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, 508 insertions, 126 deletions

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 000e7b3b9896..7756da31b02b 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -18,6 +18,7 @@ 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;
 
@@ -48,7 +49,7 @@ static int bdi_debug_stats_show(struct seq_file *m, void *v)
 	struct bdi_writeback *wb = &bdi->wb;
 	unsigned long background_thresh;
 	unsigned long dirty_thresh;
-	unsigned long bdi_thresh;
+	unsigned long wb_thresh;
 	unsigned long nr_dirty, nr_io, nr_more_io, nr_dirty_time;
 	struct inode *inode;
 
@@ -66,7 +67,7 @@ static int bdi_debug_stats_show(struct seq_file *m, void *v)
 	spin_unlock(&wb->list_lock);
 
 	global_dirty_limits(&background_thresh, &dirty_thresh);
-	bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh);
+	wb_thresh = wb_calc_thresh(wb, dirty_thresh);
 
 #define K(x) ((x) << (PAGE_SHIFT - 10))
 	seq_printf(m,
@@ -84,19 +85,19 @@ static int bdi_debug_stats_show(struct seq_file *m, void *v)
 		   "b_dirty_time:       %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),
+		   (unsigned long) K(wb_stat(wb, WB_WRITEBACK)),
+		   (unsigned long) K(wb_stat(wb, WB_RECLAIMABLE)),
+		   K(wb_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),
+		   (unsigned long) K(wb_stat(wb, WB_DIRTIED)),
+		   (unsigned long) K(wb_stat(wb, WB_WRITTEN)),
+		   (unsigned long) K(wb->write_bandwidth),
 		   nr_dirty,
 		   nr_io,
 		   nr_more_io,
 		   nr_dirty_time,
-		   !list_empty(&bdi->bdi_list), bdi->state);
+		   !list_empty(&bdi->bdi_list), bdi->wb.state);
 #undef K
 
 	return 0;
@@ -255,13 +256,8 @@ static int __init default_bdi_init(void)
 }
 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
+ * This function is used when the first inode for this wb 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
@@ -274,162 +270,550 @@ int bdi_has_dirty_io(struct backing_dev_info *bdi)
  * We have to be careful not to postpone flush work if it is scheduled for
  * earlier. Thus we use queue_delayed_work().
  */
-void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi)
+void wb_wakeup_delayed(struct bdi_writeback *wb)
 {
 	unsigned long timeout;
 
 	timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
-	spin_lock_bh(&bdi->wb_lock);
-	if (test_bit(BDI_registered, &bdi->state))
-		queue_delayed_work(bdi_wq, &bdi->wb.dwork, timeout);
-	spin_unlock_bh(&bdi->wb_lock);
+	spin_lock_bh(&wb->work_lock);
+	if (test_bit(WB_registered, &wb->state))
+		queue_delayed_work(bdi_wq, &wb->dwork, timeout);
+	spin_unlock_bh(&wb->work_lock);
 }
 
 /*
- * Remove bdi from bdi_list, and ensure that it is no longer visible
+ * Initial write bandwidth: 100 MB/s
  */
-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();
-}
+#define INIT_BW		(100 << (20 - PAGE_SHIFT))
 
-int bdi_register(struct backing_dev_info *bdi, struct device *parent,
-		const char *fmt, ...)
+static int wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi,
+		   gfp_t gfp)
 {
-	va_list args;
-	struct device *dev;
+	int i, err;
 
-	if (bdi->dev)	/* The driver needs to use separate queues per device */
-		return 0;
+	memset(wb, 0, sizeof(*wb));
 
-	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);
+	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);
+	INIT_LIST_HEAD(&wb->b_dirty_time);
+	spin_lock_init(&wb->list_lock);
 
-	bdi->dev = dev;
+	wb->bw_time_stamp = jiffies;
+	wb->balanced_dirty_ratelimit = INIT_BW;
+	wb->dirty_ratelimit = INIT_BW;
+	wb->write_bandwidth = INIT_BW;
+	wb->avg_write_bandwidth = INIT_BW;
 
