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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: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
This commit is contained in:
Tejun Heo 2014-02-13 06:58:38 -05:00
parent d3ba07c3aa
commit 3558557305
2 changed files with 4 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/linux/cgroup.h
View File

@ -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 */
};
/*

28
kernel/cgroup.c
View File

@ -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);