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Message-ID: <4d715585-413d-a506-1bc0-1f12a0aec716@gmail.com>
Date:   Wed, 14 Sep 2022 10:30:45 -0700
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Subject: Re: [PATCH 02/21] mm/hugetlb: correct max_huge_pages accounting on
 demote
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To:     Mike Kravetz <mike.kravetz@oracle.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Jonathan Corbet <corbet@lwn.net>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Frank Rowand <frowand.list@gmail.com>,
        Muchun Song <songmuchun@bytedance.com>,
        Mike Rapoport <rppt@kernel.org>,
        Christoph Hellwig <hch@lst.de>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Robin Murphy <robin.murphy@arm.com>,
        Borislav Petkov <bp@suse.de>,
        "Paul E. McKenney" <paulmck@kernel.org>,
        Neeraj Upadhyay <quic_neeraju@quicinc.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        Damien Le Moal <damien.lemoal@opensource.wdc.com>,
        Florian Fainelli <f.fainelli@gmail.com>,
        David Hildenbrand <david@redhat.com>, Zi Yan <ziy@nvidia.com>,
        Oscar Salvador <osalvador@suse.de>,
        Hari Bathini <hbathini@linux.ibm.com>,
        Kees Cook <keescook@chromium.org>,
        - <devicetree-spec@vger.kernel.org>,
        KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
        Mel Gorman <mgorman@suse.de>, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, devicetree@vger.kernel.org,
        linux-mm@kvack.org, iommu@lists.linux.dev
References: <20220913195508.3511038-1-opendmb@gmail.com>
 <20220913195508.3511038-3-opendmb@gmail.com> <YyIN+bpKdCb3JuuY@monkey>
From:   Doug Berger <opendmb@gmail.com>
In-Reply-To: <YyIN+bpKdCb3JuuY@monkey>
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On 9/14/2022 10:23 AM, Mike Kravetz wrote:
> On 09/13/22 12:54, Doug Berger wrote:
>> When demoting a hugepage to a smaller order, the number of pages
>> added to the target hstate will be the size of the large page
>> divided by the size of the smaller page.
>>
>> Fixes: 8531fc6f52f5 ("hugetlb: add hugetlb demote page support")
>> Signed-off-by: Doug Berger <opendmb@gmail.com>
>> ---
>>   mm/hugetlb.c | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
>> index e070b8593b37..79949893ac12 100644
>> --- a/mm/hugetlb.c
>> +++ b/mm/hugetlb.c
>> @@ -3472,7 +3472,8 @@ static int demote_free_huge_page(struct hstate *h, struct page *page)
>>   	 * based on pool changes for the demoted page.
>>   	 */
>>   	h->max_huge_pages--;
>> -	target_hstate->max_huge_pages += pages_per_huge_page(h);
>> +	target_hstate->max_huge_pages += pages_per_huge_page(h) /
>> +					 pages_per_huge_page(target_hstate);
>>   
>>   	return rc;
>>   }
> 
> This has already been fixed here,
> 
> https://lore.kernel.org/linux-mm/20220823030209.57434-2-linmiaohe@huawei.com/
> 
Excellent! Thanks for the pointer and sorry for the noise.
-Doug