mm: avoid taking rmap locks in move_ptes()

[deliverable/linux.git] / include / linux / mmu_notifier.h

#ifndef _LINUX_MMU_NOTIFIER_H
#define _LINUX_MMU_NOTIFIER_H

#include <linux/list.h>
#include <linux/spinlock.h>
#include <linux/mm_types.h>
#include <linux/srcu.h>

struct mmu_notifier;
struct mmu_notifier_ops;

#ifdef CONFIG_MMU_NOTIFIER

/*
 * The mmu notifier_mm structure is allocated and installed in
 * mm->mmu_notifier_mm inside the mm_take_all_locks() protected
 * critical section and it's released only when mm_count reaches zero
 * in mmdrop().
 */
struct mmu_notifier_mm {
        /* all mmu notifiers registerd in this mm are queued in this list */
        struct hlist_head list;
        /* to serialize the list modifications and hlist_unhashed */
        spinlock_t lock;
};

struct mmu_notifier_ops {
        /*
         * Called either by mmu_notifier_unregister or when the mm is
         * being destroyed by exit_mmap, always before all pages are
         * freed. This can run concurrently with other mmu notifier
         * methods (the ones invoked outside the mm context) and it
         * should tear down all secondary mmu mappings and freeze the
         * secondary mmu. If this method isn't implemented you've to
         * be sure that nothing could possibly write to the pages
         * through the secondary mmu by the time the last thread with
         * tsk->mm == mm exits.
         *
         * As side note: the pages freed after ->release returns could
         * be immediately reallocated by the gart at an alias physical
         * address with a different cache model, so if ->release isn't
         * implemented because all _software_ driven memory accesses
         * through the secondary mmu are terminated by the time the
         * last thread of this mm quits, you've also to be sure that
         * speculative _hardware_ operations can't allocate dirty
         * cachelines in the cpu that could not be snooped and made
         * coherent with the other read and write operations happening
         * through the gart alias address, so leading to memory
         * corruption.
         */
        void (*release)(struct mmu_notifier *mn,
                        struct mm_struct *mm);

        /*
         * clear_flush_young is called after the VM is
         * test-and-clearing the young/accessed bitflag in the
         * pte. This way the VM will provide proper aging to the
         * accesses to the page through the secondary MMUs and not
         * only to the ones through the Linux pte.
         */
        int (*clear_flush_young)(struct mmu_notifier *mn,
                                 struct mm_struct *mm,
                                 unsigned long address);

        /*
         * test_young is called to check the young/accessed bitflag in
         * the secondary pte. This is used to know if the page is
         * frequently used without actually clearing the flag or tearing
         * down the secondary mapping on the page.
         */
        int (*test_young)(struct mmu_notifier *mn,
                          struct mm_struct *mm,
                          unsigned long address);

        /*
         * change_pte is called in cases that pte mapping to page is changed:
         * for example, when ksm remaps pte to point to a new shared page.
         */
        void (*change_pte)(struct mmu_notifier *mn,
                           struct mm_struct *mm,
                           unsigned long address,
                           pte_t pte);

        /*
         * Before this is invoked any secondary MMU is still ok to
         * read/write to the page previously pointed to by the Linux
         * pte because the page hasn't been freed yet and it won't be
         * freed until this returns. If required set_page_dirty has to
         * be called internally to this method.
         */
        void (*invalidate_page)(struct mmu_notifier *mn,
                                struct mm_struct *mm,
                                unsigned long address);

        /*
         * invalidate_range_start() and invalidate_range_end() must be
         * paired and are called only when the mmap_sem and/or the
         * locks protecting the reverse maps are held. The subsystem
         * must guarantee that no additional references are taken to
         * the pages in the range established between the call to
         * invalidate_range_start() and the matching call to
         * invalidate_range_end().
         *
         * Invalidation of multiple concurrent ranges may be
         * optionally permitted by the driver. Either way the
         * establishment of sptes is forbidden in the range passed to
         * invalidate_range_begin/end for the whole duration of the
         * invalidate_range_begin/end critical section.
         *
         * invalidate_range_start() is called when all pages in the
         * range are still mapped and have at least a refcount of one.
         *
         * invalidate_range_end() is called when all pages in the
         * range have been unmapped and the pages have been freed by
         * the VM.
         *
         * The VM will remove the page table entries and potentially
         * the page between invalidate_range_start() and
         * invalidate_range_end(). If the page must not be freed
         * because of pending I/O or other circumstances then the
         * invalidate_range_start() callback (or the initial mapping
         * by the driver) must make sure that the refcount is kept
         * elevated.
         *
         * If the driver increases the refcount when the pages are
         * initially mapped into an address space then either
         * invalidate_range_start() or invalidate_range_end() may
         * decrease the refcount. If the refcount is decreased on
         * invalidate_range_start() then the VM can free pages as page
         * table entries are removed.  If the refcount is only
         * droppped on invalidate_range_end() then the driver itself
         * will drop the last refcount but it must take care to flush
         * any secondary tlb before doing the final free on the
         * page. Pages will no longer be referenced by the linux
         * address space but may still be referenced by sptes until
         * the last refcount is dropped.
         */
        void (*invalidate_range_start)(struct mmu_notifier *mn,
                                       struct mm_struct *mm,
                                       unsigned long start, unsigned long end);
        void (*invalidate_range_end)(struct mmu_notifier *mn,
                                     struct mm_struct *mm,
                                     unsigned long start, unsigned long end);
};

