Re: [PATCH] mm, vmalloc: use __GFP_HIGHMEM implicitly

[Matthew Wilcox]

On Tue, Mar 07, 2017 at 03:10:20PM +0100, Michal Hocko wrote:
> From: Michal Hocko <mhocko@xxxxxxxx>
> 
> __vmalloc* allows users to provide gfp flags for the underlying
> allocation. This API is quite popular
> $ git grep "=[[:space:]]__vmalloc\|return[[:space:]]*__vmalloc" | wc -l
> 77
> 
> the only problem is that many people are not aware that they really want
> to give __GFP_HIGHMEM along with other flags because there is really no
> reason to consume precious lowmemory on CONFIG_HIGHMEM systems for pages
> which are mapped to the kernel vmalloc space. About half of users don't
> use this flag, though. This signals that we make the API unnecessarily
> too complex.
> 
> This patch simply uses __GFP_HIGHMEM implicitly when allocating pages to
> be mapped to the vmalloc space. Current users which add __GFP_HIGHMEM
> are simplified and drop the flag.
> 
> Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>

Reviewed-by: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>