include/linux/backing-dev.h - linux-imx - Git at Google

 /*
  * include/linux/backing-dev.h
  *
  * low-level device information and state which is propagated up through
  * to high-level code.
  */

 #ifndef _LINUX_BACKING_DEV_H
 #define _LINUX_BACKING_DEV_H

 #include <linux/kernel.h>
 #include <linux/fs.h>
 #include <linux/sched.h>
 #include <linux/blkdev.h>
 #include <linux/writeback.h>
 #include <linux/blk-cgroup.h>
 #include <linux/backing-dev-defs.h>
 #include <linux/slab.h>

 int __must_check bdi_init(struct backing_dev_info *bdi);
 void bdi_exit(struct backing_dev_info *bdi);

 __printf(3, 4)
 int bdi_register(struct backing_dev_info *bdi, struct device *parent,
 		const char *fmt, ...);
 int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev);
 int bdi_register_owner(struct backing_dev_info *bdi, struct device *owner);
 void bdi_unregister(struct backing_dev_info *bdi);

 int __must_check bdi_setup_and_register(struct backing_dev_info *, char *);
 void bdi_destroy(struct backing_dev_info *bdi);

 void wb_start_writeback(struct bdi_writeback *wb, long nr_pages,
 			bool range_cyclic, enum wb_reason reason);
 void wb_start_background_writeback(struct bdi_writeback *wb);
 void wb_workfn(struct work_struct *work);
 void wb_wakeup_delayed(struct bdi_writeback *wb);

 extern spinlock_t bdi_lock;
 extern struct list_head bdi_list;

 extern struct workqueue_struct *bdi_wq;

 static inline bool wb_has_dirty_io(struct bdi_writeback *wb)
 {
 	return test_bit(WB_has_dirty_io, &wb->state);
 }

 static inline bool bdi_has_dirty_io(struct backing_dev_info *bdi)
 {
 	/*
 	 * @bdi->tot_write_bandwidth is guaranteed to be > 0 if there are
 	 * any dirty wbs.  See wb_update_write_bandwidth().
 	 */
 	return atomic_long_read(&bdi->tot_write_bandwidth);
 }

 static inline void __add_wb_stat(struct bdi_writeback *wb,
 				 enum wb_stat_item item, s64 amount)
 {
 	__percpu_counter_add(&wb->stat[item], amount, WB_STAT_BATCH);
 }

 static inline void __inc_wb_stat(struct bdi_writeback *wb,
 				 enum wb_stat_item item)
 {
 	__add_wb_stat(wb, item, 1);
 }

 static inline void inc_wb_stat(struct bdi_writeback *wb, enum wb_stat_item item)
 {
 	unsigned long flags;

 	local_irq_save(flags);
 	__inc_wb_stat(wb, item);
 	local_irq_restore(flags);
 }

 static inline void __dec_wb_stat(struct bdi_writeback *wb,
 				 enum wb_stat_item item)
 {
 	__add_wb_stat(wb, item, -1);
 }

 static inline void dec_wb_stat(struct bdi_writeback *wb, enum wb_stat_item item)
 {
 	unsigned long flags;

 	local_irq_save(flags);
 	__dec_wb_stat(wb, item);
 	local_irq_restore(flags);
 }

 static inline s64 wb_stat(struct bdi_writeback *wb, enum wb_stat_item item)
 {
 	return percpu_counter_read_positive(&wb->stat[item]);
 }

 static inline s64 __wb_stat_sum(struct bdi_writeback *wb,
 				enum wb_stat_item item)
 {
 	return percpu_counter_sum_positive(&wb->stat[item]);
 }

 static inline s64 wb_stat_sum(struct bdi_writeback *wb, enum wb_stat_item item)
 {
 	s64 sum;
 	unsigned long flags;

 	local_irq_save(flags);
 	sum = __wb_stat_sum(wb, item);
 	local_irq_restore(flags);

 	return sum;
 }

 extern void wb_writeout_inc(struct bdi_writeback *wb);

 /*
  * maximal error of a stat counter.
  */
 static inline unsigned long wb_stat_error(struct bdi_writeback *wb)
 {
 #ifdef CONFIG_SMP
 	return nr_cpu_ids * WB_STAT_BATCH;
 #else
 	return 1;
 #endif
 }

 int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio);
 int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio);

