[PATCH v6 13/51] mm: Support arbitrary THP sizes

[Matthew Wilcox <willy@infradead.org>]

From: "Matthew Wilcox (Oracle)" <willy@infradead.org>

Use the compound size of the page instead of assuming PTE or PMD size.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 include/linux/huge_mm.h |  8 ++------
 include/linux/mm.h      | 42 ++++++++++++++++++++---------------------
 2 files changed, 23 insertions(+), 27 deletions(-)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index bd13e9ac3437..d125912a3e0d 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -282,9 +282,7 @@ static inline struct page *thp_head(struct page *page)
 static inline unsigned int thp_order(struct page *page)
 {
 	VM_BUG_ON_PGFLAGS(PageTail(page), page);
-	if (PageHead(page))
-		return HPAGE_PMD_ORDER;
-	return 0;
+	return compound_order(page);
 }
 
 /**
@@ -294,9 +292,7 @@ static inline unsigned int thp_order(struct page *page)
 static inline int thp_nr_pages(struct page *page)
 {
 	VM_BUG_ON_PGFLAGS(PageTail(page), page);
-	if (PageHead(page))
-		return HPAGE_PMD_NR;
-	return 1;
+	return compound_nr(page);
 }
 
 struct page *follow_devmap_pmd(struct vm_area_struct *vma, unsigned long addr,
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 3fc7e8121216..67b36b141ec7 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -668,6 +668,27 @@ int vma_is_stack_for_current(struct vm_area_struct *vma);
 struct mmu_gather;
 struct inode;
 
+static inline unsigned int compound_order(struct page *page)
+{
+	if (!PageHead(page))
+		return 0;
+	return page[1].compound_order;
+}
+
+/* Returns the number of pages in this potentially compound page. */
+static inline unsigned long compound_nr(struct page *page)
+{
+	if (!PageHead(page))
+		return 1;
+	return page[1].compound_nr;
+}
+
+static inline void set_compound_order(struct page *page, unsigned int order)
+{
+	page[1].compound_order = order;
+	page[1].compound_nr = 1U << order;
+}
+
 #include <linux/huge_mm.h>
 
 /*
@@ -879,13 +900,6 @@ static inline void destroy_compound_page(struct page *page)
 	compound_page_dtors[page[1].compound_dtor](page);
 }
 
-static inline unsigned int compound_order(struct page *page)
-{
-	if (!PageHead(page))
-		return 0;
-	return page[1].compound_order;
-}
-
 static inline bool hpage_pincount_available(struct page *page)
 {
 	/*
@@ -904,20 +918,6 @@ static inline int compound_pincount(struct page *page)
 	return atomic_read(compound_pincount_ptr(page));
 }
 
-static inline void set_compound_order(struct page *page, unsigned int order)
-{
-	page[1].compound_order = order;
-	page[1].compound_nr = 1U << order;
-}
-
-/* Returns the number of pages in this potentially compound page. */
-static inline unsigned long compound_nr(struct page *page)
-{
-	if (!PageHead(page))
-		return 1;
-	return page[1].compound_nr;
-}
-
 /* Returns the number of bytes in this potentially compound page. */
 static inline unsigned long page_size(struct page *page)
 {
-- 
2.26.2