+static pgoff_t dax_entry_start(pgoff_t index, void *entry)
+{
+	if (RADIX_DAX_TYPE(entry) == RADIX_DAX_PMD)
+		index &= (PMD_MASK >> PAGE_SHIFT);
+	return index;
+}
+
 static wait_queue_head_t *dax_entry_waitqueue(struct address_space *mapping,
-					      pgoff_t index)
+					      pgoff_t entry_start)
 {
-	unsigned long hash = hash_long((unsigned long)mapping ^ index,
+	unsigned long hash = hash_long((unsigned long)mapping ^ entry_start,
 				       DAX_WAIT_TABLE_BITS);
 	return wait_table + hash;
 }

All callers of dax_entry_waitqueue need to calculate entry_start
using this new dax_entry_start helper.  Either we should move the
call to dax_entry_start into this helper.  Or at least use local
variables for in the callers as both of them also fill out a
wait_exceptional_entry_queue structure with it.  Or do both by
letting dax_entry_waitqueue fill out that structure as well.