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SubjectRe: [PATCH 1/9] [RFC] Support named cgroups hierarchies
> +static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts)
> +{
> + struct cgroupfs_root *root;
> +
> + if (!opts->subsys_bits)
> + return ERR_PTR(-EINVAL);
> +
> + root = kzalloc(sizeof(*root), GFP_KERNEL);
> + if (!root)
> + return ERR_PTR(-ENOMEM);
> +
> + init_cgroup_root(root);
> + root->subsys_bits = opts->subsys_bits;
> + root->flags = opts->flags;
> + if (opts->release_agent)
> + strcpy(root->release_agent_path, opts->release_agent);
> + if (opts->name)
> + strcpy(root->name, opts->name);
> + opts->created_root = true;
> + return root;
> +}
> +
> static int cgroup_set_super(struct super_block *sb, void *data)
> {
> int ret;
> - struct cgroupfs_root *root = data;
> + struct cgroup_sb_opts *opts = data;
> + struct cgroupfs_root *root;
>
> + root = cgroup_root_from_opts(opts);
> + if (IS_ERR(root))
> + return PTR_ERR(root);
> ret = set_anon_super(sb, NULL);
> - if (ret)
> + if (ret) {
> + kfree(root);
> return ret;
> + }
>
> sb->s_fs_info = root;
> root->sb = sb;
> @@ -1039,44 +1091,23 @@ static int cgroup_get_sb(struct file_system_type *fs_type,
> struct cgroup_sb_opts opts;
> int ret = 0;
> struct super_block *sb;
> - struct cgroupfs_root *root;
> - struct list_head tmp_cg_links;
>
> /* First find the desired set of subsystems */
> ret = parse_cgroupfs_options(data, &opts);
> - if (ret) {
> - kfree(opts.release_agent);
> - return ret;
> - }
> -
> - root = kzalloc(sizeof(*root), GFP_KERNEL);
> - if (!root) {
> - kfree(opts.release_agent);
> - return -ENOMEM;
> - }
> -
> - init_cgroup_root(root);
> - root->subsys_bits = opts.subsys_bits;
> - root->flags = opts.flags;
> - if (opts.release_agent) {
> - strcpy(root->release_agent_path, opts.release_agent);
> - kfree(opts.release_agent);
> - }
> + if (ret)
> + goto out_err;
>
> - sb = sget(fs_type, cgroup_test_super, cgroup_set_super, root);
> + sb = sget(fs_type, cgroup_test_super, cgroup_set_super, &opts);
>

cgroup_set_super() is called with spinlock held, so we
can't do kmalloc(GFP_KERNEL).

sget(...)
{
spin_lock(&sb_lock);
...
err = set(s, data);
if (err) {
spin_unlock(&sb_lock);
...
}
> if (IS_ERR(sb)) {
> - kfree(root);
> - return PTR_ERR(sb);
> + ret = PTR_ERR(sb);
> + goto out_err;
> }
>
> - if (sb->s_fs_info != root) {
> - /* Reusing an existing superblock */
> - BUG_ON(sb->s_root == NULL);
> - kfree(root);
> - root = NULL;
> - } else {
> + if (opts.created_root) {
> /* New superblock */
> + struct cgroupfs_root *root = sb->s_fs_info;
> + struct list_head tmp_cg_links;
> struct cgroup *root_cgrp = &root->top_cgroup;
> struct inode *inode;
> int i;
> @@ -1109,7 +1140,8 @@ static int cgroup_get_sb(struct file_system_type *fs_type,
> if (ret == -EBUSY) {
> mutex_unlock(&cgroup_mutex);
> mutex_unlock(&inode->i_mutex);
> - goto free_cg_links;
> + free_cg_links(&tmp_cg_links);
> + goto drop_new_super;
> }
>
> /* EBUSY should be the only error here */
> @@ -1146,12 +1178,17 @@ static int cgroup_get_sb(struct file_system_type *fs_type,
> }
>
> simple_set_mnt(mnt, sb);
> + kfree(opts.release_agent);
> + kfree(opts.name);
> return 0;
>
> - free_cg_links:
> - free_cg_links(&tmp_cg_links);
> drop_new_super:
> deactivate_locked_super(sb);
> +
> + out_err:
> + kfree(opts.release_agent);
> + kfree(opts.name);
> +
> return ret;
> }


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