leandrof/linux
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

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

Browse Source 
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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

148
kernel/cgroup/cgroup.c
View File

@ -1989,48 +1989,55 @@ out:
return ret; return ret;
} }
static struct dentry *cgroup_mount(struct file_system_type *fs_type, static struct dentry *cgroup_do_mount(struct file_system_type *fs_type,
int flags, const char *unused_dev_name, int flags, struct cgroup_root *root,
void *data) 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; struct dentry *dentry;
int ret;
int i;
bool new_sb; bool new_sb;
get_cgroup_ns(ns); dentry = kernfs_mount(fs_type, flags, root->kf_root, magic, &new_sb);
/* 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 * In non-init cgroup namespace, instead of root cgroup's dentry,
* linking each css_set to its tasks and fix up all existing tasks. * we return the dentry corresponding to the cgroupns->root_cgrp.
*/ */
if (!use_task_css_set_links) if (!IS_ERR(dentry) && ns != &init_cgroup_ns) {
cgroup_enable_task_cg_lists(); struct dentry *nsdentry;
struct cgroup *cgrp;
if (is_v2) { mutex_lock(&cgroup_mutex);
if (data) { spin_lock_irq(&css_set_lock);
pr_err("cgroup2: unknown option \"%s\"\n", (char *)data);
put_cgroup_ns(ns); cgrp = cset_cgroup_from_root(ns->root_cset, root);
return ERR_PTR(-EINVAL);
} spin_unlock_irq(&css_set_lock);
cgrp_dfl_visible = true; mutex_unlock(&cgroup_mutex);
root = &cgrp_dfl_root;
cgroup_get(&root->cgrp); nsdentry = kernfs_node_dentry(cgrp->kn, dentry->d_sb);
goto out_mount; 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); cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);
/* First find the desired set of subsystems */ /* First find the desired set of subsystems */
@ -2152,47 +2159,58 @@ out_free:
kfree(opts.release_agent); kfree(opts.release_agent);
kfree(opts.name); kfree(opts.name);
if (ret) { if (ret)
put_cgroup_ns(ns);
return ERR_PTR(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);
/* dentry = cgroup_do_mount(&cgroup_fs_type, flags, root,
* In non-init cgroup namespace, instead of root cgroup's CGROUP_SUPER_MAGIC, ns);
* 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);
/* /*
* If @pinned_sb, we're reusing an existing root and holding an * If @pinned_sb, we're reusing an existing root and holding an
* extra ref on its sb. Mount is complete. Put the extra ref. * extra ref on its sb. Mount is complete. Put the extra ref.
*/ */
if (pinned_sb) { if (pinned_sb)
WARN_ON(new_sb);
deactivate_super(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); put_cgroup_ns(ns);