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

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Date:   Mon, 9 May 2022 12:21:06 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     Miaohe Lin <linmiaohe@...wei.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        HORIGUCHI NAOYA(堀口 直也) 
        <naoya.horiguchi@....com>, Huang Ying <ying.huang@...el.com>,
        Christoph Hellwig <hch@....de>, dhowells@...hat.com,
        Christoph Lameter <cl@...ux.com>,
        David Hildenbrand <david@...hat.com>,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 3/4] mm/migration: return errno when isolate_huge_page failed

On Mon, May 9, 2022 at 11:24 AM Miaohe Lin <linmiaohe@...wei.com> wrote:
>
> 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?
>

There is also a function named folio_isolate_lru(). My initial consideration was
making it consistent with folio_isolate_lru(). isolate_hugetlb looks good to me
as well.

Thanks.