Merge branch 'for-4.3/blkcg' of git://git.kernel.dk/linux-block

Pull blk-cg updates from Jens Axboe:
 "A bit later in the cycle, but this has been in the block tree for a a
  while.  This is basically four patchsets from Tejun, that improve our
  buffered cgroup writeback.  It was dependent on the other cgroup
  changes, but they went in earlier in this cycle.

  Series 1 is set of 5 patches that has cgroup writeback updates:

   - bdi_writeback iteration fix which could lead to some wb's being
     skipped or repeated during e.g. sync under memory pressure.

   - Simplification of wb work wait mechanism.

   - Writeback tracepoints updated to report cgroup.

  Series 2 is is a set of updates for the CFQ cgroup writeback handling:

     cfq has always charged all async IOs to the root cgroup.  It didn't
     have much choice as writeback didn't know about cgroups and there
     was no way to tell who to blame for a given writeback IO.
     writeback finally grew support for cgroups and now tags each
     writeback IO with the appropriate cgroup to charge it against.

     This patchset updates cfq so that it follows the blkcg each bio is
     tagged with.  Async cfq_queues are now shared across cfq_group,
     which is per-cgroup, instead of per-request_queue cfq_data.  This
     makes all IOs follow the weight based IO resource distribution
     implemented by cfq.

     - Switched from GFP_ATOMIC to GFP_NOWAIT as suggested by Jeff.

     - Other misc review points addressed, acks added and rebased.

  Series 3 is the blkcg policy cleanup patches:

     This patchset contains assorted cleanups for blkcg_policy methods
     and blk[c]g_policy_data handling.

     - alloc/free added for blkg_policy_data.  exit dropped.

     - alloc/free added for blkcg_policy_data.

     - blk-throttle's async percpu allocation is replaced with direct
       allocation.

     - all methods now take blk[c]g_policy_data instead of blkcg_gq or
       blkcg.

  And finally, series 4 is a set of patches cleaning up the blkcg stats
  handling:

    blkcg's stats have always been somwhat of a mess.  This patchset
    tries to improve the situation a bit.

     - The following patches added to consolidate blkcg entry point and
       blkg creation.  This is in itself is an improvement and helps
       colllecting common stats on bio issue.

     - per-blkg stats now accounted on bio issue rather than request
       completion so that bio based and request based drivers can behave
       the same way.  The issue was spotted by Vivek.

     - cfq-iosched implements custom recursive stats and blk-throttle
       implements custom per-cpu stats.  This patchset make blkcg core
       support both by default.

     - cfq-iosched and blk-throttle keep track of the same stats
       multiple times.  Unify them"

* 'for-4.3/blkcg' of git://git.kernel.dk/linux-block: (45 commits)
  blkcg: use CGROUP_WEIGHT_* scale for io.weight on the unified hierarchy
  blkcg: s/CFQ_WEIGHT_*/CFQ_WEIGHT_LEGACY_*/
  blkcg: implement interface for the unified hierarchy
  blkcg: misc preparations for unified hierarchy interface
  blkcg: separate out tg_conf_updated() from tg_set_conf()
  blkcg: move body parsing from blkg_conf_prep() to its callers
  blkcg: mark existing cftypes as legacy
  blkcg: rename subsystem name from blkio to io
  blkcg: refine error codes returned during blkcg configuration
  blkcg: remove unnecessary NULL checks from __cfqg_set_weight_device()
  blkcg: reduce stack usage of blkg_rwstat_recursive_sum()
  blkcg: remove cfqg_stats->sectors
  blkcg: move io_service_bytes and io_serviced stats into blkcg_gq
  blkcg: make blkg_[rw]stat_recursive_sum() to be able to index into blkcg_gq
  blkcg: make blkcg_[rw]stat per-cpu
  blkcg: add blkg_[rw]stat->aux_cnt and replace cfq_group->dead_stats with it
  blkcg: consolidate blkg creation in blkcg_bio_issue_check()
  blk-throttle: improve queue bypass handling
  blkcg: move root blkg lookup optimization from throtl_lookup_tg() to __blkg_lookup()
  blkcg: inline [__]blkg_lookup()
  ...

Documentation/cgroups/blkio-controller.txt

@@ -201,7 +201,7 @@ Proportional weight policy files
 	  specifies the number of bytes.
 
 - blkio.io_serviced
-	- Number of IOs completed to/from the disk by the group. These
+	- Number of IOs (bio) issued to the disk by the group. These
 	  are further divided by the type of operation - read or write, sync
 	  or async. First two fields specify the major and minor number of the
 	  device, third field specifies the operation type and the fourth field
@@ -327,18 +327,11 @@ Note: If both BW and IOPS rules are specified for a device, then IO is
       subjected to both the constraints.
 
 - blkio.throttle.io_serviced
-	- Number of IOs (bio) completed to/from the disk by the group (as
-	  seen by throttling policy). These are further divided by the type
-	  of operation - read or write, sync or async. First two fields specify
-	  the major and minor number of the device, third field specifies the
-	  operation type and the fourth field specifies the number of IOs.
-
-	  blkio.io_serviced does accounting as seen by CFQ and counts are in
-	  number of requests (struct request). On the other hand,
-	  blkio.throttle.io_serviced counts number of IO in terms of number
-	  of bios as seen by throttling policy.  These bios can later be
-	  merged by elevator and total number of requests completed can be
-	  lesser.
+	- Number of IOs (bio) issued to the disk by the group. These
+	  are further divided by the type of operation - read or write, sync
+	  or async. First two fields specify the major and minor number of the
+	  device, third field specifies the operation type and the fourth field
+	  specifies the number of IOs.
 
 - blkio.throttle.io_service_bytes
 	- Number of bytes transferred to/from the disk by the group. These
@@ -347,11 +340,6 @@ Note: If both BW and IOPS rules are specified for a device, then IO is
 	  device, third field specifies the operation type and the fourth field
 	  specifies the number of bytes.
 
