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cgroup: refactor mount path and clearly distinguish v1 and v2 paths

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While sharing some mechanisms, the mount paths of v1 and v2 are
substantially different.  Their implementations were mixed in
cgroup_mount().  This patch splits them out so that they're easier to
follow and organize.

This patch causes one functional change - the WARN_ON(new_sb) gets
lost.  This is because the actual mounting gets moved to
cgroup_do_mount() and thus @new_sb is no longer accessible by default
to cgroup1_mount().  While we can add it as an explicit out parameter
to cgroup_do_mount(), this part of code hasn't changed and the warning
hasn't triggered for quite a while.  Dropping it should be fine.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Acked-by: Zefan Li <lizefan@huawei.com>
This commit is contained in:
Tejun Heo 2016-12-27 14:49:07 -05:00
parent 0a268dbd79
commit 633feee310
1 changed files with 83 additions and 65 deletions
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148
kernel/cgroup/cgroup.c
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@ -1989,48 +1989,55 @@ static int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask)
return ret;
}
static struct dentry *cgroup_mount(struct file_system_type *fs_type,
int flags, const char *unused_dev_name,
void *data)
static struct dentry *cgroup_do_mount(struct file_system_type *fs_type,
int flags, struct cgroup_root *root,
unsigned long magic,
struct cgroup_namespace *ns)
{
bool is_v2 = fs_type == &cgroup2_fs_type;
struct super_block *pinned_sb = NULL;
struct cgroup_namespace *ns = current->nsproxy->cgroup_ns;
struct cgroup_subsys *ss;
struct cgroup_root *root;
struct cgroup_sb_opts opts;
struct dentry *dentry;
int ret;
int i;
bool new_sb;
get_cgroup_ns(ns);
/* Check if the caller has permission to mount. */
if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN)) {
put_cgroup_ns(ns);
return ERR_PTR(-EPERM);
}
dentry = kernfs_mount(fs_type, flags, root->kf_root, magic, &new_sb);
/*
* The first time anyone tries to mount a cgroup, enable the list
* linking each css_set to its tasks and fix up all existing tasks.
* In non-init cgroup namespace, instead of root cgroup's dentry,
* we return the dentry corresponding to the cgroupns->root_cgrp.
*/
if (!use_task_css_set_links)
cgroup_enable_task_cg_lists();
if (!IS_ERR(dentry) && ns != &init_cgroup_ns) {
struct dentry *nsdentry;
struct cgroup *cgrp;
if (is_v2) {
if (data) {
pr_err("cgroup2: unknown option \"%s\"\n", (char *)data);
put_cgroup_ns(ns);
return ERR_PTR(-EINVAL);
}
cgrp_dfl_visible = true;
root = &cgrp_dfl_root;
cgroup_get(&root->cgrp);
goto out_mount;
mutex_lock(&cgroup_mutex);
spin_lock_irq(&css_set_lock);
cgrp = cset_cgroup_from_root(ns->root_cset, root);
spin_unlock_irq(&css_set_lock);
mutex_unlock(&cgroup_mutex);
nsdentry = kernfs_node_dentry(cgrp->kn, dentry->d_sb);
dput(dentry);
dentry = nsdentry;
}
if (IS_ERR(dentry) || !new_sb)
cgroup_put(&root->cgrp);
return dentry;
}
static struct dentry *cgroup1_mount(struct file_system_type *fs_type,
int flags, void *data,
unsigned long magic,
struct cgroup_namespace *ns)
{
struct super_block *pinned_sb = NULL;
struct cgroup_sb_opts opts;
struct cgroup_root *root;
struct cgroup_subsys *ss;
struct dentry *dentry;
int i, ret;
cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);
/* First find the desired set of subsystems */
@ -2152,47 +2159,58 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
kfree(opts.release_agent);
kfree(opts.name);
if (ret) {
put_cgroup_ns(ns);
if (ret)
return ERR_PTR(ret);
}
out_mount:
dentry = kernfs_mount(fs_type, flags, root->kf_root,
is_v2 ? CGROUP2_SUPER_MAGIC : CGROUP_SUPER_MAGIC,
&new_sb);
/*
* In non-init cgroup namespace, instead of root cgroup's
* dentry, we return the dentry corresponding to the
* cgroupns->root_cgrp.
*/
if (!IS_ERR(dentry) && ns != &init_cgroup_ns) {
struct dentry *nsdentry;
struct cgroup *cgrp;
mutex_lock(&cgroup_mutex);
spin_lock_irq(&css_set_lock);
cgrp = cset_cgroup_from_root(ns->root_cset, root);
spin_unlock_irq(&css_set_lock);
mutex_unlock(&cgroup_mutex);
nsdentry = kernfs_node_dentry(cgrp->kn, dentry->d_sb);
dput(dentry);
dentry = nsdentry;
}
if (IS_ERR(dentry) || !new_sb)
cgroup_put(&root->cgrp);
dentry = cgroup_do_mount(&cgroup_fs_type, flags, root,
CGROUP_SUPER_MAGIC, ns);
/*
* If @pinned_sb, we're reusing an existing root and holding an
* extra ref on its sb. Mount is complete. Put the extra ref.
*/
if (pinned_sb) {
WARN_ON(new_sb);
if (pinned_sb)
deactivate_super(pinned_sb);
return dentry;
}
static struct dentry *cgroup_mount(struct file_system_type *fs_type,
int flags, const char *unused_dev_name,
void *data)
{
struct cgroup_namespace *ns = current->nsproxy->cgroup_ns;
struct dentry *dentry;
get_cgroup_ns(ns);
/* Check if the caller has permission to mount. */
if (!ns_capable(ns->user_ns, CAP_SYS_ADMIN)) {
put_cgroup_ns(ns);
return ERR_PTR(-EPERM);
}
/*
* The first time anyone tries to mount a cgroup, enable the list
* linking each css_set to its tasks and fix up all existing tasks.
*/
if (!use_task_css_set_links)
cgroup_enable_task_cg_lists();
if (fs_type == &cgroup2_fs_type) {
if (data) {
pr_err("cgroup2: unknown option \"%s\"\n", (char *)data);
put_cgroup_ns(ns);
return ERR_PTR(-EINVAL);
}
cgrp_dfl_visible = true;
cgroup_get(&cgrp_dfl_root.cgrp);
dentry = cgroup_do_mount(&cgroup2_fs_type, flags, &cgrp_dfl_root,
CGROUP2_SUPER_MAGIC, ns);
} else {
dentry = cgroup1_mount(&cgroup_fs_type, flags, data,
CGROUP_SUPER_MAGIC, ns);
}
put_cgroup_ns(ns);