/*
 * The notifier chains are protected by mmap_sem and/or the reverse map
 * semaphores. Notifier chains are only changed when all reverse maps and
 * the mmap_sem locks are taken.
 *
 * Therefore notifier chains can only be traversed when either
 *
 * 1. mmap_sem is held.
 * 2. One of the reverse map locks is held (i_mmap_mutex or anon_vma->mutex).
 * 3. No other concurrent thread can access the list (release)
 */
struct mmu_notifier {
        struct hlist_node hlist;
        const struct mmu_notifier_ops *ops;
};

static inline int mm_has_notifiers(struct mm_struct *mm)
{
        return unlikely(mm->mmu_notifier_mm);
}

extern int mmu_notifier_register(struct mmu_notifier *mn,
                                 struct mm_struct *mm);
extern int __mmu_notifier_register(struct mmu_notifier *mn,
                                   struct mm_struct *mm);
extern void mmu_notifier_unregister(struct mmu_notifier *mn,
                                    struct mm_struct *mm);
extern void __mmu_notifier_mm_destroy(struct mm_struct *mm);
extern void __mmu_notifier_release(struct mm_struct *mm);
extern int __mmu_notifier_clear_flush_young(struct mm_struct *mm,
                                          unsigned long address);
extern int __mmu_notifier_test_young(struct mm_struct *mm,
                                     unsigned long address);
extern void __mmu_notifier_change_pte(struct mm_struct *mm,
                                      unsigned long address, pte_t pte);
extern void __mmu_notifier_invalidate_page(struct mm_struct *mm,
                                          unsigned long address);
extern void __mmu_notifier_invalidate_range_start(struct mm_struct *mm,
                                  unsigned long start, unsigned long end);
extern void __mmu_notifier_invalidate_range_end(struct mm_struct *mm,
                                  unsigned long start, unsigned long end);

static inline void mmu_notifier_release(struct mm_struct *mm)
{
        if (mm_has_notifiers(mm))
                __mmu_notifier_release(mm);
}

static inline int mmu_notifier_clear_flush_young(struct mm_struct *mm,
                                          unsigned long address)
{
        if (mm_has_notifiers(mm))
                return __mmu_notifier_clear_flush_young(mm, address);
        return 0;
}

static inline int mmu_notifier_test_young(struct mm_struct *mm,
                                          unsigned long address)
{
        if (mm_has_notifiers(mm))
                return __mmu_notifier_test_young(mm, address);
        return 0;
}

static inline void mmu_notifier_change_pte(struct mm_struct *mm,
                                           unsigned long address, pte_t pte)
{
        if (mm_has_notifiers(mm))
                __mmu_notifier_change_pte(mm, address, pte);
}

static inline void mmu_notifier_invalidate_page(struct mm_struct *mm,
                                          unsigned long address)
{
        if (mm_has_notifiers(mm))
                __mmu_notifier_invalidate_page(mm, address);
}

static inline void mmu_notifier_invalidate_range_start(struct mm_struct *mm,
                                  unsigned long start, unsigned long end)
{
        if (mm_has_notifiers(mm))
                __mmu_notifier_invalidate_range_start(mm, start, end);
}

static inline void mmu_notifier_invalidate_range_end(struct mm_struct *mm,
                                  unsigned long start, unsigned long end)
{
        if (mm_has_notifiers(mm))
                __mmu_notifier_invalidate_range_end(mm, start, end);
}

static inline void mmu_notifier_mm_init(struct mm_struct *mm)
{
        mm->mmu_notifier_mm = NULL;
}

static inline void mmu_notifier_mm_destroy(struct mm_struct *mm)
{
        if (mm_has_notifiers(mm))
                __mmu_notifier_mm_destroy(mm);
}

/*
 * These two macros will sometime replace ptep_clear_flush.
 * ptep_clear_flush is implemented as macro itself, so this also is
 * implemented as a macro until ptep_clear_flush will converted to an
 * inline function, to diminish the risk of compilation failure. The
 * invalidate_page method over time can be moved outside the PT lock
 * and these two macros can be later removed.
 */
#define ptep_clear_flush_notify(__vma, __address, __ptep)               \
({                                                                      \
        pte_t __pte;                                                    \
        struct vm_area_struct *___vma = __vma;                          \
        unsigned long ___address = __address;                           \
        __pte = ptep_clear_flush(___vma, ___address, __ptep);           \
        mmu_notifier_invalidate_page(___vma->vm_mm, ___address);        \
        __pte;                                                          \
})

