Merge branch 'for-4.2/writeback' of git://git.kernel.dk/linux-block

Pull cgroup writeback support from Jens Axboe:
 "This is the big pull request for adding cgroup writeback support.

  This code has been in development for a long time, and it has been
  simmering in for-next for a good chunk of this cycle too.  This is one
  of those problems that has been talked about for at least half a
  decade, finally there's a solution and code to go with it.

  Also see last weeks writeup on LWN:

        http://lwn.net/Articles/648292/"

* 'for-4.2/writeback' of git://git.kernel.dk/linux-block: (85 commits)
  writeback, blkio: add documentation for cgroup writeback support
  vfs, writeback: replace FS_CGROUP_WRITEBACK with SB_I_CGROUPWB
  writeback: do foreign inode detection iff cgroup writeback is enabled
  v9fs: fix error handling in v9fs_session_init()
  bdi: fix wrong error return value in cgwb_create()
  buffer: remove unusued 'ret' variable
  writeback: disassociate inodes from dying bdi_writebacks
  writeback: implement foreign cgroup inode bdi_writeback switching
  writeback: add lockdep annotation to inode_to_wb()
  writeback: use unlocked_inode_to_wb transaction in inode_congested()
  writeback: implement unlocked_inode_to_wb transaction and use it for stat updates
  writeback: implement [locked_]inode_to_wb_and_lock_list()
  writeback: implement foreign cgroup inode detection
  writeback: make writeback_control track the inode being written back
  writeback: relocate wb[_try]_get(), wb_put(), inode_{attach|detach}_wb()
  mm: vmscan: disable memcg direct reclaim stalling if cgroup writeback support is in use
  writeback: implement memcg writeback domain based throttling
  writeback: reset wb_domain->dirty_limit[_tstmp] when memcg domain size changes
  writeback: implement memcg wb_domain
  writeback: update wb_over_bg_thresh() to use wb_domain aware operations
  ...

1 files changed, 401 insertions, 156 deletions

diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index d87d8eced064..0e6d4828a77a 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -8,106 +8,13 @@
 #ifndef _LINUX_BACKING_DEV_H
 #define _LINUX_BACKING_DEV_H
 
