diff --git a/fs/Kconfig b/fs/Kconfig
index da3f32f..6ce72d8 100644
--- a/fs/Kconfig
+++ b/fs/Kconfig
@@ -46,6 +46,12 @@
 	  or if unsure, say N.  Saying Y will increase the size of the kernel
 	  by about 5kB.
 
+config FS_DAX_PMD
+	bool
+	default FS_DAX
+	depends on FS_DAX
+	depends on BROKEN
+
 endif # BLOCK
 
 # Posix ACL utility routines
diff --git a/fs/dax.c b/fs/dax.c
index d1e5cb7..43671b6 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -541,6 +541,10 @@
 	unsigned long pfn;
 	int result = 0;
 
+	/* dax pmd mappings are broken wrt gup and fork */
+	if (!IS_ENABLED(CONFIG_FS_DAX_PMD))
+		return VM_FAULT_FALLBACK;
+
 	/* Fall back to PTEs if we're going to COW */
 	if (write && !(vma->vm_flags & VM_SHARED))
 		return VM_FAULT_FALLBACK;