blob: dac5bf59309d04d119b699ba47d849993edbec09 [file] [log] [blame]
Andrew Morton3fcfab12006-10-19 23:28:16 -07001
2#include <linux/wait.h>
3#include <linux/backing-dev.h>
Jens Axboe03ba3782009-09-09 09:08:54 +02004#include <linux/kthread.h>
5#include <linux/freezer.h>
Andrew Morton3fcfab12006-10-19 23:28:16 -07006#include <linux/fs.h>
Jens Axboe26160152009-03-17 09:35:06 +01007#include <linux/pagemap.h>
Jens Axboe03ba3782009-09-09 09:08:54 +02008#include <linux/mm.h>
Andrew Morton3fcfab12006-10-19 23:28:16 -07009#include <linux/sched.h>
10#include <linux/module.h>
Peter Zijlstracf0ca9f2008-04-30 00:54:32 -070011#include <linux/writeback.h>
12#include <linux/device.h>
Dave Chinner455b2862010-07-07 13:24:06 +100013#include <trace/events/writeback.h>
Peter Zijlstracf0ca9f2008-04-30 00:54:32 -070014
Jens Axboec3c53202010-04-22 11:37:01 +020015static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0);
16
Jörn Engel5129a462010-04-25 08:54:42 +020017struct backing_dev_info noop_backing_dev_info = {
18 .name = "noop",
Jan Kara976e48f2010-09-21 11:48:55 +020019 .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
Jörn Engel5129a462010-04-25 08:54:42 +020020};
Tejun Heoa212b102015-05-22 17:13:33 -040021EXPORT_SYMBOL_GPL(noop_backing_dev_info);
Jörn Engel5129a462010-04-25 08:54:42 +020022
Peter Zijlstracf0ca9f2008-04-30 00:54:32 -070023static struct class *bdi_class;
Jens Axboecfc4ba52009-09-14 13:12:40 +020024
25/*
Tejun Heo181387d2013-04-01 19:08:06 -070026 * bdi_lock protects updates to bdi_list. bdi_list has RCU reader side
Jens Axboecfc4ba52009-09-14 13:12:40 +020027 * locking.
28 */
Jens Axboe03ba3782009-09-09 09:08:54 +020029DEFINE_SPINLOCK(bdi_lock);
Jens Axboe66f3b8e2009-09-02 09:19:46 +020030LIST_HEAD(bdi_list);
Jens Axboe03ba3782009-09-09 09:08:54 +020031
Tejun Heo839a8e82013-04-01 19:08:06 -070032/* bdi_wq serves all asynchronous writeback tasks */
33struct workqueue_struct *bdi_wq;
34
Miklos Szeredi76f14182008-04-30 00:54:36 -070035#ifdef CONFIG_DEBUG_FS
36#include <linux/debugfs.h>
37#include <linux/seq_file.h>
38
39static struct dentry *bdi_debug_root;
40
41static void bdi_debug_init(void)
42{
43 bdi_debug_root = debugfs_create_dir("bdi", NULL);
44}
45
46static int bdi_debug_stats_show(struct seq_file *m, void *v)
47{
48 struct backing_dev_info *bdi = m->private;
Christoph Hellwigc1955ce2010-06-19 23:08:06 +020049 struct bdi_writeback *wb = &bdi->wb;
David Rientjes364aeb22009-01-06 14:39:29 -080050 unsigned long background_thresh;
51 unsigned long dirty_thresh;
Tejun Heo0d960a32015-05-22 18:23:19 -040052 unsigned long wb_thresh;
Theodore Ts'o0ae45f62015-02-02 00:37:00 -050053 unsigned long nr_dirty, nr_io, nr_more_io, nr_dirty_time;
Jens Axboef09b00d2009-05-25 09:08:21 +020054 struct inode *inode;
55
Theodore Ts'o0ae45f62015-02-02 00:37:00 -050056 nr_dirty = nr_io = nr_more_io = nr_dirty_time = 0;
Christoph Hellwigf758eea2011-04-21 18:19:44 -060057 spin_lock(&wb->list_lock);
Nick Piggin7ccf19a2010-10-21 11:49:30 +110058 list_for_each_entry(inode, &wb->b_dirty, i_wb_list)
Christoph Hellwigc1955ce2010-06-19 23:08:06 +020059 nr_dirty++;
Nick Piggin7ccf19a2010-10-21 11:49:30 +110060 list_for_each_entry(inode, &wb->b_io, i_wb_list)
Christoph Hellwigc1955ce2010-06-19 23:08:06 +020061 nr_io++;
Nick Piggin7ccf19a2010-10-21 11:49:30 +110062 list_for_each_entry(inode, &wb->b_more_io, i_wb_list)
Christoph Hellwigc1955ce2010-06-19 23:08:06 +020063 nr_more_io++;
Theodore Ts'o0ae45f62015-02-02 00:37:00 -050064 list_for_each_entry(inode, &wb->b_dirty_time, i_wb_list)
65 if (inode->i_state & I_DIRTY_TIME)
66 nr_dirty_time++;
Christoph Hellwigf758eea2011-04-21 18:19:44 -060067 spin_unlock(&wb->list_lock);
Miklos Szeredi76f14182008-04-30 00:54:36 -070068
Wu Fengguang16c40422010-08-11 14:17:39 -070069 global_dirty_limits(&background_thresh, &dirty_thresh);
Tejun Heo0d960a32015-05-22 18:23:19 -040070 wb_thresh = wb_calc_thresh(wb, dirty_thresh);
Miklos Szeredi76f14182008-04-30 00:54:36 -070071
72#define K(x) ((x) << (PAGE_SHIFT - 10))
73 seq_printf(m,
Wu Fengguang00821b02010-08-29 11:28:45 -060074 "BdiWriteback: %10lu kB\n"
75 "BdiReclaimable: %10lu kB\n"
76 "BdiDirtyThresh: %10lu kB\n"
77 "DirtyThresh: %10lu kB\n"
78 "BackgroundThresh: %10lu kB\n"
Wu Fengguangc8e28ce2011-01-23 10:07:47 -060079 "BdiDirtied: %10lu kB\n"
Wu Fengguang00821b02010-08-29 11:28:45 -060080 "BdiWritten: %10lu kB\n"
81 "BdiWriteBandwidth: %10lu kBps\n"
82 "b_dirty: %10lu\n"
83 "b_io: %10lu\n"
84 "b_more_io: %10lu\n"
Theodore Ts'o0ae45f62015-02-02 00:37:00 -050085 "b_dirty_time: %10lu\n"
Wu Fengguang00821b02010-08-29 11:28:45 -060086 "bdi_list: %10u\n"
87 "state: %10lx\n",
Tejun Heo93f78d82015-05-22 17:13:27 -040088 (unsigned long) K(wb_stat(wb, WB_WRITEBACK)),
89 (unsigned long) K(wb_stat(wb, WB_RECLAIMABLE)),
Tejun Heo0d960a32015-05-22 18:23:19 -040090 K(wb_thresh),
Jan Karaf7d2b1e2010-12-08 22:44:24 -060091 K(dirty_thresh),
92 K(background_thresh),
Tejun Heo93f78d82015-05-22 17:13:27 -040093 (unsigned long) K(wb_stat(wb, WB_DIRTIED)),
94 (unsigned long) K(wb_stat(wb, WB_WRITTEN)),
Tejun Heoa88a3412015-05-22 17:13:28 -040095 (unsigned long) K(wb->write_bandwidth),
Jan Karaf7d2b1e2010-12-08 22:44:24 -060096 nr_dirty,
97 nr_io,
98 nr_more_io,
Theodore Ts'o0ae45f62015-02-02 00:37:00 -050099 nr_dirty_time,
