linux-kernel - Re: [RFC PATCH 1/3] filemap: convert page_endio to folio

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Message-ID: <ea4a45b8-837d-ec60-8320-126346e49a42@samsung.com>
Date:   Tue, 21 Mar 2023 14:51:12 +0100
From:   Pankaj Raghav <p.raghav@...sung.com>
To:     Matthew Wilcox <willy@...radead.org>
CC:     Christoph Hellwig <hch@...radead.org>, <hubcap@...ibond.com>,
        <senozhatsky@...omium.org>, <martin@...ibond.com>,
        <minchan@...nel.org>, <viro@...iv.linux.org.uk>,
        <brauner@...nel.org>, <axboe@...nel.dk>,
        <akpm@...ux-foundation.org>, <linux-kernel@...r.kernel.org>,
        <linux-block@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>,
        <linux-mm@...ck.org>, <gost.dev@...sung.com>, <mcgrof@...nel.org>,
        <devel@...ts.orangefs.org>
Subject: Re: [RFC PATCH 1/3] filemap: convert page_endio to folio_endio

Hi Willy,

On 2023-03-17 17:14, Pankaj Raghav wrote:
> On 2023-03-17 16:31, Matthew Wilcox wrote:
>>> +
>>> +       while ((folio = readahead_folio(rac))) {
>>> +               folio_mark_uptodate(folio);
>>> +               folio_unlock(folio);
>>>         }
>>
>> readahead_folio() is a bit too heavy-weight for that, IMO.  I'd do this
>> as;
>>
>> 	while ((folio = readahead_folio(rac))) {
>> 		if (!ret)
>> 			folio_mark_uptodate(folio);
>> 		folio_unlock(folio);
>> 	}
>>
> 
> This looks good.
> 
>> (there's no need to call folio_set_error(), nor folio_clear_uptodate())
> 
> I am trying to understand why these calls are not needed for the error case.
> I see similar pattern, for e.g. in iomap_finish_folio_read() where we call these
> functions for the error case.
> 

I am planning to send the next version. It would be great if I can get a rationale for your
statement regarding not needing to call folio_set_error() or folio_clear_uptodate().

> If we don't need to call these anymore, can the mpage code also be shortened like this:
> 
> -static void mpage_end_io(struct bio *bio)
> +static void mpage_read_end_io(struct bio *bio)
>  {
> -       struct bio_vec *bv;
> -       struct bvec_iter_all iter_all;
> +       struct folio_iter fi;
> +       int err = blk_status_to_errno(bio->bi_status);
> 
> -       bio_for_each_segment_all(bv, bio, iter_all) {
> -               struct page *page = bv->bv_page;
> -               page_endio(page, bio_op(bio),
> -                          blk_status_to_errno(bio->bi_status));
> +       bio_for_each_folio_all(fi, bio) {
> +               struct folio *folio = fi.folio;
> +
> +               if (!err)
> +                       folio_mark_uptodate(folio);
> +               folio_unlock(folio);
> +       }
> +
> +       bio_put(bio);
> +}
> +
> +static void mpage_write_end_io(struct bio *bio)
> +{
> ....
> +