Brings file locking changes from develop

38 files changed, 1348 insertions, 198 deletions

diff --git a/c++/src/H5FaccProp.cpp b/c++/src/H5FaccProp.cpp
index 1657351..6128d65 100644
--- a/c++/src/H5FaccProp.cpp
+++ b/c++/src/H5FaccProp.cpp
@@ -685,6 +685,53 @@ unsigned FileAccPropList::getGcReferences() const
 }
 
 //--------------------------------------------------------------------------
+// Function:    FileAccPropList::setFileLocking
+///\brief       Sets file locking flags.
+///\param       use_file_locking - IN: Flag that determines if file locks should
+//                  be used or not.
+///\param       ignore_when_disabled - IN: Flag that determines if file locks
+//                  should be be used when disabled on the file system or not.
+///\exception   H5::PropListIException
+///\par Description
+///             For information, please refer to the H5Pset_file_locking API in
+///             the HDF5 C Reference Manual.
+// Programmer   Dana Robinson - 2020
+//--------------------------------------------------------------------------
+void FileAccPropList::setFileLocking(hbool_t use_file_locking, hbool_t ignore_when_disabled) const
+{
+    herr_t ret_value = H5Pset_file_locking(id, use_file_locking, ignore_when_disabled);
+
+    if (ret_value < 0)
+    {
+        throw PropListIException("FileAccPropList::setFileLocking", "H5Pset_file_locking failed");
+    }
+}
+
+//--------------------------------------------------------------------------
+// Function:    FileAccPropList::getFileLocking
+///\brief       Gets file locking flags.
+///\param       use_file_locking - OUT: Flag that determines if file locks
+//                  should be used or not.
+///\param       ignore_when_disabled - OUT: Flag that determines if file locks
+//                  should be be used when disabled on the file system or not.
+///\exception   H5::PropListIException
+///\par Description
+///             For information, please refer to the H5Pget_file_locking API in
+///             the HDF5 C Reference Manual.
+// Programmer   Dana Robinson - 2020
+//--------------------------------------------------------------------------
+void FileAccPropList::getFileLocking(hbool_t& use_file_locking, hbool_t& ignore_when_disabled) const
+{
+    herr_t ret_value = H5Pget_file_locking(id, &use_file_locking, &ignore_when_disabled);
+
+    if (ret_value < 0)
+    {
+        throw PropListIException("FileAccPropList::getFileLocking", "H5Pget_file_locking failed");
+    }
+}
+
+
+//--------------------------------------------------------------------------
 // Function:    FileAccPropList::setLibverBounds
 ///\brief       Sets bounds on versions of library format to be used when creating
 ///             or writing objects.
diff --git a/c++/src/H5FaccProp.h b/c++/src/H5FaccProp.h
index 58f049e..ee90fa4 100644
--- a/c++/src/H5FaccProp.h
+++ b/c++/src/H5FaccProp.h
@@ -126,6 +126,12 @@ class H5_DLLCPP FileAccPropList : public PropList {
         // Returns garbage collecting references setting.
         unsigned getGcReferences() const;
 
+        // Sets file locking parameters.
+        void setFileLocking(hbool_t use_file_locking, hbool_t ignore_when_disabled) const;
+
+        // Gets file locking parameters.
+        void getFileLocking(hbool_t& use_file_locking, hbool_t& ignore_when_disabled) const;
+
         // Sets bounds on versions of library format to be used when creating
         // or writing objects.
         void setLibverBounds(H5F_libver_t libver_low, H5F_libver_t libver_high) const;
diff --git a/config/cmake/ConfigureChecks.cmake b/config/cmake/ConfigureChecks.cmake
index 11bf39c..4188e45 100644
--- a/config/cmake/ConfigureChecks.cmake
+++ b/config/cmake/ConfigureChecks.cmake
@@ -61,6 +61,31 @@ if (HDF5_ENABLE_CODESTACK)
 endif ()
 MARK_AS_ADVANCED (HDF5_ENABLE_CODESTACK)
 
+# ----------------------------------------------------------------------
+# Check if they would like to use file locking by default
+#-----------------------------------------------------------------------------
+option (HDF5_USE_FILE_LOCKING "Use file locking by default (mainly for SWMR)" ON)
+if (HDF5_USE_FILE_LOCKING)
+  set (${HDF_PREFIX}_USE_FILE_LOCKING 1)
+endif ()
+
+# ----------------------------------------------------------------------
+# Check if they would like to ignore file locks when disabled on a file system
+#-----------------------------------------------------------------------------
+option (HDF5_IGNORE_DISABLED_FILE_LOCKS "Ignore file locks when disabled on file system" ON)
+if (HDF5_IGNORE_DISABLED_FILE_LOCKS)
+  set (${HDF_PREFIX}_IGNORE_DISABLED_FILE_LOCKS 1)
+endif ()
+
+# Set the libhdf5.settings file variable
+if (HDF5_IGNORE_DISABLED_FILE_LOCKS AND HDF5_USE_FILE_LOCKING)
+  set (HDF5_FILE_LOCKING_SETTING "best-effort")
+elseif (HDF5_IGNORE_DISABLED_FILE_LOCKS)
+  set (HDF5_FILE_LOCKING_SETTING "yes")
+else ()
+  set (HDF5_FILE_LOCKING_SETTING "no")
+endif ()
+
 #-----------------------------------------------------------------------------
 #  Are we going to use HSIZE_T
 #-----------------------------------------------------------------------------
diff --git a/config/cmake/H5pubconf.h.in b/config/cmake/H5pubconf.h.in
index 6cbfd29..05903d4 100644
--- a/config/cmake/H5pubconf.h.in
+++ b/config/cmake/H5pubconf.h.in
@@ -480,6 +480,9 @@
 /* Define if the compiler understands __inline__ */
 #cmakedefine H5_HAVE___INLINE__ @H5_HAVE___INLINE__@
 
+/* Define if the library will ignore file locks when disabled */                 
+#cmakedefine H5_IGNORE_DISABLED_FILE_LOCKS @H5_IGNORE_DISABLED_FILE_LOCKS@
+
 /* Define if the high-level library headers should be included in hdf5.h */
 #cmakedefine H5_INCLUDE_HL @H5_INCLUDE_HL@
 
@@ -714,6 +717,9 @@
 /* Define using v1.10 public API symbols by default */
 #cmakedefine H5_USE_110_API_DEFAULT @H5_USE_110_API_DEFAULT@
 
+/* Define if the library will use file locking */
+#cmakedefine H5_FILE_LOCKING @H5_USE_FILE_LOCKING@
+
 /* Define if a memory checking tool will be used on the library, to cause
    library to be very picky about memory operations and also disable the
    internal free list manager code. */
diff --git a/config/cmake/libhdf5.settings.cmake.in b/config/cmake/libhdf5.settings.cmake.in
index e9a8395..7dd72b4 100644
--- a/config/cmake/libhdf5.settings.cmake.in
+++ b/config/cmake/libhdf5.settings.cmake.in
@@ -84,5 +84,6 @@ Parallel Filtered Dataset Writes: @PARALLEL_FILTERED_WRITES@
             Using memory checker: @HDF5_ENABLE_USING_MEMCHECKER@
  Memory allocation sanity checks: @HDF5_MEMORY_ALLOC_SANITY_CHECK@
           Function Stack Tracing: @HDF5_ENABLE_CODESTACK@
+                Use file locking: @HDF5_FILE_LOCKING_SETTING@
        Strict File Format Checks: @HDF5_STRICT_FORMAT_CHECKS@
     Optimization Instrumentation: @HDF5_Enable_Instrument@
diff --git a/configure.ac b/configure.ac
index db0d1f0..5e5db4a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2315,6 +2315,56 @@ case "X-$OPTIMIZATION" in
 esac
 
 ## ----------------------------------------------------------------------
+## Check if file locking should be used
+##
+AC_MSG_CHECKING([enable file locking])
+AC_ARG_ENABLE([file-locking],
+              [AS_HELP_STRING([--enable-file-locking=(yes|no|best-effort)],
+                              [Sets the default for whether or not to use file
+                               locking when opening files. Can be overridden
+                               with the HDF5_USE_FILE_LOCKING environment variable
+                               and the H5Pset_file_locking() API call.
+                               best-effort attempts to use file locking but does
+                               not fail when file locks have been disabled on
+                               the file system (useful with Lustre).
+                               [default=best-effort]
+                               ])],
+              [DESIRED_FILE_LOCKING=$enableval])
+
+## Set defaults
+if test "X-$DESIRED_FILE_LOCKING" = X- ; then
+  DESIRED_FILE_LOCKING=best-effort
+fi
+
+## Allow this variable to be substituted in
+## other files (src/libhdf5.settings.in, etc.)
+AC_SUBST([DESIRED_FILE_LOCKING])
+AC_SUBST([USE_FILE_LOCKING])
+AC_SUBST([IGNORE_DISABLED_FILE_LOCKS])
+
+case "X-$DESIRED_FILE_LOCKING" in
+  X-best-effort)
+      AC_MSG_RESULT([best-effort])
+      AC_DEFINE([USE_FILE_LOCKING], [1],
+                [Define if the library will use file locking])
+      AC_DEFINE([IGNORE_DISABLED_FILE_LOCKS], [1],
+                [Define if the library will ignore file locks when disabled])
+    ;;
+  X-yes)
+      AC_MSG_RESULT([yes])
+      AC_DEFINE([USE_FILE_LOCKING], [1],
+                [Define if the library will use file locking])
+    ;;
+  X-no)
+      AC_MSG_RESULT([no])
+    ;;
+  *)
+      AC_MSG_ERROR([Unrecognized value: $USE_FILE_LOCKING])
+    ;;
+esac
+
+
+## ----------------------------------------------------------------------
 ## Enable/disable internal package-level debugging output
 ##
 AC_MSG_CHECKING([for internal debug output])
diff --git a/fortran/src/H5Pff.F90 b/fortran/src/H5Pff.F90
index aa9861d..c6f053f 100644
--- a/fortran/src/H5Pff.F90
+++ b/fortran/src/H5Pff.F90
@@ -8115,5 +8115,107 @@ END SUBROUTINE h5pget_virtual_dsetname_f
 
   END SUBROUTINE h5pset_dset_no_attrs_hint_f
 
+!****s* H5P (F03)/h5pget_file_locking_f_F03
+!
+! NAME
+!  h5pget_file_locking_f
+!
+! PURPOSE
+!  Gets the file locking properties. File locking is mainly used to help
+!  enforce SWMR semantics.
+!
+! INPUTS
+!  fapl_id    - Target file access property list identifier.
+!
+! OUTPUTS
+!  use_file_locking - Whether or not to use file locks.
+!  ignore_disabled_locks - Whether or not to ignore file locks when locking
+!                          is disabled on a file system.
+!  hdferr     - error code:
+!                 0 on success and -1 on failure
+!
+! AUTHOR
+!  Dana Robinson
+!  Summer 2020
+!
+! Fortran2003 Interface:
+  SUBROUTINE h5pget_file_locking_f(fapl_id, use_file_locking, ignore_disabled_locks, hdferr)
+    IMPLICIT NONE
+    INTEGER(HID_T) , INTENT(IN)              :: fapl_id
+    LOGICAL        , INTENT(OUT)             :: use_file_locking
+    LOGICAL        , INTENT(OUT)             :: ignore_disabled_locks
+    INTEGER        , INTENT(OUT)             :: hdferr
+!*****
+    LOGICAL(C_BOOL) :: c_use_flag
+    LOGICAL(C_BOOL) :: c_ignore_flag
+
+    INTERFACE
+       INTEGER FUNCTION h5pget_file_locking(fapl_id, use_file_locking, ignore_disabled_locks) BIND(C, NAME='H5Pget_file_locking')
+         IMPORT :: HID_T, C_BOOL
+         IMPLICIT NONE
+         INTEGER(HID_T), INTENT(IN), VALUE :: fapl_id
+         LOGICAL(C_BOOL), INTENT(OUT) :: use_file_locking
+         LOGICAL(C_BOOL), INTENT(OUT) :: ignore_disabled_locks
+       END FUNCTION h5pget_file_locking
+    END INTERFACE
+
+    hdferr = INT(h5pget_file_locking(fapl_id, c_use_flag, c_ignore_flag))
+
+    ! Transfer value of C C_BOOL type to Fortran LOGICAL
+    use_file_locking = c_use_flag
+    ignore_disabled_locks = c_ignore_flag
+
+   END SUBROUTINE h5pget_file_locking_f
+
+!****s* H5P (F03)/h5pset_file_locking_f_F03
+!
+! NAME
+!  h5pset_file_locking_f
+!
+! PURPOSE
+!  Sets the file locking properties. File locking is mainly used to help
+!  enforce SWMR semantics.
+!
+! INPUTS
+!  fapl_id    - Target file access property list identifier.
+!  use_file_locking - Whether or not to use file locks.
+!  ignore_disabled_locks - Whether or not to ignore file locks when locking
+!                          is disabled on a file system.
+!  hdferr     - error code:
+!                 0 on success and -1 on failure
+!
+! AUTHOR
+!  Dana Robinson
+!  Summer 2020
+!
+! Fortran2003 Interface:
+  SUBROUTINE h5pset_file_locking_f(fapl_id, use_file_locking, ignore_disabled_locks, hdferr)
+    IMPLICIT NONE
+    INTEGER(HID_T) , INTENT(IN)              :: fapl_id
+    LOGICAL        , INTENT(IN)              :: use_file_locking
+    LOGICAL        , INTENT(IN)              :: ignore_disabled_locks
+    INTEGER        , INTENT(OUT)             :: hdferr
+!*****
+    LOGICAL(C_BOOL) :: c_use_flag
+    LOGICAL(C_BOOL) :: c_ignore_flag
+
+    INTERFACE
+       INTEGER FUNCTION h5pset_file_locking(fapl_id, use_file_locking, ignore_disabled_locks) BIND(C, NAME='H5Pset_file_locking')
+         IMPORT :: HID_T, C_BOOL
+         IMPLICIT NONE
+         INTEGER(HID_T), INTENT(IN), VALUE :: fapl_id
+         LOGICAL(C_BOOL), INTENT(IN), VALUE :: use_file_locking
+         LOGICAL(C_BOOL), INTENT(IN), VALUE :: ignore_disabled_locks
+       END FUNCTION h5pset_file_locking
+    END INTERFACE
+
+    ! Transfer value of Fortran LOGICAL to C C_BOOL type
+    c_use_flag = use_file_locking
+    c_ignore_flag = ignore_disabled_locks
+
+    hdferr = INT(h5pset_file_locking(fapl_id, c_use_flag, c_ignore_flag))
+
+  END SUBROUTINE h5pset_file_locking_f
+
 END MODULE H5P
 
diff --git a/fortran/src/hdf5_fortrandll.def.in b/fortran/src/hdf5_fortrandll.def.in
index b9e2314..8438f2a 100644
--- a/fortran/src/hdf5_fortrandll.def.in
+++ b/fortran/src/hdf5_fortrandll.def.in
@@ -333,6 +333,8 @@ H5P_mp_H5PGET_VIRTUAL_FILENAME_F
 H5P_mp_H5PGET_VIRTUAL_DSETNAME_F
 H5P_mp_H5PGET_DSET_NO_ATTRS_HINT_F
 H5P_mp_H5PSET_DSET_NO_ATTRS_HINT_F
+H5P_mp_H5PSET_FILE_LOCKING_F
+H5P_mp_H5PGET_FILE_LOCKING_F
 ; Parallel
 @H5_NOPAREXP@H5P_mp_H5PSET_FAPL_MPIO_F
 @H5_NOPAREXP@H5P_mp_H5PGET_FAPL_MPIO_F
diff --git a/fortran/test/fortranlib_test.F90 b/fortran/test/fortranlib_test.F90
index 92f9279..214f3c2 100644
--- a/fortran/test/fortranlib_test.F90
+++ b/fortran/test/fortranlib_test.F90
@@ -186,6 +186,10 @@ PROGRAM fortranlibtest
   CALL test_chunk_cache (cleanup, ret_total_error)
   CALL write_test_status(ret_total_error, ' Dataset chunk cache configuration', total_error)
 
