blkcg: move block/blk-cgroup.h to include/linux/blk-cgroup.h

Currently, a bio can only be associated with the io_context and blkcg of %current using bio_associate_current(). This is too restrictive for cgroup writeback support. Implement bio_associate_blkcg() which associates a bio with the specified blkcg.

bio_associate_blkcg() leaves the io_context unassociated. bio_associate_current() is updated so that it considers a bio as already associated if it has a blkcg_css, instead of an io_context, associated with it.

Signed-off-by Tejun Heo <[email protected]>

Cc Jens Axboe <[email protected]>

Cc Vivek Goyal <[email protected]>

---
 block/bio.c         |   24 +++++++++++++++++++++++-
 include/linux/bio.h |    3 +++
 2 files changed, 26 insertions(+), 1 deletion(-)

block/bio.c +22 -0

@@ -1981,6 +1981,28 @@ struct bio_set *bioset_create_nobvec(uns
 EXPORT_SYMBOL(bioset_create_nobvec);
 
 #ifdef CONFIG_BLK_CGROUP
+
+/**
+ * bio_associate_blkcg - associate a bio with the specified blkcg
+ * @bio: target bio
+ * @blkcg_css: the css of the blkcg to associate
+ *
+ * Associate @bio with the blkcg specified by @blkcg_css.  Block layer will
+ * treat @bio as if it were issued by a task which belongs to the blkcg.
+ *
+ * This function takes an extra reference of @blkcg_css which will be put
+ * when @bio is released.  The caller must own @bio and is responsible for
+ * synchronizing calls to this function.
+ */
+int bio_associate_blkcg(struct bio *bio, struct cgroup_subsys_state *blkcg_css)
+{
+	if (unlikely(bio->bi_css))
+		return -EBUSY;
+	css_get(blkcg_css);
+	bio->bi_css = blkcg_css;
+	return 0;
+}
+
 /**
  * bio_associate_current - associate a bio with %current
  * @bio: target bio

Not sure what can be done about this. May be a notion of per block cgroup per device io context and always use that io context when bio has cgroup info but not io context info.

bio_associate_current() currently open codes task_css() and css_tryget_online() to find and pin $current's blkcg css. Abstract it into task_get_css() which is implemented from cgroup side. As a task is always associated with an online css for every subsystem except while the css_set update is propagating, task_get_css() retries till css_tryget_online() succeeds.

This is a cleanup and shouldn't lead to noticeable behavior changes.

Signed-off-by Tejun Heo <[email protected]>

Cc Li Zefan <[email protected]>

Cc Jens Axboe <[email protected]>

Cc Vivek Goyal <[email protected]>

---
Hello,

This one can be routed through either cgroup or block tree but I think it'd be easier to route this through block as there will be more block changes in the area.

Thanks.

 block/bio.c            |   11 +----------
 include/linux/cgroup.h |   25 +++++++++++++++++++++++++
 2 files changed, 26 insertions(+), 10 deletions(-)

block/bio.c +1 -10

@@ -1997,7 +1997,6 @@ EXPORT_SYMBOL(bioset_create_nobvec);
 int bio_associate_current(struct bio *bio)
 {
 	struct io_context *ioc;
-	struct cgroup_subsys_state *css;
 
 	if (bio->bi_ioc)
 		return -EBUSY;

@@ -2006,17 +2005,9 @@ int bio_associate_current(struct bio *bi
 	if (!ioc)
 		return -ENOENT;
 
-	/* acquire active ref on @ioc and associate */
 	get_io_context_active(ioc);
 	bio->bi_ioc = ioc;
-
-	/* associate blkcg if exists */
-	rcu_read_lock();
-	css = task_css(current, blkio_cgrp_id);
-	if (css && css_tryget_online(css))
-		bio->bi_css = css;
-	rcu_read_unlock();
-
+	bio->bi_css = task_get_css(current, blkio_cgrp_id);
 	return 0;
 }
 

include/linux/cgroup.h +25 -0

@@ -748,6 +748,31 @@ static inline struct cgroup_subsys_state
 }
 
 /**
+ * task_get_css - find and get the css for (task, subsys)
+ * @task: the target task
+ * @subsys_id: the target subsystem ID
+ *
+ * Find the css for the (@task, @subsys_id) combination, increment a
+ * reference on and return it.  This function is guaranteed to return a
+ * valid css.
+ */
+static inline struct cgroup_subsys_state *
+task_get_css(struct task_struct *task, int subsys_id)
+{
+	struct cgroup_subsys_state *css;
+
+	rcu_read_lock();
+	while (true) {
+		css = task_css(task, subsys_id);
+		if (likely(css_tryget_online(css)))
+			break;
+		cpu_relax();
+	}
+	rcu_read_unlock();
+	return css;
+}
+
+/**
  * task_css_is_root - test whether a task belongs to the root css
  * @task: the target task
  * @subsys_id: the target subsystem ID

On Mon, Nov 17, 2014 at 04:13:57PM -0500, Tejun Heo wrote:
[..]

Quoted 5 lines

include/linux/blkdev.h +0 -0

@@ -1408,6 +1408,9 @@ int kblockd_schedule_delayed_work(struct
 int kblockd_schedule_delayed_work_on(int cpu, struct delayed_work *dwork, unsigned long delay);
 

include/linux/blkdev.h int kblockd_schedule_delayed_work(struct · line 1412

Quoted 3 lines

include/linux/blkdev.h +2 -0

 #ifdef CONFIG_BLK_CGROUP
+
+extern struct cgroup_subsys_state * const blkcg_root_css;

Hi Tejun,

Would it make sense to keep this in include/linux/blk-cgroup.h

cgroup aware writeback support will require exposing some of blkcg details. In preprataion, move block/blk-cgroup.h to include/linux/blk-cgroup.h. This patch is pure file move.

Signed-off-by Tejun Heo <[email protected]>

Cc Vivek Goyal <[email protected]>

---
Hello, Jens.

These four are misc prep patches on blkcg for cgroup writeback support.