 /*
  * Flags in backing_dev_info::capability
  *
  * The first three flags control whether dirty pages will contribute to the
  * VM's accounting and whether writepages() should be called for dirty pages
  * (something that would not, for example, be appropriate for ramfs)
  *
  * WARNING: these flags are closely related and should not normally be
  * used separately.  The BDI_CAP_NO_ACCT_AND_WRITEBACK combines these
  * three flags into a single convenience macro.
  *
  * BDI_CAP_NO_ACCT_DIRTY:  Dirty pages shouldn't contribute to accounting
  * BDI_CAP_NO_WRITEBACK:   Don't write pages back
  * BDI_CAP_NO_ACCT_WB:     Don't automatically account writeback pages
  * BDI_CAP_STRICTLIMIT:    Keep number of dirty pages below bdi threshold.
  *
  * BDI_CAP_CGROUP_WRITEBACK: Supports cgroup-aware writeback.
  */
 #define BDI_CAP_NO_ACCT_DIRTY	0x00000001
 #define BDI_CAP_NO_WRITEBACK	0x00000002
 #define BDI_CAP_NO_ACCT_WB	0x00000004
 #define BDI_CAP_STABLE_WRITES	0x00000008
 #define BDI_CAP_STRICTLIMIT	0x00000010
 #define BDI_CAP_CGROUP_WRITEBACK 0x00000020

 #define BDI_CAP_NO_ACCT_AND_WRITEBACK \
 	(BDI_CAP_NO_WRITEBACK | BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_ACCT_WB)

 extern struct backing_dev_info noop_backing_dev_info;

 /**
  * writeback_in_progress - determine whether there is writeback in progress
  * @wb: bdi_writeback of interest
  *
  * Determine whether there is writeback waiting to be handled against a
  * bdi_writeback.
  */
 static inline bool writeback_in_progress(struct bdi_writeback *wb)
 {
 	return test_bit(WB_writeback_running, &wb->state);
 }

 static inline struct backing_dev_info *inode_to_bdi(struct inode *inode)
 {
 	struct super_block *sb;

 	if (!inode)
 		return &noop_backing_dev_info;

 	sb = inode->i_sb;
 #ifdef CONFIG_BLOCK
 	if (sb_is_blkdev_sb(sb))
 		return blk_get_backing_dev_info(I_BDEV(inode));
 #endif
 	return sb->s_bdi;
 }

 static inline int wb_congested(struct bdi_writeback *wb, int cong_bits)
 {
 	struct backing_dev_info *bdi = wb->bdi;

 	if (bdi->congested_fn)
 		return bdi->congested_fn(bdi->congested_data, cong_bits);
 	return wb->congested->state & cong_bits;
 }

 long congestion_wait(int sync, long timeout);
 long wait_iff_congested(struct pglist_data *pgdat, int sync, long timeout);
 int pdflush_proc_obsolete(struct ctl_table *table, int write,
 		void __user *buffer, size_t *lenp, loff_t *ppos);

 static inline bool bdi_cap_stable_pages_required(struct backing_dev_info *bdi)
 {
 	return bdi->capabilities & BDI_CAP_STABLE_WRITES;
 }

 static inline bool bdi_cap_writeback_dirty(struct backing_dev_info *bdi)
 {
 	return !(bdi->capabilities & BDI_CAP_NO_WRITEBACK);
 }

 static inline bool bdi_cap_account_dirty(struct backing_dev_info *bdi)
 {
 	return !(bdi->capabilities & BDI_CAP_NO_ACCT_DIRTY);
 }

 static inline bool bdi_cap_account_writeback(struct backing_dev_info *bdi)
 {
 	/* Paranoia: BDI_CAP_NO_WRITEBACK implies BDI_CAP_NO_ACCT_WB */
 	return !(bdi->capabilities & (BDI_CAP_NO_ACCT_WB |
 				      BDI_CAP_NO_WRITEBACK));
 }

 static inline bool mapping_cap_writeback_dirty(struct address_space *mapping)
 {
 	return bdi_cap_writeback_dirty(inode_to_bdi(mapping->host));
 }

 static inline bool mapping_cap_account_dirty(struct address_space *mapping)
 {
 	return bdi_cap_account_dirty(inode_to_bdi(mapping->host));
 }

 static inline int bdi_sched_wait(void *word)
 {
 	schedule();
 	return 0;
 }

 #ifdef CONFIG_CGROUP_WRITEBACK

 struct bdi_writeback_congested *
 wb_congested_get_create(struct backing_dev_info *bdi, int blkcg_id, gfp_t gfp);
 void wb_congested_put(struct bdi_writeback_congested *congested);
 struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
 				    struct cgroup_subsys_state *memcg_css,
 				    gfp_t gfp);
 void wb_memcg_offline(struct mem_cgroup *memcg);
 void wb_blkcg_offline(struct blkcg *blkcg);
 int inode_congested(struct inode *inode, int cong_bits);

