Merge branch 'for-3.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup updates from Tejun Heo:
 "A lot of activities on the cgroup front.  Most changes aren't visible
  to userland at all at this point and are laying foundation for the
  planned unified hierarchy.

   - The biggest change is decoupling the lifetime management of css
     (cgroup_subsys_state) from that of cgroup's.  Because controllers
     (cpu, memory, block and so on) will need to be dynamically enabled
     and disabled, css which is the association point between a cgroup
     and a controller may come and go dynamically across the lifetime of
     a cgroup.  Till now, css's were created when the associated cgroup
     was created and stayed till the cgroup got destroyed.

     Assumptions around this tight coupling permeated through cgroup
     core and controllers.  These assumptions are gradually removed,
     which consists bulk of patches, and css destruction path is
     completely decoupled from cgroup destruction path.  Note that
     decoupling of creation path is relatively easy on top of these
     changes and the patchset is pending for the next window.

   - cgroup has its own event mechanism cgroup.event_control, which is
     only used by memcg.  It is overly complex trying to achieve high
     flexibility whose benefits seem dubious at best.  Going forward,
     new events will simply generate file modified event and the
     existing mechanism is being made specific to memcg.  This pull
     request contains prepatory patches for such change.

   - Various fixes and cleanups"

Fixed up conflict in kernel/cgroup.c as per Tejun.

* 'for-3.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (69 commits)
  cgroup: fix cgroup_css() invocation in css_from_id()
  cgroup: make cgroup_write_event_control() use css_from_dir() instead of __d_cgrp()
  cgroup: make cgroup_event hold onto cgroup_subsys_state instead of cgroup
  cgroup: implement CFTYPE_NO_PREFIX
  cgroup: make cgroup_css() take cgroup_subsys * instead and allow NULL subsys
  cgroup: rename cgroup_css_from_dir() to css_from_dir() and update its syntax
  cgroup: fix cgroup_write_event_control()
  cgroup: fix subsystem file accesses on the root cgroup
  cgroup: change cgroup_from_id() to css_from_id()
  cgroup: use css_get() in cgroup_create() to check CSS_ROOT
  cpuset: remove an unncessary forward declaration
  cgroup: RCU protect each cgroup_subsys_state release
  cgroup: move subsys file removal to kill_css()
  cgroup: factor out kill_css()
  cgroup: decouple cgroup_subsys_state destruction from cgroup destruction
  cgroup: replace cgroup->css_kill_cnt with ->nr_css
  cgroup: bounce cgroup_subsys_state ref kill confirmation to a work item
  cgroup: move cgroup->subsys[] assignment to online_css()
  cgroup: reorganize css init / exit paths
  cgroup: add __rcu modifier to cgroup->subsys[]
  ...

5 files changed, 174 insertions, 149 deletions

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index e9ac882868c0..3561d305b1e0 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -66,22 +66,25 @@ enum cgroup_subsys_id {
 
 /* Per-subsystem/per-cgroup state maintained by the system. */
 struct cgroup_subsys_state {
-	/*
-	 * The cgroup that this subsystem is attached to. Useful
-	 * for subsystems that want to know about the cgroup
-	 * hierarchy structure
-	 */
+	/* the cgroup that this css is attached to */
 	struct cgroup *cgroup;
 
+	/* the cgroup subsystem that this css is attached to */
+	struct cgroup_subsys *ss;
+
 	/* reference count - access via css_[try]get() and css_put() */
 	struct percpu_ref refcnt;
 
+	/* the parent css */
+	struct cgroup_subsys_state *parent;
+
 	unsigned long flags;
 	/* ID for this css, if possible */
 	struct css_id __rcu *id;
 
-	/* Used to put @cgroup->dentry on the last css_put() */
-	struct work_struct dput_work;
+	/* percpu_ref killing and RCU release */
+	struct rcu_head rcu_head;
+	struct work_struct destroy_work;
 };
 
