1 // SPDX-License-Identifier: GPL-2.0-only
3 #include <linux/wait.h>
4 #include <linux/rbtree.h>
5 #include <linux/backing-dev.h>
6 #include <linux/kthread.h>
7 #include <linux/freezer.h>
9 #include <linux/pagemap.h>
11 #include <linux/sched.h>
12 #include <linux/module.h>
13 #include <linux/writeback.h>
14 #include <linux/device.h>
15 #include <trace/events/writeback.h>
17 struct backing_dev_info noop_backing_dev_info;
18 EXPORT_SYMBOL_GPL(noop_backing_dev_info);
20 static struct class *bdi_class;
21 static const char *bdi_unknown_name = "(unknown)";
24 * bdi_lock protects bdi_tree and updates to bdi_list. bdi_list has RCU
25 * reader side locking.
27 DEFINE_SPINLOCK(bdi_lock);
28 static u64 bdi_id_cursor;
29 static struct rb_root bdi_tree = RB_ROOT;
32 /* bdi_wq serves all asynchronous writeback tasks */
33 struct workqueue_struct *bdi_wq;
35 #define K(x) ((x) << (PAGE_SHIFT - 10))
37 #ifdef CONFIG_DEBUG_FS
38 #include <linux/debugfs.h>
39 #include <linux/seq_file.h>
41 static struct dentry *bdi_debug_root;
43 static void bdi_debug_init(void)
45 bdi_debug_root = debugfs_create_dir("bdi", NULL);
48 static int bdi_debug_stats_show(struct seq_file *m, void *v)
50 struct backing_dev_info *bdi = m->private;
51 struct bdi_writeback *wb = &bdi->wb;
52 unsigned long background_thresh;
53 unsigned long dirty_thresh;
54 unsigned long wb_thresh;
55 unsigned long nr_dirty, nr_io, nr_more_io, nr_dirty_time;
58 nr_dirty = nr_io = nr_more_io = nr_dirty_time = 0;
59 spin_lock(&wb->list_lock);
60 list_for_each_entry(inode, &wb->b_dirty, i_io_list)
62 list_for_each_entry(inode, &wb->b_io, i_io_list)
64 list_for_each_entry(inode, &wb->b_more_io, i_io_list)
66 list_for_each_entry(inode, &wb->b_dirty_time, i_io_list)
67 if (inode->i_state & I_DIRTY_TIME)
69 spin_unlock(&wb->list_lock);
71 global_dirty_limits(&background_thresh, &dirty_thresh);
72 wb_thresh = wb_calc_thresh(wb, dirty_thresh);
75 "BdiWriteback: %10lu kB\n"
76 "BdiReclaimable: %10lu kB\n"
77 "BdiDirtyThresh: %10lu kB\n"
78 "DirtyThresh: %10lu kB\n"
79 "BackgroundThresh: %10lu kB\n"
80 "BdiDirtied: %10lu kB\n"
81 "BdiWritten: %10lu kB\n"
82 "BdiWriteBandwidth: %10lu kBps\n"
86 "b_dirty_time: %10lu\n"
89 (unsigned long) K(wb_stat(wb, WB_WRITEBACK)),
90 (unsigned long) K(wb_stat(wb, WB_RECLAIMABLE)),
94 (unsigned long) K(wb_stat(wb, WB_DIRTIED)),
95 (unsigned long) K(wb_stat(wb, WB_WRITTEN)),
96 (unsigned long) K(wb->write_bandwidth),
101 !list_empty(&bdi->bdi_list), bdi->wb.state);
105 DEFINE_SHOW_ATTRIBUTE(bdi_debug_stats);
107 static void bdi_debug_register(struct backing_dev_info *bdi, const char *name)
109 bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);
111 debugfs_create_file("stats", 0444, bdi->debug_dir, bdi,
112 &bdi_debug_stats_fops);
115 static void bdi_debug_unregister(struct backing_dev_info *bdi)
117 debugfs_remove_recursive(bdi->debug_dir);
120 static inline void bdi_debug_init(void)
123 static inline void bdi_debug_register(struct backing_dev_info *bdi,