+  ret_total_error = 0
+  CALL test_misc_properties(cleanup, ret_total_error)
+  CALL write_test_status(ret_total_error, ' Miscellaneous properties', total_error)
+
 !
 !      '========================================='
 !      'Testing ATTRIBUTE interface              '
diff --git a/fortran/test/tH5P.F90 b/fortran/test/tH5P.F90
index 7fe3971..19bee75 100644
--- a/fortran/test/tH5P.F90
+++ b/fortran/test/tH5P.F90
@@ -724,4 +724,77 @@ SUBROUTINE test_chunk_cache(cleanup, total_error)
 
 END SUBROUTINE test_chunk_cache
 
+!-------------------------------------------------------------------------
+! Function: test_misc_properties
+!
+! Purpose:  Tests setting and getting of miscellaneous properties. Does
+!           not test the underlying functionality as that is done in
+!           the C library tests.
+!
+!           Tests APIs:
+!               H5P_GET/SET_FILE_LOCKING_F
+!
+! Return:   Success:    0
+!           Failure:    -1
+!
+!-------------------------------------------------------------------------
+!
+SUBROUTINE test_misc_properties(cleanup, total_error)
+
+  IMPLICIT NONE
+  LOGICAL, INTENT(IN)  :: cleanup
+  INTEGER, INTENT(INOUT) :: total_error
+
+  INTEGER(hid_t) :: fapl_id = -1 !  Local fapl
+  LOGICAL :: use_file_locking           ! (H5Pset/get_file_locking_f)
+  LOGICAL :: ignore_disabled_locks      ! (H5Pset/get_file_locking_f)
+  INTEGER :: error
+
+  ! Create a default fapl
+  CALL H5Pcreate_f(H5P_FILE_ACCESS_F, fapl_id, error)
+  CALL check("H5Pcreate_f", error, total_error)
+
+  ! Test H5Pset/get_file_locking_f
+  ! true values
+  use_file_locking = .TRUE.
+  ignore_disabled_locks = .TRUE.
+  CALL h5pset_file_locking_f(fapl_id, use_file_locking, ignore_disabled_locks, error)
+  CALL check("h5pset_set_file_locking_f", error, total_error)
+  use_file_locking = .FALSE.
+  ignore_disabled_locks = .FALSE.
+  CALL h5pget_file_locking_f(fapl_id, use_file_locking, ignore_disabled_locks, error)
+  CALL check("h5pget_set_file_locking_f", error, total_error)
+  if(use_file_locking .neqv. .TRUE.) then
+    total_error = total_error + 1
+    write(*,*) "Got wrong use_file_locking flag from h5pget_file_locking_f"
+  endif
+  if(ignore_disabled_locks .neqv. .TRUE.) then
+    total_error = total_error + 1
+    write(*,*) "Got wrong ignore_disabled_locks flag from h5pget_file_locking_f"
+  endif
+
+  ! false values
+  use_file_locking = .FALSE.
+  ignore_disabled_locks = .FALSE.
+  CALL h5pset_file_locking_f(fapl_id, use_file_locking, ignore_disabled_locks, error)
+  CALL check("h5pset_set_file_locking_f", error, total_error)
+  use_file_locking = .TRUE.
+  ignore_disabled_locks = .TRUE.
+  CALL h5pget_file_locking_f(fapl_id, use_file_locking, ignore_disabled_locks, error)
+  CALL check("h5pget_set_file_locking_f", error, total_error)
+  if(use_file_locking .neqv. .FALSE.) then
+    total_error = total_error + 1
+    write(*,*) "Got wrong use_file_locking flag from h5pget_file_locking_f"
+  endif
+  if(ignore_disabled_locks .neqv. .FALSE.) then
+    total_error = total_error + 1
+    write(*,*) "Got wrong ignore_disabled_locks flag from h5pget_file_locking_f"
+  endif
+
+  ! Close the fapl
+  CALL H5Pclose_f(fapl_id, error)
+  CALL check("H5Pclose_f", error, total_error)
+
+END SUBROUTINE test_misc_properties
+
 END MODULE TH5P
diff --git a/java/src/hdf/hdf5lib/H5.java b/java/src/hdf/hdf5lib/H5.java
index 7681c48..4c9713b 100644
--- a/java/src/hdf/hdf5lib/H5.java
+++ b/java/src/hdf/hdf5lib/H5.java
@@ -6462,6 +6462,51 @@ public class H5 implements java.io.Serializable {
     public synchronized static native void H5Pset_evict_on_close(long fapl_id, boolean evict_on_close)
             throws HDF5LibraryException;
 
+    /**
+     * H5Pget_use_file_locking retrieves whether we are using file locking.
+     *
+     * @param fapl_id
+     *            IN: File access property list identifier
+     *
+     * @exception HDF5LibraryException
+     *                - Error from the HDF-5 Library.
+     *
+     **/
+    public synchronized static native boolean H5Pget_use_file_locking(long fapl_id)
+            throws HDF5LibraryException;
+
+    /**
+     * H5Pget_use_file_locking retrieves whether we ignore file locks when they are disabled.
+     *
+     * @param fapl_id
+     *            IN: File access property list identifier
+     *
+     * @exception HDF5LibraryException
+     *                - Error from the HDF-5 Library.
+     *
+     **/
+    public synchronized static native boolean H5Pget_ignore_disabled_file_locking(long fapl_id)
+            throws HDF5LibraryException;
+
+    /**
+     * H5Pset_file_locking sets parameters related to file locking.
+     *
+     * @param fapl_id
+     *            IN: File access property list identifier
+     *
+     * @param use_file_locking
+     *            IN: Whether the library will use file locking when opening files (mainly for SWMR semantics).
+     *
+     * @param ignore_when_disabled
+     *            IN: Whether file locking will be ignored when disabled on a file system (useful for Lustre).
+     *
+     * @exception HDF5LibraryException
+     *                - Error from the HDF-5 Library.
+     *
+     **/
+    public synchronized static native void H5Pset_file_locking(long fapl_id, boolean use_file_locking, boolean ignore_when_disabled)
+            throws HDF5LibraryException;
+
     // Dataset creation property list (DCPL) routines //
 
     /**
diff --git a/java/src/jni/h5pFAPLImp.c b/java/src/jni/h5pFAPLImp.c
index 9ae8775..dbfbb5a 100644
--- a/java/src/jni/h5pFAPLImp.c
+++ b/java/src/jni/h5pFAPLImp.c
@@ -1377,6 +1377,78 @@ done:
 
 /*
  * Class:     hdf_hdf5lib_H5
+ * Method:    H5Pset_file_locking
+ * Signature: (JZZ)V
+ */
+JNIEXPORT void JNICALL
+Java_hdf_hdf5lib_H5_H5Pset_1file_1locking
+    (JNIEnv *env, jclass clss, jlong fapl_id, jboolean use_file_locking, jboolean ignore_when_disabled)
+{
+    hbool_t use_file_locking_val = TRUE;
+    hbool_t ignore_when_disabled_val = TRUE;
+
+    UNUSED(clss);
+
+    use_file_locking_val = (use_file_locking == JNI_TRUE) ? TRUE : FALSE;
+    ignore_when_disabled_val = (ignore_when_disabled == JNI_TRUE) ? TRUE : FALSE;
+
+    if (H5Pset_file_locking((hid_t)fapl_id, use_file_locking_val, ignore_when_disabled_val) < 0)
+        H5_LIBRARY_ERROR(ENVONLY);
+
+done:
+    return;
+} /* end Java_hdf_hdf5lib_H5_H5Pset_1file_1locking */
+
+/*
+ * Class:     hdf_hdf5lib_H5
+ * Method:    H5Pget_use_file_locking
+ * Signature: (J)Z
+ */
+JNIEXPORT jboolean JNICALL
+Java_hdf_hdf5lib_H5_H5Pget_1use_1file_1locking
+    (JNIEnv *env, jclass clss, jlong fapl_id)
+{
+    hbool_t     use_file_locking_val    = TRUE;
+    hbool_t     unused                  = TRUE;
+    jboolean    bval                    = JNI_FALSE;
+
+    UNUSED(clss);
+
+    if (H5Pget_file_locking((hid_t)fapl_id, &use_file_locking_val, &unused) < 0)
+        H5_LIBRARY_ERROR(ENVONLY);
+
+    bval = (use_file_locking_val == TRUE) ? JNI_TRUE : JNI_FALSE;
+
+done:
+    return bval;
+} /* end Java_hdf_hdf5lib_H5_H5Pget_1use_1file_1locking */
+
+/*
+ * Class:     hdf_hdf5lib_H5
+ * Method:    H5Pget_ignore_disabled_file_locking
+ * Signature: (J)Z
+ */
+JNIEXPORT jboolean JNICALL
+Java_hdf_hdf5lib_H5_H5Pget_1ignore_1disabled_1file_1locking
+    (JNIEnv *env, jclass clss, jlong fapl_id)
+{
+    hbool_t     ignore_when_disabled_val    = TRUE;
+    hbool_t     unused                      = TRUE;
+    jboolean    bval                        = JNI_FALSE;
+
+    UNUSED(clss);
+
+    if (H5Pget_file_locking((hid_t)fapl_id, &unused, &ignore_when_disabled_val) < 0)
+        H5_LIBRARY_ERROR(ENVONLY);
+
+    bval = (ignore_when_disabled_val == TRUE) ? JNI_TRUE : JNI_FALSE;
+
+done:
+    return bval;
+} /* end Java_hdf_hdf5lib_H5_H5Pget_1ignore_1disabled_1file_1locking */
+
+/*
+ * Class:     hdf_hdf5lib_H5
  * Method:    H5Pset_metadata_read_attempts
  * Signature: (JJ)V
  */
diff --git a/java/src/jni/h5pFAPLImp.h b/java/src/jni/h5pFAPLImp.h
index 9b353e6..b9b4556 100644
--- a/java/src/jni/h5pFAPLImp.h
+++ b/java/src/jni/h5pFAPLImp.h
@@ -392,6 +392,33 @@ Java_hdf_hdf5lib_H5_H5Pget_1evict_1on_1close
 
 /*
  * Class:     hdf_hdf5lib_H5
+ * Method:    H5Pset_file_locking
+ * Signature: (JZZ)V
+ */
+JNIEXPORT void JNICALL
+Java_hdf_hdf5lib_H5_H5Pset_1file_1locking
+(JNIEnv *env, jclass clss, jlong fapl_id, jboolean use_file_locking, jboolean ignore_when_disabled);
+
+/*
+ * Class:     hdf_hdf5lib_H5
+ * Method:    H5Pget_use_file_locking
+ * Signature: (J)Z
+ */
+JNIEXPORT jboolean JNICALL
+Java_hdf_hdf5lib_H5_H5Pget_1use_1file_1locking
+(JNIEnv *env, jclass clss, jlong fapl_id);
+
+/*
+ * Class:     hdf_hdf5lib_H5
+ * Method:    H5Pget_ignore_disabled_file_locking
+ * Signature: (J)Z
+ */
+JNIEXPORT jboolean JNICALL
+Java_hdf_hdf5lib_H5_H5Pget_1ignore_1disabled_1file_1locking
+(JNIEnv *env, jclass clss, jlong fapl_id);
+
+/*
+ * Class:     hdf_hdf5lib_H5
  * Method:    H5Pset_metadata_read_attempts
  * Signature: (JJ)V
  */
diff --git a/java/test/TestH5Pfapl.java b/java/test/TestH5Pfapl.java
index 10a79dd..4233580 100644
--- a/java/test/TestH5Pfapl.java
+++ b/java/test/TestH5Pfapl.java
@@ -1398,4 +1398,36 @@ public class TestH5Pfapl {
             fail("H5P_evict_on_close: " + err);
         }
     }
+
+    @Test
+    public void testH5P_file_locking() {
+        boolean use_file_locking = false;
+        boolean ignore_disabled_file_locking = false;
+        try {
+            // false values (usually not the default)
+            H5.H5Pset_file_locking(fapl_id, false, false);
+            use_file_locking = H5.H5Pget_use_file_locking(fapl_id);
+            ignore_disabled_file_locking = H5.H5Pget_ignore_disabled_file_locking(fapl_id);
+            assertFalse("H5P_file_locking", use_file_locking);
+            assertFalse("H5P_file_locking", ignore_disabled_file_locking);
+
+            // true values (typically the default)
+            H5.H5Pset_file_locking(fapl_id, true, true);
+            use_file_locking = H5.H5Pget_use_file_locking(fapl_id);
+            ignore_disabled_file_locking = H5.H5Pget_ignore_disabled_file_locking(fapl_id);
+            assertTrue("H5P_file_locking", use_file_locking);
+            assertTrue("H5P_file_locking", ignore_disabled_file_locking);
+        }
+        catch (HDF5PropertyListInterfaceException err) {
+            // parallel is not supported
+            if (err.getMinorErrorNumber() != HDF5Constants.H5E_UNSUPPORTED) {
+                err.printStackTrace();
+                fail("H5P_test_file_locking: " + err);
+            }
+        }
+        catch (Throwable err) {
+            err.printStackTrace();
+            fail("H5P_test_file_locking: " + err);
+        }
+    }
 }
diff --git a/java/test/testfiles/JUnit-TestH5Pfapl.txt b/java/test/testfiles/JUnit-TestH5Pfapl.txt
index c4f37d0..c34ac1c 100644
--- a/java/test/testfiles/JUnit-TestH5Pfapl.txt
+++ b/java/test/testfiles/JUnit-TestH5Pfapl.txt
@@ -28,6 +28,7 @@ JUnit version 4.11
 .testH5Pset_elink_fapl
 .testH5P_hyper_vector_size
 .testH5P_gc_references
+.testH5P_file_locking
 .testH5P_family_offset
 .testH5P_fapl_core
 .testH5P_fapl_muti
@@ -37,5 +38,5 @@ JUnit version 4.11
 
