cgroup: remove bind() method from cgroup_subsys.

The bind() method of cgroup_subsys is not used in any of the
controllers (cpuset, freezer, blkio, net_cls, memcg, net_prio,
devices, perf, hugetlb, cpu and cpuacct)

tj: Removed the entry on ->bind() from
    Documentation/cgroups/cgroups.txt.  Also updated a couple
    paragraphs which were suggesting that dynamic re-binding may be
    implemented.  It's not gonna.

Signed-off-by: Rami Rosen <ramirose@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

diff --git a/Documentation/cgroups/cgroups.txt b/Documentation/cgroups/cgroups.txt
index 638bf17..2b51e12 100644 (file)
--- a/Documentation/cgroups/cgroups.txt
+++ b/Documentation/cgroups/cgroups.txt
@@ -211,10 +211,9 @@ 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 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.
+It's not possible to bind a new subsystem to an active cgroup
+hierarchy, or to unbind a subsystem from an active cgroup
+hierarchy.
 
 When a cgroup filesystem is unmounted, if there are any
 child cgroups created below the top-level cgroup, that hierarchy
@@ -382,10 +381,8 @@ 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 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.
+Note that changing the set of subsystems is only supported when the
+hierarchy consists of a single (root) cgroup.
 
 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
@@ -643,13 +640,6 @@ 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
 ===========================

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 515927e..92acf86 100644 (file)
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -483,8 +483,6 @@ 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;

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index ba3e24a..fd38e1c 100644 (file)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1064,16 +1064,12 @@ 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;