127 static inline void bdi_debug_unregister(struct backing_dev_info *bdi)
132 static ssize_t read_ahead_kb_store(struct device *dev,
133 struct device_attribute *attr,
134 const char *buf, size_t count)
136 struct backing_dev_info *bdi = dev_get_drvdata(dev);
137 unsigned long read_ahead_kb;
140 ret = kstrtoul(buf, 10, &read_ahead_kb);
144 bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10);
149 #define BDI_SHOW(name, expr) \
150 static ssize_t name##_show(struct device *dev, \
151 struct device_attribute *attr, char *buf) \
153 struct backing_dev_info *bdi = dev_get_drvdata(dev); \
155 return sysfs_emit(buf, "%lld\n", (long long)expr); \
157 static DEVICE_ATTR_RW(name);
159 BDI_SHOW(read_ahead_kb, K(bdi->ra_pages))
161 static ssize_t min_ratio_store(struct device *dev,
162 struct device_attribute *attr, const char *buf, size_t count)
164 struct backing_dev_info *bdi = dev_get_drvdata(dev);
168 ret = kstrtouint(buf, 10, &ratio);
172 ret = bdi_set_min_ratio(bdi, ratio);
178 BDI_SHOW(min_ratio, bdi->min_ratio)
180 static ssize_t max_ratio_store(struct device *dev,
181 struct device_attribute *attr, const char *buf, size_t count)
183 struct backing_dev_info *bdi = dev_get_drvdata(dev);
187 ret = kstrtouint(buf, 10, &ratio);
191 ret = bdi_set_max_ratio(bdi, ratio);
197 BDI_SHOW(max_ratio, bdi->max_ratio)
199 static ssize_t stable_pages_required_show(struct device *dev,
200 struct device_attribute *attr,
204 "the stable_pages_required attribute has been removed. Use the stable_writes queue attribute instead.\n");
205 return sysfs_emit(buf, "%d\n", 0);
207 static DEVICE_ATTR_RO(stable_pages_required);
209 static struct attribute *bdi_dev_attrs[] = {
210 &dev_attr_read_ahead_kb.attr,
211 &dev_attr_min_ratio.attr,
212 &dev_attr_max_ratio.attr,
213 &dev_attr_stable_pages_required.attr,
216 ATTRIBUTE_GROUPS(bdi_dev);
218 static __init int bdi_class_init(void)
220 bdi_class = class_create(THIS_MODULE, "bdi");
221 if (IS_ERR(bdi_class))
222 return PTR_ERR(bdi_class);
224 bdi_class->dev_groups = bdi_dev_groups;
229 postcore_initcall(bdi_class_init);
231 static int bdi_init(struct backing_dev_info *bdi);
233 static int __init default_bdi_init(void)
237 bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_UNBOUND |
242 err = bdi_init(&noop_backing_dev_info);
246 subsys_initcall(default_bdi_init);
249 * This function is used when the first inode for this wb is marked dirty. It
250 * wakes-up the corresponding bdi thread which should then take care of the
251 * periodic background write-out of dirty inodes. Since the write-out would
252 * starts only 'dirty_writeback_interval' centisecs from now anyway, we just
253 * set up a timer which wakes the bdi thread up later.
255 * Note, we wouldn't bother setting up the timer, but this function is on the
256 * fast-path (used by '__mark_inode_dirty()'), so we save few context switches
257 * by delaying the wake-up.
259 * We have to be careful not to postpone flush work if it is scheduled for
260 * earlier. Thus we use queue_delayed_work().