-	  These numbers should roughly be same as blkio.io_service_bytes as
-	  updated by CFQ. The difference between two is that
-	  blkio.io_service_bytes will not be updated if CFQ is not operating
-	  on request queue.
-
 Common files among various policies
 -----------------------------------
 - blkio.reset_stats

Documentation/cgroups/unified-hierarchy.txt

@@ -27,7 +27,7 @@ CONTENTS
     5-3-1. Format
     5-3-2. Control Knobs
   5-4. Per-Controller Changes
-    5-4-1. blkio
+    5-4-1. io
     5-4-2. cpuset
     5-4-3. memory
 6. Planned Changes
@@ -203,7 +203,7 @@ other issues.  The mapping from nice level to weight isn't obvious or
 universal, and there are various other knobs which simply aren't
 available for tasks.
 
-The blkio controller implicitly creates a hidden leaf node for each
+The io controller implicitly creates a hidden leaf node for each
 cgroup to host the tasks.  The hidden leaf has its own copies of all
 the knobs with "leaf_" prefixed.  While this allows equivalent control
 over internal tasks, it's with serious drawbacks.  It always adds an
@@ -438,9 +438,62 @@ may be specified in any order and not all pairs have to be specified.
 
 5-4. Per-Controller Changes
 
-5-4-1. blkio
+5-4-1. io
 
-- blk-throttle becomes properly hierarchical.
+- blkio is renamed to io.  The interface is overhauled anyway.  The
+  new name is more in line with the other two major controllers, cpu
+  and memory, and better suited given that it may be used for cgroup
+  writeback without involving block layer.
+
+- Everything including stat is always hierarchical making separate
+  recursive stat files pointless and, as no internal node can have
+  tasks, leaf weights are meaningless.  The operation model is
+  simplified and the interface is overhauled accordingly.
+
+  io.stat
+
+	The stat file.  The reported stats are from the point where
+	bio's are issued to request_queue.  The stats are counted
+	independent of which policies are enabled.  Each line in the
+	file follows the following format.  More fields may later be
+	added at the end.
+
+	  $MAJ:$MIN rbytes=$RBYTES wbytes=$WBYTES rios=$RIOS wrios=$WIOS
+
+  io.weight
+
+	The weight setting, currently only available and effective if
+	cfq-iosched is in use for the target device.  The weight is
+	between 1 and 10000 and defaults to 100.  The first line
+	always contains the default weight in the following format to
+	use when per-device setting is missing.
+
+	  default $WEIGHT
+
+	Subsequent lines list per-device weights of the following
+	format.
+
+	  $MAJ:$MIN $WEIGHT
+
+	Writing "$WEIGHT" or "default $WEIGHT" changes the default
+	setting.  Writing "$MAJ:$MIN $WEIGHT" sets per-device weight
+	while "$MAJ:$MIN default" clears it.
+
+	This file is available only on non-root cgroups.
+
+  io.max
+
+	The maximum bandwidth and/or iops setting, only available if
+	blk-throttle is enabled.  The file is of the following format.
+
+	  $MAJ:$MIN rbps=$RBPS wbps=$WBPS riops=$RIOPS wiops=$WIOPS
+
+	${R|W}BPS are read/write bytes per second and ${R|W}IOPS are
+	read/write IOs per second.  "max" indicates no limit.  Writing
+	to the file follows the same format but the individual
+	settings may be ommitted or specified in any order.
+
+	This file is available only on non-root cgroups.
 
 
 5-4-2. cpuset

block/bio.c

@@ -1990,7 +1990,7 @@ int bio_associate_current(struct bio *bio)
 
 	get_io_context_active(ioc);
 	bio->bi_ioc = ioc;
-	bio->bi_css = task_get_css(current, blkio_cgrp_id);
+	bio->bi_css = task_get_css(current, io_cgrp_id);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(bio_associate_current);

block/blk-core.c

@@ -1888,8 +1888,8 @@ generic_make_request_checks(struct bio *bio)
 	 */
 	create_io_context(GFP_ATOMIC, q->node);
 
-	if (blk_throtl_bio(q, bio))
-		return false;	/* throttled, will be resubmitted later */
+	if (!blkcg_bio_issue_check(q, bio))
+		return false;
 
 	trace_block_bio_queue(q, bio);
 	return true;

block/blk.h

@@ -272,15 +272,10 @@ static inline struct io_context *create_io_context(gfp_t gfp_mask, int node)
  * Internal throttling interface
  */
 #ifdef CONFIG_BLK_DEV_THROTTLING
-extern bool blk_throtl_bio(struct request_queue *q, struct bio *bio);
 extern void blk_throtl_drain(struct request_queue *q);
 extern int blk_throtl_init(struct request_queue *q);
 extern void blk_throtl_exit(struct request_queue *q);
 #else /* CONFIG_BLK_DEV_THROTTLING */
-static inline bool blk_throtl_bio(struct request_queue *q, struct bio *bio)
-{
-	return false;
-}
 static inline void blk_throtl_drain(struct request_queue *q) { }
 static inline int blk_throtl_init(struct request_queue *q) { return 0; }
 static inline void blk_throtl_exit(struct request_queue *q) { }

fs/fs-writeback.c

@@ -53,8 +53,6 @@ struct wb_writeback_work {
 	unsigned int for_background:1;
 	unsigned int for_sync:1;	/* sync(2) WB_SYNC_ALL writeback */
 	unsigned int auto_free:1;	/* free on completion */
-	unsigned int single_wait:1;
-	unsigned int single_done:1;
 	enum wb_reason reason;		/* why was writeback initiated? */
 
 	struct list_head list;		/* pending work list */
@@ -178,14 +176,11 @@ static void wb_wakeup(struct bdi_writeback *wb)
 static void wb_queue_work(struct bdi_writeback *wb,
 			  struct wb_writeback_work *work)
 {
-	trace_writeback_queue(wb->bdi, work);
+	trace_writeback_queue(wb, work);
 
 	spin_lock_bh(&wb->work_lock);
-	if (!test_bit(WB_registered, &wb->state)) {
-		if (work->single_wait)
-			work->single_done = 1;
+	if (!test_bit(WB_registered, &wb->state))
 		goto out_unlock;
-	}
 	if (work->done)
 		atomic_inc(&work->done->cnt);
 	list_add_tail(&work->list, &wb->work_list);
@@ -706,7 +701,7 @@ EXPORT_SYMBOL_GPL(wbc_account_io);
 
