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 15 enum { 16 WORK_DONE_BIT, 17 WORK_ORDER_DONE_BIT, 18 WORK_HIGH_PRIO_BIT, 19 }; 20 21 #define NO_THRESHOLD (-1) 22 #define DFT_THRESHOLD (32) 23 24 struct __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 51 struct btrfs_workqueue { 52 struct __btrfs_workqueue *normal; 53 struct __btrfs_workqueue *high; 54 }; 55 56 struct btrfs_fs_info * 57 btrfs_workqueue_owner(const struct __btrfs_workqueue *wq) 58 { 59 return wq->fs_info; 60 } 61 62 struct btrfs_fs_info * 63 btrfs_work_owner(const struct btrfs_work *work) 64 { 65 return work->wq->fs_info; 66 } 67 68 bool btrfs_workqueue_normal_congested(const struct btrfs_workqueue *wq) 69 { 70 /* 71 * We could compare wq->normal->pending with num_online_cpus() 72 * to support "thresh == NO_THRESHOLD" case, but it requires 73 * moving up atomic_inc/dec in thresh_queue/exec_hook. Let's 74 * postpone it until someone needs the support of that case. 75 */ 76 if (wq->normal->thresh == NO_THRESHOLD) 77 return false; 78 79 return atomic_read(&wq->normal->pending) > wq->normal->thresh * 2; 80 } 81 82 static struct __btrfs_workqueue * 83 __btrfs_alloc_workqueue(struct btrfs_fs_info *fs_info, const char *name, 84 unsigned int flags, int limit_active, int thresh) 85 { 86 struct __btrfs_workqueue *ret = kzalloc(sizeof(*ret), GFP_KERNEL); 87 88 if (!ret) 89 return NULL; 90 91 ret->fs_info = fs_info; 92 ret->limit_active = limit_active; 93 atomic_set(&ret->pending, 0); 94 if (thresh == 0) 95 thresh = DFT_THRESHOLD; 96 /* For low threshold, disabling threshold is a better choice */ 97 if (thresh < DFT_THRESHOLD) { 98 ret->current_active = limit_active; 99 ret->thresh = NO_THRESHOLD; 100 } else { 101 /* 102 * For threshold-able wq, let its concurrency grow on demand. 103 * Use minimal max_active at alloc time to reduce resource 104 * usage. 105 */ 106 ret->current_active = 1; 107 ret->thresh = thresh; 108 } 109 110 if (flags & WQ_HIGHPRI) 111 ret->normal_wq = alloc_workqueue("btrfs-%s-high", flags, 112 ret->current_active, name); 113 else 114 ret->normal_wq = alloc_workqueue("btrfs-%s", flags, 115 ret->current_active, name); 116 if (!ret->normal_wq) { 117 kfree(ret); 118 return NULL; 119 } 120 121 INIT_LIST_HEAD(&ret->ordered_list); 122 spin_lock_init(&ret->list_lock); 123 spin_lock_init(&ret->thres_lock); 124 trace_btrfs_workqueue_alloc(ret, name, flags & WQ_HIGHPRI); 125 return ret; 126 } 127 128 static inline void 129 __btrfs_destroy_workqueue(struct __btrfs_workqueue *wq); 130 131 struct btrfs_workqueue *btrfs_alloc_workqueue(struct btrfs_fs_info *fs_info, 132 const char *name, 133 unsigned int flags, 134 int limit_active, 135 int thresh) 136 { 137 struct btrfs_workqueue *ret = kzalloc(sizeof(*ret), GFP_KERNEL); 138 139 if (!ret) 140 return NULL; 141 142 ret->normal = __btrfs_alloc_workqueue(fs_info, name, 143 flags & ~WQ_HIGHPRI, 144 limit_active, thresh); 145 if (!ret->normal) { 146 kfree(ret); 147 return NULL; 148 } 149 150 if (flags & WQ_HIGHPRI) { 151 ret->high = __btrfs_alloc_workqueue(fs_info, name, flags, 152 limit_active, thresh); 153 if (!ret->high) { 154 __btrfs_destroy_workqueue(ret->normal); 155 kfree(ret); 156 return NULL; 157 } 158 } 159 return ret; 160 } 161 162 /* 163 * Hook for threshold which will be called in btrfs_queue_work. 164 * This hook WILL be called in IRQ handler context, 165 * so workqueue_set_max_active MUST NOT be called in this hook 166 */ 167 static inline void thresh_queue_hook(struct __btrfs_workqueue *wq) 168 { 169 if (wq->thresh == NO_THRESHOLD) 170 return; 171 atomic_inc(&wq->pending); 172 } 173 174 /* 175 * Hook for threshold which will be called before executing the work, 176 * This hook is called in kthread content. 