262 void wb_wakeup_delayed(struct bdi_writeback *wb)
264 unsigned long timeout;
266 timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
267 spin_lock_bh(&wb->work_lock);
268 if (test_bit(WB_registered, &wb->state))
269 queue_delayed_work(bdi_wq, &wb->dwork, timeout);
270 spin_unlock_bh(&wb->work_lock);
274 * Initial write bandwidth: 100 MB/s
276 #define INIT_BW (100 << (20 - PAGE_SHIFT))
278 static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi,
283 memset(wb, 0, sizeof(*wb));
288 wb->last_old_flush = jiffies;
289 INIT_LIST_HEAD(&wb->b_dirty);
290 INIT_LIST_HEAD(&wb->b_io);
291 INIT_LIST_HEAD(&wb->b_more_io);
292 INIT_LIST_HEAD(&wb->b_dirty_time);
293 spin_lock_init(&wb->list_lock);
295 wb->bw_time_stamp = jiffies;
296 wb->balanced_dirty_ratelimit = INIT_BW;
297 wb->dirty_ratelimit = INIT_BW;
298 wb->write_bandwidth = INIT_BW;
299 wb->avg_write_bandwidth = INIT_BW;
301 spin_lock_init(&wb->work_lock);
302 INIT_LIST_HEAD(&wb->work_list);
303 INIT_DELAYED_WORK(&wb->dwork, wb_workfn);
304 wb->dirty_sleep = jiffies;
306 err = fprop_local_init_percpu(&wb->completions, gfp);
310 for (i = 0; i < NR_WB_STAT_ITEMS; i++) {
311 err = percpu_counter_init(&wb->stat[i], 0, gfp);
313 goto out_destroy_stat;
320 percpu_counter_destroy(&wb->stat[i]);
321 fprop_local_destroy_percpu(&wb->completions);
328 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb);
331 * Remove bdi from the global list and shutdown any threads we have running
333 static void wb_shutdown(struct bdi_writeback *wb)
335 /* Make sure nobody queues further work */
336 spin_lock_bh(&wb->work_lock);
337 if (!test_and_clear_bit(WB_registered, &wb->state)) {
338 spin_unlock_bh(&wb->work_lock);
341 spin_unlock_bh(&wb->work_lock);
343 cgwb_remove_from_bdi_list(wb);
345 * Drain work list and shutdown the delayed_work. !WB_registered
346 * tells wb_workfn() that @wb is dying and its work_list needs to
347 * be drained no matter what.
349 mod_delayed_work(bdi_wq, &wb->dwork, 0);
350 flush_delayed_work(&wb->dwork);
351 WARN_ON(!list_empty(&wb->work_list));
354 static void wb_exit(struct bdi_writeback *wb)
358 WARN_ON(delayed_work_pending(&wb->dwork));
360 for (i = 0; i < NR_WB_STAT_ITEMS; i++)
361 percpu_counter_destroy(&wb->stat[i]);
363 fprop_local_destroy_percpu(&wb->completions);
364 if (wb != &wb->bdi->wb)
368 #ifdef CONFIG_CGROUP_WRITEBACK
370 #include <linux/memcontrol.h>
373 * cgwb_lock protects bdi->cgwb_tree, blkcg->cgwb_list, and memcg->cgwb_list.
374 * bdi->cgwb_tree is also RCU protected.
376 static DEFINE_SPINLOCK(cgwb_lock);
377 static struct workqueue_struct *cgwb_release_wq;
379 static void cgwb_release_workfn(struct work_struct *work)
381 struct bdi_writeback *wb = container_of(work, struct bdi_writeback,
383 struct blkcg *blkcg = css_to_blkcg(wb->blkcg_css);
385 mutex_lock(&wb->bdi->cgwb_release_mutex);
388 css_put(wb->memcg_css);
389 css_put(wb->blkcg_css);
390 mutex_unlock(&wb->bdi->cgwb_release_mutex);
392 /* triggers blkg destruction if no online users left */
393 blkcg_unpin_online(blkcg);
395 fprop_local_destroy_percpu(&wb->memcg_completions);
396 percpu_ref_exit(&wb->refcnt);
401 static void cgwb_release(struct percpu_ref *refcnt)
403 struct bdi_writeback *wb = container_of(refcnt, struct bdi_writeback,
405 queue_work(cgwb_release_wq, &wb->release_work);
408 static void cgwb_kill(struct bdi_writeback *wb)
410 lockdep_assert_held(&cgwb_lock);
412 WARN_ON(!radix_tree_delete(&wb->bdi->cgwb_tree, wb->memcg_css->id));
413 list_del(&wb->memcg_node);
414 list_del(&wb->blkcg_node);
415 percpu_ref_kill(&wb->refcnt);
418 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
420 spin_lock_irq(&cgwb_lock);
421 list_del_rcu(&wb->bdi_node);
422 spin_unlock_irq(&cgwb_lock);
