Re: [PATCH v2 02/10] mm/hugetlb: Don't wait for migration entry during follow page

From: John Hubbard
Date: Wed Dec 07 2022 - 17:05:38 EST


On 12/7/22 12:30, Peter Xu wrote:
That's what the code does with !hugetlb pages, so we should logically do
the same for hugetlb, so migration entry will also be treated as no page.

This reasoning make good sense to me. I looked again at the follow_page*()
paths and just double-checked that this is accurate, and it is.


This is probably also the last piece in follow_page code that may sleep,
the last one should be removed in cf994dd8af27 ("mm/gup: remove
FOLL_MIGRATION", 2022-11-16).

Reviewed-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
Signed-off-by: Peter Xu <peterx@xxxxxxxxxx>
---
mm/hugetlb.c | 11 -----------
1 file changed, 11 deletions(-)

Reviewed-by: John Hubbard <jhubbard@xxxxxxxxxx>

thanks,
--
John Hubbard
NVIDIA


diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 1088f2f41c88..c8a6673fe5b4 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -6232,7 +6232,6 @@ struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma,
if (WARN_ON_ONCE(flags & FOLL_PIN))
return NULL;
-retry:
pte = huge_pte_offset(mm, haddr, huge_page_size(h));
if (!pte)
return NULL;
@@ -6255,16 +6254,6 @@ struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma,
page = NULL;
goto out;
}
- } else {
- if (is_hugetlb_entry_migration(entry)) {
- spin_unlock(ptl);
- __migration_entry_wait_huge(pte, ptl);
- goto retry;
- }
- /*
- * hwpoisoned entry is treated as no_page_table in
- * follow_page_mask().
- */
}
out:
spin_unlock(ptl);