 Time:  XXXX
 
-OK (35 tests)
+OK (36 tests)
 
diff --git a/release_docs/RELEASE.txt b/release_docs/RELEASE.txt
index 04501b1..53467d5 100644
--- a/release_docs/RELEASE.txt
+++ b/release_docs/RELEASE.txt
@@ -251,6 +251,55 @@ New Features
 
       (ADB - 2019/04/15, HDFFV-10741)
 
+    - Add file locking configure and CMake options
+
+      HDF5 1.10.0 introduced a file locking scheme, primarily to help
+      enforce SWMR setup. Formerly, the only user-level control of the scheme
+      was via the HDF5_USE_FILE_LOCKING environment variable.
+
+      This change introduces configure-time options that control whether
+      or not file locking will be used and whether or not the library
+      ignores errors when locking has been disabled on the file system
+      (useful on some HPC Lustre installations).
+
+      In both the Autotools and CMake, the settings have the effect of changing
+      the default property list settings (see the H5Pset/get_file_locking()
+      entry, below).
+
+      The yes/no/best-effort file locking configure setting has also been
+      added to the libhdf5.settings file.
+
+      Autotools:
+
+        An --enable-file-locking=(yes|no|best-effort) option has been added.
+
+        yes:          Use file locking.
+        no:           Do not use file locking.
+        best-effort:  Use file locking and ignore "disabled" errors.
+
+      CMake:
+
+        Two self-explanatory options have been added:
+
+        HDF5_USE_FILE_LOCKING
+        HDF5_IGNORE_DISABLED_FILE_LOCKS
+
+        Setting both of these to ON is the equivalent to the Autotools'
+        best-effort setting.
+
+      NOTE:
+      The precedence order of the various file locking control mechanisms is:
+
+        1) HDF5_USE_FILE_LOCKING environment variable (highest)
+
+        2) H5Pset_file_locking()
+
+        3) configure/CMake options (which set the property list defaults)
+
+        4) library defaults (currently best-effort)
+
+      (DER - 2020/07/30, HDFFV-11092)
+
 
     Library:
     --------
@@ -292,11 +341,49 @@ New Features
 
       (JTH - 2019/10/07)
 
+    - Add BEST_EFFORT value to HDF5_USE_FILE_LOCKING environment variable
+
+      This change adds a BEST_EFFORT to the TRUE/FALSE, 1/0 settings that
+      were previously accepted. This option turns on file locking but
+      ignores locking errors when the library detects that file locking
+      has been disabled on a file system (useful on some HPC Lustre
+      installations).
+
+      The capitalization of BEST_EFFORT is mandatory.
 
-     Parallel Library:
+      See the configure option discussion for HDFFV-11092 (above) for more
+      information on the file locking feature and how it's controlled.
+
+      (DER - 2020/07/30, HDFFV-11092)
+
+
+    - Add H5Pset/get_file_locking() API calls
+
+      This change adds new API calls which can be used to set or get the
+      file locking parameters. The single API call sets both the "use file
+      locking" flag and the "ignore disabled file locking" flag.
+
+      See the configure option discussion for HDFFV-11092 (above) for more
+      information on the file locking feature and how it's controlled.
+
+      (DER - 2020/07/30, HDFFV-11092)
+
+    Parallel Library:
     -----------------
     -
 
+    Fortran Library:
+    ----------------
+    - Add wrappers for H5Pset/get_file_locking() API calls
+
+      h5pget_file_locking_f()
+      h5pset_file_locking_f()
+
+      See the configure option discussion for HDFFV-11092 (above) for more
+      information on the file locking feature and how it's controlled.
+
+      (DER - 2020/07/30, HDFFV-11092)
+
     C++ Library:
     ------------
     - Added new wrappers for H5Pset/get_create_intermediate_group()
@@ -305,6 +392,15 @@ New Features
 
       (BMR - 2019/04/22, HDFFV-10622)
 
+    - Add wrappers for H5Pset/get_file_locking() API calls
+
+      FileAccPropList::setFileLocking()
+      FileAccPropList::getFileLocking()
+
+      See the configure option discussion for HDFFV-11092 (above) for more
+      information on the file locking feature and how it's controlled.
+
+      (DER - 2020/07/30, HDFFV-11092)
 
     Java Library:
     ----------------
@@ -312,6 +408,19 @@ New Features
 
       (JTH - 2019/04/30)
 
+    - Add wrappers for H5Pset/get_file_locking() API calls
+
+      H5Pset_file_locking()
+      H5Pget_use_file_locking()
+      H5Pget_ignore_disabled_file_locking()
+
+      Unlike the C++ and Fortran wrappers, there are separate getters for the
+      two file locking settings, each of which returns a boolean value.
+
+      See the configure option discussion for HDFFV-11092 (above) for more
+      information on the file locking feature and how it's controlled.
+
+      (DER - 2020/07/30, HDFFV-11092)
 
     Tools:
     ------
diff --git a/src/H5F.c b/src/H5F.c
index 31e5def..2b3dba1 100644
--- a/src/H5F.c
+++ b/src/H5F.c
@@ -60,9 +60,6 @@
 /* Package Variables */
 /*********************/
 
-/* Package initialization variable */
-hbool_t H5_PKG_INIT_VAR = FALSE;
-
 
 /*****************************/
 /* Library Private Variables */
@@ -74,86 +71,6 @@ hbool_t H5_PKG_INIT_VAR = FALSE;
 /*******************/
 
 
-/* File ID class */
-static const H5I_class_t H5I_FILE_CLS[1] = {{
-    H5I_FILE,                   /* ID class value */
-    0,                          /* Class flags */
-    0,                          /* # of reserved IDs for class */
-    (H5I_free_t)H5F__close_cb   /* Callback routine for closing objects of this class */
-}};
-
-
-/*--------------------------------------------------------------------------
-NAME
-   H5F__init_package -- Initialize interface-specific information
-USAGE
-    herr_t H5F__init_package()
-RETURNS
-    Non-negative on success/Negative on failure
-DESCRIPTION
-    Initializes any interface-specific data or routines.
-
---------------------------------------------------------------------------*/
-herr_t
-H5F__init_package(void)
-{
-    herr_t ret_value = SUCCEED;   /* Return value */
-
-    FUNC_ENTER_PACKAGE
-
-    /*
-     * Initialize the atom group for the file IDs.
-     */
-    if(H5I_register_type(H5I_FILE_CLS) < 0)
-        HGOTO_ERROR(H5E_FILE, H5E_CANTINIT, FAIL, "unable to initialize interface")
-
-done:
-    FUNC_LEAVE_NOAPI(ret_value)
-} /* H5F__init_package() */
-
-
-/*-------------------------------------------------------------------------
- * Function:    H5F_term_package
- *
- * Purpose:     Terminate this interface: free all memory and reset global
- *              variables to their initial values.  Release all ID groups
- *              associated with this interface.
- *
- * Return:      Success:    Positive if anything was done that might
- *                          have affected other interfaces;
- *                          zero otherwise.
- *
- *              Failure:    Never fails
- *-------------------------------------------------------------------------
- */
-int
-H5F_term_package(void)
-{
-    int    n = 0;
-
-    FUNC_ENTER_NOAPI_NOINIT_NOERR
-
-    if(H5_PKG_INIT_VAR) {
-        if(H5I_nmembers(H5I_FILE) > 0) {
-            (void)H5I_clear_type(H5I_FILE, FALSE, FALSE);
-            n++; /*H5I*/
-        } /* end if */
-        else {
-            /* Make certain we've cleaned up all the shared file objects */
-            H5F_sfile_assert_num(0);
-
-            /* Destroy the file object id group */
-            n += (H5I_dec_type_ref(H5I_FILE) > 0);
-
-            /* Mark closed */
-            if(0 == n)
-                H5_PKG_INIT_VAR = FALSE;
-        } /* end else */
-    } /* end if */
-
-    FUNC_LEAVE_NOAPI(n)
-} /* end H5F_term_package() */
-
 
 /*-------------------------------------------------------------------------
  * Function:    H5Fget_create_plist
diff --git a/src/H5FD.c b/src/H5FD.c
index 2e80c7f..991b7b7 100644
--- a/src/H5FD.c
+++ b/src/H5FD.c
@@ -1436,7 +1436,7 @@ done:
  *              constant H5P_DEFAULT). The bytes to be written come from the
  *              buffer BUF.
  *
- * Return:      SNon-negative on success/Negative on failure
+ * Return:      Non-negative on success/Negative on failure
  *
  *-------------------------------------------------------------------------
  */
@@ -1642,7 +1642,7 @@ H5FDlock(H5FD_t *file, hbool_t rw)
 
     /* Call private function */
     if(H5FD_lock(file, rw) < 0)
-        HGOTO_ERROR(H5E_VFL, H5E_CANTINIT, FAIL, "file lock request failed")
+        HGOTO_ERROR(H5E_VFL, H5E_CANTLOCKFILE, FAIL, "file lock request failed")
 
 done:
     FUNC_LEAVE_API(ret_value)
@@ -1672,7 +1672,7 @@ H5FD_lock(H5FD_t *file, hbool_t rw)
 
     /* Dispatch to driver */
     if(file->cls->lock && (file->cls->lock)(file, rw) < 0)
-        HGOTO_ERROR(H5E_VFL, H5E_CANTUPDATE, FAIL, "driver lock request failed")
+        HGOTO_ERROR(H5E_VFL, H5E_CANTLOCKFILE, FAIL, "driver lock request failed")
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
@@ -1704,7 +1704,7 @@ H5FDunlock(H5FD_t *file)
 
     /* Call private function */
     if(H5FD_unlock(file) < 0)
-        HGOTO_ERROR(H5E_VFL, H5E_CANTINIT, FAIL, "file unlock request failed")
+        HGOTO_ERROR(H5E_VFL, H5E_CANTUNLOCKFILE, FAIL, "file unlock request failed")
 
 done:
     FUNC_LEAVE_API(ret_value)
@@ -1733,7 +1733,7 @@ H5FD_unlock(H5FD_t *file)
 
     /* Dispatch to driver */
     if(file->cls->unlock && (file->cls->unlock)(file) < 0)
-        HGOTO_ERROR(H5E_VFL, H5E_CANTUPDATE, FAIL, "driver unlock request failed")
+        HGOTO_ERROR(H5E_VFL, H5E_CANTUNLOCKFILE, FAIL, "driver unlock request failed")
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
diff --git a/src/H5FDcore.c b/src/H5FDcore.c
index e4a3207..40d838c 100644
--- a/src/H5FDcore.c
+++ b/src/H5FDcore.c
@@ -36,6 +36,9 @@
 /* The driver identification number, initialized at runtime */
 static hid_t H5FD_CORE_g = 0;
 
+/* Whether to ignore file locks when disabled (env var value) */
+static htri_t ignore_disabled_file_locks_s = FAIL;
+
 /* The skip list node type.  Represents a region in the file. */
 typedef struct H5FD_core_region_t {
     haddr_t start;              /* Start address of the region          */
@@ -55,6 +58,7 @@ typedef struct H5FD_core_t {
     size_t  increment;          /* multiples for mem allocation         */
     hbool_t backing_store;      /* write to file name on flush          */
     size_t  bstore_page_size;   /* backing store page size              */
+    hbool_t ignore_disabled_file_locks;
     int     fd;                 /* backing store file descriptor        */
     /* Information for determining uniqueness of a file with a backing store */
 #ifndef H5_HAVE_WIN32_API
@@ -407,9 +411,19 @@ done:
 static herr_t
 H5FD__init_package(void)
 {
+    char    *lock_env_var   = NULL;     /* Environment variable pointer */
     herr_t ret_value = SUCCEED;
 
-    FUNC_ENTER_NOAPI_NOINIT
+    FUNC_ENTER_STATIC
+
+    /* Check the use disabled file locks environment variable */
+    lock_env_var = HDgetenv("HDF5_USE_FILE_LOCKING");
+    if(lock_env_var && !HDstrcmp(lock_env_var, "BEST_EFFORT"))
+        ignore_disabled_file_locks_s = TRUE;    /* Override: Ignore disabled locks */
+    else if(lock_env_var && (!HDstrcmp(lock_env_var, "TRUE") || !HDstrcmp(lock_env_var, "1")))
+        ignore_disabled_file_locks_s = FALSE;   /* Override: Don't ignore disabled locks */
+    else
+        ignore_disabled_file_locks_s = FAIL;    /* Environment variable not set, or not set correctly */
 
     if(H5FD_core_init() < 0)
         HGOTO_ERROR(H5E_VFL, H5E_CANTINIT, FAIL, "unable to initialize core VFD")
@@ -691,6 +705,16 @@ H5FD__core_open(const char *name, unsigned flags, hid_t fapl_id, haddr_t maxaddr
     /* Save file image callbacks */
     file->fi_callbacks = file_image_info.callbacks;
 