425 static int cgwb_create(struct backing_dev_info *bdi,
426 struct cgroup_subsys_state *memcg_css, gfp_t gfp)
428 struct mem_cgroup *memcg;
429 struct cgroup_subsys_state *blkcg_css;
431 struct list_head *memcg_cgwb_list, *blkcg_cgwb_list;
432 struct bdi_writeback *wb;
436 memcg = mem_cgroup_from_css(memcg_css);
437 blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
438 blkcg = css_to_blkcg(blkcg_css);
439 memcg_cgwb_list = &memcg->cgwb_list;
440 blkcg_cgwb_list = &blkcg->cgwb_list;
442 /* look up again under lock and discard on blkcg mismatch */
443 spin_lock_irqsave(&cgwb_lock, flags);
444 wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
445 if (wb && wb->blkcg_css != blkcg_css) {
449 spin_unlock_irqrestore(&cgwb_lock, flags);
453 /* need to create a new one */
454 wb = kmalloc(sizeof(*wb), gfp);
460 ret = wb_init(wb, bdi, gfp);
464 ret = percpu_ref_init(&wb->refcnt, cgwb_release, 0, gfp);
468 ret = fprop_local_init_percpu(&wb->memcg_completions, gfp);
472 wb->memcg_css = memcg_css;
473 wb->blkcg_css = blkcg_css;
474 INIT_WORK(&wb->release_work, cgwb_release_workfn);
475 set_bit(WB_registered, &wb->state);
478 * The root wb determines the registered state of the whole bdi and
479 * memcg_cgwb_list and blkcg_cgwb_list's next pointers indicate
480 * whether they're still online. Don't link @wb if any is dead.
481 * See wb_memcg_offline() and wb_blkcg_offline().
484 spin_lock_irqsave(&cgwb_lock, flags);
485 if (test_bit(WB_registered, &bdi->wb.state) &&
486 blkcg_cgwb_list->next && memcg_cgwb_list->next) {
487 /* we might have raced another instance of this function */
488 ret = radix_tree_insert(&bdi->cgwb_tree, memcg_css->id, wb);
490 list_add_tail_rcu(&wb->bdi_node, &bdi->wb_list);
491 list_add(&wb->memcg_node, memcg_cgwb_list);
492 list_add(&wb->blkcg_node, blkcg_cgwb_list);
493 blkcg_pin_online(blkcg);
498 spin_unlock_irqrestore(&cgwb_lock, flags);
507 fprop_local_destroy_percpu(&wb->memcg_completions);
509 percpu_ref_exit(&wb->refcnt);
520 * wb_get_lookup - get wb for a given memcg
522 * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
524 * Try to get the wb for @memcg_css on @bdi. The returned wb has its
525 * refcount incremented.
527 * This function uses css_get() on @memcg_css and thus expects its refcnt
528 * to be positive on invocation. IOW, rcu_read_lock() protection on
529 * @memcg_css isn't enough. try_get it before calling this function.
531 * A wb is keyed by its associated memcg. As blkcg implicitly enables
532 * memcg on the default hierarchy, memcg association is guaranteed to be
533 * more specific (equal or descendant to the associated blkcg) and thus can
534 * identify both the memcg and blkcg associations.
536 * Because the blkcg associated with a memcg may change as blkcg is enabled
537 * and disabled closer to root in the hierarchy, each wb keeps track of
538 * both the memcg and blkcg associated with it and verifies the blkcg on
539 * each lookup. On mismatch, the existing wb is discarded and a new one is
542 struct bdi_writeback *wb_get_lookup(struct backing_dev_info *bdi,
543 struct cgroup_subsys_state *memcg_css)
545 struct bdi_writeback *wb;
547 if (!memcg_css->parent)
551 wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
553 struct cgroup_subsys_state *blkcg_css;
555 /* see whether the blkcg association has changed */
556 blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
557 if (unlikely(wb->blkcg_css != blkcg_css || !wb_tryget(wb)))
567 * wb_get_create - get wb for a given memcg, create if necessary
569 * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
570 * @gfp: allocation mask to use
572 * Try to get the wb for @memcg_css on @bdi. If it doesn't exist, try to
573 * create one. See wb_get_lookup() for more details.
