linux-kernel - Re: [PATCH v2 0/4] Change the return value for page isolation functions

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Message-ID: <5064ee08-792f-14f2-6f2d-26e81af8a239@redhat.com>
Date:   Tue, 14 Feb 2023 18:52:49 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Baolin Wang <baolin.wang@...ux.alibaba.com>,
        akpm@...ux-foundation.org
Cc:     torvalds@...ux-foundation.org, sj@...nel.org, hannes@...xchg.org,
        mhocko@...nel.org, roman.gushchin@...ux.dev, shakeelb@...gle.com,
        muchun.song@...ux.dev, naoya.horiguchi@....com,
        linmiaohe@...wei.com, osalvador@...e.de, mike.kravetz@...cle.com,
        willy@...radead.org, damon@...ts.linux.dev,
        cgroups@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 0/4] Change the return value for page isolation
 functions

On 14.02.23 14:59, Baolin Wang wrote:
> Now the page isolation functions did not return a boolean to indicate
> success or not, instead it will return a negative error when failed
> to isolate a page. So below code used in most places seem a boolean
> success/failure thing, which can confuse people whether the isolation
> is successful.
> 
> if (folio_isolate_lru(folio))
>          continue;
> 
> Moreover the page isolation functions only return 0 or -EBUSY, and
> most users did not care about the negative error except for few users,
> thus we can convert all page isolation functions to return a boolean
> value, which can remove the confusion to make code more clear.
> 
> No functional changes intended in this patch series.
> 
> Changes from v1:
>   - Convert all isolation functions to return bool.

Acked-by: David Hildenbrand <david@...hat.com>

Although it's controversial if

if (!ret)
	ret = -EBUSY;
else
	ret = 0;

is really appealing to the readers eye :)

ret = ret ? 0 : -EBUSY;

It's still confusing.

would be better as

ret = isolated ? 0 : -EBUSY;

IOW, not reusing the "int ret" variable.

-- 
Thanks,

David / dhildenb