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Subject[PATCH cgroup/for-4.2 2/2] cgroup: reorganize include/linux/cgroup.h
From e8e33da1469e11ef1a62c0e0d68fe50a4b3694a6 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Wed, 13 May 2015 15:37:01 -0400

Over time, cgroup.h grew organically and doesn't have much logical
structure at this point. Separation of cgroup-defs.h in the previous
patch gives us a good chance for reorganizing cgroup.h as changes to
the header are likely to cause conflicts anyway.

This patch reorganizes cgroup.h so that it has consistent logical
grouping. #ifdef CONFIG_CGROUPS is also moved upwards so that it
doesn't end up including a bunch of headers when cgroups is disabled.

This is pure reorganization.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
include/linux/cgroup.h | 556 ++++++++++++++++++++++++-------------------------
1 file changed, 273 insertions(+), 283 deletions(-)

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 96a2ecd..c049e7d 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -8,6 +8,8 @@
*
*/

+#ifdef CONFIG_CGROUPS
+
#include <linux/sched.h>
#include <linux/cpumask.h>
#include <linux/nodemask.h>
@@ -20,18 +22,189 @@

#include <linux/cgroup-defs.h>

-#ifdef CONFIG_CGROUPS
+/* a css_task_iter should be treated as an opaque object */
+struct css_task_iter {
+ struct cgroup_subsys *ss;
+
+ struct list_head *cset_pos;
+ struct list_head *cset_head;
+
+ struct list_head *task_pos;
+ struct list_head *tasks_head;
+ struct list_head *mg_tasks_head;
+};
+
+extern struct cgroup_root cgrp_dfl_root;
+extern struct css_set init_css_set;
+
+#define SUBSYS(_x) extern struct cgroup_subsys _x ## _cgrp_subsys;
+#include <linux/cgroup_subsys.h>
+#undef SUBSYS
+
+bool css_has_online_children(struct cgroup_subsys_state *css);
+struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss);
+struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgroup,
+ struct cgroup_subsys *ss);
+struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry,
+ struct cgroup_subsys *ss);
+
+bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor);
+int cgroup_attach_task_all(struct task_struct *from, struct task_struct *);
+int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from);
+
+int cgroup_add_dfl_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
+int cgroup_add_legacy_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
+int cgroup_rm_cftypes(struct cftype *cfts);
+
+char *task_cgroup_path(struct task_struct *task, char *buf, size_t buflen);
+int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry);
+int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
+ struct pid *pid, struct task_struct *tsk);
+
+void cgroup_fork(struct task_struct *p);
+void cgroup_post_fork(struct task_struct *p);
+void cgroup_exit(struct task_struct *p);
+
+int cgroup_init_early(void);
+int cgroup_init(void);
+
+/*
+ * Iteration helpers and macros.
+ */
+
+struct cgroup_subsys_state *css_next_child(struct cgroup_subsys_state *pos,
+ struct cgroup_subsys_state *parent);
+struct cgroup_subsys_state *css_next_descendant_pre(struct cgroup_subsys_state *pos,
+ struct cgroup_subsys_state *css);
+struct cgroup_subsys_state *css_rightmost_descendant(struct cgroup_subsys_state *pos);
+struct cgroup_subsys_state *css_next_descendant_post(struct cgroup_subsys_state *pos,
+ struct cgroup_subsys_state *css);
+
+struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset);
+struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset);
+
+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);
+
+/**
+ * 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 @parent's children. Must be called under rcu_read_lock().
+ *
+ * If a subsystem synchronizes ->css_online() and the start of iteration, a
+ * css which finished ->css_online() is guaranteed to be visible in the
+ * future iterations and will stay visible until the last reference is put.
+ * A css which hasn't finished ->css_online() or already finished
+ * ->css_offline() may show up during traversal. It's each subsystem's
+ * responsibility to synchronize against on/offlining.
+ *
+ * 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 css_for_each_child(pos, parent) \
+ for ((pos) = css_next_child(NULL, (parent)); (pos); \
+ (pos) = css_next_child((pos), (parent)))
+
+/**
+ * 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 @root's descendants. @root is included in the iteration and the
+ * first node to be visited. Must be called under rcu_read_lock().
+ *
+ * If a subsystem synchronizes ->css_online() and the start of iteration, a
+ * css which finished ->css_online() is guaranteed to be visible in the
+ * future iterations and will stay visible until the last reference is put.
+ * A css which hasn't finished ->css_online() or already finished
+ * ->css_offline() may show up during traversal. It's each subsystem's
+ * responsibility to synchronize against on/offlining.
+ *
+ * For example, the following guarantees that a descendant can't escape
+ * state updates of its ancestors.
+ *
+ * my_online(@css)
+ * {
+ * Lock @css's parent and @css;
+ * Inherit state from the parent;
+ * Unlock both.
+ * }
+ *
+ * my_update_state(@css)
+ * {
+ * css_for_each_descendant_pre(@pos, @css) {
+ * Lock @pos;
+ * if (@pos == @css)
+ * Update @css's state;
+ * else
+ * Verify @pos is alive and inherit state from its parent;
+ * Unlock @pos;
+ * }
+ * }
+ *
+ * As long as the inheriting step, including checking the parent state, is
+ * enclosed inside @pos locking, double-locking the parent isn't necessary
+ * while inheriting. The state update to the parent is guaranteed to be
+ * 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 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.
+ *
+ * Alternatively, a subsystem may choose to use a single global lock to
+ * synchronize ->css_online() and ->css_offline() against tree-walking
+ * operations.
+ *
+ * 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 css_for_each_descendant_pre(pos, css) \
+ for ((pos) = css_next_descendant_pre(NULL, (css)); (pos); \
+ (pos) = css_next_descendant_pre((pos), (css)))
+
+/**
+ * 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 css_for_each_descendant_pre() but performs post-order
+ * traversal instead. @root is included in the iteration and the last
+ * node to be visited.
+ *
+ * If a subsystem synchronizes ->css_online() and the start of iteration, a
+ * css which finished ->css_online() is guaranteed to be visible in the
+ * future iterations and will stay visible until the last reference is put.
+ * A css which hasn't finished ->css_online() or already finished
+ * ->css_offline() may show up during traversal. It's each subsystem's
+ * responsibility to synchronize against on/offlining.
+ *
+ * Note that the walk visibility guarantee example described in pre-order
+ * walk doesn't apply the same to post-order walks.
+ */
+#define css_for_each_descendant_post(pos, css) \
+ for ((pos) = css_next_descendant_post(NULL, (css)); (pos); \
+ (pos) = css_next_descendant_post((pos), (css)))

