linux-kernel - Re: [PATCH v3 3/4] mm: hugetlb: change to return bool for isolate

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Date:   Wed, 15 Feb 2023 20:25:48 +0000
From:   SeongJae Park <sj@...nel.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, willy@...radead.org,
        damon@...ts.linux.dev, cgroups@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 3/4] mm: hugetlb: change to return bool for isolate_hugetlb()

On Wed, 15 Feb 2023 18:39:36 +0800 Baolin Wang <baolin.wang@...ux.alibaba.com> wrote:

> Now the isolate_hugetlb() only returns 0 or -EBUSY, and most users did not
> care about the negative value, thus we can convert the isolate_hugetlb()
> to return a boolean value to make code more clear when checking the
> hugetlb isolation state. Moreover converts 2 users which will consider
> the negative value returned by isolate_hugetlb().
> 
> No functional changes intended.
> 
> Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
> Acked-by: David Hildenbrand <david@...hat.com>
> ---
[...]
>  include/linux/hugetlb.h |  6 +++---
>  mm/hugetlb.c            | 13 ++++++++-----
>  mm/memory-failure.c     |  2 +-
>  mm/mempolicy.c          |  2 +-
>  mm/migrate.c            |  7 +++----
>  5 files changed, 16 insertions(+), 14 deletions(-)
> 
[...]
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 3a01a9dbf445..16513cd23d5d 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -2925,13 +2925,16 @@ static int alloc_and_dissolve_hugetlb_folio(struct hstate *h,
>  		 */
>  		goto free_new;
>  	} else if (folio_ref_count(old_folio)) {
> +		bool isolated;
> +
>  		/*
>  		 * Someone has grabbed the folio, try to isolate it here.
>  		 * Fail with -EBUSY if not possible.
>  		 */
>  		spin_unlock_irq(&hugetlb_lock);
> -		ret = isolate_hugetlb(old_folio, list);
> +		isolated = isolate_hugetlb(old_folio, list);
>  		spin_lock_irq(&hugetlb_lock);
> +		ret = isolated ? 0 : -EBUSY;
>  		goto free_new;

Nit.  I'd personally prefer to set 'ret' before entering this critical section
to keep the section short, but this would be just a mean comment that wouldn't
worth request respin.


Thanks,
SJ

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