include/asm-generic/pgtable.h - kernel/msm-4.9 - Gitiles

 #ifndef _ASM_GENERIC_PGTABLE_H
 #define _ASM_GENERIC_PGTABLE_H

 #ifndef __ASSEMBLY__
 #ifdef CONFIG_MMU

 #include <linux/mm_types.h>
 #include <linux/bug.h>
 #include <linux/errno.h>

 #if 4 - defined(__PAGETABLE_PUD_FOLDED) - defined(__PAGETABLE_PMD_FOLDED) != \
 	CONFIG_PGTABLE_LEVELS
 #error CONFIG_PGTABLE_LEVELS is not consistent with __PAGETABLE_{PUD,PMD}_FOLDED
 #endif

 /*
  * On almost all architectures and configurations, 0 can be used as the
  * upper ceiling to free_pgtables(): on many architectures it has the same
  * effect as using TASK_SIZE.  However, there is one configuration which
  * must impose a more careful limit, to avoid freeing kernel pgtables.
  */
 #ifndef USER_PGTABLES_CEILING
 #define USER_PGTABLES_CEILING	0UL
 #endif

 #ifndef __HAVE_ARCH_PTEP_SET_ACCESS_FLAGS
 extern int ptep_set_access_flags(struct vm_area_struct *vma,
 				 unsigned long address, pte_t *ptep,
 				 pte_t entry, int dirty);
 #endif

 #ifndef __HAVE_ARCH_PMDP_SET_ACCESS_FLAGS
 extern int pmdp_set_access_flags(struct vm_area_struct *vma,
 				 unsigned long address, pmd_t *pmdp,
 				 pmd_t entry, int dirty);
 #endif

 #ifndef __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG
 static inline int ptep_test_and_clear_young(struct vm_area_struct *vma,
 					    unsigned long address,
 					    pte_t *ptep)
 {
 	pte_t pte = *ptep;
 	int r = 1;
 	if (!pte_young(pte))
 		r = 0;
 	else
 		set_pte_at(vma->vm_mm, address, ptep, pte_mkold(pte));
 	return r;
 }
 #endif

 #ifndef __HAVE_ARCH_PMDP_TEST_AND_CLEAR_YOUNG
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma,
 					    unsigned long address,
 					    pmd_t *pmdp)
 {
 	pmd_t pmd = *pmdp;
 	int r = 1;
 	if (!pmd_young(pmd))
 		r = 0;
 	else
 		set_pmd_at(vma->vm_mm, address, pmdp, pmd_mkold(pmd));
 	return r;
 }
 #else /* CONFIG_TRANSPARENT_HUGEPAGE */
 static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma,
 					    unsigned long address,
 					    pmd_t *pmdp)
 {
 	BUG();
 	return 0;
 }
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 #endif

 #ifndef __HAVE_ARCH_PTEP_CLEAR_YOUNG_FLUSH
 int ptep_clear_flush_young(struct vm_area_struct *vma,
 			   unsigned long address, pte_t *ptep);
 #endif

 #ifndef __HAVE_ARCH_PMDP_CLEAR_YOUNG_FLUSH
 int pmdp_clear_flush_young(struct vm_area_struct *vma,
 			   unsigned long address, pmd_t *pmdp);
 #endif

 #ifndef __HAVE_ARCH_PTEP_GET_AND_CLEAR
 static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
 				       unsigned long address,
 				       pte_t *ptep)
 {
 	pte_t pte = *ptep;
 	pte_clear(mm, address, ptep);
 	return pte;
 }
 #endif

 #ifndef __HAVE_ARCH_PMDP_HUGE_GET_AND_CLEAR
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm,
 					    unsigned long address,
 					    pmd_t *pmdp)
 {
 	pmd_t pmd = *pmdp;
 	pmd_clear(pmdp);
 	return pmd;
 }
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 #endif

 #ifndef __HAVE_ARCH_PMDP_HUGE_GET_AND_CLEAR_FULL
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 static inline pmd_t pmdp_huge_get_and_clear_full(struct mm_struct *mm,
 					    unsigned long address, pmd_t *pmdp,
 					    int full)
 {
 	return pmdp_huge_get_and_clear(mm, address, pmdp);
 }
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 #endif

 #ifndef __HAVE_ARCH_PTEP_GET_AND_CLEAR_FULL
 static inline pte_t ptep_get_and_clear_full(struct mm_struct *mm,
 					    unsigned long address, pte_t *ptep,
 					    int full)
 {
 	pte_t pte;
 	pte = ptep_get_and_clear(mm, address, ptep);
 	return pte;
 }
 #endif

 /*
  * Some architectures may be able to avoid expensive synchronization
  * primitives when modifications are made to PTE's which are already
  * not present, or in the process of an address space destruction.
  */
 #ifndef __HAVE_ARCH_PTE_CLEAR_NOT_PRESENT_FULL
 static inline void pte_clear_not_present_full(struct mm_struct *mm,
 					      unsigned long address,
 					      pte_t *ptep,
 					      int full)
 {
 	pte_clear(mm, address, ptep);
 }
 #endif

 #ifndef __HAVE_ARCH_PTEP_CLEAR_FLUSH
 extern pte_t ptep_clear_flush(struct vm_area_struct *vma,
 			      unsigned long address,
 			      pte_t *ptep);
 #endif

 #ifndef __HAVE_ARCH_PMDP_HUGE_CLEAR_FLUSH
 extern pmd_t pmdp_huge_clear_flush(struct vm_area_struct *vma,
 			      unsigned long address,
 			      pmd_t *pmdp);
 #endif

 #ifndef __HAVE_ARCH_PTEP_SET_WRPROTECT
 struct mm_struct;
 static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long address, pte_t *ptep)
 {
 	pte_t old_pte = *ptep;
 	set_pte_at(mm, address, ptep, pte_wrprotect(old_pte));
 }
 #endif

 #ifndef __HAVE_ARCH_PMDP_SET_WRPROTECT
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 static inline void pmdp_set_wrprotect(struct mm_struct *mm,
 				      unsigned long address, pmd_t *pmdp)
 {
 	pmd_t old_pmd = *pmdp;
 	set_pmd_at(mm, address, pmdp, pmd_wrprotect(old_pmd));
 }
 #else /* CONFIG_TRANSPARENT_HUGEPAGE */
 static inline void pmdp_set_wrprotect(struct mm_struct *mm,
 				      unsigned long address, pmd_t *pmdp)
 {
 	BUG();
 }
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 #endif

 #ifndef __HAVE_ARCH_PMDP_SPLITTING_FLUSH
 extern void pmdp_splitting_flush(struct vm_area_struct *vma,
 				 unsigned long address, pmd_t *pmdp);
 #endif

