Onion VFD (#1953)

* Onion VFD feature

* Fixes onion VFD errors with non-sec2 backing store VFDs

* Disables the onion VFD tests w/ ph5diff

* Disables non-sec2 VFDs as onion VFD backing stores

* Committing clang-format changes

* Formatted source

* Typo

* Adds onion VFD tools tests to CMake

* Fixes for v16 API compatibility

* Memset structs to avoid bad frees on errors

* H5Dwrite() calls now use H5T_NATIVE_INT as the memory type vs LE

* Properly decodes checksums on BE machines

* Be more careful about uint64_t to haddr_t/hsize_t conversions

* Another fix for BE data comparison

* Removed double underscores from onion constants

* Replace hard-coded onion header string w/ constant

* Fixes cleanup paths in H5FD__onion_ingest_history()

* Fixed use of size_t revision numbers

* Fix h5dump revision count format string

Co-authored-by: github-actions <41898282+github-actions[bot]@users.noreply.github.com>

12 files changed, 805 insertions, 24 deletions

diff --git a/tools/test/h5diff/CMakeTests.cmake b/tools/test/h5diff/CMakeTests.cmake
index 8e01605..21761c6 100644
--- a/tools/test/h5diff/CMakeTests.cmake
+++ b/tools/test/h5diff/CMakeTests.cmake
@@ -70,6 +70,13 @@
       ${HDF5_TOOLS_TEST_H5DIFF_SOURCE_DIR}/testfiles/h5diff_strings2.h5
       ${HDF5_TOOLS_TEST_H5DIFF_SOURCE_DIR}/testfiles/h5diff_eps1.h5
       ${HDF5_TOOLS_TEST_H5DIFF_SOURCE_DIR}/testfiles/h5diff_eps2.h5
+      # onion VFD files
+      ${HDF5_TOOLS_TEST_H5DIFF_SOURCE_DIR}/testfiles/h5diff_onion_objs.h5
+      ${HDF5_TOOLS_TEST_H5DIFF_SOURCE_DIR}/testfiles/h5diff_onion_objs.h5.onion
+      ${HDF5_TOOLS_TEST_H5DIFF_SOURCE_DIR}/testfiles/h5diff_onion_dset_ext.h5
+      ${HDF5_TOOLS_TEST_H5DIFF_SOURCE_DIR}/testfiles/h5diff_onion_dset_ext.h5.onion
+      ${HDF5_TOOLS_TEST_H5DIFF_SOURCE_DIR}/testfiles/h5diff_onion_dset_1d.h5
+      ${HDF5_TOOLS_TEST_H5DIFF_SOURCE_DIR}/testfiles/h5diff_onion_dset_1d.h5.onion
       # tools/testfiles/vds
       ${HDF5_TOOLS_DIR}/testfiles/vds/1_a.h5
       ${HDF5_TOOLS_DIR}/testfiles/vds/1_b.h5
@@ -295,6 +302,9 @@
       ${HDF5_TOOLS_TEST_H5DIFF_SOURCE_DIR}/testfiles/h5diff_801.txt
       ${HDF5_TOOLS_TEST_H5DIFF_SOURCE_DIR}/testfiles/h5diff_830.txt
       ${HDF5_TOOLS_TEST_H5DIFF_SOURCE_DIR}/testfiles/h5diff_90.txt
+      ${HDF5_TOOLS_TEST_H5DIFF_SOURCE_DIR}/testfiles/h5diff_900.txt
+      ${HDF5_TOOLS_TEST_H5DIFF_SOURCE_DIR}/testfiles/h5diff_901.txt
+      ${HDF5_TOOLS_TEST_H5DIFF_SOURCE_DIR}/testfiles/h5diff_902.txt
       ${HDF5_TOOLS_TEST_H5DIFF_SOURCE_DIR}/testfiles/h5diff_8625.txt
       ${HDF5_TOOLS_TEST_H5DIFF_SOURCE_DIR}/testfiles/h5diff_8639.txt
       ${HDF5_TOOLS_TEST_H5DIFF_SOURCE_DIR}/testfiles/h5diff_reg.txt
@@ -932,6 +942,12 @@
           h5diff_8639.out.err
           h5diff_90.out
           h5diff_90.out.err
+          h5diff_900.out
+          h5diff_900.out.err
+          h5diff_901.out
+          h5diff_901.out.err
+          h5diff_902.out
+          h5diff_902.out.err
           h5diff_v1.out
           h5diff_v1.out.err
           h5diff_v2.out
@@ -1563,6 +1579,13 @@ ADD_H5_TEST (h5diff_v1 0 -v ${FILEV1} ${FILEV2})
 ADD_H5_TEST (h5diff_v2 0 -r ${FILEV1} ${FILEV2})
 ADD_H5_TEST (h5diff_v3 0 -c ${FILEV1} ${FILEV2})
 
+# ##############################################################################
+# # onion VFD tests (serial only)
+# ##############################################################################
+ADD_SH5_TEST (h5diff_900 1 -r -v --vfd-name-1 onion --vfd-info-1 0 --vfd-name-2 onion --vfd-info-2 1 h5diff_onion_objs.h5 h5diff_onion_objs.h5)
+ADD_SH5_TEST (h5diff_901 0 -r -v --vfd-name-1 onion --vfd-info-1 0 --vfd-name-2 onion --vfd-info-2 1 h5diff_onion_dset_ext.h5 h5diff_onion_dset_ext.h5)
+ADD_SH5_TEST (h5diff_902 1 -r -v --vfd-name-1 onion --vfd-info-1 0 --vfd-name-2 onion --vfd-info-2 1 h5diff_onion_dset_1d.h5 h5diff_onion_dset_1d.h5)
+
 ##############################################################################
 ###    P L U G I N  T E S T S
 ##############################################################################
diff --git a/tools/test/h5diff/h5diffgentest.c b/tools/test/h5diff/h5diffgentest.c
index f388568..a66a7b8 100644
--- a/tools/test/h5diff/h5diffgentest.c
+++ b/tools/test/h5diff/h5diffgentest.c
@@ -38,30 +38,34 @@ size_t H5TOOLS_MALLOCSIZE = (128 * 1024 * 1024);
  *-------------------------------------------------------------------------
  */
 
