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-rw-r--r--include/linux/mm.h33
-rw-r--r--include/linux/page-flags.h14
2 files changed, 42 insertions, 5 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h
index c95d96ebd5ad..8c149fa4491d 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -267,17 +267,28 @@ static inline int get_page_unless_zero(struct page *page)
return atomic_inc_not_zero(&page->_count);
}
+static inline struct page *compound_head(struct page *page)
+{
+ /*
+ * We could avoid the PageCompound(page) check if
+ * we would not overload PageTail().
+ *
+ * This check has to be done in several performance critical
+ * paths of the slab etc. IMHO PageTail deserves its own flag.
+ */
+ if (unlikely(PageCompound(page) && PageTail(page)))
+ return page->first_page;
+ return page;
+}
+
static inline int page_count(struct page *page)
{
- if (unlikely(PageCompound(page)))
- page = (struct page *)page_private(page);
- return atomic_read(&page->_count);
+ return atomic_read(&compound_head(page)->_count);
}
static inline void get_page(struct page *page)
{
- if (unlikely(PageCompound(page)))
- page = (struct page *)page_private(page);
+ page = compound_head(page);
VM_BUG_ON(atomic_read(&page->_count) == 0);
atomic_inc(&page->_count);
}
@@ -314,6 +325,18 @@ static inline compound_page_dtor *get_compound_page_dtor(struct page *page)
return (compound_page_dtor *)page[1].lru.next;
}
+static inline int compound_order(struct page *page)
+{
+ if (!PageCompound(page) || PageTail(page))
+ return 0;
+ return (unsigned long)page[1].lru.prev;
+}
+
+static inline void set_compound_order(struct page *page, unsigned long order)
+{
+ page[1].lru.prev = (void *)order;
+}
+
/*
* Multiple processes may "see" the same page. E.g. for untouched
* mappings of /dev/null, all processes see the same page full of
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 96326594e55d..a1e143634946 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -94,6 +94,12 @@
/* PG_owner_priv_1 users should have descriptive aliases */
#define PG_checked PG_owner_priv_1 /* Used by some filesystems */
+/*
+ * Marks tail portion of a compound page. We currently do not reclaim
+ * compound pages so we can reuse a flag only used for reclaim here.
+ */
+#define PG_tail PG_reclaim
+
#if (BITS_PER_LONG > 32)
/*
* 64-bit-only flags build down from bit 31
@@ -241,6 +247,14 @@ static inline void SetPageUptodate(struct page *page)
#define __SetPageCompound(page) __set_bit(PG_compound, &(page)->flags)
#define __ClearPageCompound(page) __clear_bit(PG_compound, &(page)->flags)
+/*
+ * Note: PG_tail is an alias of another page flag. The result of PageTail()
+ * is only valid if PageCompound(page) is true.
+ */
+#define PageTail(page) test_bit(PG_tail, &(page)->flags)
+#define __SetPageTail(page) __set_bit(PG_tail, &(page)->flags)
+#define __ClearPageTail(page) __clear_bit(PG_tail, &(page)->flags)
+
#ifdef CONFIG_SWAP
#define PageSwapCache(page) test_bit(PG_swapcache, &(page)->flags)
#define SetPageSwapCache(page) set_bit(PG_swapcache, &(page)->flags)