 #ifndef pmdp_collapse_flush
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 extern pmd_t pmdp_collapse_flush(struct vm_area_struct *vma,
 				 unsigned long address, pmd_t *pmdp);
 #else
 static inline pmd_t pmdp_collapse_flush(struct vm_area_struct *vma,
 					unsigned long address,
 					pmd_t *pmdp)
 {
 	BUILD_BUG();
 	return *pmdp;
 }
 #define pmdp_collapse_flush pmdp_collapse_flush
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 #endif

 #ifndef __HAVE_ARCH_PGTABLE_DEPOSIT
 extern void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp,
 				       pgtable_t pgtable);
 #endif

 #ifndef __HAVE_ARCH_PGTABLE_WITHDRAW
 extern pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp);
 #endif

 #ifndef __HAVE_ARCH_PMDP_INVALIDATE
 extern void pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
 			    pmd_t *pmdp);
 #endif

 #ifndef __HAVE_ARCH_PTE_SAME
 static inline int pte_same(pte_t pte_a, pte_t pte_b)
 {
 	return pte_val(pte_a) == pte_val(pte_b);
 }
 #endif

 #ifndef __HAVE_ARCH_PTE_UNUSED
 /*
  * Some architectures provide facilities to virtualization guests
  * so that they can flag allocated pages as unused. This allows the
  * host to transparently reclaim unused pages. This function returns
  * whether the pte's page is unused.
  */
 static inline int pte_unused(pte_t pte)
 {
 	return 0;
 }
 #endif

 #ifndef __HAVE_ARCH_PMD_SAME
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 static inline int pmd_same(pmd_t pmd_a, pmd_t pmd_b)
 {
 	return pmd_val(pmd_a) == pmd_val(pmd_b);
 }
 #else /* CONFIG_TRANSPARENT_HUGEPAGE */
 static inline int pmd_same(pmd_t pmd_a, pmd_t pmd_b)
 {
 	BUG();
 	return 0;
 }
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
 #endif

 #ifndef __HAVE_ARCH_PGD_OFFSET_GATE
 #define pgd_offset_gate(mm, addr)	pgd_offset(mm, addr)
 #endif

 #ifndef __HAVE_ARCH_MOVE_PTE
 #define move_pte(pte, prot, old_addr, new_addr)	(pte)
 #endif

 #ifndef pte_accessible
 # define pte_accessible(mm, pte)	((void)(pte), 1)
 #endif

 #ifndef flush_tlb_fix_spurious_fault
 #define flush_tlb_fix_spurious_fault(vma, address) flush_tlb_page(vma, address)
 #endif

 #ifndef pgprot_noncached
 #define pgprot_noncached(prot)	(prot)
 #endif

 #ifndef pgprot_writecombine
 #define pgprot_writecombine pgprot_noncached
 #endif

 #ifndef pgprot_writethrough
 #define pgprot_writethrough pgprot_noncached
 #endif

 #ifndef pgprot_device
 #define pgprot_device pgprot_noncached
 #endif

 #ifndef pgprot_modify
 #define pgprot_modify pgprot_modify
 static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot)
 {
 	if (pgprot_val(oldprot) == pgprot_val(pgprot_noncached(oldprot)))
 		newprot = pgprot_noncached(newprot);
 	if (pgprot_val(oldprot) == pgprot_val(pgprot_writecombine(oldprot)))
 		newprot = pgprot_writecombine(newprot);
 	if (pgprot_val(oldprot) == pgprot_val(pgprot_device(oldprot)))
 		newprot = pgprot_device(newprot);
 	return newprot;
 }
 #endif

 /*
  * When walking page tables, get the address of the next boundary,
  * or the end address of the range if that comes earlier.  Although no
  * vma end wraps to 0, rounded up __boundary may wrap to 0 throughout.
  */

 #define pgd_addr_end(addr, end)						\
 ({	unsigned long __boundary = ((addr) + PGDIR_SIZE) & PGDIR_MASK;	\
 	(__boundary - 1 < (end) - 1)? __boundary: (end);		\
 })

 #ifndef pud_addr_end
 #define pud_addr_end(addr, end)						\
 ({	unsigned long __boundary = ((addr) + PUD_SIZE) & PUD_MASK;	\
 	(__boundary - 1 < (end) - 1)? __boundary: (end);		\
 })
 #endif

 #ifndef pmd_addr_end
 #define pmd_addr_end(addr, end)						\
 ({	unsigned long __boundary = ((addr) + PMD_SIZE) & PMD_MASK;	\
 	(__boundary - 1 < (end) - 1)? __boundary: (end);		\
 })
 #endif

 /*
  * When walking page tables, we usually want to skip any p?d_none entries;
  * and any p?d_bad entries - reporting the error before resetting to none.
  * Do the tests inline, but report and clear the bad entry in mm/memory.c.
  */
 void pgd_clear_bad(pgd_t *);
 void pud_clear_bad(pud_t *);
 void pmd_clear_bad(pmd_t *);

 static inline int pgd_none_or_clear_bad(pgd_t *pgd)
 {
 	if (pgd_none(*pgd))
 		return 1;
 	if (unlikely(pgd_bad(*pgd))) {
 		pgd_clear_bad(pgd);
 		return 1;
 	}
 	return 0;
 }

 static inline int pud_none_or_clear_bad(pud_t *pud)
 {
 	if (pud_none(*pud))
 		return 1;
 	if (unlikely(pud_bad(*pud))) {
 		pud_clear_bad(pud);
 		return 1;
 	}
 	return 0;
 }

 static inline int pmd_none_or_clear_bad(pmd_t *pmd)
 {
 	if (pmd_none(*pmd))
 		return 1;
 	if (unlikely(pmd_bad(*pmd))) {
 		pmd_clear_bad(pmd);
 		return 1;
 	}
 	return 0;
 }

 static inline pte_t __ptep_modify_prot_start(struct mm_struct *mm,
 					     unsigned long addr,
 					     pte_t *ptep)
 {
 	/*
 	 * Get the current pte state, but zero it out to make it
 	 * non-present, preventing the hardware from asynchronously
 	 * updating it.
 	 */
 	return ptep_get_and_clear(mm, addr, ptep);
 }

 static inline void __ptep_modify_prot_commit(struct mm_struct *mm,
 					     unsigned long addr,
 					     pte_t *ptep, pte_t pte)
 {
 	/*
 	 * The pte is non-present, so there's no hardware state to
 	 * preserve.
 	 */
 	set_pte_at(mm, addr, ptep, pte);
 }