Thanks.

 block/blk-cgroup.c         |    2 
 block/blk-cgroup.h         |  603 ---------------------------------------------
 block/blk-core.c           |    2 
 block/blk-sysfs.c          |    2 
 block/blk-throttle.c       |    2 
 block/cfq-iosched.c        |    2 
 block/elevator.c           |    2 
 include/linux/blk-cgroup.h |  603 +++++++++++++++++++++++++++++++++++++++++++++
 8 files changed, 609 insertions(+), 609 deletions(-)

block/blk-cgroup.c +1 -1

@@ -19,7 +19,7 @@
 #include <linux/genhd.h>
 #include <linux/delay.h>
 #include <linux/atomic.h>
-#include "blk-cgroup.h"
+#include <linux/blk-cgroup.h>
 #include "blk.h"
 
 #define MAX_KEY_LEN 100

block/blk-cgroup.h deleted +0 -603

@@ -1,603 +0,0 @@
-#ifndef _BLK_CGROUP_H
-#define _BLK_CGROUP_H
-/*
- * Common Block IO controller cgroup interface
- *
- * Based on ideas and code from CFQ, CFS and BFQ:
- * Copyright (C) 2003 Jens Axboe <[email protected]>
- *
- * Copyright (C) 2008 Fabio Checconi <[email protected]>
- *		      Paolo Valente <[email protected]>
- *
- * Copyright (C) 2009 Vivek Goyal <[email protected]>
- * 	              Nauman Rafique <[email protected]>
- */
-
-#include <linux/cgroup.h>
-#include <linux/u64_stats_sync.h>
-#include <linux/seq_file.h>
-#include <linux/radix-tree.h>
-#include <linux/blkdev.h>
-#include <linux/atomic.h>
-
-/* Max limits for throttle policy */
-#define THROTL_IOPS_MAX		UINT_MAX
-
-/* CFQ specific, out here for blkcg->cfq_weight */
-#define CFQ_WEIGHT_MIN		10
-#define CFQ_WEIGHT_MAX		1000
-#define CFQ_WEIGHT_DEFAULT	500
-
-#ifdef CONFIG_BLK_CGROUP
-
-enum blkg_rwstat_type {
-	BLKG_RWSTAT_READ,
-	BLKG_RWSTAT_WRITE,
-	BLKG_RWSTAT_SYNC,
-	BLKG_RWSTAT_ASYNC,
-
-	BLKG_RWSTAT_NR,
-	BLKG_RWSTAT_TOTAL = BLKG_RWSTAT_NR,
-};
-
-struct blkcg_gq;
-
-struct blkcg {
-	struct cgroup_subsys_state	css;
-	spinlock_t			lock;
-
-	struct radix_tree_root		blkg_tree;
-	struct blkcg_gq			*blkg_hint;
-	struct hlist_head		blkg_list;
-
-	/* TODO: per-policy storage in blkcg */
-	unsigned int			cfq_weight;	/* belongs to cfq */
-	unsigned int			cfq_leaf_weight;
-};
-
-struct blkg_stat {
-	struct u64_stats_sync		syncp;
-	uint64_t			cnt;
-};
-
-struct blkg_rwstat {
-	struct u64_stats_sync		syncp;
-	uint64_t			cnt[BLKG_RWSTAT_NR];
-};
-
-/*
- * A blkcg_gq (blkg) is association between a block cgroup (blkcg) and a
- * request_queue (q).  This is used by blkcg policies which need to track
- * information per blkcg - q pair.
- *
- * There can be multiple active blkcg policies and each has its private
- * data on each blkg, the size of which is determined by
- * blkcg_policy->pd_size.  blkcg core allocates and frees such areas
- * together with blkg and invokes pd_init/exit_fn() methods.
- *
- * Such private data must embed struct blkg_policy_data (pd) at the
- * beginning and pd_size can't be smaller than pd.
- */
-struct blkg_policy_data {
-	/* the blkg and policy id this per-policy data belongs to */
-	struct blkcg_gq			*blkg;
-	int				plid;
-
-	/* used during policy activation */
-	struct list_head		alloc_node;
-};
-
-/* association between a blk cgroup and a request queue */
-struct blkcg_gq {
-	/* Pointer to the associated request_queue */
-	struct request_queue		*q;
-	struct list_head		q_node;
-	struct hlist_node		blkcg_node;
-	struct blkcg			*blkcg;
-
-	/* all non-root blkcg_gq's are guaranteed to have access to parent */
-	struct blkcg_gq			*parent;
-
-	/* request allocation list for this blkcg-q pair */
-	struct request_list		rl;
-
-	/* reference count */
-	atomic_t			refcnt;
-
-	/* is this blkg online? protected by both blkcg and q locks */
-	bool				online;
-
-	struct blkg_policy_data		*pd[BLKCG_MAX_POLS];
-
-	struct rcu_head			rcu_head;
-};
-
-typedef void (blkcg_pol_init_pd_fn)(struct blkcg_gq *blkg);
-typedef void (blkcg_pol_online_pd_fn)(struct blkcg_gq *blkg);
-typedef void (blkcg_pol_offline_pd_fn)(struct blkcg_gq *blkg);
-typedef void (blkcg_pol_exit_pd_fn)(struct blkcg_gq *blkg);
-typedef void (blkcg_pol_reset_pd_stats_fn)(struct blkcg_gq *blkg);
-
-struct blkcg_policy {
-	int				plid;
-	/* policy specific private data size */
-	size_t				pd_size;
-	/* cgroup files for the policy */
-	struct cftype			*cftypes;
-
-	/* operations */
-	blkcg_pol_init_pd_fn		*pd_init_fn;
-	blkcg_pol_online_pd_fn		*pd_online_fn;
-	blkcg_pol_offline_pd_fn		*pd_offline_fn;
-	blkcg_pol_exit_pd_fn		*pd_exit_fn;
-	blkcg_pol_reset_pd_stats_fn	*pd_reset_stats_fn;
-};
-
-extern struct blkcg blkcg_root;
-
-struct blkcg_gq *blkg_lookup(struct blkcg *blkcg, struct request_queue *q);
-struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
-				    struct request_queue *q);
-int blkcg_init_queue(struct request_queue *q);
-void blkcg_drain_queue(struct request_queue *q);
-void blkcg_exit_queue(struct request_queue *q);
-
-/* Blkio controller policy registration */
-int blkcg_policy_register(struct blkcg_policy *pol);
-void blkcg_policy_unregister(struct blkcg_policy *pol);
-int blkcg_activate_policy(struct request_queue *q,
-			  const struct blkcg_policy *pol);
-void blkcg_deactivate_policy(struct request_queue *q,
-			     const struct blkcg_policy *pol);
-
-void blkcg_print_blkgs(struct seq_file *sf, struct blkcg *blkcg,
-		       u64 (*prfill)(struct seq_file *,
-				     struct blkg_policy_data *, int),
-		       const struct blkcg_policy *pol, int data,
-		       bool show_total);
-u64 __blkg_prfill_u64(struct seq_file *sf, struct blkg_policy_data *pd, u64 v);
-u64 __blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
-			 const struct blkg_rwstat *rwstat);
-u64 blkg_prfill_stat(struct seq_file *sf, struct blkg_policy_data *pd, int off);
-u64 blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
-		       int off);
-
-u64 blkg_stat_recursive_sum(struct blkg_policy_data *pd, int off);
-struct blkg_rwstat blkg_rwstat_recursive_sum(struct blkg_policy_data *pd,
-					     int off);
-
-struct blkg_conf_ctx {
-	struct gendisk			*disk;
-	struct blkcg_gq			*blkg;
-	u64				v;
-};
-
-int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
-		   const char *input, struct blkg_conf_ctx *ctx);
-void blkg_conf_finish(struct blkg_conf_ctx *ctx);
