linux-kernel - Re: [PATCH v3 12/16] mm/mmap: Clean up unmap

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Message-ID: <44baee28-a626-4be6-98ed-f5473d99157c@lucifer.local>
Date: Fri, 5 Jul 2024 21:33:39 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: "Liam R. Howlett" <Liam.Howlett@...cle.com>
Cc: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>, Lorenzo Stoakes <lstoakes@...il.com>,
        Matthew Wilcox <willy@...radead.org>, sidhartha.kumar@...cle.com,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Bert Karwatzki <spasswolf@....de>, Jiri Olsa <olsajiri@...il.com>,
        linux-kernel@...r.kernel.org, Kees Cook <kees@...nel.org>
Subject: Re: [PATCH v3 12/16] mm/mmap: Clean up unmap_region() argument list

On Thu, Jul 04, 2024 at 02:27:14PM GMT, Liam R. Howlett wrote:
> From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
>
> With the only caller to unmap_region() being the error path of
> mmap_region(), the argument list can be significantly reduced.
>
> There is also no need to forward declare the static function any
> longer.
>
> Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> ---
>  mm/mmap.c | 25 +++++++++----------------
>  1 file changed, 9 insertions(+), 16 deletions(-)
>
> diff --git a/mm/mmap.c b/mm/mmap.c
> index 45443a53be76..5d458c5f080e 100644
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -76,11 +76,6 @@ int mmap_rnd_compat_bits __read_mostly = CONFIG_ARCH_MMAP_RND_COMPAT_BITS;
>  static bool ignore_rlimit_data;
>  core_param(ignore_rlimit_data, ignore_rlimit_data, bool, 0644);
>
> -static void unmap_region(struct mm_struct *mm, struct ma_state *mas,
> -		struct vm_area_struct *vma, struct vm_area_struct *prev,
> -		struct vm_area_struct *next, unsigned long start,
> -		unsigned long end, unsigned long tree_end, bool mm_wr_locked);
> -
>  static pgprot_t vm_pgprot_modify(pgprot_t oldprot, unsigned long vm_flags)
>  {
>  	return pgprot_modify(oldprot, vm_get_page_prot(vm_flags));
> @@ -2398,22 +2393,21 @@ struct vm_area_struct *expand_stack(struct mm_struct *mm, unsigned long addr)
>   *
>   * Called with the mm semaphore held.
>   */
> -static void unmap_region(struct mm_struct *mm, struct ma_state *mas,
> -		struct vm_area_struct *vma, struct vm_area_struct *prev,
> -		struct vm_area_struct *next, unsigned long start,
> -		unsigned long end, unsigned long tree_end, bool mm_wr_locked)
> +static void unmap_region(struct ma_state *mas, struct vm_area_struct *vma,
> +		struct vm_area_struct *prev, struct vm_area_struct *next)
>  {
> +	struct mm_struct *mm = vma->vm_mm;
>  	struct mmu_gather tlb;
> -	unsigned long mt_start = mas->index;
>
>  	lru_add_drain();
>  	tlb_gather_mmu(&tlb, mm);
>  	update_hiwater_rss(mm);
> -	unmap_vmas(&tlb, mas, vma, start, end, tree_end, mm_wr_locked);
> -	mas_set(mas, mt_start);

OK so the 'raise something in one patch only for it to be removed in the
next' pattern continues :) more aesthetically plasing.

> +	unmap_vmas(&tlb, mas, vma, vma->vm_start, vma->vm_end, vma->vm_end,
> +		   /* mm_wr_locked = */ true);
> +	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,
> -				 mm_wr_locked);
> +		      next ? next->vm_start : USER_PGTABLES_CEILING,
> +		      /* mm_wr_locked = */ true);
>  	tlb_finish_mmu(&tlb);
>  }
>
> @@ -3186,8 +3180,7 @@ unsigned long mmap_region(struct file *file, unsigned long addr,
>
>  		vma_iter_set(&vmi, vma->vm_end);
>  		/* Undo any partial mapping done by a device driver. */
> -		unmap_region(mm, &vmi.mas, vma, prev, next, vma->vm_start,
> -			     vma->vm_end, vma->vm_end, true);
> +		unmap_region(&vmi.mas, vma, prev, next);
>  	}
>  	if (writable_file_mapping)
>  		mapping_unmap_writable(file->f_mapping);
> --
> 2.43.0
>

Lovely reduction in parameters.

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