cgroup: misc preps for kernfs conversion
* Un-inline seq_css(). After kernfs conversion, the function will
need to dereference internal data structures.
* Add cgroup_get/put_root() and replace direct super_block->s_active
manipulatinos with them. These will be converted to kernfs_root
refcnting.
* Add cgroup_get/put() and replace dget/put() on cgrp->dentry with
them. These will be converted to kernfs refcnting.
* Update current_css_set_cg_links_read() to use cgroup_name() instead
of reaching into the dentry name. The end result is the same.
These changes don't make functional differences but will make
transition to kernfs easier.
v2: Rebased on top of 0ab02ca8f887 ("cgroup: protect modifications to
cgroup_idr with cgroup_mutex").
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 11f7a05..9e9e8fd 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -169,6 +169,7 @@
static struct cftype cgroup_base_files[];
+static void cgroup_put(struct cgroup *cgrp);
static void cgroup_destroy_css_killed(struct cgroup *cgrp);
static int cgroup_destroy_locked(struct cgroup *cgrp);
static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[],
@@ -204,6 +205,13 @@
return test_bit(CGRP_DEAD, &cgrp->flags);
}
+struct cgroup_subsys_state *seq_css(struct seq_file *seq)
+{
+ struct cgroup_open_file *of = seq->private;
+ return of->cfe->css;
+}
+EXPORT_SYMBOL_GPL(seq_css);
+
/**
* cgroup_is_descendant - test ancestry
* @cgrp: the cgroup to be tested
@@ -682,6 +690,16 @@
return cset;
}
+static void cgroup_get_root(struct cgroupfs_root *root)
+{
+ atomic_inc(&root->sb->s_active);
+}
+
+static void cgroup_put_root(struct cgroupfs_root *root)
+{
+ deactivate_super(root->sb);
+}
+
/*
* Return the cgroup for "task" from the given hierarchy. Must be
* called with cgroup_mutex held.
@@ -837,18 +855,14 @@
mutex_unlock(&cgroup_mutex);
/*
- * We get a ref to the parent's dentry, and put the ref when
- * this cgroup is being freed, so it's guaranteed that the
- * parent won't be destroyed before its children.
+ * We get a ref to the parent, and put the ref when this cgroup is
+ * being freed, so it's guaranteed that the parent won't be
+ * destroyed before its children.
*/
- dput(cgrp->parent->dentry);
+ cgroup_put(cgrp->parent);
- /*
- * Drop the active superblock reference that we took when we
- * created the cgroup. This will free cgrp->root, if we are
- * holding the last reference to @sb.
- */
- deactivate_super(cgrp->root->sb);
+ /* put the root reference that we took when we created the cgroup */
+ cgroup_put_root(cgrp->root);
cgroup_pidlist_destroy_all(cgrp);
@@ -866,6 +880,11 @@
queue_work(cgroup_destroy_wq, &cgrp->destroy_work);
}
+static void cgroup_get(struct cgroup *cgrp)
+{
+ dget(cgrp->dentry);
+}
+
static void cgroup_diput(struct dentry *dentry, struct inode *inode)
{
/* is dentry a directory ? if so, kfree() associated cgroup */
@@ -899,6 +918,11 @@
iput(inode);
}
+static void cgroup_put(struct cgroup *cgrp)
+{
+ dput(cgrp->dentry);
+}
+
static void remove_dir(struct dentry *d)
{
struct dentry *parent = dget(d->d_parent);
@@ -2724,7 +2748,7 @@
struct cgroup_subsys *ss = cfts[0].ss;
struct cgroup *root = &ss->root->top_cgroup;
struct super_block *sb = ss->root->sb;
- struct dentry *prev = NULL;
+ struct cgroup *prev = NULL;
struct inode *inode;
struct cgroup_subsys_state *css;
u64 update_before;
@@ -2754,9 +2778,10 @@
continue;
inode = cgrp->dentry->d_inode;
- dget(cgrp->dentry);
- dput(prev);
- prev = cgrp->dentry;
+ cgroup_get(cgrp);
+ if (prev)
+ cgroup_put(prev);
+ prev = cgrp;
mutex_unlock(&cgroup_tree_mutex);
mutex_lock(&inode->i_mutex);
@@ -2768,8 +2793,8 @@
break;
}
mutex_unlock(&cgroup_tree_mutex);
- dput(prev);
- deactivate_super(sb);
+ cgroup_put(prev);
+ cgroup_put_root(ss->root);
return ret;
}
@@ -3863,11 +3888,9 @@
*/
static void cgroup_dput(struct cgroup *cgrp)
{
- struct super_block *sb = cgrp->root->sb;
-
- atomic_inc(&sb->s_active);
- dput(cgrp->dentry);
- deactivate_super(sb);
+ cgroup_get_root(cgrp->root);
+ cgroup_put(cgrp);
+ cgroup_put_root(cgrp->root);
}
static u64 cgroup_clone_children_read(struct cgroup_subsys_state *css,
@@ -4118,7 +4141,7 @@
if (err)
goto err_free;
- dget(cgrp->dentry);
+ cgroup_get(cgrp);
css_get(css->parent);
if (ss->broken_hierarchy && !ss->warned_broken_hierarchy &&
@@ -4197,7 +4220,7 @@
* can be done outside cgroup_mutex, since the sb can't
* disappear while someone has an open control file on the
* fs */
- atomic_inc(&sb->s_active);
+ cgroup_get_root(root);
init_cgroup_housekeeping(cgrp);
@@ -4231,7 +4254,7 @@
root->number_of_cgroups++;
/* hold a ref to the parent's dentry */
- dget(parent->dentry);
+ cgroup_get(parent);
/*
* @cgrp is now fully operational. If something fails after this
@@ -4261,7 +4284,7 @@
err_free_id:
idr_remove(&root->cgroup_idr, cgrp->id);
/* Release the reference count that we took on the superblock */
- deactivate_super(sb);
+ cgroup_put_root(root);
err_unlock:
mutex_unlock(&cgroup_mutex);
err_unlock_tree:
@@ -4493,7 +4516,6 @@
static void cgroup_destroy_css_killed(struct cgroup *cgrp)
{
struct cgroup *parent = cgrp->parent;
- struct dentry *d = cgrp->dentry;
lockdep_assert_held(&cgroup_tree_mutex);
lockdep_assert_held(&cgroup_mutex);
@@ -4501,7 +4523,7 @@
/* delete this cgroup from parent->children */
list_del_rcu(&cgrp->sibling);
- dput(d);
+ cgroup_put(cgrp);
set_bit(CGRP_RELEASABLE, &parent->flags);
check_for_release(parent);
@@ -5161,12 +5183,11 @@
cset = rcu_dereference(current->cgroups);
list_for_each_entry(link, &cset->cgrp_links, cgrp_link) {
struct cgroup *c = link->cgrp;
- const char *name;
+ const char *name = "?";
- if (c->dentry)
- name = c->dentry->d_name.name;
- else
- name = "?";
+ if (c != cgroup_dummy_top)
+ name = cgroup_name(c);
+
seq_printf(seq, "Root %d group %s\n",
c->root->hierarchy_id, name);
}