Re: [PATCH v11 14/22] mm: pagewalk: Add 'depth' parameter to pte_hole

From: Jason Gunthorpe <jgg@ziepe.ca>
To: Steven Price <steven.price@arm.com>
Cc: linux-mm@kvack.org, "Andy Lutomirski" <luto@kernel.org>,
	"Ard Biesheuvel" <ard.biesheuvel@linaro.org>,
	"Arnd Bergmann" <arnd@arndb.de>, "Borislav Petkov" <bp@alien8.de>,
	"Catalin Marinas" <catalin.marinas@arm.com>,
	"Dave Hansen" <dave.hansen@linux.intel.com>,
	"Ingo Molnar" <mingo@redhat.com>,
	"James Morse" <james.morse@arm.com>,
	"Jérôme Glisse" <jglisse@redhat.com>,
	"Peter Zijlstra" <peterz@infradead.org>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Will Deacon" <will@kernel.org>,
	x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org,
	"Mark Rutland" <Mark.Rutland@arm.com>,
	"Liang, Kan" <kan.liang@linux.intel.com>,
	"Andrew Morton" <akpm@linux-foundation.org>
Subject: Re: [PATCH v11 14/22] mm: pagewalk: Add 'depth' parameter to pte_hole
Date: Mon, 7 Oct 2019 13:10:49 -0300	[thread overview]
Message-ID: <20191007161049.GA13229@ziepe.ca> (raw)
In-Reply-To: <20191007153822.16518-15-steven.price@arm.com>

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