mm: add fields for compound destructor and order into struct page
Currently, we use lru.next/lru.prev plus cast to access or set
destructor and order of compound page.
Let's replace it with explicit fields in struct page.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Jerome Marchand <jmarchan@redhat.com>
Acked-by: Christoph Lameter <cl@linux.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 65db4ae..8dd4fde 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -627,29 +627,28 @@
* prototype for that function and accessor functions.
* These are _only_ valid on the head of a PG_compound page.
*/
-typedef void compound_page_dtor(struct page *);
static inline void set_compound_page_dtor(struct page *page,
compound_page_dtor *dtor)
{
- page[1].lru.next = (void *)dtor;
+ page[1].compound_dtor = dtor;
}
static inline compound_page_dtor *get_compound_page_dtor(struct page *page)
{
- return (compound_page_dtor *)page[1].lru.next;
+ return page[1].compound_dtor;
}
static inline int compound_order(struct page *page)
{
if (!PageHead(page))
return 0;
- return (unsigned long)page[1].lru.prev;
+ return page[1].compound_order;
}
static inline void set_compound_order(struct page *page, unsigned long order)
{
- page[1].lru.prev = (void *)order;
+ page[1].compound_order = order;
}
#ifdef CONFIG_MMU
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 07c8bd3..20ff210 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -28,6 +28,8 @@
IS_ENABLED(CONFIG_ARCH_ENABLE_SPLIT_PMD_PTLOCK))
#define ALLOC_SPLIT_PTLOCKS (SPINLOCK_SIZE > BITS_PER_LONG/8)
+typedef void compound_page_dtor(struct page *);
+
/*
* Each physical page in the system has a struct page associated with
* it to keep track of whatever it is we are using the page for at the
@@ -142,6 +144,12 @@
struct rcu_head rcu_head; /* Used by SLAB
* when destroying via RCU
*/
+ /* First tail page of compound page */
+ struct {
+ compound_page_dtor *compound_dtor;
+ unsigned long compound_order;
+ };
+
#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && USE_SPLIT_PMD_PTLOCKS
pgtable_t pmd_huge_pte; /* protected by page->ptl */
#endif