 #ifndef __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION
 /*
  * Start a pte protection read-modify-write transaction, which
  * protects against asynchronous hardware modifications to the pte.
  * The intention is not to prevent the hardware from making pte
  * updates, but to prevent any updates it may make from being lost.
  *
  * This does not protect against other software modifications of the
  * pte; the appropriate pte lock must be held over the transation.
  *
  * Note that this interface is intended to be batchable, meaning that
  * ptep_modify_prot_commit may not actually update the pte, but merely
  * queue the update to be done at some later time.  The update must be
  * actually committed before the pte lock is released, however.
  */
 static inline pte_t ptep_modify_prot_start(struct mm_struct *mm,
 					   unsigned long addr,
 					   pte_t *ptep)
 {
 	return __ptep_modify_prot_start(mm, addr, ptep);
 }

 /*
  * Commit an update to a pte, leaving any hardware-controlled bits in
  * the PTE unmodified.
  */
 static inline void ptep_modify_prot_commit(struct mm_struct *mm,
 					   unsigned long addr,
 					   pte_t *ptep, pte_t pte)
 {
 	__ptep_modify_prot_commit(mm, addr, ptep, pte);
 }
 #endif /* __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION */
 #endif /* CONFIG_MMU */

 /*
  * A facility to provide lazy MMU batching.  This allows PTE updates and
  * page invalidations to be delayed until a call to leave lazy MMU mode
  * is issued.  Some architectures may benefit from doing this, and it is
  * beneficial for both shadow and direct mode hypervisors, which may batch
  * the PTE updates which happen during this window.  Note that using this
  * interface requires that read hazards be removed from the code.  A read
  * hazard could result in the direct mode hypervisor case, since the actual
  * write to the page tables may not yet have taken place, so reads though
  * a raw PTE pointer after it has been modified are not guaranteed to be
  * up to date.  This mode can only be entered and left under the protection of
  * the page table locks for all page tables which may be modified.  In the UP
  * case, this is required so that preemption is disabled, and in the SMP case,
  * it must synchronize the delayed page table writes properly on other CPUs.
  */
 #ifndef __HAVE_ARCH_ENTER_LAZY_MMU_MODE
 #define arch_enter_lazy_mmu_mode()	do {} while (0)
 #define arch_leave_lazy_mmu_mode()	do {} while (0)
 #define arch_flush_lazy_mmu_mode()	do {} while (0)
 #endif

 /*
  * A facility to provide batching of the reload of page tables and
  * other process state with the actual context switch code for
  * paravirtualized guests.  By convention, only one of the batched
  * update (lazy) modes (CPU, MMU) should be active at any given time,
  * entry should never be nested, and entry and exits should always be
  * paired.  This is for sanity of maintaining and reasoning about the
  * kernel code.  In this case, the exit (end of the context switch) is
  * in architecture-specific code, and so doesn't need a generic
  * definition.
  */
 #ifndef __HAVE_ARCH_START_CONTEXT_SWITCH
 #define arch_start_context_switch(prev)	do {} while (0)
 #endif

 #ifndef CONFIG_HAVE_ARCH_SOFT_DIRTY
 static inline int pte_soft_dirty(pte_t pte)
 {
 	return 0;
 }

 static inline int pmd_soft_dirty(pmd_t pmd)
 {
 	return 0;
 }

 static inline pte_t pte_mksoft_dirty(pte_t pte)
 {
 	return pte;
 }

 static inline pmd_t pmd_mksoft_dirty(pmd_t pmd)
 {
 	return pmd;
 }

 static inline pte_t pte_clear_soft_dirty(pte_t pte)
 {
 	return pte;
 }

 static inline pmd_t pmd_clear_soft_dirty(pmd_t pmd)
 {
 	return pmd;
 }

 static inline pte_t pte_swp_mksoft_dirty(pte_t pte)
 {
 	return pte;
 }

 static inline int pte_swp_soft_dirty(pte_t pte)
 {
 	return 0;
 }

 static inline pte_t pte_swp_clear_soft_dirty(pte_t pte)
 {
 	return pte;
 }
 #endif

 #ifndef __HAVE_PFNMAP_TRACKING
 /*
  * Interfaces that can be used by architecture code to keep track of
  * memory type of pfn mappings specified by the remap_pfn_range,
  * vm_insert_pfn.
  */

 /*
  * track_pfn_remap is called when a _new_ pfn mapping is being established
  * by remap_pfn_range() for physical range indicated by pfn and size.
  */
 static inline int track_pfn_remap(struct vm_area_struct *vma, pgprot_t *prot,
 				  unsigned long pfn, unsigned long addr,
 				  unsigned long size)
 {
 	return 0;
 }

 /*
  * track_pfn_insert is called when a _new_ single pfn is established
  * by vm_insert_pfn().
  */
 static inline int track_pfn_insert(struct vm_area_struct *vma, pgprot_t *prot,
 				   unsigned long pfn)
 {
 	return 0;
 }

 /*
  * track_pfn_copy is called when vma that is covering the pfnmap gets
  * copied through copy_page_range().
  */
 static inline int track_pfn_copy(struct vm_area_struct *vma)
 {
 	return 0;
 }

 /*
  * untrack_pfn_vma is called while unmapping a pfnmap for a region.
  * untrack can be called for a specific region indicated by pfn and size or
  * can be for the entire vma (in which case pfn, size are zero).
  */
 static inline void untrack_pfn(struct vm_area_struct *vma,
 			       unsigned long pfn, unsigned long size)
 {
 }
 #else
 extern int track_pfn_remap(struct vm_area_struct *vma, pgprot_t *prot,
 			   unsigned long pfn, unsigned long addr,
 			   unsigned long size);
 extern int track_pfn_insert(struct vm_area_struct *vma, pgprot_t *prot,
 			    unsigned long pfn);
 extern int track_pfn_copy(struct vm_area_struct *vma);
 extern void untrack_pfn(struct vm_area_struct *vma, unsigned long pfn,
 			unsigned long size);
 #endif

 #ifdef __HAVE_COLOR_ZERO_PAGE
 static inline int is_zero_pfn(unsigned long pfn)
 {
 	extern unsigned long zero_pfn;
 	unsigned long offset_from_zero_pfn = pfn - zero_pfn;
 	return offset_from_zero_pfn <= (zero_page_mask >> PAGE_SHIFT);
 }

 #define my_zero_pfn(addr)	page_to_pfn(ZERO_PAGE(addr))

 #else
 static inline int is_zero_pfn(unsigned long pfn)
 {
 	extern unsigned long zero_pfn;
 	return pfn == zero_pfn;
 }

 static inline unsigned long my_zero_pfn(unsigned long addr)
 {
 	extern unsigned long zero_pfn;
 	return zero_pfn;
 }
 #endif

