/* 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;
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;
/* 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);
* 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
* 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);
}
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);
*/
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;
#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)
+{
+ struct cgroup *parent_cgrp = css->cgroup->parent;
+
+ if (!parent_cgrp)
+ return NULL;
+
+ if (css->ss)
+ return parent_cgrp->subsys[css->ss->subsys_id];
+ else
+ return &parent_cgrp->dummy_css;
+}
+
+/**
+ * cgroup_css - obtain a cgroup's css for the specified subsystem
+ * @cgrp: the cgroup of interest
+ * @subsys_id: the subsystem of interest
+ *
+ * Return @cgrp's css (cgroup_subsys_state) associated with @subsys_id.
+ */
+static inline struct cgroup_subsys_state *cgroup_css(struct cgroup *cgrp,
+ int subsys_id)
{
return cgrp->subsys[subsys_id];
}
#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()
* 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)]
/**
}
/**
- * 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;
}
/**
return idr_find(&ss->root->cgroup_idr, id);
}
-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);
/**
- * 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. 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;
+ * Lock @css;
+ * Update @css's state;
+ * Unlock @css;
*
- * 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;
+ * Verify @pos is alive and inherit state from @pos's parent;
* Unlock @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.
* 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
+ * Similar to css_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.
*/
-#define cgroup_for_each_descendant_post(pos, cgroup) \
- for (pos = cgroup_next_descendant_post(NULL, (cgroup)); (pos); \
- pos = cgroup_next_descendant_post((pos), (cgroup)))
+#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 cgroup_iter should be treated as an opaque object */
struct cgroup_iter {
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