-
-
-static inline struct blkcg *css_to_blkcg(struct cgroup_subsys_state *css)
-{
-	return css ? container_of(css, struct blkcg, css) : NULL;
-}
-
-static inline struct blkcg *task_blkcg(struct task_struct *tsk)
-{
-	return css_to_blkcg(task_css(tsk, blkio_cgrp_id));
-}
-
-static inline struct blkcg *bio_blkcg(struct bio *bio)
-{
-	if (bio && bio->bi_css)
-		return css_to_blkcg(bio->bi_css);
-	return task_blkcg(current);
-}
-
-/**
- * blkcg_parent - get the parent of a blkcg
- * @blkcg: blkcg of interest
- *
- * Return the parent blkcg of @blkcg.  Can be called anytime.
- */
-static inline struct blkcg *blkcg_parent(struct blkcg *blkcg)
-{
-	return css_to_blkcg(blkcg->css.parent);
-}
-
-/**
- * blkg_to_pdata - get policy private data
- * @blkg: blkg of interest
- * @pol: policy of interest
- *
- * Return pointer to private data associated with the @blkg-@pol pair.
- */
-static inline struct blkg_policy_data *blkg_to_pd(struct blkcg_gq *blkg,
-						  struct blkcg_policy *pol)
-{
-	return blkg ? blkg->pd[pol->plid] : NULL;
-}
-
-/**
- * pdata_to_blkg - get blkg associated with policy private data
- * @pd: policy private data of interest
- *
- * @pd is policy private data.  Determine the blkg it's associated with.
- */
-static inline struct blkcg_gq *pd_to_blkg(struct blkg_policy_data *pd)
-{
-	return pd ? pd->blkg : NULL;
-}
-
-/**
- * blkg_path - format cgroup path of blkg
- * @blkg: blkg of interest
- * @buf: target buffer
- * @buflen: target buffer length
- *
- * Format the path of the cgroup of @blkg into @buf.
- */
-static inline int blkg_path(struct blkcg_gq *blkg, char *buf, int buflen)
-{
-	char *p;
-
-	p = cgroup_path(blkg->blkcg->css.cgroup, buf, buflen);
-	if (!p) {
-		strncpy(buf, "<unavailable>", buflen);
-		return -ENAMETOOLONG;
-	}
-
-	memmove(buf, p, buf + buflen - p);
-	return 0;
-}
-
-/**
- * blkg_get - get a blkg reference
- * @blkg: blkg to get
- *
- * The caller should be holding an existing reference.
- */
-static inline void blkg_get(struct blkcg_gq *blkg)
-{
-	WARN_ON_ONCE(atomic_read(&blkg->refcnt) <= 0);
-	atomic_inc(&blkg->refcnt);
-}
-
-void __blkg_release_rcu(struct rcu_head *rcu);
-
-/**
- * blkg_put - put a blkg reference
- * @blkg: blkg to put
- */
-static inline void blkg_put(struct blkcg_gq *blkg)
-{
-	WARN_ON_ONCE(atomic_read(&blkg->refcnt) <= 0);
-	if (atomic_dec_and_test(&blkg->refcnt))
-		call_rcu(&blkg->rcu_head, __blkg_release_rcu);
-}
-
-struct blkcg_gq *__blkg_lookup(struct blkcg *blkcg, struct request_queue *q,
-			       bool update_hint);
-
-/**
- * blkg_for_each_descendant_pre - pre-order walk of a blkg's descendants
- * @d_blkg: loop cursor pointing to the current descendant
- * @pos_css: used for iteration
- * @p_blkg: target blkg to walk descendants of
- *
- * Walk @c_blkg through the descendants of @p_blkg.  Must be used with RCU
- * read locked.  If called under either blkcg or queue lock, the iteration
- * is guaranteed to include all and only online blkgs.  The caller may
- * update @pos_css by calling css_rightmost_descendant() to skip subtree.
- * @p_blkg is included in the iteration and the first node to be visited.
- */
-#define blkg_for_each_descendant_pre(d_blkg, pos_css, p_blkg)		\
-	css_for_each_descendant_pre((pos_css), &(p_blkg)->blkcg->css)	\
-		if (((d_blkg) = __blkg_lookup(css_to_blkcg(pos_css),	\
-					      (p_blkg)->q, false)))
-
-/**
- * blkg_for_each_descendant_post - post-order walk of a blkg's descendants
- * @d_blkg: loop cursor pointing to the current descendant
- * @pos_css: used for iteration
- * @p_blkg: target blkg to walk descendants of
- *
- * Similar to blkg_for_each_descendant_pre() but performs post-order
- * traversal instead.  Synchronization rules are the same.  @p_blkg is
- * included in the iteration and the last node to be visited.
- */
-#define blkg_for_each_descendant_post(d_blkg, pos_css, p_blkg)		\
-	css_for_each_descendant_post((pos_css), &(p_blkg)->blkcg->css)	\
-		if (((d_blkg) = __blkg_lookup(css_to_blkcg(pos_css),	\
-					      (p_blkg)->q, false)))
-
-/**
- * blk_get_rl - get request_list to use
- * @q: request_queue of interest
- * @bio: bio which will be attached to the allocated request (may be %NULL)
- *
- * The caller wants to allocate a request from @q to use for @bio.  Find
- * the request_list to use and obtain a reference on it.  Should be called
- * under queue_lock.  This function is guaranteed to return non-%NULL
- * request_list.
- */
-static inline struct request_list *blk_get_rl(struct request_queue *q,
-					      struct bio *bio)
-{
-	struct blkcg *blkcg;
-	struct blkcg_gq *blkg;
-
-	rcu_read_lock();
-
-	blkcg = bio_blkcg(bio);
-
-	/* bypass blkg lookup and use @q->root_rl directly for root */
-	if (blkcg == &blkcg_root)
-		goto root_rl;
-
-	/*
-	 * Try to use blkg->rl.  blkg lookup may fail under memory pressure
-	 * or if either the blkcg or queue is going away.  Fall back to
-	 * root_rl in such cases.
-	 */
-	blkg = blkg_lookup_create(blkcg, q);
-	if (unlikely(IS_ERR(blkg)))
-		goto root_rl;
-
-	blkg_get(blkg);
-	rcu_read_unlock();
-	return &blkg->rl;
-root_rl:
-	rcu_read_unlock();
-	return &q->root_rl;
-}
-
-/**
- * blk_put_rl - put request_list
- * @rl: request_list to put
- *
- * Put the reference acquired by blk_get_rl().  Should be called under
- * queue_lock.
- */
-static inline void blk_put_rl(struct request_list *rl)
-{
-	/* root_rl may not have blkg set */
-	if (rl->blkg && rl->blkg->blkcg != &blkcg_root)
-		blkg_put(rl->blkg);
-}
-
-/**
- * blk_rq_set_rl - associate a request with a request_list
- * @rq: request of interest
- * @rl: target request_list
- *
- * Associate @rq with @rl so that accounting and freeing can know the
- * request_list @rq came from.
- */
-static inline void blk_rq_set_rl(struct request *rq, struct request_list *rl)
-{
-	rq->rl = rl;
-}
-
-/**
- * blk_rq_rl - return the request_list a request came from
- * @rq: request of interest
- *
- * Return the request_list @rq is allocated from.
- */
-static inline struct request_list *blk_rq_rl(struct request *rq)
-{
-	return rq->rl;
-}
-
-struct request_list *__blk_queue_next_rl(struct request_list *rl,
