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cgroup: kill css_id
The only user of css_id was memcg, and it has been convered to use cgroup->id, so kill css_id. Signed-off-by: Li Zefan <lizefan@huwei.com> Reviewed-by: Michal Hocko <mhocko@suse.cz> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Li Zefan
Tejun Heo
parent
b862783594
commit
2ff2a7d03b
@ -612,11 +612,6 @@ struct cgroup_subsys {
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int subsys_id;
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int disabled;
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int early_init;
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/*
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* True if this subsys uses ID. ID is not available before cgroup_init()
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* (not available in early_init time.)
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*/
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bool use_id;
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/*
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* If %false, this subsystem is properly hierarchical -
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@ -642,9 +637,6 @@ struct cgroup_subsys {
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*/
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struct cgroupfs_root *root;
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struct list_head sibling;
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/* used when use_id == true */
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struct idr idr;
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spinlock_t id_lock;
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/* list of cftype_sets */
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struct list_head cftsets;
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@ -875,35 +867,6 @@ int css_scan_tasks(struct cgroup_subsys_state *css,
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int cgroup_attach_task_all(struct task_struct *from, struct task_struct *);
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int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from);
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/*
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* CSS ID is ID for cgroup_subsys_state structs under subsys. This only works
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* if cgroup_subsys.use_id == true. It can be used for looking up and scanning.
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* CSS ID is assigned at cgroup allocation (create) automatically
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* and removed when subsys calls free_css_id() function. This is because
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* the lifetime of cgroup_subsys_state is subsys's matter.
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*
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* Looking up and scanning function should be called under rcu_read_lock().
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* Taking cgroup_mutex is not necessary for following calls.
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* But the css returned by this routine can be "not populated yet" or "being
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* destroyed". The caller should check css and cgroup's status.
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*/
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/*
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* Typically Called at ->destroy(), or somewhere the subsys frees
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* cgroup_subsys_state.
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*/
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void free_css_id(struct cgroup_subsys *ss, struct cgroup_subsys_state *css);
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/* Find a cgroup_subsys_state which has given ID */
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struct cgroup_subsys_state *css_lookup(struct cgroup_subsys *ss, int id);
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/* Returns true if root is ancestor of cg */
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bool css_is_ancestor(struct cgroup_subsys_state *cg,
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const struct cgroup_subsys_state *root);
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/* Get id and depth of css */
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unsigned short css_id(struct cgroup_subsys_state *css);
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struct cgroup_subsys_state *css_from_dir(struct dentry *dentry,
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struct cgroup_subsys *ss);
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248
kernel/cgroup.c
248
kernel/cgroup.c
@ -124,38 +124,6 @@ struct cfent {
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struct simple_xattrs xattrs;
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};
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/*
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* CSS ID -- ID per subsys's Cgroup Subsys State(CSS). used only when
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* cgroup_subsys->use_id != 0.
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*/
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#define CSS_ID_MAX (65535)
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struct css_id {
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/*
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* The css to which this ID points. This pointer is set to valid value
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* after cgroup is populated. If cgroup is removed, this will be NULL.
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* This pointer is expected to be RCU-safe because destroy()
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* is called after synchronize_rcu(). But for safe use, css_tryget()
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* should be used for avoiding race.
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*/
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struct cgroup_subsys_state __rcu *css;
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/*
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* ID of this css.
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*/
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unsigned short id;
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/*
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* Depth in hierarchy which this ID belongs to.
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*/
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unsigned short depth;
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/*
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* ID is freed by RCU. (and lookup routine is RCU safe.)
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*/
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struct rcu_head rcu_head;
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/*
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* Hierarchy of CSS ID belongs to.
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*/
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unsigned short stack[0]; /* Array of Length (depth+1) */
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};
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/*
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* cgroup_event represents events which userspace want to receive.