 /**
  * inode_cgwb_enabled - test whether cgroup writeback is enabled on an inode
  * @inode: inode of interest
  *
  * cgroup writeback requires support from both the bdi and filesystem.
  * Also, both memcg and iocg have to be on the default hierarchy.  Test
  * whether all conditions are met.
  *
  * Note that the test result may change dynamically on the same inode
  * depending on how memcg and iocg are configured.
  */
 static inline bool inode_cgwb_enabled(struct inode *inode)
 {
 	struct backing_dev_info *bdi = inode_to_bdi(inode);

 	return cgroup_subsys_on_dfl(memory_cgrp_subsys) &&
 		cgroup_subsys_on_dfl(io_cgrp_subsys) &&
 		bdi_cap_account_dirty(bdi) &&
 		(bdi->capabilities & BDI_CAP_CGROUP_WRITEBACK) &&
 		(inode->i_sb->s_iflags & SB_I_CGROUPWB);
 }

 /**
  * wb_find_current - find wb for %current on a bdi
  * @bdi: bdi of interest
  *
  * Find the wb of @bdi which matches both the memcg and blkcg of %current.
  * Must be called under rcu_read_lock() which protects the returend wb.
  * NULL if not found.
  */
 static inline struct bdi_writeback *wb_find_current(struct backing_dev_info *bdi)
 {
 	struct cgroup_subsys_state *memcg_css;
 	struct bdi_writeback *wb;

 	memcg_css = task_css(current, memory_cgrp_id);
 	if (!memcg_css->parent)
 		return &bdi->wb;

 	wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);

 	/*
 	 * %current's blkcg equals the effective blkcg of its memcg.  No
 	 * need to use the relatively expensive cgroup_get_e_css().
 	 */
 	if (likely(wb && wb->blkcg_css == task_css(current, io_cgrp_id)))
 		return wb;
 	return NULL;
 }

 /**
  * wb_get_create_current - get or create wb for %current on a bdi
  * @bdi: bdi of interest
  * @gfp: allocation mask
  *
  * Equivalent to wb_get_create() on %current's memcg.  This function is
  * called from a relatively hot path and optimizes the common cases using
  * wb_find_current().
  */
 static inline struct bdi_writeback *
 wb_get_create_current(struct backing_dev_info *bdi, gfp_t gfp)
 {
 	struct bdi_writeback *wb;

 	rcu_read_lock();
 	wb = wb_find_current(bdi);
 	if (wb && unlikely(!wb_tryget(wb)))
 		wb = NULL;
 	rcu_read_unlock();

 	if (unlikely(!wb)) {
 		struct cgroup_subsys_state *memcg_css;

 		memcg_css = task_get_css(current, memory_cgrp_id);
 		wb = wb_get_create(bdi, memcg_css, gfp);
 		css_put(memcg_css);
 	}
 	return wb;
 }

 /**
  * inode_to_wb_is_valid - test whether an inode has a wb associated
  * @inode: inode of interest
  *
  * Returns %true if @inode has a wb associated.  May be called without any
  * locking.
  */
 static inline bool inode_to_wb_is_valid(struct inode *inode)
 {
 	return inode->i_wb;
 }

 /**
  * inode_to_wb - determine the wb of an inode
  * @inode: inode of interest
  *
  * Returns the wb @inode is currently associated with.  The caller must be
  * holding either @inode->i_lock, @inode->i_mapping->tree_lock, or the
  * associated wb's list_lock.
  */
 static inline struct bdi_writeback *inode_to_wb(struct inode *inode)
 {
 #ifdef CONFIG_LOCKDEP
 	WARN_ON_ONCE(debug_locks &&
 		     (!lockdep_is_held(&inode->i_lock) &&
 		      !lockdep_is_held(&inode->i_mapping->tree_lock) &&
 		      !lockdep_is_held(&inode->i_wb->list_lock)));
 #endif
 	return inode->i_wb;
 }

