#include <linux/wait.h>#include <linux/backing-dev.h>#include <linux/kthread.h>#include <linux/freezer.h>#include <linux/fs.h>#include <linux/pagemap.h>#include <linux/mm.h>#include <linux/sched.h>#include <linux/module.h>#include <linux/writeback.h>#include <linux/device.h>#include <trace/events/writeback.h> static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0); struct backing_dev_info default_backing_dev_info = {	.name		= "default",	.ra_pages	= VM_MAX_READAHEAD * 1024 / PAGE_CACHE_SIZE,	.state		= 0,	.capabilities	= BDI_CAP_MAP_COPY,};EXPORT_SYMBOL_GPL(default_backing_dev_info); struct backing_dev_info noop_backing_dev_info = {	.name		= "noop",	.capabilities	= BDI_CAP_NO_ACCT_AND_WRITEBACK,};EXPORT_SYMBOL_GPL(noop_backing_dev_info); static struct class *bdi_class; /* * bdi_lock protects updates to bdi_list. bdi_list has RCU reader side * locking. */DEFINE_SPINLOCK(bdi_lock);LIST_HEAD(bdi_list); /* bdi_wq serves all asynchronous writeback tasks */struct workqueue_struct *bdi_wq; void bdi_lock_two(struct bdi_writeback *wb1, struct bdi_writeback *wb2){	if (wb1 < wb2) {		spin_lock(&wb1->list_lock);		spin_lock_nested(&wb2->list_lock, 1);	} else {		spin_lock(&wb2->list_lock);		spin_lock_nested(&wb1->list_lock, 1);	}} #ifdef CONFIG_DEBUG_FS#include <linux/debugfs.h>#include <linux/seq_file.h> static struct dentry *bdi_debug_root; static void bdi_debug_init(void){	bdi_debug_root = debugfs_create_dir("bdi", NULL);} static int bdi_debug_stats_show(struct seq_file *m, void *v){	struct backing_dev_info *bdi = m->private;	struct bdi_writeback *wb = &bdi->wb;	unsigned long background_thresh;	unsigned long dirty_thresh;	unsigned long bdi_thresh;	unsigned long nr_dirty, nr_io, nr_more_io;	struct inode *inode; 	nr_dirty = nr_io = nr_more_io = 0;	spin_lock(&wb->list_lock);	list_for_each_entry(inode, &wb->b_dirty, i_wb_list)		nr_dirty++;	list_for_each_entry(inode, &wb->b_io, i_wb_list)		nr_io++;	list_for_each_entry(inode, &wb->b_more_io, i_wb_list)		nr_more_io++;	spin_unlock(&wb->list_lock); 	global_dirty_limits(&background_thresh, &dirty_thresh);	bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh); #define K(x) ((x) << (PAGE_SHIFT - 10))	seq_printf(m,		   "BdiWriteback:       %10lu kB\n"		   "BdiReclaimable:     %10lu kB\n"		   "BdiDirtyThresh:     %10lu kB\n"		   "DirtyThresh:        %10lu kB\n"		   "BackgroundThresh:   %10lu kB\n"		   "BdiDirtied:         %10lu kB\n"		   "BdiWritten:         %10lu kB\n"		   "BdiWriteBandwidth:  %10lu kBps\n"		   "b_dirty:            %10lu\n"		   "b_io:               %10lu\n"		   "b_more_io:          %10lu\n"		   "bdi_list:           %10u\n"		   "state:              %10lx\n",		   (unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)),		   (unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)),		   K(bdi_thresh),		   K(dirty_thresh),		   K(background_thresh),		   (unsigned long) K(bdi_stat(bdi, BDI_DIRTIED)),		   (unsigned long) K(bdi_stat(bdi, BDI_WRITTEN)),		   (unsigned long) K(bdi->write_bandwidth),		   nr_dirty,		   nr_io,		   nr_more_io,		   !list_empty(&bdi->bdi_list), bdi->state);#undef K 	return 0;} static int bdi_debug_stats_open(struct inode *inode, struct file *file){	return single_open(file, bdi_debug_stats_show, inode->i_private);} static const struct file_operations bdi_debug_stats_fops = {	.open		= bdi_debug_stats_open,	.read		= seq_read,	.llseek		= seq_lseek,	.release	= single_release,}; static void bdi_debug_register(struct backing_dev_info *bdi, const char *name){	bdi->debug_dir = debugfs_create_dir(name, bdi_debug_root);	bdi->debug_stats = debugfs_create_file("stats", 0444, bdi->debug_dir,					       bdi, &bdi_debug_stats_fops);} static void bdi_debug_unregister(struct backing_dev_info *bdi){	debugfs_remove(bdi->debug_stats);	debugfs_remove(bdi->debug_dir);}#elsestatic inline void bdi_debug_init(void){}static inline void bdi_debug_register(struct backing_dev_info *bdi,				      const char *name){}static inline void bdi_debug_unregister(struct backing_dev_info *bdi){}#endif