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

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Message-ID: <YmvNqWhC0uBwJ2yF@FVFYT0MHHV2J.usts.net>
Date:   Fri, 29 Apr 2022 19:36:09 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     Miaohe Lin <linmiaohe@...wei.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 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.

Thanks.