 /**
  * inode_congested - test whether an inode is congested
- * @inode: inode to test for congestion
+ * @inode: inode to test for congestion (may be NULL)
  * @cong_bits: mask of WB_[a]sync_congested bits to test
  *
  * Tests whether @inode is congested.  @cong_bits is the mask of congestion
@@ -716,6 +711,9 @@ EXPORT_SYMBOL_GPL(wbc_account_io);
  * determined by whether the cgwb (cgroup bdi_writeback) for the blkcg
  * associated with @inode is congested; otherwise, the root wb's congestion
  * state is used.
+ *
+ * @inode is allowed to be NULL as this function is often called on
+ * mapping->host which is NULL for the swapper space.
  */
 int inode_congested(struct inode *inode, int cong_bits)
 {
@@ -737,32 +735,6 @@ int inode_congested(struct inode *inode, int cong_bits)
 }
 EXPORT_SYMBOL_GPL(inode_congested);
 
-/**
- * wb_wait_for_single_work - wait for completion of a single bdi_writeback_work
- * @bdi: bdi the work item was issued to
- * @work: work item to wait for
- *
- * Wait for the completion of @work which was issued to one of @bdi's
- * bdi_writeback's.  The caller must have set @work->single_wait before
- * issuing it.  This wait operates independently fo
- * wb_wait_for_completion() and also disables automatic freeing of @work.
- */
-static void wb_wait_for_single_work(struct backing_dev_info *bdi,
-				    struct wb_writeback_work *work)
-{
-	if (WARN_ON_ONCE(!work->single_wait))
-		return;
-
-	wait_event(bdi->wb_waitq, work->single_done);
-
-	/*
-	 * Paired with smp_wmb() in wb_do_writeback() and ensures that all
-	 * modifications to @work prior to assertion of ->single_done is
-	 * visible to the caller once this function returns.
-	 */
-	smp_rmb();
-}
-
 /**
  * wb_split_bdi_pages - split nr_pages to write according to bandwidth
  * @wb: target bdi_writeback to split @nr_pages to
@@ -791,38 +763,6 @@ static long wb_split_bdi_pages(struct bdi_writeback *wb, long nr_pages)
 		return DIV_ROUND_UP_ULL((u64)nr_pages * this_bw, tot_bw);
 }
 
-/**
- * wb_clone_and_queue_work - clone a wb_writeback_work and issue it to a wb
- * @wb: target bdi_writeback
- * @base_work: source wb_writeback_work
- *
- * Try to make a clone of @base_work and issue it to @wb.  If cloning
- * succeeds, %true is returned; otherwise, @base_work is issued directly
- * and %false is returned.  In the latter case, the caller is required to
- * wait for @base_work's completion using wb_wait_for_single_work().
- *
- * A clone is auto-freed on completion.  @base_work never is.
- */
-static bool wb_clone_and_queue_work(struct bdi_writeback *wb,
-				    struct wb_writeback_work *base_work)
-{
-	struct wb_writeback_work *work;
-
-	work = kmalloc(sizeof(*work), GFP_ATOMIC);
-	if (work) {
-		*work = *base_work;
-		work->auto_free = 1;
-		work->single_wait = 0;
-	} else {
-		work = base_work;
-		work->auto_free = 0;
-		work->single_wait = 1;
-	}
-	work->single_done = 0;
-	wb_queue_work(wb, work);
-	return work != base_work;
-}
-
 /**
  * bdi_split_work_to_wbs - split a wb_writeback_work to all wb's of a bdi
  * @bdi: target backing_dev_info
@@ -838,15 +778,19 @@ static void bdi_split_work_to_wbs(struct backing_dev_info *bdi,
 				  struct wb_writeback_work *base_work,
 				  bool skip_if_busy)
 {
-	long nr_pages = base_work->nr_pages;
-	int next_blkcg_id = 0;
+	int next_memcg_id = 0;
 	struct bdi_writeback *wb;
 	struct wb_iter iter;
 
 	might_sleep();
 restart:
 	rcu_read_lock();
-	bdi_for_each_wb(wb, bdi, &iter, next_blkcg_id) {
+	bdi_for_each_wb(wb, bdi, &iter, next_memcg_id) {
+		DEFINE_WB_COMPLETION_ONSTACK(fallback_work_done);
+		struct wb_writeback_work fallback_work;
+		struct wb_writeback_work *work;
+		long nr_pages;
+
 		/* SYNC_ALL writes out I_DIRTY_TIME too */
 		if (!wb_has_dirty_io(wb) &&
 		    (base_work->sync_mode == WB_SYNC_NONE ||
@@ -855,13 +799,30 @@ restart:
 		if (skip_if_busy && writeback_in_progress(wb))
 			continue;
 