575 struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
576 struct cgroup_subsys_state *memcg_css,
579 struct bdi_writeback *wb;
581 might_sleep_if(gfpflags_allow_blocking(gfp));
583 if (!memcg_css->parent)
587 wb = wb_get_lookup(bdi, memcg_css);
588 } while (!wb && !cgwb_create(bdi, memcg_css, gfp));
593 static int cgwb_bdi_init(struct backing_dev_info *bdi)
597 INIT_RADIX_TREE(&bdi->cgwb_tree, GFP_ATOMIC);
598 mutex_init(&bdi->cgwb_release_mutex);
599 init_rwsem(&bdi->wb_switch_rwsem);
601 ret = wb_init(&bdi->wb, bdi, GFP_KERNEL);
603 bdi->wb.memcg_css = &root_mem_cgroup->css;
604 bdi->wb.blkcg_css = blkcg_root_css;
609 static void cgwb_bdi_unregister(struct backing_dev_info *bdi)
611 struct radix_tree_iter iter;
613 struct bdi_writeback *wb;
615 WARN_ON(test_bit(WB_registered, &bdi->wb.state));
617 spin_lock_irq(&cgwb_lock);
618 radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0)
620 spin_unlock_irq(&cgwb_lock);
622 mutex_lock(&bdi->cgwb_release_mutex);
623 spin_lock_irq(&cgwb_lock);
624 while (!list_empty(&bdi->wb_list)) {
625 wb = list_first_entry(&bdi->wb_list, struct bdi_writeback,
627 spin_unlock_irq(&cgwb_lock);
629 spin_lock_irq(&cgwb_lock);
631 spin_unlock_irq(&cgwb_lock);
632 mutex_unlock(&bdi->cgwb_release_mutex);
636 * wb_memcg_offline - kill all wb's associated with a memcg being offlined
637 * @memcg: memcg being offlined
639 * Also prevents creation of any new wb's associated with @memcg.
641 void wb_memcg_offline(struct mem_cgroup *memcg)
643 struct list_head *memcg_cgwb_list = &memcg->cgwb_list;
644 struct bdi_writeback *wb, *next;
646 spin_lock_irq(&cgwb_lock);
647 list_for_each_entry_safe(wb, next, memcg_cgwb_list, memcg_node)
649 memcg_cgwb_list->next = NULL; /* prevent new wb's */
650 spin_unlock_irq(&cgwb_lock);
654 * wb_blkcg_offline - kill all wb's associated with a blkcg being offlined
655 * @blkcg: blkcg being offlined
657 * Also prevents creation of any new wb's associated with @blkcg.
659 void wb_blkcg_offline(struct blkcg *blkcg)
661 struct bdi_writeback *wb, *next;
663 spin_lock_irq(&cgwb_lock);
664 list_for_each_entry_safe(wb, next, &blkcg->cgwb_list, blkcg_node)
666 blkcg->cgwb_list.next = NULL; /* prevent new wb's */
667 spin_unlock_irq(&cgwb_lock);
670 static void cgwb_bdi_register(struct backing_dev_info *bdi)
672 spin_lock_irq(&cgwb_lock);
673 list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
674 spin_unlock_irq(&cgwb_lock);
677 static int __init cgwb_init(void)
680 * There can be many concurrent release work items overwhelming
681 * system_wq. Put them in a separate wq and limit concurrency.
682 * There's no point in executing many of these in parallel.