-	bdi_debug_register(bdi, dev_name(dev));
-	set_bit(BDI_registered, &bdi->state);
+	spin_lock_init(&wb->work_lock);
+	INIT_LIST_HEAD(&wb->work_list);
+	INIT_DELAYED_WORK(&wb->dwork, wb_workfn);
 
-	spin_lock_bh(&bdi_lock);
-	list_add_tail_rcu(&bdi->bdi_list, &bdi_list);
-	spin_unlock_bh(&bdi_lock);
+	err = fprop_local_init_percpu(&wb->completions, gfp);
+	if (err)
+		return err;
 
-	trace_writeback_bdi_register(bdi);
-	return 0;
-}
-EXPORT_SYMBOL(bdi_register);
+	for (i = 0; i < NR_WB_STAT_ITEMS; i++) {
+		err = percpu_counter_init(&wb->stat[i], 0, gfp);
+		if (err) {
+			while (--i)
+				percpu_counter_destroy(&wb->stat[i]);
+			fprop_local_destroy_percpu(&wb->completions);
+			return err;
+		}
+	}
 
-int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
-{
-	return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
+	return 0;
 }
-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)
+static void wb_shutdown(struct bdi_writeback *wb)
 {
 	/* Make sure nobody queues further work */
-	spin_lock_bh(&bdi->wb_lock);
-	if (!test_and_clear_bit(BDI_registered, &bdi->state)) {
-		spin_unlock_bh(&bdi->wb_lock);
+	spin_lock_bh(&wb->work_lock);
+	if (!test_and_clear_bit(WB_registered, &wb->state)) {
+		spin_unlock_bh(&wb->work_lock);
 		return;
 	}
-	spin_unlock_bh(&bdi->wb_lock);
+	spin_unlock_bh(&wb->work_lock);
 
