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/include/linux/cgroup.h b/include/linux/cgroup.h
index 06f577764414bba629be18c698fc51a821acd09c..52327787191333681182de24afe83049a6ee8186 100644 (file)
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -516,18 +516,14 @@ static inline ino_t cgroup_ino(struct cgroup *cgrp)
                return 0;
 }
 
-static inline struct cgroup_subsys_state *seq_css(struct seq_file *seq)
-{
-       struct cgroup_open_file *of = seq->private;
-       return of->cfe->css;
-}
-
 static inline struct cftype *seq_cft(struct seq_file *seq)
 {
        struct cgroup_open_file *of = seq->private;
        return of->cfe->type;
 }
 
+struct cgroup_subsys_state *seq_css(struct seq_file *seq);
+
 int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
 int cgroup_rm_cftypes(struct cftype *cfts);
 

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 11f7a05e791ee413ec250841b7dea89947bcae79..9e9e8fd632d8a983ae4e452d3d1fcca4a25177ad 100644 (file)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -169,6 +169,7 @@ static int need_forkexit_callback __read_mostly;
 
 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 @@ static inline bool cgroup_is_dead(const struct cgroup *cgrp)
        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 @@ static struct css_set *find_css_set(struct css_set *old_cset,
        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 @@ static void cgroup_free_fn(struct work_struct *work)
        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 @@ static void cgroup_free_rcu(struct rcu_head *head)
        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 @@ static void cgroup_diput(struct dentry *dentry, struct inode *inode)
        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 @@ static int cgroup_cfts_commit(struct cftype *cfts, bool is_add)
        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 @@ static int cgroup_cfts_commit(struct cftype *cfts, bool is_add)
                        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 @@ static int cgroup_cfts_commit(struct cftype *cfts, bool is_add)
                        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 int cgroup_write_notify_on_release(struct cgroup_subsys_state *css,
  */
 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 @@ static int create_css(struct cgroup *cgrp, struct cgroup_subsys *ss)
        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 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
         * 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 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
        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 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
 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 int cgroup_destroy_locked(struct cgroup *cgrp)
 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 @@ static void cgroup_destroy_css_killed(struct cgroup *cgrp)
        /* 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 @@ static int current_css_set_cg_links_read(struct seq_file *seq, void *v)
        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 != cgroup_dummy_top)
+                       name = cgroup_name(c);
 
-               if (c->dentry)
-                       name = c->dentry->d_name.name;
-               else
-                       name = "?";
                seq_printf(seq, "Root %d group %s\n",
                           c->root->hierarchy_id, name);
        }