 /**
  * unlocked_inode_to_wb_begin - begin unlocked inode wb access transaction
  * @inode: target inode
  * @lockedp: temp bool output param, to be passed to the end function
  *
  * The caller wants to access the wb associated with @inode but isn't
  * holding inode->i_lock, mapping->tree_lock or wb->list_lock.  This
  * function determines the wb associated with @inode and ensures that the
  * association doesn't change until the transaction is finished with
  * unlocked_inode_to_wb_end().
  *
  * The caller must call unlocked_inode_to_wb_end() with *@lockdep
  * afterwards and can't sleep during transaction.  IRQ may or may not be
  * disabled on return.
  */
 static inline struct bdi_writeback *
 unlocked_inode_to_wb_begin(struct inode *inode, bool *lockedp)
 {
 	rcu_read_lock();

 	/*
 	 * Paired with store_release in inode_switch_wb_work_fn() and
 	 * ensures that we see the new wb if we see cleared I_WB_SWITCH.
 	 */
 	*lockedp = smp_load_acquire(&inode->i_state) & I_WB_SWITCH;

 	if (unlikely(*lockedp))
 		spin_lock_irq(&inode->i_mapping->tree_lock);

 	/*
 	 * Protected by either !I_WB_SWITCH + rcu_read_lock() or tree_lock.
 	 * inode_to_wb() will bark.  Deref directly.
 	 */
 	return inode->i_wb;
 }

 /**
  * unlocked_inode_to_wb_end - end inode wb access transaction
  * @inode: target inode
  * @locked: *@lockedp from unlocked_inode_to_wb_begin()
  */
 static inline void unlocked_inode_to_wb_end(struct inode *inode, bool locked)
 {
 	if (unlikely(locked))
 		spin_unlock_irq(&inode->i_mapping->tree_lock);

 	rcu_read_unlock();
 }

 #else	/* CONFIG_CGROUP_WRITEBACK */

 static inline bool inode_cgwb_enabled(struct inode *inode)
 {
 	return false;
 }

 static inline struct bdi_writeback_congested *
 wb_congested_get_create(struct backing_dev_info *bdi, int blkcg_id, gfp_t gfp)
 {
 	atomic_inc(&bdi->wb_congested->refcnt);
 	return bdi->wb_congested;
 }

 static inline void wb_congested_put(struct bdi_writeback_congested *congested)
 {
 	if (atomic_dec_and_test(&congested->refcnt))
 		kfree(congested);
 }

 static inline struct bdi_writeback *wb_find_current(struct backing_dev_info *bdi)
 {
 	return &bdi->wb;
 }

 static inline struct bdi_writeback *
 wb_get_create_current(struct backing_dev_info *bdi, gfp_t gfp)
 {
 	return &bdi->wb;
 }

 static inline bool inode_to_wb_is_valid(struct inode *inode)
 {
 	return true;
 }

 static inline struct bdi_writeback *inode_to_wb(struct inode *inode)
 {
 	return &inode_to_bdi(inode)->wb;
 }

 static inline struct bdi_writeback *
 unlocked_inode_to_wb_begin(struct inode *inode, bool *lockedp)
 {
 	return inode_to_wb(inode);
 }

 static inline void unlocked_inode_to_wb_end(struct inode *inode, bool locked)
 {
 }

 static inline void wb_memcg_offline(struct mem_cgroup *memcg)
 {
 }

 static inline void wb_blkcg_offline(struct blkcg *blkcg)
 {
 }

 static inline int inode_congested(struct inode *inode, int cong_bits)
 {
 	return wb_congested(&inode_to_bdi(inode)->wb, cong_bits);
 }

 #endif	/* CONFIG_CGROUP_WRITEBACK */

 static inline int inode_read_congested(struct inode *inode)
 {
 	return inode_congested(inode, 1 << WB_sync_congested);
 }

 static inline int inode_write_congested(struct inode *inode)
 {
 	return inode_congested(inode, 1 << WB_async_congested);
 }

 static inline int inode_rw_congested(struct inode *inode)
 {
 	return inode_congested(inode, (1 << WB_sync_congested) |
 				      (1 << WB_async_congested));
 }

 static inline int bdi_congested(struct backing_dev_info *bdi, int cong_bits)
 {
 	return wb_congested(&bdi->wb, cong_bits);
 }

 static inline int bdi_read_congested(struct backing_dev_info *bdi)
 {
 	return bdi_congested(bdi, 1 << WB_sync_congested);
 }

 static inline int bdi_write_congested(struct backing_dev_info *bdi)
 {
 	return bdi_congested(bdi, 1 << WB_async_congested);
 }

 static inline int bdi_rw_congested(struct backing_dev_info *bdi)
 {
 	return bdi_congested(bdi, (1 << WB_sync_congested) |
 				  (1 << WB_async_congested));
 }

