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Commit 26d5bbe5 authored by Tejun Heo's avatar Tejun Heo
Browse files

Revert "cgroup: remove bind() method from cgroup_subsys." 



This reverts commit 84cfb6ab.  There
are scheduled changes which make use of the removed callback.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Cc: Rami Rosen <ramirose@gmail.com>
Cc: Li Zefan <lizefan@huawei.com>
parent ef824fa1

Documentation/cgroups/cgroups.txt

+15 −5
Original line number Diff line number Diff line
@@ -211,9 +211,10 @@ matches, and any of the requested subsystems are in use in an existing 
hierarchy, the mount will fail with -EBUSY. Otherwise, a new hierarchy

is activated, associated with the requested subsystems.



It's not possible to bind a new subsystem to an active cgroup

hierarchy, or to unbind a subsystem from an active cgroup

hierarchy.

It's not currently possible to bind a new subsystem to an active

cgroup hierarchy, or to unbind a subsystem from an active cgroup

hierarchy. This may be possible in future, but is fraught with nasty

error-recovery issues.



When a cgroup filesystem is unmounted, if there are any

child cgroups created below the top-level cgroup, that hierarchy
@@ -381,8 +382,10 @@ To Specify a hierarchy's release_agent: 


Note that specifying 'release_agent' more than once will return failure.



Note that changing the set of subsystems is only supported when the

hierarchy consists of a single (root) cgroup.

Note that changing the set of subsystems is currently only supported

when the hierarchy consists of a single (root) cgroup. Supporting

the ability to arbitrarily bind/unbind subsystems from an existing

cgroup hierarchy is intended to be implemented in the future.



Then under /sys/fs/cgroup/rg1 you can find a tree that corresponds to the

tree of the cgroups in the system. For instance, /sys/fs/cgroup/rg1
@@ -640,6 +643,13 @@ void exit(struct task_struct *task) 


Called during task exit.



void bind(struct cgroup *root)

(cgroup_mutex held by caller)



Called when a cgroup subsystem is rebound to a different hierarchy

and root cgroup. Currently this will only involve movement between

the default hierarchy (which never has sub-cgroups) and a hierarchy

that is being created/destroyed (and hence has no sub-cgroups).



4. Extended attribute usage

===========================

include/linux/cgroup.h

+2 −0
Original line number Diff line number Diff line
@@ -484,6 +484,8 @@ struct cgroup_subsys { 
	void (*fork)(struct task_struct *task);

	void (*exit)(struct cgroup *cgrp, struct cgroup *old_cgrp,

		     struct task_struct *task);

	void (*bind)(struct cgroup *root);



	int subsys_id;

	int active;

	int disabled;

kernel/cgroup.c

+4 −0
Original line number Diff line number Diff line
@@ -1091,12 +1091,16 @@ static int rebind_subsystems(struct cgroupfs_root *root, 
			cgrp->subsys[i]->cgroup = cgrp;

			list_move(&ss->sibling, &root->subsys_list);

			ss->root = root;

			if (ss->bind)

				ss->bind(cgrp);

			/* refcount was already taken, and we're keeping it */

		} else if (bit & removed_mask) {

			/* We're removing this subsystem */

			BUG_ON(ss == NULL);

			BUG_ON(cgrp->subsys[i] != dummytop->subsys[i]);

			BUG_ON(cgrp->subsys[i]->cgroup != cgrp);

			if (ss->bind)

				ss->bind(dummytop);

			dummytop->subsys[i]->cgroup = dummytop;

			cgrp->subsys[i] = NULL;

			subsys[i]->root = &rootnode;