-					 struct request_queue *q);
-/**
- * blk_queue_for_each_rl - iterate through all request_lists of a request_queue
- *
- * Should be used under queue_lock.
- */
-#define blk_queue_for_each_rl(rl, q)	\
-	for ((rl) = &(q)->root_rl; (rl); (rl) = __blk_queue_next_rl((rl), (q)))
-
-static inline void blkg_stat_init(struct blkg_stat *stat)
-{
-	u64_stats_init(&stat->syncp);
-}
-
-/**
- * blkg_stat_add - add a value to a blkg_stat
- * @stat: target blkg_stat
- * @val: value to add
- *
- * Add @val to @stat.  The caller is responsible for synchronizing calls to
- * this function.
- */
-static inline void blkg_stat_add(struct blkg_stat *stat, uint64_t val)
-{
-	u64_stats_update_begin(&stat->syncp);
-	stat->cnt += val;
-	u64_stats_update_end(&stat->syncp);
-}
-
-/**
- * blkg_stat_read - read the current value of a blkg_stat
- * @stat: blkg_stat to read
- *
- * Read the current value of @stat.  This function can be called without
- * synchroniztion and takes care of u64 atomicity.
- */
-static inline uint64_t blkg_stat_read(struct blkg_stat *stat)
-{
-	unsigned int start;
-	uint64_t v;
-
-	do {
-		start = u64_stats_fetch_begin_irq(&stat->syncp);
-		v = stat->cnt;
-	} while (u64_stats_fetch_retry_irq(&stat->syncp, start));
-
-	return v;
-}
-
-/**
- * blkg_stat_reset - reset a blkg_stat
- * @stat: blkg_stat to reset
- */
-static inline void blkg_stat_reset(struct blkg_stat *stat)
-{
-	stat->cnt = 0;
-}
-
-/**
- * blkg_stat_merge - merge a blkg_stat into another
- * @to: the destination blkg_stat
- * @from: the source
- *
- * Add @from's count to @to.
- */
-static inline void blkg_stat_merge(struct blkg_stat *to, struct blkg_stat *from)
-{
-	blkg_stat_add(to, blkg_stat_read(from));
-}
-
-static inline void blkg_rwstat_init(struct blkg_rwstat *rwstat)
-{
-	u64_stats_init(&rwstat->syncp);
-}
-
-/**
- * blkg_rwstat_add - add a value to a blkg_rwstat
- * @rwstat: target blkg_rwstat
- * @rw: mask of REQ_{WRITE|SYNC}
- * @val: value to add
- *
- * Add @val to @rwstat.  The counters are chosen according to @rw.  The
- * caller is responsible for synchronizing calls to this function.
- */
-static inline void blkg_rwstat_add(struct blkg_rwstat *rwstat,
-				   int rw, uint64_t val)
-{
-	u64_stats_update_begin(&rwstat->syncp);
-
-	if (rw & REQ_WRITE)
-		rwstat->cnt[BLKG_RWSTAT_WRITE] += val;
-	else
-		rwstat->cnt[BLKG_RWSTAT_READ] += val;
-	if (rw & REQ_SYNC)
-		rwstat->cnt[BLKG_RWSTAT_SYNC] += val;
-	else
-		rwstat->cnt[BLKG_RWSTAT_ASYNC] += val;
-
-	u64_stats_update_end(&rwstat->syncp);
-}
-
-/**
- * blkg_rwstat_read - read the current values of a blkg_rwstat
- * @rwstat: blkg_rwstat to read
- *
- * Read the current snapshot of @rwstat and return it as the return value.
- * This function can be called without synchronization and takes care of
- * u64 atomicity.
- */
-static inline struct blkg_rwstat blkg_rwstat_read(struct blkg_rwstat *rwstat)
-{
-	unsigned int start;
-	struct blkg_rwstat tmp;
-
-	do {
-		start = u64_stats_fetch_begin_irq(&rwstat->syncp);
-		tmp = *rwstat;
-	} while (u64_stats_fetch_retry_irq(&rwstat->syncp, start));
-
-	return tmp;
-}
-
-/**
- * blkg_rwstat_total - read the total count of a blkg_rwstat
- * @rwstat: blkg_rwstat to read
- *
- * Return the total count of @rwstat regardless of the IO direction.  This
- * function can be called without synchronization and takes care of u64
- * atomicity.
- */
-static inline uint64_t blkg_rwstat_total(struct blkg_rwstat *rwstat)
-{
-	struct blkg_rwstat tmp = blkg_rwstat_read(rwstat);
-
-	return tmp.cnt[BLKG_RWSTAT_READ] + tmp.cnt[BLKG_RWSTAT_WRITE];
-}
-
-/**
- * blkg_rwstat_reset - reset a blkg_rwstat
- * @rwstat: blkg_rwstat to reset
- */
-static inline void blkg_rwstat_reset(struct blkg_rwstat *rwstat)
-{
-	memset(rwstat->cnt, 0, sizeof(rwstat->cnt));
-}
-
-/**
- * blkg_rwstat_merge - merge a blkg_rwstat into another
- * @to: the destination blkg_rwstat
- * @from: the source
- *
- * Add @from's counts to @to.
- */
-static inline void blkg_rwstat_merge(struct blkg_rwstat *to,
-				     struct blkg_rwstat *from)
-{
-	struct blkg_rwstat v = blkg_rwstat_read(from);
-	int i;
-
-	u64_stats_update_begin(&to->syncp);
-	for (i = 0; i < BLKG_RWSTAT_NR; i++)
-		to->cnt[i] += v.cnt[i];
-	u64_stats_update_end(&to->syncp);
-}
-
-#else	/* CONFIG_BLK_CGROUP */
-
-struct cgroup;
-struct blkcg;
-
-struct blkg_policy_data {
-};
-
-struct blkcg_gq {
-};
-
-struct blkcg_policy {
-};
-
-static inline struct blkcg_gq *blkg_lookup(struct blkcg *blkcg, void *key) { return NULL; }
-static inline int blkcg_init_queue(struct request_queue *q) { return 0; }
-static inline void blkcg_drain_queue(struct request_queue *q) { }
-static inline void blkcg_exit_queue(struct request_queue *q) { }
-static inline int blkcg_policy_register(struct blkcg_policy *pol) { return 0; }
-static inline void blkcg_policy_unregister(struct blkcg_policy *pol) { }
-static inline int blkcg_activate_policy(struct request_queue *q,
-					const struct blkcg_policy *pol) { return 0; }
-static inline void blkcg_deactivate_policy(struct request_queue *q,
-					   const struct blkcg_policy *pol) { }
-
-static inline struct blkcg *bio_blkcg(struct bio *bio) { return NULL; }
-
-static inline struct blkg_policy_data *blkg_to_pd(struct blkcg_gq *blkg,
-						  struct blkcg_policy *pol) { return NULL; }
-static inline struct blkcg_gq *pd_to_blkg(struct blkg_policy_data *pd) { return NULL; }
-static inline char *blkg_path(struct blkcg_gq *blkg) { return NULL; }
-static inline void blkg_get(struct blkcg_gq *blkg) { }
-static inline void blkg_put(struct blkcg_gq *blkg) { }
-
-static inline struct request_list *blk_get_rl(struct request_queue *q,
-					      struct bio *bio) { return &q->root_rl; }
-static inline void blk_put_rl(struct request_list *rl) { }
-static inline void blk_rq_set_rl(struct request *rq, struct request_list *rl) { }
-static inline struct request_list *blk_rq_rl(struct request *rq) { return &rq->q->root_rl; }
-
-#define blk_queue_for_each_rl(rl, q)	\
-	for ((rl) = &(q)->root_rl; (rl); (rl) = NULL)
-
-#endif	/* CONFIG_BLK_CGROUP */
-#endif	/* _BLK_CGROUP_H */

