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1// SPDX-License-Identifier: GPL-2.02/*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 requires65 * moving up atomic_inc/dec in thresh_queue/exec_hook. Let's66 * 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 resource106 * 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 hook154 */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 of180 * 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 really190 * 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_helper230 * this guarantees that the ordered function will see all231 * updates from ordinary work function.232 */233 smp_rmb();234 235 /*236 * we are going to call the ordered done function, but237 * we leave the work item on the list as a barrier so238 * that later work items that are done don't have their239 * functions called before this one returns240 */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 currently255 * executing.256 *257 * The kernel workqueue code guarantees non-reentrancy258 * of work items. I.e., if a work item with the same259 * address and work function is queued twice, the second260 * execution is blocked until the first one finishes. A261 * work item may be freed and recycled with the same262 * work function; the workqueue code assumes that the263 * original work item cannot depend on the recycled work264 * item in that case (see find_worker_executing_work()).265 *266 * Note that different types of Btrfs work can depend on267 * each other, and one type of work on one Btrfs268 * filesystem may even depend on the same type of work269 * on another Btrfs filesystem via, e.g., a loop device.270 * Therefore, we must not allow the current work item to271 * be recycled until we are really done, otherwise we272 * 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 with278 * 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 free304 * Since the struct is freed in work->func().305 * 2) after setting WORK_DONE_BIT306 * 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 are318 * ordered before setting the WORK_DONE_BIT. Ensuring the thread319 * 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}375