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Subject[PATCH 11/13] cgroup: misc preps for kernfs conversion
Date
* 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.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
include/linux/cgroup.h | 8 ++---
kernel/cgroup.c | 85 +++++++++++++++++++++++++++++++-------------------
2 files changed, 55 insertions(+), 38 deletions(-)

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 15b7839..4740cba 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -514,18 +514,14 @@ 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 e81e4c9..fd4a528 100644
--- 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 */
@@ -897,6 +916,11 @@ 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);
@@ -2722,7 +2746,7 @@ 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;
@@ -2752,9 +2776,10 @@ 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);
@@ -2766,8 +2791,8 @@ 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;
}

@@ -3861,11 +3886,9 @@ 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,
@@ -4116,7 +4139,7 @@ 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 &&
@@ -4195,7 +4218,7 @@ 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);

@@ -4229,7 +4252,7 @@ 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
@@ -4259,7 +4282,7 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
err_unlock:
mutex_unlock(&cgroup_mutex);
/* Release the reference count that we took on the superblock */
- deactivate_super(sb);
+ cgroup_put_root(root);
err_unlock_tree:
mutex_unlock(&cgroup_tree_mutex);
idr_remove(&root->cgroup_idr, cgrp->id);
@@ -4491,7 +4514,6 @@ 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);
@@ -4499,7 +4521,7 @@ 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);
@@ -5159,12 +5181,11 @@ 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);
}
--
1.8.5.3


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