Re: [PATCH v2 03/11] mm: Return the address from page_mapped_in_vma()

[Oscar Salvador <osalvador@suse.de>]

On Mon, Apr 08, 2024 at 08:42:21PM +0100, Matthew Wilcox (Oracle) wrote:
> The only user of this function calls page_address_in_vma() immediately
> after page_mapped_in_vma() calculates it and uses it to return true/false.
> Return the address instead, allowing memory-failure to skip the call
> to page_address_in_vma().
> 
> Acked-by: Miaohe Lin <linmiaohe@huawei.com>
> Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
> ---
>  mm/page_vma_mapped.c | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c
> index 53b8868ede61..48bfc17934cd 100644
> --- a/mm/page_vma_mapped.c
> +++ b/mm/page_vma_mapped.c
> @@ -319,9 +319,10 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw)
>   * @page: the page to test
>   * @vma: the VMA to test
>   *
> - * Returns 1 if the page is mapped into the page tables of the VMA, 0
> - * if the page is not mapped into the page tables of this VMA.  Only
> - * valid for normal file or anonymous VMAs.
> + * Return: The address the page is mapped at if the page is in the range
> + * covered by the VMA and present in the page table.  If the page is
> + * outside the VMA or not present, returns -EFAULT.
> + * Only valid for normal file or anonymous VMAs.

I am probably missing something here but I am confused.
Now we either return -EFAULT or the address.

But page_vma_mapped_walk() gets called from collect_procs_anon() like
this:

if (!page_mapped_in_vma(page, vma))

so that is not gonna work the way we want?
Should not that be converted to

 if (page_mapped_in_vma(page, vma) == -EFAULT)

?

-- 
Oscar Salvador
SUSE Labs