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Date:   Wed, 19 Jul 2023 15:46:52 +0800
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Subject: Re: [PATCH 1/6] mm/page_io: use a folio in __end_swap_bio_read()
To:     Matthew Wilcox <willy@infradead.org>
CC:     <linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>,
        <sidhartha.kumar@oracle.com>, <akpm@linux-foundation.org>,
        <wangkefeng.wang@huawei.com>, <sunnanyong@huawei.com>
References: <20230717132602.2202147-1-zhangpeng362@huawei.com>
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From:   "zhangpeng (AS)" <zhangpeng362@huawei.com>
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On 2023/7/19 0:16, Matthew Wilcox wrote:

> On Tue, Jul 18, 2023 at 08:56:16PM +0800, zhangpeng (AS) wrote:
>>>>    	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?
> How does _this_ folio end up in btrfs's write_dev_supers()?  This is a
> swap read.  The only folios which are swapped are anonymous and tmpfs.
> btrfs takes care of doing its own I/O.  wait_dev_supers() is looking
> for the error set in btrfs_end_super_write() which is the completion
> routine for write_dev_supers().  The pages involved there are attached
> to a btrfs address_space, not shmem or anon.

Thanks for your explanation!

Then I think nobody checks the PageError()/folio_test_error() for the page
in patch 1 and patch 2. I'll delete SetPageError() in a v2.

-- 
Best Regards,
Peng