Re: [PATCH] mmu notifiers #v7

[Peter Zijlstra]

On Wed, 2008-02-27 at 20:26 +0100, Andrea Arcangeli wrote:
> Hello,
> 
> I hope this will can be considered final for .25 and be merged. Risk
> is zero, the only discussion here is to make an API that will last
> forever, functionality-wise all these patches provides zero risk and
> zero overhead when MMU_NOTIFIER=n. This last patch covers KVM and GRU
> and hopefully all other non-blocking users optimally, and the below
> API will hopefully last forever (but even if it lasts just for .25 and
> ..26 is changed that's fine with us, it's a kernel _internal_ API
> anyway, there's absolutely nothing visible to userland).
> 
> What Christoph need to do when he's back from vacations to support
> sleepable mmu notifiers is to add a CONFIG_XPMEM config option that
> will switch the i_mmap_lock from a semaphore to a mutex (any other
> change to this patch will be minor compared to that) so XPMEM hardware
> will have kernels compiled that way. I don't see other sane ways to
> remove the "atomic" parameter from the API (apparently required by
> Andrew for merging something not restricted to the xpmem current usage
> with only anonymous memory) and I don't want to have such a
> locking-change intrusive dependency for all other non-blocking users
> that are fine without having to alter how the VM works (for example
> KVM and GRU). Very minor changes will be required to this patch to
> make it work after the VM locking will be altered (for example the
> CONFIG_XPMEM should also switch the mmu_register/unregister locking
> from RCU to mutex as well). XPMEM then will only compile if
> CONFIG_XPMEM=y and in turn the invalidate_range_* will support
> scheduling inside.
> 
> I don't think pretending to merge all in one block (I mean including
> xpmem support that requires blocking methods) is good idea anymore as
> long as we agree the "atomic" parameter shouldn't be merged. But we
> can quite easily agree on the below to be optimal for GRU/KVM and
> trivially extendible once a CONFIG_XPMEM will be added. So this first
> part can go in now I think.
> 
> Signed-off-by: Andrea Arcangeli <andrea@xxxxxxxxxxxx>
> Signed-off-by: Christoph Lameter <clameter@xxxxxxx>

Acked-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>

> 
> diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
> --- a/include/linux/mm_types.h
> +++ b/include/linux/mm_types.h
> @@ -10,6 +10,7 @@
>  #include <linux/rbtree.h>
>  #include <linux/rwsem.h>
>  #include <linux/completion.h>
> +#include <linux/mmu_notifier.h>
>  #include <asm/page.h>
>  #include <asm/mmu.h>
>  
> @@ -228,6 +229,8 @@ struct mm_struct {
>  #ifdef CONFIG_CGROUP_MEM_CONT
>  	struct mem_cgroup *mem_cgroup;
>  #endif
> +
> +	struct mmu_notifier_head mmu_notifier; /* MMU notifier list */
>  };
>  
>  #endif /* _LINUX_MM_TYPES_H */
> diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
> new file mode 100644
> --- /dev/null
> +++ b/include/linux/mmu_notifier.h
> @@ -0,0 +1,159 @@
> +#ifndef _LINUX_MMU_NOTIFIER_H
> +#define _LINUX_MMU_NOTIFIER_H
> +
> +#include <linux/list.h>
> +#include <linux/spinlock.h>
> +
> +struct mmu_notifier;
> +
> +struct mmu_notifier_ops {
> +	/*
> +	 * Called when nobody can register any more notifier in the mm
> +	 * and after the "mn" notifier has been disarmed already.
> +	 */
> +	void (*release)(struct mmu_notifier *mn,
> +			struct mm_struct *mm);
> +
> +	/*
> +	 * invalidate_page is called in atomic context after any pte
> +	 * has been updated and before dropping the PT lock required
> +	 * to update any Linux pte.  Once the PT lock will be released
> +	 * the pte will have its final value to export through the
> +	 * secondary MMU.  Before this is invoked any secondary MMU is
> +	 * still ok to read/write to the page previously pointed by
> +	 * the Linux pte because the old page hasn't been freed yet.
