[PATCH 04/11] cgroup: use kzalloc() and list_del_init()

From: Tejun Heo
Date: Wed Jun 12 2013 - 17:03:47 EST


There's no point in using kmalloc() and list_del() instead of the
clearing variants for trivial stuff. We can live dangerously
elsewhere. Use kzalloc() and list_del_init() instead and drop 0
inits.

While at it, do trivial code reorganization in cgroup_file_open().

This patch doesn't introduce any functional changes.

Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
---
kernel/cgroup.c | 28 ++++++++++++++--------------
1 file changed, 14 insertions(+), 14 deletions(-)

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 0b5cd0e..585f0a5 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -404,8 +404,8 @@ static void __put_css_set(struct css_set *cset, int taskexit)
list_for_each_entry_safe(link, tmp_link, &cset->cgrp_links, cgrp_link) {
struct cgroup *cgrp = link->cgrp;

- list_del(&link->cset_link);
- list_del(&link->cgrp_link);
+ list_del_init(&link->cset_link);
+ list_del_init(&link->cgrp_link);

/*
* We may not be holding cgroup_mutex, and if cgrp->count is
@@ -576,7 +576,7 @@ static void free_cgrp_cset_links(struct list_head *links_to_free)
struct cgrp_cset_link *link, *tmp_link;

list_for_each_entry_safe(link, tmp_link, links_to_free, cset_link) {
- list_del(&link->cset_link);
+ list_del_init(&link->cset_link);
kfree(link);
}
}
@@ -597,7 +597,7 @@ static int allocate_cgrp_cset_links(int count, struct list_head *tmp_links)
INIT_LIST_HEAD(tmp_links);

for (i = 0; i < count; i++) {
- link = kmalloc(sizeof(*link), GFP_KERNEL);
+ link = kzalloc(sizeof(*link), GFP_KERNEL);
if (!link) {
free_cgrp_cset_links(tmp_links);
return -ENOMEM;
@@ -658,7 +658,7 @@ static struct css_set *find_css_set(struct css_set *old_cset,
if (cset)
return cset;

- cset = kmalloc(sizeof(*cset), GFP_KERNEL);
+ cset = kzalloc(sizeof(*cset), GFP_KERNEL);
if (!cset)
return NULL;

@@ -1754,14 +1754,14 @@ static void cgroup_kill_sb(struct super_block *sb) {
write_lock(&css_set_lock);

list_for_each_entry_safe(link, tmp_link, &cgrp->cset_links, cset_link) {
- list_del(&link->cset_link);
- list_del(&link->cgrp_link);
+ list_del_init(&link->cset_link);
+ list_del_init(&link->cgrp_link);
kfree(link);
}
write_unlock(&css_set_lock);

if (!list_empty(&root->root_list)) {
- list_del(&root->root_list);
+ list_del_init(&root->root_list);
root_count--;
}

@@ -2478,10 +2478,12 @@ static int cgroup_file_open(struct inode *inode, struct file *file)
cft = __d_cft(file->f_dentry);

if (cft->read_map || cft->read_seq_string) {
- struct cgroup_seqfile_state *state =
- kzalloc(sizeof(*state), GFP_USER);
+ struct cgroup_seqfile_state *state;
+
+ state = kzalloc(sizeof(*state), GFP_USER);
if (!state)
return -ENOMEM;
+
state->cft = cft;
state->cgroup = __d_cgrp(file->f_dentry->d_parent);
file->f_op = &cgroup_seqfile_operations;
@@ -3514,7 +3516,7 @@ static struct cgroup_pidlist *cgroup_pidlist_find(struct cgroup *cgrp,
}
}
/* entry not found; create a new one */
- l = kmalloc(sizeof(struct cgroup_pidlist), GFP_KERNEL);
+ l = kzalloc(sizeof(struct cgroup_pidlist), GFP_KERNEL);
if (!l) {
mutex_unlock(&cgrp->pidlist_mutex);
return l;
@@ -3523,8 +3525,6 @@ static struct cgroup_pidlist *cgroup_pidlist_find(struct cgroup *cgrp,
down_write(&l->mutex);
l->key.type = type;
l->key.ns = get_pid_ns(ns);
- l->use_count = 0; /* don't increment here */
- l->list = NULL;
l->owner = cgrp;
list_add(&l->links, &cgrp->pidlists);
mutex_unlock(&cgrp->pidlist_mutex);
@@ -3738,7 +3738,7 @@ static void cgroup_release_pid_array(struct cgroup_pidlist *l)
BUG_ON(!l->use_count);
if (!--l->use_count) {
/* we're the last user if refcount is 0; remove and free */
- list_del(&l->links);
+ list_del_init(&l->links);
mutex_unlock(&l->owner->pidlist_mutex);
pidlist_free(l->list);
put_pid_ns(l->key.ns);
--
1.8.2.1

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