+    /* Check the file locking flags in the fapl */
+    if(ignore_disabled_file_locks_s != FAIL)
+        /* The environment variable was set, so use that preferentially */
+        file->ignore_disabled_file_locks = ignore_disabled_file_locks_s;
+    else {
+        /* Use the value in the property list */
+        if(H5P_get(plist, H5F_ACS_IGNORE_DISABLED_FILE_LOCKS_NAME, &file->ignore_disabled_file_locks) < 0)
+            HGOTO_ERROR(H5E_VFL, H5E_CANTGET, NULL, "can't get ignore disabled file locks property")
+    }
+
     if(fd >= 0) {
         /* Retrieve information for determining uniqueness of file */
 #ifdef H5_HAVE_WIN32_API
@@ -1509,18 +1533,20 @@ H5FD_core_lock(H5FD_t *_file, hbool_t rw)
      * descriptor, this is a no-op.
      */
     if(file->fd >= 0) {
-
         /* Set exclusive or shared lock based on rw status */
         lock_flags = rw ? LOCK_EX : LOCK_SH;
 
         /* Place a non-blocking lock on the file */
         if(HDflock(file->fd, lock_flags | LOCK_NB) < 0) {
-            if(ENOSYS == errno)
-                HSYS_GOTO_ERROR(H5E_FILE, H5E_BADFILE, FAIL, "file locking disabled on this file system (use HDF5_USE_FILE_LOCKING environment variable to override)")
+            if(file->ignore_disabled_file_locks && ENOSYS == errno) {
+                /* When errno is set to ENOSYS, the file system does not support
+                 * locking, so ignore it.
+                 */
+                errno = 0;
+            }
             else
                 HSYS_GOTO_ERROR(H5E_FILE, H5E_BADFILE, FAIL, "unable to lock file")
         } /* end if */
-
     } /* end if */
 
 done:
@@ -1549,16 +1575,17 @@ H5FD_core_unlock(H5FD_t *_file)
 
     HDassert(file);
 
-    if(file->fd >= 0) {
-
+    if(file->fd >= 0)
         if(HDflock(file->fd, LOCK_UN) < 0) {
-            if(ENOSYS == errno)
-                HSYS_GOTO_ERROR(H5E_FILE, H5E_BADFILE, FAIL, "file locking disabled on this file system (use HDF5_USE_FILE_LOCKING environment variable to override)")
+            if(file->ignore_disabled_file_locks && ENOSYS == errno) {
+                /* When errno is set to ENOSYS, the file system does not support
+                 * locking, so ignore it.
+                 */
+                errno = 0;
+            }
             else
                 HSYS_GOTO_ERROR(H5E_FILE, H5E_BADFILE, FAIL, "unable to unlock file")
-        } /* end if */
-
-    } /* end if */
+        }
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
diff --git a/src/H5FDdirect.c b/src/H5FDdirect.c
index 34c4346..4046050 100644
--- a/src/H5FDdirect.c
+++ b/src/H5FDdirect.c
@@ -38,6 +38,9 @@
 /* The driver identification number, initialized at runtime */
 static hid_t H5FD_DIRECT_g = 0;
 
+/* Whether to ignore file locks when disabled (env var value) */
+static htri_t ignore_disabled_file_locks_s = FAIL;
+
 /* File operations */
 #define OP_UNKNOWN  0
 #define OP_READ    1
@@ -71,6 +74,7 @@ typedef struct H5FD_direct_t {
     haddr_t  pos;      /*current file I/O position  */
     int    op;      /*last operation    */
     H5FD_direct_fapl_t  fa;    /*file access properties  */
+    hbool_t         ignore_disabled_file_locks;
 #ifndef H5_HAVE_WIN32_API
     /*
      * On most systems the combination of device and i-node number uniquely
@@ -193,10 +197,20 @@ DESCRIPTION
 static herr_t
 H5FD__init_package(void)
 {
+    char    *lock_env_var   = NULL;     /* Environment variable pointer */
     herr_t ret_value = SUCCEED;
 
     FUNC_ENTER_STATIC
 
+    /* Check the use disabled file locks environment variable */
+    lock_env_var = HDgetenv("HDF5_USE_FILE_LOCKING");
+    if(lock_env_var && !HDstrcmp(lock_env_var, "BEST_EFFORT"))
+        ignore_disabled_file_locks_s = TRUE;    /* Override: Ignore disabled locks */
+    else if(lock_env_var && (!HDstrcmp(lock_env_var, "TRUE") || !HDstrcmp(lock_env_var, "1")))
+        ignore_disabled_file_locks_s = FALSE;   /* Override: Don't ignore disabled locks */
+    else
+        ignore_disabled_file_locks_s = FAIL;    /* Environment variable not set, or not set correctly */
+
     if(H5FD_direct_init() < 0)
         HGOTO_ERROR(H5E_VFL, H5E_CANTINIT, FAIL, "unable to initialize direct VFD")
 
@@ -518,6 +532,16 @@ H5FD_direct_open(const char *name, unsigned flags, hid_t fapl_id, haddr_t maxadd
     file->fa.fbsize = fa->fbsize;
     file->fa.cbsize = fa->cbsize;
 
+    /* Check the file locking flags in the fapl */
+    if(ignore_disabled_file_locks_s != FAIL)
+        /* The environment variable was set, so use that preferentially */
+        file->ignore_disabled_file_locks = ignore_disabled_file_locks_s;
+    else {
+        /* Use the value in the property list */
+        if(H5P_get(plist, H5F_ACS_IGNORE_DISABLED_FILE_LOCKS_NAME, &file->ignore_disabled_file_locks) < 0)
+            HGOTO_ERROR(H5E_VFL, H5E_CANTGET, NULL, "can't get ignore disabled file locks property")
+    }
+
     /* Try to decide if data alignment is required.  The reason to check it here
      * is to handle correctly the case that the file is in a different file system
      * than the one where the program is running.
@@ -1335,16 +1359,27 @@ static herr_t
 H5FD_direct_lock(H5FD_t *_file, hbool_t rw)
 {
     H5FD_direct_t  *file = (H5FD_direct_t*)_file;	/* VFD file struct */
-    const int lock = rw ? LOCK_EX : LOCK_SH;
+    int lock_flags;                                 /* file locking flags   */
     herr_t ret_value = SUCCEED;                 	/* Return value */
 
     FUNC_ENTER_NOAPI_NOINIT
 
     HDassert(file);
 
-    /* Place the lock with non-blocking */
-    if(HDflock(file->fd, lock | LOCK_NB) < 0)
-        HSYS_GOTO_ERROR(H5E_FILE, H5E_BADFILE, FAIL, "unable to flock file")
+    /* Set exclusive or shared lock based on rw status */
+    lock_flags = rw ? LOCK_EX : LOCK_SH;
+
+    /* Place a non-blocking lock on the file */
+    if(HDflock(file->fd, lock_flags | LOCK_NB) < 0) {
+        if(file->ignore_disabled_file_locks && ENOSYS == errno) {
+            /* When errno is set to ENOSYS, the file system does not support
+             * locking, so ignore it.
+             */
+            errno = 0;
+        }
+        else
+            HSYS_GOTO_ERROR(H5E_VFL, H5E_CANTLOCKFILE, FAIL, "unable to lock file")
+    }
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
@@ -1372,8 +1407,16 @@ H5FD_direct_unlock(H5FD_t *_file)
 
     HDassert(file);
 
-    if(HDflock(file->fd, LOCK_UN) < 0)
-        HSYS_GOTO_ERROR(H5E_FILE, H5E_BADFILE, FAIL, "unable to flock (unlock) file")
+    if(HDflock(file->fd, LOCK_UN) < 0) {
+        if(file->ignore_disabled_file_locks && ENOSYS == errno) {
+            /* When errno is set to ENOSYS, the file system does not support
+             * locking, so ignore it.
+             */
+            errno = 0;
+        }
+        else
+            HSYS_GOTO_ERROR(H5E_VFL, H5E_CANTUNLOCKFILE, FAIL, "unable to unlock file")
+    }
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
diff --git a/src/H5FDfamily.c b/src/H5FDfamily.c
index d110ef7..154878e 100644
--- a/src/H5FDfamily.c
+++ b/src/H5FDfamily.c
@@ -1372,9 +1372,9 @@ H5FD_family_lock(H5FD_t *_file, hbool_t rw)
         for(v = 0; v < u; v++) {
             if(H5FD_unlock(file->memb[v]) < 0)
                 /* Push error, but keep going */
-                HDONE_ERROR(H5E_IO, H5E_CANTUNLOCK, FAIL, "unable to unlock member files")
+                HDONE_ERROR(H5E_IO, H5E_CANTUNLOCKFILE, FAIL, "unable to unlock member files")
         } /* end for */
-        HGOTO_ERROR(H5E_IO, H5E_CANTLOCK, FAIL, "unable to lock member files")
+        HGOTO_ERROR(H5E_IO, H5E_CANTLOCKFILE, FAIL, "unable to lock member files")
     } /* end if */
 
 done:
@@ -1406,7 +1406,7 @@ H5FD_family_unlock(H5FD_t *_file)
     for(u = 0; u < file->nmembs; u++)
         if(file->memb[u])
             if(H5FD_unlock(file->memb[u]) < 0)
-                HGOTO_ERROR(H5E_IO, H5E_CANTUNLOCK, FAIL, "unable to unlock member files")
+                HGOTO_ERROR(H5E_IO, H5E_CANTUNLOCKFILE, FAIL, "unable to unlock member files")
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
diff --git a/src/H5FDlog.c b/src/H5FDlog.c
index f649bc4..d34a273 100644
--- a/src/H5FDlog.c
+++ b/src/H5FDlog.c
@@ -40,6 +40,9 @@
 /* The driver identification number, initialized at runtime */
 static hid_t H5FD_LOG_g = 0;
 
+/* Whether to ignore file locks when disabled (env var value) */
+static htri_t ignore_disabled_file_locks_s = FAIL;
+
 /* Driver-specific file access properties */
 typedef struct H5FD_log_fapl_t {
     char *logfile;              /* Allocated log file name */
@@ -80,6 +83,7 @@ typedef struct H5FD_log_t {
     haddr_t         eof;    /* end of file; current file size   */
     haddr_t         pos;    /* current file I/O position        */
     H5FD_file_op_t  op;     /* last operation                   */
+    hbool_t         ignore_disabled_file_locks;
     char            filename[H5FD_MAX_FILENAME_LEN];    /* Copy of file name from open operation */
 #ifndef H5_HAVE_WIN32_API
     /* On most systems the combination of device and i-node number uniquely
@@ -234,10 +238,20 @@ H5FL_DEFINE_STATIC(H5FD_log_t);
 static herr_t
 H5FD__init_package(void)
 {
+    char    *lock_env_var   = NULL;     /* Environment variable pointer */
     herr_t ret_value = SUCCEED;
 
     FUNC_ENTER_STATIC
 
+    /* Check the use disabled file locks environment variable */
+    lock_env_var = HDgetenv("HDF5_USE_FILE_LOCKING");
+    if(lock_env_var && !HDstrcmp(lock_env_var, "BEST_EFFORT"))
+        ignore_disabled_file_locks_s = TRUE;    /* Override: Ignore disabled locks */
+    else if(lock_env_var && (!HDstrcmp(lock_env_var, "TRUE") || !HDstrcmp(lock_env_var, "1")))
+        ignore_disabled_file_locks_s = FALSE;   /* Override: Don't ignore disabled locks */
+    else
+        ignore_disabled_file_locks_s = FAIL;    /* Environment variable not set, or not set correctly */
+
     if(H5FD_log_init() < 0)
         HGOTO_ERROR(H5E_VFL, H5E_CANTINIT, FAIL, "unable to initialize log VFD")
 
@@ -640,6 +654,16 @@ H5FD_log_open(const char *name, unsigned flags, hid_t fapl_id, haddr_t maxaddr)
 
     } /* end if */
 
+    /* Check the file locking flags in the fapl */
+    if(ignore_disabled_file_locks_s != FAIL)
+        /* The environment variable was set, so use that preferentially */
+        file->ignore_disabled_file_locks = ignore_disabled_file_locks_s;
+    else {
+        /* Use the value in the property list */
+        if(H5P_get(plist, H5F_ACS_IGNORE_DISABLED_FILE_LOCKS_NAME, &file->ignore_disabled_file_locks) < 0)
+            HGOTO_ERROR(H5E_VFL, H5E_CANTGET, NULL, "can't get ignore disabled file locks property")
+    }
+
     /* Check for non-default FAPL */
     if(H5P_FILE_ACCESS_DEFAULT != fapl_id) {
         /* This step is for h5repart tool only. If user wants to change file driver from
@@ -1713,11 +1737,15 @@ H5FD_log_lock(H5FD_t *_file, hbool_t rw)
 
     /* Place a non-blocking lock on the file */
     if(HDflock(file->fd, lock_flags | LOCK_NB) < 0) {
-        if(ENOSYS == errno)
-            HSYS_GOTO_ERROR(H5E_FILE, H5E_BADFILE, FAIL, "file locking disabled on this file system (use HDF5_USE_FILE_LOCKING environment variable to override)")
+        if(file->ignore_disabled_file_locks && ENOSYS == errno) {
+            /* When errno is set to ENOSYS, the file system does not support
+             * locking, so ignore it.
+             */
+            errno = 0;
+        }
         else
-            HSYS_GOTO_ERROR(H5E_FILE, H5E_BADFILE, FAIL, "unable to lock file")
-    } /* end if */
+            HSYS_GOTO_ERROR(H5E_VFL, H5E_CANTLOCKFILE, FAIL, "unable to lock file")
+    }
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
@@ -1746,11 +1774,15 @@ H5FD_log_unlock(H5FD_t *_file)
     HDassert(file);
 
     if(HDflock(file->fd, LOCK_UN) < 0) {
-        if(ENOSYS == errno)
-            HSYS_GOTO_ERROR(H5E_FILE, H5E_BADFILE, FAIL, "file locking disabled on this file system (use HDF5_USE_FILE_LOCKING environment variable to override)")
+        if(file->ignore_disabled_file_locks && ENOSYS == errno) {
+            /* When errno is set to ENOSYS, the file system does not support
+             * locking, so ignore it.
+             */
+            errno = 0;
+        }
         else
-            HSYS_GOTO_ERROR(H5E_FILE, H5E_BADFILE, FAIL, "unable to unlock file")
-    } /* end if */
+            HSYS_GOTO_ERROR(H5E_VFL, H5E_CANTUNLOCKFILE, FAIL, "unable to unlock file")
+    }
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
diff --git a/src/H5FDmulti.c b/src/H5FDmulti.c
index 72f4da5..f80cac5 100644
--- a/src/H5FDmulti.c
+++ b/src/H5FDmulti.c
@@ -1856,7 +1856,7 @@ H5FD_multi_lock(H5FD_t *_file, hbool_t rw)
     } /* end if */
 
     if(nerrors)
-        H5Epush_ret(func, H5E_ERR_CLS, H5E_INTERNAL, H5E_BADVALUE, "error locking member files", -1)
+        H5Epush_ret(func, H5E_ERR_CLS, H5E_VFL, H5E_CANTLOCKFILE, "error locking member files", -1)
     return 0;
 
