rmap.h

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#ifndef _LINUX_RMAP_H
#define _LINUX_RMAP_H
/*
 * Declarations for Reverse Mapping functions in mm/rmap.c
 */

#include <linux/list.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/mutex.h>
#include <linux/memcontrol.h>

/*
 * The anon_vma heads a list of private "related" vmas, to scan if
 * an anonymous page pointing to this anon_vma needs to be unmapped:
 * the vmas on the list will be related by forking, or by splitting.
 *
 * Since vmas come and go as they are split and merged (particularly
 * in mprotect), the mapping field of an anonymous page cannot point
 * directly to a vma: instead it points to an anon_vma, on whose list
 * the related vmas can be easily linked or unlinked.
 *
 * After unlinking the last vma on the list, we must garbage collect
 * the anon_vma object itself: we're guaranteed no page can be
 * pointing to this anon_vma once its vma list is empty.
 */
struct anon_vma {
    struct anon_vma *root;  /* Root of this anon_vma tree */
    struct mutex mutex; /* Serialize access to vma list */
    /*
     * The refcount is taken on an anon_vma when there is no
     * guarantee that the vma of page tables will exist for
     * the duration of the operation. A caller that takes
     * the reference is responsible for clearing up the
     * anon_vma if they are the last user on release
     */
    atomic_t refcount;

    /*
     * NOTE: the LSB of the rb_root.rb_node is set by
     * mm_take_all_locks() _after_ taking the above lock. So the
     * rb_root must only be read/written after taking the above lock
     * to be sure to see a valid next pointer. The LSB bit itself
     * is serialized by a system wide lock only visible to
     * mm_take_all_locks() (mm_all_locks_mutex).
     */
    struct rb_root rb_root; /* Interval tree of private "related" vmas */
};

/*
 * The copy-on-write semantics of fork mean that an anon_vma
 * can become associated with multiple processes. Furthermore,
 * each child process will have its own anon_vma, where new
 * pages for that process are instantiated.
 *
 * This structure allows us to find the anon_vmas associated
 * with a VMA, or the VMAs associated with an anon_vma.
 * The "same_vma" list contains the anon_vma_chains linking
 * all the anon_vmas associated with this VMA.
 * The "rb" field indexes on an interval tree the anon_vma_chains
 * which link all the VMAs associated with this anon_vma.
 */
struct anon_vma_chain {
    struct vm_area_struct *vma;
    struct anon_vma *anon_vma;
    struct list_head same_vma;   /* locked by mmap_sem & page_table_lock */
    struct rb_node rb;          /* locked by anon_vma->mutex */
    unsigned long rb_subtree_last;
#ifdef CONFIG_DEBUG_VM_RB
    unsigned long cached_vma_start, cached_vma_last;
#endif
};

enum ttu_flags {
    TTU_UNMAP = 0,          /* unmap mode */
    TTU_MIGRATION = 1,      /* migration mode */
    TTU_MUNLOCK = 2,        /* munlock mode */
    TTU_ACTION_MASK = 0xff,

    TTU_IGNORE_MLOCK = (1 << 8),    /* ignore mlock */
    TTU_IGNORE_ACCESS = (1 << 9),   /* don't age */
    TTU_IGNORE_HWPOISON = (1 << 10),/* corrupted page is recoverable */
};

#ifdef CONFIG_MMU
static inline void get_anon_vma(struct anon_vma *anon_vma)
{
    atomic_inc(&anon_vma->refcount);
}

void __put_anon_vma(struct anon_vma *anon_vma);

static inline void put_anon_vma(struct anon_vma *anon_vma)
{
    if (atomic_dec_and_test(&anon_vma->refcount))
        __put_anon_vma(anon_vma);
}

static inline struct anon_vma *page_anon_vma(struct page *page)
{
    if (((unsigned long)page->mapping & PAGE_MAPPING_FLAGS) !=
                        PAGE_MAPPING_ANON)
        return NULL;
    return page_rmapping(page);
}

static inline void vma_lock_anon_vma(struct vm_area_struct *vma)
{
    struct anon_vma *anon_vma = vma->anon_vma;
    if (anon_vma)
        mutex_lock(&anon_vma->root->mutex);
}

static inline void vma_unlock_anon_vma(struct vm_area_struct *vma)
{
    struct anon_vma *anon_vma = vma->anon_vma;
    if (anon_vma)
        mutex_unlock(&anon_vma->root->mutex);
}

static inline void anon_vma_lock(struct anon_vma *anon_vma)
{
    mutex_lock(&anon_vma->root->mutex);
}

static inline void anon_vma_unlock(struct anon_vma *anon_vma)
{
    mutex_unlock(&anon_vma->root->mutex);
}

