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Commit 59f5296b authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: misc preps for kernfs conversion 



* Un-inline seq_css().  After kernfs conversion, the function will
  need to dereference internal data structures.

* Add cgroup_get/put_root() and replace direct super_block->s_active
  manipulatinos with them.  These will be converted to kernfs_root
  refcnting.

* Add cgroup_get/put() and replace dget/put() on cgrp->dentry with
  them.  These will be converted to kernfs refcnting.

* Update current_css_set_cg_links_read() to use cgroup_name() instead
  of reaching into the dentry name.  The end result is the same.

These changes don't make functional differences but will make
transition to kernfs easier.

v2: Rebased on top of 0ab02ca8 ("cgroup: protect modifications to
    cgroup_idr with cgroup_mutex").

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
parent b1664924

include/linux/cgroup.h

+2 −6
Original line number Diff line number Diff line
@@ -516,18 +516,14 @@ static inline ino_t cgroup_ino(struct cgroup *cgrp) 
		return 0;

}



static inline struct cgroup_subsys_state *seq_css(struct seq_file *seq)

{

	struct cgroup_open_file *of = seq->private;

	return of->cfe->css;

}



static inline struct cftype *seq_cft(struct seq_file *seq)

{

	struct cgroup_open_file *of = seq->private;

	return of->cfe->type;

}



struct cgroup_subsys_state *seq_css(struct seq_file *seq);



int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);

int cgroup_rm_cftypes(struct cftype *cfts);

kernel/cgroup.c

+53 −32
Original line number Diff line number Diff line
@@ -169,6 +169,7 @@ static int need_forkexit_callback __read_mostly; 


static struct cftype cgroup_base_files[];



static void cgroup_put(struct cgroup *cgrp);

static void cgroup_destroy_css_killed(struct cgroup *cgrp);

static int cgroup_destroy_locked(struct cgroup *cgrp);

static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[],
@@ -204,6 +205,13 @@ static inline bool cgroup_is_dead(const struct cgroup *cgrp) 
	return test_bit(CGRP_DEAD, &cgrp->flags);

}



struct cgroup_subsys_state *seq_css(struct seq_file *seq)

{

	struct cgroup_open_file *of = seq->private;

	return of->cfe->css;

}

EXPORT_SYMBOL_GPL(seq_css);



/**

 * cgroup_is_descendant - test ancestry

 * @cgrp: the cgroup to be tested
@@ -682,6 +690,16 @@ static struct css_set *find_css_set(struct css_set *old_cset, 
	return cset;

}



static void cgroup_get_root(struct cgroupfs_root *root)

{

	atomic_inc(&root->sb->s_active);

}



static void cgroup_put_root(struct cgroupfs_root *root)

{

	deactivate_super(root->sb);

}



/*

 * Return the cgroup for "task" from the given hierarchy. Must be

 * called with cgroup_mutex held.
@@ -837,18 +855,14 @@ static void cgroup_free_fn(struct work_struct *work) 
	mutex_unlock(&cgroup_mutex);



	/*

	 * We get a ref to the parent's dentry, and put the ref when

	 * this cgroup is being freed, so it's guaranteed that the

	 * parent won't be destroyed before its children.

	 * We get a ref to the parent, and put the ref when this cgroup is

	 * being freed, so it's guaranteed that the parent won't be

	 * destroyed before its children.

	 */

	dput(cgrp->parent->dentry);

	cgroup_put(cgrp->parent);



	/*

	 * Drop the active superblock reference that we took when we

	 * created the cgroup. This will free cgrp->root, if we are

	 * holding the last reference to @sb.

	 */

	deactivate_super(cgrp->root->sb);

	/* put the root reference that we took when we created the cgroup */

	cgroup_put_root(cgrp->root);



	cgroup_pidlist_destroy_all(cgrp);
@@ -866,6 +880,11 @@ static void cgroup_free_rcu(struct rcu_head *head) 
	queue_work(cgroup_destroy_wq, &cgrp->destroy_work);

}



static void cgroup_get(struct cgroup *cgrp)

{

	dget(cgrp->dentry);

}



static void cgroup_diput(struct dentry *dentry, struct inode *inode)

{

	/* is dentry a directory ? if so, kfree() associated cgroup */
@@ -899,6 +918,11 @@ static void cgroup_diput(struct dentry *dentry, struct inode *inode) 
	iput(inode);

}



static void cgroup_put(struct cgroup *cgrp)

{

	dput(cgrp->dentry);

}



static void remove_dir(struct dentry *d)