 } /* H5FD_multi_lock() */
@@ -1893,7 +1893,7 @@ H5FD_multi_unlock(H5FD_t *_file)
     } END_MEMBERS;
 
     if(nerrors)
-        H5Epush_ret(func, H5E_ERR_CLS, H5E_INTERNAL, H5E_BADVALUE, "error unlocking member files", -1)
+        H5Epush_ret(func, H5E_ERR_CLS, H5E_VFL, H5E_CANTUNLOCKFILE, "error unlocking member files", -1)
 
     return 0;
 } /* H5FD_multi_unlock() */
diff --git a/src/H5FDsec2.c b/src/H5FDsec2.c
index ba4750e..cbb707a 100644
--- a/src/H5FDsec2.c
+++ b/src/H5FDsec2.c
@@ -39,6 +39,9 @@
 /* The driver identification number, initialized at runtime */
 static hid_t H5FD_SEC2_g = 0;
 
+/* Whether to ignore file locks when disabled (env var value) */
+static htri_t ignore_disabled_file_locks_s = FAIL;
+
 /* The description of a file belonging to this driver. The 'eoa' and 'eof'
  * determine the amount of hdf5 address space in use and the high-water mark
  * of the file (the current size of the underlying filesystem file). The
@@ -57,6 +60,7 @@ typedef struct H5FD_sec2_t {
     haddr_t         eof;    /* end of file; current file size   */
     haddr_t         pos;    /* current file I/O position        */
     H5FD_file_op_t  op;     /* last operation                   */
+    hbool_t         ignore_disabled_file_locks;
     char            filename[H5FD_MAX_FILENAME_LEN];    /* Copy of file name from open operation */
 #ifndef H5_HAVE_WIN32_API
     /* On most systems the combination of device and i-node number uniquely
@@ -190,10 +194,20 @@ H5FL_DEFINE_STATIC(H5FD_sec2_t);
 static herr_t
 H5FD__init_package(void)
 {
+    char    *lock_env_var   = NULL;     /* Environment variable pointer */
     herr_t ret_value = SUCCEED;
 
     FUNC_ENTER_STATIC
 
+    /* Check the use disabled file locks environment variable */
+    lock_env_var = HDgetenv("HDF5_USE_FILE_LOCKING");
+    if(lock_env_var && !HDstrcmp(lock_env_var, "BEST_EFFORT"))
+        ignore_disabled_file_locks_s = TRUE;    /* Override: Ignore disabled locks */
+    else if(lock_env_var && (!HDstrcmp(lock_env_var, "TRUE") || !HDstrcmp(lock_env_var, "1")))
+        ignore_disabled_file_locks_s = FALSE;   /* Override: Don't ignore disabled locks */
+    else
+        ignore_disabled_file_locks_s = FAIL;    /* Environment variable not set, or not set correctly */
+
     if(H5FD_sec2_init() < 0)
         HGOTO_ERROR(H5E_VFL, H5E_CANTINIT, FAIL, "unable to initialize sec2 VFD")
 
@@ -316,6 +330,7 @@ H5FD_sec2_open(const char *name, unsigned flags, hid_t fapl_id, haddr_t maxaddr)
     struct _BY_HANDLE_FILE_INFORMATION fileinfo;
 #endif
     h5_stat_t       sb;
+    H5P_genplist_t  *plist;                 /* Property list pointer */
     H5FD_t          *ret_value = NULL;          /* Return value */
 
     FUNC_ENTER_NOAPI_NOINIT
@@ -373,17 +388,26 @@ H5FD_sec2_open(const char *name, unsigned flags, hid_t fapl_id, haddr_t maxaddr)
     file->inode = sb.st_ino;
 #endif /* H5_HAVE_WIN32_API */
 
+    /* Get the FAPL */
+    if(NULL == (plist = (H5P_genplist_t *)H5I_object(fapl_id)))
+        HGOTO_ERROR(H5E_VFL, H5E_BADTYPE, NULL, "not a file access property list")
+
+    /* Check the file locking flags in the fapl */
+    if(ignore_disabled_file_locks_s != FAIL)
+        /* The environment variable was set, so use that preferentially */
+        file->ignore_disabled_file_locks = ignore_disabled_file_locks_s;
+    else {
+        /* Use the value in the property list */
+        if(H5P_get(plist, H5F_ACS_IGNORE_DISABLED_FILE_LOCKS_NAME, &file->ignore_disabled_file_locks) < 0)
+            HGOTO_ERROR(H5E_VFL, H5E_CANTGET, NULL, "can't get ignore disabled file locks property")
+    }
+
     /* Retain a copy of the name used to open the file, for possible error reporting */
     HDstrncpy(file->filename, name, sizeof(file->filename));
     file->filename[sizeof(file->filename) - 1] = '\0';
 
     /* Check for non-default FAPL */
     if(H5P_FILE_ACCESS_DEFAULT != fapl_id) {
-        H5P_genplist_t      *plist;      /* Property list pointer */
-
-        /* Get the FAPL */
-        if(NULL == (plist = (H5P_genplist_t *)H5I_object(fapl_id)))
-            HGOTO_ERROR(H5E_VFL, H5E_BADTYPE, NULL, "not a file access property list")
 
         /* This step is for h5repart tool only. If user wants to change file driver from
          * family to one that uses single files (sec2, etc.) while using h5repart, this
@@ -955,11 +979,15 @@ H5FD_sec2_lock(H5FD_t *_file, hbool_t rw)
 
     /* Place a non-blocking lock on the file */
     if(HDflock(file->fd, lock_flags | LOCK_NB) < 0) {
-        if(ENOSYS == errno)
-            HSYS_GOTO_ERROR(H5E_FILE, H5E_BADFILE, FAIL, "file locking disabled on this file system (use HDF5_USE_FILE_LOCKING environment variable to override)")
+        if(file->ignore_disabled_file_locks && ENOSYS == errno) {
+            /* When errno is set to ENOSYS, the file system does not support
+             * locking, so ignore it.
+             */
+            errno = 0;
+        }
         else
-            HSYS_GOTO_ERROR(H5E_FILE, H5E_BADFILE, FAIL, "unable to lock file")
-    } /* end if */
+            HSYS_GOTO_ERROR(H5E_VFL, H5E_CANTLOCKFILE, FAIL, "unable to lock file")
+    }
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
@@ -988,11 +1016,15 @@ H5FD_sec2_unlock(H5FD_t *_file)
     HDassert(file);
 
     if(HDflock(file->fd, LOCK_UN) < 0) {
-        if(ENOSYS == errno)
-            HSYS_GOTO_ERROR(H5E_FILE, H5E_BADFILE, FAIL, "file locking disabled on this file system (use HDF5_USE_FILE_LOCKING environment variable to override)")
+        if(file->ignore_disabled_file_locks && ENOSYS == errno) {
+            /* When errno is set to ENOSYS, the file system does not support
+             * locking, so ignore it.
+             */
+            errno = 0;
+        }
         else
-            HSYS_GOTO_ERROR(H5E_FILE, H5E_BADFILE, FAIL, "unable to unlock file")
-    } /* end if */
+            HSYS_GOTO_ERROR(H5E_VFL, H5E_CANTUNLOCKFILE, FAIL, "unable to unlock file")
+    }
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
diff --git a/src/H5FDstdio.c b/src/H5FDstdio.c
index d29a1b4..a769e86 100644
--- a/src/H5FDstdio.c
+++ b/src/H5FDstdio.c
@@ -52,6 +52,9 @@
 /* The driver identification number, initialized at runtime */
 static hid_t H5FD_STDIO_g = 0;
 
+/* Whether to ignore file locks when disabled (env var value) */
+static htri_t ignore_disabled_file_locks_s = -1;
+
 /* The maximum number of bytes which can be written in a single I/O operation */
 static size_t H5_STDIO_MAX_IO_BYTES_g = (size_t)-1;
 
@@ -82,6 +85,7 @@ typedef struct H5FD_stdio_t {
     haddr_t     eof;            /* end of file; current file size   */
     haddr_t     pos;            /* current file I/O position        */
     unsigned    write_access;   /* Flag to indicate the file was opened with write access */
+    hbool_t     ignore_disabled_file_locks;
     H5FD_stdio_file_op op;  /* last operation */
 #ifndef H5_HAVE_WIN32_API
     /* On most systems the combination of device and i-node number uniquely
@@ -231,11 +235,23 @@ static const H5FD_class_t H5FD_stdio_g = {
 hid_t
 H5FD_stdio_init(void)
 {
+    char    *lock_env_var   = NULL;     /* Environment variable pointer */
+
     /* Clear the error stack */
     H5Eclear2(H5E_DEFAULT);
 
-    if (H5I_VFL!=H5Iget_type(H5FD_STDIO_g))
+    /* Check the use disabled file locks environment variable */
+    lock_env_var = getenv("HDF5_USE_FILE_LOCKING");
+    if(lock_env_var && !strcmp(lock_env_var, "BEST_EFFORT"))
+        ignore_disabled_file_locks_s = 1;       /* Override: Ignore disabled locks */
+    else if(lock_env_var && (!strcmp(lock_env_var, "TRUE") || !strcmp(lock_env_var, "1")))
+        ignore_disabled_file_locks_s = 0;       /* Override: Don't ignore disabled locks */
+    else
+        ignore_disabled_file_locks_s = -1;      /* Environment variable not set, or not set correctly */
+
+    if (H5I_VFL != H5Iget_type(H5FD_STDIO_g))
         H5FD_STDIO_g = H5FDregister(&H5FD_stdio_g);
+
     return H5FD_STDIO_g;
 } /* end H5FD_stdio_init() */
 
@@ -318,7 +334,7 @@ H5Pset_fapl_stdio(hid_t fapl_id)
  *-------------------------------------------------------------------------
  */
 static H5FD_t *
-H5FD_stdio_open( const char *name, unsigned flags, hid_t /*UNUSED*/ fapl_id,
+H5FD_stdio_open( const char *name, unsigned flags, hid_t fapl_id,
     haddr_t maxaddr)
 {
     FILE                *f = NULL;
@@ -396,6 +412,21 @@ H5FD_stdio_open( const char *name, unsigned flags, hid_t /*UNUSED*/ fapl_id,
         file->eof = (haddr_t)x;
     }
 
+    /* Check the file locking flags in the fapl */
+    if(ignore_disabled_file_locks_s != -1)
+        /* The environment variable was set, so use that preferentially */
+        file->ignore_disabled_file_locks = ignore_disabled_file_locks_s;
+    else {
+        hbool_t unused;
+
+        /* Use the value in the property list */
+        if(H5Pget_file_locking(fapl_id, &unused, &file->ignore_disabled_file_locks) < 0) {
+            free(file);
+            fclose(f);
+            H5Epush_ret(func, H5E_ERR_CLS, H5E_FILE, H5E_CANTGET, "unable to get use disabled file locks property", NULL);
+        }
+    }
+
     /* Get the file descriptor (needed for truncate and some Windows information) */
 #ifdef H5_HAVE_WIN32_API
     file->fd = _fileno(file->fp);
@@ -1104,10 +1135,13 @@ H5FD_stdio_lock(H5FD_t *_file, hbool_t rw)
 
     /* Place a non-blocking lock on the file */
     if(flock(file->fd, lock_flags | LOCK_NB) < 0) {
-        if(ENOSYS == errno)
-            H5Epush_ret(func, H5E_ERR_CLS, H5E_IO, H5E_FCNTL, "file locking disabled on this file system (use HDF5_USE_FILE_LOCKING environment variable to override)", -1)
+        if(file->ignore_disabled_file_locks && ENOSYS == errno)
+            /* When errno is set to ENOSYS, the file system does not support
+             * locking, so ignore it.
+             */
+            errno = 0;
         else
-            H5Epush_ret(func, H5E_ERR_CLS, H5E_IO, H5E_FCNTL, "file lock failed", -1)
+            H5Epush_ret(func, H5E_ERR_CLS, H5E_VFL, H5E_CANTLOCKFILE, "file lock failed", -1)
     } /* end if */
 
     /* Flush the stream */
@@ -1152,10 +1186,13 @@ H5FD_stdio_unlock(H5FD_t *_file)
 
     /* Place a non-blocking lock on the file */
     if(flock(file->fd, LOCK_UN) < 0) {
-        if(ENOSYS == errno)
-            H5Epush_ret(func, H5E_ERR_CLS, H5E_IO, H5E_FCNTL, "file locking disabled on this file system (use HDF5_USE_FILE_LOCKING environment variable to override)", -1)
+        if(file->ignore_disabled_file_locks && ENOSYS == errno)
+            /* When errno is set to ENOSYS, the file system does not support
+             * locking, so ignore it.
+             */
+            errno = 0;
         else
-            H5Epush_ret(func, H5E_ERR_CLS, H5E_IO, H5E_FCNTL, "file unlock failed", -1)
+            H5Epush_ret(func, H5E_ERR_CLS, H5E_VFL, H5E_CANTUNLOCKFILE, "file unlock failed", -1)
     } /* end if */
 
 #endif /* H5_HAVE_FLOCK */
diff --git a/src/H5Fint.c b/src/H5Fint.c
index eb023d6..29bbd45 100644
--- a/src/H5Fint.c
+++ b/src/H5Fint.c
@@ -77,6 +77,7 @@ static herr_t H5F__get_objects(const H5F_t *f, unsigned types, size_t max_index,
 static int H5F__get_objects_cb(void *obj_ptr, hid_t obj_id, void *key);
 static herr_t H5F__build_name(const char *prefix, const char *file_name, char **full_name/*out*/);
 static char *H5F__getenv_prefix_name(char **env_prefix/*in,out*/);
+static herr_t H5F__check_if_using_file_locks(H5P_genplist_t *fapl, hbool_t *use_file_locking);
 static herr_t H5F__build_actual_name(const H5F_t *f, const H5P_genplist_t *fapl, const char *name, char ** /*out*/ actual_name);
 static herr_t H5F__flush_phase1(H5F_t *f);
 static herr_t H5F__flush_phase2(H5F_t *f, hbool_t closing);
@@ -86,6 +87,15 @@ static herr_t H5F__flush_phase2(H5F_t *f, hbool_t closing);
 /* Package Variables */
 /*********************/
 