Tejun Heo44522262015-05-22 17:13:26 -0400100 !list_empty(&bdi->bdi_list), bdi->wb.state);
Miklos Szeredi76f14182008-04-30 00:54:36 -0700101#undef K
102
103 return 0;
104}
105
106static int bdi_debug_stats_open(struct inode *inode, struct file *file)
107{
108 return single_open(file, bdi_debug_stats_show, inode->i_private);
109}
110
111static const struct file_operations bdi_debug_stats_fops = {
112 .open = bdi_debug_stats_open,
113 .read = seq_read,
114 .llseek = seq_lseek,
115 .release = single_release,
116};
117
118static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
119{
120 bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
121 bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,
122 bdi, &bdi_debug_stats_fops);
123}
124
125static void bdi_debug_unregister(struct backing_dev_info *bdi)
126{
127 debugfs_remove(bdi->debug_stats);
128 debugfs_remove(bdi->debug_dir);
129}
130#else
131static inline void bdi_debug_init(void)
132{
133}
134static inline void bdi_debug_register(struct backing_dev_info *bdi,
135 const char *name)
136{
137}
138static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
139{
140}
141#endif
142
Peter Zijlstracf0ca9f2008-04-30 00:54:32 -0700143static ssize_t read_ahead_kb_store(struct device *dev,
144 struct device_attribute *attr,
145 const char *buf, size_t count)
146{
147 struct backing_dev_info *bdi = dev_get_drvdata(dev);
Peter Zijlstracf0ca9f2008-04-30 00:54:32 -0700148 unsigned long read_ahead_kb;
Namjae Jeon7034ed12012-08-25 16:57:27 +0800149 ssize_t ret;
Peter Zijlstracf0ca9f2008-04-30 00:54:32 -0700150
Namjae Jeon7034ed12012-08-25 16:57:27 +0800151 ret = kstrtoul(buf, 10, &read_ahead_kb);
152 if (ret < 0)
153 return ret;
154
155 bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
156
157 return count;
Peter Zijlstracf0ca9f2008-04-30 00:54:32 -0700158}
159
160#define K(pages) ((pages) << (PAGE_SHIFT - 10))
161
162#define BDI_SHOW(name, expr) \
163static ssize_t name##_show(struct device *dev, \
164 struct device_attribute *attr, char *page) \
165{ \
166 struct backing_dev_info *bdi = dev_get_drvdata(dev); \
167 \
168 return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr); \
Greg Kroah-Hartmand9e12412013-07-24 15:05:26 -0700169} \
170static DEVICE_ATTR_RW(name);
Peter Zijlstracf0ca9f2008-04-30 00:54:32 -0700171
172BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
173
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700174static ssize_t min_ratio_store(struct device *dev,
175 struct device_attribute *attr, const char *buf, size_t count)
176{
177 struct backing_dev_info *bdi = dev_get_drvdata(dev);
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700178 unsigned int ratio;
Namjae Jeon7034ed12012-08-25 16:57:27 +0800179 ssize_t ret;
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700180
Namjae Jeon7034ed12012-08-25 16:57:27 +0800181 ret = kstrtouint(buf, 10, &ratio);
182 if (ret < 0)
183 return ret;
184
185 ret = bdi_set_min_ratio(bdi, ratio);
186 if (!ret)
187 ret = count;
188
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700189 return ret;
190}
191BDI_SHOW(min_ratio, bdi->min_ratio)
192
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700193static ssize_t max_ratio_store(struct device *dev,
194 struct device_attribute *attr, const char *buf, size_t count)
195{
196 struct backing_dev_info *bdi = dev_get_drvdata(dev);
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700197 unsigned int ratio;
Namjae Jeon7034ed12012-08-25 16:57:27 +0800198 ssize_t ret;
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700199
Namjae Jeon7034ed12012-08-25 16:57:27 +0800200 ret = kstrtouint(buf, 10, &ratio);
201 if (ret < 0)
202 return ret;
203
204 ret = bdi_set_max_ratio(bdi, ratio);
205 if (!ret)
206 ret = count;
207
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700208 return ret;
209}
210BDI_SHOW(max_ratio, bdi->max_ratio)
211
Darrick J. Wong7d311cd2013-02-21 16:42:48 -0800212static ssize_t stable_pages_required_show(struct device *dev,
213 struct device_attribute *attr,
214 char *page)
215{
216 struct backing_dev_info *bdi = dev_get_drvdata(dev);
217
218 return snprintf(page, PAGE_SIZE-1, "%d\n",
219 bdi_cap_stable_pages_required(bdi) ? 1 : 0);
220}
Greg Kroah-Hartmand9e12412013-07-24 15:05:26 -0700221static DEVICE_ATTR_RO(stable_pages_required);
Darrick J. Wong7d311cd2013-02-21 16:42:48 -0800222
Greg Kroah-Hartmand9e12412013-07-24 15:05:26 -0700223static struct attribute *bdi_dev_attrs[] = {
224 &dev_attr_read_ahead_kb.attr,
225 &dev_attr_min_ratio.attr,
226 &dev_attr_max_ratio.attr,
227 &dev_attr_stable_pages_required.attr,
228 NULL,
Peter Zijlstracf0ca9f2008-04-30 00:54:32 -0700229};
Greg Kroah-Hartmand9e12412013-07-24 15:05:26 -0700230ATTRIBUTE_GROUPS(bdi_dev);
Peter Zijlstracf0ca9f2008-04-30 00:54:32 -0700231
232static __init int bdi_class_init(void)
233{
234 bdi_class = class_create(THIS_MODULE, "bdi");
Anton Blanchard14421452010-04-02 09:46:55 +0200235 if (IS_ERR(bdi_class))
236 return PTR_ERR(bdi_class);
237
Greg Kroah-Hartmand9e12412013-07-24 15:05:26 -0700238 bdi_class->dev_groups = bdi_dev_groups;
Miklos Szeredi76f14182008-04-30 00:54:36 -0700239 bdi_debug_init();
Peter Zijlstracf0ca9f2008-04-30 00:54:32 -0700240 return 0;
241}