block/blk-core.c +1 -1

@@ -32,12 +32,12 @@
 #include <linux/delay.h>
 #include <linux/ratelimit.h>
 #include <linux/pm_runtime.h>
+#include <linux/blk-cgroup.h>
 
 #define CREATE_TRACE_POINTS
 #include <trace/events/block.h>
 
 #include "blk.h"
-#include "blk-cgroup.h"
 #include "blk-mq.h"
 
 EXPORT_TRACEPOINT_SYMBOL_GPL(block_bio_remap);

block/blk-sysfs.c +1 -1

@@ -8,9 +8,9 @@
 #include <linux/blkdev.h>
 #include <linux/blktrace_api.h>
 #include <linux/blk-mq.h>
+#include <linux/blk-cgroup.h>
 
 #include "blk.h"
-#include "blk-cgroup.h"
 #include "blk-mq.h"
 
 struct queue_sysfs_entry {

block/blk-throttle.c +1 -1

@@ -9,7 +9,7 @@
 #include <linux/blkdev.h>
 #include <linux/bio.h>
 #include <linux/blktrace_api.h>
-#include "blk-cgroup.h"
+#include <linux/blk-cgroup.h>
 #include "blk.h"
 
 /* Max dispatch from a group in 1 round */

block/cfq-iosched.c +1 -1

@@ -14,8 +14,8 @@
 #include <linux/rbtree.h>
 #include <linux/ioprio.h>
 #include <linux/blktrace_api.h>
+#include <linux/blk-cgroup.h>
 #include "blk.h"
-#include "blk-cgroup.h"
 
 /*
  * tunables

block/elevator.c +1 -1

@@ -35,11 +35,11 @@
 #include <linux/hash.h>
 #include <linux/uaccess.h>
 #include <linux/pm_runtime.h>
+#include <linux/blk-cgroup.h>
 
 #include <trace/events/block.h>
 
 #include "blk.h"
-#include "blk-cgroup.h"
 
 static DEFINE_SPINLOCK(elv_list_lock);
 static LIST_HEAD(elv_list);

