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Date: Tue, 20 Dec 2016 16:08:23 -0500
From: Tejun Heo <tj@...nel.org>
To: lizefan@...wei.com, hannes@...xchg.org
Cc: linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
kernel-team@...com, Tejun Heo <tj@...nel.org>
Subject: [PATCH 4/8] cgroup: refactor mount path and clearly distinguish v1 and v2 paths
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@...nel.org>
---
kernel/cgroup/cgroup.c | 140 ++++++++++++++++++++++++++++---------------------
1 file changed, 79 insertions(+), 61 deletions(-)
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index cb0d29e..6225c4b 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -1991,48 +1991,55 @@ 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 */
@@ -2154,47 +2161,58 @@ 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);
+
+ dentry = cgroup_do_mount(&cgroup_fs_type, flags, root,
+ CGROUP_SUPER_MAGIC, ns);
/*
- * In non-init cgroup namespace, instead of root cgroup's
- * dentry, we return the dentry corresponding to the
- * cgroupns->root_cgrp.
+ * 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 (!IS_ERR(dentry) && ns != &init_cgroup_ns) {
- struct dentry *nsdentry;
- struct cgroup *cgrp;
+ if (pinned_sb)
+ deactivate_super(pinned_sb);
- mutex_lock(&cgroup_mutex);
- spin_lock_irq(&css_set_lock);
+ return dentry;
+}
- cgrp = cset_cgroup_from_root(ns->root_cset, root);
+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;
- spin_unlock_irq(&css_set_lock);
- mutex_unlock(&cgroup_mutex);
+ get_cgroup_ns(ns);
- nsdentry = kernfs_node_dentry(cgrp->kn, dentry->d_sb);
- dput(dentry);
- dentry = nsdentry;
+ /* 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);
}
- if (IS_ERR(dentry) || !new_sb)
- cgroup_put(&root->cgrp);
-
/*
- * If @pinned_sb, we're reusing an existing root and holding an
- * extra ref on its sb. Mount is complete. Put the extra ref.
+ * 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 (pinned_sb) {
- WARN_ON(new_sb);
- deactivate_super(pinned_sb);
+ 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);
--
2.9.3
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