linux-kernel - Re: [PATCH 2/3] mm: update core kernel code to use vm_flags

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Message-ID: <aIgSpAnU8EaIcqd9@hyeyoo>
Date: Tue, 29 Jul 2025 09:15:51 +0900
From: Harry Yoo <harry.yoo@...cle.com>
To: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Madhavan Srinivasan <maddy@...ux.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        "David S . Miller" <davem@...emloft.net>,
        Andreas Larsson <andreas@...sler.com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
        Borislav Petkov <bp@...en8.de>, "H . Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>,
        Kees Cook <kees@...nel.org>, Peter Xu <peterx@...hat.com>,
        David Hildenbrand <david@...hat.com>, Zi Yan <ziy@...dia.com>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        "Liam R . Howlett" <Liam.Howlett@...cle.com>,
        Nico Pache <npache@...hat.com>, Ryan Roberts <ryan.roberts@....com>,
        Dev Jain <dev.jain@....com>, Barry Song <baohua@...nel.org>,
        Xu Xin <xu.xin16@....com.cn>,
        Chengming Zhou <chengming.zhou@...ux.dev>,
        Hugh Dickins <hughd@...gle.com>, Vlastimil Babka <vbabka@...e.cz>,
        Mike Rapoport <rppt@...nel.org>,
        Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>,
        Rik van Riel <riel@...riel.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Matthew Wilcox <willy@...radead.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Jason Gunthorpe <jgg@...pe.ca>, John Hubbard <jhubbard@...dia.com>,
        Muchun Song <muchun.song@...ux.dev>,
        Oscar Salvador <osalvador@...e.de>, Jann Horn <jannh@...gle.com>,
        Pedro Falcato <pfalcato@...e.de>, Johannes Weiner <hannes@...xchg.org>,
        Qi Zheng <zhengqi.arch@...edance.com>,
        Shakeel Butt <shakeel.butt@...ux.dev>,
        Uladzislau Rezki <urezki@...il.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, kvm@...r.kernel.org,
        sparclinux@...r.kernel.org, linux-sgx@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        nvdimm@...ts.linux.dev, linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] mm: update core kernel code to use vm_flags_t
 consistently

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@...cle.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