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Commit 4e96ee8e authored by Li Zefan's avatar Li Zefan Committed by Tejun Heo
Browse files

cgroup: convert cgroup_ida to cgroup_idr 



This enables us to lookup a cgroup by its id.

v4:
- add a comment for idr_remove() in cgroup_offline_fn().

v3:
- on success, idr_alloc() returns the id but not 0, so fix the BUG_ON()
  in cgroup_init().
- pass the right value to idr_alloc() so that the id for dummy cgroup is 0.

Signed-off-by: default avatarLi Zefan <lizefan@huawei.com>
Reviewed-by: default avatarMichal Hocko <mhocko@suse.cz>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 6f4b7e63

include/linux/cgroup.h

+2 −2
Original line number Diff line number Diff line
@@ -161,7 +161,7 @@ struct cgroup_name { 
struct cgroup {

	unsigned long flags;		/* "unsigned long" so bitops work */



	int id;				/* ida allocated in-hierarchy ID */

	int id;				/* idr allocated in-hierarchy ID */



	/*

	 * We link our 'sibling' struct into our parent's 'children'.
@@ -322,7 +322,7 @@ struct cgroupfs_root { 
	unsigned long flags;



	/* IDs for cgroups in this hierarchy */

	struct ida cgroup_ida;

	struct idr cgroup_idr;



	/* The path to use for release notifications. */

	char release_agent_path[PATH_MAX];

kernel/cgroup.c

+27 −6
Original line number Diff line number Diff line
@@ -866,8 +866,6 @@ static void cgroup_free_fn(struct work_struct *work) 
	 */

	dput(cgrp->parent->dentry);



	ida_simple_remove(&cgrp->root->cgroup_ida, cgrp->id);



	/*

	 * Drop the active superblock reference that we took when we

	 * created the cgroup. This will free cgrp->root, if we are
@@ -1379,6 +1377,7 @@ static void init_cgroup_root(struct cgroupfs_root *root) 
	cgrp->root = root;

	RCU_INIT_POINTER(cgrp->name, &root_cgroup_name);

	init_cgroup_housekeeping(cgrp);

	idr_init(&root->cgroup_idr);

}



static int cgroup_init_root_id(struct cgroupfs_root *root, int start, int end)
@@ -1451,7 +1450,6 @@ static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts) 
	 */

	root->subsys_mask = opts->subsys_mask;

	root->flags = opts->flags;

	ida_init(&root->cgroup_ida);

	if (opts->release_agent)

		strcpy(root->release_agent_path, opts->release_agent);

	if (opts->name)
@@ -1467,7 +1465,7 @@ static void cgroup_free_root(struct cgroupfs_root *root) 
		/* hierarhcy ID shoulid already have been released */

		WARN_ON_ONCE(root->hierarchy_id);



		ida_destroy(&root->cgroup_ida);

		idr_destroy(&root->cgroup_idr);

		kfree(root);

	}

}
@@ -1582,6 +1580,11 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, 
		mutex_lock(&cgroup_mutex);

		mutex_lock(&cgroup_root_mutex);



		root_cgrp->id = idr_alloc(&root->cgroup_idr, root_cgrp,

					   0, 1, GFP_KERNEL);

		if (root_cgrp->id < 0)

			goto unlock_drop;



		/* Check for name clashes with existing mounts */

		ret = -EBUSY;

		if (strlen(root->name))
@@ -4253,7 +4256,11 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry, 
		goto err_free_cgrp;

	rcu_assign_pointer(cgrp->name, name);



	cgrp->id = ida_simple_get(&root->cgroup_ida, 1, 0, GFP_KERNEL);

	/*

	 * Temporarily set the pointer to NULL, so idr_find() won't return

	 * a half-baked cgroup.

	 */

	cgrp->id = idr_alloc(&root->cgroup_idr, NULL, 1, 0, GFP_KERNEL);

	if (cgrp->id < 0)

		goto err_free_name;
@@ -4351,6 +4358,8 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry, 
		}

	}



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



	err = cgroup_addrm_files(cgrp, NULL, cgroup_base_files, true);

	if (err)

		goto err_destroy;
@@ -4377,7 +4386,7 @@ err_free_all: 
	/* Release the reference count that we took on the superblock */

	deactivate_super(sb);

err_free_id:

	ida_simple_remove(&root->cgroup_ida, cgrp->id);

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

err_free_name:

	kfree(rcu_dereference_raw(cgrp->name));

err_free_cgrp:
@@ -4570,6 +4579,14 @@ static void cgroup_offline_fn(struct work_struct *work) 
	/* delete this cgroup from parent->children */

	list_del_rcu(&cgrp->sibling);



	/*

	 * We should remove the cgroup object from idr before its grace

	 * period starts, so we won't be looking up a cgroup while the

	 * cgroup is being freed.

	 */

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

	cgrp->id = -1;



	dput(d);



	set_bit(CGRP_RELEASABLE, &parent->flags);
@@ -4895,6 +4912,10 @@ int __init cgroup_init(void) 


	BUG_ON(cgroup_init_root_id(&cgroup_dummy_root, 0, 1));



	err = idr_alloc(&cgroup_dummy_root.cgroup_idr, cgroup_dummy_top,

			0, 1, GFP_KERNEL);

	BUG_ON(err < 0);



	mutex_unlock(&cgroup_root_mutex);

	mutex_unlock(&cgroup_mutex);