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

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Message-ID: <cca8918f-e8c2-8f2c-cbb9-5797631ab3eb@linux.alibaba.com>
Date:   Thu, 16 Feb 2023 10:04:29 +0800
From:   Baolin Wang <baolin.wang@...ux.alibaba.com>
To:     SeongJae Park <sj@...nel.org>
Cc:     akpm@...ux-foundation.org, torvalds@...ux-foundation.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 2/16/2023 4:25 AM, SeongJae Park wrote:
> 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.

Yes, good catch. And I see Andrew has helped to do this (Thanks Andrew).

Thanks for reviewing.