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Subject: Re: [PATCH v5 4/8] hugetlb: create remove_hugetlb_page() to separate
 functionality
To:     Oscar Salvador <osalvador@suse.de>
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Roman Gushchin <guro@fb.com>, Michal Hocko <mhocko@suse.com>,
        Shakeel Butt <shakeelb@google.com>,
        David Hildenbrand <david@redhat.com>,
        Muchun Song <songmuchun@bytedance.com>,
        David Rientjes <rientjes@google.com>,
        Miaohe Lin <linmiaohe@huawei.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Matthew Wilcox <willy@infradead.org>,
        HORIGUCHI NAOYA <naoya.horiguchi@nec.com>,
        "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>,
        Waiman Long <longman@redhat.com>, Peter Xu <peterx@redhat.com>,
        Mina Almasry <almasrymina@google.com>,
        Hillf Danton <hdanton@sina.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>,
        Barry Song <song.bao.hua@hisilicon.com>,
        Will Deacon <will@kernel.org>
References: <20210409205254.242291-1-mike.kravetz@oracle.com>
 <20210409205254.242291-5-mike.kravetz@oracle.com>
 <20210412073307.GB27818@linux>
From:   Mike Kravetz <mike.kravetz@oracle.com>
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Date:   Mon, 12 Apr 2021 11:03:56 -0700
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On 4/12/21 12:33 AM, Oscar Salvador wrote:
> On Fri, Apr 09, 2021 at 01:52:50PM -0700, Mike Kravetz wrote:
>> The new remove_hugetlb_page() routine is designed to remove a hugetlb
>> page from hugetlbfs processing.  It will remove the page from the active
>> or free list, update global counters and set the compound page
>> destructor to NULL so that PageHuge() will return false for the 'page'.
>> After this call, the 'page' can be treated as a normal compound page or
>> a collection of base size pages.
>>
>> update_and_free_page no longer decrements h->nr_huge_pages{_node} as
>> this is performed in remove_hugetlb_page.  The only functionality
>> performed by update_and_free_page is to free the base pages to the lower
>> level allocators.
>>
>> update_and_free_page is typically called after remove_hugetlb_page.
>>
>> remove_hugetlb_page is to be called with the hugetlb_lock held.
>>
>> Creating this routine and separating functionality is in preparation for
>> restructuring code to reduce lock hold times.  This commit should not
>> introduce any changes to functionality.
>>
>> Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
>> Acked-by: Michal Hocko <mhocko@suse.com>
>> Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
>> Reviewed-by: Muchun Song <songmuchun@bytedance.com>
> 
> Reviewed-by: Oscar Salvador <osalvador@suse.de>
> 
> A "nit" below:
> 
>>  static void update_and_free_page(struct hstate *h, struct page *page)
>>  {
>>  	int i;
>> @@ -1334,8 +1369,6 @@ static void update_and_free_page(struct hstate *h, struct page *page)
> 
> After this, update_and_free_page()'s job is to reset subpage's flags and free
> the page.
> Maybe we want to rename that function at some point, or maybe not as "update" might
> already imply that. Just speaking out loud.

Thanks Oscar,

I did not think about a name change as the routine is still "updating"
subpages before freeing.  We can certainly keep this in mind in the future,
especially if there are more functionality changes.
-- 
Mike Kravetz