-#include <linux/percpu_counter.h>
-#include <linux/log2.h>
-#include <linux/flex_proportions.h>
 #include <linux/kernel.h>
 #include <linux/fs.h>
 #include <linux/sched.h>
-#include <linux/timer.h>
+#include <linux/blkdev.h>
 #include <linux/writeback.h>
-#include <linux/atomic.h>
-#include <linux/sysctl.h>
-#include <linux/workqueue.h>
-
-struct page;
-struct device;
-struct dentry;
-
-/*
- * Bits in backing_dev_info.state
- */
-enum bdi_state {
-	BDI_async_congested,	/* The async (write) queue is getting full */
-	BDI_sync_congested,	/* The sync queue is getting full */
-	BDI_registered,		/* bdi_register() was done */
-	BDI_writeback_running,	/* Writeback is in progress */
-};
-
-typedef int (congested_fn)(void *, int);
-
-enum bdi_stat_item {
-	BDI_RECLAIMABLE,
-	BDI_WRITEBACK,
-	BDI_DIRTIED,
-	BDI_WRITTEN,
-	NR_BDI_STAT_ITEMS
-};
-
-#define BDI_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))
-
-struct bdi_writeback {
-	struct backing_dev_info *bdi;	/* our parent bdi */
-
-	unsigned long last_old_flush;	/* last old data flush */
-
-	struct delayed_work dwork;	/* work item used for writeback */
-	struct list_head b_dirty;	/* dirty inodes */
-	struct list_head b_io;		/* parked for writeback */
-	struct list_head b_more_io;	/* parked for more writeback */
-	struct list_head b_dirty_time;	/* time stamps are dirty */
-	spinlock_t list_lock;		/* protects the b_* lists */
-};
-
-struct backing_dev_info {
-	struct list_head bdi_list;
-	unsigned long ra_pages;	/* max readahead in PAGE_CACHE_SIZE units */
-	unsigned long state;	/* Always use atomic bitops on this */
-	unsigned int capabilities; /* Device capabilities */
-	congested_fn *congested_fn; /* Function pointer if device is md/dm */
-	void *congested_data;	/* Pointer to aux data for congested func */
-
-	char *name;
-
-	struct percpu_counter bdi_stat[NR_BDI_STAT_ITEMS];
-
-	unsigned long bw_time_stamp;	/* last time write bw is updated */
-	unsigned long dirtied_stamp;
-	unsigned long written_stamp;	/* pages written at bw_time_stamp */
-	unsigned long write_bandwidth;	/* the estimated write bandwidth */
-	unsigned long avg_write_bandwidth; /* further smoothed write bw */
-
-	/*
-	 * The base dirty throttle rate, re-calculated on every 200ms.
-	 * All the bdi tasks' dirty rate will be curbed under it.
-	 * @dirty_ratelimit tracks the estimated @balanced_dirty_ratelimit
-	 * in small steps and is much more smooth/stable than the latter.
-	 */
-	unsigned long dirty_ratelimit;
-	unsigned long balanced_dirty_ratelimit;
-
-	struct fprop_local_percpu completions;
-	int dirty_exceeded;
-
-	unsigned int min_ratio;
-	unsigned int max_ratio, max_prop_frac;
-
-	struct bdi_writeback wb;  /* default writeback info for this bdi */
-	spinlock_t wb_lock;	  /* protects work_list & wb.dwork scheduling */
-
-	struct list_head work_list;
-
-	struct device *dev;
-
-	struct timer_list laptop_mode_wb_timer;
-
-#ifdef CONFIG_DEBUG_FS
-	struct dentry *debug_dir;
-	struct dentry *debug_stats;
-#endif
-};
-
-struct backing_dev_info *inode_to_bdi(struct inode *inode);
+#include <linux/blk-cgroup.h>
+#include <linux/backing-dev-defs.h>
 
 int __must_check bdi_init(struct backing_dev_info *bdi);
 void bdi_destroy(struct backing_dev_info *bdi);
@@ -117,97 +24,99 @@ 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 __must_check bdi_setup_and_register(struct backing_dev_info *, char *);
-void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
-			enum wb_reason reason);
-void bdi_start_background_writeback(struct backing_dev_info *bdi);
-void bdi_writeback_workfn(struct work_struct *work);
-int bdi_has_dirty_io(struct backing_dev_info *bdi);
-void bdi_wakeup_thread_delayed(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 int wb_has_dirty_io(struct bdi_writeback *wb)
+static inline bool wb_has_dirty_io(struct bdi_writeback *wb)
 {
-	return !list_empty(&wb->b_dirty) ||
-	       !list_empty(&wb->b_io) ||
-	       !list_empty(&wb->b_more_io);
+	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_bdi_stat(struct backing_dev_info *bdi,
-		enum bdi_stat_item item, s64 amount)
+static inline void __add_wb_stat(struct bdi_writeback *wb,
+				 enum wb_stat_item item, s64 amount)
 {
-	__percpu_counter_add(&bdi->bdi_stat[item], amount, BDI_STAT_BATCH);
+	__percpu_counter_add(&wb->stat[item], amount, WB_STAT_BATCH);
 }
 
-static inline void __inc_bdi_stat(struct backing_dev_info *bdi,
-		enum bdi_stat_item item)
+static inline void __inc_wb_stat(struct bdi_writeback *wb,
+				 enum wb_stat_item item)
 {
-	__add_bdi_stat(bdi, item, 1);
+	__add_wb_stat(wb, item, 1);
 }
 
