Re: [PATCH cgroup] cgroup: set the correct return code if hierarchy limits are reached

[Roman Gushchin]

On Mon, Jun 27, 2022 at 05:12:55AM +0300, Vasily Averin wrote:
> When cgroup_mkdir reaches the limits of the cgroup hierarchy, it should
> not return -EAGAIN, but instead react similarly to reaching the global
> limit.
> 
> Signed-off-by: Vasily Averin <vvs@xxxxxxxxxx>
> ---
>  kernel/cgroup/cgroup.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
> index 1be0f81fe8e1..243239553ea3 100644
> --- a/kernel/cgroup/cgroup.c
> +++ b/kernel/cgroup/cgroup.c
> @@ -5495,7 +5495,7 @@ int cgroup_mkdir(struct kernfs_node *parent_kn, const char *name, umode_t mode)
>  		return -ENODEV;
>  
>  	if (!cgroup_check_hierarchy_limits(parent)) {
> -		ret = -EAGAIN;
> +		ret = -ENOSPC;

I'd not argue whether ENOSPC is better or worse here, but I don't think we need
to change it now. It's been in this state for a long time and is a part of ABI.
EAGAIN is pretty unique as a mkdir() result, so systemd can handle it well.

Thanks!