--- old/src/hotspot/os/linux/gc/z/zPhysicalMemoryBacking_linux.cpp	2020-02-17 13:00:57.460759300 +0900
+++ new/src/hotspot/os/linux/gc/z/zPhysicalMemoryBacking_linux.cpp	2020-02-17 13:00:57.149170000 +0900
@@ -138,14 +138,14 @@
   _available = buf.f_bavail * _block_size;
 
   // Make sure we're on a supported filesystem
-  if (!is_tmpfs() && !is_hugetlbfs()) {
+  if (!ZAllowHeapOnFileSystem && !is_tmpfs() && !is_hugetlbfs()) {
     log_error(gc)("Backing file must be located on a %s or a %s filesystem",
                   ZFILESYSTEM_TMPFS, ZFILESYSTEM_HUGETLBFS);
     return;
   }
 
   // Make sure the filesystem type matches requested large page type
-  if (ZLargePages::is_transparent() && !is_tmpfs()) {
+  if (!ZAllowHeapOnFileSystem && ZLargePages::is_transparent() && !is_tmpfs()) {
     log_error(gc)("-XX:+UseTransparentHugePages can only be enable when using a %s filesystem",
                   ZFILESYSTEM_TMPFS);
     return;
@@ -170,7 +170,13 @@
   }
 
   const size_t expected_block_size = is_tmpfs() ? os::vm_page_size() : os::large_page_size();
-  if (expected_block_size != _block_size) {
+  if (ZAllowHeapOnFileSystem) {
+    if (ZGranuleSize % _block_size != 0) {
+      log_error(gc)("Filesystem block size of %s should be multiple of " SIZE_FORMAT,
+                    AllocateHeapAt, _block_size);
+      return;
+    }
+  } else if (expected_block_size != _block_size) {
     log_error(gc)("%s filesystem has unexpected block size " SIZE_FORMAT " (expected " SIZE_FORMAT ")",
                   is_tmpfs() ? ZFILESYSTEM_TMPFS : ZFILESYSTEM_HUGETLBFS, _block_size, expected_block_size);
     return;
--- old/src/hotspot/share/gc/z/z_globals.hpp	2020-02-17 13:00:58.519850800 +0900
+++ new/src/hotspot/share/gc/z/z_globals.hpp	2020-02-17 13:00:58.228533300 +0900
@@ -58,6 +58,10 @@
           "Uncommit memory if it has been unused for the specified "        \
           "amount of time (in seconds)")                                    \
                                                                             \
+  experimental(bool, ZAllowHeapOnFileSystem, false,                         \
+          "Allow to use filesystem as Java heap backing storage "           \
+          "specified by -XX:AllocateHeapAt")                                \
+                                                                            \
   diagnostic(uint, ZStatisticsInterval, 10,                                 \
           "Time between statistics print outs (in seconds)")                \
           range(1, (uint)-1)                                                \