-#define FILE1             "h5diff_basic1.h5"
-#define FILE2             "h5diff_basic2.h5"
-#define FILE3             "h5diff_types.h5"
-#define FILE4             "h5diff_dtypes.h5"
-#define FILE5             "h5diff_attr1.h5"
-#define FILE6             "h5diff_attr2.h5"
-#define FILE6a            "h5diff_attr3.h5"
-#define FILE7             "h5diff_dset1.h5"
-#define FILE8             "h5diff_dset2.h5"
-#define FILE8A            "h5diff_dset3.h5"
-#define FILE9             "h5diff_hyper1.h5"
-#define FILE10            "h5diff_hyper2.h5"
-#define FILE11            "h5diff_empty.h5"
-#define FILE12            "h5diff_links.h5"
-#define FILE13            "h5diff_softlinks.h5"
-#define FILE14            "h5diff_linked_softlink.h5"
-#define FILE15            "h5diff_extlink_src.h5"
-#define FILE16            "h5diff_extlink_trg.h5"
-#define FILE17            "h5diff_ext2softlink_src.h5"
-#define FILE18            "h5diff_ext2softlink_trg.h5"
-#define FILE19            "h5diff_dset_zero_dim_size1.h5"
-#define FILE20            "h5diff_dset_zero_dim_size2.h5"
-#define FILE21            "h5diff_dset_idx1.h5"
-#define FILE22            "h5diff_dset_idx2.h5"
+#define FILE1  "h5diff_basic1.h5"
+#define FILE2  "h5diff_basic2.h5"
+#define FILE3  "h5diff_types.h5"
+#define FILE4  "h5diff_dtypes.h5"
+#define FILE5  "h5diff_attr1.h5"
+#define FILE6  "h5diff_attr2.h5"
+#define FILE6a "h5diff_attr3.h5"
+#define FILE7  "h5diff_dset1.h5"
+#define FILE8  "h5diff_dset2.h5"
+#define FILE8A "h5diff_dset3.h5"
+#define FILE9  "h5diff_hyper1.h5"
+#define FILE10 "h5diff_hyper2.h5"
+#define FILE11 "h5diff_empty.h5"
+#define FILE12 "h5diff_links.h5"
+#define FILE13 "h5diff_softlinks.h5"
+#define FILE14 "h5diff_linked_softlink.h5"
+#define FILE15 "h5diff_extlink_src.h5"
+#define FILE16 "h5diff_extlink_trg.h5"
+#define FILE17 "h5diff_ext2softlink_src.h5"
+#define FILE18 "h5diff_ext2softlink_trg.h5"
+#define FILE19 "h5diff_dset_zero_dim_size1.h5"
+#define FILE20 "h5diff_dset_zero_dim_size2.h5"
+#define FILE21 "h5diff_dset_idx1.h5"
+#define FILE22 "h5diff_dset_idx2.h5"
+#define FILE23 "h5diff_onion_dset_1d.h5"
+#define FILE24 "h5diff_onion_objs.h5"
+#define FILE25 "h5diff_onion_dset_ext.h5"
+
 #define DANGLE_LINK_FILE1 "h5diff_danglelinks1.h5"
 #define DANGLE_LINK_FILE2 "h5diff_danglelinks2.h5"
 #define GRP_RECURSE_FILE1 "h5diff_grp_recurse1.h5"
@@ -111,6 +115,11 @@ size_t H5TOOLS_MALLOCSIZE = (128 * 1024 * 1024);
 #define SPACE1_DIM1 0
 #define SPACE1_DIM2 0
 
+/* For Onion VFD */
+#define ONION_TEST_FIXNAME_SIZE 1024
+#define ONION_TEST_PAGE_SIZE    (uint32_t)32
+#define ONE_DIM_SIZE            16
+
 /* Error macros */
 #define AT() HDprintf("ERROR at %s:%d in %s()...\n", __FILE__, __LINE__, __func__);
 #define PROGRAM_ERROR                                                                                        \
@@ -179,6 +188,11 @@ static void test_objs_nocomparables(const char *fname1, const char *fname2);
 static void test_objs_strings(const char *fname, const char *fname2);
 static void test_double_epsilon(const char *fname1, const char *fname2);
 
+/* Generate the files for testing Onion VFD */
+static int test_onion_1d_dset(const char *fname);
+static int test_onion_create_delete_objects(const char *fname);
+static int test_onion_dset_extension(const char *fname);
+
 /* called by test_attributes() and test_datasets() */
 static void write_attr_strings(hid_t loc_id, const char *dset_name, hid_t fid, int make_diffs);
 static void write_attr_in(hid_t loc_id, const char *dset_name, hid_t fid, int make_diffs);
@@ -298,9 +312,676 @@ main(void)
     /* double dataset and epsilion. HDFFV-10897 */
     test_double_epsilon(DIFF_EPS1, DIFF_EPS2);
 
+    /* Generate the files for testing Onion VFD */
+    test_onion_1d_dset(FILE23);
+    test_onion_create_delete_objects(FILE24);
+    test_onion_dset_extension(FILE25);
+
     return EXIT_SUCCESS;
 }
 