 /* bits in struct cgroup_subsys_state flags field */
@@ -161,7 +164,16 @@ struct cgroup_name {
 struct cgroup {
 	unsigned long flags;		/* "unsigned long" so bitops work */
 
-	int id;				/* ida allocated in-hierarchy ID */
+	/*
+	 * idr allocated in-hierarchy ID.
+	 *
+	 * The ID of the root cgroup is always 0, and a new cgroup
+	 * will be assigned with a smallest available ID.
+	 */
+	int id;
+
+	/* the number of attached css's */
+	int nr_css;
 
 	/*
 	 * We link our 'sibling' struct into our parent's 'children'.
@@ -196,7 +208,7 @@ struct cgroup {
 	struct cgroup_name __rcu *name;
 
 	/* Private pointers for each registered subsystem */
-	struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
+	struct cgroup_subsys_state __rcu *subsys[CGROUP_SUBSYS_COUNT];
 
 	struct cgroupfs_root *root;
 
@@ -220,10 +232,12 @@ struct cgroup {
 	struct list_head pidlists;
 	struct mutex pidlist_mutex;
 
+	/* dummy css with NULL ->ss, points back to this cgroup */
+	struct cgroup_subsys_state dummy_css;
+
 	/* For css percpu_ref killing and RCU-protected deletion */
 	struct rcu_head rcu_head;
 	struct work_struct destroy_work;
-	atomic_t css_kill_cnt;
 
 	/* List of events which userspace want to receive */
 	struct list_head event_list;
@@ -322,7 +336,7 @@ struct cgroupfs_root {
 	unsigned long flags;
 
 	/* IDs for cgroups in this hierarchy */
-	struct ida cgroup_ida;
+	struct idr cgroup_idr;
 
 	/* The path to use for release notifications. */
 	char release_agent_path[PATH_MAX];
@@ -394,9 +408,10 @@ struct cgroup_map_cb {
 
 /* cftype->flags */
 enum {
-	CFTYPE_ONLY_ON_ROOT	= (1 << 0),	/* only create on root cg */
-	CFTYPE_NOT_ON_ROOT	= (1 << 1),	/* don't create on root cg */
+	CFTYPE_ONLY_ON_ROOT	= (1 << 0),	/* only create on root cgrp */
+	CFTYPE_NOT_ON_ROOT	= (1 << 1),	/* don't create on root cgrp */
 	CFTYPE_INSANE		= (1 << 2),	/* don't create if sane_behavior */
+	CFTYPE_NO_PREFIX	= (1 << 3),	/* (DON'T USE FOR NEW FILES) no subsys prefix */
 };
 
 #define MAX_CFTYPE_NAME		64
@@ -424,35 +439,41 @@ struct cftype {
 	/* CFTYPE_* flags */
 	unsigned int flags;
 
+	/*
+	 * The subsys this file belongs to.  Initialized automatically
+	 * during registration.  NULL for cgroup core files.
+	 */
+	struct cgroup_subsys *ss;
+
 	int (*open)(struct inode *inode, struct file *file);
-	ssize_t (*read)(struct cgroup *cgrp, struct cftype *cft,
+	ssize_t (*read)(struct cgroup_subsys_state *css, struct cftype *cft,
 			struct file *file,
 			char __user *buf, size_t nbytes, loff_t *ppos);
 	/*
 	 * read_u64() is a shortcut for the common case of returning a
 	 * single integer. Use it in place of read()
 	 */
-	u64 (*read_u64)(struct cgroup *cgrp, struct cftype *cft);
+	u64 (*read_u64)(struct cgroup_subsys_state *css, struct cftype *cft);
 	/*
 	 * read_s64() is a signed version of read_u64()
 	 */
-	s64 (*read_s64)(struct cgroup *cgrp, struct cftype *cft);
+	s64 (*read_s64)(struct cgroup_subsys_state *css, struct cftype *cft);
 	/*
 	 * read_map() is used for defining a map of key/value
 	 * pairs. It should call cb->fill(cb, key, value) for each
 	 * entry. The key/value pairs (and their ordering) should not
 	 * change between reboots.
 	 */
-	int (*read_map)(struct cgroup *cgrp, struct cftype *cft,
+	int (*read_map)(struct cgroup_subsys_state *css, struct cftype *cft,
 			struct cgroup_map_cb *cb);
 	/*
 	 * read_seq_string() is used for outputting a simple sequence
 	 * using seqfile.
 	 */
-	int (*read_seq_string)(struct cgroup *cgrp, struct cftype *cft,
-			       struct seq_file *m);
+	int (*read_seq_string)(struct cgroup_subsys_state *css,
+			       struct cftype *cft, struct seq_file *m);
 