+/* Package initialization variable */
+hbool_t H5_PKG_INIT_VAR = FALSE;
+
+/* Based on the value of the HDF5_USE_FILE_LOCKING environment variable.
+ * TRUE/FALSE have obvious meanings. FAIL means the environment variable was
+ * not set, so the code should ignore it and use the fapl value instead.
+ */
+htri_t use_locks_env_g = FAIL;
+
 
 /*****************************/
 /* Library Private Variables */
@@ -102,6 +112,123 @@ H5FL_DEFINE(H5F_t);
 /* Declare a free list to manage the H5F_shared_t struct */
 H5FL_DEFINE(H5F_shared_t);
 
+/* File ID class */
+static const H5I_class_t H5I_FILE_CLS[1] = {{
+    H5I_FILE,                   /* ID class value */
+    0,                          /* Class flags */
+    0,                          /* # of reserved IDs for class */
+    (H5I_free_t)H5F__close_cb   /* Callback routine for closing objects of this class */
+}};
+
+
+
+/*--------------------------------------------------------------------------
+NAME
+   H5F__init_package -- Initialize interface-specific information
+USAGE
+    herr_t H5F__init_package()
+RETURNS
+    Non-negative on success/Negative on failure
+DESCRIPTION
+    Initializes any interface-specific data or routines.
+
+--------------------------------------------------------------------------*/
+herr_t
+H5F__init_package(void)
+{
+    herr_t  ret_value       = SUCCEED;  /* Return value */
+
+    FUNC_ENTER_PACKAGE
+
+    /*
+     * Initialize the atom group for the file IDs.
+     */
+    if(H5I_register_type(H5I_FILE_CLS) < 0)
+        HGOTO_ERROR(H5E_FILE, H5E_CANTINIT, FAIL, "unable to initialize interface")
+
+    /* Check the file locking environment variable */
+    if(H5F__parse_file_lock_env_var(&use_locks_env_g) < 0)
+        HGOTO_ERROR(H5E_FILE, H5E_CANTGET, FAIL, "unable to parse file locking environment variable")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* H5F__init_package() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5F_term_package
+ *
+ * Purpose:     Terminate this interface: free all memory and reset global
+ *              variables to their initial values.  Release all ID groups
+ *              associated with this interface.
+ *
+ * Return:      Success:    Positive if anything was done that might
+ *                          have affected other interfaces;
+ *                          zero otherwise.
+ *
+ *              Failure:    Never fails
+ *
+ *-------------------------------------------------------------------------
+ */
+int
+H5F_term_package(void)
+{
+    int    n = 0;
+
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+
+    if(H5_PKG_INIT_VAR) {
+        if(H5I_nmembers(H5I_FILE) > 0) {
+            (void)H5I_clear_type(H5I_FILE, FALSE, FALSE);
+            n++; /*H5I*/
+        } /* end if */
+        else {
+            /* Make certain we've cleaned up all the shared file objects */
+            H5F_sfile_assert_num(0);
+
+            /* Destroy the file object id group */
+            n += (H5I_dec_type_ref(H5I_FILE) > 0);
+
+            /* Mark closed */
+            if(0 == n)
+                H5_PKG_INIT_VAR = FALSE;
+        } /* end else */
+    } /* end if */
+
+    FUNC_LEAVE_NOAPI(n)
+} /* end H5F_term_package() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5F__parse_file_lock_env_var
+ *
+ * Purpose:     Parses the HDF5_USE_FILE_LOCKING environment variable.
+ *
+ * NOTE:        This is done in a separate function so we can call it from
+ *              the test code.
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5F__parse_file_lock_env_var(htri_t *use_locks)
+{
+    char    *lock_env_var   = NULL;     /* Environment variable pointer */
+
+    FUNC_ENTER_PACKAGE_NOERR
+
+    /* Check the file locking environment variable */
+    lock_env_var = HDgetenv("HDF5_USE_FILE_LOCKING");
+    if(lock_env_var && (!HDstrcmp(lock_env_var, "FALSE") || !HDstrcmp(lock_env_var, "0")))
+        *use_locks = FALSE;    /* Override: Never use locks */
+    else if(lock_env_var && (!HDstrcmp(lock_env_var, "TRUE") || !HDstrcmp(lock_env_var, "BEST_EFFORT") || !HDstrcmp(lock_env_var, "1")))
+        *use_locks = TRUE;     /* Override: Always use locks */
+    else
+        *use_locks = FAIL;      /* Environment variable not set, or not set correctly */
+
+    FUNC_LEAVE_NOAPI(SUCCEED)
+} /* end H5F__parse_file_lock_env_var() */
 
 
 /*-------------------------------------------------------------------------
@@ -1334,6 +1461,52 @@ H5F__dest(H5F_t *f, hbool_t flush)
 
 
 /*-------------------------------------------------------------------------
+ * Function:    H5F__check_if_using_file_locks
+ *
+ * Purpose:     Determines if this file will use file locks.
+ *
+ * There are three ways that file locking can be controlled:
+ *
+ * 1) The configure/cmake option that sets the H5_USE_FILE_LOCKING
+ *    symbol (which is used as the default fapl value).
+ *
+ * 2) The H5Pset_file_locking() API call, which will override
+ *    the configuration default.
+ *
+ * 3) The HDF5_USE_FILE_LOCKING environment variable, which overrides
+ *    everything above.
+ *
+ * The main reason to disable file locking is to prevent errors on file
+ * systems where locking is not supported or has been disabled (as is
+ * often the case in parallel file systems).
+ *
+ * Return:      SUCCEED/FAIL
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5F__check_if_using_file_locks(H5P_genplist_t *fapl, hbool_t *use_file_locking)
+{
+    herr_t  ret_value       = SUCCEED;      /* Return value */
+
+    FUNC_ENTER_STATIC
+
+    /* Make sure the out parameter has a value */
+    *use_file_locking = TRUE;
+
+    /* Check the fapl property */
+    if(H5P_get(fapl, H5F_ACS_USE_FILE_LOCKING_NAME, use_file_locking) < 0)
+        HGOTO_ERROR(H5E_FILE, H5E_CANTGET, FAIL, "can't get use file locking flag")
+
+    /* Check the environment variable */
+    if(use_locks_env_g != FAIL)
+        *use_file_locking = (use_locks_env_g == TRUE) ? TRUE : FALSE;
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5F__check_if_using_file_locks() */
+
+
+/*-------------------------------------------------------------------------
  * Function:    H5F_open
  *
  * Purpose:    Opens (or creates) a file.  This function understands the
@@ -1422,8 +1595,7 @@ H5F_open(const char *name, unsigned flags, hid_t fcpl_id, hid_t fapl_id)
     hbool_t             set_flag = FALSE;   /*set the status_flags in the superblock */
     hbool_t             clear = FALSE;      /*clear the status_flags         */
     hbool_t             evict_on_close;     /* evict on close value from plist  */
-    char               *lock_env_var = NULL;/*env var pointer               */
-    hbool_t             use_file_locking;   /*read from env var             */
+    hbool_t             use_file_locking = TRUE;    /* Using file locks? */
     hbool_t             ci_load = FALSE;    /* whether MDC ci load requested */
     hbool_t             ci_write = FALSE;   /* whether MDC CI write requested */
     H5F_t              *ret_value = NULL;   /*actual return value           */
@@ -1441,15 +1613,13 @@ H5F_open(const char *name, unsigned flags, hid_t fcpl_id, hid_t fapl_id)
     if(NULL == (drvr = H5FD_get_class(fapl_id)))
         HGOTO_ERROR(H5E_FILE, H5E_CANTGET, NULL, "unable to retrieve VFL class")
 
-    /* Check the environment variable that determines if we care
-     * about file locking. File locking should be used unless explicitly
-     * disabled.
-     */
-    lock_env_var = HDgetenv("HDF5_USE_FILE_LOCKING");
-    if(lock_env_var && !HDstrcmp(lock_env_var, "FALSE"))
-        use_file_locking = FALSE;
-    else
-        use_file_locking = TRUE;
+    /* Get the file access property list, for future queries */
+    if(NULL == (a_plist = (H5P_genplist_t *)H5I_object(fapl_id)))
+        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, NULL, "not file access property list")
+
+    /* Check if we are using file locking */
+    if (H5F__check_if_using_file_locks(a_plist, &use_file_locking) < 0)
+        HGOTO_ERROR(H5E_FILE, H5E_CANTGET, NULL, "unable to get file locking flag")
 
     /*
      * Opening a file is a two step process. First we try to open the
@@ -1540,8 +1710,8 @@ H5F_open(const char *name, unsigned flags, hid_t fcpl_id, hid_t fapl_id)
             if(H5FD_lock(lf, (hbool_t)((flags & H5F_ACC_RDWR) ? TRUE : FALSE)) < 0) {
                 /* Locking failed - Closing will remove the lock */
                 if(H5FD_close(lf) < 0)
-                    HDONE_ERROR(H5E_FILE, H5E_CANTOPENFILE, NULL, "unable to close low-level file info")
-                HGOTO_ERROR(H5E_FILE, H5E_CANTOPENFILE, NULL, "unable to lock the file")
+                    HDONE_ERROR(H5E_FILE, H5E_CANTCLOSEFILE, NULL, "unable to close low-level file info")
+                HGOTO_ERROR(H5E_FILE, H5E_CANTLOCKFILE, NULL, "unable to lock the file")
             } /* end if */
 
         /* Create the 'top' file structure */
@@ -1573,10 +1743,6 @@ H5F_open(const char *name, unsigned flags, hid_t fcpl_id, hid_t fapl_id)
     shared = file->shared;
     lf = shared->lf;
 
-    /* Get the file access property list, for future queries */
-    if(NULL == (a_plist = (H5P_genplist_t *)H5I_object(fapl_id)))
-        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, NULL, "not file access property list")
-
     /* Check if page buffering is enabled */
     if(H5P_get(a_plist, H5F_ACS_PAGE_BUFFER_SIZE_NAME, &page_buf_size) < 0)
         HGOTO_ERROR(H5E_FILE, H5E_CANTGET, NULL, "can't get page buffer size")
@@ -1715,7 +1881,7 @@ H5F_open(const char *name, unsigned flags, hid_t fcpl_id, hid_t fapl_id)
             /* Remove the file lock for SWMR_WRITE */
             if(use_file_locking && (H5F_INTENT(file) & H5F_ACC_SWMR_WRITE)) {
                 if(H5FD_unlock(file->shared->lf) < 0)
-                    HGOTO_ERROR(H5E_FILE, H5E_CANTOPENFILE, NULL, "unable to unlock the file")
+                    HGOTO_ERROR(H5E_FILE, H5E_CANTUNLOCKFILE, NULL, "unable to unlock the file")
             } /* end if */
         } /* end if */
         else { /* H5F_ACC_RDONLY: check consistency of status_flags */
diff --git a/src/H5Fpkg.h b/src/H5Fpkg.h
index e4892ed..6e3f3d4 100644
--- a/src/H5Fpkg.h
+++ b/src/H5Fpkg.h
@@ -389,6 +389,10 @@ H5FL_EXTERN(H5F_t);
 /* Declare a free list to manage the H5F_shared_t struct */
 H5FL_EXTERN(H5F_shared_t);
 
+/* Whether or not to use file locking (based on the environment variable)
+ * FAIL means ignore the environment variable.
+ */
+H5_DLLVAR htri_t use_locks_env_g;
 
 /******************************/
 /* Package Private Prototypes */
@@ -407,6 +411,7 @@ H5_DLL herr_t H5F__start_swmr_write(H5F_t *f);
 H5_DLL herr_t H5F__close(hid_t file_id);
 H5_DLL herr_t H5F__close_cb(H5F_t *f);
 H5_DLL herr_t H5F__set_libver_bounds(H5F_t *f, H5F_libver_t low, H5F_libver_t high);
+H5_DLL herr_t H5F__parse_file_lock_env_var(htri_t *use_locks);
 
 /* File mount related routines */
 H5_DLL herr_t H5F__mount(H5G_loc_t *loc, const char *name, H5F_t *child, hid_t plist_id);
@@ -466,6 +471,7 @@ H5_DLL herr_t H5F__get_sohm_mesg_count_test(hid_t fid, unsigned type_id, size_t
 H5_DLL herr_t H5F__check_cached_stab_test(hid_t file_id);
 H5_DLL herr_t H5F__get_maxaddr_test(hid_t file_id, haddr_t *maxaddr);
 H5_DLL herr_t H5F__get_sbe_addr_test(hid_t file_id, haddr_t *sbe_addr);
+H5_DLL herr_t H5F__reparse_file_lock_variable_test(void);
 #endif /* H5F_TESTING */
 
 #endif /* _H5Fpkg_H */
diff --git a/src/H5Fprivate.h b/src/H5Fprivate.h
index 57318a7..fd161e2 100644
--- a/src/H5Fprivate.h
+++ b/src/H5Fprivate.h
@@ -516,6 +516,8 @@ typedef struct H5F_t H5F_t;
 #define H5F_ACS_PAGE_BUFFER_SIZE_NAME           "page_buffer_size" /* the maximum size for the page buffer cache */
 #define H5F_ACS_PAGE_BUFFER_MIN_META_PERC_NAME  "page_buffer_min_meta_perc" /* the min metadata percentage for the page buffer cache */
 #define H5F_ACS_PAGE_BUFFER_MIN_RAW_PERC_NAME   "page_buffer_min_raw_perc" /* the min raw data percentage for the page buffer cache */
+#define H5F_ACS_USE_FILE_LOCKING_NAME           "use_file_locking" /* whether or not we use file locks for SWMR control and to prevent multiple writers */
+#define H5F_ACS_IGNORE_DISABLED_FILE_LOCKS_NAME "ignore_disabled_file_locks" /* whether or not we ignore "locks disabled" errors */
 