177 * So workqueue_set_max_active is called here. 178 */ 179 static inline void thresh_exec_hook(struct __btrfs_workqueue *wq) 180 { 181 int new_current_active; 182 long pending; 183 int need_change = 0; 184 185 if (wq->thresh == NO_THRESHOLD) 186 return; 187 188 atomic_dec(&wq->pending); 189 spin_lock(&wq->thres_lock); 190 /* 191 * Use wq->count to limit the calling frequency of 192 * workqueue_set_max_active. 193 */ 194 wq->count++; 195 wq->count %= (wq->thresh / 4); 196 if (!wq->count) 197 goto out; 198 new_current_active = wq->current_active; 199 200 /* 201 * pending may be changed later, but it's OK since we really 202 * don't need it so accurate to calculate new_max_active. 203 */ 204 pending = atomic_read(&wq->pending); 205 if (pending > wq->thresh) 206 new_current_active++; 207 if (pending < wq->thresh / 2) 208 new_current_active--; 209 new_current_active = clamp_val(new_current_active, 1, wq->limit_active); 210 if (new_current_active != wq->current_active) { 211 need_change = 1; 212 wq->current_active = new_current_active; 213 } 214 out: 215 spin_unlock(&wq->thres_lock); 216 217 if (need_change) { 218 workqueue_set_max_active(wq->normal_wq, wq->current_active); 219 } 220 } 221 222 static void run_ordered_work(struct __btrfs_workqueue *wq, 223 struct btrfs_work *self) 224 { 225 struct list_head *list = &wq->ordered_list; 226 struct btrfs_work *work; 227 spinlock_t *lock = &wq->list_lock; 228 unsigned long flags; 229 void *wtag; 230 bool free_self = false; 231 232 while (1) { 233 spin_lock_irqsave(lock, flags); 234 if (list_empty(list)) 235 break; 236 work = list_entry(list->next, struct btrfs_work, 237 ordered_list); 238 if (!test_bit(WORK_DONE_BIT, &work->flags)) 239 break; 240 241 /* 242 * we are going to call the ordered done function, but 243 * we leave the work item on the list as a barrier so 244 * that later work items that are done don't have their 245 * functions called before this one returns 246 */ 247 if (test_and_set_bit(WORK_ORDER_DONE_BIT, &work->flags)) 248 break; 249 trace_btrfs_ordered_sched(work); 250 spin_unlock_irqrestore(lock, flags); 251 work->ordered_func(work); 252 253 /* now take the lock again and drop our item from the list */ 254 spin_lock_irqsave(lock, flags); 255 list_del(&work->ordered_list); 256 spin_unlock_irqrestore(lock, flags); 257 258 if (work == self) { 259 /* 260 * This is the work item that the worker is currently 261 * executing. 262 * 263 * The kernel workqueue code guarantees non-reentrancy 264 * of work items. I.e., if a work item with the same 265 * address and work function is queued twice, the second 266 * execution is blocked until the first one finishes. A 267 * work item may be freed and recycled with the same 268 * work function; the workqueue code assumes that the 269 * original work item cannot depend on the recycled work 270 * item in that case (see find_worker_executing_work()). 271 * 272 * Note that different types of Btrfs work can depend on 273 * each other, and one type of work on one Btrfs 274 * filesystem may even depend on the same type of work 275 * on another Btrfs filesystem via, e.g., a loop device. 276 * Therefore, we must not allow the current work item to 277 * be recycled until we are really done, otherwise we 278 * break the above assumption and can deadlock. 