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-rw-r--r--mm/page_alloc.c22
1 files changed, 22 insertions, 0 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 10291985135..fc65e87368b 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -752,6 +752,28 @@ static inline void prep_zero_page(struct page *page, int order, gfp_t gfp_flags)
clear_highpage(page + i);
}
+#ifdef CONFIG_MMU
+/*
+ * split_page takes a non-compound higher-order page, and splits it into
+ * n (1<<order) sub-pages: page[0..n]
+ * Each sub-page must be freed individually.
+ *
+ * Note: this is probably too low level an operation for use in drivers.
+ * Please consult with lkml before using this in your driver.
+ */
+void split_page(struct page *page, unsigned int order)
+{
+ int i;
+
+ BUG_ON(PageCompound(page));
+ BUG_ON(!page_count(page));
+ for (i = 1; i < (1 << order); i++) {
+ BUG_ON(page_count(page + i));
+ set_page_count(page + i, 1);
+ }
+}
+#endif
+
/*
* Really, prep_compound_page() should be called from __rmqueue_bulk(). But
* we cheat by calling it from here, in the order > 0 path. Saves a branch