Re: [RFC PATCH 2/2] mm, memory_hotplug: drop CONFIG_MOVABLE_NODE

[Igor Mammedov]

On Wed, 24 May 2017 14:24:11 +0200
Michal Hocko <mhocko@xxxxxxxxxx> wrote:

[...]
> index facc20a3f962..ec7d6ae01c96 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -2246,8 +2246,11 @@
[...]
> +			movable. This means that the memory of such nodes
> +			will be usable only for movable allocations which
> +			rules out almost all kernel allocations. Use with
> +			caution!
maybe dumb question but, is it really true that kernel won't ever
do kernel allocations from movable zone?

looking at kmalloc(slab): we can get here:

get_page_from_freelist() ->
    rmqueue() ->
        __rmqueue() ->
            __rmqueue_fallback() ->
                find_suitable_fallback()

and it might return movable fallback and page could be stolen from there.