/*
 * anon_vma helper functions.
 */
void anon_vma_init(void);   /* create anon_vma_cachep */
int  anon_vma_prepare(struct vm_area_struct *);
void unlink_anon_vmas(struct vm_area_struct *);
int anon_vma_clone(struct vm_area_struct *, struct vm_area_struct *);
int anon_vma_fork(struct vm_area_struct *, struct vm_area_struct *);

static inline void anon_vma_merge(struct vm_area_struct *vma,
                  struct vm_area_struct *next)
{
    VM_BUG_ON(vma->anon_vma != next->anon_vma);
    unlink_anon_vmas(next);
}

struct anon_vma *page_get_anon_vma(struct page *page);

/*
 * rmap interfaces called when adding or removing pte of page
 */
void page_move_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
void page_add_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
void do_page_add_anon_rmap(struct page *, struct vm_area_struct *,
               unsigned long, int);
void page_add_new_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
void page_add_file_rmap(struct page *);
void page_remove_rmap(struct page *);

void hugepage_add_anon_rmap(struct page *, struct vm_area_struct *,
                unsigned long);
void hugepage_add_new_anon_rmap(struct page *, struct vm_area_struct *,
                unsigned long);

static inline void page_dup_rmap(struct page *page)
{
    atomic_inc(&page->_mapcount);
}

/*
 * Called from mm/vmscan.c to handle paging out
 */
int page_referenced(struct page *, int is_locked,
            struct mem_cgroup *memcg, unsigned long *vm_flags);
int page_referenced_one(struct page *, struct vm_area_struct *,
    unsigned long address, unsigned int *mapcount, unsigned long *vm_flags);

#define TTU_ACTION(x) ((x) & TTU_ACTION_MASK)

int try_to_unmap(struct page *, enum ttu_flags flags);
int try_to_unmap_one(struct page *, struct vm_area_struct *,
            unsigned long address, enum ttu_flags flags);

/*
 * Called from mm/filemap_xip.c to unmap empty zero page
 */
pte_t *__page_check_address(struct page *, struct mm_struct *,
                unsigned long, spinlock_t **, int);

static inline pte_t *page_check_address(struct page *page, struct mm_struct *mm,
                    unsigned long address,
                    spinlock_t **ptlp, int sync)
{
    pte_t *ptep;

    __cond_lock(*ptlp, ptep = __page_check_address(page, mm, address,
                               ptlp, sync));
    return ptep;
}

/*
 * Used by swapoff to help locate where page is expected in vma.
 */
unsigned long page_address_in_vma(struct page *, struct vm_area_struct *);

/*
 * Cleans the PTEs of shared mappings.
 * (and since clean PTEs should also be readonly, write protects them too)
 *
 * returns the number of cleaned PTEs.
 */
int page_mkclean(struct page *);

/*
 * called in munlock()/munmap() path to check for other vmas holding
 * the page mlocked.
 */
int try_to_munlock(struct page *);

/*
 * Called by memory-failure.c to kill processes.
 */
struct anon_vma *page_lock_anon_vma(struct page *page);
void page_unlock_anon_vma(struct anon_vma *anon_vma);
int page_mapped_in_vma(struct page *page, struct vm_area_struct *vma);

/*
 * Called by migrate.c to remove migration ptes, but might be used more later.
 */
int rmap_walk(struct page *page, int (*rmap_one)(struct page *,
        struct vm_area_struct *, unsigned long, void *), void *arg);

#else   /* !CONFIG_MMU */

#define anon_vma_init()     do {} while (0)
#define anon_vma_prepare(vma)   (0)
#define anon_vma_link(vma)  do {} while (0)

static inline int page_referenced(struct page *page, int is_locked,
                  struct mem_cgroup *memcg,
                  unsigned long *vm_flags)
{
    *vm_flags = 0;
    return 0;
}

#define try_to_unmap(page, refs) SWAP_FAIL

static inline int page_mkclean(struct page *page)
{
    return 0;
}


#endif  /* CONFIG_MMU */

/*
 * Return values of try_to_unmap
 */
#define SWAP_SUCCESS    0
#define SWAP_AGAIN  1
#define SWAP_FAIL   2
#define SWAP_MLOCK  3

#endif  /* _LINUX_RMAP_H */