Multi Dataset (#2120)

* Fix bug with cross platform compatibility of references within vlens.
No testing yet.

* Merge from multi_rd_wd_coll_io to a more recent branch from develop.
Untested, probably does not work yet.

* Committing clang-format changes

* Committing clang-format changes

* Fix many bugs in multi dataset branch.  Mostly works, some issues in
SWMR tests.

* Committing clang-format changes

* Disable test in swmr.c that was failing due to bug in HDF5 unrelated to
multi dataset.

* Committing clang-format changes

* Fixed fortran multi-dataset tests

* Fixed xlf errors

* Added benchmark code for multi-datasets

* loops over datasets

* added missing error arg.

* Added gnuplot formatting

* Jonathan Kim original MD benchmarking code

* updated MD benchmarking code

* code clean-up

* Only make files in feature test mode

* misc clean-up

* removed TEST_MDSET_NO_LAST_DSET_2ND_PROC option

* Committing clang-format changes

* Change multi dataset API to use arrays of individual parameters instead
of the parameter struct.

* Committing clang-format changes

* Update to new multi dataset Fortran API and tests. (#1724)

* Update to new multi dataset Fortran API and tests.
* Sync Fortran with develop.
* skipping h5pget_mpio_actual_io_mode_f for now

* Fixed issue with dxpl_id, changed to variable size dim. (#1770)

* Remove "is_coll_broken" field from H5D_io_info_t struct

* Committing clang-format changes

* Minor cleanup in multi dataset code.

* Committing clang-format changes

* Clean up in multi dataset code.

* Committing clang-format changes

* Committing clang-format changes

* Fix speeling

* Fix bug in parallel compression. Switch base_maddr in io_info to be a
union.

* Committing clang-format changes

* Implement selection I/O support with multi dataset.  Will be broken in
parallel until PR 1803 is merged to develop then the MDS branch.

* Committing clang-format changes

* Spelling

* Fix bug in multi dataset that could cause errors when only some of the
datasets in the multi dataset I/O used type conversion.

* Committing clang-format changes

* Integrate multi dataset APIs with VOL layer.  Add async versions of
multi dataset APIs.

* Committing clang-format changes

* Spelling fixes

* Fix bug in non-parallel HDF5 compilation.

* Committing clang-format changes

* Fix potential memory/free list error. Minor performance fix. Other minor
changes.

* Committing clang-format changes

* Fix memory leak with memory dataspace for I/O.

* Committing clang-format changes

* Fix stack variables too large.  Rename H5D_dset_info_t to
H5D_dset_io_info_t.

* Committing clang-format changes

* Remove mem_space_alloc field from H5D_dset_io_info_t.  Each function is
now responsible for freeing any spaces it adds to dset_info.

* Committing clang-format changes

* fixed _multi Fortran declaration

* Refactor various things in (mostly) the serial I/O code path to make
things more maintainable.

* Committing clang-format changes

* updated to array based, doxygen, and examples

* Reinstate H5D_chunk_map_t, stored (via pointer) inside
H5D_dset_io_info_t.

* Change from calloc to malloc for H5D_dset_io_info_t and H5D_chunk_map_t.
Switch temporary dset_infos to be local stack variables.

* Committing clang-format changes

* format cleanup

* format cleanup

* added coll and ind

* Modify all parallel I/O paths to take dset_info instead of assuming
dset_info[0].

* Committing clang-format changes

* fixed output

* Rework parallel I/O code to work properly with multi dataset in more
cases.  Fix bug in parallel compression.

* Committing clang-format changes

* Prevent H5D__multi_chunk_collective_io() from messing up collective opt
property for other datasets in I/O.  Other minor cleanup.  Add new test
case to t_pmulti_dset.c for H5FD_MPIO_INDIVIDUAL_IO, disabled for now
due to failures apparently unrelated to multi dataset code.

* Fix spelling

* Committing clang-format changes

* Replace N log N algorithm for finding chunk in
H5D__multi_chunk_collective_io() with O(N) algorithm, and remove use of
io_info->sel_pieces in that function.

