linux-kernel - Re: [PATCH v5 4/8] hugetlb: create remove_hugetlb

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Date:   Mon, 12 Apr 2021 11:03:56 -0700
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     Oscar Salvador <osalvador@...e.de>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <guro@...com>, Michal Hocko <mhocko@...e.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        David Hildenbrand <david@...hat.com>,
        Muchun Song <songmuchun@...edance.com>,
        David Rientjes <rientjes@...gle.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Matthew Wilcox <willy@...radead.org>,
        HORIGUCHI NAOYA <naoya.horiguchi@....com>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
        Waiman Long <longman@...hat.com>, Peter Xu <peterx@...hat.com>,
        Mina Almasry <almasrymina@...gle.com>,
        Hillf Danton <hdanton@...a.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Barry Song <song.bao.hua@...ilicon.com>,
        Will Deacon <will@...nel.org>
Subject: Re: [PATCH v5 4/8] hugetlb: create remove_hugetlb_page() to separate
 functionality

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@...cle.com>
>> Acked-by: Michal Hocko <mhocko@...e.com>
>> Reviewed-by: Miaohe Lin <linmiaohe@...wei.com>
>> Reviewed-by: Muchun Song <songmuchun@...edance.com>
> 
> Reviewed-by: Oscar Salvador <osalvador@...e.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