linux-kernel - Re: [RFC PATCH 5/6] mm/vma: Add page table limit to unmap

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Message-ID: <ac33f990-1f79-498c-96ca-12ffb26d8093@lucifer.local>
Date: Tue, 19 Aug 2025 20:27:03 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: "Liam R. Howlett" <Liam.Howlett@...cle.com>
Cc: David Hildenbrand <david@...hat.com>, maple-tree@...ts.infradead.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Vlastimil Babka <vbabka@...e.cz>, Mike Rapoport <rppt@...nel.org>,
        Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jann Horn <jannh@...gle.com>, Pedro Falcato <pfalcato@...e.de>,
        Charan Teja Kalla <quic_charante@...cinc.com>,
        shikemeng@...weicloud.com, kasong@...cent.com, nphamcs@...il.com,
        bhe@...hat.com, baohua@...nel.org, chrisl@...nel.org,
        Matthew Wilcox <willy@...radead.org>
Subject: Re: [RFC PATCH 5/6] mm/vma: Add page table limit to unmap_region()

On Fri, Aug 15, 2025 at 03:10:30PM -0400, Liam R. Howlett wrote:
> The unmap_region() calls need to pass through the page table limit for a
> future patch.
>
> No functional changes intended.
>
> Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>

This functionally LGTM, but see comment below... about a comment :P

Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>

> ---
>  mm/vma.c | 5 +++--
>  mm/vma.h | 2 +-
>  2 files changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/mm/vma.c b/mm/vma.c
> index aa75ca8618609..39f3b55a020b2 100644
> --- a/mm/vma.c
> +++ b/mm/vma.c
> @@ -474,7 +474,7 @@ void remove_vma(struct vm_area_struct *vma)
>   * Called with the mm semaphore held.
>   */
>  void unmap_region(struct ma_state *mas, struct vm_area_struct *vma,
> -		unsigned long vma_min, unsigned long vma_max,
> +		unsigned long vma_min, unsigned long vma_max, unsigned long pg_max,
>  		struct vm_area_struct *prev, struct vm_area_struct *next)

See previous comments about refactoring unmap_region(), also let's have a
comment explaining what's going on with these parameters too.

>  {
>  	struct mm_struct *mm = vma->vm_mm;
> @@ -487,7 +487,7 @@ void unmap_region(struct ma_state *mas, struct vm_area_struct *vma,
>  	mas_set(mas, vma->vm_end);
>  	free_pgtables(&tlb, mas, vma, prev ? prev->vm_end : FIRST_USER_ADDRESS,
>  		      next ? next->vm_start : USER_PGTABLES_CEILING,
> -		      next ? next->vm_start : USER_PGTABLES_CEILING,
> +		      pg_max,
>  		      /* mm_wr_locked = */ true);
>  	tlb_finish_mmu(&tlb);
>  }
> @@ -2420,6 +2420,7 @@ static int __mmap_new_file_vma(struct mmap_state *map,
>  		vma_iter_set(vmi, vma->vm_end);
>  		/* Undo any partial mapping done by a device driver. */
>  		unmap_region(&vmi->mas, vma, vma->vm_start, vma->vm_end,
> +			     map->next ? map->next->vm_start : USER_PGTABLES_CEILING,
>  			     map->prev, map->next);
>
>  		return error;
> diff --git a/mm/vma.h b/mm/vma.h
> index 336dae295853e..ba203c0c1d89d 100644
> --- a/mm/vma.h
> +++ b/mm/vma.h
> @@ -281,7 +281,7 @@ int do_vmi_munmap(struct vma_iterator *vmi, struct mm_struct *mm,
>  void remove_vma(struct vm_area_struct *vma);
>
>  void unmap_region(struct ma_state *mas, struct vm_area_struct *vma,
> -		unsigned long min, unsigned long max,
> +		unsigned long min, unsigned long max, unsigned long pg_max,
>  		struct vm_area_struct *prev, struct vm_area_struct *next);
>
>  /* We are about to modify the VMA's flags. */
> --
> 2.47.2
>