 #ifdef CONFIG_MMU

 #ifndef CONFIG_TRANSPARENT_HUGEPAGE
 static inline int pmd_trans_huge(pmd_t pmd)
 {
 	return 0;
 }
 static inline int pmd_trans_splitting(pmd_t pmd)
 {
 	return 0;
 }
 #ifndef __HAVE_ARCH_PMD_WRITE
 static inline int pmd_write(pmd_t pmd)
 {
 	BUG();
 	return 0;
 }
 #endif /* __HAVE_ARCH_PMD_WRITE */
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */

 #ifndef pmd_read_atomic
 static inline pmd_t pmd_read_atomic(pmd_t *pmdp)
 {
 	/*
 	 * Depend on compiler for an atomic pmd read. NOTE: this is
 	 * only going to work, if the pmdval_t isn't larger than
 	 * an unsigned long.
 	 */
 	return *pmdp;
 }
 #endif

 #ifndef pmd_move_must_withdraw
 static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
 					 spinlock_t *old_pmd_ptl)
 {
 	/*
 	 * With split pmd lock we also need to move preallocated
 	 * PTE page table if new_pmd is on different PMD page table.
 	 */
 	return new_pmd_ptl != old_pmd_ptl;
 }
 #endif

 /*
  * This function is meant to be used by sites walking pagetables with
  * the mmap_sem hold in read mode to protect against MADV_DONTNEED and
  * transhuge page faults. MADV_DONTNEED can convert a transhuge pmd
  * into a null pmd and the transhuge page fault can convert a null pmd
  * into an hugepmd or into a regular pmd (if the hugepage allocation
  * fails). While holding the mmap_sem in read mode the pmd becomes
  * stable and stops changing under us only if it's not null and not a
  * transhuge pmd. When those races occurs and this function makes a
  * difference vs the standard pmd_none_or_clear_bad, the result is
  * undefined so behaving like if the pmd was none is safe (because it
  * can return none anyway). The compiler level barrier() is critically
  * important to compute the two checks atomically on the same pmdval.
  *
  * For 32bit kernels with a 64bit large pmd_t this automatically takes
  * care of reading the pmd atomically to avoid SMP race conditions
  * against pmd_populate() when the mmap_sem is hold for reading by the
  * caller (a special atomic read not done by "gcc" as in the generic
  * version above, is also needed when THP is disabled because the page
  * fault can populate the pmd from under us).
  */
 static inline int pmd_none_or_trans_huge_or_clear_bad(pmd_t *pmd)
 {
 	pmd_t pmdval = pmd_read_atomic(pmd);
 	/*
 	 * The barrier will stabilize the pmdval in a register or on
 	 * the stack so that it will stop changing under the code.
 	 *
 	 * When CONFIG_TRANSPARENT_HUGEPAGE=y on x86 32bit PAE,
 	 * pmd_read_atomic is allowed to return a not atomic pmdval
 	 * (for example pointing to an hugepage that has never been
 	 * mapped in the pmd). The below checks will only care about
 	 * the low part of the pmd with 32bit PAE x86 anyway, with the
 	 * exception of pmd_none(). So the important thing is that if
 	 * the low part of the pmd is found null, the high part will
 	 * be also null or the pmd_none() check below would be
 	 * confused.
 	 */
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 	barrier();
 #endif
 	if (pmd_none(pmdval) || pmd_trans_huge(pmdval))
 		return 1;
 	if (unlikely(pmd_bad(pmdval))) {
 		pmd_clear_bad(pmd);
 		return 1;
 	}
 	return 0;
 }

 /*
  * This is a noop if Transparent Hugepage Support is not built into
  * the kernel. Otherwise it is equivalent to
  * pmd_none_or_trans_huge_or_clear_bad(), and shall only be called in
  * places that already verified the pmd is not none and they want to
  * walk ptes while holding the mmap sem in read mode (write mode don't
  * need this). If THP is not enabled, the pmd can't go away under the
  * code even if MADV_DONTNEED runs, but if THP is enabled we need to
  * run a pmd_trans_unstable before walking the ptes after
  * split_huge_page_pmd returns (because it may have run when the pmd
  * become null, but then a page fault can map in a THP and not a
  * regular page).
  */
 static inline int pmd_trans_unstable(pmd_t *pmd)
 {
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 	return pmd_none_or_trans_huge_or_clear_bad(pmd);
 #else
 	return 0;
 #endif
 }

 #ifndef CONFIG_NUMA_BALANCING
 /*
  * Technically a PTE can be PROTNONE even when not doing NUMA balancing but
  * the only case the kernel cares is for NUMA balancing and is only ever set
  * when the VMA is accessible. For PROT_NONE VMAs, the PTEs are not marked
  * _PAGE_PROTNONE so by by default, implement the helper as "always no". It
  * is the responsibility of the caller to distinguish between PROT_NONE
  * protections and NUMA hinting fault protections.
  */
 static inline int pte_protnone(pte_t pte)
 {
 	return 0;
 }

 static inline int pmd_protnone(pmd_t pmd)
 {
 	return 0;
 }
 #endif /* CONFIG_NUMA_BALANCING */

 #endif /* CONFIG_MMU */

 #ifdef CONFIG_HAVE_ARCH_HUGE_VMAP
 int pud_set_huge(pud_t *pud, phys_addr_t addr, pgprot_t prot);
 int pmd_set_huge(pmd_t *pmd, phys_addr_t addr, pgprot_t prot);
 int pud_clear_huge(pud_t *pud);
 int pmd_clear_huge(pmd_t *pmd);
 #else	/* !CONFIG_HAVE_ARCH_HUGE_VMAP */
 static inline int pud_set_huge(pud_t *pud, phys_addr_t addr, pgprot_t prot)
 {
 	return 0;
 }
 static inline int pmd_set_huge(pmd_t *pmd, phys_addr_t addr, pgprot_t prot)
 {
 	return 0;
 }
 static inline int pud_clear_huge(pud_t *pud)
 {
 	return 0;
 }
 static inline int pmd_clear_huge(pmd_t *pmd)
 {
 	return 0;
 }
 #endif	/* CONFIG_HAVE_ARCH_HUGE_VMAP */

 #endif /* !__ASSEMBLY__ */

 #ifndef io_remap_pfn_range
 #define io_remap_pfn_range remap_pfn_range
 #endif

 #endif /* _ASM_GENERIC_PGTABLE_H */
	#ifndef _ASM_GENERIC_PGTABLE_H
	#define _ASM_GENERIC_PGTABLE_H