> +	 * 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);
> +
> +	/*
> +	 * Age page is called in atomic context inside the PT lock
> +	 * right 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 (*age_page)(struct mmu_notifier *mn,
> +			struct mm_struct *mm,
> +			unsigned long address);
> +
> +	/*
> +	 * invalidate_range_begin() and invalidate_range_end() must be
> +	 * paired. Multiple invalidate_range_begin/ends may be nested
> +	 * or called concurrently.
> +	 */
> +	void (*invalidate_range_begin)(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);
> +};
> +
> +struct mmu_notifier {
> +	struct hlist_node hlist;
> +	const struct mmu_notifier_ops *ops;
> +};
> +
> +#ifdef CONFIG_MMU_NOTIFIER
> +
> +struct mmu_notifier_head {
> +	struct hlist_head head;
> +	spinlock_t lock;
> +};
> +
> +#include <linux/mm_types.h>
> +
> +/*
> + * RCU is used to traverse the list. A quiescent period needs to pass
> + * before the notifier is guaranteed to be visible to all threads.
> + */
> +extern void mmu_notifier_register(struct mmu_notifier *mn,
> +				  struct mm_struct *mm);
> +/*
> + * RCU is used to traverse the list. A quiescent period needs to pass
> + * before the "struct mmu_notifier" can be freed. Alternatively it
> + * can be synchronously freed inside ->release when the list can't
> + * change anymore and nobody could possibly walk it.
> + */
> +extern void mmu_notifier_unregister(struct mmu_notifier *mn,
> +				    struct mm_struct *mm);
> +extern void mmu_notifier_release(struct mm_struct *mm);
> +extern int mmu_notifier_age_page(struct mm_struct *mm,
> +				 unsigned long address);
> +
> +static inline void mmu_notifier_head_init(struct mmu_notifier_head *mnh)
> +{
> +	INIT_HLIST_HEAD(&mnh->head);
> +	spin_lock_init(&mnh->lock);
> +}
> +
> +#define mmu_notifier(function, mm, args...)				\
> +	do {								\
> +		struct mmu_notifier *__mn;				\
> +		struct hlist_node *__n;					\
> +									\
> +		if (unlikely(!hlist_empty(&(mm)->mmu_notifier.head))) { \
> +			rcu_read_lock();				\
> +			hlist_for_each_entry_rcu(__mn, __n,		\
> +						 &(mm)->mmu_notifier.head, \
> +						 hlist)			\
> +				if (__mn->ops->function)		\
> +					__mn->ops->function(__mn,	\
> +							    mm,		\
> +							    args);	\
> +			rcu_read_unlock();				\
> +		}							\
> +	} while (0)
> +
> +#define ptep_clear_flush_notify(__vma, __address, __ptep)		\
> +({									\
> +	pte_t __pte;							\
> +	__pte = ptep_clear_flush(__vma, __address, __ptep);		\
> +	mmu_notifier(invalidate_page, (__vma)->vm_mm, __address);	\
> +	__pte;								\
> +})
> +
> +#define ptep_clear_flush_young_notify(__vma, __address, __ptep)		\
> +({									\
> +	int __young;							\
> +	__young = ptep_clear_flush_young(__vma, __address, __ptep);	\
> +	__young |= mmu_notifier_age_page((__vma)->vm_mm, __address);	\
> +	__young;							\
> +})
> +
> +#else /* CONFIG_MMU_NOTIFIER */
> +
> +struct mmu_notifier_head {};
> +
> +#define mmu_notifier_register(mn, mm) do {} while(0)
> +#define mmu_notifier_unregister(mn, mm) do {} while (0)
> +#define mmu_notifier_release(mm) do {} while (0)
> +#define mmu_notifier_age_page(mm, address) ({ 0; })
> +#define mmu_notifier_head_init(mmh) do {} while (0)
> +
> +/*
> + * Notifiers that use the parameters that they were passed so that the
> + * compiler does not complain about unused variables but does proper
> + * parameter checks even if !CONFIG_MMU_NOTIFIER.
> + * Macros generate no code.