include/linux/blk-cgroup.h new file +603 -0

@@ -0,0 +1,603 @@
+#ifndef _BLK_CGROUP_H
+#define _BLK_CGROUP_H
+/*
+ * Common Block IO controller cgroup interface
+ *
+ * Based on ideas and code from CFQ, CFS and BFQ:
+ * Copyright (C) 2003 Jens Axboe <[email protected]>
+ *
+ * Copyright (C) 2008 Fabio Checconi <[email protected]>
+ *		      Paolo Valente <[email protected]>
+ *
+ * Copyright (C) 2009 Vivek Goyal <[email protected]>
+ * 	              Nauman Rafique <[email protected]>
+ */
+
+#include <linux/cgroup.h>
+#include <linux/u64_stats_sync.h>
+#include <linux/seq_file.h>
+#include <linux/radix-tree.h>
+#include <linux/blkdev.h>
+#include <linux/atomic.h>
+
+/* Max limits for throttle policy */
+#define THROTL_IOPS_MAX		UINT_MAX
+
+/* CFQ specific, out here for blkcg->cfq_weight */
+#define CFQ_WEIGHT_MIN		10
+#define CFQ_WEIGHT_MAX		1000
+#define CFQ_WEIGHT_DEFAULT	500
+
+#ifdef CONFIG_BLK_CGROUP
+
+enum blkg_rwstat_type {
+	BLKG_RWSTAT_READ,
+	BLKG_RWSTAT_WRITE,
+	BLKG_RWSTAT_SYNC,
+	BLKG_RWSTAT_ASYNC,
+
+	BLKG_RWSTAT_NR,
+	BLKG_RWSTAT_TOTAL = BLKG_RWSTAT_NR,
+};
+
+struct blkcg_gq;
+
+struct blkcg {
+	struct cgroup_subsys_state	css;
+	spinlock_t			lock;
+
+	struct radix_tree_root		blkg_tree;
+	struct blkcg_gq			*blkg_hint;
+	struct hlist_head		blkg_list;
+
+	/* TODO: per-policy storage in blkcg */
+	unsigned int			cfq_weight;	/* belongs to cfq */
+	unsigned int			cfq_leaf_weight;
+};
+
+struct blkg_stat {
+	struct u64_stats_sync		syncp;
+	uint64_t			cnt;
+};
+
+struct blkg_rwstat {
+	struct u64_stats_sync		syncp;
+	uint64_t			cnt[BLKG_RWSTAT_NR];
+};
+
+/*
+ * A blkcg_gq (blkg) is association between a block cgroup (blkcg) and a
+ * request_queue (q).  This is used by blkcg policies which need to track
+ * information per blkcg - q pair.
+ *
+ * There can be multiple active blkcg policies and each has its private
+ * data on each blkg, the size of which is determined by
+ * blkcg_policy->pd_size.  blkcg core allocates and frees such areas
+ * together with blkg and invokes pd_init/exit_fn() methods.
+ *
+ * Such private data must embed struct blkg_policy_data (pd) at the
+ * beginning and pd_size can't be smaller than pd.
+ */
+struct blkg_policy_data {
+	/* the blkg and policy id this per-policy data belongs to */
+	struct blkcg_gq			*blkg;
+	int				plid;
+
+	/* used during policy activation */
+	struct list_head		alloc_node;
+};
+
+/* association between a blk cgroup and a request queue */
+struct blkcg_gq {
+	/* Pointer to the associated request_queue */
+	struct request_queue		*q;
+	struct list_head		q_node;
+	struct hlist_node		blkcg_node;
+	struct blkcg			*blkcg;
+
+	/* all non-root blkcg_gq's are guaranteed to have access to parent */
+	struct blkcg_gq			*parent;
+
+	/* request allocation list for this blkcg-q pair */
+	struct request_list		rl;
+
+	/* reference count */
+	atomic_t			refcnt;
+
+	/* is this blkg online? protected by both blkcg and q locks */
+	bool				online;
+
+	struct blkg_policy_data		*pd[BLKCG_MAX_POLS];
+
+	struct rcu_head			rcu_head;
+};
+
+typedef void (blkcg_pol_init_pd_fn)(struct blkcg_gq *blkg);
+typedef void (blkcg_pol_online_pd_fn)(struct blkcg_gq *blkg);
+typedef void (blkcg_pol_offline_pd_fn)(struct blkcg_gq *blkg);
+typedef void (blkcg_pol_exit_pd_fn)(struct blkcg_gq *blkg);
+typedef void (blkcg_pol_reset_pd_stats_fn)(struct blkcg_gq *blkg);
+
+struct blkcg_policy {
+	int				plid;
+	/* policy specific private data size */
+	size_t				pd_size;
+	/* cgroup files for the policy */
+	struct cftype			*cftypes;
+
+	/* operations */
+	blkcg_pol_init_pd_fn		*pd_init_fn;
+	blkcg_pol_online_pd_fn		*pd_online_fn;
+	blkcg_pol_offline_pd_fn		*pd_offline_fn;
+	blkcg_pol_exit_pd_fn		*pd_exit_fn;
+	blkcg_pol_reset_pd_stats_fn	*pd_reset_stats_fn;
+};
+
+extern struct blkcg blkcg_root;
+
+struct blkcg_gq *blkg_lookup(struct blkcg *blkcg, struct request_queue *q);
+struct blkcg_gq *blkg_lookup_create(struct blkcg *blkcg,
+				    struct request_queue *q);
+int blkcg_init_queue(struct request_queue *q);
+void blkcg_drain_queue(struct request_queue *q);
+void blkcg_exit_queue(struct request_queue *q);
+
+/* Blkio controller policy registration */
+int blkcg_policy_register(struct blkcg_policy *pol);
+void blkcg_policy_unregister(struct blkcg_policy *pol);
+int blkcg_activate_policy(struct request_queue *q,
+			  const struct blkcg_policy *pol);
+void blkcg_deactivate_policy(struct request_queue *q,
+			     const struct blkcg_policy *pol);
+
+void blkcg_print_blkgs(struct seq_file *sf, struct blkcg *blkcg,
+		       u64 (*prfill)(struct seq_file *,
+				     struct blkg_policy_data *, int),
+		       const struct blkcg_policy *pol, int data,
+		       bool show_total);
+u64 __blkg_prfill_u64(struct seq_file *sf, struct blkg_policy_data *pd, u64 v);
+u64 __blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
+			 const struct blkg_rwstat *rwstat);
+u64 blkg_prfill_stat(struct seq_file *sf, struct blkg_policy_data *pd, int off);
+u64 blkg_prfill_rwstat(struct seq_file *sf, struct blkg_policy_data *pd,
+		       int off);
+
+u64 blkg_stat_recursive_sum(struct blkg_policy_data *pd, int off);
+struct blkg_rwstat blkg_rwstat_recursive_sum(struct blkg_policy_data *pd,
+					     int off);
+
+struct blkg_conf_ctx {
+	struct gendisk			*disk;
+	struct blkcg_gq			*blkg;
+	u64				v;
+};
+
+int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
+		   const char *input, struct blkg_conf_ctx *ctx);
+void blkg_conf_finish(struct blkg_conf_ctx *ctx);
+
+
+static inline struct blkcg *css_to_blkcg(struct cgroup_subsys_state *css)
+{
+	return css ? container_of(css, struct blkcg, css) : NULL;
+}
+
+static inline struct blkcg *task_blkcg(struct task_struct *tsk)
+{
+	return css_to_blkcg(task_css(tsk, blkio_cgrp_id));
+}
+
+static inline struct blkcg *bio_blkcg(struct bio *bio)
+{
+	if (bio && bio->bi_css)
+		return css_to_blkcg(bio->bi_css);
+	return task_blkcg(current);
