3 files changed, 144 insertions, 0 deletions
diff --git a/include/linux/frontswap.h b/include/linux/frontswap.h
new file mode 100644
index 0000000..0e4e2ee
--- /dev/null
+++ b/include/linux/frontswap.h
@@ -0,0 +1,127 @@
+#ifndef _LINUX_FRONTSWAP_H
+#define _LINUX_FRONTSWAP_H
+
+#include <linux/swap.h>
+#include <linux/mm.h>
+#include <linux/bitops.h>
+
+struct frontswap_ops {
+	void (*init)(unsigned);
+	int (*store)(unsigned, pgoff_t, struct page *);
+	int (*load)(unsigned, pgoff_t, struct page *);
+	void (*invalidate_page)(unsigned, pgoff_t);
+	void (*invalidate_area)(unsigned);
+};
+
+extern bool frontswap_enabled;
+extern struct frontswap_ops
+	frontswap_register_ops(struct frontswap_ops *ops);
+extern void frontswap_shrink(unsigned long);
+extern unsigned long frontswap_curr_pages(void);
+extern void frontswap_writethrough(bool);
+
+extern void __frontswap_init(unsigned type);
+extern int __frontswap_store(struct page *page);
+extern int __frontswap_load(struct page *page);
+extern void __frontswap_invalidate_page(unsigned, pgoff_t);
+extern void __frontswap_invalidate_area(unsigned);
+
+#ifdef CONFIG_FRONTSWAP
+
+static inline bool frontswap_test(struct swap_info_struct *sis, pgoff_t offset)
+{
+	bool ret = false;
+
+	if (frontswap_enabled && sis->frontswap_map)
+		ret = test_bit(offset, sis->frontswap_map);
+	return ret;
+}
+
+static inline void frontswap_set(struct swap_info_struct *sis, pgoff_t offset)
+{
+	if (frontswap_enabled && sis->frontswap_map)
+		set_bit(offset, sis->frontswap_map);
+}
+
+static inline void frontswap_clear(struct swap_info_struct *sis, pgoff_t offset)
+{
+	if (frontswap_enabled && sis->frontswap_map)
+		clear_bit(offset, sis->frontswap_map);
+}
+
+static inline void frontswap_map_set(struct swap_info_struct *p,
+				     unsigned long *map)
+{
+	p->frontswap_map = map;
+}
+
+static inline unsigned long *frontswap_map_get(struct swap_info_struct *p)
+{
+	return p->frontswap_map;
+}
+#else
+/* all inline routines become no-ops and all externs are ignored */
+
+#define frontswap_enabled (0)
+
+static inline bool frontswap_test(struct swap_info_struct *sis, pgoff_t offset)
+{
+	return false;
+}
+
+static inline void frontswap_set(struct swap_info_struct *sis, pgoff_t offset)
+{
+}
+
+static inline void frontswap_clear(struct swap_info_struct *sis, pgoff_t offset)
+{
+}
+
+static inline void frontswap_map_set(struct swap_info_struct *p,
+				     unsigned long *map)
+{
+}
+
+static inline unsigned long *frontswap_map_get(struct swap_info_struct *p)
+{
+	return NULL;
+}
+#endif
+
+static inline int frontswap_store(struct page *page)
+{
+	int ret = -1;
+
+	if (frontswap_enabled)
+		ret = __frontswap_store(page);
+	return ret;
+}
+
+static inline int frontswap_load(struct page *page)
+{
+	int ret = -1;
+
+	if (frontswap_enabled)
+		ret = __frontswap_load(page);
+	return ret;
+}
+
+static inline void frontswap_invalidate_page(unsigned type, pgoff_t offset)
+{
+	if (frontswap_enabled)
+		__frontswap_invalidate_page(type, offset);
+}
+
+static inline void frontswap_invalidate_area(unsigned type)
+{
+	if (frontswap_enabled)
+		__frontswap_invalidate_area(type);
+}
+
+static inline void frontswap_init(unsigned type)
+{
+	if (frontswap_enabled)
+		__frontswap_init(type);
+}
+
+#endif /* _LINUX_FRONTSWAP_H */
diff --git a/include/linux/swap.h b/include/linux/swap.h
index b666193..c84ec68 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -197,6 +197,10 @@ struct swap_info_struct {
 	struct block_device *bdev;	/* swap device or bdev of swap file */
 	struct file *swap_file;		/* seldom referenced */
 	unsigned int old_block_size;	/* seldom referenced */
+#ifdef CONFIG_FRONTSWAP
+	unsigned long *frontswap_map;	/* frontswap in-use, one bit per page */
+	atomic_t frontswap_pages;	/* frontswap pages in-use counter */
+#endif
 };
 
 struct swap_list_t {
diff --git a/include/linux/swapfile.h b/include/linux/swapfile.h
new file mode 100644
index 0000000..e282624
--- /dev/null
+++ b/include/linux/swapfile.h
@@ -0,0 +1,13 @@
+#ifndef _LINUX_SWAPFILE_H
+#define _LINUX_SWAPFILE_H
+
+/*
+ * these were static in swapfile.c but frontswap.c needs them and we don't
+ * want to expose them to the dozens of source files that include swap.h
+ */
+extern spinlock_t swap_lock;
+extern struct swap_list_t swap_list;
+extern struct swap_info_struct *swap_info[];
+extern int try_to_unuse(unsigned int, bool, unsigned long);
+
+#endif /* _LINUX_SWAPFILE_H */