* Committing clang-format changes

* Replace sel_pieces skiplist in io_info with flat array of pointers, use
qsort in I/O routine only when necessary.

* Committing clang-format changes

* Add new test case to mdset.c

* Committing clang-format changes

* Fix spelling

* Very minor fix in H5VL__native_dataset_read()

* Fix bug that could affect filtered parallel multi-dataset I/O.

* Add RM entries for H5Dread_multi(), H5Dread_multi_async(),
H5Dwrite_multi(), and H5Dwrite_multi_async()

* Unskip test in swmr.c

* Committing clang-format changes

* Eliminate H5D__pre_read and H5D__pre_write

* Remove examples/ph5mdsettest.c. Will fix and re-add as a test.

* Enable hyperslab combinations in mdset test

* Committing clang-format changes

* Clarify H5Dread/write_multi documentation.

* Fix bugs in multi-dataset I/O.  Expand serial multi dataset test.
Update macro in parallel multi dataset test.

* Committing clang-format changes

* Spelling

* Remove obsolete entry in bin/trace

* Rework type conversion buffer allocation. Only one buffer is shared
between datasets in mdset mode, and it is malloced instead of calloced.

* Committing clang-format changes

* Fix bug in error handling in H5D__read/write

* added multi-dataset fortran check with optional dataset creation id (#2150)

* removed dup. dll entry

* Address comments from code review.

* Remove spurious changes in H5Fmpi.c

* Fix issue with reading unallocated datasets in multi-dataset mode.
Address other comments from code review.

* Committing clang-format changes

* Delay chunk index lookup from io_init to mdio_init so it doesn't add
overhead to single dataset I/O.

* Committing clang-format changes

* Fix inappropriate use of piece_count

* updated copyright on new file, removed benchmark from testing dir.

Co-authored-by: github-actions <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: M. Scot Breitenfeld <brtnfld@hdfgroup.org>
Co-authored-by: Dana Robinson <43805+derobins@users.noreply.github.com>

1 files changed, 215 insertions, 38 deletions

diff --git a/src/H5VLcallback.c b/src/H5VLcallback.c
index 4fb0a63..8191d29 100644
--- a/src/H5VLcallback.c
+++ b/src/H5VLcallback.c
@@ -88,10 +88,12 @@ static void  *H5VL__dataset_create(void *obj, const H5VL_loc_params_t *loc_param
                                    hid_t dcpl_id, hid_t dapl_id, hid_t dxpl_id, void **req);
 static void  *H5VL__dataset_open(void *obj, const H5VL_loc_params_t *loc_params, const H5VL_class_t *cls,
                                  const char *name, hid_t dapl_id, hid_t dxpl_id, void **req);
-static herr_t H5VL__dataset_read(void *dset, const H5VL_class_t *cls, hid_t mem_type_id, hid_t mem_space_id,
-                                 hid_t file_space_id, hid_t dxpl_id, void *buf, void **req);
-static herr_t H5VL__dataset_write(void *obj, const H5VL_class_t *cls, hid_t mem_type_id, hid_t mem_space_id,
-                                  hid_t file_space_id, hid_t dxpl_id, const void *buf, void **req);
+static herr_t H5VL__dataset_read(size_t count, void *obj[], const H5VL_class_t *cls, hid_t mem_type_id[],
+                                 hid_t mem_space_id[], hid_t file_space_id[], hid_t dxpl_id, void *buf[],
+                                 void **req);
+static herr_t H5VL__dataset_write(size_t count, void *obj[], const H5VL_class_t *cls, hid_t mem_type_id[],
+                                  hid_t mem_space_id[], hid_t file_space_id[], hid_t dxpl_id,
+                                  const void *buf[], void **req);
 static herr_t H5VL__dataset_get(void *obj, const H5VL_class_t *cls, H5VL_dataset_get_args_t *args,
                                 hid_t dxpl_id, void **req);
 static herr_t H5VL__dataset_specific(void *obj, const H5VL_class_t *cls, H5VL_dataset_specific_args_t *args,
@@ -2020,9 +2022,9 @@ done:
 } /* end H5VLdataset_open() */
 