 #endif	/* _LINUX_BACKING_DEV_H */
	/*
	* include/linux/backing-dev.h
	*
	* low-level device information and state which is propagated up through
	* to high-level code.
	*/

	#ifndef _LINUX_BACKING_DEV_H
	#define _LINUX_BACKING_DEV_H

	#include <linux/kernel.h>
	#include <linux/fs.h>
	#include <linux/sched.h>
	#include <linux/blkdev.h>
	#include <linux/writeback.h>
	#include <linux/blk-cgroup.h>
	#include <linux/backing-dev-defs.h>
	#include <linux/slab.h>

	int __must_check bdi_init(struct backing_dev_info *bdi);
	void bdi_exit(struct backing_dev_info *bdi);

	__printf(3, 4)
	int bdi_register(struct backing_dev_info bdi, struct device parent,
	const char *fmt, ...);
	int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev);
	int bdi_register_owner(struct backing_dev_info bdi, struct device owner);
	void bdi_unregister(struct backing_dev_info *bdi);

	int __must_check bdi_setup_and_register(struct backing_dev_info , char );
	void bdi_destroy(struct backing_dev_info *bdi);

	void wb_start_writeback(struct bdi_writeback *wb, long nr_pages,
	bool range_cyclic, enum wb_reason reason);
	void wb_start_background_writeback(struct bdi_writeback *wb);
	void wb_workfn(struct work_struct *work);
	void wb_wakeup_delayed(struct bdi_writeback *wb);

	extern spinlock_t bdi_lock;
	extern struct list_head bdi_list;

	extern struct workqueue_struct *bdi_wq;

	static inline bool wb_has_dirty_io(struct bdi_writeback *wb)
	{
	return test_bit(WB_has_dirty_io, &wb->state);
	}

	static inline bool bdi_has_dirty_io(struct backing_dev_info *bdi)
	{
	/*
	* @bdi->tot_write_bandwidth is guaranteed to be > 0 if there are
	* any dirty wbs. See wb_update_write_bandwidth().
	*/
	return atomic_long_read(&bdi->tot_write_bandwidth);
	}

	static inline void __add_wb_stat(struct bdi_writeback *wb,
	enum wb_stat_item item, s64 amount)
	{
	__percpu_counter_add(&wb->stat[item], amount, WB_STAT_BATCH);
	}

	static inline void __inc_wb_stat(struct bdi_writeback *wb,
	enum wb_stat_item item)
	{
	__add_wb_stat(wb, item, 1);
	}

	static inline void inc_wb_stat(struct bdi_writeback *wb, enum wb_stat_item item)
	{
	unsigned long flags;

	local_irq_save(flags);
	__inc_wb_stat(wb, item);
	local_irq_restore(flags);
	}

	static inline void __dec_wb_stat(struct bdi_writeback *wb,
	enum wb_stat_item item)
	{
	__add_wb_stat(wb, item, -1);
	}

	static inline void dec_wb_stat(struct bdi_writeback *wb, enum wb_stat_item item)
	{
	unsigned long flags;

	local_irq_save(flags);
	__dec_wb_stat(wb, item);
	local_irq_restore(flags);
	}

	static inline s64 wb_stat(struct bdi_writeback *wb, enum wb_stat_item item)
	{
	return percpu_counter_read_positive(&wb->stat[item]);
	}

	static inline s64 __wb_stat_sum(struct bdi_writeback *wb,
	enum wb_stat_item item)
	{
	return percpu_counter_sum_positive(&wb->stat[item]);
	}

	static inline s64 wb_stat_sum(struct bdi_writeback *wb, enum wb_stat_item item)
	{
	s64 sum;
	unsigned long flags;

	local_irq_save(flags);
	sum = __wb_stat_sum(wb, item);
	local_irq_restore(flags);

	return sum;
	}

	extern void wb_writeout_inc(struct bdi_writeback *wb);

	/*
	* maximal error of a stat counter.
	*/
	static inline unsigned long wb_stat_error(struct bdi_writeback *wb)
	{
	#ifdef CONFIG_SMP
	return nr_cpu_ids * WB_STAT_BATCH;
	#else
	return 1;
	#endif
	}

	int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio);
	int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio);