 	/*
-	 * Make sure nobody finds us on the bdi_list anymore
+	 * Drain work list and shutdown the delayed_work.  !WB_registered
+	 * tells wb_workfn() that @wb is dying and its work_list needs to
+	 * be drained no matter what.
 	 */
-	bdi_remove_from_list(bdi);
+	mod_delayed_work(bdi_wq, &wb->dwork, 0);
+	flush_delayed_work(&wb->dwork);
+	WARN_ON(!list_empty(&wb->work_list));
+}
+
+static void wb_exit(struct bdi_writeback *wb)
+{
+	int i;
+
+	WARN_ON(delayed_work_pending(&wb->dwork));
+
+	for (i = 0; i < NR_WB_STAT_ITEMS; i++)
+		percpu_counter_destroy(&wb->stat[i]);
+
+	fprop_local_destroy_percpu(&wb->completions);
+}
+
+#ifdef CONFIG_CGROUP_WRITEBACK
+
+#include <linux/memcontrol.h>
+
+/*
+ * cgwb_lock protects bdi->cgwb_tree, bdi->cgwb_congested_tree,
+ * blkcg->cgwb_list, and memcg->cgwb_list.  bdi->cgwb_tree is also RCU
+ * protected.  cgwb_release_wait is used to wait for the completion of cgwb
+ * releases from bdi destruction path.
+ */
+static DEFINE_SPINLOCK(cgwb_lock);
+static DECLARE_WAIT_QUEUE_HEAD(cgwb_release_wait);
+
+/**
+ * wb_congested_get_create - get or create a wb_congested
+ * @bdi: associated bdi
+ * @blkcg_id: ID of the associated blkcg
+ * @gfp: allocation mask
+ *
+ * Look up the wb_congested for @blkcg_id on @bdi.  If missing, create one.
+ * The returned wb_congested has its reference count incremented.  Returns
+ * NULL on failure.
+ */
+struct bdi_writeback_congested *
+wb_congested_get_create(struct backing_dev_info *bdi, int blkcg_id, gfp_t gfp)
+{
+	struct bdi_writeback_congested *new_congested = NULL, *congested;
+	struct rb_node **node, *parent;
+	unsigned long flags;
+
+	if (blkcg_id == 1)
+		return &bdi->wb_congested;
+retry:
+	spin_lock_irqsave(&cgwb_lock, flags);
+
+	node = &bdi->cgwb_congested_tree.rb_node;
+	parent = NULL;
+
+	while (*node != NULL) {
+		parent = *node;
+		congested = container_of(parent, struct bdi_writeback_congested,
+					 rb_node);
+		if (congested->blkcg_id < blkcg_id)
+			node = &parent->rb_left;
+		else if (congested->blkcg_id > blkcg_id)
+			node = &parent->rb_right;
+		else
+			goto found;
+	}
+
+	if (new_congested) {
+		/* !found and storage for new one already allocated, insert */
+		congested = new_congested;
+		new_congested = NULL;
+		rb_link_node(&congested->rb_node, parent, node);
+		rb_insert_color(&congested->rb_node, &bdi->cgwb_congested_tree);
+		atomic_inc(&bdi->usage_cnt);
+		goto found;
+	}
+
+	spin_unlock_irqrestore(&cgwb_lock, flags);
+
+	/* allocate storage for new one and retry */
+	new_congested = kzalloc(sizeof(*new_congested), gfp);
+	if (!new_congested)
+		return NULL;
+
+	atomic_set(&new_congested->refcnt, 0);
+	new_congested->bdi = bdi;
+	new_congested->blkcg_id = blkcg_id;
+	goto retry;
+
+found:
+	atomic_inc(&congested->refcnt);
+	spin_unlock_irqrestore(&cgwb_lock, flags);
+	kfree(new_congested);
+	return congested;
+}
+
+/**
+ * wb_congested_put - put a wb_congested
+ * @congested: wb_congested to put
+ *
+ * Put @congested and destroy it if the refcnt reaches zero.
+ */
+void wb_congested_put(struct bdi_writeback_congested *congested)
+{
+	struct backing_dev_info *bdi = congested->bdi;
+	unsigned long flags;
+
+	if (congested->blkcg_id == 1)
+		return;
+
+	local_irq_save(flags);
+	if (!atomic_dec_and_lock(&congested->refcnt, &cgwb_lock)) {
+		local_irq_restore(flags);
+		return;
+	}
+
+	rb_erase(&congested->rb_node, &congested->bdi->cgwb_congested_tree);
+	spin_unlock_irqrestore(&cgwb_lock, flags);
+	kfree(congested);
+
+	if (atomic_dec_and_test(&bdi->usage_cnt))
+		wake_up_all(&cgwb_release_wait);
+}
+
+static void cgwb_release_workfn(struct work_struct *work)
+{
+	struct bdi_writeback *wb = container_of(work, struct bdi_writeback,
+						release_work);
+	struct backing_dev_info *bdi = wb->bdi;
+
+	wb_shutdown(wb);
+
+	css_put(wb->memcg_css);
+	css_put(wb->blkcg_css);
+	wb_congested_put(wb->congested);
+
+	fprop_local_destroy_percpu(&wb->memcg_completions);
+	percpu_ref_exit(&wb->refcnt);
+	wb_exit(wb);
+	kfree_rcu(wb, rcu);
+
+	if (atomic_dec_and_test(&bdi->usage_cnt))
+		wake_up_all(&cgwb_release_wait);
+}
+
+static void cgwb_release(struct percpu_ref *refcnt)
+{
+	struct bdi_writeback *wb = container_of(refcnt, struct bdi_writeback,
+						refcnt);
+	schedule_work(&wb->release_work);
+}
+
+static void cgwb_kill(struct bdi_writeback *wb)
+{
+	lockdep_assert_held(&cgwb_lock);
+
+	WARN_ON(!radix_tree_delete(&wb->bdi->cgwb_tree, wb->memcg_css->id));
+	list_del(&wb->memcg_node);
+	list_del(&wb->blkcg_node);
+	percpu_ref_kill(&wb->refcnt);
+}
+
+static int cgwb_create(struct backing_dev_info *bdi,
+		       struct cgroup_subsys_state *memcg_css, gfp_t gfp)
+{
+	struct mem_cgroup *memcg;
+	struct cgroup_subsys_state *blkcg_css;
+	struct blkcg *blkcg;
+	struct list_head *memcg_cgwb_list, *blkcg_cgwb_list;
+	struct bdi_writeback *wb;
+	unsigned long flags;
+	int ret = 0;
+
+	memcg = mem_cgroup_from_css(memcg_css);
+	blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &blkio_cgrp_subsys);
+	blkcg = css_to_blkcg(blkcg_css);
+	memcg_cgwb_list = mem_cgroup_cgwb_list(memcg);
+	blkcg_cgwb_list = &blkcg->cgwb_list;
+
+	/* look up again under lock and discard on blkcg mismatch */
+	spin_lock_irqsave(&cgwb_lock, flags);
+	wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
+	if (wb && wb->blkcg_css != blkcg_css) {
+		cgwb_kill(wb);
+		wb = NULL;
+	}
+	spin_unlock_irqrestore(&cgwb_lock, flags);
+	if (wb)
+		goto out_put;
+
+	/* need to create a new one */
+	wb = kmalloc(sizeof(*wb), gfp);
+	if (!wb)
+		return -ENOMEM;
+
+	ret = wb_init(wb, bdi, gfp);
+	if (ret)
+		goto err_free;
+
+	ret = percpu_ref_init(&wb->refcnt, cgwb_release, 0, gfp);
+	if (ret)
+		goto err_wb_exit;
+
+	ret = fprop_local_init_percpu(&wb->memcg_completions, gfp);
+	if (ret)
+		goto err_ref_exit;
+
+	wb->congested = wb_congested_get_create(bdi, blkcg_css->id, gfp);
+	if (!wb->congested) {
+		ret = -ENOMEM;
+		goto err_fprop_exit;
+	}
+
+	wb->memcg_css = memcg_css;
+	wb->blkcg_css = blkcg_css;
+	INIT_WORK(&wb->release_work, cgwb_release_workfn);
+	set_bit(WB_registered, &wb->state);
 
