linux-kernel - Re: [PATCH v11 14/22] mm: pagewalk: Add 'depth' parameter to pte

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Date:   Mon, 7 Oct 2019 13:10:49 -0300
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Steven Price <steven.price@....com>
Cc:     linux-mm@...ck.org, Andy Lutomirski <luto@...nel.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        James Morse <james.morse@....com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will@...nel.org>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Mark Rutland <Mark.Rutland@....com>,
        "Liang, Kan" <kan.liang@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v11 14/22] mm: pagewalk: Add 'depth' parameter to pte_hole

On Mon, Oct 07, 2019 at 04:38:14PM +0100, Steven Price wrote:
> diff --git a/mm/hmm.c b/mm/hmm.c
> index 902f5fa6bf93..34fe904dd417 100644
> +++ b/mm/hmm.c
> @@ -376,7 +376,7 @@ static void hmm_range_need_fault(const struct hmm_vma_walk *hmm_vma_walk,
>  }
>  
>  static int hmm_vma_walk_hole(unsigned long addr, unsigned long end,
> -			     struct mm_walk *walk)
> +			     __always_unused int depth, struct mm_walk *walk)

It this __always_unused on function arguments something we are doing
now?

Can we have negative depth? Should it be unsigned?

>  {
>  	struct hmm_vma_walk *hmm_vma_walk = walk->private;
>  	struct hmm_range *range = hmm_vma_walk->range;
> @@ -564,7 +564,7 @@ static int hmm_vma_walk_pmd(pmd_t *pmdp,
>  again:
>  	pmd = READ_ONCE(*pmdp);
>  	if (pmd_none(pmd))
> -		return hmm_vma_walk_hole(start, end, walk);
> +		return hmm_vma_walk_hole(start, end, 0, walk);
>  
>  	if (thp_migration_supported() && is_pmd_migration_entry(pmd)) {
>  		bool fault, write_fault;
> @@ -666,7 +666,7 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
>  again:
>  	pud = READ_ONCE(*pudp);
>  	if (pud_none(pud))
> -		return hmm_vma_walk_hole(start, end, walk);
> +		return hmm_vma_walk_hole(start, end, 0, walk);
>  
>  	if (pud_huge(pud) && pud_devmap(pud)) {
>  		unsigned long i, npages, pfn;
> @@ -674,7 +674,7 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
>  		bool fault, write_fault;
>  
>  		if (!pud_present(pud))
> -			return hmm_vma_walk_hole(start, end, walk);
> +			return hmm_vma_walk_hole(start, end, 0, walk);
>  
>  		i = (addr - range->start) >> PAGE_SHIFT;
>  		npages = (end - addr) >> PAGE_SHIFT;

Otherwise this mechanical change to hmm.c looks OK to me

Jason