Miklos Szeredi76f14182008-04-30 00:54:36 -0700242postcore_initcall(bdi_class_init);
Peter Zijlstracf0ca9f2008-04-30 00:54:32 -0700243
Jens Axboe26160152009-03-17 09:35:06 +0100244static int __init default_bdi_init(void)
245{
246 int err;
247
Tejun Heo839a8e82013-04-01 19:08:06 -0700248 bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_FREEZABLE |
Tejun Heob5c872d2013-04-01 19:08:06 -0700249 WQ_UNBOUND | WQ_SYSFS, 0);
Tejun Heo839a8e82013-04-01 19:08:06 -0700250 if (!bdi_wq)
251 return -ENOMEM;
252
Jan Kara976e48f2010-09-21 11:48:55 +0200253 err = bdi_init(&noop_backing_dev_info);
Jens Axboe26160152009-03-17 09:35:06 +0100254
255 return err;
256}
257subsys_initcall(default_bdi_init);
258
Artem Bityutskiy64677162010-07-25 14:29:22 +0300259/*
Tejun Heof0054bb2015-05-22 17:13:30 -0400260 * This function is used when the first inode for this wb is marked dirty. It
Artem Bityutskiy64677162010-07-25 14:29:22 +0300261 * wakes-up the corresponding bdi thread which should then take care of the
262 * periodic background write-out of dirty inodes. Since the write-out would
263 * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
264 * set up a timer which wakes the bdi thread up later.
265 *
266 * Note, we wouldn't bother setting up the timer, but this function is on the
267 * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
268 * by delaying the wake-up.
Derek Basehore6ca738d2014-04-03 14:46:22 -0700269 *
270 * We have to be careful not to postpone flush work if it is scheduled for
271 * earlier. Thus we use queue_delayed_work().
Artem Bityutskiy64677162010-07-25 14:29:22 +0300272 */
Tejun Heof0054bb2015-05-22 17:13:30 -0400273void wb_wakeup_delayed(struct bdi_writeback *wb)
Artem Bityutskiy64677162010-07-25 14:29:22 +0300274{
275 unsigned long timeout;
276
277 timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
Tejun Heof0054bb2015-05-22 17:13:30 -0400278 spin_lock_bh(&wb->work_lock);
279 if (test_bit(WB_registered, &wb->state))
280 queue_delayed_work(bdi_wq, &wb->dwork, timeout);
281 spin_unlock_bh(&wb->work_lock);
Jens Axboe03ba3782009-09-09 09:08:54 +0200282}
283
Jens Axboecfc4ba52009-09-14 13:12:40 +0200284/*
Tejun Heoa88a3412015-05-22 17:13:28 -0400285 * Initial write bandwidth: 100 MB/s
Jens Axboecfc4ba52009-09-14 13:12:40 +0200286 */
Tejun Heoa88a3412015-05-22 17:13:28 -0400287#define INIT_BW (100 << (20 - PAGE_SHIFT))
Jens Axboecfc4ba52009-09-14 13:12:40 +0200288
Tejun Heo8395cd92015-05-22 17:13:34 -0400289static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi,
Tejun Heoa13f35e2015-07-02 08:44:34 -0600290 int blkcg_id, gfp_t gfp)
Artem Bityutskiy64677162010-07-25 14:29:22 +0300291{
Tejun Heo93f78d82015-05-22 17:13:27 -0400292 int i, err;
293
Artem Bityutskiy64677162010-07-25 14:29:22 +0300294 memset(wb, 0, sizeof(*wb));
295
296 wb->bdi = bdi;
297 wb->last_old_flush = jiffies;
298 INIT_LIST_HEAD(&wb->b_dirty);
299 INIT_LIST_HEAD(&wb->b_io);
300 INIT_LIST_HEAD(&wb->b_more_io);
Theodore Ts'o0ae45f62015-02-02 00:37:00 -0500301 INIT_LIST_HEAD(&wb->b_dirty_time);
Christoph Hellwigf758eea2011-04-21 18:19:44 -0600302 spin_lock_init(&wb->list_lock);
Tejun Heo93f78d82015-05-22 17:13:27 -0400303
Tejun Heoa88a3412015-05-22 17:13:28 -0400304 wb->bw_time_stamp = jiffies;
305 wb->balanced_dirty_ratelimit = INIT_BW;
306 wb->dirty_ratelimit = INIT_BW;
307 wb->write_bandwidth = INIT_BW;
308 wb->avg_write_bandwidth = INIT_BW;
309
Tejun Heof0054bb2015-05-22 17:13:30 -0400310 spin_lock_init(&wb->work_lock);
311 INIT_LIST_HEAD(&wb->work_list);
312 INIT_DELAYED_WORK(&wb->dwork, wb_workfn);
313
Tejun Heoa13f35e2015-07-02 08:44:34 -0600314 wb->congested = wb_congested_get_create(bdi, blkcg_id, gfp);
315 if (!wb->congested)
316 return -ENOMEM;
317
Tejun Heo8395cd92015-05-22 17:13:34 -0400318 err = fprop_local_init_percpu(&wb->completions, gfp);
Tejun Heoa88a3412015-05-22 17:13:28 -0400319 if (err)
Tejun Heoa13f35e2015-07-02 08:44:34 -0600320 goto out_put_cong;
Tejun Heoa88a3412015-05-22 17:13:28 -0400321
Tejun Heo93f78d82015-05-22 17:13:27 -0400322 for (i = 0; i < NR_WB_STAT_ITEMS; i++) {
Tejun Heo8395cd92015-05-22 17:13:34 -0400323 err = percpu_counter_init(&wb->stat[i], 0, gfp);
Tejun Heoa13f35e2015-07-02 08:44:34 -0600324 if (err)
325 goto out_destroy_stat;
Tejun Heo93f78d82015-05-22 17:13:27 -0400326 }
327
328 return 0;
Tejun Heoa13f35e2015-07-02 08:44:34 -0600329
330out_destroy_stat:
331 while (--i)
332 percpu_counter_destroy(&wb->stat[i]);
333 fprop_local_destroy_percpu(&wb->completions);
334out_put_cong:
335 wb_congested_put(wb->congested);
336 return err;
Peter Zijlstracf0ca9f2008-04-30 00:54:32 -0700337}
Jens Axboe03ba3782009-09-09 09:08:54 +0200338
Tejun Heo46100072015-05-22 17:13:31 -0400339/*
340 * Remove bdi from the global list and shutdown any threads we have running
341 */
342static void wb_shutdown(struct bdi_writeback *wb)
343{
344 /* Make sure nobody queues further work */
345 spin_lock_bh(&wb->work_lock);
346 if (!test_and_clear_bit(WB_registered, &wb->state)) {
347 spin_unlock_bh(&wb->work_lock);
348 return;
349 }
350 spin_unlock_bh(&wb->work_lock);
351
352 /*
353 * Drain work list and shutdown the delayed_work. !WB_registered
354 * tells wb_workfn() that @wb is dying and its work_list needs to
355 * be drained no matter what.