-		base_work->nr_pages = wb_split_bdi_pages(wb, nr_pages);
-		if (!wb_clone_and_queue_work(wb, base_work)) {
-			next_blkcg_id = wb->blkcg_css->id + 1;
-			rcu_read_unlock();
-			wb_wait_for_single_work(bdi, base_work);
-			goto restart;
+		nr_pages = wb_split_bdi_pages(wb, base_work->nr_pages);
+
+		work = kmalloc(sizeof(*work), GFP_ATOMIC);
+		if (work) {
+			*work = *base_work;
+			work->nr_pages = nr_pages;
+			work->auto_free = 1;
+			wb_queue_work(wb, work);
+			continue;
 		}
+
+		/* alloc failed, execute synchronously using on-stack fallback */
+		work = &fallback_work;
+		*work = *base_work;
+		work->nr_pages = nr_pages;
+		work->auto_free = 0;
+		work->done = &fallback_work_done;
+
+		wb_queue_work(wb, work);
+
+		next_memcg_id = wb->memcg_css->id + 1;
+		rcu_read_unlock();
+		wb_wait_for_completion(bdi, &fallback_work_done);
+		goto restart;
 	}
 	rcu_read_unlock();
 }
@@ -902,8 +863,6 @@ static void bdi_split_work_to_wbs(struct backing_dev_info *bdi,
 
 	if (!skip_if_busy || !writeback_in_progress(&bdi->wb)) {
 		base_work->auto_free = 0;
-		base_work->single_wait = 0;
-		base_work->single_done = 0;
 		wb_queue_work(&bdi->wb, base_work);
 	}
 }
@@ -924,7 +883,7 @@ void wb_start_writeback(struct bdi_writeback *wb, long nr_pages,
 	 */
 	work = kzalloc(sizeof(*work), GFP_ATOMIC);
 	if (!work) {
-		trace_writeback_nowork(wb->bdi);
+		trace_writeback_nowork(wb);
 		wb_wakeup(wb);
 		return;
 	}
@@ -954,7 +913,7 @@ void wb_start_background_writeback(struct bdi_writeback *wb)
 	 * We just wake up the flusher thread. It will perform background
 	 * writeback as soon as there is no other work to do.
 	 */
-	trace_writeback_wake_background(wb->bdi);
+	trace_writeback_wake_background(wb);
 	wb_wakeup(wb);
 }
 
@@ -1660,14 +1619,14 @@ static long wb_writeback(struct bdi_writeback *wb,
 		} else if (work->for_background)
 			oldest_jif = jiffies;
 
-		trace_writeback_start(wb->bdi, work);
+		trace_writeback_start(wb, work);
 		if (list_empty(&wb->b_io))
 			queue_io(wb, work);
 		if (work->sb)
 			progress = writeback_sb_inodes(work->sb, wb, work);
 		else
 			progress = __writeback_inodes_wb(wb, work);
-		trace_writeback_written(wb->bdi, work);
+		trace_writeback_written(wb, work);
 
 		wb_update_bandwidth(wb, wb_start);
 
@@ -1692,7 +1651,7 @@ static long wb_writeback(struct bdi_writeback *wb,
 		 * we'll just busyloop.
 		 */
 		if (!list_empty(&wb->b_more_io))  {
-			trace_writeback_wait(wb->bdi, work);
+			trace_writeback_wait(wb, work);
 			inode = wb_inode(wb->b_more_io.prev);
 			spin_lock(&inode->i_lock);
 			spin_unlock(&wb->list_lock);
@@ -1797,26 +1756,14 @@ static long wb_do_writeback(struct bdi_writeback *wb)
 	set_bit(WB_writeback_running, &wb->state);
 	while ((work = get_next_work_item(wb)) != NULL) {
 		struct wb_completion *done = work->done;
-		bool need_wake_up = false;
 
-		trace_writeback_exec(wb->bdi, work);
+		trace_writeback_exec(wb, work);
 
 		wrote += wb_writeback(wb, work);
 
-		if (work->single_wait) {
-			WARN_ON_ONCE(work->auto_free);
-			/* paired w/ rmb in wb_wait_for_single_work() */
-			smp_wmb();
-			work->single_done = 1;
-			need_wake_up = true;
-		} else if (work->auto_free) {
+		if (work->auto_free)
 			kfree(work);
-		}
-
 		if (done && atomic_dec_and_test(&done->cnt))
-			need_wake_up = true;
-
-		if (need_wake_up)
 			wake_up_all(&wb->bdi->wb_waitq);
 	}
 

fs/kernfs/dir.c

@@ -91,6 +91,29 @@ int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen)
 	return ret;
 }
 
+/**
+ * kernfs_path_len - determine the length of the full path of a given node
+ * @kn: kernfs_node of interest
+ *
+ * The returned length doesn't include the space for the terminating '\0'.
+ */
+size_t kernfs_path_len(struct kernfs_node *kn)
+{
+	size_t len = 0;
+	unsigned long flags;
+
+	spin_lock_irqsave(&kernfs_rename_lock, flags);
+
+	do {
+		len += strlen(kn->name) + 1;
+		kn = kn->parent;
+	} while (kn && kn->parent);
+
+	spin_unlock_irqrestore(&kernfs_rename_lock, flags);
+
+	return len;
+}
+
 /**
  * kernfs_path - build full path of a given node
  * @kn: kernfs_node of interest

include/linux/backing-dev.h

@@ -286,7 +286,7 @@ static inline struct bdi_writeback *wb_find_current(struct backing_dev_info *bdi
 	 * %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)))
+	if (likely(wb && wb->blkcg_css == task_css(current, io_cgrp_id)))
 		return wb;
 	return NULL;
 }
@@ -402,7 +402,7 @@ static inline void unlocked_inode_to_wb_end(struct inode *inode, bool locked)
 }
 
 struct wb_iter {
-	int			start_blkcg_id;
+	int			start_memcg_id;
 	struct radix_tree_iter	tree_iter;
 	void			**slot;
 };
@@ -414,9 +414,9 @@ static inline struct bdi_writeback *__wb_iter_next(struct wb_iter *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;
+	if (iter->start_memcg_id >= 0) {
+		iter->slot = radix_tree_iter_init(titer, iter->start_memcg_id);
+		iter->start_memcg_id = -1;
 	} else {
 		iter->slot = radix_tree_next_slot(iter->slot, titer, 0);
 	}
@@ -430,30 +430,30 @@ static inline struct bdi_writeback *__wb_iter_next(struct wb_iter *iter,
 
 static inline struct bdi_writeback *__wb_iter_init(struct wb_iter *iter,
 						   struct backing_dev_info *bdi,
-						   int start_blkcg_id)
+						   int start_memcg_id)
 {
-	iter->start_blkcg_id = start_blkcg_id;
+	iter->start_memcg_id = start_memcg_id;
 