-	ssize_t (*write)(struct cgroup *cgrp, struct cftype *cft,
+	ssize_t (*write)(struct cgroup_subsys_state *css, struct cftype *cft,
 			 struct file *file,
 			 const char __user *buf, size_t nbytes, loff_t *ppos);
 
@@ -461,18 +482,20 @@ struct cftype {
 	 * a single integer (as parsed by simple_strtoull) from
 	 * userspace. Use in place of write(); return 0 or error.
 	 */
-	int (*write_u64)(struct cgroup *cgrp, struct cftype *cft, u64 val);
+	int (*write_u64)(struct cgroup_subsys_state *css, struct cftype *cft,
+			 u64 val);
 	/*
 	 * write_s64() is a signed version of write_u64()
 	 */
-	int (*write_s64)(struct cgroup *cgrp, struct cftype *cft, s64 val);
+	int (*write_s64)(struct cgroup_subsys_state *css, struct cftype *cft,
+			 s64 val);
 
 	/*
 	 * write_string() is passed a nul-terminated kernelspace
 	 * buffer of maximum length determined by max_write_len.
 	 * Returns 0 or -ve error code.
 	 */
-	int (*write_string)(struct cgroup *cgrp, struct cftype *cft,
+	int (*write_string)(struct cgroup_subsys_state *css, struct cftype *cft,
 			    const char *buffer);
 	/*
 	 * trigger() callback can be used to get some kick from the
@@ -480,7 +503,7 @@ struct cftype {
 	 * at all. The private field can be used to determine the
 	 * kick type for multiplexing.
 	 */
-	int (*trigger)(struct cgroup *cgrp, unsigned int event);
+	int (*trigger)(struct cgroup_subsys_state *css, unsigned int event);
 
 	int (*release)(struct inode *inode, struct file *file);
 
@@ -490,16 +513,18 @@ struct cftype {
 	 * you want to provide this functionality. Use eventfd_signal()
 	 * on eventfd to send notification to userspace.
 	 */
-	int (*register_event)(struct cgroup *cgrp, struct cftype *cft,
-			struct eventfd_ctx *eventfd, const char *args);
+	int (*register_event)(struct cgroup_subsys_state *css,
+			      struct cftype *cft, struct eventfd_ctx *eventfd,
+			      const char *args);
 	/*
 	 * unregister_event() callback will be called when userspace
 	 * closes the eventfd or on cgroup removing.
 	 * This callback must be implemented, if you want provide
 	 * notification functionality.
 	 */
-	void (*unregister_event)(struct cgroup *cgrp, struct cftype *cft,
-			struct eventfd_ctx *eventfd);
+	void (*unregister_event)(struct cgroup_subsys_state *css,
+				 struct cftype *cft,
+				 struct eventfd_ctx *eventfd);
 };
 
 /*
@@ -512,15 +537,6 @@ struct cftype_set {
 	struct cftype			*cfts;
 };
 
-struct cgroup_scanner {
-	struct cgroup *cg;
-	int (*test_task)(struct task_struct *p, struct cgroup_scanner *scan);
-	void (*process_task)(struct task_struct *p,
-			struct cgroup_scanner *scan);
-	struct ptr_heap *heap;
-	void *data;
-};
-
 /*
  * See the comment above CGRP_ROOT_SANE_BEHAVIOR for details.  This
  * function can be called as long as @cgrp is accessible.
@@ -537,7 +553,7 @@ static inline const char *cgroup_name(const struct cgroup *cgrp)
 }
 
 int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
-int cgroup_rm_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
+int cgroup_rm_cftypes(struct cftype *cfts);
 
 bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor);
 