279 */ 280 free_self = true; 281 } else { 282 /* 283 * We don't want to call the ordered free functions with 284 * the lock held though. Save the work as tag for the 285 * trace event, because the callback could free the 286 * structure. 287 */ 288 wtag = work; 289 work->ordered_free(work); 290 trace_btrfs_all_work_done(wq->fs_info, wtag); 291 } 292 } 293 spin_unlock_irqrestore(lock, flags); 294 295 if (free_self) { 296 wtag = self; 297 self->ordered_free(self); 298 trace_btrfs_all_work_done(wq->fs_info, wtag); 299 } 300 } 301 302 static void btrfs_work_helper(struct work_struct *normal_work) 303 { 304 struct btrfs_work *work = container_of(normal_work, struct btrfs_work, 305 normal_work); 306 struct __btrfs_workqueue *wq; 307 void *wtag; 308 int need_order = 0; 309 310 /* 311 * We should not touch things inside work in the following cases: 312 * 1) after work->func() if it has no ordered_free 313 * Since the struct is freed in work->func(). 314 * 2) after setting WORK_DONE_BIT 315 * The work may be freed in other threads almost instantly. 316 * So we save the needed things here. 317 */ 318 if (work->ordered_func) 319 need_order = 1; 320 wq = work->wq; 321 /* Safe for tracepoints in case work gets freed by the callback */ 322 wtag = work; 323 324 trace_btrfs_work_sched(work); 325 thresh_exec_hook(wq); 326 work->func(work); 327 if (need_order) { 328 set_bit(WORK_DONE_BIT, &work->flags); 329 run_ordered_work(wq, work); 330 } 331 if (!need_order) 332 trace_btrfs_all_work_done(wq->fs_info, wtag); 333 } 334 335 void btrfs_init_work(struct btrfs_work *work, btrfs_func_t func, 336 btrfs_func_t ordered_func, btrfs_func_t ordered_free) 337 { 338 work->func = func; 339 work->ordered_func = ordered_func; 340 work->ordered_free = ordered_free; 341 INIT_WORK(&work->normal_work, btrfs_work_helper); 342 INIT_LIST_HEAD(&work->ordered_list); 343 work->flags = 0; 344 } 345 346 static inline void __btrfs_queue_work(struct __btrfs_workqueue *wq, 347 struct btrfs_work *work) 348 { 349 unsigned long flags; 350 351 work->wq = wq; 352 thresh_queue_hook(wq); 353 if (work->ordered_func) { 354 spin_lock_irqsave(&wq->list_lock, flags); 355 list_add_tail(&work->ordered_list, &wq->ordered_list); 356 spin_unlock_irqrestore(&wq->list_lock, flags); 357 } 358 trace_btrfs_work_queued(work); 359 queue_work(wq->normal_wq, &work->normal_work); 360 } 361 362 void btrfs_queue_work(struct btrfs_workqueue *wq, 363 struct btrfs_work *work) 364 { 365 struct __btrfs_workqueue *dest_wq; 366 367 if (test_bit(WORK_HIGH_PRIO_BIT, &work->flags) && wq->high) 368 dest_wq = wq->high; 369 else 370 dest_wq = wq->normal; 371 __btrfs_queue_work(dest_wq, work); 372 } 373 374 static inline void 375 __btrfs_destroy_workqueue(struct __btrfs_workqueue *wq) 376 { 377 destroy_workqueue(wq->normal_wq); 378 trace_btrfs_workqueue_destroy(wq); 379 kfree(wq); 380 } 381 382 void btrfs_destroy_workqueue(struct btrfs_workqueue *wq) 383 { 384 if (!wq) 385 return; 386 if (wq->high) 387 __btrfs_destroy_workqueue(wq->high); 388 __btrfs_destroy_workqueue(wq->normal); 389 kfree(wq); 390 } 391 392 void btrfs_workqueue_set_max(struct btrfs_workqueue *wq, int limit_active) 393 { 394 if (!wq) 395 return; 396 wq->normal->limit_active = limit_active; 397 if (wq->high) 398 wq->high->limit_active = limit_active; 399 } 400 401 void btrfs_set_work_high_priority(struct btrfs_work *work) 402 { 403 set_bit(WORK_HIGH_PRIO_BIT, &work->flags); 404 } 405