linux-kernel - Re: [PATCH v4 35/36] mm: Convert do_set_pte() to set_pte

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Date:   Tue, 21 Mar 2023 13:13:29 +0800
From:   Yin Fengwei <fengwei.yin@...el.com>
To:     Matthew Wilcox <willy@...radead.org>
CC:     Ryan Roberts <ryan.roberts@....com>, <linux-arch@...r.kernel.org>,
        <will@...nel.org>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 35/36] mm: Convert do_set_pte() to set_pte_range()

On 3/20/23 22:08, Matthew Wilcox wrote:
> On Mon, Mar 20, 2023 at 09:38:55PM +0800, Yin, Fengwei wrote:
>> Thanks a lot to Ryan for helping to test the debug patch I made.
>>
>> Ryan confirmed that the following change could fix the kernel build regression:
>> diff --git a/mm/filemap.c b/mm/filemap.c
>> index db86e459dde6..343d6ff36b2c 100644
>> --- a/mm/filemap.c
>> +++ b/mm/filemap.c
>> @@ -3557,7 +3557,7 @@ vm_fault_t filemap_map_pages(struct vm_fault *vmf,
>>
>>                  ret |= filemap_map_folio_range(vmf, folio,
>>                                  xas.xa_index - folio->index, addr, nr_pages);
>> -               xas.xa_index += nr_pages;
>> +               xas.xa_index += folio_test_large(folio) ? nr_pages : 0;
>>
>>                  folio_unlock(folio);
>>                  folio_put(folio);
>>
>> I will make upstream-able change as "xas.xa_index += nr_pages - 1;"
> 
> Thanks to both of you!
> 
> Really, we shouldn't need to interfere with xas.xa_index at all.
> Does this work?
Yes. This works perfectly in my side. Thanks.

Regards
Yin, Fengwei

> 
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 8e4f95c5b65a..e40c967dde5f 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -3420,10 +3420,10 @@ static bool filemap_map_pmd(struct vm_fault *vmf, struct folio *folio,
>   	return false;
>   }
>   
> -static struct folio *next_uptodate_page(struct folio *folio,
> -				       struct address_space *mapping,
> -				       struct xa_state *xas, pgoff_t end_pgoff)
> +static struct folio *next_uptodate_folio(struct xa_state *xas,
> +		struct address_space *mapping, pgoff_t end_pgoff)
>   {
> +	struct folio *folio = xas_next_entry(xas, end_pgoff);
>   	unsigned long max_idx;
>   
>   	do {
> @@ -3461,22 +3461,6 @@ static struct folio *next_uptodate_page(struct folio *folio,
>   	return NULL;
>   }
>   
> -static inline struct folio *first_map_page(struct address_space *mapping,
> -					  struct xa_state *xas,
> -					  pgoff_t end_pgoff)
> -{
> -	return next_uptodate_page(xas_find(xas, end_pgoff),
> -				  mapping, xas, end_pgoff);
> -}
> -
> -static inline struct folio *next_map_page(struct address_space *mapping,
> -					 struct xa_state *xas,
> -					 pgoff_t end_pgoff)
> -{
> -	return next_uptodate_page(xas_next_entry(xas, end_pgoff),
> -				  mapping, xas, end_pgoff);
> -}
> -
>   /*
>    * Map page range [start_page, start_page + nr_pages) of folio.
>    * start_page is gotten from start by folio_page(folio, start)
> @@ -3552,7 +3536,7 @@ vm_fault_t filemap_map_pages(struct vm_fault *vmf,
>   	int nr_pages = 0;
>   
>   	rcu_read_lock();
> -	folio = first_map_page(mapping, &xas, end_pgoff);
> +	folio = next_uptodate_folio(&xas, mapping, end_pgoff);
>   	if (!folio)
>   		goto out;
>   
> @@ -3574,11 +3558,11 @@ vm_fault_t filemap_map_pages(struct vm_fault *vmf,
>   
>   		ret |= filemap_map_folio_range(vmf, folio,
>   				xas.xa_index - folio->index, addr, nr_pages);
> -		xas.xa_index += nr_pages;
>   
>   		folio_unlock(folio);
>   		folio_put(folio);
> -	} while ((folio = next_map_page(mapping, &xas, end_pgoff)) != NULL);
> +		folio = next_uptodate_folio(&xas, mapping, end_pgoff);
> +	} while (folio);
>   	pte_unmap_unlock(vmf->pte, vmf->ptl);
>   out:
>   	rcu_read_unlock();
> 
>> Ryan and I also identify some other changes needed. I am not sure how to
>> integrate those changes to this series. Maybe an add-on patch after this
>> series? Thanks.
> 
> Up to you; I'm happy to integrate fixup patches into the current series
> or add on new ones.