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Commit 35585573 authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: drop CGRP_ROOT_SUBSYS_BOUND 



Before kernfs conversion, due to the way super_block lookup works,
cgroup roots were created and made visible before being fully
initialized.  This in turn required a special flag to mark that the
root hasn't been fully initialized so that the destruction path can
tell fully bound ones from half initialized.

That flag is CGRP_ROOT_SUBSYS_BOUND and no longer necessary after the
kernfs conversion as the lookup and creation of new root are atomic
w.r.t. cgroup_mutex.  This patch removes the flag and passes the
requests subsystem mask to cgroup_setup_root() so that it can set the
respective mask bits as subsystems are bound.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
parent d3ba07c3

include/linux/cgroup.h

+0 −2
Original line number Diff line number Diff line
@@ -267,8 +267,6 @@ enum { 


	/* mount options live below bit 16 */

	CGRP_ROOT_OPTION_MASK	= (1 << 16) - 1,



	CGRP_ROOT_SUBSYS_BOUND	= (1 << 16), /* subsystems finished binding */

};



/*

kernel/cgroup.c

+4 −24
Original line number Diff line number Diff line
@@ -733,7 +733,6 @@ static void cgroup_destroy_root(struct cgroupfs_root *root) 
{

	struct cgroup *cgrp = &root->top_cgroup;

	struct cgrp_cset_link *link, *tmp_link;

	int ret;



	mutex_lock(&cgroup_tree_mutex);

	mutex_lock(&cgroup_mutex);
@@ -742,11 +741,7 @@ static void cgroup_destroy_root(struct cgroupfs_root *root) 
	BUG_ON(!list_empty(&cgrp->children));



	/* Rebind all subsystems back to the default hierarchy */

	if (root->flags & CGRP_ROOT_SUBSYS_BOUND) {

		ret = rebind_subsystems(root, 0, root->subsys_mask);

		/* Shouldn't be able to fail ... */

		BUG_ON(ret);

	}

	WARN_ON(rebind_subsystems(root, 0, root->subsys_mask));



	/*

	 * Release all the links from cset_links to this hierarchy's
@@ -1055,13 +1050,7 @@ static int rebind_subsystems(struct cgroupfs_root *root, 
		}

	}



	/*

	 * Mark @root has finished binding subsystems.  @root->subsys_mask

	 * now matches the bound subsystems.

	 */

	root->flags |= CGRP_ROOT_SUBSYS_BOUND;

	kernfs_activate(cgrp->kn);



	return 0;

}
@@ -1353,15 +1342,6 @@ static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts) 


	init_cgroup_root(root);



	/*

	 * We need to set @root->subsys_mask now so that @root can be

	 * matched by cgroup_test_super() before it finishes

	 * initialization; otherwise, competing mounts with the same

	 * options may try to bind the same subsystems instead of waiting

	 * for the first one leading to unexpected mount errors.

	 * SUBSYS_BOUND will be set once actual binding is complete.

	 */

	root->subsys_mask = opts->subsys_mask;

	root->flags = opts->flags;

	if (opts->release_agent)

		strcpy(root->release_agent_path, opts->release_agent);
@@ -1372,7 +1352,7 @@ static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts) 
	return root;

}



static int cgroup_setup_root(struct cgroupfs_root *root)

static int cgroup_setup_root(struct cgroupfs_root *root, unsigned long ss_mask)

{

	LIST_HEAD(tmp_links);

	struct cgroup *root_cgrp = &root->top_cgroup;
@@ -1415,7 +1395,7 @@ static int cgroup_setup_root(struct cgroupfs_root *root) 
	if (ret)

		goto destroy_root;



	ret = rebind_subsystems(root, root->subsys_mask, 0);

	ret = rebind_subsystems(root, ss_mask, 0);

	if (ret)

		goto destroy_root;
@@ -1532,7 +1512,7 @@ retry: 
		goto out_unlock;

	}



	ret = cgroup_setup_root(root);

	ret = cgroup_setup_root(root, opts.subsys_mask);

	if (ret)

		cgroup_free_root(root);