> + */
> +#define mmu_notifier(function, mm, args...)			       \
> +	do {							       \
> +		if (0) {					       \
> +			struct mmu_notifier *__mn;		       \
> +								       \
> +			__mn = (struct mmu_notifier *)(0x00ff);	       \
> +			__mn->ops->function(__mn, mm, args);	       \
> +		};						       \
> +	} while (0)
> +
> +#define ptep_clear_flush_young_notify ptep_clear_flush_young
> +#define ptep_clear_flush_notify ptep_clear_flush
> +
> +#endif /* CONFIG_MMU_NOTIFIER */
> +
> +#endif /* _LINUX_MMU_NOTIFIER_H */
> diff --git a/kernel/fork.c b/kernel/fork.c
> --- a/kernel/fork.c
> +++ b/kernel/fork.c
> @@ -362,6 +362,7 @@ static struct mm_struct * mm_init(struct
>  
>  	if (likely(!mm_alloc_pgd(mm))) {
>  		mm->def_flags = 0;
> +		mmu_notifier_head_init(&mm->mmu_notifier);
>  		return mm;
>  	}
>  
> diff --git a/mm/Kconfig b/mm/Kconfig
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -193,3 +193,7 @@ config VIRT_TO_BUS
>  config VIRT_TO_BUS
>  	def_bool y
>  	depends on !ARCH_NO_VIRT_TO_BUS
> +
> +config MMU_NOTIFIER
> +	def_bool y
> +	bool "MMU notifier, for paging KVM/RDMA"
> diff --git a/mm/Makefile b/mm/Makefile
> --- a/mm/Makefile
> +++ b/mm/Makefile
> @@ -33,4 +33,4 @@ obj-$(CONFIG_SMP) += allocpercpu.o
>  obj-$(CONFIG_SMP) += allocpercpu.o
>  obj-$(CONFIG_QUICKLIST) += quicklist.o
>  obj-$(CONFIG_CGROUP_MEM_CONT) += memcontrol.o
> -
> +obj-$(CONFIG_MMU_NOTIFIER) += mmu_notifier.o
> diff --git a/mm/filemap_xip.c b/mm/filemap_xip.c
> --- a/mm/filemap_xip.c
> +++ b/mm/filemap_xip.c
> @@ -194,7 +194,7 @@ __xip_unmap (struct address_space * mapp
>  		if (pte) {
>  			/* Nuke the page table entry. */
>  			flush_cache_page(vma, address, pte_pfn(*pte));
> -			pteval = ptep_clear_flush(vma, address, pte);
> +			pteval = ptep_clear_flush_notify(vma, address, pte);
>  			page_remove_rmap(page, vma);
>  			dec_mm_counter(mm, file_rss);
>  			BUG_ON(pte_dirty(pteval));
> diff --git a/mm/fremap.c b/mm/fremap.c
> --- a/mm/fremap.c
> +++ b/mm/fremap.c
> @@ -214,7 +214,9 @@ asmlinkage long sys_remap_file_pages(uns
>  		spin_unlock(&mapping->i_mmap_lock);
>  	}
>  
> +	mmu_notifier(invalidate_range_begin, mm, start, start + size);
>  	err = populate_range(mm, vma, start, size, pgoff);
> +	mmu_notifier(invalidate_range_end, mm, start, start + size);
>  	if (!err && !(flags & MAP_NONBLOCK)) {
>  		if (unlikely(has_write_lock)) {
>  			downgrade_write(&mm->mmap_sem);
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -755,6 +755,7 @@ void __unmap_hugepage_range(struct vm_ar
>  	BUG_ON(start & ~HPAGE_MASK);
>  	BUG_ON(end & ~HPAGE_MASK);
>  
> +	mmu_notifier(invalidate_range_begin, mm, start, end);
>  	spin_lock(&mm->page_table_lock);
>  	for (address = start; address < end; address += HPAGE_SIZE) {
>  		ptep = huge_pte_offset(mm, address);
> @@ -775,6 +776,7 @@ void __unmap_hugepage_range(struct vm_ar
>  	}
>  	spin_unlock(&mm->page_table_lock);
>  	flush_tlb_range(vma, start, end);
> +	mmu_notifier(invalidate_range_end, mm, start, end);
>  	list_for_each_entry_safe(page, tmp, &page_list, lru) {
>  		list_del(&page->lru);
>  		put_page(page);
> diff --git a/mm/memory.c b/mm/memory.c
