[PATCH 09/64] mm/mmu_notifier: teach oom reaper about range locking

[Davidlohr Bueso]

From: Davidlohr Bueso <dave@xxxxxxxxxxxx>

Also begin using mm_is_locked() wrappers (which is sometimes
the only reason why mm_has_blockable_invalidate_notifiers()
needs to be aware of the range passed back in oom_reap_task_mm().

Signed-off-by: Davidlohr Bueso <dbueso@xxxxxxx>
---
 include/linux/mmu_notifier.h | 6 ++++--
 mm/mmu_notifier.c            | 5 +++--
 mm/oom_kill.c                | 3 ++-
 3 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
index 2d07a1ed5a31..9172cb0bc15d 100644
--- a/include/linux/mmu_notifier.h
+++ b/include/linux/mmu_notifier.h
@@ -236,7 +236,8 @@ extern void __mmu_notifier_invalidate_range_end(struct mm_struct *mm,
 				  bool only_end);
 extern void __mmu_notifier_invalidate_range(struct mm_struct *mm,
 				  unsigned long start, unsigned long end);
-extern bool mm_has_blockable_invalidate_notifiers(struct mm_struct *mm);
+extern bool mm_has_blockable_invalidate_notifiers(struct mm_struct *mm,
+						  struct range_lock *mmrange);
 
 static inline void mmu_notifier_release(struct mm_struct *mm)
 {
@@ -476,7 +477,8 @@ static inline void mmu_notifier_invalidate_range(struct mm_struct *mm,
 {
 }
 
-static inline bool mm_has_blockable_invalidate_notifiers(struct mm_struct *mm)
+static inline bool mm_has_blockable_invalidate_notifiers(struct mm_struct *mm,
+							 struct range_lock *mmrange)
 {
 	return false;
 }
diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c
index eff6b88a993f..3e8a1a10607e 100644
--- a/mm/mmu_notifier.c
+++ b/mm/mmu_notifier.c
@@ -240,13 +240,14 @@ EXPORT_SYMBOL_GPL(__mmu_notifier_invalidate_range);
  * Must be called while holding mm->mmap_sem for either read or write.
  * The result is guaranteed to be valid until mm->mmap_sem is dropped.
  */
-bool mm_has_blockable_invalidate_notifiers(struct mm_struct *mm)
+bool mm_has_blockable_invalidate_notifiers(struct mm_struct *mm,
+					   struct range_lock *mmrange)
 {
 	struct mmu_notifier *mn;
 	int id;
 	bool ret = false;
 
-	WARN_ON_ONCE(!rwsem_is_locked(&mm->mmap_sem));
+	WARN_ON_ONCE(!mm_is_locked(mm, mmrange));
 
 	if (!mm_has_notifiers(mm))
 		return ret;
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 8219001708e0..2288e1cb1bc9 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -490,6 +490,7 @@ static bool __oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
 	struct mmu_gather tlb;
 	struct vm_area_struct *vma;
 	bool ret = true;
+	DEFINE_RANGE_LOCK_FULL(mmrange);
 
 	/*
 	 * We have to make sure to not race with the victim exit path
@@ -519,7 +520,7 @@ static bool __oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
 	 * TODO: we really want to get rid of this ugly hack and make sure that
 	 * notifiers cannot block for unbounded amount of time
 	 */
-	if (mm_has_blockable_invalidate_notifiers(mm)) {
+	if (mm_has_blockable_invalidate_notifiers(mm, &mmrange)) {
 		up_read(&mm->mmap_sem);
 		schedule_timeout_idle(HZ);
 		goto unlock_oom;
-- 
2.13.6