356 */
357 mod_delayed_work(bdi_wq, &wb->dwork, 0);
358 flush_delayed_work(&wb->dwork);
359 WARN_ON(!list_empty(&wb->work_list));
360}
361
Tejun Heof0054bb2015-05-22 17:13:30 -0400362static void wb_exit(struct bdi_writeback *wb)
Tejun Heo93f78d82015-05-22 17:13:27 -0400363{
364 int i;
365
366 WARN_ON(delayed_work_pending(&wb->dwork));
367
368 for (i = 0; i < NR_WB_STAT_ITEMS; i++)
369 percpu_counter_destroy(&wb->stat[i]);
Artem Bityutskiy64677162010-07-25 14:29:22 +0300370
Tejun Heoa88a3412015-05-22 17:13:28 -0400371 fprop_local_destroy_percpu(&wb->completions);
Tejun Heoa13f35e2015-07-02 08:44:34 -0600372 wb_congested_put(wb->congested);
Tejun Heoa88a3412015-05-22 17:13:28 -0400373}
Wu Fengguange98be2d2010-08-29 11:22:30 -0600374
Tejun Heo52ebea72015-05-22 17:13:37 -0400375#ifdef CONFIG_CGROUP_WRITEBACK
376
377#include <linux/memcontrol.h>
378
379/*
380 * cgwb_lock protects bdi->cgwb_tree, bdi->cgwb_congested_tree,
381 * blkcg->cgwb_list, and memcg->cgwb_list. bdi->cgwb_tree is also RCU
382 * protected. cgwb_release_wait is used to wait for the completion of cgwb
383 * releases from bdi destruction path.
384 */
385static DEFINE_SPINLOCK(cgwb_lock);
386static DECLARE_WAIT_QUEUE_HEAD(cgwb_release_wait);
387
388/**
389 * wb_congested_get_create - get or create a wb_congested
390 * @bdi: associated bdi
391 * @blkcg_id: ID of the associated blkcg
392 * @gfp: allocation mask
393 *
394 * Look up the wb_congested for @blkcg_id on @bdi. If missing, create one.
395 * The returned wb_congested has its reference count incremented. Returns
396 * NULL on failure.
397 */
398struct bdi_writeback_congested *
399wb_congested_get_create(struct backing_dev_info *bdi, int blkcg_id, gfp_t gfp)
400{
401 struct bdi_writeback_congested *new_congested = NULL, *congested;
402 struct rb_node **node, *parent;
403 unsigned long flags;
Tejun Heo52ebea72015-05-22 17:13:37 -0400404retry:
405 spin_lock_irqsave(&cgwb_lock, flags);
406
407 node = &bdi->cgwb_congested_tree.rb_node;
408 parent = NULL;
409
410 while (*node != NULL) {
411 parent = *node;
412 congested = container_of(parent, struct bdi_writeback_congested,
413 rb_node);
414 if (congested->blkcg_id < blkcg_id)
415 node = &parent->rb_left;
416 else if (congested->blkcg_id > blkcg_id)
417 node = &parent->rb_right;
418 else
419 goto found;
420 }
421
422 if (new_congested) {
423 /* !found and storage for new one already allocated, insert */
424 congested = new_congested;
425 new_congested = NULL;
426 rb_link_node(&congested->rb_node, parent, node);
427 rb_insert_color(&congested->rb_node, &bdi->cgwb_congested_tree);
Tejun Heo52ebea72015-05-22 17:13:37 -0400428 goto found;
429 }
430
431 spin_unlock_irqrestore(&cgwb_lock, flags);
432
433 /* allocate storage for new one and retry */
434 new_congested = kzalloc(sizeof(*new_congested), gfp);
435 if (!new_congested)
436 return NULL;
437
438 atomic_set(&new_congested->refcnt, 0);
439 new_congested->bdi = bdi;
440 new_congested->blkcg_id = blkcg_id;
441 goto retry;
442
443found:
444 atomic_inc(&congested->refcnt);
445 spin_unlock_irqrestore(&cgwb_lock, flags);
446 kfree(new_congested);
447 return congested;
448}
449
450/**
451 * wb_congested_put - put a wb_congested
452 * @congested: wb_congested to put
453 *
454 * Put @congested and destroy it if the refcnt reaches zero.