-extern int cgroup_init_early(void);
-extern int cgroup_init(void);
-extern void cgroup_fork(struct task_struct *p);
-extern void cgroup_post_fork(struct task_struct *p);
-extern void cgroup_exit(struct task_struct *p);
-extern int cgroupstats_build(struct cgroupstats *stats,
- struct dentry *dentry);
+/**
+ * cgroup_taskset_for_each - iterate cgroup_taskset
+ * @task: the loop cursor
+ * @tset: taskset to iterate
+ */
+#define cgroup_taskset_for_each(task, tset) \
+ for ((task) = cgroup_taskset_first((tset)); (task); \
+ (task) = cgroup_taskset_next((tset)))

-extern int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
- struct pid *pid, struct task_struct *tsk);
+/*
+ * Inline functions.
+ */

/**
* css_get - obtain a reference on the specified css
@@ -118,8 +291,87 @@ static inline void css_put_many(struct cgroup_subsys_state *css, unsigned int n)
percpu_ref_put_many(&css->refcnt, n);
}

-extern struct cgroup_root cgrp_dfl_root;
-extern struct css_set init_css_set;
+/**
+ * task_css_set_check - obtain a task's css_set with extra access conditions
+ * @task: the task to obtain css_set for
+ * @__c: extra condition expression to be passed to rcu_dereference_check()
+ *
+ * A task's css_set is RCU protected, initialized and exited while holding
+ * task_lock(), and can only be modified while holding both cgroup_mutex
+ * and task_lock() while the task is alive. This macro verifies that the
+ * caller is inside proper critical section and returns @task's css_set.
+ *
+ * The caller can also specify additional allowed conditions via @__c, such
+ * as locks used during the cgroup_subsys::attach() methods.
+ */
+#ifdef CONFIG_PROVE_RCU
+extern struct mutex cgroup_mutex;
+extern struct rw_semaphore css_set_rwsem;
+#define task_css_set_check(task, __c) \
+ rcu_dereference_check((task)->cgroups, \
+ lockdep_is_held(&cgroup_mutex) || \
+ lockdep_is_held(&css_set_rwsem) || \
+ ((task)->flags & PF_EXITING) || (__c))
+#else
+#define task_css_set_check(task, __c) \
+ rcu_dereference((task)->cgroups)
+#endif
+
+/**
+ * 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()
+ *
+ * Return the cgroup_subsys_state for the (@task, @subsys_id) pair. The
+ * synchronization rules are the same as task_css_set_check().
+ */
+#define task_css_check(task, subsys_id, __c) \
+ task_css_set_check((task), (__c))->subsys[(subsys_id)]
+
+/**
+ * task_css_set - obtain a task's css_set
+ * @task: the task to obtain css_set for
+ *
+ * See task_css_set_check().
+ */
+static inline struct css_set *task_css_set(struct task_struct *task)
+{
+ return task_css_set_check(task, false);
+}
+
+/**
+ * task_css - obtain css for (task, subsys)
+ * @task: the target task
+ * @subsys_id: the target subsystem ID
+ *
+ * See task_css_check().
+ */
+static inline struct cgroup_subsys_state *task_css(struct task_struct *task,
+ int subsys_id)
+{
+ return task_css_check(task, subsys_id, false);
+}
+
+/**
+ * task_css_is_root - test whether a task belongs to the root css
+ * @task: the target task
+ * @subsys_id: the target subsystem ID
+ *
+ * Test whether @task belongs to the root css on the specified subsystem.
+ * May be invoked in any context.
+ */
+static inline bool task_css_is_root(struct task_struct *task, int subsys_id)
+{
+ return task_css_check(task, subsys_id, true) ==
+ init_css_set.subsys[subsys_id];
+}
+
+static inline struct cgroup *task_cgroup(struct task_struct *task,
+ int subsys_id)
+{
+ return task_css(task, subsys_id)->cgroup;
+}