+}
+
+/**
+ * blkcg_parent - get the parent of a blkcg
+ * @blkcg: blkcg of interest
+ *
+ * Return the parent blkcg of @blkcg.  Can be called anytime.
+ */
+static inline struct blkcg *blkcg_parent(struct blkcg *blkcg)
+{
+	return css_to_blkcg(blkcg->css.parent);
+}
+
+/**
+ * blkg_to_pdata - get policy private data
+ * @blkg: blkg of interest
+ * @pol: policy of interest
+ *
+ * Return pointer to private data associated with the @blkg-@pol pair.
+ */
+static inline struct blkg_policy_data *blkg_to_pd(struct blkcg_gq *blkg,
+						  struct blkcg_policy *pol)
+{
+	return blkg ? blkg->pd[pol->plid] : NULL;
+}
+
+/**
+ * pdata_to_blkg - get blkg associated with policy private data
+ * @pd: policy private data of interest
+ *
+ * @pd is policy private data.  Determine the blkg it's associated with.
+ */
+static inline struct blkcg_gq *pd_to_blkg(struct blkg_policy_data *pd)
+{
+	return pd ? pd->blkg : NULL;
+}
+
+/**
+ * blkg_path - format cgroup path of blkg
+ * @blkg: blkg of interest
+ * @buf: target buffer
+ * @buflen: target buffer length
+ *
+ * Format the path of the cgroup of @blkg into @buf.
+ */
+static inline int blkg_path(struct blkcg_gq *blkg, char *buf, int buflen)
+{
+	char *p;
+
+	p = cgroup_path(blkg->blkcg->css.cgroup, buf, buflen);
+	if (!p) {
+		strncpy(buf, "<unavailable>", buflen);
+		return -ENAMETOOLONG;
+	}
+
+	memmove(buf, p, buf + buflen - p);
+	return 0;
+}
+
+/**
+ * blkg_get - get a blkg reference
+ * @blkg: blkg to get
+ *
+ * The caller should be holding an existing reference.
+ */
+static inline void blkg_get(struct blkcg_gq *blkg)
+{
+	WARN_ON_ONCE(atomic_read(&blkg->refcnt) <= 0);
+	atomic_inc(&blkg->refcnt);
+}
+
+void __blkg_release_rcu(struct rcu_head *rcu);
+
+/**
+ * blkg_put - put a blkg reference
+ * @blkg: blkg to put
+ */
+static inline void blkg_put(struct blkcg_gq *blkg)
+{
+	WARN_ON_ONCE(atomic_read(&blkg->refcnt) <= 0);
+	if (atomic_dec_and_test(&blkg->refcnt))
+		call_rcu(&blkg->rcu_head, __blkg_release_rcu);
+}
+
+struct blkcg_gq *__blkg_lookup(struct blkcg *blkcg, struct request_queue *q,
+			       bool update_hint);
+
+/**
+ * blkg_for_each_descendant_pre - pre-order walk of a blkg's descendants
+ * @d_blkg: loop cursor pointing to the current descendant
+ * @pos_css: used for iteration
+ * @p_blkg: target blkg to walk descendants of
+ *
+ * Walk @c_blkg through the descendants of @p_blkg.  Must be used with RCU
+ * read locked.  If called under either blkcg or queue lock, the iteration
+ * is guaranteed to include all and only online blkgs.  The caller may
+ * update @pos_css by calling css_rightmost_descendant() to skip subtree.
+ * @p_blkg is included in the iteration and the first node to be visited.
+ */
+#define blkg_for_each_descendant_pre(d_blkg, pos_css, p_blkg)		\
+	css_for_each_descendant_pre((pos_css), &(p_blkg)->blkcg->css)	\
+		if (((d_blkg) = __blkg_lookup(css_to_blkcg(pos_css),	\
+					      (p_blkg)->q, false)))
+
+/**
+ * blkg_for_each_descendant_post - post-order walk of a blkg's descendants
+ * @d_blkg: loop cursor pointing to the current descendant
+ * @pos_css: used for iteration
+ * @p_blkg: target blkg to walk descendants of
+ *
+ * Similar to blkg_for_each_descendant_pre() but performs post-order
+ * traversal instead.  Synchronization rules are the same.  @p_blkg is
+ * included in the iteration and the last node to be visited.
+ */
+#define blkg_for_each_descendant_post(d_blkg, pos_css, p_blkg)		\
+	css_for_each_descendant_post((pos_css), &(p_blkg)->blkcg->css)	\
+		if (((d_blkg) = __blkg_lookup(css_to_blkcg(pos_css),	\
+					      (p_blkg)->q, false)))
+
+/**
+ * blk_get_rl - get request_list to use
+ * @q: request_queue of interest
+ * @bio: bio which will be attached to the allocated request (may be %NULL)
+ *
+ * The caller wants to allocate a request from @q to use for @bio.  Find
+ * the request_list to use and obtain a reference on it.  Should be called
+ * under queue_lock.  This function is guaranteed to return non-%NULL
+ * request_list.
+ */
+static inline struct request_list *blk_get_rl(struct request_queue *q,
+					      struct bio *bio)
+{
+	struct blkcg *blkcg;
+	struct blkcg_gq *blkg;
+
+	rcu_read_lock();
+
+	blkcg = bio_blkcg(bio);
+
+	/* bypass blkg lookup and use @q->root_rl directly for root */
+	if (blkcg == &blkcg_root)
+		goto root_rl;
+
+	/*
+	 * Try to use blkg->rl.  blkg lookup may fail under memory pressure
+	 * or if either the blkcg or queue is going away.  Fall back to
+	 * root_rl in such cases.
+	 */
+	blkg = blkg_lookup_create(blkcg, q);
+	if (unlikely(IS_ERR(blkg)))
+		goto root_rl;
+
+	blkg_get(blkg);
+	rcu_read_unlock();
+	return &blkg->rl;
+root_rl:
+	rcu_read_unlock();
+	return &q->root_rl;
+}
+
+/**
+ * blk_put_rl - put request_list
+ * @rl: request_list to put
+ *
+ * Put the reference acquired by blk_get_rl().  Should be called under
+ * queue_lock.
+ */
+static inline void blk_put_rl(struct request_list *rl)
+{
+	/* root_rl may not have blkg set */
+	if (rl->blkg && rl->blkg->blkcg != &blkcg_root)
+		blkg_put(rl->blkg);
+}
+
+/**
+ * blk_rq_set_rl - associate a request with a request_list
+ * @rq: request of interest
+ * @rl: target request_list
+ *
+ * Associate @rq with @rl so that accounting and freeing can know the
+ * request_list @rq came from.
+ */
+static inline void blk_rq_set_rl(struct request *rq, struct request_list *rl)
+{
+	rq->rl = rl;
+}
+
+/**
+ * blk_rq_rl - return the request_list a request came from
+ * @rq: request of interest
+ *
+ * Return the request_list @rq is allocated from.
+ */
+static inline struct request_list *blk_rq_rl(struct request *rq)
+{
+	return rq->rl;
+}
+
+struct request_list *__blk_queue_next_rl(struct request_list *rl,
+					 struct request_queue *q);
+/**
+ * blk_queue_for_each_rl - iterate through all request_lists of a request_queue
+ *
+ * Should be used under queue_lock.
+ */
+#define blk_queue_for_each_rl(rl, q)	\
