Re: [PATCH v3 11/12] mm/debug_vm_pgtable: Remove unused code

[Gavin Shan]

Hi Anshuman,

On 7/22/21 2:51 PM, Anshuman Khandual wrote:
> Small nit for the subject line.
>
> s/Remove unused code/Remove unused page table debug elements/

Ok. Will apply the replacement in v4, thanks!

> On 7/19/21 6:36 PM, 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@xxxxxxxxxx>
> > ---
> >   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 5ebacc940b68..4f7bf1c9724a 100644
> > --- a/mm/debug_vm_pgtable.c
> > +++ b/mm/debug_vm_pgtable.c
> > @@ -1124,14 +1124,6 @@ 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;
> > -	pgtable_t saved_ptep;
> > -	unsigned long vaddr;
> >   	spinlock_t *ptl = NULL;
> >   	int idx, ret;
> >   
> > @@ -1140,41 +1132,6 @@ 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.
> > -	 */
>
> Please move this comment as is to the right place inside init_args()
> in the first patch itself. If possible all comments should be moved
> during the first patch and just the code gets dropped here.

In PATCH[v3 01/12], We already had the comments in init_args() as below:

       /*
        * The above page table entries will be modified. Lets save the
        * page table entries so that they can be released when the tests
        * are completed.
        */


> > -	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
> > @@ -1256,17 +1213,6 @@ 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));
> > -	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;
> >   }

Thanks,
Gavin