diff mbox series

[7/7] mm/thp: remap_page() is only needed on anonymous THP

Message ID alpine.LSU.2.11.2106011415430.2148@eggly.anvils (mailing list archive)
State New, archived
Headers show
Series mm/thp: fix THP splitting unmap BUGs and related | expand

Commit Message

Hugh Dickins June 1, 2021, 9:17 p.m. UTC 
THP splitting's unmap_page() only sets TTU_SPLIT_FREEZE when PageAnon,
and migration entries are only inserted when TTU_MIGRATION (unused here)
or TTU_SPLIT_FREEZE is set: so it's just a waste of time for remap_page()
to search for migration entries to remove when !PageAnon.

Fixes: baa355fd3314 ("thp: file pages support for split_huge_page()")
Signed-off-by: Hugh Dickins <hughd@google.com>
---
 mm/huge_memory.c | 5 +++++
 1 file changed, 5 insertions(+)

Comments

Yang Shi June 3, 2021, 10:09 p.m. UTC | #1 
On Tue, Jun 1, 2021 at 2:17 PM Hugh Dickins <hughd@google.com> wrote:
>
> THP splitting's unmap_page() only sets TTU_SPLIT_FREEZE when PageAnon,
> and migration entries are only inserted when TTU_MIGRATION (unused here)
> or TTU_SPLIT_FREEZE is set: so it's just a waste of time for remap_page()
> to search for migration entries to remove when !PageAnon.
>
> Fixes: baa355fd3314 ("thp: file pages support for split_huge_page()")
> Signed-off-by: Hugh Dickins <hughd@google.com>

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

> ---
>  mm/huge_memory.c | 5 +++++
>  1 file changed, 5 insertions(+)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 305f709a7aca..e4a83e310452 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -2354,6 +2354,7 @@ static void unmap_page(struct page *page)
>
>         VM_BUG_ON_PAGE(!PageHead(page), page);
>
> +       /* If TTU_SPLIT_FREEZE is ever extended to file, update remap_page() */
>         if (PageAnon(page))
>                 ttu_flags |= TTU_SPLIT_FREEZE;
>
> @@ -2368,6 +2369,10 @@ static void unmap_page(struct page *page)
>  static void remap_page(struct page *page, unsigned int nr)
>  {
>         int i;
> +
> +       /* If TTU_SPLIT_FREEZE is ever extended to file, remove this check */
> +       if (!PageAnon(page))
> +               return;
>         if (PageTransHuge(page)) {
>                 remove_migration_ptes(page, page, true);
>         } else {
> --
> 2.32.0.rc0.204.g9fa02ecfa5-goog
>
Kirill A . Shutemov June 4, 2021, 4:41 p.m. UTC | #2 
On Tue, Jun 01, 2021 at 02:17:19PM -0700, Hugh Dickins wrote:
> THP splitting's unmap_page() only sets TTU_SPLIT_FREEZE when PageAnon,
> and migration entries are only inserted when TTU_MIGRATION (unused here)
> or TTU_SPLIT_FREEZE is set: so it's just a waste of time for remap_page()
> to search for migration entries to remove when !PageAnon.
> 
> Fixes: baa355fd3314 ("thp: file pages support for split_huge_page()")
> Signed-off-by: Hugh Dickins <hughd@google.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 305f709a7aca..e4a83e310452 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2354,6 +2354,7 @@  static void unmap_page(struct page *page)
 
 	VM_BUG_ON_PAGE(!PageHead(page), page);
 
+	/* If TTU_SPLIT_FREEZE is ever extended to file, update remap_page() */
 	if (PageAnon(page))
 		ttu_flags |= TTU_SPLIT_FREEZE;
 
@@ -2368,6 +2369,10 @@  static void unmap_page(struct page *page)
 static void remap_page(struct page *page, unsigned int nr)
 {
 	int i;
+
+	/* If TTU_SPLIT_FREEZE is ever extended to file, remove this check */
+	if (!PageAnon(page))
+		return;
 	if (PageTransHuge(page)) {
 		remove_migration_ptes(page, page, true);
 	} else {