	/*
	* Flags in backing_dev_info::capability
	*
	* The first three flags control whether dirty pages will contribute to the
	* VM's accounting and whether writepages() should be called for dirty pages
	* (something that would not, for example, be appropriate for ramfs)
	*
	* WARNING: these flags are closely related and should not normally be
	* used separately. The BDI_CAP_NO_ACCT_AND_WRITEBACK combines these
	* three flags into a single convenience macro.
	*
	* BDI_CAP_NO_ACCT_DIRTY: Dirty pages shouldn't contribute to accounting
	* BDI_CAP_NO_WRITEBACK: Don't write pages back
	* BDI_CAP_NO_ACCT_WB: Don't automatically account writeback pages
	* BDI_CAP_STRICTLIMIT: Keep number of dirty pages below bdi threshold.
	*
	* BDI_CAP_CGROUP_WRITEBACK: Supports cgroup-aware writeback.
	*/
	#define BDI_CAP_NO_ACCT_DIRTY 0x00000001
	#define BDI_CAP_NO_WRITEBACK 0x00000002
	#define BDI_CAP_NO_ACCT_WB 0x00000004
	#define BDI_CAP_STABLE_WRITES 0x00000008
	#define BDI_CAP_STRICTLIMIT 0x00000010
	#define BDI_CAP_CGROUP_WRITEBACK 0x00000020

	#define BDI_CAP_NO_ACCT_AND_WRITEBACK \
	(BDI_CAP_NO_WRITEBACK \| BDI_CAP_NO_ACCT_DIRTY \| BDI_CAP_NO_ACCT_WB)

	extern struct backing_dev_info noop_backing_dev_info;

	/**
	* writeback_in_progress - determine whether there is writeback in progress
	* @wb: bdi_writeback of interest
	*
	* Determine whether there is writeback waiting to be handled against a
	* bdi_writeback.
	*/
	static inline bool writeback_in_progress(struct bdi_writeback *wb)
	{
	return test_bit(WB_writeback_running, &wb->state);
	}

	static inline struct backing_dev_info inode_to_bdi(struct inode inode)
	{
	struct super_block *sb;

	if (!inode)
	return &noop_backing_dev_info;

	sb = inode->i_sb;
	#ifdef CONFIG_BLOCK
	if (sb_is_blkdev_sb(sb))
	return blk_get_backing_dev_info(I_BDEV(inode));
	#endif
	return sb->s_bdi;
	}

	static inline int wb_congested(struct bdi_writeback *wb, int cong_bits)
	{
	struct backing_dev_info *bdi = wb->bdi;

	if (bdi->congested_fn)
	return bdi->congested_fn(bdi->congested_data, cong_bits);
	return wb->congested->state & cong_bits;
	}

	long congestion_wait(int sync, long timeout);
	long wait_iff_congested(struct pglist_data *pgdat, int sync, long timeout);
	int pdflush_proc_obsolete(struct ctl_table *table, int write,
	void __user buffer, size_t lenp, loff_t *ppos);

	static inline bool bdi_cap_stable_pages_required(struct backing_dev_info *bdi)
	{
	return bdi->capabilities & BDI_CAP_STABLE_WRITES;
	}

	static inline bool bdi_cap_writeback_dirty(struct backing_dev_info *bdi)
	{
	return !(bdi->capabilities & BDI_CAP_NO_WRITEBACK);
	}

	static inline bool bdi_cap_account_dirty(struct backing_dev_info *bdi)
	{
	return !(bdi->capabilities & BDI_CAP_NO_ACCT_DIRTY);
	}

	static inline bool bdi_cap_account_writeback(struct backing_dev_info *bdi)
	{
	/* Paranoia: BDI_CAP_NO_WRITEBACK implies BDI_CAP_NO_ACCT_WB */
	return !(bdi->capabilities & (BDI_CAP_NO_ACCT_WB \|
	BDI_CAP_NO_WRITEBACK));
	}

	static inline bool mapping_cap_writeback_dirty(struct address_space *mapping)
	{
	return bdi_cap_writeback_dirty(inode_to_bdi(mapping->host));
	}

	static inline bool mapping_cap_account_dirty(struct address_space *mapping)
	{
	return bdi_cap_account_dirty(inode_to_bdi(mapping->host));
	}

	static inline int bdi_sched_wait(void *word)
	{
	schedule();
	return 0;
	}

	#ifdef CONFIG_CGROUP_WRITEBACK

	struct bdi_writeback_congested *
	wb_congested_get_create(struct backing_dev_info *bdi, int blkcg_id, gfp_t gfp);
	void wb_congested_put(struct bdi_writeback_congested *congested);
	struct bdi_writeback wb_get_create(struct backing_dev_info bdi,
	struct cgroup_subsys_state *memcg_css,
	gfp_t gfp);
	void wb_memcg_offline(struct mem_cgroup *memcg);
	void wb_blkcg_offline(struct blkcg *blkcg);
	int inode_congested(struct inode *inode, int cong_bits);

