linux-kernel - Re: [PATCH v2 3/4] mm/migration: return errno when isolate_huge

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Date:   Mon, 9 May 2022 11:23:59 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     Muchun Song <songmuchun@...edance.com>
CC:     <akpm@...ux-foundation.org>, <mike.kravetz@...cle.com>,
        <naoya.horiguchi@....com>, <ying.huang@...el.com>, <hch@....de>,
        <dhowells@...hat.com>, <cl@...ux.com>, <david@...hat.com>,
        <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/4] mm/migration: return errno when isolate_huge_page
 failed

On 2022/4/29 19:36, Muchun Song wrote:
> On Mon, Apr 25, 2022 at 09:27:22PM +0800, Miaohe Lin wrote:
>> We might fail to isolate huge page due to e.g. the page is under migration
>> which cleared HPageMigratable. So we should return -EBUSY in this case
>> rather than always return 1 which could confuse the user. Also we make
>> the prototype of isolate_huge_page consistent with isolate_lru_page to
>> improve the readability.
>>
>> Fixes: e8db67eb0ded ("mm: migrate: move_pages() supports thp migration")
>> Suggested-by: Huang Ying <ying.huang@...el.com>
>> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
>> ---
>>  include/linux/hugetlb.h |  6 +++---
>>  mm/gup.c                |  2 +-
>>  mm/hugetlb.c            | 11 +++++------
>>  mm/memory-failure.c     |  2 +-
>>  mm/mempolicy.c          |  2 +-
>>  mm/migrate.c            |  5 +++--
>>  6 files changed, 14 insertions(+), 14 deletions(-)
>>
>> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
>> index 04f0186b089b..306d6ef3fa22 100644
>> --- a/include/linux/hugetlb.h
>> +++ b/include/linux/hugetlb.h
>> @@ -170,7 +170,7 @@ bool hugetlb_reserve_pages(struct inode *inode, long from, long to,
>>  						vm_flags_t vm_flags);
>>  long hugetlb_unreserve_pages(struct inode *inode, long start, long end,
>>  						long freed);
>> -bool isolate_huge_page(struct page *page, struct list_head *list);
>> +int isolate_huge_page(struct page *page, struct list_head *list);
>>  int get_hwpoison_huge_page(struct page *page, bool *hugetlb);
>>  int get_huge_page_for_hwpoison(unsigned long pfn, int flags);
>>  void putback_active_hugepage(struct page *page);
>> @@ -376,9 +376,9 @@ static inline pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr,
>>  	return NULL;
>>  }
>>  
>> -static inline bool isolate_huge_page(struct page *page, struct list_head *list)
>> +static inline int isolate_huge_page(struct page *page, struct list_head *list)
> 
> Since you already touched all the call sites, how about renaming this
> to hugetlb_isolate()? I've always felt that huge_page is not a
> straightforward and clear name since we also have another type of
> huge page (THP).  I think hugetlb is more specific.
> 

Sorry for late respond. This suggestion looks good to me. But is isolate_hugetlb more suitable?
This could make it more consistent with isolate_lru_page? What do you think?

Thanks!

> Thanks.
>  
> .
>