Re: [PATCH] mm/memory_failure: Fix the missing pte_unmap() call

[Qi Zheng]

On 9/24/21 7:17 AM, Andrew Morton wrote:
> On Thu, 23 Sep 2021 20:26:42 +0800 Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx> wrote:
>
> > The paired pte_unmap() call is missing before the
> > dev_pagemap_mapping_shift() returns. So fix it.
> >
> > ...
> >
> > --- a/mm/memory-failure.c
> > +++ b/mm/memory-failure.c
> > @@ -306,6 +306,7 @@ static unsigned long dev_pagemap_mapping_shift(struct page *page,
> >   		struct vm_area_struct *vma)
> >   {
> >   	unsigned long address = vma_address(page, vma);
> > +	unsigned long ret = 0;
> >   	pgd_t *pgd;
> >   	p4d_t *p4d;
> >   	pud_t *pud;
> > @@ -330,10 +331,12 @@ static unsigned long dev_pagemap_mapping_shift(struct page *page,
> >   		return PMD_SHIFT;
> >   	pte = pte_offset_map(pmd, address);
> >   	if (!pte_present(*pte))
> > -		return 0;
> > +		goto unmap;
> >   	if (pte_devmap(*pte))
> > -		return PAGE_SHIFT;
> > -	return 0;
> > +		ret = PAGE_SHIFT;
> > +unmap:
> > +	pte_unmap(pte);
> > +	return ret;
> >   }
> >   
>
> This is neater?

Yes, and I see this neater version has merged into your mm tree,
thanks. :)

> +++ a/mm/memory-failure.c
> @@ -330,11 +330,8 @@ static unsigned long dev_pagemap_mapping
>   	if (pmd_devmap(*pmd))
>   		return PMD_SHIFT;
>   	pte = pte_offset_map(pmd, address);
> -	if (!pte_present(*pte))
> -		goto unmap;
> -	if (pte_devmap(*pte))
> +	if (pte_present(*pte) && pte_devmap(*pte))
>   		ret = PAGE_SHIFT;
> -unmap:
>   	pte_unmap(pte);
>   	return ret;
>   }
> _