684 cgwb_release_wq = alloc_workqueue("cgwb_release", 0, 1);
685 if (!cgwb_release_wq)
690 subsys_initcall(cgwb_init);
692 #else /* CONFIG_CGROUP_WRITEBACK */
694 static int cgwb_bdi_init(struct backing_dev_info *bdi)
696 return wb_init(&bdi->wb, bdi, GFP_KERNEL);
699 static void cgwb_bdi_unregister(struct backing_dev_info *bdi) { }
701 static void cgwb_bdi_register(struct backing_dev_info *bdi)
703 list_add_tail_rcu(&bdi->wb.bdi_node, &bdi->wb_list);
706 static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb)
708 list_del_rcu(&wb->bdi_node);
711 #endif /* CONFIG_CGROUP_WRITEBACK */
713 static int bdi_init(struct backing_dev_info *bdi)
719 kref_init(&bdi->refcnt);
721 bdi->max_ratio = 100;
722 bdi->max_prop_frac = FPROP_FRAC_BASE;
723 INIT_LIST_HEAD(&bdi->bdi_list);
724 INIT_LIST_HEAD(&bdi->wb_list);
725 init_waitqueue_head(&bdi->wb_waitq);
727 ret = cgwb_bdi_init(bdi);
732 struct backing_dev_info *bdi_alloc(int node_id)
734 struct backing_dev_info *bdi;
736 bdi = kzalloc_node(sizeof(*bdi), GFP_KERNEL, node_id);
744 bdi->capabilities = BDI_CAP_WRITEBACK | BDI_CAP_WRITEBACK_ACCT;
745 bdi->ra_pages = VM_READAHEAD_PAGES;
746 bdi->io_pages = VM_READAHEAD_PAGES;
749 EXPORT_SYMBOL(bdi_alloc);
751 static struct rb_node **bdi_lookup_rb_node(u64 id, struct rb_node **parentp)
753 struct rb_node **p = &bdi_tree.rb_node;
754 struct rb_node *parent = NULL;
755 struct backing_dev_info *bdi;
757 lockdep_assert_held(&bdi_lock);
761 bdi = rb_entry(parent, struct backing_dev_info, rb_node);
765 else if (bdi->id < id)
777 * bdi_get_by_id - lookup and get bdi from its id
778 * @id: bdi id to lookup
780 * Find bdi matching @id and get it. Returns NULL if the matching bdi
781 * doesn't exist or is already unregistered.
783 struct backing_dev_info *bdi_get_by_id(u64 id)
785 struct backing_dev_info *bdi = NULL;
788 spin_lock_bh(&bdi_lock);
789 p = bdi_lookup_rb_node(id, NULL);
791 bdi = rb_entry(*p, struct backing_dev_info, rb_node);
794 spin_unlock_bh(&bdi_lock);
799 int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, va_list args)
802 struct rb_node *parent, **p;
804 if (bdi->dev) /* The driver needs to use separate queues per device */
807 vsnprintf(bdi->dev_name, sizeof(bdi->dev_name), fmt, args);
808 dev = device_create(bdi_class, NULL, MKDEV(0, 0), bdi, bdi->dev_name);
812 cgwb_bdi_register(bdi);
815 bdi_debug_register(bdi, dev_name(dev));
816 set_bit(WB_registered, &bdi->wb.state);
818 spin_lock_bh(&bdi_lock);
820 bdi->id = ++bdi_id_cursor;
822 p = bdi_lookup_rb_node(bdi->id, &parent);
823 rb_link_node(&bdi->rb_node, parent, p);
824 rb_insert_color(&bdi->rb_node, &bdi_tree);
826 list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
828 spin_unlock_bh(&bdi_lock);
830 trace_writeback_bdi_register(bdi);
834 int bdi_register(struct backing_dev_info *bdi, const char *fmt, ...)