-	if (start_blkcg_id)
+	if (start_memcg_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
+ * bdi_for_each_wb - walk all wb's of a bdi in ascending memcg 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
+ * @start_memcg_id: memcg 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
+ * memcg ID order starting from @start_memcg_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);	\
+#define bdi_for_each_wb(wb_cur, bdi, iter, start_memcg_id)		\
+	for ((wb_cur) = __wb_iter_init(iter, bdi, start_memcg_id);	\
 	     (wb_cur); (wb_cur) = __wb_iter_next(iter, bdi))
 
 #else	/* CONFIG_CGROUP_WRITEBACK */

include/linux/cgroup_subsys.h

@@ -27,7 +27,7 @@ SUBSYS(cpuacct)
 #endif
 
 #if IS_ENABLED(CONFIG_BLK_CGROUP)
-SUBSYS(blkio)
+SUBSYS(io)
 #endif
 
 #if IS_ENABLED(CONFIG_MEMCG)

include/linux/kernfs.h

@@ -266,6 +266,7 @@ static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
 }
 
 int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen);
+size_t kernfs_path_len(struct kernfs_node *kn);
 char * __must_check kernfs_path(struct kernfs_node *kn, char *buf,
 				size_t buflen);
 void pr_cont_kernfs_name(struct kernfs_node *kn);
@@ -332,6 +333,9 @@ static inline bool kernfs_ns_enabled(struct kernfs_node *kn)
 static inline int kernfs_name(struct kernfs_node *kn, char *buf, size_t buflen)
 { return -ENOSYS; }
 
+static inline size_t kernfs_path_len(struct kernfs_node *kn)
+{ return 0; }
+
 static inline char * __must_check kernfs_path(struct kernfs_node *kn, char *buf,
 					      size_t buflen)
 { return NULL; }

include/trace/events/writeback.h

@@ -131,6 +131,66 @@ DEFINE_EVENT(writeback_dirty_inode_template, writeback_dirty_inode,
 	TP_ARGS(inode, flags)
 );
 
+#ifdef CREATE_TRACE_POINTS
+#ifdef CONFIG_CGROUP_WRITEBACK
+
+static inline size_t __trace_wb_cgroup_size(struct bdi_writeback *wb)
+{
+	return kernfs_path_len(wb->memcg_css->cgroup->kn) + 1;
+}
+
+static inline void __trace_wb_assign_cgroup(char *buf, struct bdi_writeback *wb)
+{
+	struct cgroup *cgrp = wb->memcg_css->cgroup;
+	char *path;
+
+	path = cgroup_path(cgrp, buf, kernfs_path_len(cgrp->kn) + 1);
+	WARN_ON_ONCE(path != buf);
+}
+
+static inline size_t __trace_wbc_cgroup_size(struct writeback_control *wbc)
+{
+	if (wbc->wb)
+		return __trace_wb_cgroup_size(wbc->wb);
+	else
+		return 2;
+}
+
+static inline void __trace_wbc_assign_cgroup(char *buf,
+					     struct writeback_control *wbc)
+{
+	if (wbc->wb)
+		__trace_wb_assign_cgroup(buf, wbc->wb);
+	else
+		strcpy(buf, "/");
+}
+
+#else	/* CONFIG_CGROUP_WRITEBACK */
+
+static inline size_t __trace_wb_cgroup_size(struct bdi_writeback *wb)
+{
+	return 2;
+}
+
+static inline void __trace_wb_assign_cgroup(char *buf, struct bdi_writeback *wb)
+{
+	strcpy(buf, "/");
+}
+
+static inline size_t __trace_wbc_cgroup_size(struct writeback_control *wbc)
+{
+	return 2;
+}
+
+static inline void __trace_wbc_assign_cgroup(char *buf,
+					     struct writeback_control *wbc)
+{
+	strcpy(buf, "/");
+}
+
+#endif	/* CONFIG_CGROUP_WRITEBACK */
+#endif	/* CREATE_TRACE_POINTS */
+
 DECLARE_EVENT_CLASS(writeback_write_inode_template,
 
 	TP_PROTO(struct inode *inode, struct writeback_control *wbc),
@@ -141,6 +201,7 @@ DECLARE_EVENT_CLASS(writeback_write_inode_template,
 		__array(char, name, 32)
 		__field(unsigned long, ino)
 		__field(int, sync_mode)
+		__dynamic_array(char, cgroup, __trace_wbc_cgroup_size(wbc))
 	),
 
 	TP_fast_assign(
@@ -148,12 +209,14 @@ DECLARE_EVENT_CLASS(writeback_write_inode_template,
 			dev_name(inode_to_bdi(inode)->dev), 32);
 		__entry->ino		= inode->i_ino;
 		__entry->sync_mode	= wbc->sync_mode;
+		__trace_wbc_assign_cgroup(__get_str(cgroup), wbc);
 	),
 
-	TP_printk("bdi %s: ino=%lu sync_mode=%d",
+	TP_printk("bdi %s: ino=%lu sync_mode=%d cgroup=%s",
 		__entry->name,
 		__entry->ino,
-		__entry->sync_mode
+		__entry->sync_mode,
+		__get_str(cgroup)
 	)
 );
 
@@ -172,8 +235,8 @@ DEFINE_EVENT(writeback_write_inode_template, writeback_write_inode,
 );
 
