Merge tag 'for-linus-4.16' of git://git.kernel.org/pub/scm/linux/kernel/git/hubcap...

[sfrench/cifs-2.6.git] / mm / mmu_notifier.c

diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c
index 96edb33fd09a79601ac0a54378ca4ff26df9112a..eff6b88a993f2491b8fb96a2ad553196448966da 100644 (file)
--- a/mm/mmu_notifier.c
+++ b/mm/mmu_notifier.c
@@ -236,6 +236,37 @@ void __mmu_notifier_invalidate_range(struct mm_struct *mm,
 }
 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)
+{
+       struct mmu_notifier *mn;
+       int id;
+       bool ret = false;
+
+       WARN_ON_ONCE(!rwsem_is_locked(&mm->mmap_sem));
+
+       if (!mm_has_notifiers(mm))
+               return ret;
+
+       id = srcu_read_lock(&srcu);
+       hlist_for_each_entry_rcu(mn, &mm->mmu_notifier_mm->list, hlist) {
+               if (!mn->ops->invalidate_range &&
+                   !mn->ops->invalidate_range_start &&
+                   !mn->ops->invalidate_range_end)
+                               continue;
+
+               if (!(mn->ops->flags & MMU_INVALIDATE_DOES_NOT_BLOCK)) {
+                       ret = true;
+                       break;
+               }
+       }
+       srcu_read_unlock(&srcu, id);
+       return ret;
+}
+
 static int do_mmu_notifier_register(struct mmu_notifier *mn,
                                    struct mm_struct *mm,
                                    int take_mmap_sem)