Re: [PATCH v2 02/14] mm/page_alloc: split prep_compound_page into head and tail subparts
From: Mike Kravetz <hidden>
Date: 2021-07-13 00:02:31
Also in:
linux-mm, nvdimm
On 6/17/21 11:44 AM, Joao Martins wrote:
quoted hunk ↗ jump to hunk
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 <redacted> --- mm/page_alloc.c | 32 +++++++++++++++++++++----------- 1 file changed, 21 insertions(+), 11 deletions(-)diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 8836e54721ae..95967ce55829 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c@@ -741,24 +741,34 @@ 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; + + set_page_count(p, 0);
When you rebase, you should notice this has been removed from prep_compound_page as all tail pages should have zero ref count.
+ 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;
- set_page_count(p, 0);
- 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_PAGEALLOCI'll need something like this for demote hugetlb page fuinctionality when the pages being demoted have been optimized for minimal vmemmap usage. Acked-by: Mike Kravetz <redacted> -- Mike Kravetz