+	for ((rl) = &(q)->root_rl; (rl); (rl) = __blk_queue_next_rl((rl), (q)))
+
+static inline void blkg_stat_init(struct blkg_stat *stat)
+{
+	u64_stats_init(&stat->syncp);
+}
+
+/**
+ * blkg_stat_add - add a value to a blkg_stat
+ * @stat: target blkg_stat
+ * @val: value to add
+ *
+ * Add @val to @stat.  The caller is responsible for synchronizing calls to
+ * this function.
+ */
+static inline void blkg_stat_add(struct blkg_stat *stat, uint64_t val)
+{
+	u64_stats_update_begin(&stat->syncp);
+	stat->cnt += val;
+	u64_stats_update_end(&stat->syncp);
+}
+
+/**
+ * blkg_stat_read - read the current value of a blkg_stat
+ * @stat: blkg_stat to read
+ *
+ * Read the current value of @stat.  This function can be called without
+ * synchroniztion and takes care of u64 atomicity.
+ */
+static inline uint64_t blkg_stat_read(struct blkg_stat *stat)
+{
+	unsigned int start;
+	uint64_t v;
+
+	do {
+		start = u64_stats_fetch_begin_irq(&stat->syncp);
+		v = stat->cnt;
+	} while (u64_stats_fetch_retry_irq(&stat->syncp, start));
+
+	return v;
+}
+
+/**
+ * blkg_stat_reset - reset a blkg_stat
+ * @stat: blkg_stat to reset
+ */
+static inline void blkg_stat_reset(struct blkg_stat *stat)
+{
+	stat->cnt = 0;
+}
+
+/**
+ * blkg_stat_merge - merge a blkg_stat into another
+ * @to: the destination blkg_stat
+ * @from: the source
+ *
+ * Add @from's count to @to.
+ */
+static inline void blkg_stat_merge(struct blkg_stat *to, struct blkg_stat *from)
+{
+	blkg_stat_add(to, blkg_stat_read(from));
+}
+
+static inline void blkg_rwstat_init(struct blkg_rwstat *rwstat)
+{
+	u64_stats_init(&rwstat->syncp);
+}
+
+/**
+ * blkg_rwstat_add - add a value to a blkg_rwstat
+ * @rwstat: target blkg_rwstat
+ * @rw: mask of REQ_{WRITE|SYNC}
+ * @val: value to add
+ *
+ * Add @val to @rwstat.  The counters are chosen according to @rw.  The
+ * caller is responsible for synchronizing calls to this function.
+ */
+static inline void blkg_rwstat_add(struct blkg_rwstat *rwstat,
+				   int rw, uint64_t val)
+{
+	u64_stats_update_begin(&rwstat->syncp);
+
+	if (rw & REQ_WRITE)
+		rwstat->cnt[BLKG_RWSTAT_WRITE] += val;
+	else
+		rwstat->cnt[BLKG_RWSTAT_READ] += val;
+	if (rw & REQ_SYNC)
+		rwstat->cnt[BLKG_RWSTAT_SYNC] += val;
+	else
+		rwstat->cnt[BLKG_RWSTAT_ASYNC] += val;
+
+	u64_stats_update_end(&rwstat->syncp);
+}
+
+/**
+ * blkg_rwstat_read - read the current values of a blkg_rwstat
+ * @rwstat: blkg_rwstat to read
+ *
+ * Read the current snapshot of @rwstat and return it as the return value.
+ * This function can be called without synchronization and takes care of
+ * u64 atomicity.
+ */
+static inline struct blkg_rwstat blkg_rwstat_read(struct blkg_rwstat *rwstat)
+{
+	unsigned int start;
+	struct blkg_rwstat tmp;
+
+	do {
+		start = u64_stats_fetch_begin_irq(&rwstat->syncp);
+		tmp = *rwstat;
+	} while (u64_stats_fetch_retry_irq(&rwstat->syncp, start));
+
+	return tmp;
+}
+
+/**
+ * blkg_rwstat_total - read the total count of a blkg_rwstat
+ * @rwstat: blkg_rwstat to read
+ *
+ * Return the total count of @rwstat regardless of the IO direction.  This
+ * function can be called without synchronization and takes care of u64
+ * atomicity.
+ */
+static inline uint64_t blkg_rwstat_total(struct blkg_rwstat *rwstat)
+{
+	struct blkg_rwstat tmp = blkg_rwstat_read(rwstat);
+
+	return tmp.cnt[BLKG_RWSTAT_READ] + tmp.cnt[BLKG_RWSTAT_WRITE];
+}
+
+/**
+ * blkg_rwstat_reset - reset a blkg_rwstat
+ * @rwstat: blkg_rwstat to reset
+ */
+static inline void blkg_rwstat_reset(struct blkg_rwstat *rwstat)
+{
+	memset(rwstat->cnt, 0, sizeof(rwstat->cnt));
+}
+
+/**
+ * blkg_rwstat_merge - merge a blkg_rwstat into another
+ * @to: the destination blkg_rwstat
+ * @from: the source
+ *
+ * Add @from's counts to @to.
+ */
+static inline void blkg_rwstat_merge(struct blkg_rwstat *to,
+				     struct blkg_rwstat *from)
+{
+	struct blkg_rwstat v = blkg_rwstat_read(from);
+	int i;
+
+	u64_stats_update_begin(&to->syncp);
+	for (i = 0; i < BLKG_RWSTAT_NR; i++)
+		to->cnt[i] += v.cnt[i];
+	u64_stats_update_end(&to->syncp);
+}
+
+#else	/* CONFIG_BLK_CGROUP */
+
+struct cgroup;
+struct blkcg;
+
+struct blkg_policy_data {
+};
+
+struct blkcg_gq {
+};
+
+struct blkcg_policy {
+};
+
+static inline struct blkcg_gq *blkg_lookup(struct blkcg *blkcg, void *key) { return NULL; }
+static inline int blkcg_init_queue(struct request_queue *q) { return 0; }
+static inline void blkcg_drain_queue(struct request_queue *q) { }
+static inline void blkcg_exit_queue(struct request_queue *q) { }
+static inline int blkcg_policy_register(struct blkcg_policy *pol) { return 0; }
+static inline void blkcg_policy_unregister(struct blkcg_policy *pol) { }
+static inline int blkcg_activate_policy(struct request_queue *q,
+					const struct blkcg_policy *pol) { return 0; }
+static inline void blkcg_deactivate_policy(struct request_queue *q,
+					   const struct blkcg_policy *pol) { }
+
+static inline struct blkcg *bio_blkcg(struct bio *bio) { return NULL; }
+
+static inline struct blkg_policy_data *blkg_to_pd(struct blkcg_gq *blkg,
+						  struct blkcg_policy *pol) { return NULL; }
+static inline struct blkcg_gq *pd_to_blkg(struct blkg_policy_data *pd) { return NULL; }
+static inline char *blkg_path(struct blkcg_gq *blkg) { return NULL; }
+static inline void blkg_get(struct blkcg_gq *blkg) { }
+static inline void blkg_put(struct blkcg_gq *blkg) { }
+
+static inline struct request_list *blk_get_rl(struct request_queue *q,
+					      struct bio *bio) { return &q->root_rl; }
+static inline void blk_put_rl(struct request_list *rl) { }
+static inline void blk_rq_set_rl(struct request *rq, struct request_list *rl) { }
+static inline struct request_list *blk_rq_rl(struct request *rq) { return &rq->q->root_rl; }
+
+#define blk_queue_for_each_rl(rl, q)	\
+	for ((rl) = &(q)->root_rl; (rl); (rl) = NULL)
+
+#endif	/* CONFIG_BLK_CGROUP */
+#endif	/* _BLK_CGROUP_H */