-static inline void inc_bdi_stat(struct backing_dev_info *bdi,
-		enum bdi_stat_item item)
+static inline void inc_wb_stat(struct bdi_writeback *wb, enum wb_stat_item item)
 {
 	unsigned long flags;
 
 	local_irq_save(flags);
-	__inc_bdi_stat(bdi, item);
+	__inc_wb_stat(wb, item);
 	local_irq_restore(flags);
 }
 
-static inline void __dec_bdi_stat(struct backing_dev_info *bdi,
-		enum bdi_stat_item item)
+static inline void __dec_wb_stat(struct bdi_writeback *wb,
+				 enum wb_stat_item item)
 {
-	__add_bdi_stat(bdi, item, -1);
+	__add_wb_stat(wb, item, -1);
 }
 
-static inline void dec_bdi_stat(struct backing_dev_info *bdi,
-		enum bdi_stat_item item)
+static inline void dec_wb_stat(struct bdi_writeback *wb, enum wb_stat_item item)
 {
 	unsigned long flags;
 
 	local_irq_save(flags);
-	__dec_bdi_stat(bdi, item);
+	__dec_wb_stat(wb, item);
 	local_irq_restore(flags);
 }
 
-static inline s64 bdi_stat(struct backing_dev_info *bdi,
-		enum bdi_stat_item item)
+static inline s64 wb_stat(struct bdi_writeback *wb, enum wb_stat_item item)
 {
-	return percpu_counter_read_positive(&bdi->bdi_stat[item]);
+	return percpu_counter_read_positive(&wb->stat[item]);
 }
 
-static inline s64 __bdi_stat_sum(struct backing_dev_info *bdi,
-		enum bdi_stat_item item)
+static inline s64 __wb_stat_sum(struct bdi_writeback *wb,
+				enum wb_stat_item item)
 {
-	return percpu_counter_sum_positive(&bdi->bdi_stat[item]);
+	return percpu_counter_sum_positive(&wb->stat[item]);
 }
 
-static inline s64 bdi_stat_sum(struct backing_dev_info *bdi,
-		enum bdi_stat_item 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 = __bdi_stat_sum(bdi, item);
+	sum = __wb_stat_sum(wb, item);
 	local_irq_restore(flags);
 
 	return sum;
 }
 
-extern void bdi_writeout_inc(struct backing_dev_info *bdi);
+extern void wb_writeout_inc(struct bdi_writeback *wb);
 
 /*
  * maximal error of a stat counter.
  */
-static inline unsigned long bdi_stat_error(struct backing_dev_info *bdi)
+static inline unsigned long wb_stat_error(struct bdi_writeback *wb)
 {
 #ifdef CONFIG_SMP
-	return nr_cpu_ids * BDI_STAT_BATCH;
+	return nr_cpu_ids * WB_STAT_BATCH;
 #else
 	return 1;
 #endif
@@ -231,50 +140,57 @@ int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio);
  * 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;
 
-int writeback_in_progress(struct backing_dev_info *bdi);
-
-static inline int bdi_congested(struct backing_dev_info *bdi, int bdi_bits)
+/**
+ * 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)
 {
-	if (bdi->congested_fn)
-		return bdi->congested_fn(bdi->congested_data, bdi_bits);
-	return (bdi->state & bdi_bits);
+	return test_bit(WB_writeback_running, &wb->state);
 }
 
-static inline int bdi_read_congested(struct backing_dev_info *bdi)
+static inline struct backing_dev_info *inode_to_bdi(struct inode *inode)
 {
-	return bdi_congested(bdi, 1 << BDI_sync_congested);
-}
+	struct super_block *sb;
 
-static inline int bdi_write_congested(struct backing_dev_info *bdi)
-{
-	return bdi_congested(bdi, 1 << BDI_async_congested);
+	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 bdi_rw_congested(struct backing_dev_info *bdi)
+static inline int wb_congested(struct bdi_writeback *wb, int cong_bits)
 {
-	return bdi_congested(bdi, (1 << BDI_sync_congested) |
-				  (1 << BDI_async_congested));
-}
+	struct backing_dev_info *bdi = wb->bdi;
 