static ssize_t read_ahead_kb_store(struct device *dev,				  struct device_attribute *attr,				  const char *buf, size_t count){	struct backing_dev_info *bdi = dev_get_drvdata(dev);	unsigned long read_ahead_kb;	ssize_t ret; 	ret = kstrtoul(buf, 10, &read_ahead_kb);	if (ret < 0)		return ret; 	bdi->ra_pages = read_ahead_kb >> (PAGE_SHIFT - 10); 	return count;} #define K(pages) ((pages) << (PAGE_SHIFT - 10)) #define BDI_SHOW(name, expr)						\static ssize_t name##_show(struct device *dev,				\			   struct device_attribute *attr, char *page)	\{									\	struct backing_dev_info *bdi = dev_get_drvdata(dev);		\									\	return snprintf(page, PAGE_SIZE-1, "%lld\n", (long long)expr);	\}									\static DEVICE_ATTR_RW(name); BDI_SHOW(read_ahead_kb, K(bdi->ra_pages)) static ssize_t min_ratio_store(struct device *dev,		struct device_attribute *attr, const char *buf, size_t count){	struct backing_dev_info *bdi = dev_get_drvdata(dev);	unsigned int ratio;	ssize_t ret; 	ret = kstrtouint(buf, 10, &ratio);	if (ret < 0)		return ret; 	ret = bdi_set_min_ratio(bdi, ratio);	if (!ret)		ret = count; 	return ret;}BDI_SHOW(min_ratio, bdi->min_ratio) static ssize_t max_ratio_store(struct device *dev,		struct device_attribute *attr, const char *buf, size_t count){	struct backing_dev_info *bdi = dev_get_drvdata(dev);	unsigned int ratio;	ssize_t ret; 	ret = kstrtouint(buf, 10, &ratio);	if (ret < 0)		return ret; 	ret = bdi_set_max_ratio(bdi, ratio);	if (!ret)		ret = count; 	return ret;}BDI_SHOW(max_ratio, bdi->max_ratio) static ssize_t stable_pages_required_show(struct device *dev,					  struct device_attribute *attr,					  char *page){	struct backing_dev_info *bdi = dev_get_drvdata(dev); 	return snprintf(page, PAGE_SIZE-1, "%d\n",			bdi_cap_stable_pages_required(bdi) ? 1 : 0);}static DEVICE_ATTR_RO(stable_pages_required); static struct attribute *bdi_dev_attrs[] = {	&dev_attr_read_ahead_kb.attr,	&dev_attr_min_ratio.attr,	&dev_attr_max_ratio.attr,	&dev_attr_stable_pages_required.attr,	NULL,};ATTRIBUTE_GROUPS(bdi_dev); static __init int bdi_class_init(void){	bdi_class = class_create(THIS_MODULE, "bdi");	if (IS_ERR(bdi_class))		return PTR_ERR(bdi_class); 	bdi_class->dev_groups = bdi_dev_groups;	bdi_debug_init();	return 0;}postcore_initcall(bdi_class_init); static int __init default_bdi_init(void){	int err; 	bdi_wq = alloc_workqueue("writeback", WQ_MEM_RECLAIM | WQ_FREEZABLE |					      WQ_UNBOUND | WQ_SYSFS, 0);	if (!bdi_wq)		return -ENOMEM; 	err = bdi_init(&default_backing_dev_info);	if (!err)		bdi_register(&default_backing_dev_info, NULL, "default");	err = bdi_init(&noop_backing_dev_info); 	return err;}subsys_initcall(default_bdi_init); int bdi_has_dirty_io(struct backing_dev_info *bdi){	return wb_has_dirty_io(&bdi->wb);} /* * This function is used when the first inode for this bdi is marked dirty. It * wakes-up the corresponding bdi thread which should then take care of the * periodic background write-out of dirty inodes. Since the write-out would * starts only 'dirty_writeback_interval' centisecs from now anyway, we just * set up a timer which wakes the bdi thread up later. * * Note, we wouldn't bother setting up the timer, but this function is on the * fast-path (used by '__mark_inode_dirty()'), so we save few context switches * by delaying the wake-up. */void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi){	unsigned long timeout; 	timeout = msecs_to_jiffies(dirty_writeback_interval * 10);	mod_delayed_work(bdi_wq, &bdi->wb.dwork, timeout);} /* * Remove bdi from bdi_list, and ensure that it is no longer visible */static void bdi_remove_from_list(struct backing_dev_info *bdi){	spin_lock_bh(&bdi_lock);	list_del_rcu(&bdi->bdi_list);	spin_unlock_bh(&bdi_lock); 	synchronize_rcu_expedited(); 	/* bdi_list is now unused, clear it to mark @bdi dying */	INIT_LIST_HEAD(&bdi->bdi_list);} int bdi_register(struct backing_dev_info *bdi, struct device *parent,		const char *fmt, ...){	va_list args;	struct device *dev; 	if (bdi->dev)	/* The driver needs to