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Commit d427dfeb authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: factor out cgroup_setup_root() from cgroup_mount() 



Factor out new root initialization into cgroup_setup_root() from
cgroup_mount().  This makes it easier to follow and will ease kernfs
conversion.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
parent 8e30e2b8

kernel/cgroup.c

+113 −98
Original line number Diff line number Diff line
@@ -1455,67 +1455,30 @@ static int cgroup_get_rootdir(struct super_block *sb) 
	return 0;

}



static struct dentry *cgroup_mount(struct file_system_type *fs_type,

			 int flags, const char *unused_dev_name,

			 void *data)

static int cgroup_setup_root(struct cgroupfs_root *root)

{

	LIST_HEAD(tmp_links);

	struct super_block *sb = NULL;

	struct inode *inode = NULL;

	struct cgroupfs_root *root = NULL;

	struct cgroup_sb_opts opts;

	struct cgroupfs_root *new_root;

	const struct cred *cred;

	int ret;



	mutex_lock(&cgroup_tree_mutex);

	mutex_lock(&cgroup_mutex);



	/* First find the desired set of subsystems */

	ret = parse_cgroupfs_options(data, &opts);

	if (ret)

		goto out_unlock;



	/*

	 * Allocate a new cgroup root. We may not need it if we're

	 * reusing an existing hierarchy.

	 */

	new_root = cgroup_root_from_opts(&opts);

	if (IS_ERR(new_root)) {

		ret = PTR_ERR(new_root);

		goto out_unlock;

	}

	opts.new_root = new_root;



	/* Locate an existing or new sb for this hierarchy */

	mutex_unlock(&cgroup_mutex);

	mutex_unlock(&cgroup_tree_mutex);

	sb = sget(fs_type, cgroup_test_super, cgroup_set_super, 0, &opts);

	mutex_lock(&cgroup_tree_mutex);

	mutex_lock(&cgroup_mutex);

	if (IS_ERR(sb)) {

		ret = PTR_ERR(sb);

		cgroup_free_root(opts.new_root);

		goto out_unlock;

	}



	root = sb->s_fs_info;

	BUG_ON(!root);

	if (root == opts.new_root) {

		/* We used the new root structure, so this is a new hierarchy */

	struct super_block *sb = root->sb;

	struct cgroup *root_cgrp = &root->top_cgroup;

	struct cgroupfs_root *existing_root;

		int i;

	struct css_set *cset;

	struct inode *inode;

	const struct cred *cred;

	int i, ret;



	lockdep_assert_held(&cgroup_tree_mutex);

	lockdep_assert_held(&cgroup_mutex);

	BUG_ON(sb->s_root != NULL);



	mutex_unlock(&cgroup_mutex);

	mutex_unlock(&cgroup_tree_mutex);



	ret = cgroup_get_rootdir(sb);

		if (ret)

			goto out_unlock;

	if (ret) {

		mutex_lock(&cgroup_tree_mutex);

		mutex_lock(&cgroup_mutex);

		return ret;

	}

	inode = sb->s_root->d_inode;



	mutex_lock(&inode->i_mutex);
@@ -1527,7 +1490,7 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, 
		goto out_unlock;

	root_cgrp->id = ret;



		/* Check for name clashes with existing mounts */

	/* check for name clashes with existing mounts */

	ret = -EBUSY;

	if (strlen(root->name))

		for_each_active_root(existing_root)
@@ -1535,10 +1498,9 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, 
				goto out_unlock;



	/*

		 * We're accessing css_set_count without locking

		 * css_set_lock here, but that's OK - it can only be

		 * increased by someone holding cgroup_lock, and

		 * that's us. The worst that can happen is that we

	 * We're accessing css_set_count without locking css_set_lock here,

	 * but that's OK - it can only be increased by someone holding

	 * cgroup_lock, and that's us. The worst that can happen is that we

	 * have some link structures left over

	 */

	ret = allocate_cgrp_cset_links(css_set_count, &tmp_links);
@@ -1554,11 +1516,11 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, 
	root_cgrp->dentry = sb->s_root;



	/*

		 * We're inside get_sb() and will call lookup_one_len() to

		 * create the root files, which doesn't work if SELinux is

		 * in use.  The following cred dancing somehow works around

		 * it.  See 2ce9738ba ("cgroupfs: use init_cred when

		 * populating new cgroupfs mount") for more details.

