linux-kernel - Re: [PATCH v2 1/5] userfaultfd: move vma_can

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Message-ID: <i3qrqbj6nhqpjrnolg2zf6nmbdwsw6ejgmugzkeg6iqsi22jjv@ycv5iw7iaeol>
Date: Wed, 26 Nov 2025 10:05:49 -0500
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: Mike Rapoport <rppt@...nel.org>
Cc: linux-mm@...ck.org, Andrea Arcangeli <aarcange@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        David Hildenbrand <david@...hat.com>, Hugh Dickins <hughd@...gle.com>,
        James Houghton <jthoughton@...gle.com>,
        Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
        Michal Hocko <mhocko@...e.com>, Nikita Kalyazin <kalyazin@...zon.com>,
        Paolo Bonzini <pbonzini@...hat.com>, Peter Xu <peterx@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>, Shuah Khan <shuah@...nel.org>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, linux-kselftest@...r.kernel.org,
        "David Hildenbrand (Red Hat)" <david@...nel.org>
Subject: Re: [PATCH v2 1/5] userfaultfd: move vma_can_userfault out of line

* Mike Rapoport <rppt@...nel.org> [251125 13:39]:
> From: "Mike Rapoport (Microsoft)" <rppt@...nel.org>
> 
> vma_can_userfault() has grown pretty big and it's not called on
> performance critical path.
> 
> Move it out of line.
> 
> No functional changes.
> 
> Reviewed-by: David Hildenbrand (Red Hat) <david@...nel.org>
> Signed-off-by: Mike Rapoport (Microsoft) <rppt@...nel.org>

Reviewed-by: Liam R. Howlett <Liam.Howlett@...cle.com>

> ---
>  include/linux/userfaultfd_k.h | 36 ++---------------------------------
>  mm/userfaultfd.c              | 34 +++++++++++++++++++++++++++++++++
>  2 files changed, 36 insertions(+), 34 deletions(-)
> 
> diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h
> index c0e716aec26a..e4f43e7b063f 100644
> --- a/include/linux/userfaultfd_k.h
> +++ b/include/linux/userfaultfd_k.h
> @@ -208,40 +208,8 @@ static inline bool userfaultfd_armed(struct vm_area_struct *vma)
>  	return vma->vm_flags & __VM_UFFD_FLAGS;
>  }
>  
> -static inline bool vma_can_userfault(struct vm_area_struct *vma,
> -				     vm_flags_t vm_flags,
> -				     bool wp_async)
> -{
> -	vm_flags &= __VM_UFFD_FLAGS;
> -
> -	if (vma->vm_flags & VM_DROPPABLE)
> -		return false;
> -
> -	if ((vm_flags & VM_UFFD_MINOR) &&
> -	    (!is_vm_hugetlb_page(vma) && !vma_is_shmem(vma)))
> -		return false;
> -
> -	/*
> -	 * If wp async enabled, and WP is the only mode enabled, allow any
> -	 * memory type.
> -	 */
> -	if (wp_async && (vm_flags == VM_UFFD_WP))
> -		return true;
> -
> -#ifndef CONFIG_PTE_MARKER_UFFD_WP
> -	/*
> -	 * If user requested uffd-wp but not enabled pte markers for
> -	 * uffd-wp, then shmem & hugetlbfs are not supported but only
> -	 * anonymous.
> -	 */
> -	if ((vm_flags & VM_UFFD_WP) && !vma_is_anonymous(vma))
> -		return false;
> -#endif
> -
> -	/* By default, allow any of anon|shmem|hugetlb */
> -	return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma) ||
> -	    vma_is_shmem(vma);
> -}
> +bool vma_can_userfault(struct vm_area_struct *vma, vm_flags_t vm_flags,
> +		       bool wp_async);
>  
>  static inline bool vma_has_uffd_without_event_remap(struct vm_area_struct *vma)
>  {
> diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
> index af61b95c89e4..8dc964389b0d 100644
> --- a/mm/userfaultfd.c
> +++ b/mm/userfaultfd.c
> @@ -1977,6 +1977,40 @@ ssize_t move_pages(struct userfaultfd_ctx *ctx, unsigned long dst_start,
>  	return moved ? moved : err;
>  }
>  
> +bool vma_can_userfault(struct vm_area_struct *vma, vm_flags_t vm_flags,
> +		       bool wp_async)
> +{
> +	vm_flags &= __VM_UFFD_FLAGS;
> +
> +	if (vma->vm_flags & VM_DROPPABLE)
> +		return false;
> +
> +	if ((vm_flags & VM_UFFD_MINOR) &&
> +	    (!is_vm_hugetlb_page(vma) && !vma_is_shmem(vma)))
> +		return false;
> +
> +	/*
> +	 * If wp async enabled, and WP is the only mode enabled, allow any
> +	 * memory type.
> +	 */
> +	if (wp_async && (vm_flags == VM_UFFD_WP))
> +		return true;
> +
> +#ifndef CONFIG_PTE_MARKER_UFFD_WP
> +	/*
> +	 * If user requested uffd-wp but not enabled pte markers for
> +	 * uffd-wp, then shmem & hugetlbfs are not supported but only
> +	 * anonymous.
> +	 */
> +	if ((vm_flags & VM_UFFD_WP) && !vma_is_anonymous(vma))
> +		return false;
> +#endif
> +
> +	/* By default, allow any of anon|shmem|hugetlb */
> +	return vma_is_anonymous(vma) || is_vm_hugetlb_page(vma) ||
> +	    vma_is_shmem(vma);
> +}
> +
>  static void userfaultfd_set_vm_flags(struct vm_area_struct *vma,
>  				     vm_flags_t vm_flags)
>  {
> -- 
> 2.50.1
>