+/* Structure to collect the onion filepaths in one place. */
+struct onion_filepaths {
+    char *canon;
+    char *onion;
+    char *recovery;
+};
+
+/* Allocate and populate filepaths with h5_fixname'd strings as appropriate.
+ * Should be released with onion_filepaths_destroy() when done.
+ */
+static struct onion_filepaths *
+onion_filepaths_init(const char *basename)
+{
+    struct onion_filepaths *paths = NULL;
+
+    if (NULL == (paths = HDcalloc(1, sizeof(struct onion_filepaths))))
+        goto error;
+
+    if (NULL == (paths->canon = HDstrdup(basename)))
+        goto error;
+
+    if (NULL == (paths->onion = HDmalloc(sizeof(char) * ONION_TEST_FIXNAME_SIZE)))
+        goto error;
+    HDsnprintf(paths->onion, ONION_TEST_FIXNAME_SIZE, "%s.onion", paths->canon);
+
+    if (NULL == (paths->recovery = HDmalloc(sizeof(char) * ONION_TEST_FIXNAME_SIZE)))
+        goto error;
+    HDsnprintf(paths->recovery, ONION_TEST_FIXNAME_SIZE, "%s.onion.recovery", paths->canon);
+
+    return paths;
+
+error:
+    if (paths != NULL) {
+        HDfree(paths->canon);
+        HDfree(paths->onion);
+        HDfree(paths->recovery);
+        HDfree(paths);
+    }
+    return NULL;
+}
+
+static void
+onion_filepaths_destroy(struct onion_filepaths *s)
+{
+    if (s) {
+        HDfree(s->canon);
+        HDfree(s->onion);
+        HDfree(s->recovery);
+        HDfree(s);
+    }
+}
+
+static int
+test_onion_1d_dset(const char *fname)
+{
+    hid_t   file    = H5I_INVALID_HID;
+    hid_t   space   = H5I_INVALID_HID;
+    hid_t   dset    = H5I_INVALID_HID;
+    hid_t   dcpl    = H5I_INVALID_HID;
+    hsize_t dims[2] = {1, ONE_DIM_SIZE}, maxdims[2] = {1, ONE_DIM_SIZE};
+    int     wdata[1][ONE_DIM_SIZE], /* Write buffer */
+        fillval;
+
+    hid_t                   fapl_id    = H5I_INVALID_HID;
+    struct onion_filepaths *paths      = NULL;
+    H5FD_onion_fapl_info_t  onion_info = {
+        H5FD_ONION_FAPL_INFO_VERSION_CURR,
+        H5I_INVALID_HID,               /* backing_fapl_id  */
+        ONION_TEST_PAGE_SIZE,          /* page_size        */
+        H5FD_ONION_STORE_TARGET_ONION, /* store_target     */
+        H5FD_ONION_FAPL_INFO_REVISION_ID_LATEST,
+        0,               /* force_write_open */
+        0,               /* creation flags, was H5FD_ONION_FAPL_INFO_CREATE_FLAG_ENABLE_PAGE_ALIGNMENT */
+        "initial commit" /* comment          */
+    };
+    hid_t file_id = H5I_INVALID_HID;
+
+    /* Setup */
+    onion_info.backing_fapl_id = H5Pcreate(H5P_FILE_ACCESS);
+
+    if ((fapl_id = H5Pcreate(H5P_FILE_ACCESS)) < 0)
+        goto error;
+    if (H5Pset_fapl_onion(fapl_id, &onion_info) < 0)
+        goto error;
+
+    if ((paths = onion_filepaths_init(fname)) == NULL)
+        goto error;
+
+    /*----------------------------------------------------------------------
+     * Create the skeleton file (create the file without Onion VFD)
+     *----------------------------------------------------------------------
+     */
+    /* Initialize data */
+    for (int i = 0; i < ONE_DIM_SIZE; i++)
+        wdata[0][i] = i;
+
+    /* Create a new file using the default properties */
+    if ((file = H5Fcreate(paths->canon, H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT)) < 0)
+        goto error;
+
+    /* Create dataspace with unlimited dimensions */
+    if ((space = H5Screate_simple(2, dims, maxdims)) < 0)
+        goto error;
+
+    /* Create the dataset creation property list */
+    if ((dcpl = H5Pcreate(H5P_DATASET_CREATE)) < 0)
+        goto error;
+
+    /* Set the fill value for the dataset */
+    fillval = 99;
+    if (H5Pset_fill_value(dcpl, H5T_NATIVE_INT, &fillval) < 0)
+        goto error;
+
+    /* Set the allocation time to "early". This way we can be sure
+     * that reading from the dataset immediately after creation will
+     * return the fill value.
+     */
+    if (H5Pset_alloc_time(dcpl, H5D_ALLOC_TIME_EARLY) < 0)
+        goto error;
+
+    /* Create the dataset using the dataset creation property list */
+    if ((dset = H5Dcreate2(file, "DS1", H5T_STD_I32LE, space, H5P_DEFAULT, dcpl, H5P_DEFAULT)) < 0)
+        goto error;
+
+    /* Write the data to the dataset */
+    if (H5Dwrite(dset, H5T_NATIVE_INT, H5S_ALL, H5S_ALL, H5P_DEFAULT, wdata[0]) < 0)
+        goto error;
+
+    /* Close and release resources */
+    if (H5Pclose(dcpl) < 0)
+        goto error;
+    if (H5Dclose(dset) < 0)
+        goto error;
+    if (H5Sclose(space) < 0)
+        goto error;
+    if (H5Fclose(file) < 0)
+        goto error;
+
+    /*----------------------------------------------------------------------
+     * First revision: open the file with Onion VFD and change the data
+     *----------------------------------------------------------------------
+     */
+    if ((file_id = H5Fopen(paths->canon, H5F_ACC_RDWR, fapl_id)) < 0)
+        goto error;
+
+    if ((dset = H5Dopen2(file_id, "DS1", H5P_DEFAULT)) < 0)
+        goto error;
+
+    int dset_data[1][ONE_DIM_SIZE];
+    for (int i = 0; i < ONE_DIM_SIZE; i++)
+        dset_data[0][i] = i + ONE_DIM_SIZE;
+
+    if (H5Dwrite(dset, H5T_STD_I32LE, H5S_ALL, H5S_ALL, H5P_DEFAULT, dset_data) < 0)
+        goto error;
+
+    if (H5Dclose(dset) < 0)
+        goto error;
+    if (H5Fclose(file_id) < 0)
+        goto error;
+
