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Commit 633feee3 authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: refactor mount path and clearly distinguish v1 and v2 paths 



While sharing some mechanisms, the mount paths of v1 and v2 are
substantially different.  Their implementations were mixed in
cgroup_mount().  This patch splits them out so that they're easier to
follow and organize.

This patch causes one functional change - the WARN_ON(new_sb) gets
lost.  This is because the actual mounting gets moved to
cgroup_do_mount() and thus @new_sb is no longer accessible by default
to cgroup1_mount().  While we can add it as an explicit out parameter
to cgroup_do_mount(), this part of code hasn't changed and the warning
hasn't triggered for quite a while.  Dropping it should be fine.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarAcked-by: Zefan Li <lizefan@huawei.com>
parent 0a268dbd

kernel/cgroup/cgroup.c

+79 −61
Original line number Diff line number Diff line
@@ -1989,48 +1989,55 @@ static int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask) 
	return ret;

}



static struct dentry *cgroup_mount(struct file_system_type *fs_type,

			 int flags, const char *unused_dev_name,

			 void *data)

static struct dentry *cgroup_do_mount(struct file_system_type *fs_type,

				      int flags, struct cgroup_root *root,

				      unsigned long magic,

				      struct cgroup_namespace *ns)

{

	bool is_v2 = fs_type == &cgroup2_fs_type;

	struct super_block *pinned_sb = NULL;

	struct cgroup_namespace *ns = current->nsproxy->cgroup_ns;

	struct cgroup_subsys *ss;

	struct cgroup_root *root;

	struct cgroup_sb_opts opts;

	struct dentry *dentry;

	int ret;

	int i;

	bool new_sb;



	get_cgroup_ns(ns);



	/* Check if the caller has permission to mount. */

	if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN)) {

		put_cgroup_ns(ns);

		return ERR_PTR(-EPERM);

	}

	dentry = kernfs_mount(fs_type, flags, root->kf_root, magic, &new_sb);



	/*

	 * The first time anyone tries to mount a cgroup, enable the list

	 * linking each css_set to its tasks and fix up all existing tasks.

	 * In non-init cgroup namespace, instead of root cgroup's dentry,

	 * we return the dentry corresponding to the cgroupns->root_cgrp.

	 */

	if (!use_task_css_set_links)

		cgroup_enable_task_cg_lists();

	if (!IS_ERR(dentry) && ns != &init_cgroup_ns) {

		struct dentry *nsdentry;

		struct cgroup *cgrp;



	if (is_v2) {

		if (data) {

			pr_err("cgroup2: unknown option \"%s\"\n", (char *)data);

			put_cgroup_ns(ns);

			return ERR_PTR(-EINVAL);

		mutex_lock(&cgroup_mutex);

		spin_lock_irq(&css_set_lock);



		cgrp = cset_cgroup_from_root(ns->root_cset, root);



		spin_unlock_irq(&css_set_lock);

		mutex_unlock(&cgroup_mutex);



		nsdentry = kernfs_node_dentry(cgrp->kn, dentry->d_sb);

		dput(dentry);

		dentry = nsdentry;

	}

		cgrp_dfl_visible = true;

		root = &cgrp_dfl_root;

		cgroup_get(&root->cgrp);

		goto out_mount;



	if (IS_ERR(dentry) || !new_sb)

		cgroup_put(&root->cgrp);



	return dentry;

}



static struct dentry *cgroup1_mount(struct file_system_type *fs_type,

				    int flags, void *data,

				    unsigned long magic,

				    struct cgroup_namespace *ns)

{

	struct super_block *pinned_sb = NULL;

	struct cgroup_sb_opts opts;

	struct cgroup_root *root;

	struct cgroup_subsys *ss;

	struct dentry *dentry;

	int i, ret;



	cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);



	/* First find the desired set of subsystems */
@@ -2152,47 +2159,58 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, 
	kfree(opts.release_agent);

	kfree(opts.name);



	if (ret) {

		put_cgroup_ns(ns);

	if (ret)

		return ERR_PTR(ret);

	}

out_mount:

	dentry = kernfs_mount(fs_type, flags, root->kf_root,

			      is_v2 ? CGROUP2_SUPER_MAGIC : CGROUP_SUPER_MAGIC,

			      &new_sb);



	dentry = cgroup_do_mount(&cgroup_fs_type, flags, root,

				 CGROUP_SUPER_MAGIC, ns);



	/*

	 * In non-init cgroup namespace, instead of root cgroup's

	 * dentry, we return the dentry corresponding to the

	 * cgroupns->root_cgrp.

	 * If @pinned_sb, we're reusing an existing root and holding an

	 * extra ref on its sb.  Mount is complete.  Put the extra ref.

	 */

	if (!IS_ERR(dentry) && ns != &init_cgroup_ns) {

		struct dentry *nsdentry;

		struct cgroup *cgrp;

	if (pinned_sb)

		deactivate_super(pinned_sb);



		mutex_lock(&cgroup_mutex);

		spin_lock_irq(&css_set_lock);

	return dentry;

}



		cgrp = cset_cgroup_from_root(ns->root_cset, root);

static struct dentry *cgroup_mount(struct file_system_type *fs_type,

			 int flags, const char *unused_dev_name,

			 void *data)

{

	struct cgroup_namespace *ns = current->nsproxy->cgroup_ns;

	struct dentry *dentry;



		spin_unlock_irq(&css_set_lock);

		mutex_unlock(&cgroup_mutex);

	get_cgroup_ns(ns);



		nsdentry = kernfs_node_dentry(cgrp->kn, dentry->d_sb);

		dput(dentry);

		dentry = nsdentry;

	/* Check if the caller has permission to mount. */

	if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN)) {

		put_cgroup_ns(ns);

		return ERR_PTR(-EPERM);

	}



	if (IS_ERR(dentry) || !new_sb)

		cgroup_put(&root->cgrp);



	/*

	 * If @pinned_sb, we're reusing an existing root and holding an

	 * extra ref on its sb.  Mount is complete.  Put the extra ref.

	 * The first time anyone tries to mount a cgroup, enable the list

	 * linking each css_set to its tasks and fix up all existing tasks.

	 */

	if (pinned_sb) {

		WARN_ON(new_sb);

		deactivate_super(pinned_sb);

	if (!use_task_css_set_links)

		cgroup_enable_task_cg_lists();



	if (fs_type == &cgroup2_fs_type) {

		if (data) {

			pr_err("cgroup2: unknown option \"%s\"\n", (char *)data);

			put_cgroup_ns(ns);

			return ERR_PTR(-EINVAL);

		}

		cgrp_dfl_visible = true;

		cgroup_get(&cgrp_dfl_root.cgrp);



		dentry = cgroup_do_mount(&cgroup2_fs_type, flags, &cgrp_dfl_root,

					 CGROUP2_SUPER_MAGIC, ns);

	} else {

		dentry = cgroup1_mount(&cgroup_fs_type, flags, data,

				       CGROUP_SUPER_MAGIC, ns);

	}



	put_cgroup_ns(ns);