455 */
456void wb_congested_put(struct bdi_writeback_congested *congested)
457{
Tejun Heo52ebea72015-05-22 17:13:37 -0400458 unsigned long flags;
459
Tejun Heo52ebea72015-05-22 17:13:37 -0400460 local_irq_save(flags);
461 if (!atomic_dec_and_lock(&congested->refcnt, &cgwb_lock)) {
462 local_irq_restore(flags);
463 return;
464 }
465
Tejun Heoa20135f2015-07-01 20:53:37 -0400466 /* bdi might already have been destroyed leaving @congested unlinked */
467 if (congested->bdi) {
468 rb_erase(&congested->rb_node,
469 &congested->bdi->cgwb_congested_tree);
470 congested->bdi = NULL;
471 }
472
Tejun Heo52ebea72015-05-22 17:13:37 -0400473 spin_unlock_irqrestore(&cgwb_lock, flags);
474 kfree(congested);
Tejun Heo52ebea72015-05-22 17:13:37 -0400475}
476
477static void cgwb_release_workfn(struct work_struct *work)
478{
479 struct bdi_writeback *wb = container_of(work, struct bdi_writeback,
480 release_work);
481 struct backing_dev_info *bdi = wb->bdi;
482
483 wb_shutdown(wb);
484
485 css_put(wb->memcg_css);
486 css_put(wb->blkcg_css);
Tejun Heo52ebea72015-05-22 17:13:37 -0400487
Tejun Heo841710a2015-05-22 18:23:33 -0400488 fprop_local_destroy_percpu(&wb->memcg_completions);
Tejun Heo52ebea72015-05-22 17:13:37 -0400489 percpu_ref_exit(&wb->refcnt);
490 wb_exit(wb);
491 kfree_rcu(wb, rcu);
492
493 if (atomic_dec_and_test(&bdi->usage_cnt))
494 wake_up_all(&cgwb_release_wait);
495}
496
497static void cgwb_release(struct percpu_ref *refcnt)
498{
499 struct bdi_writeback *wb = container_of(refcnt, struct bdi_writeback,
500 refcnt);
501 schedule_work(&wb->release_work);
502}
503
504static void cgwb_kill(struct bdi_writeback *wb)
505{
506 lockdep_assert_held(&cgwb_lock);
507
508 WARN_ON(!radix_tree_delete(&wb->bdi->cgwb_tree, wb->memcg_css->id));
509 list_del(&wb->memcg_node);
510 list_del(&wb->blkcg_node);
511 percpu_ref_kill(&wb->refcnt);
512}
513
514static int cgwb_create(struct backing_dev_info *bdi,
515 struct cgroup_subsys_state *memcg_css, gfp_t gfp)
516{
517 struct mem_cgroup *memcg;
518 struct cgroup_subsys_state *blkcg_css;
519 struct blkcg *blkcg;
520 struct list_head *memcg_cgwb_list, *blkcg_cgwb_list;
521 struct bdi_writeback *wb;
522 unsigned long flags;
523 int ret = 0;
524
525 memcg = mem_cgroup_from_css(memcg_css);
526 blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &blkio_cgrp_subsys);
527 blkcg = css_to_blkcg(blkcg_css);
528 memcg_cgwb_list = mem_cgroup_cgwb_list(memcg);
529 blkcg_cgwb_list = &blkcg->cgwb_list;
530
531 /* look up again under lock and discard on blkcg mismatch */
532 spin_lock_irqsave(&cgwb_lock, flags);
533 wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
534 if (wb && wb->blkcg_css != blkcg_css) {
535 cgwb_kill(wb);
536 wb = NULL;
537 }
538 spin_unlock_irqrestore(&cgwb_lock, flags);
539 if (wb)
540 goto out_put;
541
542 /* need to create a new one */
543 wb = kmalloc(sizeof(*wb), gfp);
544 if (!wb)
545 return -ENOMEM;
546
Tejun Heoa13f35e2015-07-02 08:44:34 -0600547 ret = wb_init(wb, bdi, blkcg_css->id, gfp);
Tejun Heo52ebea72015-05-22 17:13:37 -0400548 if (ret)
549 goto err_free;
550
551 ret = percpu_ref_init(&wb->refcnt, cgwb_release, 0, gfp);
552 if (ret)
553 goto err_wb_exit;
554
Tejun Heo841710a2015-05-22 18:23:33 -0400555 ret = fprop_local_init_percpu(&wb->memcg_completions, gfp);
556 if (ret)
557 goto err_ref_exit;
558
Tejun Heo52ebea72015-05-22 17:13:37 -0400559 wb->memcg_css = memcg_css;
560 wb->blkcg_css = blkcg_css;
561 INIT_WORK(&wb->release_work, cgwb_release_workfn);
562 set_bit(WB_registered, &wb->state);
563
564 /*
565 * The root wb determines the registered state of the whole bdi and
566 * memcg_cgwb_list and blkcg_cgwb_list's next pointers indicate
567 * whether they're still online. Don't link @wb if any is dead.
568 * See wb_memcg_offline() and wb_blkcg_offline().
569 */
570 ret = -ENODEV;
571 spin_lock_irqsave(&cgwb_lock, flags);
572 if (test_bit(WB_registered, &bdi->wb.state) &&
573 blkcg_cgwb_list->next && memcg_cgwb_list->next) {
574 /* we might have raced another instance of this function */
575 ret = radix_tree_insert(&bdi->cgwb_tree, memcg_css->id, wb);
576 if (!ret) {
577 atomic_inc(&bdi->usage_cnt);
578 list_add(&wb->memcg_node, memcg_cgwb_list);
579 list_add(&wb->blkcg_node, blkcg_cgwb_list);
580 css_get(memcg_css);
581 css_get(blkcg_css);
582 }
583 }
584 spin_unlock_irqrestore(&cgwb_lock, flags);
585 if (ret) {
586 if (ret == -EEXIST)
587 ret = 0;
Tejun Heoa13f35e2015-07-02 08:44:34 -0600588 goto err_fprop_exit;
Tejun Heo52ebea72015-05-22 17:13:37 -0400589 }
590 goto out_put;
591
Tejun Heo841710a2015-05-22 18:23:33 -0400592err_fprop_exit:
593 fprop_local_destroy_percpu(&wb->memcg_completions);
Tejun Heo52ebea72015-05-22 17:13:37 -0400594err_ref_exit:
595 percpu_ref_exit(&wb->refcnt);
596err_wb_exit:
597 wb_exit(wb);
598err_free:
599 kfree(wb);
600out_put:
601 css_put(blkcg_css);
602 return ret;
603}
604
605/**
606 * wb_get_create - get wb for a given memcg, create if necessary
607 * @bdi: target bdi
608 * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
609 * @gfp: allocation mask to use
610 *
611 * Try to get the wb for @memcg_css on @bdi. If it doesn't exist, try to
612 * create one. The returned wb has its refcount incremented.
613 *
614 * This function uses css_get() on @memcg_css and thus expects its refcnt
615 * to be positive on invocation. IOW, rcu_read_lock() protection on
616 * @memcg_css isn't enough. try_get it before calling this function.
617 *
618 * A wb is keyed by its associated memcg. As blkcg implicitly enables
619 * memcg on the default hierarchy, memcg association is guaranteed to be
620 * more specific (equal or descendant to the associated blkcg) and thus can
621 * identify both the memcg and blkcg associations.
