linux-kernel - Re: [PATCH v3 1/4] mm: change to return bool for folio_isolate

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Message-ID: <Y+z7tT6amGO4wNf4@casper.infradead.org>
Date:   Wed, 15 Feb 2023 15:35:17 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     Baolin Wang <baolin.wang@...ux.alibaba.com>
Cc:     akpm@...ux-foundation.org, 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, david@...hat.com, osalvador@...e.de,
        mike.kravetz@...cle.com, damon@...ts.linux.dev,
        cgroups@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/4] mm: change to return bool for folio_isolate_lru()

On Wed, Feb 15, 2023 at 06:39:34PM +0800, Baolin Wang wrote:
> Now the folio_isolate_lru() did not return a boolean value to indicate
> isolation success or not, however below code checking the return value
> can make people think that it was a boolean success/failure thing, which
> makes people easy to make mistakes (see the fix patch[1]).
> 
> if (folio_isolate_lru(folio))
> 	continue;
> 
> Thus it's better to check the negative error value expilictly returned by
> folio_isolate_lru(), which makes code more clear per Linus's suggestion[2].
> Moreover Matthew suggested we can convert the isolation functions to return
> a boolean[3], since most users did not care about the negative error value,
> and can also remove the confusing of checking return value.
> 
> So this patch converts the folio_isolate_lru() to return a boolean value,
> which means return 'true' to indicate the folio isolation is successful,
> and 'false' means a failure to isolation. Meanwhile changing all users'
> logic of checking the isolation state.
> 
> No functional changes intended.
> 
> [1] https://lore.kernel.org/all/20230131063206.28820-1-Kuan-Ying.Lee@mediatek.com/T/#u
> [2] https://lore.kernel.org/all/CAHk-=wiBrY+O-4=2mrbVyxR+hOqfdJ=Do6xoucfJ9_5az01L4Q@mail.gmail.com/
> [3] https://lore.kernel.org/all/Y+sTFqwMNAjDvxw3@casper.infradead.org/
> 
> Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
> Reviewed-by: SeongJae Park <sj@...nel.org>
> Acked-by: David Hildenbrand <david@...hat.com>

Reviewed-by: Matthew Wilcox (Oracle) <willy@...radead.org>