@@ -553,20 +569,22 @@ int cgroup_task_count(const struct cgroup *cgrp);
 struct cgroup_taskset;
 struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset);
 struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset);
-struct cgroup *cgroup_taskset_cur_cgroup(struct cgroup_taskset *tset);
+struct cgroup_subsys_state *cgroup_taskset_cur_css(struct cgroup_taskset *tset,
+						   int subsys_id);
 int cgroup_taskset_size(struct cgroup_taskset *tset);
 
 /**
  * cgroup_taskset_for_each - iterate cgroup_taskset
  * @task: the loop cursor
- * @skip_cgrp: skip if task's cgroup matches this, %NULL to iterate through all
+ * @skip_css: skip if task's css matches this, %NULL to iterate through all
  * @tset: taskset to iterate
  */
-#define cgroup_taskset_for_each(task, skip_cgrp, tset)			\
+#define cgroup_taskset_for_each(task, skip_css, tset)			\
 	for ((task) = cgroup_taskset_first((tset)); (task);		\
 	     (task) = cgroup_taskset_next((tset)))			\
-		if (!(skip_cgrp) ||					\
-		    cgroup_taskset_cur_cgroup((tset)) != (skip_cgrp))
+		if (!(skip_css) ||					\
+		    cgroup_taskset_cur_css((tset),			\
+			(skip_css)->ss->subsys_id) != (skip_css))
 
 /*
  * Control Group subsystem type.
@@ -574,18 +592,22 @@ int cgroup_taskset_size(struct cgroup_taskset *tset);
  */
 
 struct cgroup_subsys {
-	struct cgroup_subsys_state *(*css_alloc)(struct cgroup *cgrp);
-	int (*css_online)(struct cgroup *cgrp);
-	void (*css_offline)(struct cgroup *cgrp);
-	void (*css_free)(struct cgroup *cgrp);
-
-	int (*can_attach)(struct cgroup *cgrp, struct cgroup_taskset *tset);
-	void (*cancel_attach)(struct cgroup *cgrp, struct cgroup_taskset *tset);
-	void (*attach)(struct cgroup *cgrp, struct cgroup_taskset *tset);
+	struct cgroup_subsys_state *(*css_alloc)(struct cgroup_subsys_state *parent_css);
+	int (*css_online)(struct cgroup_subsys_state *css);
+	void (*css_offline)(struct cgroup_subsys_state *css);
+	void (*css_free)(struct cgroup_subsys_state *css);
+
+	int (*can_attach)(struct cgroup_subsys_state *css,
+			  struct cgroup_taskset *tset);
+	void (*cancel_attach)(struct cgroup_subsys_state *css,
+			      struct cgroup_taskset *tset);
+	void (*attach)(struct cgroup_subsys_state *css,
+		       struct cgroup_taskset *tset);
 	void (*fork)(struct task_struct *task);
-	void (*exit)(struct cgroup *cgrp, struct cgroup *old_cgrp,
+	void (*exit)(struct cgroup_subsys_state *css,
+		     struct cgroup_subsys_state *old_css,
 		     struct task_struct *task);
-	void (*bind)(struct cgroup *root);
+	void (*bind)(struct cgroup_subsys_state *root_css);
 
 	int subsys_id;
 	int disabled;
@@ -641,10 +663,17 @@ struct cgroup_subsys {
 #undef IS_SUBSYS_ENABLED
 #undef SUBSYS
 
