linux-kernel - Re: [PATCH v1 5/7] mm/pagewalk: add walk_page_range

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Message-ID: <274c790a-04c7-078a-19be-851066dc21bb@redhat.com>
Date:   Thu, 6 Oct 2022 11:35:38 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Peter Xu <peterx@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        linux-kselftest@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Shuah Khan <shuah@...nel.org>, Hugh Dickins <hughd@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Andrea Arcangeli <aarcange@...hat.com>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Jason Gunthorpe <jgg@...dia.com>,
        John Hubbard <jhubbard@...dia.com>
Subject: Re: [PATCH v1 5/7] mm/pagewalk: add walk_page_range_vma()

On 05.10.22 22:42, Peter Xu wrote:
> On Fri, Sep 30, 2022 at 04:19:29PM +0200, David Hildenbrand wrote:
>> +int walk_page_range_vma(struct vm_area_struct *vma, unsigned long start,
>> +			unsigned long end, const struct mm_walk_ops *ops,
>> +			void *private)
>> +{
>> +	struct mm_walk walk = {
>> +		.ops		= ops,
>> +		.mm		= vma->vm_mm,
>> +		.vma		= vma,
>> +		.private	= private,
>> +	};
>> +	int err;
>> +
>> +	if (start >= end || !walk.mm)
>> +		return -EINVAL;
>> +	if (start < vma->vm_start || end > vma->vm_end)
>> +		return -EINVAL;
>> +
>> +	mmap_assert_locked(walk.mm);
>> +
>> +	err = walk_page_test(start, end, &walk);
> 
> According to test_walk():
> 
>   * @test_walk:		caller specific callback function to determine whether
>   *			we walk over the current vma or not. Returning 0 means
>   *			"do page table walk over the current vma", returning
>   *			a negative value means "abort current page table walk
>   *			right now" and returning 1 means "skip the current vma"
> 
> Since this helper has vma passed in, not sure whether this is needed at
> all?

I kept it because walk_page_vma() similarly has it -- walk_page_vma() 
walks the whole VMA range.

I do agree that it's kind of weird to have it like that. All users of 
walk_page_vma() don't use it, so we can just get rid of it there as 
well. Might make the walk slightly faster.

> 
> walk_page_vma_range() sounds slightly better to me as it does look more
> like an extension of walk_page_vma(), rather than sister version of
> walk_page_range_novma() (which works for "no backing VMA" case).  But no
> strong opinion.
> 

I matched that to walk_page_range_novma(). Now we have

walk_page_range
walk_page_vma
walk_page_range_novma
walk_page_range_vma


-- 
Thanks,

David / dhildenb