 DECLARE_EVENT_CLASS(writeback_work_class,
-	TP_PROTO(struct backing_dev_info *bdi, struct wb_writeback_work *work),
-	TP_ARGS(bdi, work),
+	TP_PROTO(struct bdi_writeback *wb, struct wb_writeback_work *work),
+	TP_ARGS(wb, work),
 	TP_STRUCT__entry(
 		__array(char, name, 32)
 		__field(long, nr_pages)
@@ -183,10 +246,11 @@ DECLARE_EVENT_CLASS(writeback_work_class,
 		__field(int, range_cyclic)
 		__field(int, for_background)
 		__field(int, reason)
+		__dynamic_array(char, cgroup, __trace_wb_cgroup_size(wb))
 	),
 	TP_fast_assign(
 		strncpy(__entry->name,
-			bdi->dev ? dev_name(bdi->dev) : "(unknown)", 32);
+			wb->bdi->dev ? dev_name(wb->bdi->dev) : "(unknown)", 32);
 		__entry->nr_pages = work->nr_pages;
 		__entry->sb_dev = work->sb ? work->sb->s_dev : 0;
 		__entry->sync_mode = work->sync_mode;
@@ -194,9 +258,10 @@ DECLARE_EVENT_CLASS(writeback_work_class,
 		__entry->range_cyclic = work->range_cyclic;
 		__entry->for_background	= work->for_background;
 		__entry->reason = work->reason;
+		__trace_wb_assign_cgroup(__get_str(cgroup), wb);
 	),
 	TP_printk("bdi %s: sb_dev %d:%d nr_pages=%ld sync_mode=%d "
-		  "kupdate=%d range_cyclic=%d background=%d reason=%s",
+		  "kupdate=%d range_cyclic=%d background=%d reason=%s cgroup=%s",
 		  __entry->name,
 		  MAJOR(__entry->sb_dev), MINOR(__entry->sb_dev),
 		  __entry->nr_pages,
@@ -204,13 +269,14 @@ DECLARE_EVENT_CLASS(writeback_work_class,
 		  __entry->for_kupdate,
 		  __entry->range_cyclic,
 		  __entry->for_background,
-		  __print_symbolic(__entry->reason, WB_WORK_REASON)
+		  __print_symbolic(__entry->reason, WB_WORK_REASON),
+		  __get_str(cgroup)
 	)
 );
 #define DEFINE_WRITEBACK_WORK_EVENT(name) \
 DEFINE_EVENT(writeback_work_class, name, \
-	TP_PROTO(struct backing_dev_info *bdi, struct wb_writeback_work *work), \
-	TP_ARGS(bdi, work))
+	TP_PROTO(struct bdi_writeback *wb, struct wb_writeback_work *work), \
+	TP_ARGS(wb, work))
 DEFINE_WRITEBACK_WORK_EVENT(writeback_queue);
 DEFINE_WRITEBACK_WORK_EVENT(writeback_exec);
 DEFINE_WRITEBACK_WORK_EVENT(writeback_start);
@@ -230,6 +296,30 @@ TRACE_EVENT(writeback_pages_written,
 );
 
 DECLARE_EVENT_CLASS(writeback_class,
+	TP_PROTO(struct bdi_writeback *wb),
+	TP_ARGS(wb),
+	TP_STRUCT__entry(
+		__array(char, name, 32)
+		__dynamic_array(char, cgroup, __trace_wb_cgroup_size(wb))
+	),
+	TP_fast_assign(
+		strncpy(__entry->name, dev_name(wb->bdi->dev), 32);
+		__trace_wb_assign_cgroup(__get_str(cgroup), wb);
+	),
+	TP_printk("bdi %s: cgroup=%s",
+		  __entry->name,
+		  __get_str(cgroup)
+	)
+);
+#define DEFINE_WRITEBACK_EVENT(name) \
+DEFINE_EVENT(writeback_class, name, \
+	TP_PROTO(struct bdi_writeback *wb), \
+	TP_ARGS(wb))
+
+DEFINE_WRITEBACK_EVENT(writeback_nowork);
+DEFINE_WRITEBACK_EVENT(writeback_wake_background);
+
+TRACE_EVENT(writeback_bdi_register,
 	TP_PROTO(struct backing_dev_info *bdi),
 	TP_ARGS(bdi),
 	TP_STRUCT__entry(
@@ -239,17 +329,9 @@ DECLARE_EVENT_CLASS(writeback_class,
 		strncpy(__entry->name, dev_name(bdi->dev), 32);
 	),
 	TP_printk("bdi %s",
-		  __entry->name
+		__entry->name
 	)
 );
-#define DEFINE_WRITEBACK_EVENT(name) \
-DEFINE_EVENT(writeback_class, name, \
-	TP_PROTO(struct backing_dev_info *bdi), \
-	TP_ARGS(bdi))
-
-DEFINE_WRITEBACK_EVENT(writeback_nowork);
-DEFINE_WRITEBACK_EVENT(writeback_wake_background);
-DEFINE_WRITEBACK_EVENT(writeback_bdi_register);
 
 DECLARE_EVENT_CLASS(wbc_class,
 	TP_PROTO(struct writeback_control *wbc, struct backing_dev_info *bdi),
@@ -265,6 +347,7 @@ DECLARE_EVENT_CLASS(wbc_class,
 		__field(int, range_cyclic)
 		__field(long, range_start)
 		__field(long, range_end)
+		__dynamic_array(char, cgroup, __trace_wbc_cgroup_size(wbc))
 	),
 
 	TP_fast_assign(
@@ -278,11 +361,12 @@ DECLARE_EVENT_CLASS(wbc_class,
 		__entry->range_cyclic	= wbc->range_cyclic;
 		__entry->range_start	= (long)wbc->range_start;
 		__entry->range_end	= (long)wbc->range_end;
+		__trace_wbc_assign_cgroup(__get_str(cgroup), wbc);
 	),
 
 	TP_printk("bdi %s: towrt=%ld skip=%ld mode=%d kupd=%d "
 		"bgrd=%d reclm=%d cyclic=%d "
-		"start=0x%lx end=0x%lx",
+		"start=0x%lx end=0x%lx cgroup=%s",
 		__entry->name,
 		__entry->nr_to_write,
 		__entry->pages_skipped,
@@ -292,7 +376,9 @@ DECLARE_EVENT_CLASS(wbc_class,
 		__entry->for_reclaim,
 		__entry->range_cyclic,
 		__entry->range_start,
-		__entry->range_end)
+		__entry->range_end,
+		__get_str(cgroup)
+	)
 )
 