 	/*
-	 * 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.
+	 * The root wb determines the registered state of the whole bdi and
+	 * memcg_cgwb_list and blkcg_cgwb_list's next pointers indicate
+	 * whether they're still online.  Don't link @wb if any is dead.
+	 * See wb_memcg_offline() and wb_blkcg_offline().
 	 */
-	mod_delayed_work(bdi_wq, &bdi->wb.dwork, 0);
-	flush_delayed_work(&bdi->wb.dwork);
+	ret = -ENODEV;
+	spin_lock_irqsave(&cgwb_lock, flags);
+	if (test_bit(WB_registered, &bdi->wb.state) &&
+	    blkcg_cgwb_list->next && memcg_cgwb_list->next) {
+		/* we might have raced another instance of this function */
+		ret = radix_tree_insert(&bdi->cgwb_tree, memcg_css->id, wb);
+		if (!ret) {
+			atomic_inc(&bdi->usage_cnt);
+			list_add(&wb->memcg_node, memcg_cgwb_list);
+			list_add(&wb->blkcg_node, blkcg_cgwb_list);
+			css_get(memcg_css);
+			css_get(blkcg_css);
+		}
+	}
+	spin_unlock_irqrestore(&cgwb_lock, flags);
+	if (ret) {
+		if (ret == -EEXIST)
+			ret = 0;
+		goto err_put_congested;
+	}
+	goto out_put;
+
+err_put_congested:
+	wb_congested_put(wb->congested);
+err_fprop_exit:
+	fprop_local_destroy_percpu(&wb->memcg_completions);
+err_ref_exit:
+	percpu_ref_exit(&wb->refcnt);
+err_wb_exit:
+	wb_exit(wb);
+err_free:
+	kfree(wb);
+out_put:
+	css_put(blkcg_css);
+	return ret;
 }
 
