linux-libre/include/linux/swapfile.h

#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 plist_head swap_active_head;
extern struct swap_info_struct *swap_info[];
extern int try_to_unuse(unsigned int, bool, unsigned long);

#endif /* _LINUX_SWAPFILE_H */