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Commit e8c82d20 authored by Li Zefan's avatar Li Zefan Committed by Tejun Heo
Browse files

cgroup: convert cgroup_cft_commit() to use cgroup_for_each_descendant_pre() 



We used root->allcg_list to iterate cgroup hierarchy because at that time
cgroup_for_each_descendant_pre() hasn't been invented.

tj: In cgroup_cfts_commit(), s/@serial_nr/@update_upto/, move the
    assignment right above releasing cgroup_mutex and explain what's
    going on there.

Signed-off-by: default avatarLi Zefan <lizefan@huawei.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 794611a1

include/linux/cgroup.h

+0 −6
Original line number Diff line number Diff line
@@ -206,9 +206,6 @@ struct cgroup { 
	 */

	struct list_head cset_links;



	struct list_head allcg_node;	/* cgroupfs_root->allcg_list */

	struct list_head cft_q_node;	/* used during cftype add/rm */



	/*

	 * Linked list running through all cgroups that can

	 * potentially be reaped by the release agent. Protected by
@@ -313,9 +310,6 @@ struct cgroupfs_root { 
	/* A list running through the active hierarchies */

	struct list_head root_list;



	/* All cgroups on this root, cgroup_mutex protected */

	struct list_head allcg_list;



	/* Hierarchy-specific flags */

	unsigned long flags;

kernel/cgroup.c

+44 −36
Original line number Diff line number Diff line
@@ -1399,7 +1399,6 @@ static void init_cgroup_housekeeping(struct cgroup *cgrp) 
	INIT_LIST_HEAD(&cgrp->children);

	INIT_LIST_HEAD(&cgrp->files);

	INIT_LIST_HEAD(&cgrp->cset_links);

	INIT_LIST_HEAD(&cgrp->allcg_node);

	INIT_LIST_HEAD(&cgrp->release_list);

	INIT_LIST_HEAD(&cgrp->pidlists);

	mutex_init(&cgrp->pidlist_mutex);
@@ -1414,12 +1413,10 @@ static void init_cgroup_root(struct cgroupfs_root *root) 


	INIT_LIST_HEAD(&root->subsys_list);

	INIT_LIST_HEAD(&root->root_list);

	INIT_LIST_HEAD(&root->allcg_list);

	root->number_of_cgroups = 1;

	cgrp->root = root;

	cgrp->name = &root_cgroup_name;

	init_cgroup_housekeeping(cgrp);

	list_add_tail(&cgrp->allcg_node, &root->allcg_list);

}



static int cgroup_init_root_id(struct cgroupfs_root *root)
@@ -2785,65 +2782,78 @@ static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys, 
	return ret;

}



static DEFINE_MUTEX(cgroup_cft_mutex);



static void cgroup_cfts_prepare(void)

	__acquires(&cgroup_cft_mutex) __acquires(&cgroup_mutex)

	__acquires(&cgroup_mutex)

{

	/*

	 * Thanks to the entanglement with vfs inode locking, we can't walk

	 * the existing cgroups under cgroup_mutex and create files.

	 * Instead, we increment reference on all cgroups and build list of

	 * them using @cgrp->cft_q_node.  Grab cgroup_cft_mutex to ensure

	 * exclusive access to the field.

	 * Instead, we use cgroup_for_each_descendant_pre() and drop RCU

	 * read lock before calling cgroup_addrm_files().

	 */

	mutex_lock(&cgroup_cft_mutex);

	mutex_lock(&cgroup_mutex);

}



static void cgroup_cfts_commit(struct cgroup_subsys *ss,

			       struct cftype *cfts, bool is_add)

	__releases(&cgroup_mutex) __releases(&cgroup_cft_mutex)

	__releases(&cgroup_mutex)

{

	LIST_HEAD(pending);

	struct cgroup *cgrp, *n;

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

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

	struct dentry *prev = NULL;

	struct inode *inode;

	u64 update_upto;



	/* %NULL @cfts indicates abort and don't bother if @ss isn't attached */

	if (cfts && ss->root != &rootnode &&

	    atomic_inc_not_zero(sb->s_active)) {

		list_for_each_entry(cgrp, &ss->root->allcg_list, allcg_node) {

			dget(cgrp->dentry);

			list_add_tail(&cgrp->cft_q_node, &pending);

		}

	} else {

		sb = NULL;

	}



	if (!cfts || ss->root == &rootnode ||

	    !atomic_inc_not_zero(&sb->s_active)) {

		mutex_unlock(&cgroup_mutex);

		return;

	}



	/*

	 * All new cgroups will see @cfts update on @ss->cftsets.  Add/rm

	 * files for all cgroups which were created before.

	 * All cgroups which are created after we drop cgroup_mutex will

	 * have the updated set of files, so we only need to update the

	 * cgroups created before the current @cgroup_serial_nr_cursor.

	 */

	list_for_each_entry_safe(cgrp, n, &pending, cft_q_node) {

		struct inode *inode = cgrp->dentry->d_inode;

	update_upto = atomic64_read(&cgroup_serial_nr_cursor);



	mutex_unlock(&cgroup_mutex);



	/* @root always needs to be updated */

	inode = root->dentry->d_inode;

	mutex_lock(&inode->i_mutex);

	mutex_lock(&cgroup_mutex);

		if (!cgroup_is_dead(cgrp))

	cgroup_addrm_files(root, ss, cfts, is_add);

	mutex_unlock(&cgroup_mutex);

	mutex_unlock(&inode->i_mutex);



	/* add/rm files for all cgroups created before */

	rcu_read_lock();

	cgroup_for_each_descendant_pre(cgrp, root) {

		if (cgroup_is_dead(cgrp))

			continue;



		inode = cgrp->dentry->d_inode;

		dget(cgrp->dentry);

		rcu_read_unlock();



		dput(prev);

		prev = cgrp->dentry;



		mutex_lock(&inode->i_mutex);

		mutex_lock(&cgroup_mutex);

		if (cgrp->serial_nr <= update_upto && !cgroup_is_dead(cgrp))

			cgroup_addrm_files(cgrp, ss, cfts, is_add);

		mutex_unlock(&cgroup_mutex);

		mutex_unlock(&inode->i_mutex);



		list_del_init(&cgrp->cft_q_node);

		dput(cgrp->dentry);

		rcu_read_lock();

	}



	if (sb)

	rcu_read_unlock();

	dput(prev);

	deactivate_super(sb);



	mutex_unlock(&cgroup_cft_mutex);

}



/**
@@ -4320,7 +4330,6 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry, 
	cgrp->serial_nr = atomic64_inc_return(&cgroup_serial_nr_cursor);



	/* allocation complete, commit to creation */

	list_add_tail(&cgrp->allcg_node, &root->allcg_list);

	list_add_tail_rcu(&cgrp->sibling, &cgrp->parent->children);

	root->number_of_cgroups++;
@@ -4559,7 +4568,6 @@ static void cgroup_offline_fn(struct work_struct *work) 


	/* delete this cgroup from parent->children */

	list_del_rcu(&cgrp->sibling);

	list_del_init(&cgrp->allcg_node);



	dput(d);