-static inline struct cgroup_subsys_state *cgroup_subsys_state(
-	struct cgroup *cgrp, int subsys_id)
+/**
+ * css_parent - find the parent css
+ * @css: the target cgroup_subsys_state
+ *
+ * Return the parent css of @css.  This function is guaranteed to return
+ * non-NULL parent as long as @css isn't the root.
+ */
+static inline
+struct cgroup_subsys_state *css_parent(struct cgroup_subsys_state *css)
 {
-	return cgrp->subsys[subsys_id];
+	return css->parent;
 }
 
 /**
@@ -672,7 +701,7 @@ extern struct mutex cgroup_mutex;
 #endif
 
 /**
- * task_subsys_state_check - obtain css for (task, subsys) w/ extra access conds
+ * task_css_check - obtain css for (task, subsys) w/ extra access conds
  * @task: the target task
  * @subsys_id: the target subsystem ID
  * @__c: extra condition expression to be passed to rcu_dereference_check()
@@ -680,7 +709,7 @@ extern struct mutex cgroup_mutex;
  * Return the cgroup_subsys_state for the (@task, @subsys_id) pair.  The
  * synchronization rules are the same as task_css_set_check().
  */
-#define task_subsys_state_check(task, subsys_id, __c)			\
+#define task_css_check(task, subsys_id, __c)				\
 	task_css_set_check((task), (__c))->subsys[(subsys_id)]
 
 /**
@@ -695,87 +724,92 @@ static inline struct css_set *task_css_set(struct task_struct *task)
 }
 
 /**
- * task_subsys_state - obtain css for (task, subsys)
+ * task_css - obtain css for (task, subsys)
  * @task: the target task
  * @subsys_id: the target subsystem ID
  *
- * See task_subsys_state_check().
+ * See task_css_check().
  */
-static inline struct cgroup_subsys_state *
-task_subsys_state(struct task_struct *task, int subsys_id)
+static inline struct cgroup_subsys_state *task_css(struct task_struct *task,
+						   int subsys_id)
 {
-	return task_subsys_state_check(task, subsys_id, false);
+	return task_css_check(task, subsys_id, false);
 }
 
-static inline struct cgroup* task_cgroup(struct task_struct *task,
-					       int subsys_id)
+static inline struct cgroup *task_cgroup(struct task_struct *task,
+					 int subsys_id)
 {
-	return task_subsys_state(task, subsys_id)->cgroup;
+	return task_css(task, subsys_id)->cgroup;
 }
 
-struct cgroup *cgroup_next_sibling(struct cgroup *pos);
+struct cgroup_subsys_state *css_next_child(struct cgroup_subsys_state *pos,
+					   struct cgroup_subsys_state *parent);
+
+struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss);
 
 /**
- * cgroup_for_each_child - iterate through children of a cgroup
- * @pos: the cgroup * to use as the loop cursor
- * @cgrp: cgroup whose children to walk
+ * css_for_each_child - iterate through children of a css
+ * @pos: the css * to use as the loop cursor
+ * @parent: css whose children to walk
  *
- * Walk @cgrp's children.  Must be called under rcu_read_lock().  A child
- * cgroup which hasn't finished ->css_online() or already has finished
+ * Walk @parent's children.  Must be called under rcu_read_lock().  A child
+ * css which hasn't finished ->css_online() or already has finished
  * ->css_offline() may show up during traversal and it's each subsystem's
  * responsibility to verify that each @pos is alive.
  *
  * If a subsystem synchronizes against the parent in its ->css_online() and
- * before starting iterating, a cgroup which finished ->css_online() is
+ * before starting iterating, a css which finished ->css_online() is
  * guaranteed to be visible in the future iterations.
  *
  * It is allowed to temporarily drop RCU read lock during iteration.  The
  * caller is responsible for ensuring that @pos remains accessible until
  * the start of the next iteration by, for example, bumping the css refcnt.
  */
-#define cgroup_for_each_child(pos, cgrp)				\
-	for ((pos) = list_first_or_null_rcu(&(cgrp)->children,		\
-					    struct cgroup, sibling);	\
-	     (pos); (pos) = cgroup_next_sibling((pos)))
+#define css_for_each_child(pos, parent)					\
+	for ((pos) = css_next_child(NULL, (parent)); (pos);		\
+	     (pos) = css_next_child((pos), (parent)))
+
+struct cgroup_subsys_state *
+css_next_descendant_pre(struct cgroup_subsys_state *pos,
+			struct cgroup_subsys_state *css);
 