/**
* cgroup_on_dfl - test whether a cgroup is on the default hierarchy
@@ -236,284 +488,22 @@ static inline void pr_cont_cgroup_path(struct cgroup *cgrp)
pr_cont_kernfs_path(cgrp->kn);
}

-char *task_cgroup_path(struct task_struct *task, char *buf, size_t buflen);
-
-int cgroup_add_dfl_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
-int cgroup_add_legacy_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);
-
-struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset);
-struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset);
-
-/**
- * cgroup_taskset_for_each - iterate cgroup_taskset
- * @task: the loop cursor
- * @tset: taskset to iterate
- */
-#define cgroup_taskset_for_each(task, tset) \
- for ((task) = cgroup_taskset_first((tset)); (task); \
- (task) = cgroup_taskset_next((tset)))
-
-#define SUBSYS(_x) extern struct cgroup_subsys _x ## _cgrp_subsys;
-#include <linux/cgroup_subsys.h>
-#undef SUBSYS
-
-/**
- * task_css_set_check - obtain a task's css_set with extra access conditions
- * @task: the task to obtain css_set for
- * @__c: extra condition expression to be passed to rcu_dereference_check()
- *
- * A task's css_set is RCU protected, initialized and exited while holding
- * task_lock(), and can only be modified while holding both cgroup_mutex
- * and task_lock() while the task is alive. This macro verifies that the
- * caller is inside proper critical section and returns @task's css_set.
- *
- * The caller can also specify additional allowed conditions via @__c, such
- * as locks used during the cgroup_subsys::attach() methods.
- */
-#ifdef CONFIG_PROVE_RCU
-extern struct mutex cgroup_mutex;
-extern struct rw_semaphore css_set_rwsem;
-#define task_css_set_check(task, __c) \
- rcu_dereference_check((task)->cgroups, \
- lockdep_is_held(&cgroup_mutex) || \
- lockdep_is_held(&css_set_rwsem) || \
- ((task)->flags & PF_EXITING) || (__c))
-#else
-#define task_css_set_check(task, __c) \
- rcu_dereference((task)->cgroups)
-#endif
-
-/**
- * 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()
- *
- * Return the cgroup_subsys_state for the (@task, @subsys_id) pair. The
- * synchronization rules are the same as task_css_set_check().
- */
-#define task_css_check(task, subsys_id, __c) \
- task_css_set_check((task), (__c))->subsys[(subsys_id)]
-
-/**
- * task_css_set - obtain a task's css_set
- * @task: the task to obtain css_set for
- *
- * See task_css_set_check().
- */
-static inline struct css_set *task_css_set(struct task_struct *task)
-{
- return task_css_set_check(task, false);
-}
-
-/**
- * task_css - obtain css for (task, subsys)
- * @task: the target task
- * @subsys_id: the target subsystem ID
- *
- * See task_css_check().
- */
-static inline struct cgroup_subsys_state *task_css(struct task_struct *task,
- int subsys_id)
-{
- return task_css_check(task, subsys_id, false);
-}
-
-/**
- * task_css_is_root - test whether a task belongs to the root css
- * @task: the target task
- * @subsys_id: the target subsystem ID
- *
- * Test whether @task belongs to the root css on the specified subsystem.
- * May be invoked in any context.
- */
-static inline bool task_css_is_root(struct task_struct *task, int subsys_id)
-{
- return task_css_check(task, subsys_id, true) ==
- init_css_set.subsys[subsys_id];
-}
-
-static inline struct cgroup *task_cgroup(struct task_struct *task,
- int subsys_id)
-{
- return task_css(task, subsys_id)->cgroup;
-}
-
-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);
-
-/**
- * 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 @parent's children. Must be called under rcu_read_lock().
- *
- * If a subsystem synchronizes ->css_online() and the start of iteration, a
- * css which finished ->css_online() is guaranteed to be visible in the
- * future iterations and will stay visible until the last reference is put.
- * A css which hasn't finished ->css_online() or already finished
- * ->css_offline() may show up during traversal. It's each subsystem's
- * responsibility to synchronize against on/offlining.
- *
- * 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 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_subsys_state *
-css_rightmost_descendant(struct cgroup_subsys_state *pos);
-
-/**
- * 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 @root's descendants. @root is included in the iteration and the
- * first node to be visited. Must be called under rcu_read_lock().
- *
