percpu: migrate percpu data structures to internal header

Migrates pcpu_chunk definition and a few percpu static variables to an
internal header file from mm/percpu.c. These will be used with debugfs
to expose statistics about percpu memory improving visibility regarding
allocations and fragmentation.

Signed-off-by: Dennis Zhou <dennisz@fb.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

mm/percpu-internal.h

@@ -0,0 +1,33 @@
+#ifndef _MM_PERCPU_INTERNAL_H
+#define _MM_PERCPU_INTERNAL_H
+
+#include <linux/types.h>
+#include <linux/percpu.h>
+
+struct pcpu_chunk {
+	struct list_head	list;		/* linked to pcpu_slot lists */
+	int			free_size;	/* free bytes in the chunk */
+	int			contig_hint;	/* max contiguous size hint */
+	void			*base_addr;	/* base address of this chunk */
+
+	int			map_used;	/* # of map entries used before the sentry */
+	int			map_alloc;	/* # of map entries allocated */
+	int			*map;		/* allocation map */
+	struct list_head	map_extend_list;/* on pcpu_map_extend_chunks */
+
+	void			*data;		/* chunk data */
+	int			first_free;	/* no free below this */
+	bool			immutable;	/* no [de]population allowed */
+	int			nr_populated;	/* # of populated pages */
+	unsigned long		populated[];	/* populated bitmap */
+};
+
+extern spinlock_t pcpu_lock;
+
+extern struct list_head *pcpu_slot;
+extern int pcpu_nr_slots;
+
+extern struct pcpu_chunk *pcpu_first_chunk;
+extern struct pcpu_chunk *pcpu_reserved_chunk;
+
+#endif