+    /*----------------------------------------------------------------------
+     * Second revision: open the file with Onion VFD and change the data
+     *----------------------------------------------------------------------
+     */
+    if ((file_id = H5Fopen(paths->canon, H5F_ACC_RDWR, fapl_id)) < 0)
+        goto error;
+
+    if ((dset = H5Dopen2(file_id, "DS1", H5P_DEFAULT)) < 0)
+        goto error;
+
+    for (int i = 0; i < ONE_DIM_SIZE; i++)
+        dset_data[0][i] = i + 2048;
+
+    if (H5Dwrite(dset, H5T_STD_I32LE, H5S_ALL, H5S_ALL, H5P_DEFAULT, dset_data) < 0)
+        goto error;
+
+    /* CLEANUP */
+    if (H5Dclose(dset) < 0)
+        goto error;
+    dset = H5I_INVALID_HID;
+    if (H5Fclose(file_id) < 0)
+        goto error;
+    file_id = H5I_INVALID_HID;
+
+    /*----------------------------------------------------------------------
+     * Third revision: open the file with Onion VFD and change the data
+     *----------------------------------------------------------------------
+     */
+    if ((file_id = H5Fopen(paths->canon, H5F_ACC_RDWR, fapl_id)) < 0)
+        goto error;
+
+    if ((dset = H5Dopen2(file_id, "DS1", H5P_DEFAULT)) < 0)
+        goto error;
+
+    for (int i = 0; i < ONE_DIM_SIZE; i += 20)
+        dset_data[0][i] = i + 3072;
+
+    if (H5Dwrite(dset, H5T_STD_I32LE, H5S_ALL, H5S_ALL, H5P_DEFAULT, dset_data) < 0)
+        goto error;
+
+    /* CLEANUP */
+    if (H5Dclose(dset) < 0)
+        goto error;
+    if (H5Fclose(file_id) < 0)
+        goto error;
+    if (H5Pclose(fapl_id) < 0)
+        goto error;
+    if (H5Pclose(onion_info.backing_fapl_id) < 0)
+        goto error;
+
+    onion_filepaths_destroy(paths);
+
+    return 0;
+
+error:
+    H5E_BEGIN_TRY
+    {
+        H5Pclose(onion_info.backing_fapl_id);
+        H5Pclose(fapl_id);
+        H5Dclose(dset);
+        H5Sclose(space);
+        H5Fclose(file_id);
+    }
+    H5E_END_TRY;
+
+    return -1;
+} /* test_onion_1d_dset */
+
+static int
+test_onion_create_delete_objects(const char *fname)
+{
+    struct onion_filepaths *paths = NULL;
+
+    H5FD_onion_fapl_info_t onion_info = {
+        H5FD_ONION_FAPL_INFO_VERSION_CURR,
+        H5I_INVALID_HID,               /* backing_fapl_id  */
+        ONION_TEST_PAGE_SIZE,          /* page_size        */
+        H5FD_ONION_STORE_TARGET_ONION, /* store_target     */
+        H5FD_ONION_FAPL_INFO_REVISION_ID_LATEST,
+        0,               /* force_write_open */
+        0,               /* creation flags, was H5FD_ONION_FAPL_INFO_CREATE_FLAG_ENABLE_PAGE_ALIGNMENT */
+        "initial commit" /* comment          */
+    };
+
+    hid_t fapl_id       = H5I_INVALID_HID;
+    hid_t group_id      = H5I_INVALID_HID;
+    hid_t attr_space_id = H5I_INVALID_HID;
+    hid_t attr_id       = H5I_INVALID_HID;
+    hid_t file          = H5I_INVALID_HID;
+    hid_t space         = H5I_INVALID_HID;
+    hid_t dset          = H5I_INVALID_HID;
+    hid_t dcpl          = H5I_INVALID_HID;
+
+    hsize_t attr_dim[1] = {4};
+    hsize_t dims[2]     = {4, 4};
+    hsize_t maxdims[2]  = {H5S_UNLIMITED, H5S_UNLIMITED};
+    hsize_t chunk[2]    = {4, 4};
+    int     wdata[4][4]; /* Write buffer */
+
+    int fillval;
+
+    /* Set up */
+    if ((onion_info.backing_fapl_id = H5Pcreate(H5P_FILE_ACCESS)) < 0)
+        goto error;
+    if ((fapl_id = H5Pcreate(H5P_FILE_ACCESS)) < 0)
+        goto error;
+    if (H5Pset_fapl_onion(fapl_id, &onion_info) < 0)
+        goto error;
+
+    if ((paths = onion_filepaths_init(fname)) == NULL)
+        goto error;
+
+    /*----------------------------------------------------------------------
+     * Create the skeleton file (create the file without Onion VFD)
+     *----------------------------------------------------------------------
+     */
+
+    /*
+     * Initialize data.
+     */
+    for (int i = 0; i < 4; i++)
+        for (int j = 0; j < 4; j++)
+            wdata[i][j] = i + j;
+
+    /*
+     * Create a new file using the default properties.
+     */
+    if ((file = H5Fcreate(paths->canon, H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT)) < 0)
+        goto error;
+
+    /*
+     * Create dataspace with unlimited dimensions.
+     */
+    if ((space = H5Screate_simple(2, dims, maxdims)) < 0)
+        goto error;
+
+    /*
+     * Create the dataset creation property list, and set the chunk
+     * size.
+     */
+    if ((dcpl = H5Pcreate(H5P_DATASET_CREATE)) < 0)
+        goto error;
+    if (H5Pset_chunk(dcpl, 2, chunk) < 0)
+        goto error;
+
+    /*
+     * Set the fill value for the dataset.
+     */
+    fillval = 99;
+    if (H5Pset_fill_value(dcpl, H5T_NATIVE_INT, &fillval) < 0)
+        goto error;
+
+    /*
+     * Set the allocation time to "early".  This way we can be sure
+     * that reading from the dataset immediately after creation will
+     * return the fill value.
+     */
+    if (H5Pset_alloc_time(dcpl, H5D_ALLOC_TIME_EARLY) < 0)
+        goto error;
+
+    /*
+     * Create the dataset using the dataset creation property list.
+     */
+    if ((dset = H5Dcreate2(file, "DS1", H5T_STD_I32LE, space, H5P_DEFAULT, dcpl, H5P_DEFAULT)) < 0)
+        goto error;
+
+    /*
+     * Write the data to the dataset.
+     */
+    if (H5Dwrite(dset, H5T_NATIVE_INT, H5S_ALL, H5S_ALL, H5P_DEFAULT, wdata) < 0)
+        goto error;
+
+    if (H5Dclose(dset) < 0)