	#ifndef __ASSEMBLY__
	#ifdef CONFIG_MMU

	#include <linux/mm_types.h>
	#include <linux/bug.h>
	#include <linux/errno.h>

	#if 4 - defined(__PAGETABLE_PUD_FOLDED) - defined(__PAGETABLE_PMD_FOLDED) != \
	CONFIG_PGTABLE_LEVELS
	#error CONFIG_PGTABLE_LEVELS is not consistent with __PAGETABLE_{PUD,PMD}_FOLDED
	#endif

	/*
	* On almost all architectures and configurations, 0 can be used as the
	* upper ceiling to free_pgtables(): on many architectures it has the same
	* effect as using TASK_SIZE. However, there is one configuration which
	* must impose a more careful limit, to avoid freeing kernel pgtables.
	*/
	#ifndef USER_PGTABLES_CEILING
	#define USER_PGTABLES_CEILING 0UL
	#endif

	#ifndef __HAVE_ARCH_PTEP_SET_ACCESS_FLAGS
	extern int ptep_set_access_flags(struct vm_area_struct *vma,
	unsigned long address, pte_t *ptep,
	pte_t entry, int dirty);
	#endif

	#ifndef __HAVE_ARCH_PMDP_SET_ACCESS_FLAGS
	extern int pmdp_set_access_flags(struct vm_area_struct *vma,
	unsigned long address, pmd_t *pmdp,
	pmd_t entry, int dirty);
	#endif

	#ifndef __HAVE_ARCH_PTEP_TEST_AND_CLEAR_YOUNG
	static inline int ptep_test_and_clear_young(struct vm_area_struct *vma,
	unsigned long address,
	pte_t *ptep)
	{
	pte_t pte = *ptep;
	int r = 1;
	if (!pte_young(pte))
	r = 0;
	else
	set_pte_at(vma->vm_mm, address, ptep, pte_mkold(pte));
	return r;
	}
	#endif

	#ifndef __HAVE_ARCH_PMDP_TEST_AND_CLEAR_YOUNG
	#ifdef CONFIG_TRANSPARENT_HUGEPAGE
	static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma,
	unsigned long address,
	pmd_t *pmdp)
	{
	pmd_t pmd = *pmdp;
	int r = 1;
	if (!pmd_young(pmd))
	r = 0;
	else
	set_pmd_at(vma->vm_mm, address, pmdp, pmd_mkold(pmd));
	return r;
	}
	#else /* CONFIG_TRANSPARENT_HUGEPAGE */
	static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma,
	unsigned long address,
	pmd_t *pmdp)
	{
	BUG();
	return 0;
	}
	#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
	#endif

	#ifndef __HAVE_ARCH_PTEP_CLEAR_YOUNG_FLUSH
	int ptep_clear_flush_young(struct vm_area_struct *vma,
	unsigned long address, pte_t *ptep);
	#endif

	#ifndef __HAVE_ARCH_PMDP_CLEAR_YOUNG_FLUSH
	int pmdp_clear_flush_young(struct vm_area_struct *vma,
	unsigned long address, pmd_t *pmdp);
	#endif

	#ifndef __HAVE_ARCH_PTEP_GET_AND_CLEAR
	static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
	unsigned long address,
	pte_t *ptep)
	{
	pte_t pte = *ptep;
	pte_clear(mm, address, ptep);
	return pte;
	}
	#endif

	#ifndef __HAVE_ARCH_PMDP_HUGE_GET_AND_CLEAR
	#ifdef CONFIG_TRANSPARENT_HUGEPAGE
	static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm,
	unsigned long address,
	pmd_t *pmdp)
	{
	pmd_t pmd = *pmdp;
	pmd_clear(pmdp);
	return pmd;
	}
	#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
	#endif

	#ifndef __HAVE_ARCH_PMDP_HUGE_GET_AND_CLEAR_FULL
	#ifdef CONFIG_TRANSPARENT_HUGEPAGE
	static inline pmd_t pmdp_huge_get_and_clear_full(struct mm_struct *mm,
	unsigned long address, pmd_t *pmdp,
	int full)
	{
	return pmdp_huge_get_and_clear(mm, address, pmdp);
	}
	#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
	#endif

	#ifndef __HAVE_ARCH_PTEP_GET_AND_CLEAR_FULL
	static inline pte_t ptep_get_and_clear_full(struct mm_struct *mm,
	unsigned long address, pte_t *ptep,
	int full)
	{
	pte_t pte;
	pte = ptep_get_and_clear(mm, address, ptep);
	return pte;
	}
	#endif

	/*
	* Some architectures may be able to avoid expensive synchronization
	* primitives when modifications are made to PTE's which are already
	* not present, or in the process of an address space destruction.
	*/
	#ifndef __HAVE_ARCH_PTE_CLEAR_NOT_PRESENT_FULL
	static inline void pte_clear_not_present_full(struct mm_struct *mm,
	unsigned long address,
	pte_t *ptep,
	int full)
	{
	pte_clear(mm, address, ptep);
	}
	#endif

	#ifndef __HAVE_ARCH_PTEP_CLEAR_FLUSH
	extern pte_t ptep_clear_flush(struct vm_area_struct *vma,
	unsigned long address,
	pte_t *ptep);
	#endif

	#ifndef __HAVE_ARCH_PMDP_HUGE_CLEAR_FLUSH
	extern pmd_t pmdp_huge_clear_flush(struct vm_area_struct *vma,
	unsigned long address,
	pmd_t *pmdp);
	#endif

	#ifndef __HAVE_ARCH_PTEP_SET_WRPROTECT
	struct mm_struct;
	static inline void ptep_set_wrprotect(struct mm_struct mm, unsigned long address, pte_t ptep)
	{
	pte_t old_pte = *ptep;
	set_pte_at(mm, address, ptep, pte_wrprotect(old_pte));
	}
	#endif

	#ifndef __HAVE_ARCH_PMDP_SET_WRPROTECT
	#ifdef CONFIG_TRANSPARENT_HUGEPAGE
	static inline void pmdp_set_wrprotect(struct mm_struct *mm,
	unsigned long address, pmd_t *pmdp)
	{
	pmd_t old_pmd = *pmdp;
	set_pmd_at(mm, address, pmdp, pmd_wrprotect(old_pmd));
	}
	#else /* CONFIG_TRANSPARENT_HUGEPAGE */
	static inline void pmdp_set_wrprotect(struct mm_struct *mm,
	unsigned long address, pmd_t *pmdp)
	{
	BUG();
	}
	#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
	#endif