	 * We're inside get_sb() and will call lookup_one_len() to create

	 * the root files, which doesn't work if SELinux is in use.  The

	 * following cred dancing somehow works around it.  See 2ce9738ba

	 * ("cgroupfs: use init_cred when populating new cgroupfs mount")

	 * for more details.

	 */

	cred = override_creds(&init_cred);
@@ -1573,16 +1535,17 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, 
	revert_creds(cred);



	/*

		 * There must be no failure case after here, since rebinding

		 * takes care of subsystems' refcounts, which are explicitly

		 * dropped in the failure exit path.

	 * There must be no failure case after here, since rebinding takes

	 * care of subsystems' refcounts, which are explicitly dropped in

	 * the failure exit path.

	 */



	list_add(&root->root_list, &cgroup_roots);

	cgroup_root_count++;



		/* Link the top cgroup in this hierarchy into all

		 * the css_set objects */

	/*

	 * Link the top cgroup in this hierarchy into all the css_set

	 * objects.

	 */

	write_lock(&css_set_lock);

	hash_for_each(css_set_table, i, cset, hlist)

		link_css_set(&tmp_links, cset, root_cgrp);
@@ -1590,6 +1553,67 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, 


	BUG_ON(!list_empty(&root_cgrp->children));

	BUG_ON(root->number_of_cgroups != 1);



	ret = 0;

	goto out_unlock;



rm_base_files:

	cgroup_addrm_files(&root->top_cgroup, cgroup_base_files, false);

	revert_creds(cred);

	cgroup_exit_root_id(root);

out_unlock:

	mutex_unlock(&inode->i_mutex);

	free_cgrp_cset_links(&tmp_links);

	return ret;

}



static struct dentry *cgroup_mount(struct file_system_type *fs_type,

			 int flags, const char *unused_dev_name,

			 void *data)

{

	struct super_block *sb = NULL;

	struct cgroupfs_root *root = NULL;

	struct cgroup_sb_opts opts;

	struct cgroupfs_root *new_root;

	int ret;



	mutex_lock(&cgroup_tree_mutex);

	mutex_lock(&cgroup_mutex);



	/* First find the desired set of subsystems */

	ret = parse_cgroupfs_options(data, &opts);

	if (ret)

		goto out_unlock;



	/*

	 * Allocate a new cgroup root. We may not need it if we're

	 * reusing an existing hierarchy.

	 */

	new_root = cgroup_root_from_opts(&opts);

	if (IS_ERR(new_root)) {

		ret = PTR_ERR(new_root);

		goto out_unlock;

	}

	opts.new_root = new_root;



	/* Locate an existing or new sb for this hierarchy */

	mutex_unlock(&cgroup_mutex);

	mutex_unlock(&cgroup_tree_mutex);

	sb = sget(fs_type, cgroup_test_super, cgroup_set_super, 0, &opts);

	mutex_lock(&cgroup_tree_mutex);

	mutex_lock(&cgroup_mutex);

	if (IS_ERR(sb)) {

		ret = PTR_ERR(sb);

		cgroup_free_root(opts.new_root);

		goto out_unlock;

	}



	root = sb->s_fs_info;

	BUG_ON(!root);

	if (root == opts.new_root) {

		ret = cgroup_setup_root(root);

		if (ret)

			goto out_unlock;

	} else {

		/*

		 * We re-used an existing hierarchy - the new root (if
@@ -1609,22 +1633,13 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, 
	}



	ret = 0;

	goto out_unlock;



rm_base_files:

	cgroup_addrm_files(&root->top_cgroup, cgroup_base_files, false);

	revert_creds(cred);

	cgroup_exit_root_id(root);

out_unlock:

	mutex_unlock(&cgroup_mutex);

	mutex_unlock(&cgroup_tree_mutex);

	if (inode)

		mutex_unlock(&inode->i_mutex);



	if (ret && !IS_ERR_OR_NULL(sb))

		deactivate_locked_super(sb);



	free_cgrp_cset_links(&tmp_links);

	kfree(opts.release_agent);

	kfree(opts.name);