+        goto error;
+    if (H5Fclose(file) < 0)
+        goto error;
+
+    /*----------------------------------------------------------------------
+     * First revision: open the file with Onion VFD and add a dataset (DS2) to the file
+     *----------------------------------------------------------------------
+     */
+    if ((file = H5Fopen(paths->canon, H5F_ACC_RDWR, fapl_id)) < 0)
+        goto error;
+
+    /*
+     * Create the dataset using the dataset creation property list.
+     */
+    if ((dset = H5Dcreate2(file, "DS2", H5T_STD_I32LE, space, H5P_DEFAULT, dcpl, H5P_DEFAULT)) < 0)
+        goto error;
+
+    /*
+     * Write the data to the dataset.
+     */
+    if (H5Dwrite(dset, H5T_NATIVE_INT, H5S_ALL, H5S_ALL, H5P_DEFAULT, wdata) < 0)
+        goto error;
+
+    if (H5Dclose(dset) < 0)
+        goto error;
+    dset = H5I_INVALID_HID;
+    if (H5Fclose(file) < 0)
+        goto error;
+    file = H5I_INVALID_HID;
+
+    /*----------------------------------------------------------------------
+     * Second revision: open the file with Onion VFD and remove the dataset (DS2),
+     * which was added during the first revision.
+     *----------------------------------------------------------------------
+     */
+    if ((file = H5Fopen(paths->canon, H5F_ACC_RDWR, fapl_id)) < 0)
+        goto error;
+
+    if (H5Ldelete(file, "DS2", H5P_DEFAULT) < 0)
+        goto error;
+
+    if (H5Fclose(file) < 0)
+        goto error;
+    file = H5I_INVALID_HID;
+
+    /*----------------------------------------------------------------------
+     * Third revision: open the file with Onion VFD and add an attribute to the file
+     *----------------------------------------------------------------------
+     */
+    if ((file = H5Fopen(paths->canon, H5F_ACC_RDWR, fapl_id)) < 0)
+        goto error;
+
+    /* Create dataspace for attribute */
+    attr_space_id = H5Screate_simple(1, attr_dim, NULL);
+
+    if ((attr_id =
+             H5Acreate2(file, "file_attribute", H5T_STD_I32LE, attr_space_id, H5P_DEFAULT, H5P_DEFAULT)) < 0)
+        goto error;
+
+    if (H5Sclose(attr_space_id) < 0)
+        goto error;
+    if (H5Aclose(attr_id) < 0)
+        goto error;
+    if (H5Fclose(file) < 0)
+        goto error;
+    file = H5I_INVALID_HID;
+
+    /*----------------------------------------------------------------------
+     * Fourth revision: open the file with Onion VFD and delete the attribute
+     *----------------------------------------------------------------------
+     */
+    if ((file = H5Fopen(paths->canon, H5F_ACC_RDWR, fapl_id)) < 0)
+        goto error;
+
+    if (H5Adelete(file, "file_attribute") < 0)
+        goto error;
+
+    if (H5Fclose(file) < 0)
+        goto error;
+    file = H5I_INVALID_HID;
+
+    /*----------------------------------------------------------------------
+     * Fifth revision: open the file with Onion VFD and add a group to the file
+     *----------------------------------------------------------------------
+     */
+    if ((file = H5Fopen(paths->canon, H5F_ACC_RDWR, fapl_id)) < 0)
+        goto error;
+
+    if ((group_id = H5Gcreate2(file, "new_group", H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT)) < 0)
+        goto error;
+
+    if (H5Gclose(group_id) < 0)
+        goto error;
+    if (H5Fclose(file) < 0)
+        goto error;
+    file = H5I_INVALID_HID;
+
+    /*----------------------------------------------------------------------
+     * Sixth revision: open the file with Onion VFD and delete the newly added group
+     *----------------------------------------------------------------------
+     */
+    if ((file = H5Fopen(paths->canon, H5F_ACC_RDWR, fapl_id)) < 0)
+        goto error;
+
+    if (H5Ldelete(file, "new_group", H5P_DEFAULT) < 0)
+        goto error;
+
+    if (H5Fclose(file) < 0)
+        goto error;
+    file = H5I_INVALID_HID;
+
+    /*
+     * Close and release resources.
+     */
+    if (H5Pclose(onion_info.backing_fapl_id) < 0)
+        goto error;
+    if (H5Pclose(fapl_id) < 0)
+        goto error;
+    if (H5Pclose(dcpl) < 0)
+        goto error;
+    if (H5Sclose(space) < 0)
+        goto error;
+
+    onion_filepaths_destroy(paths);
+
+    return 0;
+error:
+
+    if (paths != NULL) {
+        HDremove(paths->canon);
+        HDremove(paths->onion);
+        HDremove(paths->recovery);
+        onion_filepaths_destroy(paths);
+    }
+
+    if (dset != H5I_INVALID_HID)
+        (void)H5Dclose(dset);
+    if (file != H5I_INVALID_HID)
+        (void)H5Fclose(file);
+    if (fapl_id != H5I_INVALID_HID)
+        (void)H5Pclose(fapl_id);
+    if (onion_info.backing_fapl_id != H5I_INVALID_HID)
+        H5Pclose(onion_info.backing_fapl_id);
+
+    return -1;
+} /* test_onion_create_delete_objects */
+
+static int
+test_onion_dset_extension(const char *fname)
+{
+    hid_t                   fapl_id    = H5I_INVALID_HID;
+    struct onion_filepaths *paths      = NULL;
+    H5FD_onion_fapl_info_t  onion_info = {
+        H5FD_ONION_FAPL_INFO_VERSION_CURR,
+        H5I_INVALID_HID,               /* backing_fapl_id  */
+        ONION_TEST_PAGE_SIZE,          /* page_size        */
+        H5FD_ONION_STORE_TARGET_ONION, /* store_target     */
+        H5FD_ONION_FAPL_INFO_REVISION_ID_LATEST,
+        0,               /* force_write_open */
