fs/btrfs/async-thread.c

   1 /*
   2  * Copyright (C) 2007 Oracle.  All rights reserved.
   3  * Copyright (C) 2014 Fujitsu.  All rights reserved.
   4  *
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU General Public
   7  * License v2 as published by the Free Software Foundation.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public
  15  * License along with this program; if not, write to the
  16  * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  17  * Boston, MA 021110-1307, USA.
  18  */
  19
  20 #include <linux/kthread.h>
  21 #include <linux/slab.h>
  22 #include <linux/list.h>
  23 #include <linux/spinlock.h>
  24 #include <linux/freezer.h>
  25 #include <linux/workqueue.h>
  26 #include "async-thread.h"
  27
  28 #define WORK_DONE_BIT 0
  29 #define WORK_ORDER_DONE_BIT 1
  30 #define WORK_HIGH_PRIO_BIT 2
  31
  32 #define NO_THRESHOLD (-1)
  33 #define DFT_THRESHOLD (32)
  34
  35 struct __btrfs_workqueue {
  36         struct workqueue_struct *normal_wq;
  37         /* List head pointing to ordered work list */
  38         struct list_head ordered_list;
  39
  40         /* Spinlock for ordered_list */
  41         spinlock_t list_lock;
  42
  43         /* Thresholding related variants */
  44         atomic_t pending;
  45         int max_active;
  46         int current_max;
  47         int thresh;
  48         unsigned int count;
  49         spinlock_t thres_lock;
  50 };
  51
  52 struct btrfs_workqueue {
  53         struct __btrfs_workqueue *normal;
  54         struct __btrfs_workqueue *high;
  55 };
  56
  57 static inline struct __btrfs_workqueue
  58 *__btrfs_alloc_workqueue(char *name, int flags, int max_active, int thresh)
  59 {
  60         struct __btrfs_workqueue *ret = kzalloc(sizeof(*ret), GFP_NOFS);
  61
  62         if (unlikely(!ret))
  63                 return NULL;
  64
  65         ret->max_active = max_active;
  66         atomic_set(&ret->pending, 0);
  67         if (thresh == 0)
  68                 thresh = DFT_THRESHOLD;
  69         /* For low threshold, disabling threshold is a better choice */
  70         if (thresh < DFT_THRESHOLD) {
  71                 ret->current_max = max_active;
  72                 ret->thresh = NO_THRESHOLD;
  73         } else {
  74                 ret->current_max = 1;
  75                 ret->thresh = thresh;
  76         }
  77
  78         if (flags & WQ_HIGHPRI)
  79                 ret->normal_wq = alloc_workqueue("%s-%s-high", flags,
  80                                                  ret->max_active,
  81                                                  "btrfs", name);
  82         else
  83                 ret->normal_wq = alloc_workqueue("%s-%s", flags,
  84                                                  ret->max_active, "btrfs",
  85                                                  name);
  86         if (unlikely(!ret->normal_wq)) {
  87                 kfree(ret);
  88                 return NULL;
  89         }
  90
  91         INIT_LIST_HEAD(&ret->ordered_list);
  92         spin_lock_init(&ret->list_lock);
  93         spin_lock_init(&ret->thres_lock);
  94         return ret;
  95 }
  96
  97 static inline void
  98 __btrfs_destroy_workqueue(struct __btrfs_workqueue *wq);
  99
 100 struct btrfs_workqueue *btrfs_alloc_workqueue(char *name,
 101                                               int flags,
 102                                               int max_active,
 103                                               int thresh)
 104 {
 105         struct btrfs_workqueue *ret = kzalloc(sizeof(*ret), GFP_NOFS);
 106
 107         if (unlikely(!ret))
 108                 return NULL;
 109
 110         ret->normal = __btrfs_alloc_workqueue(name, flags & ~WQ_HIGHPRI,
 111                                               max_active, thresh);
 112         if (unlikely(!ret->normal)) {
 113                 kfree(ret);
 114                 return NULL;
 115         }
 116
 117         if (flags & WQ_HIGHPRI) {
 118                 ret->high = __btrfs_alloc_workqueue(name, flags, max_active,
 119                                                     thresh);
 120                 if (unlikely(!ret->high)) {
 121                         __btrfs_destroy_workqueue(ret->normal);
 122                         kfree(ret);
 123                         return NULL;
 124                 }
 125         }
 126         return ret;
 127 }
 128
 129 /*
 130  * Hook for threshold which will be called in btrfs_queue_work.
 131  * This hook WILL be called in IRQ handler context,
 132  * so workqueue_set_max_active MUST NOT be called in this hook
 133  */
 134 static inline void thresh_queue_hook(struct __btrfs_workqueue *wq)
 135 {
 136         if (wq->thresh == NO_THRESHOLD)
 137                 return;
 138         atomic_inc(&wq->pending);
 139 }
 140
 141 /*
 142  * Hook for threshold which will be called before executing the work,
 143  * This hook is called in kthread content.
 144  * So workqueue_set_max_active is called here.
 145  */
 146 static inline void thresh_exec_hook(struct __btrfs_workqueue *wq)
 147 {
 148         int new_max_active;
 149         long pending;
 150         int need_change = 0;
 151
 152         if (wq->thresh == NO_THRESHOLD)
 153                 return;
 154
 155         atomic_dec(&wq->pending);
 156         spin_lock(&wq->thres_lock);
 157         /*
 158          * Use wq->count to limit the calling frequency of
 159          * workqueue_set_max_active.
 160          */
 161         wq->count++;
 162         wq->count %= (wq->thresh / 4);
 163         if (!wq->count)
 164                 goto  out;
 165         new_max_active = wq->current_max;
 166
 167         /*
 168          * pending may be changed later, but it's OK since we really
 169          * don't need it so accurate to calculate new_max_active.