622 *
623 * Because the blkcg associated with a memcg may change as blkcg is enabled
624 * and disabled closer to root in the hierarchy, each wb keeps track of
625 * both the memcg and blkcg associated with it and verifies the blkcg on
626 * each lookup. On mismatch, the existing wb is discarded and a new one is
627 * created.
628 */
629struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
630 struct cgroup_subsys_state *memcg_css,
631 gfp_t gfp)
632{
633 struct bdi_writeback *wb;
634
635 might_sleep_if(gfp & __GFP_WAIT);
636
637 if (!memcg_css->parent)
638 return &bdi->wb;
639
640 do {
641 rcu_read_lock();
642 wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
643 if (wb) {
644 struct cgroup_subsys_state *blkcg_css;
645
646 /* see whether the blkcg association has changed */
647 blkcg_css = cgroup_get_e_css(memcg_css->cgroup,
648 &blkio_cgrp_subsys);
649 if (unlikely(wb->blkcg_css != blkcg_css ||
650 !wb_tryget(wb)))
651 wb = NULL;
652 css_put(blkcg_css);
653 }
654 rcu_read_unlock();
655 } while (!wb && !cgwb_create(bdi, memcg_css, gfp));
656
657 return wb;
658}
659
Tejun Heoa13f35e2015-07-02 08:44:34 -0600660static int cgwb_bdi_init(struct backing_dev_info *bdi)
Tejun Heo52ebea72015-05-22 17:13:37 -0400661{
Tejun Heoa13f35e2015-07-02 08:44:34 -0600662 int ret;
663
Tejun Heo52ebea72015-05-22 17:13:37 -0400664 INIT_RADIX_TREE(&bdi->cgwb_tree, GFP_ATOMIC);
665 bdi->cgwb_congested_tree = RB_ROOT;
666 atomic_set(&bdi->usage_cnt, 1);
Tejun Heoa13f35e2015-07-02 08:44:34 -0600667
668 ret = wb_init(&bdi->wb, bdi, 1, GFP_KERNEL);
669 if (!ret) {
670 bdi->wb.memcg_css = mem_cgroup_root_css;
671 bdi->wb.blkcg_css = blkcg_root_css;
672 }
673 return ret;
Tejun Heo52ebea72015-05-22 17:13:37 -0400674}
675
676static void cgwb_bdi_destroy(struct backing_dev_info *bdi)
677{
678 struct radix_tree_iter iter;
Tejun Heoa20135f2015-07-01 20:53:37 -0400679 struct bdi_writeback_congested *congested, *congested_n;
Tejun Heo52ebea72015-05-22 17:13:37 -0400680 void **slot;
681
682 WARN_ON(test_bit(WB_registered, &bdi->wb.state));
683
684 spin_lock_irq(&cgwb_lock);
Tejun Heoa20135f2015-07-01 20:53:37 -0400685
Tejun Heo52ebea72015-05-22 17:13:37 -0400686 radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0)
687 cgwb_kill(*slot);
Tejun Heoa20135f2015-07-01 20:53:37 -0400688
689 rbtree_postorder_for_each_entry_safe(congested, congested_n,
690 &bdi->cgwb_congested_tree, rb_node) {
691 rb_erase(&congested->rb_node, &bdi->cgwb_congested_tree);
692 congested->bdi = NULL; /* mark @congested unlinked */
693 }
694
Tejun Heo52ebea72015-05-22 17:13:37 -0400695 spin_unlock_irq(&cgwb_lock);
696
697 /*
698 * All cgwb's and their congested states must be shutdown and
699 * released before returning. Drain the usage counter to wait for
700 * all cgwb's and cgwb_congested's ever created on @bdi.
701 */
702 atomic_dec(&bdi->usage_cnt);
703 wait_event(cgwb_release_wait, !atomic_read(&bdi->usage_cnt));
704}
705
706/**
707 * wb_memcg_offline - kill all wb's associated with a memcg being offlined
708 * @memcg: memcg being offlined
709 *
710 * Also prevents creation of any new wb's associated with @memcg.
711 */
712void wb_memcg_offline(struct mem_cgroup *memcg)
713{
714 LIST_HEAD(to_destroy);
715 struct list_head *memcg_cgwb_list = mem_cgroup_cgwb_list(memcg);
716 struct bdi_writeback *wb, *next;
717
718 spin_lock_irq(&cgwb_lock);
719 list_for_each_entry_safe(wb, next, memcg_cgwb_list, memcg_node)
720 cgwb_kill(wb);
721 memcg_cgwb_list->next = NULL; /* prevent new wb's */
722 spin_unlock_irq(&cgwb_lock);
723}
724
725/**
726 * wb_blkcg_offline - kill all wb's associated with a blkcg being offlined
727 * @blkcg: blkcg being offlined
728 *
729 * Also prevents creation of any new wb's associated with @blkcg.
730 */
731void wb_blkcg_offline(struct blkcg *blkcg)
732{
733 LIST_HEAD(to_destroy);
734 struct bdi_writeback *wb, *next;
735
736 spin_lock_irq(&cgwb_lock);
737 list_for_each_entry_safe(wb, next, &blkcg->cgwb_list, blkcg_node)
738 cgwb_kill(wb);
739 blkcg->cgwb_list.next = NULL; /* prevent new wb's */
740 spin_unlock_irq(&cgwb_lock);
741}
742
743#else /* CONFIG_CGROUP_WRITEBACK */
744
Tejun Heoa13f35e2015-07-02 08:44:34 -0600745static int cgwb_bdi_init(struct backing_dev_info *bdi)
746{
747 int err;
748
749 bdi->wb_congested = kzalloc(sizeof(*bdi->wb_congested), GFP_KERNEL);
750 if (!bdi->wb_congested)
751 return -ENOMEM;
752
753 err = wb_init(&bdi->wb, bdi, 1, GFP_KERNEL);
754 if (err) {
755 kfree(bdi->wb_congested);
756 return err;
757 }
758 return 0;
759}
760
Tejun Heo52ebea72015-05-22 17:13:37 -0400761static void cgwb_bdi_destroy(struct backing_dev_info *bdi) { }
762
763#endif /* CONFIG_CGROUP_WRITEBACK */
764
Peter Zijlstrab2e8fb62007-10-16 23:25:47 -0700765int bdi_init(struct backing_dev_info *bdi)
766{
Peter Zijlstracf0ca9f2008-04-30 00:54:32 -0700767 bdi->dev = NULL;
768
Peter Zijlstra189d3c42008-04-30 00:54:35 -0700769 bdi->min_ratio = 0;
Peter Zijlstraa42dde02008-04-30 00:54:36 -0700770 bdi->max_ratio = 100;
Jan Karaeb608e32012-05-24 18:59:11 +0200771 bdi->max_prop_frac = FPROP_FRAC_BASE;
Jens Axboe66f3b8e2009-09-02 09:19:46 +0200772 INIT_LIST_HEAD(&bdi->bdi_list);
Tejun Heocc395d72015-05-22 17:13:58 -0400773 init_waitqueue_head(&bdi->wb_waitq);
Jens Axboe03ba3782009-09-09 09:08:54 +0200774
Tejun Heoa13f35e2015-07-02 08:44:34 -0600775 return cgwb_bdi_init(bdi);
Peter Zijlstrab2e8fb62007-10-16 23:25:47 -0700776}
777EXPORT_SYMBOL(bdi_init);
778
Peter Zijlstrab2e8fb62007-10-16 23:25:47 -0700779int bdi_register(struct backing_dev_info *bdi, struct device *parent,
780 const char *fmt, ...)