+        0,               /* creation flags, was H5FD_ONION_FAPL_INFO_CREATE_FLAG_ENABLE_PAGE_ALIGNMENT */
+        "initial commit" /* comment          */
+    };
+    hid_t   file       = H5I_INVALID_HID;
+    hid_t   space      = H5I_INVALID_HID;
+    hid_t   dset_space = H5I_INVALID_HID;
+    hid_t   dset       = H5I_INVALID_HID;
+    hid_t   dcpl       = H5I_INVALID_HID;
+    hsize_t dims[2] = {4, 4}, maxdims[2] = {H5S_UNLIMITED, H5S_UNLIMITED}, chunk[2] = {4, 4};
+    hsize_t size[2], offset[2];
+    int     wdata[4][4], /* Write buffer */
+        fillval;
+
+    /* Setup */
+    if ((onion_info.backing_fapl_id = H5Pcreate(H5P_FILE_ACCESS)) < 0)
+        goto error;
+    if ((fapl_id = H5Pcreate(H5P_FILE_ACCESS)) < 0)
+        goto error;
+
+    if (H5Pset_fapl_onion(fapl_id, &onion_info) < 0)
+        goto error;
+
+    if ((paths = onion_filepaths_init(fname)) == NULL)
+        goto error;
+
+    /*----------------------------------------------------------------------
+     * Create the skeleton file (create the file without Onion VFD)
+     *----------------------------------------------------------------------
+     */
+    /* Initialize data */
+    for (int i = 0; i < 4; i++)
+        for (int j = 0; j < 4; j++)
+            wdata[i][j] = i + j;
+
+    /* Create a new file using the default properties */
+    if ((file = H5Fcreate(paths->canon, H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT)) < 0)
+        goto error;
+
+    /* Create dataspace with unlimited dimensions */
+    if ((space = H5Screate_simple(2, dims, maxdims)) < 0)
+        goto error;
+
+    /* Create the dataset creation property list, and set the chunk
+     * size.
+     */
+    if ((dcpl = H5Pcreate(H5P_DATASET_CREATE)) < 0)
+        goto error;
+    if (H5Pset_chunk(dcpl, 2, chunk) < 0)
+        goto error;
+
+    /* Set the fill value for the dataset */
+    fillval = 99;
+    if (H5Pset_fill_value(dcpl, H5T_NATIVE_INT, &fillval) < 0)
+        goto error;
+
+    /* Set the allocation time to "early". This way we can be sure
+     * that reading from the dataset immediately after creation will
+     * return the fill value.
+     */
+    if (H5Pset_alloc_time(dcpl, H5D_ALLOC_TIME_EARLY) < 0)
+        goto error;
+
+    /* Create the dataset using the dataset creation property list */
+    if ((dset = H5Dcreate2(file, "DS1", H5T_STD_I32LE, space, H5P_DEFAULT, dcpl, H5P_DEFAULT)) < 0)
+        goto error;
+
+    /* Write the data to the dataset */
+    if (H5Dwrite(dset, H5T_NATIVE_INT, H5S_ALL, H5S_ALL, H5P_DEFAULT, wdata) < 0)
+        goto error;
+
+    if (H5Dclose(dset) < 0)
+        goto error;
+    if (H5Fclose(file) < 0)
+        goto error;
+
+    /*----------------------------------------------------------------------
+     * First revision: open the file with Onion VFD and extend the dataset
+     *----------------------------------------------------------------------
+     */
+    if ((file = H5Fopen(paths->canon, H5F_ACC_RDWR, fapl_id)) < 0)
+        goto error;
+
+    /* Open the dataset */
+    if ((dset = H5Dopen2(file, "DS1", H5P_DEFAULT)) < 0)
+        goto error;
+
+    /* Extend the dataset and double the rows */
+    size[0] = 2 * dims[0];
+    size[1] = dims[1];
+    if (H5Dset_extent(dset, size) < 0)
+        goto error;
+
+    if ((dset_space = H5Dget_space(dset)) < 0)
+        goto error;
+
+    offset[0] = dims[0];
+    offset[1] = 0;
+    if (H5Sselect_hyperslab(dset_space, H5S_SELECT_SET, offset, NULL, dims, NULL) < 0)
+        goto error;
+
+    /* Write the data to the dataset. */
+    if (H5Dwrite(dset, H5T_NATIVE_INT, space, dset_space, H5P_DEFAULT, wdata) < 0)
+        goto error;
+
+    if (H5Sclose(dset_space) < 0)
+        goto error;
+
+    if (H5Dclose(dset) < 0)
+        goto error;
+    dset = H5I_INVALID_HID;
+    if (H5Fclose(file) < 0)
+        goto error;
+    file = H5I_INVALID_HID;
+
+    /*----------------------------------------------------------------------
+     * Second revision: open the file with Onion VFD and shrink the dataset
+     *----------------------------------------------------------------------
+     */
+    if ((file = H5Fopen(paths->canon, H5F_ACC_RDWR, fapl_id)) < 0)
+        goto error;
+
+    /* Open the dataset */
+    if ((dset = H5Dopen2(file, "DS1", H5P_DEFAULT)) < 0)
+        goto error;
+
+    /* Extend the dataset and shrink back the size */
+    if (H5Dset_extent(dset, dims) < 0)
+        goto error;
+
+    if (H5Dclose(dset) < 0)
+        goto error;
+    dset = H5I_INVALID_HID;
+    if (H5Fclose(file) < 0)
+        goto error;
+    file = H5I_INVALID_HID;
+
+    /* Close and release resources. */
+    if (H5Pclose(onion_info.backing_fapl_id) < 0)
+        goto error;
+    if (H5Pclose(fapl_id) < 0)
+        goto error;
+    if (H5Pclose(dcpl) < 0)
+        goto error;
+    if (H5Sclose(space) < 0)
+        goto error;
+
+    onion_filepaths_destroy(paths);
+
+    return 0;
+error:
+
+    if (paths != NULL) {
+        HDremove(paths->canon);
+        HDremove(paths->onion);
+        HDremove(paths->recovery);
+        onion_filepaths_destroy(paths);
+    }
+
+    H5E_BEGIN_TRY
+    {
+        H5Dclose(dset);
+        H5Fclose(file);
+        H5Pclose(fapl_id);
+        H5Pclose(onion_info.backing_fapl_id);
+    }
+    H5E_END_TRY;
+
+    return -1;
