Re: [PATCH 2] mm/kvmalloc: do not call kmalloc for size > KMALLOC_MAX_SIZE

Michal Hocko
2018-11-01T10:24:07Z

On Thu 01-11-18 13:09:16, Konstantin Khlebnikov wrote:
> Allocations over KMALLOC_MAX_SIZE could be served only by vmalloc.

I would go on and say that allocations with sizes too large can actually
trigger a warning (once you have posted in the previous version outside
of the changelog area) because that might be interesting to people -
there are deployments to panic on warning and then a warning is much
more important.

> Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>

Acked-by: Michal Hocko <mhocko@suse.com>

Thanks!

> ---
> mm/util.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
> diff --git a/mm/util.c b/mm/util.c
> index 8bf08b5b5760..f5f04fa22814 100644
> --- a/mm/util.c
> +++ b/mm/util.c
> @@ -392,6 +392,9 @@ void *kvmalloc_node(size_t size, gfp_t flags, int node)
> gfp_t kmalloc_flags = flags;
> void *ret;
>
> + if (size > KMALLOC_MAX_SIZE)
> + goto fallback;
> +
> /*
> * vmalloc uses GFP_KERNEL for some internal allocations (e.g page tables)
> * so the given set of flags has to be compatible.
> @@ -422,6 +425,7 @@ void *kvmalloc_node(size_t size, gfp_t flags, int node)
> if (ret || size <= PAGE_SIZE)
> return ret;
>
> +fallback:
> return __vmalloc_node_flags_caller(size, node, flags,
> __builtin_return_address(0));
> }
>

--
Michal Hocko
SUSE Labs