mm/mmu_notifier: kill invalidate_page

The invalidate_page callback suffered from two pitfalls.  First it used
to happen after the page table lock was release and thus a new page
might have setup before the call to invalidate_page() happened.

This is in a weird way fixed by commit c7ab0d2 ("mm: convert
try_to_unmap_one() to use page_vma_mapped_walk()") that moved the
callback under the page table lock but this also broke several existing
users of the mmu_notifier API that assumed they could sleep inside this
callback.

The second pitfall was invalidate_page() being the only callback not
taking a range of address in respect to invalidation but was giving an
address and a page.  Lots of the callback implementers assumed this
could never be THP and thus failed to invalidate the appropriate range
for THP.

By killing this callback we unify the mmu_notifier callback API to
always take a virtual address range as input.

Finally this also simplifies the end user life as there is now two clear
choices:
  - invalidate_range_start()/end() callback (which allow you to sleep)
  - invalidate_range() where you can not sleep but happen right after
    page table update under page table lock

Signed-off-by: Jérôme Glisse <[email protected]>
Cc: Bernhard Held <[email protected]>
Cc: Adam Borowski <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Radim Krčmář <[email protected]>
Cc: Wanpeng Li <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Takashi Iwai <[email protected]>
Cc: Nadav Amit <[email protected]>
Cc: Mike Galbraith <[email protected]>
Cc: Kirill A. Shutemov <[email protected]>
Cc: axie <[email protected]>
Cc: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

include/linux/mmu_notifier.h

@@ -94,17 +94,6 @@ struct mmu_notifier_ops {
 			   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
@@ -220,8 +209,6 @@ 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,
@@ -268,13 +255,6 @@ static inline void mmu_notifier_change_pte(struct mm_struct *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)
 {
@@ -442,11 +422,6 @@ static inline void mmu_notifier_change_pte(struct mm_struct *mm,
 {
 }
 
-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)
 {

mm/mmu_notifier.c

@@ -174,20 +174,6 @@ void __mmu_notifier_change_pte(struct mm_struct *mm, unsigned long address,
 	srcu_read_unlock(&srcu, id);
 }
 
-void __mmu_notifier_invalidate_page(struct mm_struct *mm,
-					  unsigned long address)
-{
-	struct mmu_notifier *mn;
-	int id;
-
-	id = srcu_read_lock(&srcu);
-	hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
-		if (mn->ops->invalidate_page)
-			mn->ops->invalidate_page(mn, mm, address);
-	}
-	srcu_read_unlock(&srcu, id);
-}
-
 void __mmu_notifier_invalidate_range_start(struct mm_struct *mm,
 				  unsigned long start, unsigned long end)
 {