-static void bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
+/**
+ * wb_get_create - get wb for a given memcg, create if necessary
+ * @bdi: target bdi
+ * @memcg_css: cgroup_subsys_state of the target memcg (must have positive ref)
+ * @gfp: allocation mask to use
+ *
+ * Try to get the wb for @memcg_css on @bdi.  If it doesn't exist, try to
+ * create one.  The returned wb has its refcount incremented.
+ *
+ * This function uses css_get() on @memcg_css and thus expects its refcnt
+ * to be positive on invocation.  IOW, rcu_read_lock() protection on
+ * @memcg_css isn't enough.  try_get it before calling this function.
+ *
+ * A wb is keyed by its associated memcg.  As blkcg implicitly enables
+ * memcg on the default hierarchy, memcg association is guaranteed to be
+ * more specific (equal or descendant to the associated blkcg) and thus can
+ * identify both the memcg and blkcg associations.
+ *
+ * Because the blkcg associated with a memcg may change as blkcg is enabled
+ * and disabled closer to root in the hierarchy, each wb keeps track of
+ * both the memcg and blkcg associated with it and verifies the blkcg on
+ * each lookup.  On mismatch, the existing wb is discarded and a new one is
+ * created.
+ */
+struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
+				    struct cgroup_subsys_state *memcg_css,
+				    gfp_t gfp)
 {
-	memset(wb, 0, sizeof(*wb));
+	struct bdi_writeback *wb;
+
+	might_sleep_if(gfp & __GFP_WAIT);
+
+	if (!memcg_css->parent)
+		return &bdi->wb;
+
+	do {
+		rcu_read_lock();
+		wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
+		if (wb) {
+			struct cgroup_subsys_state *blkcg_css;
+
+			/* see whether the blkcg association has changed */
+			blkcg_css = cgroup_get_e_css(memcg_css->cgroup,
+						     &blkio_cgrp_subsys);
+			if (unlikely(wb->blkcg_css != blkcg_css ||
+				     !wb_tryget(wb)))
+				wb = NULL;
+			css_put(blkcg_css);
+		}
+		rcu_read_unlock();
+	} while (!wb && !cgwb_create(bdi, memcg_css, gfp));
+
+	return 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);
-	INIT_LIST_HEAD(&wb->b_dirty_time);
-	spin_lock_init(&wb->list_lock);
-	INIT_DELAYED_WORK(&wb->dwork, bdi_writeback_workfn);
+static void cgwb_bdi_init(struct backing_dev_info *bdi)
+{
+	bdi->wb.memcg_css = mem_cgroup_root_css;
+	bdi->wb.blkcg_css = blkcg_root_css;
+	bdi->wb_congested.blkcg_id = 1;
+	INIT_RADIX_TREE(&bdi->cgwb_tree, GFP_ATOMIC);
+	bdi->cgwb_congested_tree = RB_ROOT;
+	atomic_set(&bdi->usage_cnt, 1);
 }
 