 170          */
 171         pending = atomic_read(&wq->pending);
 172         if (pending > wq->thresh)
 173                 new_max_active++;
 174         if (pending < wq->thresh / 2)
 175                 new_max_active--;
 176         new_max_active = clamp_val(new_max_active, 1, wq->max_active);
 177         if (new_max_active != wq->current_max)  {
 178                 need_change = 1;
 179                 wq->current_max = new_max_active;
 180         }
 181 out:
 182         spin_unlock(&wq->thres_lock);
 183
 184         if (need_change) {
 185                 workqueue_set_max_active(wq->normal_wq, wq->current_max);
 186         }
 187 }
 188
 189 static void run_ordered_work(struct __btrfs_workqueue *wq)
 190 {
 191         struct list_head *list = &wq->ordered_list;
 192         struct btrfs_work *work;
 193         spinlock_t *lock = &wq->list_lock;
 194         unsigned long flags;
 195
 196         while (1) {
 197                 spin_lock_irqsave(lock, flags);
 198                 if (list_empty(list))
 199                         break;
 200                 work = list_entry(list->next, struct btrfs_work,
 201                                   ordered_list);
 202                 if (!test_bit(WORK_DONE_BIT, &work->flags))
 203                         break;
 204
 205                 /*
 206                  * we are going to call the ordered done function, but
 207                  * we leave the work item on the list as a barrier so
 208                  * that later work items that are done don't have their
 209                  * functions called before this one returns
 210                  */
 211                 if (test_and_set_bit(WORK_ORDER_DONE_BIT, &work->flags))
 212                         break;
 213                 spin_unlock_irqrestore(lock, flags);
 214                 work->ordered_func(work);
 215
 216                 /* now take the lock again and drop our item from the list */
 217                 spin_lock_irqsave(lock, flags);
 218                 list_del(&work->ordered_list);
 219                 spin_unlock_irqrestore(lock, flags);
 220
 221                 /*
 222                  * we don't want to call the ordered free functions
 223                  * with the lock held though
 224                  */
 225                 work->ordered_free(work);
 226         }
 227         spin_unlock_irqrestore(lock, flags);
 228 }
 229
 230 static void normal_work_helper(struct work_struct *arg)
 231 {
 232         struct btrfs_work *work;
 233         struct __btrfs_workqueue *wq;
 234         int need_order = 0;
 235
 236         work = container_of(arg, struct btrfs_work, normal_work);
 237         /*
 238          * We should not touch things inside work in the following cases:
 239          * 1) after work->func() if it has no ordered_free
 240          *    Since the struct is freed in work->func().
 241          * 2) after setting WORK_DONE_BIT
 242          *    The work may be freed in other threads almost instantly.
 243          * So we save the needed things here.
 244          */
 245         if (work->ordered_func)
 246                 need_order = 1;
 247         wq = work->wq;
 248
 249         thresh_exec_hook(wq);
 250         work->func(work);
 251         if (need_order) {
 252                 set_bit(WORK_DONE_BIT, &work->flags);
 253                 run_ordered_work(wq);
 254         }
 255 }
 256
 257 void btrfs_init_work(struct btrfs_work *work,
 258                      void (*func)(struct btrfs_work *),
 259                      void (*ordered_func)(struct btrfs_work *),
 260                      void (*ordered_free)(struct btrfs_work *))
 261 {
 262         work->func = func;
 263         work->ordered_func = ordered_func;
 264         work->ordered_free = ordered_free;
 265         INIT_WORK(&work->normal_work, normal_work_helper);
 266         INIT_LIST_HEAD(&work->ordered_list);
 267         work->flags = 0;
 268 }
 269
 270 static inline void __btrfs_queue_work(struct __btrfs_workqueue *wq,
 271                                       struct btrfs_work *work)
 272 {
 273         unsigned long flags;
 274
 275         work->wq = wq;
 276         thresh_queue_hook(wq);
 277         if (work->ordered_func) {
 278                 spin_lock_irqsave(&wq->list_lock, flags);
 279                 list_add_tail(&work->ordered_list, &wq->ordered_list);
 280                 spin_unlock_irqrestore(&wq->list_lock, flags);
 281         }
 282         queue_work(wq->normal_wq, &work->normal_work);
 283 }
 284
 285 void btrfs_queue_work(struct btrfs_workqueue *wq,
 286                       struct btrfs_work *work)
 287 {
 288         struct __btrfs_workqueue *dest_wq;
 289
 290         if (test_bit(WORK_HIGH_PRIO_BIT, &work->flags) && wq->high)
 291                 dest_wq = wq->high;
 292         else
 293                 dest_wq = wq->normal;
 294         __btrfs_queue_work(dest_wq, work);
 295 }
 296
 297 static inline void
 298 __btrfs_destroy_workqueue(struct __btrfs_workqueue *wq)
 299 {
 300         destroy_workqueue(wq->normal_wq);
 301         kfree(wq);
 302 }
 303
 304 void btrfs_destroy_workqueue(struct btrfs_workqueue *wq)
 305 {
 306         if (!wq)
 307                 return;
 308         if (wq->high)
 309                 __btrfs_destroy_workqueue(wq->high);
 310         __btrfs_destroy_workqueue(wq->normal);
 311 }
 312
 313 void btrfs_workqueue_set_max(struct btrfs_workqueue *wq, int max)
 314 {
 315         wq->normal->max_active = max;
 316         if (wq->high)
 317                 wq->high->max_active = max;
 318 }
 319
 320 void btrfs_set_work_high_priority(struct btrfs_work *work)
 321 {
 322         set_bit(WORK_HIGH_PRIO_BIT, &work->flags);
 323 }