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*/
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@ -387,9 +355,6 @@ struct cgrp_cset_link {
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static struct css_set init_css_set;
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static struct cgrp_cset_link init_cgrp_cset_link;
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static int cgroup_init_idr(struct cgroup_subsys *ss,
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struct cgroup_subsys_state *css);
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/*
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* css_set_lock protects the list of css_set objects, and the chain of
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* tasks off each css_set. Nests outside task->alloc_lock due to
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@ -841,8 +806,6 @@ static struct backing_dev_info cgroup_backing_dev_info = {
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.capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
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};
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static int alloc_css_id(struct cgroup_subsys_state *child_css);
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static struct inode *cgroup_new_inode(umode_t mode, struct super_block *sb)
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{
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struct inode *inode = new_inode(sb);
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@ -4242,21 +4205,6 @@ static int cgroup_populate_dir(struct cgroup *cgrp, unsigned long subsys_mask)
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goto err;
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}
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}
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/* This cgroup is ready now */
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for_each_root_subsys(cgrp->root, ss) {
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struct cgroup_subsys_state *css = cgroup_css(cgrp, ss);
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struct css_id *id = rcu_dereference_protected(css->id, true);
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/*
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* Update id->css pointer and make this css visible from
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* CSS ID functions. This pointer will be dereferened
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* from RCU-read-side without locks.
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*/
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if (id)
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rcu_assign_pointer(id->css, css);
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}
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return 0;
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err:
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cgroup_clear_dir(cgrp, subsys_mask);
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@ -4325,7 +4273,6 @@ static void init_css(struct cgroup_subsys_state *css, struct cgroup_subsys *ss,
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css->cgroup = cgrp;
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css->ss = ss;
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css->flags = 0;
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css->id = NULL;
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if (cgrp->parent)
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css->parent = cgroup_css(cgrp->parent, ss);
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@ -4457,12 +4404,6 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
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goto err_free_all;
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init_css(css, ss, cgrp);
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if (ss->use_id) {
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err = alloc_css_id(css);
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if (err)
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goto err_free_all;
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}
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}
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/*
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@ -4927,12 +4868,6 @@ int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
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/* our new subsystem will be attached to the dummy hierarchy. */
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init_css(css, ss, cgroup_dummy_top);
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/* init_idr must be after init_css() because it sets css->id. */
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if (ss->use_id) {
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ret = cgroup_init_idr(ss, css);
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if (ret)
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goto err_unload;
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}
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/*
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* Now we need to entangle the css into the existing css_sets. unlike
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@ -4998,9 +4933,6 @@ void cgroup_unload_subsys(struct cgroup_subsys *ss)
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offline_css(cgroup_css(cgroup_dummy_top, ss));
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if (ss->use_id)
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idr_destroy(&ss->idr);
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/* deassign the subsys_id */
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cgroup_subsys[ss->subsys_id] = NULL;
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@ -5027,8 +4959,7 @@ void cgroup_unload_subsys(struct cgroup_subsys *ss)
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/*
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* remove subsystem's css from the cgroup_dummy_top and free it -
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* need to free before marking as null because ss->css_free needs
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* the cgrp->subsys pointer to find their state. note that this
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* also takes care of freeing the css_id.
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* the cgrp->subsys pointer to find their state.
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*/
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ss->css_free(cgroup_css(cgroup_dummy_top, ss));
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RCU_INIT_POINTER(cgroup_dummy_top->subsys[ss->subsys_id], NULL);
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@ -5099,8 +5030,6 @@ int __init cgroup_init(void)
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for_each_builtin_subsys(ss, i) {
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if (!ss->early_init)
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cgroup_init_subsys(ss);
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if (ss->use_id)
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cgroup_init_idr(ss, init_css_set.subsys[ss->subsys_id]);
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}
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/* allocate id for the dummy hierarchy */
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@ -5520,181 +5449,6 @@ static int __init cgroup_disable(char *str)
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}
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__setup("cgroup_disable=", cgroup_disable);
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/*
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* Functons for CSS ID.
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*/
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/* to get ID other than 0, this should be called when !cgroup_is_dead() */
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unsigned short css_id(struct cgroup_subsys_state *css)
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{
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struct css_id *cssid;
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/*
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* This css_id() can return correct value when somone has refcnt
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* on this or this is under rcu_read_lock(). Once css->id is allocated,
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* it's unchanged until freed.
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*/
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cssid = rcu_dereference_raw(css->id);
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if (cssid)
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return cssid->id;
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return 0;
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}
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EXPORT_SYMBOL_GPL(css_id);
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/**
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* css_is_ancestor - test "root" css is an ancestor of "child"
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* @child: the css to be tested.
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* @root: the css supporsed to be an ancestor of the child.
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*
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* Returns true if "root" is an ancestor of "child" in its hierarchy. Because
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* this function reads css->id, the caller must hold rcu_read_lock().
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* But, considering usual usage, the csses should be valid objects after test.
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* Assuming that the caller will do some action to the child if this returns
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* returns true, the caller must take "child";s reference count.
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* If "child" is valid object and this returns true, "root" is valid, too.