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -611,6 +611,9 @@ int copy_page_range(struct mm_struct *ds
>  	if (is_vm_hugetlb_page(vma))
>  		return copy_hugetlb_page_range(dst_mm, src_mm, vma);
>  
> +	if (is_cow_mapping(vma->vm_flags))
> +		mmu_notifier(invalidate_range_begin, src_mm, addr, end);
> +
>  	dst_pgd = pgd_offset(dst_mm, addr);
>  	src_pgd = pgd_offset(src_mm, addr);
>  	do {
> @@ -621,6 +624,11 @@ int copy_page_range(struct mm_struct *ds
>  						vma, addr, next))
>  			return -ENOMEM;
>  	} while (dst_pgd++, src_pgd++, addr = next, addr != end);
> +
> +	if (is_cow_mapping(vma->vm_flags))
> +		mmu_notifier(invalidate_range_end, src_mm,
> +						vma->vm_start, end);
> +
>  	return 0;
>  }
>  
> @@ -897,7 +905,9 @@ unsigned long zap_page_range(struct vm_a
>  	lru_add_drain();
>  	tlb = tlb_gather_mmu(mm, 0);
>  	update_hiwater_rss(mm);
> +	mmu_notifier(invalidate_range_begin, mm, address, end);
>  	end = unmap_vmas(&tlb, vma, address, end, &nr_accounted, details);
> +	mmu_notifier(invalidate_range_end, mm, address, end);
>  	if (tlb)
>  		tlb_finish_mmu(tlb, address, end);
>  	return end;
> @@ -1463,10 +1473,11 @@ int apply_to_page_range(struct mm_struct
>  {
>  	pgd_t *pgd;
>  	unsigned long next;
> -	unsigned long end = addr + size;
> +	unsigned long start = addr, end = addr + size;
>  	int err;
>  
>  	BUG_ON(addr >= end);
> +	mmu_notifier(invalidate_range_begin, mm, start, end);
>  	pgd = pgd_offset(mm, addr);
>  	do {
>  		next = pgd_addr_end(addr, end);
> @@ -1474,6 +1485,7 @@ int apply_to_page_range(struct mm_struct
>  		if (err)
>  			break;
>  	} while (pgd++, addr = next, addr != end);
> +	mmu_notifier(invalidate_range_end, mm, start, end);
>  	return err;
>  }
>  EXPORT_SYMBOL_GPL(apply_to_page_range);
> @@ -1675,7 +1687,7 @@ gotten:
>  		 * seen in the presence of one thread doing SMC and another
>  		 * thread doing COW.
>  		 */
> -		ptep_clear_flush(vma, address, page_table);
> +		ptep_clear_flush_notify(vma, address, page_table);
>  		set_pte_at(mm, address, page_table, entry);
>  		update_mmu_cache(vma, address, entry);
>  		lru_cache_add_active(new_page);
> diff --git a/mm/mmap.c b/mm/mmap.c
> --- a/mm/mmap.c
> +++ b/mm/mmap.c
> @@ -1747,11 +1747,13 @@ static void unmap_region(struct mm_struc
>  	lru_add_drain();
>  	tlb = tlb_gather_mmu(mm, 0);
>  	update_hiwater_rss(mm);
> +	mmu_notifier(invalidate_range_begin, mm, start, end);
>  	unmap_vmas(&tlb, vma, start, end, &nr_accounted, NULL);
>  	vm_unacct_memory(nr_accounted);
>  	free_pgtables(&tlb, vma, prev? prev->vm_end: FIRST_USER_ADDRESS,
>  				 next? next->vm_start: 0);
>  	tlb_finish_mmu(tlb, start, end);
> +	mmu_notifier(invalidate_range_end, mm, start, end);
>  }
>  
>  /*
> @@ -2048,6 +2050,7 @@ void exit_mmap(struct mm_struct *mm)
>  	vm_unacct_memory(nr_accounted);
>  	free_pgtables(&tlb, vma, FIRST_USER_ADDRESS, 0);
>  	tlb_finish_mmu(tlb, 0, end);
> +	mmu_notifier_release(mm);
>  
>  	/*
>  	 * Walk the list again, actually closing and freeing it,
> diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c
> new file mode 100644
> --- /dev/null
> +++ b/mm/mmu_notifier.c
> @@ -0,0 +1,73 @@
> +/*
> + *  linux/mm/mmu_notifier.c
> + *
> + *  Copyright (C) 2008  Qumranet, Inc.
