Re: [PATCH v4 11/12] mm/debug_vm_pgtable: Remove unused code

[Anshuman Khandual <anshuman.khandual@arm.com>]

On 7/27/21 11:44 AM, Gavin Shan wrote:
> The variables used by old implementation isn't needed as we switched
> to "struct pgtable_debug_args". Lets remove them and related code in
> debug_vm_pgtable().
> 
> Signed-off-by: Gavin Shan <gshan@redhat.com>
> ---
>  mm/debug_vm_pgtable.c | 54 -------------------------------------------
>  1 file changed, 54 deletions(-)
> 
> diff --git a/mm/debug_vm_pgtable.c b/mm/debug_vm_pgtable.c
> index 0611b5f31e89..162ff6329f7b 100644
> --- a/mm/debug_vm_pgtable.c
> +++ b/mm/debug_vm_pgtable.c
> @@ -1201,15 +1201,7 @@ static int __init init_args(struct pgtable_debug_args *args)
>  static int __init debug_vm_pgtable(void)
>  {
>  	struct pgtable_debug_args args;
> -	struct vm_area_struct *vma;
> -	struct mm_struct *mm;
> -	pgd_t *pgdp;
> -	p4d_t *p4dp;
> -	pud_t *pudp;
> -	pmd_t *pmdp, *saved_pmdp, pmd;
>  	pte_t *ptep;
> -	pgtable_t saved_ptep;
> -	unsigned long vaddr;
>  	spinlock_t *ptl = NULL;
>  	int idx, ret;
>  
> @@ -1218,41 +1210,6 @@ static int __init debug_vm_pgtable(void)
>  	if (ret)
>  		return ret;
>  
> -	vaddr = get_random_vaddr();
> -	mm = mm_alloc();
> -	if (!mm) {
> -		pr_err("mm_struct allocation failed\n");
> -		return 1;
> -	}
> -
> -	vma = vm_area_alloc(mm);
> -	if (!vma) {
> -		pr_err("vma allocation failed\n");
> -		return 1;
> -	}
> -
> -	pgdp = pgd_offset(mm, vaddr);
> -	p4dp = p4d_alloc(mm, pgdp, vaddr);
> -	pudp = pud_alloc(mm, p4dp, vaddr);
> -	pmdp = pmd_alloc(mm, pudp, vaddr);
> -	/*
> -	 * Allocate pgtable_t
> -	 */
> -	if (pte_alloc(mm, pmdp)) {
> -		pr_err("pgtable allocation failed\n");
> -		return 1;
> -	}
> -
> -	/*
> -	 * Save all the page table page addresses as the page table
> -	 * entries will be used for testing with random or garbage
> -	 * values. These saved addresses will be used for freeing
> -	 * page table pages.
> -	 */
> -	pmd = READ_ONCE(*pmdp);
> -	saved_pmdp = pmd_offset(pudp, 0UL);
> -	saved_ptep = pmd_pgtable(pmd);
> -
>  	/*
>  	 * Iterate over the protection_map[] to make sure that all
>  	 * the basic page table transformation validations just hold
> @@ -1335,17 +1292,6 @@ static int __init debug_vm_pgtable(void)
>  	pgd_populate_tests(&args);
>  	spin_unlock(&(args.mm->page_table_lock));
>  
> -	p4d_free(mm, p4d_offset(pgdp, 0UL));
> -	pud_free(mm, pud_offset(p4dp, 0UL));

Small nit. saved_p4dp and saved_pudp could have been dropped in this
patch rather than the previous one. Previous build error with W=1
might not have been a problem as there was a remaining usage after
the assignment.

> -	pmd_free(mm, saved_pmdp);
> -	pte_free(mm, saved_ptep);
> -
> -	vm_area_free(vma);
> -	mm_dec_nr_puds(mm);
> -	mm_dec_nr_pmds(mm);
> -	mm_dec_nr_ptes(mm);
> -	mmdrop(mm);
> -
>  	destroy_args(&args);
>  	return 0;
>  }
> 

With or without the above change.
 
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>