock_init(&wq->thres_lock);
82}
83
84struct 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(sizeof(*ret), GFP_KERNEL);
89
90 if (!ret)
91 return NULL;
92
93 btrfs_init_workqueue(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("btrfs-%s", flags, ret->current_active,
113 name);
114 if (!ret->normal_wq) {
115 kfree(ret);
116 return NULL;
117 }
118
119 trace_btrfs_workqueue_alloc(ret, name);
120 return ret;
121}
122
123struct 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(sizeof(*ret), GFP_KERNEL);
130 if (!ret)
131 return NULL;
132
133 btrfs_init_workqueue(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(ret);
143 return NULL;
144 }
145
146 trace_btrfs_workqueue_alloc(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 */
155static inline void thresh_queue_hook(struct btrfs_workqueue *wq)
156{
157 if (wq->thresh == NO_THRESHOLD)
158 return;
159 atomic_inc(&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 */
167static 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(&wq->pending);
177 spin_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(&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 }
202out:
203 spin_unlock(&wq->thres_lock);
204
205 if (need_change) {
206 workqueue_set_max_active(wq->normal_wq, wq->current_active);
207 }
208}
209
210static 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(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(WORK_ORDER_DONE_BIT, &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(&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(wq->fs_info, 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(wq->fs_info, self);
291 }
292}
293
294static 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(WORK_DONE_BIT, &work->flags);
324 run_ordered_work(wq, work);
325 } else {
326 /* NB: work must not be dereferenced past this point. */
327 trace_btrfs_all_work_done(wq->fs_info, work);
328 }
329}
330
331void 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(&work->ordered_list);
338 work->flags = 0;
339}
340
341void 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(&work->ordered_list, &wq->ordered_list);
350 spin_unlock_irqrestore(&wq->list_lock, flags);
351 }
352 trace_btrfs_work_queued(work);
353 queue_work(wq->normal_wq, &work->normal_work);
354}
355
356void btrfs_destroy_workqueue(struct btrfs_workqueue *wq)
357{
358 if (!wq)
359 return;
360 destroy_workqueue(wq->normal_wq);
361 trace_btrfs_workqueue_destroy(wq);
362 kfree(wq);
363}
364
365void btrfs_workqueue_set_max(struct btrfs_workqueue *wq, int limit_active)
366{
367 if (wq)
368 wq->limit_active = limit_active;
369}
370
371void btrfs_flush_workqueue(struct btrfs_workqueue *wq)
372{
373 flush_workqueue(wq->normal_wq);
374}