use separate queues per device */		return 0; 	va_start(args, fmt);	dev = device_create_vargs(bdi_class, parent, MKDEV(0, 0), bdi, fmt, args);	va_end(args);	if (IS_ERR(dev))		return PTR_ERR(dev); 	bdi->dev = dev; 	bdi_debug_register(bdi, dev_name(dev));	set_bit(BDI_registered, &bdi->state); 	spin_lock_bh(&bdi_lock);	list_add_tail_rcu(&bdi->bdi_list, &bdi_list);	spin_unlock_bh(&bdi_lock); 	trace_writeback_bdi_register(bdi);	return 0;}EXPORT_SYMBOL(bdi_register); int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev){	return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));}EXPORT_SYMBOL(bdi_register_dev); /* * Remove bdi from the global list and shutdown any threads we have running */static void bdi_wb_shutdown(struct backing_dev_info *bdi){	if (!bdi_cap_writeback_dirty(bdi))		return; 	/*	 * Make sure nobody finds us on the bdi_list anymore	 */	bdi_remove_from_list(bdi); 	/*	 * Drain work list and shutdown the delayed_work.  At this point,	 * @bdi->bdi_list is empty telling bdi_Writeback_workfn() that @bdi	 * is dying and its work_list needs to be drained no matter what.	 */	mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);	flush_delayed_work(&bdi->wb.dwork);	WARN_ON(!list_empty(&bdi->work_list)); 	/*	 * This shouldn't be necessary unless @bdi for some reason has	 * unflushed dirty IO after work_list is drained.  Do it anyway	 * just in case.	 */	cancel_delayed_work_sync(&bdi->wb.dwork);} /* * This bdi is going away now, make sure that no super_blocks point to it */static void bdi_prune_sb(struct backing_dev_info *bdi){	struct super_block *sb; 	spin_lock(&sb_lock);	list_for_each_entry(sb, &super_blocks, s_list) {		if (sb->s_bdi == bdi)			sb->s_bdi = &default_backing_dev_info;	}	spin_unlock(&sb_lock);} void bdi_unregister(struct backing_dev_info *bdi){	struct device *dev = bdi->dev; 	if (dev) {		bdi_set_min_ratio(bdi, 0);		trace_writeback_bdi_unregister(bdi);		bdi_prune_sb(bdi); 		bdi_wb_shutdown(bdi);		bdi_debug_unregister(bdi); 		spin_lock_bh(&bdi->wb_lock);		bdi->dev = NULL;		spin_unlock_bh(&bdi->wb_lock); 		device_unregister(dev);	}}EXPORT_SYMBOL(bdi_unregister); static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi){	memset(wb, 0, sizeof(*wb)); 	wb->bdi = bdi;	wb->last_old_flush = jiffies;	INIT_LIST_HEAD(&wb->b_dirty);	INIT_LIST_HEAD(&wb->b_io);	INIT_LIST_HEAD(&wb->b_more_io);	spin_lock_init(&wb->list_lock);	INIT_DELAYED_WORK(&wb->dwork, bdi_writeback_workfn);} /* * Initial write bandwidth: 100 MB/s */#define INIT_BW		(100 << (20 - PAGE_SHIFT)) int bdi_init(struct backing_dev_info *bdi){	int i, err; 	bdi->dev = NULL; 	bdi->min_ratio = 0;	bdi->max_ratio = 100;	bdi->max_prop_frac = FPROP_FRAC_BASE;	spin_lock_init(&bdi->wb_lock);	INIT_LIST_HEAD(&bdi->bdi_list);	INIT_LIST_HEAD(&bdi->work_list); 	bdi_wb_init(&bdi->wb, bdi); 	for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {		err = percpu_counter_init(&bdi->bdi_stat[i], 0);		if (err)			goto err;	} 	bdi->dirty_exceeded = 0; 	bdi->bw_time_stamp = jiffies;	bdi->written_stamp = 0; 	bdi->balanced_dirty_ratelimit = INIT_BW;	bdi->dirty_ratelimit = INIT_BW;	bdi->write_bandwidth = INIT_BW;	bdi->avg_write_bandwidth = INIT_BW; 	err = fprop_local_init_percpu(&bdi->completions); 	if (err) {err:		while (i--)			percpu_counter_destroy(&bdi->bdi_stat[i]);	} 	return err;}EXPORT_SYMBOL(bdi_init); void bdi_destroy(struct backing_dev_info *bdi){	int i; 	/*	 * Splice our entries to the default_backing_dev_info, if this	 * bdi disappears	 */	if (bdi_has_dirty_io(bdi)) {		struct bdi_writeback *dst = &default_backing_dev_info.wb; 		bdi_lock_two(&bdi->wb, dst);		list_splice(&bdi->wb.b_dirty, &dst->b_dirty);		list_splice(&bdi->wb.b_io, &dst->b_io);		list_splice(&bdi->wb.b_more_io, &dst->b_more_io);		spin_unlock(&bdi->wb.list_lock);		spin_unlock(&dst->list_lock);	} 	bdi_unregister(bdi); 	/*	 * If bdi_unregister() had already been called earlier, the dwork	 * could still be pending because bdi_prune_sb() can race with the

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