Re: [PATCH 3/4] mm: hugetlb_vmemmap: move PageVmemmapSelfHosted() check to split_vmemmap_huge_pmd()

Mike Kravetz
2023-12-04T23:28:31Z

On 11/27/23 16:46, Muchun Song wrote:
> To check a page whether it is self-hosted needs to traverse the page table (e.g.
> pmd_off_k()), however, we already have done this in the next calling of
> vmemmap_remap_range(). Moving PageVmemmapSelfHosted() check to vmemmap_pmd_entry()
> could simplify the code a bit.
>
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> ---
> mm/hugetlb_vmemmap.c | 70 +++++++++++++++-----------------------------
> 1 file changed, 24 insertions(+), 46 deletions(-)
>
> diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
> index ef14356855d13..ce920ca6c90ee 100644
> --- a/mm/hugetlb_vmemmap.c
> +++ b/mm/hugetlb_vmemmap.c
> @@ -95,6 +95,7 @@ static int vmemmap_split_pmd(pmd_t *pmd, struct page *head, unsigned long start,
> static int vmemmap_pmd_entry(pmd_t *pmd, unsigned long addr,
> unsigned long next, struct mm_walk *walk)
> {
> + int ret = 0;
> struct page *head;
> struct vmemmap_remap_walk *vmemmap_walk = walk->private;
>
> @@ -104,9 +105,30 @@ static int vmemmap_pmd_entry(pmd_t *pmd, unsigned long addr,
>
> spin_lock(&init_mm.page_table_lock);
> head = pmd_leaf(*pmd) ? pmd_page(*pmd) : NULL;

I was going to ask why you dropped the:
if (IS_ENABLED(CONFIG_MEMORY_HOTPLUG))
However, without the extra page table reads it really is not necessary.

Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
--
Mike Kravetz