1 files changed, 21 insertions, 0 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 77e64e3eac80..64a71bf20536 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1300,6 +1300,27 @@ static inline bool page_maybe_dma_pinned(struct page *page)
 		GUP_PIN_COUNTING_BIAS;
 }
 
+static inline bool is_cow_mapping(vm_flags_t flags)
+{
+	return (flags & (VM_SHARED | VM_MAYWRITE)) == VM_MAYWRITE;
+}
+
+/*
+ * This should most likely only be called during fork() to see whether we
+ * should break the cow immediately for a page on the src mm.
+ */
+static inline bool page_needs_cow_for_dma(struct vm_area_struct *vma,
+					  struct page *page)
+{
+	if (!is_cow_mapping(vma->vm_flags))
+		return false;
+
+	if (!atomic_read(&vma->vm_mm->has_pinned))
+		return false;
+
+	return page_maybe_dma_pinned(page);
+}
+
 #if defined(CONFIG_SPARSEMEM) && !defined(CONFIG_SPARSEMEM_VMEMMAP)
 #define SECTION_IN_PAGE_FLAGS
 #endif