	#ifndef __HAVE_ARCH_PMDP_SPLITTING_FLUSH
	extern void pmdp_splitting_flush(struct vm_area_struct *vma,
	unsigned long address, pmd_t *pmdp);
	#endif

	#ifndef pmdp_collapse_flush
	#ifdef CONFIG_TRANSPARENT_HUGEPAGE
	extern pmd_t pmdp_collapse_flush(struct vm_area_struct *vma,
	unsigned long address, pmd_t *pmdp);
	#else
	static inline pmd_t pmdp_collapse_flush(struct vm_area_struct *vma,
	unsigned long address,
	pmd_t *pmdp)
	{
	BUILD_BUG();
	return *pmdp;
	}
	#define pmdp_collapse_flush pmdp_collapse_flush
	#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
	#endif

	#ifndef __HAVE_ARCH_PGTABLE_DEPOSIT
	extern void pgtable_trans_huge_deposit(struct mm_struct mm, pmd_t pmdp,
	pgtable_t pgtable);
	#endif

	#ifndef __HAVE_ARCH_PGTABLE_WITHDRAW
	extern pgtable_t pgtable_trans_huge_withdraw(struct mm_struct mm, pmd_t pmdp);
	#endif

	#ifndef __HAVE_ARCH_PMDP_INVALIDATE
	extern void pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
	pmd_t *pmdp);
	#endif

	#ifndef __HAVE_ARCH_PTE_SAME
	static inline int pte_same(pte_t pte_a, pte_t pte_b)
	{
	return pte_val(pte_a) == pte_val(pte_b);
	}
	#endif

	#ifndef __HAVE_ARCH_PTE_UNUSED
	/*
	* Some architectures provide facilities to virtualization guests
	* so that they can flag allocated pages as unused. This allows the
	* host to transparently reclaim unused pages. This function returns
	* whether the pte's page is unused.
	*/
	static inline int pte_unused(pte_t pte)
	{
	return 0;
	}
	#endif

	#ifndef __HAVE_ARCH_PMD_SAME
	#ifdef CONFIG_TRANSPARENT_HUGEPAGE
	static inline int pmd_same(pmd_t pmd_a, pmd_t pmd_b)
	{
	return pmd_val(pmd_a) == pmd_val(pmd_b);
	}
	#else /* CONFIG_TRANSPARENT_HUGEPAGE */
	static inline int pmd_same(pmd_t pmd_a, pmd_t pmd_b)
	{
	BUG();
	return 0;
	}
	#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
	#endif

	#ifndef __HAVE_ARCH_PGD_OFFSET_GATE
	#define pgd_offset_gate(mm, addr) pgd_offset(mm, addr)
	#endif

	#ifndef __HAVE_ARCH_MOVE_PTE
	#define move_pte(pte, prot, old_addr, new_addr) (pte)
	#endif

	#ifndef pte_accessible
	# define pte_accessible(mm, pte) ((void)(pte), 1)
	#endif

	#ifndef flush_tlb_fix_spurious_fault
	#define flush_tlb_fix_spurious_fault(vma, address) flush_tlb_page(vma, address)
	#endif

	#ifndef pgprot_noncached
	#define pgprot_noncached(prot) (prot)
	#endif

	#ifndef pgprot_writecombine
	#define pgprot_writecombine pgprot_noncached
	#endif

	#ifndef pgprot_writethrough
	#define pgprot_writethrough pgprot_noncached
	#endif

	#ifndef pgprot_device
	#define pgprot_device pgprot_noncached
	#endif

	#ifndef pgprot_modify
	#define pgprot_modify pgprot_modify
	static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot)
	{
	if (pgprot_val(oldprot) == pgprot_val(pgprot_noncached(oldprot)))
	newprot = pgprot_noncached(newprot);
	if (pgprot_val(oldprot) == pgprot_val(pgprot_writecombine(oldprot)))
	newprot = pgprot_writecombine(newprot);
	if (pgprot_val(oldprot) == pgprot_val(pgprot_device(oldprot)))
	newprot = pgprot_device(newprot);
	return newprot;
	}
	#endif

	/*
	* When walking page tables, get the address of the next boundary,
	* or the end address of the range if that comes earlier. Although no
	* vma end wraps to 0, rounded up __boundary may wrap to 0 throughout.
	*/

	#define pgd_addr_end(addr, end) \
	({ unsigned long __boundary = ((addr) + PGDIR_SIZE) & PGDIR_MASK; \
	(__boundary - 1 < (end) - 1)? __boundary: (end); \
	})

	#ifndef pud_addr_end
	#define pud_addr_end(addr, end) \
	({ unsigned long __boundary = ((addr) + PUD_SIZE) & PUD_MASK; \
	(__boundary - 1 < (end) - 1)? __boundary: (end); \
	})
	#endif

	#ifndef pmd_addr_end
	#define pmd_addr_end(addr, end) \
	({ unsigned long __boundary = ((addr) + PMD_SIZE) & PMD_MASK; \
	(__boundary - 1 < (end) - 1)? __boundary: (end); \
	})
	#endif

	/*
	* When walking page tables, we usually want to skip any p?d_none entries;
	* and any p?d_bad entries - reporting the error before resetting to none.
	* Do the tests inline, but report and clear the bad entry in mm/memory.c.
	*/
	void pgd_clear_bad(pgd_t *);
	void pud_clear_bad(pud_t *);
	void pmd_clear_bad(pmd_t *);

	static inline int pgd_none_or_clear_bad(pgd_t *pgd)
	{
	if (pgd_none(*pgd))
	return 1;
	if (unlikely(pgd_bad(*pgd))) {
	pgd_clear_bad(pgd);
	return 1;
	}
	return 0;
	}

	static inline int pud_none_or_clear_bad(pud_t *pud)
	{
	if (pud_none(*pud))
	return 1;
	if (unlikely(pud_bad(*pud))) {
	pud_clear_bad(pud);
	return 1;
	}
	return 0;
	}

	static inline int pmd_none_or_clear_bad(pmd_t *pmd)
	{
	if (pmd_none(*pmd))
	return 1;
	if (unlikely(pmd_bad(*pmd))) {
	pmd_clear_bad(pmd);
	return 1;
	}
	return 0;
	}

	static inline pte_t __ptep_modify_prot_start(struct mm_struct *mm,
	unsigned long addr,
	pte_t *ptep)
	{
	/*
	* Get the current pte state, but zero it out to make it
	* non-present, preventing the hardware from asynchronously
	* updating it.
	*/
	return ptep_get_and_clear(mm, addr, ptep);
	}

	static inline void __ptep_modify_prot_commit(struct mm_struct *mm,
	unsigned long addr,
	pte_t *ptep, pte_t pte)
	{
	/*
	* The pte is non-present, so there's no hardware state to
	* preserve.
	*/
	set_pte_at(mm, addr, ptep, pte);
	}