	/**
	* inode_cgwb_enabled - test whether cgroup writeback is enabled on an inode
	* @inode: inode of interest
	*
	* cgroup writeback requires support from both the bdi and filesystem.
	* Also, both memcg and iocg have to be on the default hierarchy. Test
	* whether all conditions are met.
	*
	* Note that the test result may change dynamically on the same inode
	* depending on how memcg and iocg are configured.
	*/
	static inline bool inode_cgwb_enabled(struct inode *inode)
	{
	struct backing_dev_info *bdi = inode_to_bdi(inode);

	return cgroup_subsys_on_dfl(memory_cgrp_subsys) &&
	cgroup_subsys_on_dfl(io_cgrp_subsys) &&
	bdi_cap_account_dirty(bdi) &&
	(bdi->capabilities & BDI_CAP_CGROUP_WRITEBACK) &&
	(inode->i_sb->s_iflags & SB_I_CGROUPWB);
	}

	/**
	* wb_find_current - find wb for %current on a bdi
	* @bdi: bdi of interest
	*
	* Find the wb of @bdi which matches both the memcg and blkcg of %current.
	* Must be called under rcu_read_lock() which protects the returend wb.
	* NULL if not found.
	*/
	static inline struct bdi_writeback wb_find_current(struct backing_dev_info bdi)
	{
	struct cgroup_subsys_state *memcg_css;
	struct bdi_writeback *wb;

	memcg_css = task_css(current, memory_cgrp_id);
	if (!memcg_css->parent)
	return &bdi->wb;

	wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);

	/*
	* %current's blkcg equals the effective blkcg of its memcg. No
	* need to use the relatively expensive cgroup_get_e_css().
	*/
	if (likely(wb && wb->blkcg_css == task_css(current, io_cgrp_id)))
	return wb;
	return NULL;
	}

	/**
	* wb_get_create_current - get or create wb for %current on a bdi
	* @bdi: bdi of interest
	* @gfp: allocation mask
	*
	* Equivalent to wb_get_create() on %current's memcg. This function is
	* called from a relatively hot path and optimizes the common cases using
	* wb_find_current().
	*/
	static inline struct bdi_writeback *
	wb_get_create_current(struct backing_dev_info *bdi, gfp_t gfp)
	{
	struct bdi_writeback *wb;

	rcu_read_lock();
	wb = wb_find_current(bdi);
	if (wb && unlikely(!wb_tryget(wb)))
	wb = NULL;
	rcu_read_unlock();

	if (unlikely(!wb)) {
	struct cgroup_subsys_state *memcg_css;

	memcg_css = task_get_css(current, memory_cgrp_id);
	wb = wb_get_create(bdi, memcg_css, gfp);
	css_put(memcg_css);
	}
	return wb;
	}

	/**
	* inode_to_wb_is_valid - test whether an inode has a wb associated
	* @inode: inode of interest
	*
	* Returns %true if @inode has a wb associated. May be called without any
	* locking.
	*/
	static inline bool inode_to_wb_is_valid(struct inode *inode)
	{
	return inode->i_wb;
	}

	/**
	* inode_to_wb - determine the wb of an inode
	* @inode: inode of interest
	*
	* Returns the wb @inode is currently associated with. The caller must be
	* holding either @inode->i_lock, @inode->i_mapping->tree_lock, or the
	* associated wb's list_lock.
	*/
	static inline struct bdi_writeback inode_to_wb(struct inode inode)
	{
	#ifdef CONFIG_LOCKDEP
	WARN_ON_ONCE(debug_locks &&
	(!lockdep_is_held(&inode->i_lock) &&
	!lockdep_is_held(&inode->i_mapping->tree_lock) &&
	!lockdep_is_held(&inode->i_wb->list_lock)));
	#endif
	return inode->i_wb;
	}