-enum {
-	BLK_RW_ASYNC	= 0,
-	BLK_RW_SYNC	= 1,
-};
+	if (bdi->congested_fn)
+		return bdi->congested_fn(bdi->congested_data, cong_bits);
+	return wb->congested->state & cong_bits;
+}
 
-void clear_bdi_congested(struct backing_dev_info *bdi, int sync);
-void set_bdi_congested(struct backing_dev_info *bdi, int sync);
 long congestion_wait(int sync, long timeout);
 long wait_iff_congested(struct zone *zone, int sync, long timeout);
 int pdflush_proc_obsolete(struct ctl_table *table, int write,
@@ -318,4 +234,333 @@ static inline int bdi_sched_wait(void *word)
 	return 0;
 }
 
-#endif		/* _LINUX_BACKING_DEV_H */
+#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.
+ * Test whether @inode has both.
+ */
+static inline bool inode_cgwb_enabled(struct inode *inode)
+{
+	struct backing_dev_info *bdi = inode_to_bdi(inode);
+
+	return 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, blkio_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();
+}
+
+struct wb_iter {
+	int			start_blkcg_id;
+	struct radix_tree_iter	tree_iter;
+	void			**slot;
+};
+
+static inline struct bdi_writeback *__wb_iter_next(struct wb_iter *iter,
+						   struct backing_dev_info *bdi)
+{
+	struct radix_tree_iter *titer = &iter->tree_iter;
+
+	WARN_ON_ONCE(!rcu_read_lock_held());
+
+	if (iter->start_blkcg_id >= 0) {
+		iter->slot = radix_tree_iter_init(titer, iter->start_blkcg_id);
+		iter->start_blkcg_id = -1;
+	} else {
+		iter->slot = radix_tree_next_slot(iter->slot, titer, 0);
+	}
+
+	if (!iter->slot)
+		iter->slot = radix_tree_next_chunk(&bdi->cgwb_tree, titer, 0);
+	if (iter->slot)
+		return *iter->slot;
+	return NULL;
+}
+
+static inline struct bdi_writeback *__wb_iter_init(struct wb_iter *iter,
+						   struct backing_dev_info *bdi,
+						   int start_blkcg_id)
+{
+	iter->start_blkcg_id = start_blkcg_id;
+
+	if (start_blkcg_id)
+		return __wb_iter_next(iter, bdi);
+	else
+		return &bdi->wb;
+}
+
+/**
+ * bdi_for_each_wb - walk all wb's of a bdi in ascending blkcg ID order
+ * @wb_cur: cursor struct bdi_writeback pointer
+ * @bdi: bdi to walk wb's of
+ * @iter: pointer to struct wb_iter to be used as iteration buffer
+ * @start_blkcg_id: blkcg ID to start iteration from
+ *
+ * Iterate @wb_cur through the wb's (bdi_writeback's) of @bdi in ascending
+ * blkcg ID order starting from @start_blkcg_id.  @iter is struct wb_iter
+ * to be used as temp storage during iteration.  rcu_read_lock() must be
+ * held throughout iteration.
+ */
+#define bdi_for_each_wb(wb_cur, bdi, iter, start_blkcg_id)		\
+	for ((wb_cur) = __wb_iter_init(iter, bdi, start_blkcg_id);	\
+	     (wb_cur); (wb_cur) = __wb_iter_next(iter, bdi))
+
+#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)
+{
+	return bdi->wb.congested;
+}
+
+static inline void wb_congested_put(struct bdi_writeback_congested *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)
+{
+}
+
+struct wb_iter {
+	int		next_id;
+};
+
+#define bdi_for_each_wb(wb_cur, bdi, iter, start_blkcg_id)		\
+	for ((iter)->next_id = (start_blkcg_id);			\
+	     ({	(wb_cur) = !(iter)->next_id++ ? &(bdi)->wb : NULL; }); )
+
+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 */