> + *  Copyright (C) 2008  SGI
> + *             Christoph Lameter <clameter@xxxxxxx>
> + *
> + *  This work is licensed under the terms of the GNU GPL, version 2. See
> + *  the COPYING file in the top-level directory.
> + */
> +
> +#include <linux/mmu_notifier.h>
> +#include <linux/module.h>
> +#include <linux/rcupdate.h>
> +
> +/*
> + * No synchronization. This function can only be called when only a single
> + * process remains that performs teardown.
> + */
> +void mmu_notifier_release(struct mm_struct *mm)
> +{
> +	struct mmu_notifier *mn;
> +	struct hlist_node *n, *tmp;
> +
> +	if (unlikely(!hlist_empty(&mm->mmu_notifier.head))) {
> +		hlist_for_each_entry_safe(mn, n, tmp,
> +					  &mm->mmu_notifier.head, hlist) {
> +			hlist_del(&mn->hlist);
> +			if (mn->ops->release)
> +				mn->ops->release(mn, mm);
> +		}
> +	}
> +}
> +
> +/*
> + * If no young bitflag is supported by the hardware, ->age_page can
> + * unmap the address and return 1 or 0 depending if the mapping previously
> + * existed or not.
> + */
> +int mmu_notifier_age_page(struct mm_struct *mm, unsigned long address)
> +{
> +	struct mmu_notifier *mn;
> +	struct hlist_node *n;
> +	int young = 0;
> +
> +	if (unlikely(!hlist_empty(&mm->mmu_notifier.head))) {
> +		rcu_read_lock();
> +		hlist_for_each_entry_rcu(mn, n,
> +					 &mm->mmu_notifier.head, hlist) {
> +			if (mn->ops->age_page)
> +				young |= mn->ops->age_page(mn, mm, address);
> +		}
> +		rcu_read_unlock();
> +	}
> +
> +	return young;
> +}
> +
> +void mmu_notifier_register(struct mmu_notifier *mn, struct mm_struct *mm)
> +{
> +	spin_lock(&mm->mmu_notifier.lock);
> +	hlist_add_head_rcu(&mn->hlist, &mm->mmu_notifier.head);
> +	spin_unlock(&mm->mmu_notifier.lock);
> +}
> +EXPORT_SYMBOL_GPL(mmu_notifier_register);
> +
> +void mmu_notifier_unregister(struct mmu_notifier *mn, struct mm_struct *mm)
> +{
> +	spin_lock(&mm->mmu_notifier.lock);
> +	hlist_del_rcu(&mn->hlist);
> +	spin_unlock(&mm->mmu_notifier.lock);
> +}
> +EXPORT_SYMBOL_GPL(mmu_notifier_unregister);
> diff --git a/mm/mprotect.c b/mm/mprotect.c
> --- a/mm/mprotect.c
> +++ b/mm/mprotect.c
> @@ -198,10 +198,12 @@ success:
>  		dirty_accountable = 1;
>  	}
>  
> +	mmu_notifier(invalidate_range_begin, mm, start, end);
>  	if (is_vm_hugetlb_page(vma))
>  		hugetlb_change_protection(vma, start, end, vma->vm_page_prot);
>  	else
>  		change_protection(vma, start, end, vma->vm_page_prot, dirty_accountable);
> +	mmu_notifier(invalidate_range_end, mm, start, end);
>  	vm_stat_account(mm, oldflags, vma->vm_file, -nrpages);
>  	vm_stat_account(mm, newflags, vma->vm_file, nrpages);
>  	return 0;
> diff --git a/mm/mremap.c b/mm/mremap.c
> --- a/mm/mremap.c
> +++ b/mm/mremap.c
> @@ -74,6 +74,7 @@ static void move_ptes(struct vm_area_str
>  	struct mm_struct *mm = vma->vm_mm;
>  	pte_t *old_pte, *new_pte, pte;
>  	spinlock_t *old_ptl, *new_ptl;
> +	unsigned long old_start;
