Re: [PATCH 3/3] s390: supplement for ptdesc conversion

[Vishal Moola]

On Mon, Mar 04, 2024 at 07:07:20PM +0800, Qi Zheng wrote:
> --- a/arch/s390/mm/gmap.c
> +++ b/arch/s390/mm/gmap.c
> @@ -206,9 +206,11 @@ static void gmap_free(struct gmap *gmap)
>  
>  	/* Free additional data for a shadow gmap */
>  	if (gmap_is_shadow(gmap)) {
> +		struct ptdesc *ptdesc;
> +
>  		/* Free all page tables. */
> -		list_for_each_entry_safe(page, next, &gmap->pt_list, lru)
> -			page_table_free_pgste(page);
> +		list_for_each_entry_safe(ptdesc, next, &gmap->pt_list, pt_list)
> +			page_table_free_pgste(ptdesc);

An important note: ptdesc allocation/freeing is different than the
standard alloc_pages()/free_pages() routines architectures are used to.
Are we sure we don't have memory leaks here?

We always allocate and free ptdescs as compound pages; for page table
struct pages, most archictectures do not. s390 has CRST_ALLOC_ORDER
pagetables, meaning if we free anything using the ptdesc api, we better
be sure it was allocated using the ptdesc api as well.

Like you, I don't have a s390 to test on, so hopefully some s390 expert
can chime in to let us know if we need a fix for this.