-struct cgroup *cgroup_next_descendant_pre(struct cgroup *pos,
-					  struct cgroup *cgroup);
-struct cgroup *cgroup_rightmost_descendant(struct cgroup *pos);
+struct cgroup_subsys_state *
+css_rightmost_descendant(struct cgroup_subsys_state *pos);
 
 /**
- * cgroup_for_each_descendant_pre - pre-order walk of a cgroup's descendants
- * @pos: the cgroup * to use as the loop cursor
- * @cgroup: cgroup whose descendants to walk
+ * css_for_each_descendant_pre - pre-order walk of a css's descendants
+ * @pos: the css * to use as the loop cursor
+ * @root: css whose descendants to walk
  *
- * Walk @cgroup's descendants.  Must be called under rcu_read_lock().  A
- * descendant cgroup which hasn't finished ->css_online() or already has
+ * Walk @root's descendants.  @root is included in the iteration and the
+ * first node to be visited.  Must be called under rcu_read_lock().  A
+ * descendant css which hasn't finished ->css_online() or already has
  * finished ->css_offline() may show up during traversal and it's each
  * subsystem's responsibility to verify that each @pos is alive.
  *
  * If a subsystem synchronizes against the parent in its ->css_online() and
  * before starting iterating, and synchronizes against @pos on each
- * iteration, any descendant cgroup which finished ->css_online() is
+ * iteration, any descendant css which finished ->css_online() is
  * guaranteed to be visible in the future iterations.
  *
  * In other words, the following guarantees that a descendant can't escape
  * state updates of its ancestors.
  *
- * my_online(@cgrp)
+ * my_online(@css)
  * {
- *	Lock @cgrp->parent and @cgrp;
- *	Inherit state from @cgrp->parent;
+ *	Lock @css's parent and @css;
+ *	Inherit state from the parent;
  *	Unlock both.
  * }
  *
- * my_update_state(@cgrp)
+ * my_update_state(@css)
  * {
- *	Lock @cgrp;
- *	Update @cgrp's state;
- *	Unlock @cgrp;
- *
- *	cgroup_for_each_descendant_pre(@pos, @cgrp) {
+ *	css_for_each_descendant_pre(@pos, @css) {
  *		Lock @pos;
- *		Verify @pos is alive and inherit state from @pos->parent;
+ *		if (@pos == @css)
+ *			Update @css's state;
+ *		else
+ *			Verify @pos is alive and inherit state from its parent;
  *		Unlock @pos;
  *	}
  * }
@@ -786,8 +820,7 @@ struct cgroup *cgroup_rightmost_descendant(struct cgroup *pos);
  * visible by walking order and, as long as inheriting operations to the
  * same @pos are atomic to each other, multiple updates racing each other
  * still result in the correct state.  It's guaranateed that at least one
- * inheritance happens for any cgroup after the latest update to its
- * parent.
+ * inheritance happens for any css after the latest update to its parent.
  *
  * If checking parent's state requires locking the parent, each inheriting
  * iteration should lock and unlock both @pos->parent and @pos.
@@ -800,52 +833,45 @@ struct cgroup *cgroup_rightmost_descendant(struct cgroup *pos);
  * caller is responsible for ensuring that @pos remains accessible until
  * the start of the next iteration by, for example, bumping the css refcnt.
  */
-#define cgroup_for_each_descendant_pre(pos, cgroup)			\
-	for (pos = cgroup_next_descendant_pre(NULL, (cgroup)); (pos);	\
-	     pos = cgroup_next_descendant_pre((pos), (cgroup)))
+#define css_for_each_descendant_pre(pos, css)				\
+	for ((pos) = css_next_descendant_pre(NULL, (css)); (pos);	\
+	     (pos) = css_next_descendant_pre((pos), (css)))
 