	#ifndef __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION
	/*
	* Start a pte protection read-modify-write transaction, which
	* protects against asynchronous hardware modifications to the pte.
	* The intention is not to prevent the hardware from making pte
	* updates, but to prevent any updates it may make from being lost.
	*
	* This does not protect against other software modifications of the
	* pte; the appropriate pte lock must be held over the transation.
	*
	* Note that this interface is intended to be batchable, meaning that
	* ptep_modify_prot_commit may not actually update the pte, but merely
	* queue the update to be done at some later time. The update must be
	* actually committed before the pte lock is released, however.
	*/
	static inline pte_t ptep_modify_prot_start(struct mm_struct *mm,
	unsigned long addr,
	pte_t *ptep)
	{
	return __ptep_modify_prot_start(mm, addr, ptep);
	}

	/*
	* Commit an update to a pte, leaving any hardware-controlled bits in
	* the PTE unmodified.
	*/
	static inline void ptep_modify_prot_commit(struct mm_struct *mm,
	unsigned long addr,
	pte_t *ptep, pte_t pte)
	{
	__ptep_modify_prot_commit(mm, addr, ptep, pte);
	}
	#endif /* __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION */
	#endif /* CONFIG_MMU */

	/*
	* A facility to provide lazy MMU batching. This allows PTE updates and
	* page invalidations to be delayed until a call to leave lazy MMU mode
	* is issued. Some architectures may benefit from doing this, and it is
	* beneficial for both shadow and direct mode hypervisors, which may batch
	* the PTE updates which happen during this window. Note that using this
	* interface requires that read hazards be removed from the code. A read
	* hazard could result in the direct mode hypervisor case, since the actual
	* write to the page tables may not yet have taken place, so reads though
	* a raw PTE pointer after it has been modified are not guaranteed to be
	* up to date. This mode can only be entered and left under the protection of
	* the page table locks for all page tables which may be modified. In the UP
	* case, this is required so that preemption is disabled, and in the SMP case,
	* it must synchronize the delayed page table writes properly on other CPUs.
	*/
	#ifndef __HAVE_ARCH_ENTER_LAZY_MMU_MODE
	#define arch_enter_lazy_mmu_mode() do {} while (0)
	#define arch_leave_lazy_mmu_mode() do {} while (0)
	#define arch_flush_lazy_mmu_mode() do {} while (0)
	#endif

	/*
	* A facility to provide batching of the reload of page tables and
	* other process state with the actual context switch code for
	* paravirtualized guests. By convention, only one of the batched
	* update (lazy) modes (CPU, MMU) should be active at any given time,
	* entry should never be nested, and entry and exits should always be
	* paired. This is for sanity of maintaining and reasoning about the
	* kernel code. In this case, the exit (end of the context switch) is
	* in architecture-specific code, and so doesn't need a generic
	* definition.
	*/
	#ifndef __HAVE_ARCH_START_CONTEXT_SWITCH
	#define arch_start_context_switch(prev) do {} while (0)
	#endif

	#ifndef CONFIG_HAVE_ARCH_SOFT_DIRTY
	static inline int pte_soft_dirty(pte_t pte)
	{
	return 0;
	}

	static inline int pmd_soft_dirty(pmd_t pmd)
	{
	return 0;
	}

	static inline pte_t pte_mksoft_dirty(pte_t pte)
	{
	return pte;
	}

	static inline pmd_t pmd_mksoft_dirty(pmd_t pmd)
	{
	return pmd;
	}

	static inline pte_t pte_clear_soft_dirty(pte_t pte)
	{
	return pte;
	}

	static inline pmd_t pmd_clear_soft_dirty(pmd_t pmd)
	{
	return pmd;
	}

	static inline pte_t pte_swp_mksoft_dirty(pte_t pte)
	{
	return pte;
	}

	static inline int pte_swp_soft_dirty(pte_t pte)
	{
	return 0;
	}

	static inline pte_t pte_swp_clear_soft_dirty(pte_t pte)
	{
	return pte;
	}
	#endif

	#ifndef __HAVE_PFNMAP_TRACKING
	/*
	* Interfaces that can be used by architecture code to keep track of
	* memory type of pfn mappings specified by the remap_pfn_range,
	* vm_insert_pfn.
	*/

	/*
	* track_pfn_remap is called when a _new_ pfn mapping is being established
	* by remap_pfn_range() for physical range indicated by pfn and size.
	*/
	static inline int track_pfn_remap(struct vm_area_struct vma, pgprot_t prot,
	unsigned long pfn, unsigned long addr,
	unsigned long size)
	{
	return 0;
	}

	/*
	* track_pfn_insert is called when a _new_ single pfn is established
	* by vm_insert_pfn().
	*/
	static inline int track_pfn_insert(struct vm_area_struct vma, pgprot_t prot,
	unsigned long pfn)
	{
	return 0;
	}

	/*
	* track_pfn_copy is called when vma that is covering the pfnmap gets
	* copied through copy_page_range().
	*/
	static inline int track_pfn_copy(struct vm_area_struct *vma)
	{
	return 0;
	}

	/*
	* untrack_pfn_vma is called while unmapping a pfnmap for a region.
	* untrack can be called for a specific region indicated by pfn and size or
	* can be for the entire vma (in which case pfn, size are zero).
	*/
	static inline void untrack_pfn(struct vm_area_struct *vma,
	unsigned long pfn, unsigned long size)
	{
	}
	#else
	extern int track_pfn_remap(struct vm_area_struct vma, pgprot_t prot,
	unsigned long pfn, unsigned long addr,
	unsigned long size);
	extern int track_pfn_insert(struct vm_area_struct vma, pgprot_t prot,
	unsigned long pfn);
	extern int track_pfn_copy(struct vm_area_struct *vma);
	extern void untrack_pfn(struct vm_area_struct *vma, unsigned long pfn,
	unsigned long size);
	#endif

	#ifdef __HAVE_COLOR_ZERO_PAGE
	static inline int is_zero_pfn(unsigned long pfn)
	{
	extern unsigned long zero_pfn;
	unsigned long offset_from_zero_pfn = pfn - zero_pfn;
	return offset_from_zero_pfn <= (zero_page_mask >> PAGE_SHIFT);
	}

	#define my_zero_pfn(addr) page_to_pfn(ZERO_PAGE(addr))

