Re: [PATCH v3 2/6] mm: hugetlbfs: fix cannot migrate the fallocated HugeTLB page

Michal Hocko
2021-01-12T09:45:52Z

On Sun 10-01-21 20:40:13, Muchun Song wrote:
> If a new hugetlb page is allocated during fallocate it will not be
> marked as active (set_page_huge_active) which will result in a later
> isolate_huge_page failure when the page migration code would like to
> move that page. Such a failure would be unexpected and wrong.
>
> Only export set_page_huge_active, just leave clear_page_huge_active
> as static. Because there are no external users.
>
> Fixes: 70c3547e36f5 (hugetlbfs: add hugetlbfs_fallocate())
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> Cc: stable@vger.kernel.org

Acked-by: Michal Hocko <mhocko@suse.com>

Thanks!

> ---
> fs/hugetlbfs/inode.c | 3 ++-
> include/linux/hugetlb.h | 2 ++
> mm/hugetlb.c | 2 +-
> 3 files changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
> index b5c109703daa..21c20fd5f9ee 100644
> --- a/fs/hugetlbfs/inode.c
> +++ b/fs/hugetlbfs/inode.c
> @@ -735,9 +735,10 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset,
>
> mutex_unlock(&hugetlb_fault_mutex_table[hash]);
>
> + set_page_huge_active(page);
> /*
> * unlock_page because locked by add_to_page_cache()
> - * page_put due to reference from alloc_huge_page()
> + * put_page() due to reference from alloc_huge_page()
> */
> unlock_page(page);
> put_page(page);
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index ebca2ef02212..b5807f23caf8 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -770,6 +770,8 @@ static inline void huge_ptep_modify_prot_commit(struct vm_area_struct *vma,
> }
> #endif
>
> +void set_page_huge_active(struct page *page);
> +
> #else /* CONFIG_HUGETLB_PAGE */
> struct hstate {};
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 1f3bf1710b66..4741d60f8955 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1348,7 +1348,7 @@ bool page_huge_active(struct page *page)
> }
>
> /* never called for tail page */
> -static void set_page_huge_active(struct page *page)
> +void set_page_huge_active(struct page *page)
> {
> VM_BUG_ON_PAGE(!PageHeadHuge(page), page);
> SetPagePrivate(&page[1]);
> --
> 2.11.0

--
Michal Hocko
SUSE Labs