 #define DEFINE_WBC_EVENT(name) \
@@ -312,6 +398,7 @@ TRACE_EVENT(writeback_queue_io,
 		__field(long,		age)
 		__field(int,		moved)
 		__field(int,		reason)
+		__dynamic_array(char, cgroup, __trace_wb_cgroup_size(wb))
 	),
 	TP_fast_assign(
 		unsigned long *older_than_this = work->older_than_this;
@@ -321,13 +408,15 @@ TRACE_EVENT(writeback_queue_io,
 				  (jiffies - *older_than_this) * 1000 / HZ : -1;
 		__entry->moved	= moved;
 		__entry->reason	= work->reason;
+		__trace_wb_assign_cgroup(__get_str(cgroup), wb);
 	),
-	TP_printk("bdi %s: older=%lu age=%ld enqueue=%d reason=%s",
+	TP_printk("bdi %s: older=%lu age=%ld enqueue=%d reason=%s cgroup=%s",
 		__entry->name,
 		__entry->older,	/* older_than_this in jiffies */
 		__entry->age,	/* older_than_this in relative milliseconds */
 		__entry->moved,
-		__print_symbolic(__entry->reason, WB_WORK_REASON)
+		__print_symbolic(__entry->reason, WB_WORK_REASON),
+		__get_str(cgroup)
 	)
 );
 
@@ -381,11 +470,11 @@ TRACE_EVENT(global_dirty_state,
 
 TRACE_EVENT(bdi_dirty_ratelimit,
 
-	TP_PROTO(struct backing_dev_info *bdi,
+	TP_PROTO(struct bdi_writeback *wb,
 		 unsigned long dirty_rate,
 		 unsigned long task_ratelimit),
 
-	TP_ARGS(bdi, dirty_rate, task_ratelimit),
+	TP_ARGS(wb, dirty_rate, task_ratelimit),
 
 	TP_STRUCT__entry(
 		__array(char,		bdi, 32)
@@ -395,36 +484,39 @@ TRACE_EVENT(bdi_dirty_ratelimit,
 		__field(unsigned long,	dirty_ratelimit)
 		__field(unsigned long,	task_ratelimit)
 		__field(unsigned long,	balanced_dirty_ratelimit)
+		__dynamic_array(char, cgroup, __trace_wb_cgroup_size(wb))
 	),
 
 	TP_fast_assign(
-		strlcpy(__entry->bdi, dev_name(bdi->dev), 32);
-		__entry->write_bw	= KBps(bdi->wb.write_bandwidth);
-		__entry->avg_write_bw	= KBps(bdi->wb.avg_write_bandwidth);
+		strlcpy(__entry->bdi, dev_name(wb->bdi->dev), 32);
+		__entry->write_bw	= KBps(wb->write_bandwidth);
+		__entry->avg_write_bw	= KBps(wb->avg_write_bandwidth);
 		__entry->dirty_rate	= KBps(dirty_rate);
-		__entry->dirty_ratelimit = KBps(bdi->wb.dirty_ratelimit);
+		__entry->dirty_ratelimit = KBps(wb->dirty_ratelimit);
 		__entry->task_ratelimit	= KBps(task_ratelimit);
 		__entry->balanced_dirty_ratelimit =
-					KBps(bdi->wb.balanced_dirty_ratelimit);
+					KBps(wb->balanced_dirty_ratelimit);
+		__trace_wb_assign_cgroup(__get_str(cgroup), wb);
 	),
 
 	TP_printk("bdi %s: "
 		  "write_bw=%lu awrite_bw=%lu dirty_rate=%lu "
 		  "dirty_ratelimit=%lu task_ratelimit=%lu "
-		  "balanced_dirty_ratelimit=%lu",
+		  "balanced_dirty_ratelimit=%lu cgroup=%s",
 		  __entry->bdi,
 		  __entry->write_bw,		/* write bandwidth */
 		  __entry->avg_write_bw,	/* avg write bandwidth */
 		  __entry->dirty_rate,		/* bdi dirty rate */
 		  __entry->dirty_ratelimit,	/* base ratelimit */
 		  __entry->task_ratelimit, /* ratelimit with position control */
-		  __entry->balanced_dirty_ratelimit /* the balanced ratelimit */
+		  __entry->balanced_dirty_ratelimit, /* the balanced ratelimit */
+		  __get_str(cgroup)
 	)
 );
 
 TRACE_EVENT(balance_dirty_pages,
 
-	TP_PROTO(struct backing_dev_info *bdi,
+	TP_PROTO(struct bdi_writeback *wb,
 		 unsigned long thresh,
 		 unsigned long bg_thresh,
 		 unsigned long dirty,
@@ -437,7 +529,7 @@ TRACE_EVENT(balance_dirty_pages,
 		 long pause,
 		 unsigned long start_time),
 
-	TP_ARGS(bdi, thresh, bg_thresh, dirty, bdi_thresh, bdi_dirty,
+	TP_ARGS(wb, thresh, bg_thresh, dirty, bdi_thresh, bdi_dirty,
 		dirty_ratelimit, task_ratelimit,
 		dirtied, period, pause, start_time),
 
@@ -456,11 +548,12 @@ TRACE_EVENT(balance_dirty_pages,
 		__field(	 long,	pause)
 		__field(unsigned long,	period)
 		__field(	 long,	think)
+		__dynamic_array(char, cgroup, __trace_wb_cgroup_size(wb))
 	),
 
 	TP_fast_assign(
 		unsigned long freerun = (thresh + bg_thresh) / 2;
-		strlcpy(__entry->bdi, dev_name(bdi->dev), 32);
+		strlcpy(__entry->bdi, dev_name(wb->bdi->dev), 32);
 
 		__entry->limit		= global_wb_domain.dirty_limit;
 		__entry->setpoint	= (global_wb_domain.dirty_limit +
@@ -478,6 +571,7 @@ TRACE_EVENT(balance_dirty_pages,
 		__entry->period		= period * 1000 / HZ;
 		__entry->pause		= pause * 1000 / HZ;
 		__entry->paused		= (jiffies - start_time) * 1000 / HZ;
+		__trace_wb_assign_cgroup(__get_str(cgroup), wb);
 	),
 