-struct cgroup *cgroup_next_descendant_post(struct cgroup *pos,
-					   struct cgroup *cgroup);
+struct cgroup_subsys_state *
+css_next_descendant_post(struct cgroup_subsys_state *pos,
+			 struct cgroup_subsys_state *css);
 
 /**
- * cgroup_for_each_descendant_post - post-order walk of a cgroup's descendants
- * @pos: the cgroup * to use as the loop cursor
- * @cgroup: cgroup whose descendants to walk
+ * css_for_each_descendant_post - post-order walk of a css's descendants
+ * @pos: the css * to use as the loop cursor
+ * @css: css whose descendants to walk
  *
- * Similar to cgroup_for_each_descendant_pre() but performs post-order
- * traversal instead.  Note that the walk visibility guarantee described in
- * pre-order walk doesn't apply the same to post-order walks.
+ * Similar to css_for_each_descendant_pre() but performs post-order
+ * traversal instead.  @root is included in the iteration and the last
+ * node to be visited.  Note that the walk visibility guarantee described
+ * in pre-order walk doesn't apply the same to post-order walks.
  */
-#define cgroup_for_each_descendant_post(pos, cgroup)			\
-	for (pos = cgroup_next_descendant_post(NULL, (cgroup)); (pos);	\
-	     pos = cgroup_next_descendant_post((pos), (cgroup)))
-
-/* A cgroup_iter should be treated as an opaque object */
-struct cgroup_iter {
-	struct list_head *cset_link;
-	struct list_head *task;
+#define css_for_each_descendant_post(pos, css)				\
+	for ((pos) = css_next_descendant_post(NULL, (css)); (pos);	\
+	     (pos) = css_next_descendant_post((pos), (css)))
+
+/* A css_task_iter should be treated as an opaque object */
+struct css_task_iter {
+	struct cgroup_subsys_state	*origin_css;
+	struct list_head		*cset_link;
+	struct list_head		*task;
 };
 
-/*
- * To iterate across the tasks in a cgroup:
- *
- * 1) call cgroup_iter_start to initialize an iterator
- *
- * 2) call cgroup_iter_next() to retrieve member tasks until it
- *    returns NULL or until you want to end the iteration
- *
- * 3) call cgroup_iter_end() to destroy the iterator.
- *
- * Or, call cgroup_scan_tasks() to iterate through every task in a
- * cgroup - cgroup_scan_tasks() holds the css_set_lock when calling
- * the test_task() callback, but not while calling the process_task()
- * callback.
- */
-void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it);
-struct task_struct *cgroup_iter_next(struct cgroup *cgrp,
-					struct cgroup_iter *it);
-void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it);
-int cgroup_scan_tasks(struct cgroup_scanner *scan);
+void css_task_iter_start(struct cgroup_subsys_state *css,
+			 struct css_task_iter *it);
+struct task_struct *css_task_iter_next(struct css_task_iter *it);
+void css_task_iter_end(struct css_task_iter *it);
+
+int css_scan_tasks(struct cgroup_subsys_state *css,
+		   bool (*test)(struct task_struct *, void *),
+		   void (*process)(struct task_struct *, void *),
+		   void *data, struct ptr_heap *heap);
+
 int cgroup_attach_task_all(struct task_struct *from, struct task_struct *);
 int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from);
 
@@ -878,7 +904,8 @@ bool css_is_ancestor(struct cgroup_subsys_state *cg,
 
 /* Get id and depth of css */
 unsigned short css_id(struct cgroup_subsys_state *css);
-struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id);
+struct cgroup_subsys_state *css_from_dir(struct dentry *dentry,
+					 struct cgroup_subsys *ss);
 
