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Date: Mon, 1 Dec 2008 16:20:42 -0800
From: Paul Menage <menage@...gle.com>
To: Li Zefan <lizf@...fujitsu.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
LKML <linux-kernel@...r.kernel.org>,
Linux Containers <containers@...ts.linux-foundation.org>
Subject: Re: [PATCH 3/3] cgroups: introduce link_css_set() to remove duplicate
code
On Fri, Nov 28, 2008 at 2:02 AM, Li Zefan <lizf@...fujitsu.com> wrote:
> Add a common function link_css_set() to link a css_set to a cgroup.
>
> Signed-off-by: Li Zefan <lizf@...fujitsu.com>
Overall the change looks like an improvement, but:
- the new function could do with comments about the semantics of its
parameters, particularly tmp_cg_links.
- why are you renaming cgrp -> root_cgrp in cgroup_get_sb()? That
seems like unnecessary churn.
Thanks,
Paul
> ---
> kernel/cgroup.c | 62 +++++++++++++++++++++---------------------------------
> 1 files changed, 24 insertions(+), 38 deletions(-)
>
> diff --git a/kernel/cgroup.c b/kernel/cgroup.c
> index 4e50e97..1442077 100644
> --- a/kernel/cgroup.c
> +++ b/kernel/cgroup.c
> @@ -385,6 +385,19 @@ static int allocate_cg_links(int count, struct list_head *tmp)
> return 0;
> }
>
> +static void link_css_set(struct list_head *tmp_cg_links,
> + struct css_set *cg, struct cgroup *cgrp)
> +{
> + struct cg_cgroup_link *link;
> +
> + BUG_ON(list_empty(tmp_cg_links));
> + link = list_first_entry(tmp_cg_links, struct cg_cgroup_link,
> + cgrp_link_list);
> + link->cg = cg;
> + list_move(&link->cgrp_link_list, &cgrp->css_sets);
> + list_add(&link->cg_link_list, &cg->cg_links);
> +}
> +
> /*
> * find_css_set() takes an existing cgroup group and a
> * cgroup object, and returns a css_set object that's
> @@ -400,7 +413,6 @@ static struct css_set *find_css_set(
> int i;
>
> struct list_head tmp_cg_links;
> - struct cg_cgroup_link *link;
>
> struct hlist_head *hhead;
>
> @@ -445,26 +457,11 @@ static struct css_set *find_css_set(
> * only do it for the first subsystem in each
> * hierarchy
> */
> - if (ss->root->subsys_list.next == &ss->sibling) {
> - BUG_ON(list_empty(&tmp_cg_links));
> - link = list_entry(tmp_cg_links.next,
> - struct cg_cgroup_link,
> - cgrp_link_list);
> - list_del(&link->cgrp_link_list);
> - list_add(&link->cgrp_link_list, &cgrp->css_sets);
> - link->cg = res;
> - list_add(&link->cg_link_list, &res->cg_links);
> - }
> - }
> - if (list_empty(&rootnode.subsys_list)) {
> - link = list_entry(tmp_cg_links.next,
> - struct cg_cgroup_link,
> - cgrp_link_list);
> - list_del(&link->cgrp_link_list);
> - list_add(&link->cgrp_link_list, &dummytop->css_sets);
> - link->cg = res;
> - list_add(&link->cg_link_list, &res->cg_links);
> + if (ss->root->subsys_list.next == &ss->sibling)
> + link_css_set(&tmp_cg_links, res, cgrp);
> }
> + if (list_empty(&rootnode.subsys_list))
> + link_css_set(&tmp_cg_links, res, dummytop);
>
> BUG_ON(!list_empty(&tmp_cg_links));
>
> @@ -992,7 +989,7 @@ static int cgroup_get_sb(struct file_system_type *fs_type,
> root = NULL;
> } else {
> /* New superblock */
> - struct cgroup *cgrp = &root->top_cgroup;
> + struct cgroup *root_cgrp = &root->top_cgroup;
> struct inode *inode;
> int i;
>
> @@ -1033,7 +1030,7 @@ static int cgroup_get_sb(struct file_system_type *fs_type,
> list_add(&root->root_list, &roots);
> root_count++;
>
> - sb->s_root->d_fsdata = &root->top_cgroup;
> + sb->s_root->d_fsdata = root_cgrp;
> root->top_cgroup.dentry = sb->s_root;
>
> /* Link the top cgroup in this hierarchy into all
> @@ -1044,29 +1041,18 @@ static int cgroup_get_sb(struct file_system_type *fs_type,
> struct hlist_node *node;
> struct css_set *cg;
>
> - hlist_for_each_entry(cg, node, hhead, hlist) {
> - struct cg_cgroup_link *link;
> -
> - BUG_ON(list_empty(&tmp_cg_links));
> - link = list_entry(tmp_cg_links.next,
> - struct cg_cgroup_link,
> - cgrp_link_list);
> - list_del(&link->cgrp_link_list);
> - link->cg = cg;
> - list_add(&link->cgrp_link_list,
> - &root->top_cgroup.css_sets);
> - list_add(&link->cg_link_list, &cg->cg_links);
> - }
> + hlist_for_each_entry(cg, node, hhead, hlist)
> + link_css_set(&tmp_cg_links, cg, root_cgrp);
> }
> write_unlock(&css_set_lock);
>
> free_cg_links(&tmp_cg_links);
>
> - BUG_ON(!list_empty(&cgrp->sibling));
> - BUG_ON(!list_empty(&cgrp->children));
> + BUG_ON(!list_empty(&root_cgrp->sibling));
> + BUG_ON(!list_empty(&root_cgrp->children));
> BUG_ON(root->number_of_cgroups != 1);
>
> - cgroup_populate_dir(cgrp);
> + cgroup_populate_dir(root_cgrp);
> mutex_unlock(&inode->i_mutex);
> mutex_unlock(&cgroup_mutex);
> }
> --
> 1.5.4.rc3
>
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