>  
>  	if (vma->vm_file) {
>  		/*
> @@ -100,6 +101,9 @@ static void move_ptes(struct vm_area_str
>  		spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
>  	arch_enter_lazy_mmu_mode();
>  
> +	old_start = old_addr;
> +	mmu_notifier(invalidate_range_begin, vma->vm_mm,
> +		     old_start, old_end);
>  	for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE,
>  				   new_pte++, new_addr += PAGE_SIZE) {
>  		if (pte_none(*old_pte))
> @@ -108,6 +112,7 @@ static void move_ptes(struct vm_area_str
>  		pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr);
>  		set_pte_at(mm, new_addr, new_pte, pte);
>  	}
> +	mmu_notifier(invalidate_range_end, vma->vm_mm, old_start, old_end);
>  
>  	arch_leave_lazy_mmu_mode();
>  	if (new_ptl != old_ptl)
> diff --git a/mm/rmap.c b/mm/rmap.c
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -287,7 +287,7 @@ static int page_referenced_one(struct pa
>  	if (vma->vm_flags & VM_LOCKED) {
>  		referenced++;
>  		*mapcount = 1;	/* break early from loop */
> -	} else if (ptep_clear_flush_young(vma, address, pte))
> +	} else if (ptep_clear_flush_young_notify(vma, address, pte))
>  		referenced++;
>  
>  	/* Pretend the page is referenced if the task has the
> @@ -454,7 +454,7 @@ static int page_mkclean_one(struct page 
>  		pte_t entry;
>  
>  		flush_cache_page(vma, address, pte_pfn(*pte));
> -		entry = ptep_clear_flush(vma, address, pte);
> +		entry = ptep_clear_flush_notify(vma, address, pte);
>  		entry = pte_wrprotect(entry);
>  		entry = pte_mkclean(entry);
>  		set_pte_at(mm, address, pte, entry);
> @@ -712,14 +712,14 @@ static int try_to_unmap_one(struct page 
>  	 * skipped over this mm) then we should reactivate it.
>  	 */
>  	if (!migration && ((vma->vm_flags & VM_LOCKED) ||
> -			(ptep_clear_flush_young(vma, address, pte)))) {
> +			(ptep_clear_flush_young_notify(vma, address, pte)))) {
>  		ret = SWAP_FAIL;
>  		goto out_unmap;
>  	}
>  
>  	/* Nuke the page table entry. */
>  	flush_cache_page(vma, address, page_to_pfn(page));
> -	pteval = ptep_clear_flush(vma, address, pte);
> +	pteval = ptep_clear_flush_notify(vma, address, pte);
>  
>  	/* Move the dirty bit to the physical page now the pte is gone. */
>  	if (pte_dirty(pteval))
> @@ -844,12 +844,12 @@ static void try_to_unmap_cluster(unsigne
>  		page = vm_normal_page(vma, address, *pte);
>  		BUG_ON(!page || PageAnon(page));
>  
> -		if (ptep_clear_flush_young(vma, address, pte))
> +		if (ptep_clear_flush_young_notify(vma, address, pte))
>  			continue;
>  
>  		/* Nuke the page table entry. */
>  		flush_cache_page(vma, address, pte_pfn(*pte));
> -		pteval = ptep_clear_flush(vma, address, pte);
> +		pteval = ptep_clear_flush_notify(vma, address, pte);
>  
>  		/* If nonlinear, store the file page offset in the pte. */
>  		if (page->index != linear_page_index(vma, address))
> 

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