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

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Message-ID: <Yz3sIY5Njzda3XSA@x1n>
Date:   Wed, 5 Oct 2022 16:42:09 -0400
From:   Peter Xu <peterx@...hat.com>
To:     David Hildenbrand <david@...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 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?

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.

-- 
Peter Xu