781{
782 va_list args;
783 struct device *dev;
784
785 if (bdi->dev) /* The driver needs to use separate queues per device */
786 return 0;
787
788 va_start(args, fmt);
789 dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);
Peter Zijlstracf0ca9f2008-04-30 00:54:32 -0700790 va_end(args);
791 if (IS_ERR(dev))
Peter Zijlstrab2e8fb62007-10-16 23:25:47 -0700792 return PTR_ERR(dev);
793
Peter Zijlstra04fbfdc2007-10-16 23:25:50 -0700794 bdi->dev = dev;
795
Peter Zijlstrab2e8fb62007-10-16 23:25:47 -0700796 bdi_debug_register(bdi, dev_name(dev));
Tejun Heo46100072015-05-22 17:13:31 -0400797 set_bit(WB_registered, &bdi->wb.state);
Andrew Morton3fcfab12006-10-19 23:28:16 -0700798
799 spin_lock_bh(&bdi_lock);
800 list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
801 spin_unlock_bh(&bdi_lock);
802
803 trace_writeback_bdi_register(bdi);
804 return 0;
805}
806EXPORT_SYMBOL(bdi_register);
807
808int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
809{
810 return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
811}
812EXPORT_SYMBOL(bdi_register_dev);
813
814/*
Tejun Heo46100072015-05-22 17:13:31 -0400815 * Remove bdi from bdi_list, and ensure that it is no longer visible
Andrew Morton3fcfab12006-10-19 23:28:16 -0700816 */
Tejun Heo46100072015-05-22 17:13:31 -0400817static void bdi_remove_from_list(struct backing_dev_info *bdi)
Andrew Morton3fcfab12006-10-19 23:28:16 -0700818{
Tejun Heo46100072015-05-22 17:13:31 -0400819 spin_lock_bh(&bdi_lock);
820 list_del_rcu(&bdi->bdi_list);
821 spin_unlock_bh(&bdi_lock);
Andrew Morton3fcfab12006-10-19 23:28:16 -0700822
Tejun Heo46100072015-05-22 17:13:31 -0400823 synchronize_rcu_expedited();
Andrew Morton3fcfab12006-10-19 23:28:16 -0700824}
825
Andrew Morton3fcfab12006-10-19 23:28:16 -0700826void bdi_destroy(struct backing_dev_info *bdi)
827{
Tejun Heof0054bb2015-05-22 17:13:30 -0400828 /* make sure nobody finds us on the bdi_list anymore */
829 bdi_remove_from_list(bdi);
830 wb_shutdown(&bdi->wb);
Tejun Heo52ebea72015-05-22 17:13:37 -0400831 cgwb_bdi_destroy(bdi);
Rabin Vincent7a401a92011-11-11 13:29:04 +0100832
Christoph Hellwigc4db59d2015-01-20 14:05:00 -0700833 if (bdi->dev) {
834 bdi_debug_unregister(bdi);
835 device_unregister(bdi->dev);
836 bdi->dev = NULL;
837 }
838
Tejun Heof0054bb2015-05-22 17:13:30 -0400839 wb_exit(&bdi->wb);
Andrew Morton3fcfab12006-10-19 23:28:16 -0700840}
841EXPORT_SYMBOL(bdi_destroy);
842
Jens Axboec3c53202010-04-22 11:37:01 +0200843/*
844 * For use from filesystems to quickly init and register a bdi associated
845 * with dirty writeback
846 */
Christoph Hellwigb4caecd2015-01-14 10:42:32 +0100847int bdi_setup_and_register(struct backing_dev_info *bdi, char *name)
Jens Axboec3c53202010-04-22 11:37:01 +0200848{
Jens Axboec3c53202010-04-22 11:37:01 +0200849 int err;
850
851 bdi->name = name;
Christoph Hellwigb4caecd2015-01-14 10:42:32 +0100852 bdi->capabilities = 0;
Jens Axboec3c53202010-04-22 11:37:01 +0200853 err = bdi_init(bdi);
854 if (err)
855 return err;
856
Kees Cook02aa2a32013-07-03 15:04:56 -0700857 err = bdi_register(bdi, NULL, "%.28s-%ld", name,
858 atomic_long_inc_return(&bdi_seq));
Jens Axboec3c53202010-04-22 11:37:01 +0200859 if (err) {
860 bdi_destroy(bdi);
861 return err;
862 }
863
864 return 0;
865}
866EXPORT_SYMBOL(bdi_setup_and_register);
867
Andrew Morton3fcfab12006-10-19 23:28:16 -0700868static wait_queue_head_t congestion_wqh[2] = {
869 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
870 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
871 };
Tejun Heoec8a6f22015-05-22 17:13:41 -0400872static atomic_t nr_wb_congested[2];
Andrew Morton3fcfab12006-10-19 23:28:16 -0700873
Tejun Heoec8a6f22015-05-22 17:13:41 -0400874void clear_wb_congested(struct bdi_writeback_congested *congested, int sync)
Andrew Morton3fcfab12006-10-19 23:28:16 -0700875{
Jens Axboe1faa16d2009-04-06 14:48:01 +0200876 wait_queue_head_t *wqh = &congestion_wqh[sync];
Tejun Heoec8a6f22015-05-22 17:13:41 -0400877 enum wb_state bit;
Andrew Morton3fcfab12006-10-19 23:28:16 -0700878
Tejun Heo44522262015-05-22 17:13:26 -0400879 bit = sync ? WB_sync_congested : WB_async_congested;
Tejun Heoec8a6f22015-05-22 17:13:41 -0400880 if (test_and_clear_bit(bit, &congested->state))
881 atomic_dec(&nr_wb_congested[sync]);
Peter Zijlstra4e857c52014-03-17 18:06:10 +0100882 smp_mb__after_atomic();
Andrew Morton3fcfab12006-10-19 23:28:16 -0700883 if (waitqueue_active(wqh))
884 wake_up(wqh);
885}
Tejun Heoec8a6f22015-05-22 17:13:41 -0400886EXPORT_SYMBOL(clear_wb_congested);
Andrew Morton3fcfab12006-10-19 23:28:16 -0700887
Tejun Heoec8a6f22015-05-22 17:13:41 -0400888void set_wb_congested(struct bdi_writeback_congested *congested, int sync)
