linux-kernel - Re: [PATCH 1/6] mm/page_io: use a folio in __end_swap_bio

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Message-ID: <df29af76-fc8f-b4f1-4a32-a200b5d4ba31@huawei.com>
Date:   Tue, 18 Jul 2023 20:56:16 +0800
From:   "zhangpeng (AS)" <zhangpeng362@...wei.com>
To:     Matthew Wilcox <willy@...radead.org>
CC:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <sidhartha.kumar@...cle.com>, <akpm@...ux-foundation.org>,
        <wangkefeng.wang@...wei.com>, <sunnanyong@...wei.com>
Subject: Re: [PATCH 1/6] mm/page_io: use a folio in __end_swap_bio_read()

On 2023/7/17 21:34, Matthew Wilcox wrote:

> On Mon, Jul 17, 2023 at 09:25:57PM +0800, Peng Zhang wrote:
>> +++ b/mm/page_io.c
>> @@ -58,18 +58,18 @@ static void end_swap_bio_write(struct bio *bio)
>>   
>>   static void __end_swap_bio_read(struct bio *bio)
>>   {
>> -	struct page *page = bio_first_page_all(bio);
>> +	struct folio *folio = page_folio(bio_first_page_all(bio));
> Should we have a bio_first_folio_all()?  It wouldn't save any calls to
> compound_head(), but it's slightly easier to use.

Yes, I'll convert bio_first_page_all() to bio_first_folio_all() in a v2.
Thanks.

>>   	if (bio->bi_status) {
>> -		SetPageError(page);
>> -		ClearPageUptodate(page);
>> +		folio_set_error(folio);
> I appreciate this is a 1:1 conversion, but maybe we could think about
> this a bit.  Is there anybody who checks the
> PageError()/folio_test_error() for this page/folio?

Maybe wait_dev_supers() checks the PageError() after write_dev_supers()
in fs/btrfs/disk-io.c?

>> +		folio_clear_uptodate(folio);
> Similarly ... surely the folio is already !uptodate, so we don't need to
> clear the flag?

Indeed, the folio is already !uptodate. I'll drop this line in a v2.
Thanks for your feedback.

-- 
Best Regards,
Peng