 
@@ -486,7 +580,7 @@ TRACE_EVENT(balance_dirty_pages,
 		  "bdi_setpoint=%lu bdi_dirty=%lu "
 		  "dirty_ratelimit=%lu task_ratelimit=%lu "
 		  "dirtied=%u dirtied_pause=%u "
-		  "paused=%lu pause=%ld period=%lu think=%ld",
+		  "paused=%lu pause=%ld period=%lu think=%ld cgroup=%s",
 		  __entry->bdi,
 		  __entry->limit,
 		  __entry->setpoint,
@@ -500,7 +594,8 @@ TRACE_EVENT(balance_dirty_pages,
 		  __entry->paused,	/* ms */
 		  __entry->pause,	/* ms */
 		  __entry->period,	/* ms */
-		  __entry->think	/* ms */
+		  __entry->think,	/* ms */
+		  __get_str(cgroup)
 	  )
 );
 
@@ -514,6 +609,8 @@ TRACE_EVENT(writeback_sb_inodes_requeue,
 		__field(unsigned long, ino)
 		__field(unsigned long, state)
 		__field(unsigned long, dirtied_when)
+		__dynamic_array(char, cgroup,
+				__trace_wb_cgroup_size(inode_to_wb(inode)))
 	),
 
 	TP_fast_assign(
@@ -522,14 +619,16 @@ TRACE_EVENT(writeback_sb_inodes_requeue,
 		__entry->ino		= inode->i_ino;
 		__entry->state		= inode->i_state;
 		__entry->dirtied_when	= inode->dirtied_when;
+		__trace_wb_assign_cgroup(__get_str(cgroup), inode_to_wb(inode));
 	),
 
-	TP_printk("bdi %s: ino=%lu state=%s dirtied_when=%lu age=%lu",
+	TP_printk("bdi %s: ino=%lu state=%s dirtied_when=%lu age=%lu cgroup=%s",
 		  __entry->name,
 		  __entry->ino,
 		  show_inode_state(__entry->state),
 		  __entry->dirtied_when,
-		  (jiffies - __entry->dirtied_when) / HZ
+		  (jiffies - __entry->dirtied_when) / HZ,
+		  __get_str(cgroup)
 	)
 );
 
@@ -585,6 +684,7 @@ DECLARE_EVENT_CLASS(writeback_single_inode_template,
 		__field(unsigned long, writeback_index)
 		__field(long, nr_to_write)
 		__field(unsigned long, wrote)
+		__dynamic_array(char, cgroup, __trace_wbc_cgroup_size(wbc))
 	),
 
 	TP_fast_assign(
@@ -596,10 +696,11 @@ DECLARE_EVENT_CLASS(writeback_single_inode_template,
 		__entry->writeback_index = inode->i_mapping->writeback_index;
 		__entry->nr_to_write	= nr_to_write;
 		__entry->wrote		= nr_to_write - wbc->nr_to_write;
+		__trace_wbc_assign_cgroup(__get_str(cgroup), wbc);
 	),
 
 	TP_printk("bdi %s: ino=%lu state=%s dirtied_when=%lu age=%lu "
-		  "index=%lu to_write=%ld wrote=%lu",
+		  "index=%lu to_write=%ld wrote=%lu cgroup=%s",
 		  __entry->name,
 		  __entry->ino,
 		  show_inode_state(__entry->state),
@@ -607,7 +708,8 @@ DECLARE_EVENT_CLASS(writeback_single_inode_template,
 		  (jiffies - __entry->dirtied_when) / HZ,
 		  __entry->writeback_index,
 		  __entry->nr_to_write,
-		  __entry->wrote
+		  __entry->wrote,
+		  __get_str(cgroup)
 	)
 );
 

mm/backing-dev.c

@@ -523,7 +523,7 @@ static int cgwb_create(struct backing_dev_info *bdi,
 	int ret = 0;
 
 	memcg = mem_cgroup_from_css(memcg_css);
-	blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &blkio_cgrp_subsys);
+	blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
 	blkcg = css_to_blkcg(blkcg_css);
 	memcg_cgwb_list = mem_cgroup_cgwb_list(memcg);
 	blkcg_cgwb_list = &blkcg->cgwb_list;
@@ -645,7 +645,7 @@ struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
 
 			/* see whether the blkcg association has changed */
 			blkcg_css = cgroup_get_e_css(memcg_css->cgroup,
-						     &blkio_cgrp_subsys);
+						     &io_cgrp_subsys);
 			if (unlikely(wb->blkcg_css != blkcg_css ||
 				     !wb_tryget(wb)))
 				wb = NULL;

mm/page-writeback.c

@@ -1289,7 +1289,7 @@ static void wb_update_dirty_ratelimit(struct dirty_throttle_control *dtc,
 	wb->dirty_ratelimit = max(dirty_ratelimit, 1UL);
 	wb->balanced_dirty_ratelimit = balanced_dirty_ratelimit;
 
-	trace_bdi_dirty_ratelimit(wb->bdi, dirty_rate, task_ratelimit);
+	trace_bdi_dirty_ratelimit(wb, dirty_rate, task_ratelimit);
 }
 
 static void __wb_update_bandwidth(struct dirty_throttle_control *gdtc,
@@ -1683,7 +1683,7 @@ static void balance_dirty_pages(struct address_space *mapping,
 		 * do a reset, as it may be a light dirtier.
 		 */
 		if (pause < min_pause) {
-			trace_balance_dirty_pages(bdi,
+			trace_balance_dirty_pages(wb,
 						  sdtc->thresh,
 						  sdtc->bg_thresh,
 						  sdtc->dirty,
@@ -1712,7 +1712,7 @@ static void balance_dirty_pages(struct address_space *mapping,
 		}
 
 pause:
-		trace_balance_dirty_pages(bdi,
+		trace_balance_dirty_pages(wb,
 					  sdtc->thresh,
 					  sdtc->bg_thresh,
 					  sdtc->dirty,