 /* ======================== File Mount properties ====================*/
 #define H5F_MNT_SYM_LOCAL_NAME         "local"                 /* Whether absolute symlinks local to file. */
diff --git a/src/H5Ftest.c b/src/H5Ftest.c
index df9c933..e9d697a 100644
--- a/src/H5Ftest.c
+++ b/src/H5Ftest.c
@@ -232,3 +232,36 @@ done:
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5F__get_sbe_addr_test() */
 
+
+/*-------------------------------------------------------------------------
+ * Function:    H5F__reparse_file_lock_variable_test
+ *
+ * Purpose:     Re-parse the file locking environment variable.
+ *
+ *              Since getenv(3) is fairly expensive, we only parse it once,
+ *              when the library opens. This test function is used to
+ *              re-parse the environment variable after we've changed it
+ *              with setnev(3).
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ * Programmer:	Dana Robinson
+ *              Summer 2020
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5F__reparse_file_lock_variable_test(void)
+{
+    herr_t ret_value = SUCCEED;
+
+    FUNC_ENTER_PACKAGE
+
+    /* Check the file locking environment variable */
+    if(H5F__parse_file_lock_env_var(&use_locks_env_g) < 0)
+        HGOTO_ERROR(H5E_FILE, H5E_CANTGET, FAIL, "unable to parse file locking environment variable")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5F__reparse_file_lock_variable_test() */
+
diff --git a/src/H5Pfapl.c b/src/H5Pfapl.c
index b2a1a30..208c8dd 100644
--- a/src/H5Pfapl.c
+++ b/src/H5Pfapl.c
@@ -259,6 +259,29 @@
 #define H5F_ACS_PAGE_BUFFER_MIN_RAW_PERC_DEF            0
 #define H5F_ACS_PAGE_BUFFER_MIN_RAW_PERC_ENC            H5P__encode_unsigned
 #define H5F_ACS_PAGE_BUFFER_MIN_RAW_PERC_DEC            H5P__decode_unsigned
+/* Definition for using file locking or not. The default is set
+ * via the configure step.
+ */
+#define H5F_ACS_USE_FILE_LOCKING_SIZE                   sizeof(hbool_t)
+#if defined H5_USE_FILE_LOCKING && H5_USE_FILE_LOCKING
+#define H5F_ACS_USE_FILE_LOCKING_DEF                    TRUE
+#else
+#define H5F_ACS_USE_FILE_LOCKING_DEF                    FALSE
+#endif
+#define H5F_ACS_USE_FILE_LOCKING_ENC                    H5P__encode_hbool_t
+#define H5F_ACS_USE_FILE_LOCKING_DEC                    H5P__decode_hbool_t
+/* Definition for whether we ignore file locking errors when we can
+ * tell that file locking has been disabled on the file system.
+ * The default is set via the configure step.
+ */
+#define H5F_ACS_IGNORE_DISABLED_FILE_LOCKS_SIZE         sizeof(hbool_t)
+#if defined H5_IGNORE_DISABLED_FILE_LOCKS && H5_IGNORE_DISABLED_FILE_LOCKS
+#define H5F_ACS_IGNORE_DISABLED_FILE_LOCKS_DEF          TRUE
+#else
+#define H5F_ACS_IGNORE_DISABLED_FILE_LOCKS_DEF          FALSE
+#endif
+#define H5F_ACS_IGNORE_DISABLED_FILE_LOCKS_ENC          H5P__encode_hbool_t
+#define H5F_ACS_IGNORE_DISABLED_FILE_LOCKS_DEC          H5P__decode_hbool_t
 
 
 /******************/
@@ -398,6 +421,8 @@ static const H5AC_cache_image_config_t H5F_def_mdc_initCacheImageCfg_g = H5F_ACS
 static const size_t H5F_def_page_buf_size_g = H5F_ACS_PAGE_BUFFER_SIZE_DEF;      /* Default page buffer size */
 static const unsigned H5F_def_page_buf_min_meta_perc_g = H5F_ACS_PAGE_BUFFER_MIN_META_PERC_DEF;      /* Default page buffer minimum metadata size */
 static const unsigned H5F_def_page_buf_min_raw_perc_g = H5F_ACS_PAGE_BUFFER_MIN_RAW_PERC_DEF;      /* Default page buffer mininum raw data size */
+static const hbool_t H5F_def_use_file_locking_g = H5F_ACS_USE_FILE_LOCKING_DEF;                 /* Default use file locking flag */
+static const hbool_t H5F_def_ignore_disabled_file_locks_g = H5F_ACS_IGNORE_DISABLED_FILE_LOCKS_DEF;     /* Default ignore disabled file locks flag */
 
 
 /*-------------------------------------------------------------------------
@@ -647,6 +672,16 @@ H5P__facc_reg_prop(H5P_genclass_t *pclass)
             NULL, NULL, NULL, NULL) < 0)
         HGOTO_ERROR(H5E_PLIST, H5E_CANTINSERT, FAIL, "can't insert property into class")
 
+    /* Register the use file locking flag */
+    if(H5P__register_real(pclass, H5F_ACS_USE_FILE_LOCKING_NAME, H5F_ACS_USE_FILE_LOCKING_SIZE, &H5F_def_use_file_locking_g,
+            NULL, NULL, NULL, H5F_ACS_USE_FILE_LOCKING_ENC, H5F_ACS_USE_FILE_LOCKING_DEC, NULL, NULL, NULL, NULL) < 0)
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTINSERT, FAIL, "can't insert property into class")
+
+    /* Register the ignore disabled file locks flag */
+    if(H5P__register_real(pclass, H5F_ACS_IGNORE_DISABLED_FILE_LOCKS_NAME, H5F_ACS_IGNORE_DISABLED_FILE_LOCKS_SIZE, &H5F_def_ignore_disabled_file_locks_g,
+            NULL, NULL, NULL, H5F_ACS_IGNORE_DISABLED_FILE_LOCKS_ENC, H5F_ACS_IGNORE_DISABLED_FILE_LOCKS_DEC, NULL, NULL, NULL, NULL) < 0)
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTINSERT, FAIL, "can't insert property into class")
+
 done:
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5P__facc_reg_prop() */
@@ -4586,6 +4621,98 @@ done:
     FUNC_LEAVE_API(ret_value)
 } /* end H5Pget_evict_on_close() */
 
+
+/*-------------------------------------------------------------------------
+ * Function:    H5Pset_file_locking
+ *
+ * Purpose:     Sets the file locking property values.
+ *
+ *              Overrides the default file locking flag setting that was
+ *              set when the library was configured.
+ *
+ *              Can be overridden by the HDF5_USE_FILE_LOCKING environment
+ *              variable.
+ *
+ *              File locking is used when creating/opening a file to prevent
+ *              problematic file accesses.
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ * Programmer:  Dana Robinson
+ *              Spring 2020
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5Pset_file_locking(hid_t fapl_id, hbool_t use_file_locking, hbool_t ignore_when_disabled)
+{
+    H5P_genplist_t *plist;          /* property list pointer */
+    herr_t ret_value = SUCCEED;     /* return value */
+
+    FUNC_ENTER_API(FAIL)
+    H5TRACE3("e", "ibb", fapl_id, use_file_locking, ignore_when_disabled);
+
+    /* Make sure this is a fapl */
+    if(TRUE != H5P_isa_class(fapl_id, H5P_FILE_ACCESS))
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTREGISTER, FAIL, "property list is not a file access plist")
+
+    /* Get the plist structure */
+    if(NULL == (plist = (H5P_genplist_t *)H5I_object(fapl_id)))
+        HGOTO_ERROR(H5E_ATOM, H5E_BADATOM, FAIL, "can't find object for ID")
+
+    /* Set values */
+    if(H5P_set(plist, H5F_ACS_USE_FILE_LOCKING_NAME, &use_file_locking) < 0)
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "can't set use file locking property")
+    if(H5P_set(plist, H5F_ACS_IGNORE_DISABLED_FILE_LOCKS_NAME, &ignore_when_disabled) < 0)
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTSET, FAIL, "can't set ignore disabled file locks property")
+
+done:
+    FUNC_LEAVE_API(ret_value)
+} /* end H5Pset_file_locking() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5Pget_file_locking
+ *
+ * Purpose:     Gets the file locking property values.
+ *
+ *              File locking is used when creating/opening a file to prevent
+ *              problematic file accesses.
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ * Programmer:  Dana Robinson
+ *              Spring 2020
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5Pget_file_locking(hid_t fapl_id, hbool_t *use_file_locking, hbool_t *ignore_when_disabled)
+{
+    H5P_genplist_t *plist;          /* property list pointer */
+    herr_t ret_value = SUCCEED;     /* return value */
+
+    FUNC_ENTER_API(FAIL)
+    H5TRACE3("e", "i*b*b", fapl_id, use_file_locking, ignore_when_disabled);
+
+    /* Make sure this is a fapl */
+    if(TRUE != H5P_isa_class(fapl_id, H5P_FILE_ACCESS))
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTREGISTER, FAIL, "property list is not an access plist")
+
+    /* Get the plist structure */
+    if(NULL == (plist = (H5P_genplist_t *)H5I_object(fapl_id)))
+        HGOTO_ERROR(H5E_ATOM, H5E_BADATOM, FAIL, "can't find object for ID")
+
+    /* Get values */
+    if(H5P_get(plist, H5F_ACS_USE_FILE_LOCKING_NAME, use_file_locking) < 0)
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "can't get use file locking property")
+    if(H5P_get(plist, H5F_ACS_IGNORE_DISABLED_FILE_LOCKS_NAME, ignore_when_disabled) < 0)
+        HGOTO_ERROR(H5E_PLIST, H5E_CANTGET, FAIL, "can't get ignore disabled file locks property")
+
+done:
+    FUNC_LEAVE_API(ret_value)
+} /* end H5Pget_file_locking() */
+
 #ifdef H5_HAVE_PARALLEL
 
 /*-------------------------------------------------------------------------
diff --git a/src/H5Ppublic.h b/src/H5Ppublic.h
index 5d6dea8..dbd0724 100644
--- a/src/H5Ppublic.h
+++ b/src/H5Ppublic.h
@@ -359,6 +359,8 @@ H5_DLL herr_t H5Pset_mdc_log_options(hid_t plist_id, hbool_t is_enabled, const c
 H5_DLL herr_t H5Pget_mdc_log_options(hid_t plist_id, hbool_t *is_enabled, char *location, size_t *location_size, hbool_t *start_on_access);
 H5_DLL herr_t H5Pset_evict_on_close(hid_t fapl_id, hbool_t evict_on_close);
 H5_DLL herr_t H5Pget_evict_on_close(hid_t fapl_id, hbool_t *evict_on_close);
+H5_DLL herr_t H5Pset_file_locking(hid_t fapl_id, hbool_t use_file_locking, hbool_t ignore_when_disabled);
+H5_DLL herr_t H5Pget_file_locking(hid_t fapl_id, hbool_t *use_file_locking, hbool_t *ignore_when_disabled);
 #ifdef H5_HAVE_PARALLEL
 H5_DLL herr_t H5Pset_all_coll_metadata_ops(hid_t plist_id, hbool_t is_collective);
 H5_DLL herr_t H5Pget_all_coll_metadata_ops(hid_t plist_id, hbool_t *is_collective);
diff --git a/src/H5err.txt b/src/H5err.txt
index 30c646f..f3cca72 100644
--- a/src/H5err.txt
+++ b/src/H5err.txt
@@ -133,6 +133,8 @@ MINOR, FILEACC, H5E_NOTHDF5, Not an HDF5 file
 MINOR, FILEACC, H5E_BADFILE, Bad file ID accessed
 MINOR, FILEACC, H5E_TRUNCATED, File has been truncated
 MINOR, FILEACC, H5E_MOUNT, File mount error
+MINOR, FILEACC, H5E_CANTLOCKFILE, Unable to lock file
+MINOR, FILEACC, H5E_CANTUNLOCKFILE, Unable to unlock file
 
 # Generic low-level file I/O errors
 MINOR, FILE, H5E_SEEKERROR, Seek failed
diff --git a/src/H5private.h b/src/H5private.h
index c0d39fc..78746c3 100644
--- a/src/H5private.h
+++ b/src/H5private.h
@@ -863,8 +863,8 @@ H5_DLL H5_ATTR_CONST int Nflock(int fd, int operation);
 #ifndef HDflock
     /* NOTE: flock(2) is not present on all POSIX systems.
      * If it is not present, we try a flock() equivalent based on
-     * fcntl(2), then fall back to a function that always fails if
-     * it is not present at all (Windows uses a separate Wflock()
+     * fcntl(2), then fall back to a function that always succeeds
+     * if it is not present at all (Windows uses a separate Wflock()
      * function).
      */
     #if defined(H5_HAVE_FLOCK)
diff --git a/src/H5system.c b/src/H5system.c
index a7ca3f8..dfb8d21 100644
--- a/src/H5system.c
+++ b/src/H5system.c
@@ -647,14 +647,14 @@ Pflock(int fd, int operation) {
  * Purpose:     Wrapper function for systems where no file locking is
  *              available.
  *
- * Return:      Failure:    -1 (always fails)
+ * Return:      0 (success)
  *
  *-------------------------------------------------------------------------
  */
 int H5_ATTR_CONST
 Nflock(int H5_ATTR_UNUSED fd, int H5_ATTR_UNUSED operation) {
-    /* just fail */
-    return -1;
+    /* just succeed */
+    return 0;
 } /* end Nflock() */
 
 
diff --git a/src/libhdf5.settings.in b/src/libhdf5.settings.in
index 422ca0b..b1c1b2b 100644
--- a/src/libhdf5.settings.in
+++ b/src/libhdf5.settings.in
@@ -87,5 +87,6 @@ Parallel Filtered Dataset Writes: @PARALLEL_FILTERED_WRITES@
             Using memory checker: @USINGMEMCHECKER@
  Memory allocation sanity checks: @MEMORYALLOCSANITYCHECK@
           Function stack tracing: @CODESTACK@
+                Use file locking: @DESIRED_FILE_LOCKING@
        Strict file format checks: @STRICT_FORMAT_CHECKS@
     Optimization instrumentation: @INSTRUMENT_LIBRARY@
diff --git a/test/h5test.c b/test/h5test.c
index 2613ce1..5e6f01a 100644
--- a/test/h5test.c
+++ b/test/h5test.c
@@ -1941,3 +1941,61 @@ const char *H5_get_srcdir(void)
         return(NULL);
 } /* end H5_get_srcdir() */
 
