Re: [PATCH] mm/vmalloc: add missing __GFP_HIGHMEM flag for vmalloc

[Matthew Wilcox <willy@infradead.org>]

On Mon, Jul 26, 2021 at 11:23:33AM +0800, Chen Wandun wrote:
> struct page array can also be allocated in highmem during vmalloc,
> that will ease the low memory stress in 32bit system.

Huh?  Where does it get kmapped in order to access it?

> Fixes: f255935b9767 ("mm: cleanup the gfp_mask handling in __vmalloc_area_node")
> Signed-off-by: Chen Wandun <chenwandun@huawei.com>
> ---
>  mm/vmalloc.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 3824dc16ce1c..8d9b0b08a6dc 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -2885,7 +2885,8 @@ static void *__vmalloc_area_node(struct vm_struct *area, gfp_t gfp_mask,
>  
>  	/* Please note that the recursion is strictly bounded. */
>  	if (array_size > PAGE_SIZE) {
> -		area->pages = __vmalloc_node(array_size, 1, nested_gfp, node,
> +		area->pages = __vmalloc_node(array_size, 1,
> +					nested_gfp | __GFP_HIGHMEM, node,
>  					area->caller);
>  	} else {
>  		area->pages = kmalloc_node(array_size, nested_gfp, node);
> -- 
> 2.25.1
> 
>