[v3,02/14] mm/page_alloc: split prep_compound_page into head and tail subparts

Commit Message

Joao Martins July 14, 2021, 7:35 p.m. UTC

Split the utility function prep_compound_page() into head and tail
counterparts, and use them accordingly.

This is in preparation for sharing the storage for / deduplicating
compound page metadata.

Signed-off-by: Joao Martins <[e-mail]>
Acked-by: Mike Kravetz <[e-mail]>
---
 mm/page_alloc.c | 30 ++++++++++++++++++++----------
 1 file changed, 20 insertions(+), 10 deletions(-)

Comments

Dan Williams July 15, 2021, 12:19 a.m. UTC | #1

On Wed, Jul 14, 2021 at 12:36 PM Joao Martins <[e-mail]> wrote:
>
> Split the utility function prep_compound_page() into head and tail
> counterparts, and use them accordingly.
>
> This is in preparation for sharing the storage for / deduplicating
> compound page metadata.
>
> Signed-off-by: Joao Martins <[e-mail]>
> Acked-by: Mike Kravetz <[e-mail]>

Looks good,

Reviewed-by: Dan Williams <[e-mail]>

Muchun Song July 15, 2021, 2:53 a.m. UTC | #2

On Thu, Jul 15, 2021 at 3:36 AM Joao Martins <[e-mail]> wrote:
>
> Split the utility function prep_compound_page() into head and tail
> counterparts, and use them accordingly.
>
> This is in preparation for sharing the storage for / deduplicating
> compound page metadata.
>
> Signed-off-by: Joao Martins <[e-mail]>
> Acked-by: Mike Kravetz <[e-mail]>

Reviewed-by: Muchun Song <[e-mail]>

Joao Martins July 15, 2021, 1:17 p.m. UTC | #3

On 7/15/21 3:53 AM, Muchun Song wrote:
> On Thu, Jul 15, 2021 at 3:36 AM Joao Martins <[e-mail]> wrote:
>>
>> Split the utility function prep_compound_page() into head and tail
>> counterparts, and use them accordingly.
>>
>> This is in preparation for sharing the storage for / deduplicating
>> compound page metadata.
>>
>> Signed-off-by: Joao Martins <[e-mail]>
>> Acked-by: Mike Kravetz <[e-mail]>
> 
> Reviewed-by: Muchun Song <[e-mail]>
> 
Thanks!

Patch

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 3b97e17806be..68b5591a69fe 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -730,23 +730,33 @@  void free_compound_page(struct page *page)
 	free_the_page(page, compound_order(page));
 }
 
+static void prep_compound_head(struct page *page, unsigned int order)
+{
+	set_compound_page_dtor(page, COMPOUND_PAGE_DTOR);
+	set_compound_order(page, order);
+	atomic_set(compound_mapcount_ptr(page), -1);
+	if (hpage_pincount_available(page))
+		atomic_set(compound_pincount_ptr(page), 0);
+}
+
+static void prep_compound_tail(struct page *head, int tail_idx)
+{
+	struct page *p = head + tail_idx;
+
+	p->mapping = TAIL_MAPPING;
+	set_compound_head(p, head);
+}
+
 void prep_compound_page(struct page *page, unsigned int order)
 {
 	int i;
 	int nr_pages = 1 << order;
 
 	__SetPageHead(page);
-	for (i = 1; i < nr_pages; i++) {
-		struct page *p = page + i;
-		p->mapping = TAIL_MAPPING;
-		set_compound_head(p, page);
-	}
+	for (i = 1; i < nr_pages; i++)
+		prep_compound_tail(page, i);
 
-	set_compound_page_dtor(page, COMPOUND_PAGE_DTOR);
-	set_compound_order(page, order);
-	atomic_set(compound_mapcount_ptr(page), -1);
-	if (hpage_pincount_available(page))
-		atomic_set(compound_pincount_ptr(page), 0);
+	prep_compound_head(page, order);
 }
 
 #ifdef CONFIG_DEBUG_PAGEALLOC