Index: lib/Support/Unix/Path.inc
===================================================================
--- lib/Support/Unix/Path.inc
+++ lib/Support/Unix/Path.inc
@@ -421,8 +421,12 @@
 #if defined(HAVE_POSIX_FALLOCATE)
   // If we have posix_fallocate use it. Unlike ftruncate it always allocates
   // space, so we get an error if the disk is full.
-  if (int Err = ::posix_fallocate(FD, 0, Size))
-    return std::error_code(Err, std::generic_category());
+  if (int Err = ::posix_fallocate(FD, 0, Size)) {
+    if (Err != EOPNOTSUPP)
+      return std::error_code(Err, std::generic_category());
+  }
+  if (::ftruncate(FD, Size) == -1)
+    return std::error_code(errno, std::generic_category());
 #else
   // Use ftruncate as a fallback. It may or may not allocate space. At least on
   // OS X with HFS+ it does.