diff mbox series

[v1,04/11] mm: thp: simlify total_mapcount()

Message ID 20211217113049.23850-5-david@redhat.com (mailing list archive)
State New
Headers show
Series mm: COW fixes part 1: fix the COW security issue for THP and hugetlb | expand

Commit Message

David Hildenbrand Dec. 17, 2021, 11:30 a.m. UTC 
Let's simplify a bit, returning for PageHuge() early and using
head_compound_page() as we are only getting called for HEAD pages.

Note the VM_BUG_ON_PAGE(PageTail(page), page) check at the beginning of
total_mapcount().

This is a preparation for further changes.

Reviewed-by: Peter Xu <peterx@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
 mm/huge_memory.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

Comments

Yang Shi Dec. 17, 2021, 7:12 p.m. UTC | #1 
On Fri, Dec 17, 2021 at 3:33 AM David Hildenbrand <david@redhat.com> wrote:
>
> Let's simplify a bit, returning for PageHuge() early and using
> head_compound_page() as we are only getting called for HEAD pages.
>
> Note the VM_BUG_ON_PAGE(PageTail(page), page) check at the beginning of
> total_mapcount().
>
> This is a preparation for further changes.
>
> Reviewed-by: Peter Xu <peterx@redhat.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>

Reviewed-by: Yang Shi <shy828301@gmail.com>

> ---
>  mm/huge_memory.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 4751d03947da..826cabcad11a 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -2506,12 +2506,11 @@ int total_mapcount(struct page *page)
>
>         if (likely(!PageCompound(page)))
>                 return atomic_read(&page->_mapcount) + 1;
> +       if (PageHuge(page))
> +               return head_compound_mapcount(page);
>
> -       compound = compound_mapcount(page);
>         nr = compound_nr(page);
> -       if (PageHuge(page))
> -               return compound;
> -       ret = compound;
> +       ret = compound = head_compound_mapcount(page);
>         for (i = 0; i < nr; i++)
>                 ret += atomic_read(&page[i]._mapcount) + 1;
>         /* File pages has compound_mapcount included in _mapcount */
> --
> 2.31.1
>
Kirill A. Shutemov Dec. 18, 2021, 2:35 p.m. UTC | #2 
On Fri, Dec 17, 2021 at 12:30:42PM +0100, David Hildenbrand wrote:
> Let's simplify a bit, returning for PageHuge() early and using
> head_compound_page() as we are only getting called for HEAD pages.
> 
> Note the VM_BUG_ON_PAGE(PageTail(page), page) check at the beginning of
> total_mapcount().
> 
> This is a preparation for further changes.
> 
> Reviewed-by: Peter Xu <peterx@redhat.com>
> Signed-off-by: David Hildenbrand <david@redhat.com>

Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
diff mbox series

Patch

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 4751d03947da..826cabcad11a 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2506,12 +2506,11 @@  int total_mapcount(struct page *page)
 
 	if (likely(!PageCompound(page)))
 		return atomic_read(&page->_mapcount) + 1;
+	if (PageHuge(page))
+		return head_compound_mapcount(page);
 
-	compound = compound_mapcount(page);
 	nr = compound_nr(page);
-	if (PageHuge(page))
-		return compound;
-	ret = compound;
+	ret = compound = head_compound_mapcount(page);
 	for (i = 0; i < nr; i++)
 		ret += atomic_read(&page[i]._mapcount) + 1;
 	/* File pages has compound_mapcount included in _mapcount */