 #else /* !CONFIG_CGROUPS */
 
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 7b4d9d79570b..6c416092e324 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -85,7 +85,7 @@ extern struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p);
 extern struct mem_cgroup *try_get_mem_cgroup_from_mm(struct mm_struct *mm);
 
 extern struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *memcg);
-extern struct mem_cgroup *mem_cgroup_from_cont(struct cgroup *cont);
+extern struct mem_cgroup *mem_cgroup_from_css(struct cgroup_subsys_state *css);
 
 static inline
 bool mm_match_cgroup(const struct mm_struct *mm, const struct mem_cgroup *memcg)
diff --git a/include/linux/vmpressure.h b/include/linux/vmpressure.h
index 7dc17e2456de..3f3788d49362 100644
--- a/include/linux/vmpressure.h
+++ b/include/linux/vmpressure.h
@@ -34,10 +34,12 @@ extern void vmpressure_cleanup(struct vmpressure *vmpr);
 extern struct vmpressure *memcg_to_vmpressure(struct mem_cgroup *memcg);
 extern struct cgroup_subsys_state *vmpressure_to_css(struct vmpressure *vmpr);
 extern struct vmpressure *css_to_vmpressure(struct cgroup_subsys_state *css);
-extern int vmpressure_register_event(struct cgroup *cg, struct cftype *cft,
+extern int vmpressure_register_event(struct cgroup_subsys_state *css,
+				     struct cftype *cft,
 				     struct eventfd_ctx *eventfd,
 				     const char *args);
-extern void vmpressure_unregister_event(struct cgroup *cg, struct cftype *cft,
+extern void vmpressure_unregister_event(struct cgroup_subsys_state *css,
+					struct cftype *cft,
 					struct eventfd_ctx *eventfd);
 #else
 static inline void vmpressure(gfp_t gfp, struct mem_cgroup *memcg,
diff --git a/include/net/cls_cgroup.h b/include/net/cls_cgroup.h
index 0fee0617fb7d..52adaa75dac9 100644
--- a/include/net/cls_cgroup.h
+++ b/include/net/cls_cgroup.h
@@ -35,7 +35,7 @@ static inline u32 task_cls_classid(struct task_struct *p)
 		return 0;
 
 	rcu_read_lock();
-	classid = container_of(task_subsys_state(p, net_cls_subsys_id),
+	classid = container_of(task_css(p, net_cls_subsys_id),
 			       struct cgroup_cls_state, css)->classid;
 	rcu_read_unlock();
 
@@ -51,7 +51,7 @@ static inline u32 task_cls_classid(struct task_struct *p)
 		return 0;
 
 	rcu_read_lock();
-	css = task_subsys_state(p, net_cls_subsys_id);
+	css = task_css(p, net_cls_subsys_id);
 	if (css)
 		classid = container_of(css,
 				       struct cgroup_cls_state, css)->classid;
diff --git a/include/net/netprio_cgroup.h b/include/net/netprio_cgroup.h
index 50ab8c26ab59..a24f8bb3ca47 100644
--- a/include/net/netprio_cgroup.h
+++ b/include/net/netprio_cgroup.h
@@ -25,10 +25,6 @@ struct netprio_map {
 	u32 priomap[];
 };
 
-struct cgroup_netprio_state {
-	struct cgroup_subsys_state css;
-};
-
 extern void sock_update_netprioidx(struct sock *sk);
 
 #if IS_BUILTIN(CONFIG_NETPRIO_CGROUP)
@@ -39,7 +35,7 @@ static inline u32 task_netprioidx(struct task_struct *p)
 	u32 idx;
 
 	rcu_read_lock();
-	css = task_subsys_state(p, net_prio_subsys_id);
+	css = task_css(p, net_prio_subsys_id);
 	idx = css->cgroup->id;
 	rcu_read_unlock();
 	return idx;
@@ -53,7 +49,7 @@ static inline u32 task_netprioidx(struct task_struct *p)
 	u32 idx = 0;
 
 	rcu_read_lock();
-	css = task_subsys_state(p, net_prio_subsys_id);
+	css = task_css(p, net_prio_subsys_id);
 	if (css)
 		idx = css->cgroup->id;
 	rcu_read_unlock();