+} /* test_onion_dset_extension */
+
 /*-------------------------------------------------------------------------
  * Function: test_basic
  *
diff --git a/tools/test/h5diff/testfiles/h5diff_900.txt b/tools/test/h5diff/testfiles/h5diff_900.txt
new file mode 100644
index 0000000..eca7872
--- /dev/null
+++ b/tools/test/h5diff/testfiles/h5diff_900.txt
@@ -0,0 +1,12 @@
+
+file1     file2
+---------------------------------------
+    x      x    /              
+    x      x    /DS1           
+           x    /DS2           
+
+group  : </> and </>
+0 differences found
+dataset: </DS1> and </DS1>
+0 differences found
+EXIT CODE: 1
diff --git a/tools/test/h5diff/testfiles/h5diff_901.txt b/tools/test/h5diff/testfiles/h5diff_901.txt
new file mode 100644
index 0000000..eb1f7d9
--- /dev/null
+++ b/tools/test/h5diff/testfiles/h5diff_901.txt
@@ -0,0 +1,17 @@
+
+file1     file2
+---------------------------------------
+    x      x    /              
+    x      x    /DS1           
+
+group  : </> and </>
+0 differences found
+dataset: </DS1> and </DS1>
+Not comparable: </DS1> has rank 2, dimensions [4x4], max dimensions [18446744073709551615x18446744073709551615]
+and </DS1> has rank 2, dimensions [8x4], max dimensions [18446744073709551615x18446744073709551615]
+0 differences found
+--------------------------------
+Some objects are not comparable
+--------------------------------
+Use -c for a list of objects without details of differences.
+EXIT CODE: 0
diff --git a/tools/test/h5diff/testfiles/h5diff_902.txt b/tools/test/h5diff/testfiles/h5diff_902.txt
new file mode 100644
index 0000000..3863e16
--- /dev/null
+++ b/tools/test/h5diff/testfiles/h5diff_902.txt
@@ -0,0 +1,30 @@
+
+file1     file2
+---------------------------------------
+    x      x    /              
+    x      x    /DS1           
+
+group  : </> and </>
+0 differences found
+dataset: </DS1> and </DS1>
+size:           [1x16]           [1x16]
+position        DS1             DS1             difference          
+------------------------------------------------------------
+[ 0 0 ]          0               16              16             
+[ 0 1 ]          1               17              16             
+[ 0 2 ]          2               18              16             
+[ 0 3 ]          3               19              16             
+[ 0 4 ]          4               20              16             
+[ 0 5 ]          5               21              16             
+[ 0 6 ]          6               22              16             
+[ 0 7 ]          7               23              16             
+[ 0 8 ]          8               24              16             
+[ 0 9 ]          9               25              16             
+[ 0 10 ]          10              26              16             
+[ 0 11 ]          11              27              16             
+[ 0 12 ]          12              28              16             
+[ 0 13 ]          13              29              16             
+[ 0 14 ]          14              30              16             
+[ 0 15 ]          15              31              16             
+16 differences found
+EXIT CODE: 1
diff --git a/tools/test/h5diff/testfiles/h5diff_onion_dset_1d.h5 b/tools/test/h5diff/testfiles/h5diff_onion_dset_1d.h5
new file mode 100644
index 0000000..5e53fba
--- /dev/null
+++ b/tools/test/h5diff/testfiles/h5diff_onion_dset_1d.h5
diff --git a/tools/test/h5diff/testfiles/h5diff_onion_dset_1d.h5.onion b/tools/test/h5diff/testfiles/h5diff_onion_dset_1d.h5.onion
new file mode 100644
index 0000000..95893f2
--- /dev/null
+++ b/tools/test/h5diff/testfiles/h5diff_onion_dset_1d.h5.onion
diff --git a/tools/test/h5diff/testfiles/h5diff_onion_dset_ext.h5 b/tools/test/h5diff/testfiles/h5diff_onion_dset_ext.h5
new file mode 100644
index 0000000..369ace6
--- /dev/null
+++ b/tools/test/h5diff/testfiles/h5diff_onion_dset_ext.h5
diff --git a/tools/test/h5diff/testfiles/h5diff_onion_dset_ext.h5.onion b/tools/test/h5diff/testfiles/h5diff_onion_dset_ext.h5.onion
new file mode 100644
index 0000000..291f9b3
--- /dev/null
+++ b/tools/test/h5diff/testfiles/h5diff_onion_dset_ext.h5.onion
diff --git a/tools/test/h5diff/testfiles/h5diff_onion_objs.h5 b/tools/test/h5diff/testfiles/h5diff_onion_objs.h5
new file mode 100644
index 0000000..369ace6
--- /dev/null
+++ b/tools/test/h5diff/testfiles/h5diff_onion_objs.h5
diff --git a/tools/test/h5diff/testfiles/h5diff_onion_objs.h5.onion b/tools/test/h5diff/testfiles/h5diff_onion_objs.h5.onion
new file mode 100644
index 0000000..7811f83
--- /dev/null
+++ b/tools/test/h5diff/testfiles/h5diff_onion_objs.h5.onion
diff --git a/tools/test/h5diff/testh5diff.sh.in b/tools/test/h5diff/testh5diff.sh.in
index 6871463..4d232a7 100644
--- a/tools/test/h5diff/testh5diff.sh.in
+++ b/tools/test/h5diff/testh5diff.sh.in
@@ -124,6 +124,12 @@ $SRC_H5DIFF_TESTFILES/h5diff_strings1.h5
 $SRC_H5DIFF_TESTFILES/h5diff_strings2.h5
 $SRC_H5DIFF_TESTFILES/h5diff_eps1.h5
 $SRC_H5DIFF_TESTFILES/h5diff_eps2.h5
+$SRC_H5DIFF_TESTFILES/h5diff_onion_objs.h5
+$SRC_H5DIFF_TESTFILES/h5diff_onion_objs.h5.onion
+$SRC_H5DIFF_TESTFILES/h5diff_onion_dset_ext.h5
+$SRC_H5DIFF_TESTFILES/h5diff_onion_dset_ext.h5.onion
+$SRC_H5DIFF_TESTFILES/h5diff_onion_dset_1d.h5
+$SRC_H5DIFF_TESTFILES/h5diff_onion_dset_1d.h5.onion
 $SRC_TOOLS_TESTFILES/tvlstr.h5
 "
 