+/*-------------------------------------------------------------------------
+ * Function:    h5_check_if_file_locking_enabled
+ *
+ * Purpose:     Checks if file locking is enabled on this file system.
+ *
+ * Return:      SUCCEED/FAIL
+ *              are_enabled will be FALSE if file locking is disabled on
+ *              the file system of if there were errors.
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+h5_check_if_file_locking_enabled(hbool_t *is_enabled)
+{
+    const char *filename = "locking_test_file";
+    int pmode = O_RDWR | O_CREAT | O_TRUNC;
+    int fd = -1;
+
+    *is_enabled = TRUE;
+
+    if((fd = HDopen(filename, pmode, H5_POSIX_CREATE_MODE_RW)) < 0)
+        goto error;
+
+    /* Test HDflock() to see if it works */
+    if(HDflock(fd, LOCK_EX | LOCK_NB) < 0) {
+        if(ENOSYS == errno) {
+            /* When errno is set to ENOSYS, the file system does not support
+             * locking, so ignore it. This is most frequently used on
+             * Lustre. If we also want to check for disabled NFS locks
+             * we'll need to check for ENOLCK, too. That isn't done by
+             * default here since that could also represent an actual
+             * error condition.
+             */
+            errno = 0;
+            *is_enabled = FALSE;
+        }
+        else
+            goto error;
+    }
+    if(HDflock(fd, LOCK_UN) < 0)
+        goto error;
+
+    if(HDclose(fd) < 0)
+        goto error;
+    if(HDremove(filename) < 0)
+        goto error;
+
+    return SUCCEED;
+
+error:
+    *is_enabled = FALSE;
+    if (fd > -1) {
+        HDclose(fd);
+        HDremove(filename);
+    }
+    return FAIL;
+} /* end h5_check_if_file_locking_enabled() */
+
diff --git a/test/h5test.h b/test/h5test.h
index 0d937e1..35eea98 100644
--- a/test/h5test.h
+++ b/test/h5test.h
@@ -206,6 +206,7 @@ H5TEST_DLL int h5_make_local_copy(const char *origfilename, const char *local_co
 H5TEST_DLL herr_t h5_verify_cached_stabs(const char *base_name[], hid_t fapl);
 H5TEST_DLL H5FD_class_t *h5_get_dummy_vfd_class(void);
 H5TEST_DLL const char *h5_get_version_string(H5F_libver_t libver);
+H5TEST_DLL herr_t h5_check_if_file_locking_enabled(hbool_t *are_enabled);
 
 /* Functions that will replace components of a FAPL */
 H5TEST_DLL herr_t h5_get_vfd_fapl(hid_t fapl_id);
diff --git a/test/swmr.c b/test/swmr.c
index 700a68c..a407dac 100644
--- a/test/swmr.c
+++ b/test/swmr.c
@@ -90,7 +90,7 @@ static int test_file_lock_concur(hid_t fapl);
 static int test_file_lock_swmr_concur(hid_t fapl);
 
 /* Test file lock environment variable */
-static int test_file_lock_env_var(hid_t fapl);
+static int test_file_locking(hid_t in_fapl, hbool_t turn_locking_on, hbool_t env_var_override);
 
 /* Tests for SWMR VFD flag */
 static int test_swmr_vfd_flag(void);
@@ -4255,8 +4255,11 @@ test_file_lock_same(hid_t in_fapl)
     /* Output message about test being performed */
     TESTING("File open with different combinations of flags--single process access");
 
+    /* Set locking in the fapl */
     if((fapl = H5Pcopy(in_fapl)) < 0)
         FAIL_STACK_ERROR
+    if(H5Pset_file_locking(fapl, TRUE, TRUE) < 0)
+        FAIL_STACK_ERROR
 
     /* Set the filename to use for this test (dependent on fapl) */
     h5_fixname(FILENAME[1], fapl, filename, sizeof(filename));
@@ -4415,9 +4418,11 @@ test_file_lock_swmr_same(hid_t in_fapl)
     /* Output message about test being performed */
     TESTING("File open with different combinations of flags + SWMR flags--single process access");
 
-    /* Get a copy of the parameter in_fapl */
+    /* Set locking in the fapl */
     if((fapl = H5Pcopy(in_fapl)) < 0)
         FAIL_STACK_ERROR
+    if(H5Pset_file_locking(fapl, TRUE, TRUE) < 0)
+        FAIL_STACK_ERROR
 
     /* Set the filename to use for this test (dependent on fapl) */
     h5_fixname(FILENAME[1], fapl, filename, sizeof(filename));
@@ -4725,8 +4730,11 @@ test_file_lock_concur(hid_t in_fapl)
     /* Output message about test being performed */
     TESTING("File open with different combinations of flags--concurrent access");
 
+    /* Set locking in the fapl */
     if((fapl = H5Pcopy(in_fapl)) < 0)
         FAIL_STACK_ERROR
+    if(H5Pset_file_locking(fapl, TRUE, TRUE) < 0)
+        FAIL_STACK_ERROR
 
     /* Set the filename to use for this test (dependent on fapl) */
     h5_fixname(FILENAME[1], fapl, filename, sizeof(filename));
@@ -5101,8 +5109,11 @@ test_file_lock_swmr_concur(hid_t in_fapl)
     /* Output message about test being performed */
     TESTING("File open with different combintations of flags + SWMR flags--concurrent access");
 
+    /* Set locking in the fapl */
     if((fapl = H5Pcopy(in_fapl)) < 0)
         FAIL_STACK_ERROR
+    if(H5Pset_file_locking(fapl, TRUE, TRUE) < 0)
+        FAIL_STACK_ERROR
 
     /* Set the filename to use for this test (dependent on fapl) */
     h5_fixname(FILENAME[2], fapl, filename, sizeof(filename));
@@ -5597,7 +5608,7 @@ test_file_lock_swmr_concur(hid_t in_fapl)
 
         /* Open the test file */
         H5E_BEGIN_TRY {
-            child_fid = H5Fopen(filename, H5F_ACC_RDWR, H5P_DEFAULT);
+            child_fid = H5Fopen(filename, H5F_ACC_RDWR, fapl);
         } H5E_END_TRY;
 
         /* Should fail */
@@ -5921,7 +5932,7 @@ test_file_lock_swmr_concur(hid_t in_fapl)
         FAIL_STACK_ERROR
 
     /* Open the test file */
-    if((fid = H5Fopen(filename, H5F_ACC_RDONLY, H5P_DEFAULT)) < 0)
+    if((fid = H5Fopen(filename, H5F_ACC_RDONLY, fapl)) < 0)
         FAIL_STACK_ERROR
 
     /* Notify child process */
@@ -6058,7 +6069,7 @@ error:
 **
 *****************************************************************/
 static int
-test_file_lock_env_var(hid_t in_fapl)
+test_file_locking(hid_t in_fapl, hbool_t turn_locking_on, hbool_t env_var_override)
 {
 #if !(defined(H5_HAVE_FORK) && defined(H5_HAVE_WAITPID))
     SKIPPED();
@@ -6073,18 +6084,40 @@ test_file_lock_env_var(hid_t in_fapl)
     int child_wait_option=0;        /* Options passed to waitpid */
     int out_pdf[2];
     int notify = 0;
+    int exit_status = 0;
+    herr_t ret;
+
+    if (turn_locking_on && env_var_override)
+        TESTING("File locking: ON w/ env var override")
+    else if (turn_locking_on && !env_var_override)
+        TESTING("File locking: ON")
+    else if (!turn_locking_on && env_var_override)
+        TESTING("File locking: OFF w/ env var override")
+    else
+        TESTING("File locking: OFF")
 
-
-    TESTING("File locking environment variable");
-
-
-    /* Set the environment variable */
-    if(HDsetenv("HDF5_USE_FILE_LOCKING", "FALSE", TRUE) < 0)
+    /* Copy the incoming fapl */
+    if((fapl = H5Pcopy(in_fapl)) < 0)
         TEST_ERROR
 
-    if((fapl = H5Pcopy(in_fapl)) < 0)
+    /* Set locking in the fapl */
+    if(H5Pset_file_locking(fapl, turn_locking_on ? TRUE : FALSE, TRUE) < 0)
         TEST_ERROR
 
+    /* If requested, set the environment variable */
+    if (env_var_override) {
+        if(HDsetenv("HDF5_USE_FILE_LOCKING", turn_locking_on ? "FALSE" : "TRUE", TRUE) < 0)
+            TEST_ERROR
+        if(H5F__reparse_file_lock_variable_test() < 0)
+            TEST_ERROR
+    }
+    else {
+        if(HDsetenv("HDF5_USE_FILE_LOCKING", "", TRUE) < 0)
+            TEST_ERROR
+        if(H5F__reparse_file_lock_variable_test() < 0)
+            TEST_ERROR
+    }
+
     /* Set the filename to use for this test (dependent on fapl) */
     h5_fixname(FILENAME[1], fapl, filename, sizeof(filename));
 
@@ -6096,10 +6129,8 @@ test_file_lock_env_var(hid_t in_fapl)
     if(H5Fclose(fid) < 0)
         TEST_ERROR
 
-    /* Open a file for read-only and then read-write. This would
-     * normally fail due to the file locking scheme but should
-     * pass when the environment variable is set to disable file
-     * locking.
+    /* Open a file for read-only and then read-write. This will fail
+     * when the locking scheme is turned on.
      */
 
     /* Create 1 pipe */
@@ -6114,7 +6145,7 @@ test_file_lock_env_var(hid_t in_fapl)
 
         /* Child process */
 
-        hid_t child_fid;    /* File ID */
+        hid_t child_fid = H5I_INVALID_HID;  /* File ID */
         int child_notify = 0;
 
         /* Close unused write end for out_pdf */
@@ -6125,18 +6156,23 @@ test_file_lock_env_var(hid_t in_fapl)
         while(child_notify != 1) {
             if(HDread(out_pdf[0], &child_notify, sizeof(int)) < 0)
                 HDexit(EXIT_FAILURE);
-        } /* end while */
+        }
 
-        /* Open the test file */
-        if((child_fid = H5Fopen(filename, H5F_ACC_RDWR, fapl)) < 0)
-            TEST_ERROR
+        /* Open and close the test file */
+        H5E_BEGIN_TRY {
+            child_fid = H5Fopen(filename, H5F_ACC_RDWR, fapl);
+            ret = H5Fclose(child_fid);
+        } H5E_END_TRY; 
 
         /* Close the pipe */
         if(HDclose(out_pdf[0]) < 0)
             HDexit(EXIT_FAILURE);
 
-        HDexit(EXIT_SUCCESS);
-    } /* end if */
+        if(H5I_INVALID_HID == child_fid || FAIL == ret)
+            HDexit(EXIT_FAILURE);
+        else
+            HDexit(EXIT_SUCCESS);
+    } /* end child process work */
 
     /* close unused read end for out_pdf */
     if(HDclose(out_pdf[0]) < 0)
@@ -6159,15 +6195,28 @@ test_file_lock_env_var(hid_t in_fapl)
     if(HDwaitpid(childpid, &child_status, child_wait_option) < 0)
         TEST_ERROR
 
-    /* Check if child terminated normally */
-    if(WIFEXITED(child_status)) {
-        /* Check exit status of the child */
-        if(WEXITSTATUS(child_status) != 0)
-            TEST_ERROR
-    } /* end if */
+    /* Check exit status of the child */
+    if(WIFEXITED(child_status))
+        exit_status = WEXITSTATUS(child_status);
     else
         TEST_ERROR
 
+    /* The child process should have passed or failed as follows:
+     *
+     * locks on:                            FAIL
+     * locks off:                           PASS
+     * locks on, env var override:          PASS
+     * locks off, env var override:         FAIL
+     */
+    if(turn_locking_on && !env_var_override && (0 == exit_status))
+        TEST_ERROR
+    else if(!turn_locking_on && !env_var_override && (0 != exit_status))
+        TEST_ERROR
+    else if(turn_locking_on && env_var_override && (0 != exit_status))
+        TEST_ERROR
+    else if(!turn_locking_on && env_var_override && (0 == exit_status))
+        TEST_ERROR
+
     /* Close the file */
     if(H5Fclose(fid) < 0)
         TEST_ERROR
@@ -6191,7 +6240,7 @@ error:
 
 #endif /* !(defined(H5_HAVE_FORK && defined(H5_HAVE_WAITPID)) */
 
-} /* end test_file_lock_env_var() */
+} /* end test_file_locking() */
 
 
 static int
@@ -7018,7 +7067,7 @@ error:
         H5Fclose(fid3);
     } H5E_END_TRY;
 
-    return -1;
+    return 1;
 
 } /* test_multiple_same() */
 
@@ -7035,6 +7084,7 @@ main(void)
     char *driver = NULL;    /* VFD string (from env variable) */
     char *lock_env_var = NULL; /* file locking env var pointer */
     hbool_t use_file_locking;   /* read from env var */
+    hbool_t file_locking_enabled = FALSE;   /* Checks if the file system supports locks */
 
     /* Skip this test if SWMR I/O is not supported for the VFD specified
      * by the environment variable.
@@ -7055,6 +7105,13 @@ main(void)
     else
         use_file_locking = TRUE;
 
+    /* Check if file locking is enabled on this file system */
+    if(use_file_locking)
+        if(h5_check_if_file_locking_enabled(&file_locking_enabled) < 0) {
+            HDprintf("Error when determining if file locks are enabled\n");
+            return EXIT_FAILURE;
+        }
+
     /* Set up */
     h5_reset();
 
@@ -7096,7 +7153,7 @@ main(void)
     nerrors += test_append_flush_dataset_fixed(fapl);
     nerrors += test_append_flush_dataset_multiple(fapl);
 
-    if(use_file_locking) {
+    if(use_file_locking && file_locking_enabled) {
         /*
          * Tests for:
          *   file open flags--single process access
@@ -7126,7 +7183,12 @@ main(void)
     /* This test changes the HDF5_USE_FILE_LOCKING environment variable
      * so it should be run last.
      */
-    nerrors += test_file_lock_env_var(fapl);
+    if (use_file_locking && file_locking_enabled) {
+        nerrors += test_file_locking(fapl, TRUE, TRUE);
+        nerrors += test_file_locking(fapl, TRUE, FALSE);
+        nerrors += test_file_locking(fapl, FALSE, TRUE);
+        nerrors += test_file_locking(fapl, FALSE, FALSE);
+    }
 
     if(nerrors)
         goto error;