2022-10-21 16:56:57

by James Houghton

Subject: [RFC PATCH v2 19/47] hugetlb: make hugetlb_follow_page_mask HGM-enabled

The change here is very simple: do a high-granularity walk.

Signed-off-by: James Houghton <[email protected]>
---
mm/hugetlb.c | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index d76ab32fb6d3..5783a8307a77 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -6408,6 +6408,7 @@ struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma,
struct page *page = NULL;
spinlock_t *ptl;
pte_t *pte, entry;
+ struct hugetlb_pte hpte;

/*
* FOLL_PIN is not supported for follow_page(). Ordinary GUP goes via
@@ -6429,9 +6430,22 @@ struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma,
return NULL;
}

- ptl = huge_pte_lock(h, mm, pte);
+retry_walk:
+ hugetlb_pte_populate(&hpte, pte, huge_page_shift(h),
+ hpage_size_to_level(huge_page_size(h)));
+ hugetlb_hgm_walk(mm, vma, &hpte, address,
+ PAGE_SIZE,
+ /*stop_at_none=*/true);
+
+ ptl = hugetlb_pte_lock(mm, &hpte);
entry = huge_ptep_get(pte);
if (pte_present(entry)) {
+ if (unlikely(!hugetlb_pte_present_leaf(&hpte, entry))) {
+ /* We raced with someone splitting from under us. */
+ spin_unlock(ptl);
+ goto retry_walk;
+ }
+
page = pte_page(entry) +
((address & ~huge_page_mask(h)) >> PAGE_SHIFT);
/*
--
2.38.0.135.g90850a2211-goog

2022-12-16 00:43:11

by Mike Kravetz

Subject: Re: [RFC PATCH v2 19/47] hugetlb: make hugetlb_follow_page_mask HGM-enabled

On 10/21/22 16:36, James Houghton wrote:
> The change here is very simple: do a high-granularity walk.
>
> Signed-off-by: James Houghton <[email protected]>
> ---
> mm/hugetlb.c | 16 +++++++++++++++-
> 1 file changed, 15 insertions(+), 1 deletion(-)

Looks fine

--
Mike Kravetz