	#else
	static inline int is_zero_pfn(unsigned long pfn)
	{
	extern unsigned long zero_pfn;
	return pfn == zero_pfn;
	}

	static inline unsigned long my_zero_pfn(unsigned long addr)
	{
	extern unsigned long zero_pfn;
	return zero_pfn;
	}
	#endif

	#ifdef CONFIG_MMU

	#ifndef CONFIG_TRANSPARENT_HUGEPAGE
	static inline int pmd_trans_huge(pmd_t pmd)
	{
	return 0;
	}
	static inline int pmd_trans_splitting(pmd_t pmd)
	{
	return 0;
	}
	#ifndef __HAVE_ARCH_PMD_WRITE
	static inline int pmd_write(pmd_t pmd)
	{
	BUG();
	return 0;
	}
	#endif /* __HAVE_ARCH_PMD_WRITE */
	#endif /* CONFIG_TRANSPARENT_HUGEPAGE */

	#ifndef pmd_read_atomic
	static inline pmd_t pmd_read_atomic(pmd_t *pmdp)
	{
	/*
	* Depend on compiler for an atomic pmd read. NOTE: this is
	* only going to work, if the pmdval_t isn't larger than
	* an unsigned long.
	*/
	return *pmdp;
	}
	#endif

	#ifndef pmd_move_must_withdraw
	static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
	spinlock_t *old_pmd_ptl)
	{
	/*
	* With split pmd lock we also need to move preallocated
	* PTE page table if new_pmd is on different PMD page table.
	*/
	return new_pmd_ptl != old_pmd_ptl;
	}
	#endif

	/*
	* This function is meant to be used by sites walking pagetables with
	* the mmap_sem hold in read mode to protect against MADV_DONTNEED and
	* transhuge page faults. MADV_DONTNEED can convert a transhuge pmd
	* into a null pmd and the transhuge page fault can convert a null pmd
	* into an hugepmd or into a regular pmd (if the hugepage allocation
	* fails). While holding the mmap_sem in read mode the pmd becomes
	* stable and stops changing under us only if it's not null and not a
	* transhuge pmd. When those races occurs and this function makes a
	* difference vs the standard pmd_none_or_clear_bad, the result is
	* undefined so behaving like if the pmd was none is safe (because it
	* can return none anyway). The compiler level barrier() is critically
	* important to compute the two checks atomically on the same pmdval.
	*
	* For 32bit kernels with a 64bit large pmd_t this automatically takes
	* care of reading the pmd atomically to avoid SMP race conditions
	* against pmd_populate() when the mmap_sem is hold for reading by the
	* caller (a special atomic read not done by "gcc" as in the generic
	* version above, is also needed when THP is disabled because the page
	* fault can populate the pmd from under us).
	*/
	static inline int pmd_none_or_trans_huge_or_clear_bad(pmd_t *pmd)
	{
	pmd_t pmdval = pmd_read_atomic(pmd);
	/*
	* The barrier will stabilize the pmdval in a register or on
	* the stack so that it will stop changing under the code.
	*
	* When CONFIG_TRANSPARENT_HUGEPAGE=y on x86 32bit PAE,
	* pmd_read_atomic is allowed to return a not atomic pmdval
	* (for example pointing to an hugepage that has never been
	* mapped in the pmd). The below checks will only care about
	* the low part of the pmd with 32bit PAE x86 anyway, with the
	* exception of pmd_none(). So the important thing is that if
	* the low part of the pmd is found null, the high part will
	* be also null or the pmd_none() check below would be
	* confused.
	*/
	#ifdef CONFIG_TRANSPARENT_HUGEPAGE
	barrier();
	#endif
	if (pmd_none(pmdval) \|\| pmd_trans_huge(pmdval))
	return 1;
	if (unlikely(pmd_bad(pmdval))) {
	pmd_clear_bad(pmd);
	return 1;
	}
	return 0;
	}

	/*
	* This is a noop if Transparent Hugepage Support is not built into
	* the kernel. Otherwise it is equivalent to
	* pmd_none_or_trans_huge_or_clear_bad(), and shall only be called in
	* places that already verified the pmd is not none and they want to
	* walk ptes while holding the mmap sem in read mode (write mode don't
	* need this). If THP is not enabled, the pmd can't go away under the
	* code even if MADV_DONTNEED runs, but if THP is enabled we need to
	* run a pmd_trans_unstable before walking the ptes after
	* split_huge_page_pmd returns (because it may have run when the pmd
	* become null, but then a page fault can map in a THP and not a
	* regular page).
	*/
	static inline int pmd_trans_unstable(pmd_t *pmd)
	{
	#ifdef CONFIG_TRANSPARENT_HUGEPAGE
	return pmd_none_or_trans_huge_or_clear_bad(pmd);
	#else
	return 0;
	#endif
	}

	#ifndef CONFIG_NUMA_BALANCING
	/*
	* Technically a PTE can be PROTNONE even when not doing NUMA balancing but
	* the only case the kernel cares is for NUMA balancing and is only ever set
	* when the VMA is accessible. For PROT_NONE VMAs, the PTEs are not marked
	* _PAGE_PROTNONE so by by default, implement the helper as "always no". It
	* is the responsibility of the caller to distinguish between PROT_NONE
	* protections and NUMA hinting fault protections.
	*/
	static inline int pte_protnone(pte_t pte)
	{
	return 0;
	}

	static inline int pmd_protnone(pmd_t pmd)
	{
	return 0;
	}
	#endif /* CONFIG_NUMA_BALANCING */

	#endif /* CONFIG_MMU */

	#ifdef CONFIG_HAVE_ARCH_HUGE_VMAP
	int pud_set_huge(pud_t *pud, phys_addr_t addr, pgprot_t prot);
	int pmd_set_huge(pmd_t *pmd, phys_addr_t addr, pgprot_t prot);
	int pud_clear_huge(pud_t *pud);
	int pmd_clear_huge(pmd_t *pmd);
	#else /* !CONFIG_HAVE_ARCH_HUGE_VMAP */
	static inline int pud_set_huge(pud_t *pud, phys_addr_t addr, pgprot_t prot)
	{
	return 0;
	}
	static inline int pmd_set_huge(pmd_t *pmd, phys_addr_t addr, pgprot_t prot)
	{
	return 0;
	}
	static inline int pud_clear_huge(pud_t *pud)
	{
	return 0;
	}
	static inline int pmd_clear_huge(pmd_t *pmd)
	{
	return 0;
	}
	#endif /* CONFIG_HAVE_ARCH_HUGE_VMAP */

	#endif /* !__ASSEMBLY__ */

	#ifndef io_remap_pfn_range
	#define io_remap_pfn_range remap_pfn_range
	#endif

	#endif /* _ASM_GENERIC_PGTABLE_H */