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Subject[PATCH v2 07/14] cgroup: reorganize css init / exit paths
css (cgroup_subsys_state) lifetime management is about to be
restructured. In prepartion, make the following mostly trivial
changes.

* init_cgroup_css() is renamed to init_css() so that it's consistent
with other css handling functions.

* alloc_css_id(), online_css() and offline_css() updated to take @css
instead of cgroups and subsys IDs.

This patch doesn't make any functional changes.

v2: v1 merged two for_each_root_subsys() loops in cgroup_create() but
Li Zefan pointed out that it breaks error path. Dropped.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Li Zefan <lizefan@huawei.com>
---
This causes some offset warnings for later patches but nothing patch
can't handle. The git branch is updated accordingly.

Thanks.

kernel/cgroup.c | 50 +++++++++++++++++++++++---------------------------
1 file changed, 23 insertions(+), 27 deletions(-)

--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -838,8 +838,7 @@ static struct backing_dev_info cgroup_ba
.capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
};

-static int alloc_css_id(struct cgroup_subsys *ss,
- struct cgroup *parent, struct cgroup *child);
+static int alloc_css_id(struct cgroup_subsys_state *child_css);

static struct inode *cgroup_new_inode(umode_t mode, struct super_block *sb)
{
@@ -4308,9 +4307,8 @@ static void css_release(struct percpu_re
schedule_work(&css->destroy_work);
}

-static void init_cgroup_css(struct cgroup_subsys_state *css,
- struct cgroup_subsys *ss,
- struct cgroup *cgrp)
+static void init_css(struct cgroup_subsys_state *css, struct cgroup_subsys *ss,
+ struct cgroup *cgrp)
{
css->cgroup = cgrp;
css->ss = ss;
@@ -4327,9 +4325,9 @@ static void init_cgroup_css(struct cgrou
}

/* invoke ->css_online() on a new CSS and mark it online if successful */
-static int online_css(struct cgroup_subsys *ss, struct cgroup *cgrp)
+static int online_css(struct cgroup_subsys_state *css)
{
- struct cgroup_subsys_state *css = cgroup_css(cgrp, ss->subsys_id);
+ struct cgroup_subsys *ss = css->ss;
int ret = 0;

lockdep_assert_held(&cgroup_mutex);
@@ -4342,9 +4340,9 @@ static int online_css(struct cgroup_subs
}

/* if the CSS is online, invoke ->css_offline() on it and mark it offline */
-static void offline_css(struct cgroup_subsys *ss, struct cgroup *cgrp)
+static void offline_css(struct cgroup_subsys_state *css)
{
- struct cgroup_subsys_state *css = cgroup_css(cgrp, ss->subsys_id);
+ struct cgroup_subsys *ss = css->ss;

lockdep_assert_held(&cgroup_mutex);

@@ -4442,10 +4440,10 @@ static long cgroup_create(struct cgroup
goto err_free_all;
}

- init_cgroup_css(css, ss, cgrp);
+ init_css(css, ss, cgrp);

if (ss->use_id) {
- err = alloc_css_id(ss, parent, cgrp);
+ err = alloc_css_id(css);
if (err)
goto err_free_all;
}
@@ -4480,7 +4478,9 @@ static long cgroup_create(struct cgroup

/* creation succeeded, notify subsystems */
for_each_root_subsys(root, ss) {
- err = online_css(ss, cgrp);
+ struct cgroup_subsys_state *css = cgroup_css(cgrp, ss->subsys_id);
+
+ err = online_css(css);
if (err)
goto err_destroy;

@@ -4700,7 +4700,7 @@ static void cgroup_offline_fn(struct wor
* initate destruction.
*/
for_each_root_subsys(cgrp->root, ss)
- offline_css(ss, cgrp);
+ offline_css(cgroup_css(cgrp, ss->subsys_id));

/*
* Put the css refs from cgroup_destroy_locked(). Each css holds
@@ -4778,7 +4778,7 @@ static void __init cgroup_init_subsys(st
css = ss->css_alloc(cgroup_css(cgroup_dummy_top, ss->subsys_id));
/* We don't handle early failures gracefully */
BUG_ON(IS_ERR(css));
- init_cgroup_css(css, ss, cgroup_dummy_top);
+ init_css(css, ss, cgroup_dummy_top);

/* Update the init_css_set to contain a subsys
* pointer to this state - since the subsystem is
@@ -4793,7 +4793,7 @@ static void __init cgroup_init_subsys(st
* need to invoke fork callbacks here. */
BUG_ON(!list_empty(&init_task.tasks));

- BUG_ON(online_css(ss, cgroup_dummy_top));
+ BUG_ON(online_css(cgroup_css(cgroup_dummy_top, ss->subsys_id)));

mutex_unlock(&cgroup_mutex);

@@ -4866,8 +4866,8 @@ int __init_or_module cgroup_load_subsys(
ss->root = &cgroup_dummy_root;

/* our new subsystem will be attached to the dummy hierarchy. */
- init_cgroup_css(css, ss, cgroup_dummy_top);
- /* init_idr must be after init_cgroup_css because it sets css->id. */
+ init_css(css, ss, cgroup_dummy_top);
+ /* init_idr must be after init_css() because it sets css->id. */
if (ss->use_id) {
ret = cgroup_init_idr(ss, css);
if (ret)
@@ -4897,7 +4897,7 @@ int __init_or_module cgroup_load_subsys(
}
write_unlock(&css_set_lock);

- ret = online_css(ss, cgroup_dummy_top);
+ ret = online_css(cgroup_css(cgroup_dummy_top, ss->subsys_id));
if (ret)
goto err_unload;

@@ -4936,7 +4936,7 @@ void cgroup_unload_subsys(struct cgroup_

mutex_lock(&cgroup_mutex);

- offline_css(ss, cgroup_dummy_top);
+ offline_css(cgroup_css(cgroup_dummy_top, ss->subsys_id));

if (ss->use_id)
idr_destroy(&ss->idr);
@@ -5588,20 +5588,16 @@ static int __init_or_module cgroup_init_
return 0;
}

-static int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *parent,
- struct cgroup *child)
+static int alloc_css_id(struct cgroup_subsys_state *child_css)
{
- int subsys_id, i, depth = 0;
- struct cgroup_subsys_state *parent_css, *child_css;
+ struct cgroup_subsys_state *parent_css = css_parent(child_css);
struct css_id *child_id, *parent_id;
+ int i, depth;

- subsys_id = ss->subsys_id;
- parent_css = cgroup_css(parent, subsys_id);
- child_css = cgroup_css(child, subsys_id);
parent_id = rcu_dereference_protected(parent_css->id, true);
depth = parent_id->depth + 1;

- child_id = get_new_cssid(ss, depth);
+ child_id = get_new_cssid(child_css->ss, depth);
if (IS_ERR(child_id))
return PTR_ERR(child_id);


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