@@ -356,6 +362,9 @@ $SRC_H5DIFF_TESTFILES/h5diff_800.txt
 $SRC_H5DIFF_TESTFILES/h5diff_801.txt
 $SRC_H5DIFF_TESTFILES/h5diff_830.txt
 $SRC_H5DIFF_TESTFILES/h5diff_90.txt
+$SRC_H5DIFF_TESTFILES/h5diff_900.txt
+$SRC_H5DIFF_TESTFILES/h5diff_901.txt
+$SRC_H5DIFF_TESTFILES/h5diff_902.txt
 $SRC_H5DIFF_TESTFILES/h5diff_8625.txt
 $SRC_H5DIFF_TESTFILES/h5diff_8639.txt
 $SRC_H5DIFF_TESTFILES/h5diff_reg.txt
@@ -1214,6 +1223,15 @@ TOOLTEST h5diff_v1.txt -v 1_vds.h5 2_vds.h5
 TOOLTEST h5diff_v2.txt -r 1_vds.h5 2_vds.h5
 TOOLTEST h5diff_v3.txt -c 1_vds.h5 2_vds.h5
 
+# ##############################################################################
+# Onion VFD tests
+# ############################################################################## 
+# These tests won't pass under ph5diff
+if test -z "$pmode"; then
+    TOOLTEST h5diff_900.txt -r -v --vfd-name-1 onion --vfd-info-1 0 --vfd-name-2 onion --vfd-info-2 1 h5diff_onion_objs.h5 h5diff_onion_objs.h5
+    TOOLTEST h5diff_901.txt -r -v --vfd-name-1 onion --vfd-info-1 0 --vfd-name-2 onion --vfd-info-2 1 h5diff_onion_dset_ext.h5 h5diff_onion_dset_ext.h5
+    TOOLTEST h5diff_902.txt -r -v --vfd-name-1 onion --vfd-info-1 0 --vfd-name-2 onion --vfd-info-2 1 h5diff_onion_dset_1d.h5 h5diff_onion_dset_1d.h5
+fi
 
 # ##############################################################################
 # # END