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*/
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bool css_is_ancestor(struct cgroup_subsys_state *child,
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const struct cgroup_subsys_state *root)
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{
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struct css_id *child_id;
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struct css_id *root_id;
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child_id = rcu_dereference(child->id);
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if (!child_id)
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return false;
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root_id = rcu_dereference(root->id);
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if (!root_id)
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return false;
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if (child_id->depth < root_id->depth)
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return false;
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if (child_id->stack[root_id->depth] != root_id->id)
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return false;
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return true;
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}
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void free_css_id(struct cgroup_subsys *ss, struct cgroup_subsys_state *css)
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{
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struct css_id *id = rcu_dereference_protected(css->id, true);
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/* When this is called before css_id initialization, id can be NULL */
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if (!id)
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return;
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BUG_ON(!ss->use_id);
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rcu_assign_pointer(id->css, NULL);
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rcu_assign_pointer(css->id, NULL);
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spin_lock(&ss->id_lock);
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idr_remove(&ss->idr, id->id);
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spin_unlock(&ss->id_lock);
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kfree_rcu(id, rcu_head);
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}
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EXPORT_SYMBOL_GPL(free_css_id);
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/*
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* This is called by init or create(). Then, calls to this function are
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* always serialized (By cgroup_mutex() at create()).
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*/
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static struct css_id *get_new_cssid(struct cgroup_subsys *ss, int depth)
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{
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struct css_id *newid;
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int ret, size;
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BUG_ON(!ss->use_id);
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size = sizeof(*newid) + sizeof(unsigned short) * (depth + 1);
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newid = kzalloc(size, GFP_KERNEL);
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if (!newid)
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return ERR_PTR(-ENOMEM);
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idr_preload(GFP_KERNEL);
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spin_lock(&ss->id_lock);
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/* Don't use 0. allocates an ID of 1-65535 */
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ret = idr_alloc(&ss->idr, newid, 1, CSS_ID_MAX + 1, GFP_NOWAIT);
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spin_unlock(&ss->id_lock);
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idr_preload_end();
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/* Returns error when there are no free spaces for new ID.*/
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if (ret < 0)
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goto err_out;
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newid->id = ret;
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newid->depth = depth;
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return newid;
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err_out:
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kfree(newid);
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return ERR_PTR(ret);
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}
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static int __init_or_module cgroup_init_idr(struct cgroup_subsys *ss,
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struct cgroup_subsys_state *rootcss)
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{
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struct css_id *newid;
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spin_lock_init(&ss->id_lock);
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idr_init(&ss->idr);
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newid = get_new_cssid(ss, 0);
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if (IS_ERR(newid))
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return PTR_ERR(newid);
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newid->stack[0] = newid->id;
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RCU_INIT_POINTER(newid->css, rootcss);
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RCU_INIT_POINTER(rootcss->id, newid);
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return 0;
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}
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static int alloc_css_id(struct cgroup_subsys_state *child_css)
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{
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struct cgroup_subsys_state *parent_css = css_parent(child_css);
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struct css_id *child_id, *parent_id;
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int i, depth;
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parent_id = rcu_dereference_protected(parent_css->id, true);
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depth = parent_id->depth + 1;
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child_id = get_new_cssid(child_css->ss, depth);
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if (IS_ERR(child_id))
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return PTR_ERR(child_id);
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for (i = 0; i < depth; i++)
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child_id->stack[i] = parent_id->stack[i];
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child_id->stack[depth] = child_id->id;
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/*
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* child_id->css pointer will be set after this cgroup is available
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* see cgroup_populate_dir()
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*/
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rcu_assign_pointer(child_css->id, child_id);
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return 0;
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}
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/**
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* css_lookup - lookup css by id
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* @ss: cgroup subsys to be looked into.
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* @id: the id
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*
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* Returns pointer to cgroup_subsys_state if there is valid one with id.
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* NULL if not. Should be called under rcu_read_lock()
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*/
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struct cgroup_subsys_state *css_lookup(struct cgroup_subsys *ss, int id)
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{
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struct css_id *cssid = NULL;
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BUG_ON(!ss->use_id);
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cssid = idr_find(&ss->idr, id);
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if (unlikely(!cssid))
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return NULL;
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return rcu_dereference(cssid->css);
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}
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EXPORT_SYMBOL_GPL(css_lookup);
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/**
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* css_from_dir - get corresponding css from the dentry of a cgroup dir
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* @dentry: directory dentry of interest
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