840 ret = bdi_register_va(bdi, fmt, args);
844 EXPORT_SYMBOL(bdi_register);
846 void bdi_set_owner(struct backing_dev_info *bdi, struct device *owner)
848 WARN_ON_ONCE(bdi->owner);
854 * Remove bdi from bdi_list, and ensure that it is no longer visible
856 static void bdi_remove_from_list(struct backing_dev_info *bdi)
858 spin_lock_bh(&bdi_lock);
859 rb_erase(&bdi->rb_node, &bdi_tree);
860 list_del_rcu(&bdi->bdi_list);
861 spin_unlock_bh(&bdi_lock);
863 synchronize_rcu_expedited();
866 void bdi_unregister(struct backing_dev_info *bdi)
868 /* make sure nobody finds us on the bdi_list anymore */
869 bdi_remove_from_list(bdi);
870 wb_shutdown(&bdi->wb);
871 cgwb_bdi_unregister(bdi);
874 bdi_debug_unregister(bdi);
875 device_unregister(bdi->dev);
880 put_device(bdi->owner);
885 static void release_bdi(struct kref *ref)
887 struct backing_dev_info *bdi =
888 container_of(ref, struct backing_dev_info, refcnt);
890 if (test_bit(WB_registered, &bdi->wb.state))
892 WARN_ON_ONCE(bdi->dev);
897 void bdi_put(struct backing_dev_info *bdi)
899 kref_put(&bdi->refcnt, release_bdi);
901 EXPORT_SYMBOL(bdi_put);
903 const char *bdi_dev_name(struct backing_dev_info *bdi)
905 if (!bdi || !bdi->dev)
906 return bdi_unknown_name;
907 return bdi->dev_name;
909 EXPORT_SYMBOL_GPL(bdi_dev_name);
911 static wait_queue_head_t congestion_wqh[2] = {
912 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
913 __WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
915 static atomic_t nr_wb_congested[2];
917 void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
919 wait_queue_head_t *wqh = &congestion_wqh[sync];
920 enum wb_congested_state bit;
922 bit = sync ? WB_sync_congested : WB_async_congested;
923 if (test_and_clear_bit(bit, &bdi->wb.congested))
924 atomic_dec(&nr_wb_congested[sync]);
925 smp_mb__after_atomic();
926 if (waitqueue_active(wqh))
929 EXPORT_SYMBOL(clear_bdi_congested);
931 void set_bdi_congested(struct backing_dev_info *bdi, int sync)
933 enum wb_congested_state bit;
935 bit = sync ? WB_sync_congested : WB_async_congested;
936 if (!test_and_set_bit(bit, &bdi->wb.congested))
937 atomic_inc(&nr_wb_congested[sync]);
939 EXPORT_SYMBOL(set_bdi_congested);
942 * congestion_wait - wait for a backing_dev to become uncongested
943 * @sync: SYNC or ASYNC IO
944 * @timeout: timeout in jiffies
946 * Waits for up to @timeout jiffies for a backing_dev (any backing_dev) to exit
947 * write congestion. If no backing_devs are congested then just wait for the
948 * next write to be completed.
950 long congestion_wait(int sync, long timeout)
953 unsigned long start = jiffies;
955 wait_queue_head_t *wqh = &congestion_wqh[sync];
957 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
958 ret = io_schedule_timeout(timeout);
959 finish_wait(wqh, &wait);
961 trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
962 jiffies_to_usecs(jiffies - start));
966 EXPORT_SYMBOL(congestion_wait);
969 * wait_iff_congested - Conditionally wait for a backing_dev to become uncongested or a pgdat to complete writes
970 * @sync: SYNC or ASYNC IO
971 * @timeout: timeout in jiffies
973 * In the event of a congested backing_dev (any backing_dev) this waits
974 * for up to @timeout jiffies for either a BDI to exit congestion of the
975 * given @sync queue or a write to complete.
977 * The return value is 0 if the sleep is for the full timeout. Otherwise,
978 * it is the number of jiffies that were still remaining when the function
979 * returned. return_value == timeout implies the function did not sleep.
981 long wait_iff_congested(int sync, long timeout)
984 unsigned long start = jiffies;
986 wait_queue_head_t *wqh = &congestion_wqh[sync];
989 * If there is no congestion, yield if necessary instead
990 * of sleeping on the congestion queue
992 if (atomic_read(&nr_wb_congested[sync]) == 0) {
995 /* In case we scheduled, work out time remaining */
996 ret = timeout - (jiffies - start);
1003 /* Sleep until uncongested or a write happens */
1004 prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
1005 ret = io_schedule_timeout(timeout);
1006 finish_wait(wqh, &wait);
1009 trace_writeback_wait_iff_congested(jiffies_to_usecs(timeout),
1010 jiffies_to_usecs(jiffies - start));
1014 EXPORT_SYMBOL(wait_iff_congested);