#define pmdp_clear_flush_notify(__vma, __address, __pmdp)               \
({                                                                      \
        pmd_t __pmd;                                                    \
        struct vm_area_struct *___vma = __vma;                          \
        unsigned long ___address = __address;                           \
        VM_BUG_ON(__address & ~HPAGE_PMD_MASK);                         \
        mmu_notifier_invalidate_range_start(___vma->vm_mm, ___address,  \
                                            (__address)+HPAGE_PMD_SIZE);\
        __pmd = pmdp_clear_flush(___vma, ___address, __pmdp);           \
        mmu_notifier_invalidate_range_end(___vma->vm_mm, ___address,    \
                                          (__address)+HPAGE_PMD_SIZE);  \
        __pmd;                                                          \
})

#define pmdp_splitting_flush_notify(__vma, __address, __pmdp)           \
({                                                                      \
        struct vm_area_struct *___vma = __vma;                          \
        unsigned long ___address = __address;                           \
        VM_BUG_ON(__address & ~HPAGE_PMD_MASK);                         \
        mmu_notifier_invalidate_range_start(___vma->vm_mm, ___address,  \
                                            (__address)+HPAGE_PMD_SIZE);\
        pmdp_splitting_flush(___vma, ___address, __pmdp);               \
        mmu_notifier_invalidate_range_end(___vma->vm_mm, ___address,    \
                                          (__address)+HPAGE_PMD_SIZE);  \
})

#define ptep_clear_flush_young_notify(__vma, __address, __ptep)         \
({                                                                      \
        int __young;                                                    \
        struct vm_area_struct *___vma = __vma;                          \
        unsigned long ___address = __address;                           \
        __young = ptep_clear_flush_young(___vma, ___address, __ptep);   \
        __young |= mmu_notifier_clear_flush_young(___vma->vm_mm,        \
                                                  ___address);          \
        __young;                                                        \
})

#define pmdp_clear_flush_young_notify(__vma, __address, __pmdp)         \
({                                                                      \
        int __young;                                                    \
        struct vm_area_struct *___vma = __vma;                          \
        unsigned long ___address = __address;                           \
        __young = pmdp_clear_flush_young(___vma, ___address, __pmdp);   \
        __young |= mmu_notifier_clear_flush_young(___vma->vm_mm,        \
                                                  ___address);          \
        __young;                                                        \
})

/*
 * set_pte_at_notify() sets the pte _after_ running the notifier.
 * This is safe to start by updating the secondary MMUs, because the primary MMU
 * pte invalidate must have already happened with a ptep_clear_flush() before
 * set_pte_at_notify() has been invoked.  Updating the secondary MMUs first is
 * required when we change both the protection of the mapping from read-only to
 * read-write and the pfn (like during copy on write page faults). Otherwise the
 * old page would remain mapped readonly in the secondary MMUs after the new
 * page is already writable by some CPU through the primary MMU.
 */
#define set_pte_at_notify(__mm, __address, __ptep, __pte)               \
({                                                                      \
        struct mm_struct *___mm = __mm;                                 \
        unsigned long ___address = __address;                           \
        pte_t ___pte = __pte;                                           \
                                                                        \
        mmu_notifier_change_pte(___mm, ___address, ___pte);             \
        set_pte_at(___mm, ___address, __ptep, ___pte);                  \
})

#else /* CONFIG_MMU_NOTIFIER */

static inline void mmu_notifier_release(struct mm_struct *mm)
{
}

static inline int mmu_notifier_clear_flush_young(struct mm_struct *mm,
                                          unsigned long address)
{
        return 0;
}

static inline int mmu_notifier_test_young(struct mm_struct *mm,
                                          unsigned long address)
{
        return 0;
}

static inline void mmu_notifier_change_pte(struct mm_struct *mm,
                                           unsigned long address, pte_t pte)
{
}

static inline void mmu_notifier_invalidate_page(struct mm_struct *mm,
                                          unsigned long address)
{
}

static inline void mmu_notifier_invalidate_range_start(struct mm_struct *mm,
                                  unsigned long start, unsigned long end)
{
}

static inline void mmu_notifier_invalidate_range_end(struct mm_struct *mm,
                                  unsigned long start, unsigned long end)
{
}

static inline void mmu_notifier_mm_init(struct mm_struct *mm)
{
}

static inline void mmu_notifier_mm_destroy(struct mm_struct *mm)
{
}

#define ptep_clear_flush_young_notify ptep_clear_flush_young
#define pmdp_clear_flush_young_notify pmdp_clear_flush_young
#define ptep_clear_flush_notify ptep_clear_flush
#define pmdp_clear_flush_notify pmdp_clear_flush
#define pmdp_splitting_flush_notify pmdp_splitting_flush
#define set_pte_at_notify set_pte_at

#endif /* CONFIG_MMU_NOTIFIER */

#endif /* _LINUX_MMU_NOTIFIER_H */