-/*
- * Initial write bandwidth: 100 MB/s
+static void cgwb_bdi_destroy(struct backing_dev_info *bdi)
+{
+	struct radix_tree_iter iter;
+	void **slot;
+
+	WARN_ON(test_bit(WB_registered, &bdi->wb.state));
+
+	spin_lock_irq(&cgwb_lock);
+	radix_tree_for_each_slot(slot, &bdi->cgwb_tree, &iter, 0)
+		cgwb_kill(*slot);
+	spin_unlock_irq(&cgwb_lock);
+
+	/*
+	 * All cgwb's and their congested states must be shutdown and
+	 * released before returning.  Drain the usage counter to wait for
+	 * all cgwb's and cgwb_congested's ever created on @bdi.
+	 */
+	atomic_dec(&bdi->usage_cnt);
+	wait_event(cgwb_release_wait, !atomic_read(&bdi->usage_cnt));
+}
+
+/**
+ * wb_memcg_offline - kill all wb's associated with a memcg being offlined
+ * @memcg: memcg being offlined
+ *
+ * Also prevents creation of any new wb's associated with @memcg.
  */
-#define INIT_BW		(100 << (20 - PAGE_SHIFT))
+void wb_memcg_offline(struct mem_cgroup *memcg)
+{
+	LIST_HEAD(to_destroy);
+	struct list_head *memcg_cgwb_list = mem_cgroup_cgwb_list(memcg);
+	struct bdi_writeback *wb, *next;
+
+	spin_lock_irq(&cgwb_lock);
+	list_for_each_entry_safe(wb, next, memcg_cgwb_list, memcg_node)
+		cgwb_kill(wb);
+	memcg_cgwb_list->next = NULL;	/* prevent new wb's */
+	spin_unlock_irq(&cgwb_lock);
+}
+
+/**
+ * wb_blkcg_offline - kill all wb's associated with a blkcg being offlined
+ * @blkcg: blkcg being offlined
+ *
+ * Also prevents creation of any new wb's associated with @blkcg.
+ */
+void wb_blkcg_offline(struct blkcg *blkcg)
+{
+	LIST_HEAD(to_destroy);
+	struct bdi_writeback *wb, *next;
+
+	spin_lock_irq(&cgwb_lock);
+	list_for_each_entry_safe(wb, next, &blkcg->cgwb_list, blkcg_node)
+		cgwb_kill(wb);
+	blkcg->cgwb_list.next = NULL;	/* prevent new wb's */
+	spin_unlock_irq(&cgwb_lock);
+}
+
+#else	/* CONFIG_CGROUP_WRITEBACK */
+
+static void cgwb_bdi_init(struct backing_dev_info *bdi) { }
+static void cgwb_bdi_destroy(struct backing_dev_info *bdi) { }
+
+#endif	/* CONFIG_CGROUP_WRITEBACK */
 
 int bdi_init(struct backing_dev_info *bdi)
 {
-	int i, err;
+	int 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);
+	init_waitqueue_head(&bdi->wb_waitq);
 
-	bdi_wb_init(&bdi->wb, bdi);
+	err = wb_init(&bdi->wb, bdi, GFP_KERNEL);
+	if (err)
+		return err;
 
-	for (i = 0; i < NR_BDI_STAT_ITEMS; i++) {
-		err = percpu_counter_init(&bdi->bdi_stat[i], 0, GFP_KERNEL);
-		if (err)
-			goto err;
-	}
+	bdi->wb_congested.state = 0;
+	bdi->wb.congested = &bdi->wb_congested;
 
-	bdi->dirty_exceeded = 0;
+	cgwb_bdi_init(bdi);
+	return 0;
+}
+EXPORT_SYMBOL(bdi_init);
 
-	bdi->bw_time_stamp = jiffies;
-	bdi->written_stamp = 0;
+int bdi_register(struct backing_dev_info *bdi, struct device *parent,
+		const char *fmt, ...)
+{
+	va_list args;
+	struct device *dev;
 
-	bdi->balanced_dirty_ratelimit = INIT_BW;
-	bdi->dirty_ratelimit = INIT_BW;
-	bdi->write_bandwidth = INIT_BW;
-	bdi->avg_write_bandwidth = INIT_BW;
+	if (bdi->dev)	/* The driver needs to use separate queues per device */
+		return 0;
 
-	err = fprop_local_init_percpu(&bdi->completions, GFP_KERNEL);
+	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);
 
-	if (err) {
-err:
-		while (i--)
-			percpu_counter_destroy(&bdi->bdi_stat[i]);
-	}
+	bdi->dev = dev;
 
-	return err;
+	bdi_debug_register(bdi, dev_name(dev));
+	set_bit(WB_registered, &bdi->wb.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_init);
+EXPORT_SYMBOL(bdi_register);
 