	/**
	* unlocked_inode_to_wb_begin - begin unlocked inode wb access transaction
	* @inode: target inode
	* @lockedp: temp bool output param, to be passed to the end function
	*
	* The caller wants to access the wb associated with @inode but isn't
	* holding inode->i_lock, mapping->tree_lock or wb->list_lock. This
	* function determines the wb associated with @inode and ensures that the
	* association doesn't change until the transaction is finished with
	* unlocked_inode_to_wb_end().
	*
	* The caller must call unlocked_inode_to_wb_end() with *@lockdep
	* afterwards and can't sleep during transaction. IRQ may or may not be
	* disabled on return.
	*/
	static inline struct bdi_writeback *
	unlocked_inode_to_wb_begin(struct inode inode, bool lockedp)
	{
	rcu_read_lock();

	/*
	* Paired with store_release in inode_switch_wb_work_fn() and
	* ensures that we see the new wb if we see cleared I_WB_SWITCH.
	*/
	*lockedp = smp_load_acquire(&inode->i_state) & I_WB_SWITCH;

	if (unlikely(*lockedp))
	spin_lock_irq(&inode->i_mapping->tree_lock);

	/*
	* Protected by either !I_WB_SWITCH + rcu_read_lock() or tree_lock.
	* inode_to_wb() will bark. Deref directly.
	*/
	return inode->i_wb;
	}

	/**
	* unlocked_inode_to_wb_end - end inode wb access transaction
	* @inode: target inode
	* @locked: *@lockedp from unlocked_inode_to_wb_begin()
	*/
	static inline void unlocked_inode_to_wb_end(struct inode *inode, bool locked)
	{
	if (unlikely(locked))
	spin_unlock_irq(&inode->i_mapping->tree_lock);

	rcu_read_unlock();
	}

	#else /* CONFIG_CGROUP_WRITEBACK */

	static inline bool inode_cgwb_enabled(struct inode *inode)
	{
	return false;
	}

	static inline struct bdi_writeback_congested *
	wb_congested_get_create(struct backing_dev_info *bdi, int blkcg_id, gfp_t gfp)
	{
	atomic_inc(&bdi->wb_congested->refcnt);
	return bdi->wb_congested;
	}

	static inline void wb_congested_put(struct bdi_writeback_congested *congested)
	{
	if (atomic_dec_and_test(&congested->refcnt))
	kfree(congested);
	}

	static inline struct bdi_writeback wb_find_current(struct backing_dev_info bdi)
	{
	return &bdi->wb;
	}

	static inline struct bdi_writeback *
	wb_get_create_current(struct backing_dev_info *bdi, gfp_t gfp)
	{
	return &bdi->wb;
	}

	static inline bool inode_to_wb_is_valid(struct inode *inode)
	{
	return true;
	}

	static inline struct bdi_writeback inode_to_wb(struct inode inode)
	{
	return &inode_to_bdi(inode)->wb;
	}

	static inline struct bdi_writeback *
	unlocked_inode_to_wb_begin(struct inode inode, bool lockedp)
	{
	return inode_to_wb(inode);
	}

	static inline void unlocked_inode_to_wb_end(struct inode *inode, bool locked)
	{
	}

	static inline void wb_memcg_offline(struct mem_cgroup *memcg)
	{
	}

	static inline void wb_blkcg_offline(struct blkcg *blkcg)
	{
	}

	static inline int inode_congested(struct inode *inode, int cong_bits)
	{
	return wb_congested(&inode_to_bdi(inode)->wb, cong_bits);
	}

	#endif /* CONFIG_CGROUP_WRITEBACK */

	static inline int inode_read_congested(struct inode *inode)
	{
	return inode_congested(inode, 1 << WB_sync_congested);
	}

	static inline int inode_write_congested(struct inode *inode)
	{
	return inode_congested(inode, 1 << WB_async_congested);
	}

	static inline int inode_rw_congested(struct inode *inode)
	{
	return inode_congested(inode, (1 << WB_sync_congested) \|
	(1 << WB_async_congested));
	}

	static inline int bdi_congested(struct backing_dev_info *bdi, int cong_bits)
	{
	return wb_congested(&bdi->wb, cong_bits);
	}

	static inline int bdi_read_congested(struct backing_dev_info *bdi)
	{
	return bdi_congested(bdi, 1 << WB_sync_congested);
	}

	static inline int bdi_write_congested(struct backing_dev_info *bdi)
	{
	return bdi_congested(bdi, 1 << WB_async_congested);
	}

	static inline int bdi_rw_congested(struct backing_dev_info *bdi)
	{
	return bdi_congested(bdi, (1 << WB_sync_congested) \|
	(1 << WB_async_congested));
	}

	#endif /* _LINUX_BACKING_DEV_H */