Re: [PATCH 2/3] mm: update core kernel code to use vm_flags_t consistently

Harry Yoo
2025-07-29T00:18:29Z

On Wed, Jun 18, 2025 at 08:42:53PM +0100, Lorenzo Stoakes wrote:
> The core kernel code is currently very inconsistent in its use of
> vm_flags_t vs. unsigned long. This prevents us from changing the type of
> vm_flags_t in the future and is simply not correct, so correct this.
>
> While this results in rather a lot of churn, it is a critical pre-requisite
> for a future planned change to VMA flag type.
>
> Additionally, update VMA userland tests to account for the changes.
>
> To make review easier and to break things into smaller parts, driver and
> architecture-specific changes is left for a subsequent commit.
>
> The code has been adjusted to cascade the changes across all calling code
> as far as is needed.
>
> We will adjust architecture-specific and driver code in a subsequent patch.
>
> Overall, this patch does not introduce any functional change.
>
> Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
> ---

[Adding Uladzislau to Cc]

Hi Lorenzo, just wanted to clarify one thing.

You know, many people acked and reviewed it, which makes me wonder if
I'm misunderstanding something... but it wouldn't hurt to check, right?

> diff --git a/mm/execmem.c b/mm/execmem.c
> index 9720ac2dfa41..bd95ff6a1d03 100644
> --- a/mm/execmem.c
> +++ b/mm/execmem.c
> @@ -26,7 +26,7 @@ static struct execmem_info default_execmem_info __ro_after_init;
>
> #ifdef CONFIG_MMU
> static void *execmem_vmalloc(struct execmem_range *range, size_t size,
> - pgprot_t pgprot, unsigned long vm_flags)
> + pgprot_t pgprot, vm_flags_t vm_flags)
> {
> bool kasan = range->flags & EXECMEM_KASAN_SHADOW;
> gfp_t gfp_flags = GFP_KERNEL | __GFP_NOWARN;

Is it intentional to use vm_flags_t for vm_struct flags, not vma flags?

You didn't update the type of struct vm_struct.flags field and vm_flags
parameter in __vmalloc_node_range_noprof() (of MMU version in mm/vmalloc.c)
...which makes me suspect it's not intentional?

> @@ -82,7 +82,7 @@ struct vm_struct *execmem_vmap(size_t size)
> }
> #else
> static void *execmem_vmalloc(struct execmem_range *range, size_t size,
> - pgprot_t pgprot, unsigned long vm_flags)
> + pgprot_t pgprot, vm_flags_t vm_flags)
> {
> return vmalloc(size);
> }

ditto.

> @@ -284,7 +284,7 @@ void execmem_cache_make_ro(void)
>
> static int execmem_cache_populate(struct execmem_range *range, size_t size)
> {
> - unsigned long vm_flags = VM_ALLOW_HUGE_VMAP;
> + vm_flags_t vm_flags = VM_ALLOW_HUGE_VMAP;
> struct vm_struct *vm;
> size_t alloc_size;
> int err = -ENOMEM;

ditto.

> @@ -407,7 +407,7 @@ void *execmem_alloc(enum execmem_type type, size_t size)
> {
> struct execmem_range *range = &execmem_info->ranges[type];
> bool use_cache = range->flags & EXECMEM_ROX_CACHE;
> - unsigned long vm_flags = VM_FLUSH_RESET_PERMS;
> + vm_flags_t vm_flags = VM_FLUSH_RESET_PERMS;
> pgprot_t pgprot = range->pgprot;
> void *p;

ditto.

> diff --git a/mm/internal.h b/mm/internal.h
> index feda91c9b3f4..506c6fc8b6dc 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -1360,7 +1360,7 @@ int migrate_device_coherent_folio(struct folio *folio);
>
> struct vm_struct *__get_vm_area_node(unsigned long size,
> unsigned long align, unsigned long shift,
> - unsigned long flags, unsigned long start,
> + vm_flags_t vm_flags, unsigned long start,
> unsigned long end, int node, gfp_t gfp_mask,
> const void *caller);

ditto.

> diff --git a/mm/nommu.c b/mm/nommu.c
> index b624acec6d2e..87e1acab0d64 100644
> --- a/mm/nommu.c
> +++ b/mm/nommu.c
> @@ -126,7 +126,7 @@ void *vrealloc_noprof(const void *p, size_t size, gfp_t flags)
>
> void *__vmalloc_node_range_noprof(unsigned long size, unsigned long align,
> unsigned long start, unsigned long end, gfp_t gfp_mask,
> - pgprot_t prot, unsigned long vm_flags, int node,
> + pgprot_t prot, vm_flags_t vm_flags, int node,
> const void *caller)
> {

ditto.

> return __vmalloc_noprof(size, gfp_mask);

--
Cheers,
Harry / Hyeonggon