-void bdi_destroy(struct backing_dev_info *bdi)
+int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev)
 {
-	int i;
+	return bdi_register(bdi, NULL, "%u:%u", MAJOR(dev), MINOR(dev));
+}
+EXPORT_SYMBOL(bdi_register_dev);
+
+/*
+ * 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);
 
-	bdi_wb_shutdown(bdi);
-	bdi_set_min_ratio(bdi, 0);
+	synchronize_rcu_expedited();
+}
 
-	WARN_ON(!list_empty(&bdi->work_list));
-	WARN_ON(delayed_work_pending(&bdi->wb.dwork));
+void bdi_destroy(struct backing_dev_info *bdi)
+{
+	/* make sure nobody finds us on the bdi_list anymore */
+	bdi_remove_from_list(bdi);
+	wb_shutdown(&bdi->wb);
+	cgwb_bdi_destroy(bdi);
 
 	if (bdi->dev) {
 		bdi_debug_unregister(bdi);
@@ -437,9 +821,7 @@ void bdi_destroy(struct backing_dev_info *bdi)
 		bdi->dev = NULL;
 	}
 
-	for (i = 0; i < NR_BDI_STAT_ITEMS; i++)
-		percpu_counter_destroy(&bdi->bdi_stat[i]);
-	fprop_local_destroy_percpu(&bdi->completions);
+	wb_exit(&bdi->wb);
 }
 EXPORT_SYMBOL(bdi_destroy);
 
@@ -472,31 +854,31 @@ static wait_queue_head_t congestion_wqh[2] = {
 		__WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[0]),
 		__WAIT_QUEUE_HEAD_INITIALIZER(congestion_wqh[1])
 	};
-static atomic_t nr_bdi_congested[2];
+static atomic_t nr_wb_congested[2];
 
-void clear_bdi_congested(struct backing_dev_info *bdi, int sync)
+void clear_wb_congested(struct bdi_writeback_congested *congested, int sync)
 {
-	enum bdi_state bit;
 	wait_queue_head_t *wqh = &congestion_wqh[sync];
+	enum wb_state bit;
 
-	bit = sync ? BDI_sync_congested : BDI_async_congested;
-	if (test_and_clear_bit(bit, &bdi->state))
-		atomic_dec(&nr_bdi_congested[sync]);
+	bit = sync ? WB_sync_congested : WB_async_congested;
+	if (test_and_clear_bit(bit, &congested->state))
+		atomic_dec(&nr_wb_congested[sync]);
 	smp_mb__after_atomic();
 	if (waitqueue_active(wqh))
 		wake_up(wqh);
 }
-EXPORT_SYMBOL(clear_bdi_congested);
+EXPORT_SYMBOL(clear_wb_congested);
 
-void set_bdi_congested(struct backing_dev_info *bdi, int sync)
+void set_wb_congested(struct bdi_writeback_congested *congested, int sync)
 {
-	enum bdi_state bit;
+	enum wb_state bit;
 
-	bit = sync ? BDI_sync_congested : BDI_async_congested;
-	if (!test_and_set_bit(bit, &bdi->state))
-		atomic_inc(&nr_bdi_congested[sync]);
+	bit = sync ? WB_sync_congested : WB_async_congested;
+	if (!test_and_set_bit(bit, &congested->state))
+		atomic_inc(&nr_wb_congested[sync]);
 }
-EXPORT_SYMBOL(set_bdi_congested);
+EXPORT_SYMBOL(set_wb_congested);
 
 /**
  * congestion_wait - wait for a backing_dev to become uncongested
@@ -555,7 +937,7 @@ long wait_iff_congested(struct zone *zone, int sync, long timeout)
 	 * encountered in the current zone, yield if necessary instead
 	 * of sleeping on the congestion queue
 	 */
-	if (atomic_read(&nr_bdi_congested[sync]) == 0 ||
+	if (atomic_read(&nr_wb_congested[sync]) == 0 ||
 	    !test_bit(ZONE_CONGESTED, &zone->flags)) {
 		cond_resched();