On Wed 24-07-13 17:59:12, Li Zefan wrote:
> This enables us to lookup a cgroup by its id.
>
> Signed-off-by: Li Zefan <lizefan@xxxxxxxxxx>
Reviewed-by: Michal Hocko <mhocko@xxxxxxx>
One nit/question bellow
[...]
> @@ -4268,15 +4271,19 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
> if (!cgrp)
> return -ENOMEM;
>
> + /*
> + * Temporarily set the pointer to NULL, so idr_find() won't return
> + * a half-baked cgroup.
> + */
> + cgrp->id = idr_alloc(&root->cgroup_idr, NULL, 1, 0, GFP_KERNEL);
> + if (cgrp->id < 0)
> + goto err_free_cgrp;
> +
> name = cgroup_alloc_name(dentry);
> if (!name)
> - goto err_free_cgrp;
> + goto err_free_id;
> rcu_assign_pointer(cgrp->name, name);
>
> - cgrp->id = ida_simple_get(&root->cgroup_ida, 1, 0, GFP_KERNEL);
> - if (cgrp->id < 0)
> - goto err_free_name;
> -
Is the move necessary? You would safe few lines in the patch if you kept
the ordering.
> /*
> * Only live parents can have children. Note that the liveliness
> * check isn't strictly necessary because cgroup_mkdir() and
> @@ -4286,7 +4293,7 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
> */
> if (!cgroup_lock_live_group(parent)) {
> err = -ENODEV;
> - goto err_free_id;
> + goto err_free_name;
> }
>
> /* Grab a reference on the superblock so the hierarchy doesn't
> @@ -4371,6 +4378,8 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
> }
> }
>
> + idr_replace(&root->cgroup_idr, cgrp, cgrp->id);
> +
> err = cgroup_addrm_files(cgrp, NULL, cgroup_base_files, true);
> if (err)
> goto err_destroy;
> @@ -4396,10 +4405,10 @@ err_free_all:
> mutex_unlock(&cgroup_mutex);
> /* Release the reference count that we took on the superblock */
> deactivate_super(sb);
> -err_free_id:
> - ida_simple_remove(&root->cgroup_ida, cgrp->id);
> err_free_name:
> kfree(rcu_dereference_raw(cgrp->name));
> +err_free_id:
> + idr_remove(&root->cgroup_idr, cgrp->id);
> err_free_cgrp:
> kfree(cgrp);
> return err;
[...]
--
Michal Hocko
SUSE Labs
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