{

	struct dentry *parent = dget(d->d_parent);
@@ -2724,7 +2748,7 @@ static int cgroup_cfts_commit(struct cftype *cfts, bool is_add) 
	struct cgroup_subsys *ss = cfts[0].ss;

	struct cgroup *root = &ss->root->top_cgroup;

	struct super_block *sb = ss->root->sb;

	struct dentry *prev = NULL;

	struct cgroup *prev = NULL;

	struct inode *inode;

	struct cgroup_subsys_state *css;

	u64 update_before;
@@ -2754,9 +2778,10 @@ static int cgroup_cfts_commit(struct cftype *cfts, bool is_add) 
			continue;



		inode = cgrp->dentry->d_inode;

		dget(cgrp->dentry);

		dput(prev);

		prev = cgrp->dentry;

		cgroup_get(cgrp);

		if (prev)

			cgroup_put(prev);

		prev = cgrp;



		mutex_unlock(&cgroup_tree_mutex);

		mutex_lock(&inode->i_mutex);
@@ -2768,8 +2793,8 @@ static int cgroup_cfts_commit(struct cftype *cfts, bool is_add) 
			break;

	}

	mutex_unlock(&cgroup_tree_mutex);

	dput(prev);

	deactivate_super(sb);

	cgroup_put(prev);

	cgroup_put_root(ss->root);

	return ret;

}
@@ -3863,11 +3888,9 @@ static int cgroup_write_notify_on_release(struct cgroup_subsys_state *css, 
 */

static void cgroup_dput(struct cgroup *cgrp)

{

	struct super_block *sb = cgrp->root->sb;



	atomic_inc(&sb->s_active);

	dput(cgrp->dentry);

	deactivate_super(sb);

	cgroup_get_root(cgrp->root);

	cgroup_put(cgrp);

	cgroup_put_root(cgrp->root);

}



static u64 cgroup_clone_children_read(struct cgroup_subsys_state *css,
@@ -4118,7 +4141,7 @@ static int create_css(struct cgroup *cgrp, struct cgroup_subsys *ss) 
	if (err)

		goto err_free;



	dget(cgrp->dentry);

	cgroup_get(cgrp);

	css_get(css->parent);



	if (ss->broken_hierarchy && !ss->warned_broken_hierarchy &&
@@ -4197,7 +4220,7 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry, 
	 * can be done outside cgroup_mutex, since the sb can't

	 * disappear while someone has an open control file on the

	 * fs */

	atomic_inc(&sb->s_active);

	cgroup_get_root(root);



	init_cgroup_housekeeping(cgrp);
@@ -4231,7 +4254,7 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry, 
	root->number_of_cgroups++;



	/* hold a ref to the parent's dentry */

	dget(parent->dentry);

	cgroup_get(parent);



	/*

	 * @cgrp is now fully operational.  If something fails after this
@@ -4261,7 +4284,7 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry, 
err_free_id:

	idr_remove(&root->cgroup_idr, cgrp->id);

	/* Release the reference count that we took on the superblock */

	deactivate_super(sb);

	cgroup_put_root(root);

err_unlock:

	mutex_unlock(&cgroup_mutex);

err_unlock_tree:
@@ -4493,7 +4516,6 @@ static int cgroup_destroy_locked(struct cgroup *cgrp) 
static void cgroup_destroy_css_killed(struct cgroup *cgrp)

{

	struct cgroup *parent = cgrp->parent;

	struct dentry *d = cgrp->dentry;



	lockdep_assert_held(&cgroup_tree_mutex);

	lockdep_assert_held(&cgroup_mutex);
@@ -4501,7 +4523,7 @@ static void cgroup_destroy_css_killed(struct cgroup *cgrp) 
	/* delete this cgroup from parent->children */

	list_del_rcu(&cgrp->sibling);



	dput(d);

	cgroup_put(cgrp);



	set_bit(CGRP_RELEASABLE, &parent->flags);

	check_for_release(parent);
@@ -5161,12 +5183,11 @@ static int current_css_set_cg_links_read(struct seq_file *seq, void *v) 
	cset = rcu_dereference(current->cgroups);

	list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {

		struct cgroup *c = link->cgrp;

		const char *name;

		const char *name = "?";



		if (c != cgroup_dummy_top)

			name = cgroup_name(c);



		if (c->dentry)

			name = c->dentry->d_name.name;

		else

			name = "?";

		seq_printf(seq, "Root %d group %s\n",

			   c->root->hierarchy_id, name);

	}