mm/mmu_notifier: mmu_notifier_range_update_to_read_only() helper

Helper to test if a range is updated to read only (it is still valid to
read from the range).  This is useful for device driver or anyone who wish
to optimize out update when they know that they already have the range map
read only.

Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Jérôme Glisse <[email protected]>
Reviewed-by: Ralph Campbell <[email protected]>
Reviewed-by: Ira Weiny <[email protected]>
Cc: Christian König <[email protected]>
Cc: Joonas Lahtinen <[email protected]>
Cc: Jani Nikula <[email protected]>
Cc: Rodrigo Vivi <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Peter Xu <[email protected]>
Cc: Felix Kuehling <[email protected]>
Cc: Jason Gunthorpe <[email protected]>
Cc: Ross Zwisler <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: Paolo Bonzini <[email protected]>
Cc: Radim Krcmar <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Christian Koenig <[email protected]>
Cc: John Hubbard <[email protected]>
Cc: Arnd Bergmann <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
index 0379956fff237ba6b47317566e734d29fe9a324e..b6c004bd9f6ad977ffdcb60ffc662a2916f94766 100644 (file)
--- a/include/linux/mmu_notifier.h
+++ b/include/linux/mmu_notifier.h
@@ -259,6 +259,8 @@ extern void __mmu_notifier_invalidate_range_end(struct mmu_notifier_range *r,
                                  bool only_end);
 extern void __mmu_notifier_invalidate_range(struct mm_struct *mm,
                                  unsigned long start, unsigned long end);
+extern bool
+mmu_notifier_range_update_to_read_only(const struct mmu_notifier_range *range);
 
 static inline bool
 mmu_notifier_range_blockable(const struct mmu_notifier_range *range)
@@ -568,6 +570,8 @@ static inline void mmu_notifier_mm_destroy(struct mm_struct *mm)
 {
 }
 
+#define mmu_notifier_range_update_to_read_only(r) false
+
 #define ptep_clear_flush_young_notify ptep_clear_flush_young
 #define pmdp_clear_flush_young_notify pmdp_clear_flush_young
 #define ptep_clear_young_notify ptep_test_and_clear_young

diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c
index abd88c466eb248a2a89ae875fae8db95b3873790..ee36068077b6e54b5c94287dafec00a18e88ff75 100644 (file)
--- a/mm/mmu_notifier.c
+++ b/mm/mmu_notifier.c
@@ -395,3 +395,13 @@ void mmu_notifier_unregister_no_release(struct mmu_notifier *mn,
        mmdrop(mm);
 }
 EXPORT_SYMBOL_GPL(mmu_notifier_unregister_no_release);
+
+bool
+mmu_notifier_range_update_to_read_only(const struct mmu_notifier_range *range)
+{
+       if (!range->vma || range->event != MMU_NOTIFY_PROTECTION_VMA)
+               return false;
+       /* Return true if the vma still have the read flag set. */
+       return range->vma->vm_flags & VM_READ;
+}
+EXPORT_SYMBOL_GPL(mmu_notifier_range_update_to_read_only);