Andrew Morton3fcfab12006-10-19 23:28:16 -0700889{
Tejun Heo44522262015-05-22 17:13:26 -0400890 enum wb_state bit;
Andrew Morton3fcfab12006-10-19 23:28:16 -0700891
Tejun Heo44522262015-05-22 17:13:26 -0400892 bit = sync ? WB_sync_congested : WB_async_congested;
Tejun Heoec8a6f22015-05-22 17:13:41 -0400893 if (!test_and_set_bit(bit, &congested->state))
894 atomic_inc(&nr_wb_congested[sync]);
Andrew Morton3fcfab12006-10-19 23:28:16 -0700895}
Tejun Heoec8a6f22015-05-22 17:13:41 -0400896EXPORT_SYMBOL(set_wb_congested);
Andrew Morton3fcfab12006-10-19 23:28:16 -0700897
898/**
899 * congestion_wait - wait for a backing_dev to become uncongested
Jens Axboe8aa7e842009-07-09 14:52:32 +0200900 * @sync: SYNC or ASYNC IO
Andrew Morton3fcfab12006-10-19 23:28:16 -0700901 * @timeout: timeout in jiffies
902 *
903 * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
904 * write congestion. If no backing_devs are congested then just wait for the
905 * next write to be completed.
906 */
Jens Axboe8aa7e842009-07-09 14:52:32 +0200907long congestion_wait(int sync, long timeout)
Andrew Morton3fcfab12006-10-19 23:28:16 -0700908{
909 long ret;
Mel Gorman52bb9192010-10-26 14:21:41 -0700910 unsigned long start = jiffies;
Andrew Morton3fcfab12006-10-19 23:28:16 -0700911 DEFINE_WAIT(wait);
Jens Axboe8aa7e842009-07-09 14:52:32 +0200912 wait_queue_head_t *wqh = &congestion_wqh[sync];
Andrew Morton3fcfab12006-10-19 23:28:16 -0700913
914 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
915 ret = io_schedule_timeout(timeout);
916 finish_wait(wqh, &wait);
Mel Gorman52bb9192010-10-26 14:21:41 -0700917
918 trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
919 jiffies_to_usecs(jiffies - start));
920
Andrew Morton3fcfab12006-10-19 23:28:16 -0700921 return ret;
922}
923EXPORT_SYMBOL(congestion_wait);
924
Mel Gorman0e093d992010-10-26 14:21:45 -0700925/**
926 * wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a zone to complete writes
927 * @zone: A zone to check if it is heavily congested
928 * @sync: SYNC or ASYNC IO
929 * @timeout: timeout in jiffies
930 *
931 * In the event of a congested backing_dev (any backing_dev) and the given
932 * @zone has experienced recent congestion, this waits for up to @timeout
933 * jiffies for either a BDI to exit congestion of the given @sync queue
934 * or a write to complete.
935 *
Lucas De Marchi25985ed2011-03-30 22:57:33 -0300936 * In the absence of zone congestion, cond_resched() is called to yield
Mel Gorman0e093d992010-10-26 14:21:45 -0700937 * the processor if necessary but otherwise does not sleep.
938 *
939 * The return value is 0 if the sleep is for the full timeout. Otherwise,
940 * it is the number of jiffies that were still remaining when the function
941 * returned. return_value == timeout implies the function did not sleep.
942 */
943long wait_iff_congested(struct zone *zone, int sync, long timeout)
944{
945 long ret;
946 unsigned long start = jiffies;
947 DEFINE_WAIT(wait);
948 wait_queue_head_t *wqh = &congestion_wqh[sync];
949
950 /*
951 * If there is no congestion, or heavy congestion is not being
952 * encountered in the current zone, yield if necessary instead
953 * of sleeping on the congestion queue
954 */
Tejun Heoec8a6f22015-05-22 17:13:41 -0400955 if (atomic_read(&nr_wb_congested[sync]) == 0 ||
Johannes Weiner57054652014-10-09 15:28:17 -0700956 !test_bit(ZONE_CONGESTED, &zone->flags)) {
Mel Gorman0e093d992010-10-26 14:21:45 -0700957 cond_resched();
958
959 /* In case we scheduled, work out time remaining */
960 ret = timeout - (jiffies - start);
961 if (ret < 0)
962 ret = 0;
963
964 goto out;
965 }
966
967 /* Sleep until uncongested or a write happens */
968 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
969 ret = io_schedule_timeout(timeout);
970 finish_wait(wqh, &wait);
971
972out:
973 trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout),
974 jiffies_to_usecs(jiffies - start));
975
976 return ret;
977}
978EXPORT_SYMBOL(wait_iff_congested);
Wanpeng Li3965c9a2012-07-31 16:41:52 -0700979
980int pdflush_proc_obsolete(struct ctl_table *table, int write,
981 void __user *buffer, size_t *lenp, loff_t *ppos)
982{
983 char kbuf[] = "0\n";
984
Chen Gang4c3bffc2013-09-11 14:22:44 -0700985 if (*ppos || *lenp < sizeof(kbuf)) {
Wanpeng Li3965c9a2012-07-31 16:41:52 -0700986 *lenp = 0;
987 return 0;
988 }
989
990 if (copy_to_user(buffer, kbuf, sizeof(kbuf)))
991 return -EFAULT;
992 printk_once(KERN_WARNING "%s exported in /proc is scheduled for removal\n",
993 table->procname);
994
995 *lenp = 2;
996 *ppos += *lenp;
997 return 2;
998}