linux-kernel - Re: [PATCH 2/6] mm/page_io: use a folio in sio_read

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Message-ID: <526ccc57-a1c3-455a-3f4a-34cd5c517bc7@huawei.com>
Date:   Wed, 19 Jul 2023 15:47:19 +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>,
        Kent Overstreet <kent.overstreet@...il.com>
Subject: Re: [PATCH 2/6] mm/page_io: use a folio in sio_read_complete()

On 2023/7/19 0:21, Matthew Wilcox wrote:

> On Tue, Jul 18, 2023 at 08:58:17PM +0800, zhangpeng (AS) wrote:
>> On 2023/7/17 21:40, Matthew Wilcox wrote:
>>
>>> On Mon, Jul 17, 2023 at 09:25:58PM +0800, Peng Zhang wrote:
>>>> +++ b/mm/page_io.c
>>>> @@ -406,19 +406,19 @@ static void sio_read_complete(struct kiocb *iocb, long ret)
>>>>    	if (ret == sio->len) {
>>>>    		for (p = 0; p < sio->pages; p++) {
>>>> -			struct page *page = sio->bvec[p].bv_page;
>>>> +			struct folio *folio = page_folio(sio->bvec[p].bv_page);
>>>> -			SetPageUptodate(page);
>>>> -			unlock_page(page);
>>>> +			folio_mark_uptodate(folio);
>>>> +			folio_unlock(folio);
>>>>    		}
>>> I'm kind of shocked this works today.  Usually bvecs coalesce adjacent
>>> pages into a single entry, so you need to use a real iterator like
>>> bio_for_each_folio_all() to extract individual pages from a bvec.
>>> Maybe the sio bvec is constructed inefficiently.
>>>
>>> I think Kent had some bvec folio iterators in progress?
>> I'll convert bio_first_page_all() to bio_first_folio_all() in a v2.
> That isn't my point at all.  What I'm saying is that when you call a
> function like bio_add_folio(), if @folio is physically adjacent to the
> immediately prior folio already in the bio, it will extend the bv_len
> instead of adding the new folio to the bvec.  Maybe there's nothing like
> that for sio.

Thanks for your reply! I got it.

-- 
Best Regards,
Peng