- * If a subsystem synchronizes ->css_online() and the start of iteration, a
- * css which finished ->css_online() is guaranteed to be visible in the
- * future iterations and will stay visible until the last reference is put.
- * A css which hasn't finished ->css_online() or already finished
- * ->css_offline() may show up during traversal. It's each subsystem's
- * responsibility to synchronize against on/offlining.
- *
- * For example, the following guarantees that a descendant can't escape
- * state updates of its ancestors.
- *
- * my_online(@css)
- * {
- * Lock @css's parent and @css;
- * Inherit state from the parent;
- * Unlock both.
- * }
- *
- * my_update_state(@css)
- * {
- * css_for_each_descendant_pre(@pos, @css) {
- * Lock @pos;
- * if (@pos == @css)
- * Update @css's state;
- * else
- * Verify @pos is alive and inherit state from its parent;
- * Unlock @pos;
- * }
- * }
- *
- * As long as the inheriting step, including checking the parent state, is
- * enclosed inside @pos locking, double-locking the parent isn't necessary
- * while inheriting. The state update to the parent is guaranteed to be
- * 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 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.
- *
- * Alternatively, a subsystem may choose to use a single global lock to
- * synchronize ->css_online() and ->css_offline() against tree-walking
- * operations.
- *
- * 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 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_subsys_state *
-css_next_descendant_post(struct cgroup_subsys_state *pos,
- struct cgroup_subsys_state *css);
-
-/**
- * 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 css_for_each_descendant_pre() but performs post-order
- * traversal instead. @root is included in the iteration and the last
- * node to be visited.
- *
- * If a subsystem synchronizes ->css_online() and the start of iteration, a
- * css which finished ->css_online() is guaranteed to be visible in the
- * future iterations and will stay visible until the last reference is put.
- * A css which hasn't finished ->css_online() or already finished
- * ->css_offline() may show up during traversal. It's each subsystem's
- * responsibility to synchronize against on/offlining.
- *
- * Note that the walk visibility guarantee example described in pre-order
- * walk doesn't apply the same to post-order walks.
- */
-#define css_for_each_descendant_post(pos, css) \
- for ((pos) = css_next_descendant_post(NULL, (css)); (pos); \
- (pos) = css_next_descendant_post((pos), (css)))
-
-bool css_has_online_children(struct cgroup_subsys_state *css);
-
-/* A css_task_iter should be treated as an opaque object */
-struct css_task_iter {
- struct cgroup_subsys *ss;
-
- struct list_head *cset_pos;
- struct list_head *cset_head;
-
- struct list_head *task_pos;
- struct list_head *tasks_head;
- struct list_head *mg_tasks_head;
-};
-
-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 cgroup_attach_task_all(struct task_struct *from, struct task_struct *);
-int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from);
-
-struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgroup,
- struct cgroup_subsys *ss);
-struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry,
- struct cgroup_subsys *ss);
-
-#else /* !CONFIG_CGROUPS */
+#else /* !CONFIG_CGROUPS */

struct cgroup_subsys_state;

-static inline int cgroup_init_early(void) { return 0; }
-static inline int cgroup_init(void) { return 0; }
+static inline void css_put(struct cgroup_subsys_state *css) {}
+static inline int cgroup_attach_task_all(struct task_struct *from,
+ struct task_struct *t) { return 0; }
+static inline int cgroupstats_build(struct cgroupstats *stats,
+ struct dentry *dentry) { return -EINVAL; }
+
static inline void cgroup_fork(struct task_struct *p) {}
static inline void cgroup_post_fork(struct task_struct *p) {}
static inline void cgroup_exit(struct task_struct *p) {}

-static inline int cgroupstats_build(struct cgroupstats *stats,
- struct dentry *dentry)
-{
- return -EINVAL;
-}
-
-static inline void css_put(struct cgroup_subsys_state *css) {}
-
-/* No cgroups - nothing to do */
-static inline int cgroup_attach_task_all(struct task_struct *from,
- struct task_struct *t)
-{
- return 0;
-}
+static inline int cgroup_init_early(void) { return 0; }
+static inline int cgroup_init(void) { return 0; }

#endif /* !CONFIG_CGROUPS */

--
2.1.0


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