1 files changed, 27 insertions, 3 deletions

diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
index b25dc9db19fc..2d07a1ed5a31 100644
--- a/include/linux/mmu_notifier.h
+++ b/include/linux/mmu_notifier.h
@@ -2,6 +2,7 @@
 #ifndef _LINUX_MMU_NOTIFIER_H
 #define _LINUX_MMU_NOTIFIER_H
 
+#include <linux/types.h>
 #include <linux/list.h>
 #include <linux/spinlock.h>
 #include <linux/mm_types.h>
@@ -10,6 +11,9 @@
 struct mmu_notifier;
 struct mmu_notifier_ops;
 
+/* mmu_notifier_ops flags */
+#define MMU_INVALIDATE_DOES_NOT_BLOCK   (0x01)
+
 #ifdef CONFIG_MMU_NOTIFIER
 
 /*
@@ -27,6 +31,15 @@ struct mmu_notifier_mm {
 
 struct mmu_notifier_ops {
         /*
+         * Flags to specify behavior of callbacks for this MMU notifier.
+         * Used to determine which context an operation may be called.
+         *
+         * MMU_INVALIDATE_DOES_NOT_BLOCK: invalidate_range_* callbacks do not
+         *      block
+         */
+        int flags;
+
+        /*
          * Called either by mmu_notifier_unregister or when the mm is
          * being destroyed by exit_mmap, always before all pages are
          * freed. This can run concurrently with other mmu notifier
@@ -137,6 +150,10 @@ struct mmu_notifier_ops {
          * page. Pages will no longer be referenced by the linux
          * address space but may still be referenced by sptes until
          * the last refcount is dropped.
+         *
+         * If both of these callbacks cannot block, and invalidate_range
+         * cannot block, mmu_notifier_ops.flags should have
+         * MMU_INVALIDATE_DOES_NOT_BLOCK set.
          */
         void (*invalidate_range_start)(struct mmu_notifier *mn,
                                        struct mm_struct *mm,
@@ -159,12 +176,13 @@ struct mmu_notifier_ops {
          * external TLB range needs to be flushed. For more in depth
          * discussion on this see Documentation/vm/mmu_notifier.txt
          *
-         * The invalidate_range() function is called under the ptl
-         * spin-lock and not allowed to sleep.
-         *
          * Note that this function might be called with just a sub-range
          * of what was passed to invalidate_range_start()/end(), if
          * called between those functions.
+         *
+         * If this callback cannot block, and invalidate_range_{start,end}
+         * cannot block, mmu_notifier_ops.flags should have
+         * MMU_INVALIDATE_DOES_NOT_BLOCK set.
          */
         void (*invalidate_range)(struct mmu_notifier *mn, struct mm_struct *mm,
                                  unsigned long start, unsigned long end);
@@ -218,6 +236,7 @@ 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);
 
 static inline void mmu_notifier_release(struct mm_struct *mm)
 {
@@ -457,6 +476,11 @@ static inline void mmu_notifier_invalidate_range(struct mm_struct *mm,
 {
 }
 
+static inline bool mm_has_blockable_invalidate_notifiers(struct mm_struct *mm)
+{
+        return false;
+}
+
 static inline void mmu_notifier_mm_init(struct mm_struct *mm)
 {
 }