 /*-------------------------------------------------------------------------
- * Function:	H5VL__dataset_read
+ * Function:    H5VL__dataset_read
  *
- * Purpose:	Reads data from dataset through the VOL
+ * Purpose:     Reads data from dataset through the VOL
  *
  * Return:      Success:    Non-negative
  *              Failure:    Negative
@@ -2030,8 +2032,8 @@ done:
  *-------------------------------------------------------------------------
  */
 static herr_t
-H5VL__dataset_read(void *obj, const H5VL_class_t *cls, hid_t mem_type_id, hid_t mem_space_id,
-                   hid_t file_space_id, hid_t dxpl_id, void *buf, void **req)
+H5VL__dataset_read(size_t count, void *obj[], const H5VL_class_t *cls, hid_t mem_type_id[],
+                   hid_t mem_space_id[], hid_t file_space_id[], hid_t dxpl_id, void *buf[], void **req)
 {
     herr_t ret_value = SUCCEED; /* Return value */
 
@@ -2042,7 +2044,7 @@ H5VL__dataset_read(void *obj, const H5VL_class_t *cls, hid_t mem_type_id, hid_t
         HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL connector has no 'dataset read' method")
 
     /* Call the corresponding VOL callback */
-    if ((cls->dataset_cls.read)(obj, mem_type_id, mem_space_id, file_space_id, dxpl_id, buf, req) < 0)
+    if ((cls->dataset_cls.read)(count, obj, mem_type_id, mem_space_id, file_space_id, dxpl_id, buf, req) < 0)
         HGOTO_ERROR(H5E_VOL, H5E_READERROR, FAIL, "dataset read failed")
 
 done:
@@ -2050,6 +2052,54 @@ done:
 } /* end H5VL__dataset_read() */
 
 /*-------------------------------------------------------------------------
+ * Function:    H5VL_dataset_read_direct
+ *
+ * Purpose:     Reads data from dataset through the VOL.  This is like
+ *              H5VL_dataset_read, but takes an array of void * for the
+ *              objects and a class pointer instead of an array of
+ *              H5VL_object_t.  This allows us to avoid allocating and
+ *              copying an extra array (of H5VL_object_ts).
+ *
+ * Return:      Success:    Non-negative
+ *              Failure:    Negative
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5VL_dataset_read_direct(size_t count, void *obj[], H5VL_t *connector, hid_t mem_type_id[],
+                         hid_t mem_space_id[], hid_t file_space_id[], hid_t dxpl_id, void *buf[], void **req)
+{
+    hbool_t       vol_wrapper_set = FALSE; /* Whether the VOL object wrapping context was set up */
+    H5VL_object_t tmp_vol_obj;             /* Temporary VOL object for setting VOL wrapper */
+    herr_t        ret_value = SUCCEED;     /* Return value */
+
+    FUNC_ENTER_NOAPI(FAIL)
+
+    HDassert(obj);
+    HDassert(connector);
+
+    /* Set wrapper info in API context */
+    tmp_vol_obj.data      = obj[0];
+    tmp_vol_obj.connector = connector;
+    tmp_vol_obj.rc        = 1;
+    if (H5VL_set_vol_wrapper(&tmp_vol_obj) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTSET, FAIL, "can't set VOL wrapper info")
+    vol_wrapper_set = TRUE;
+
+    /* Call the corresponding internal VOL routine */
+    if (H5VL__dataset_read(count, obj, connector->cls, mem_type_id, mem_space_id, file_space_id, dxpl_id, buf,
+                           req) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_READERROR, FAIL, "dataset read failed")
+
+done:
+    /* Reset object wrapping info in API context */
+    if (vol_wrapper_set && H5VL_reset_vol_wrapper() < 0)
+        HDONE_ERROR(H5E_VOL, H5E_CANTRESET, FAIL, "can't reset VOL wrapper info")
+
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5VL_dataset_read_direct() */
+
+/*-------------------------------------------------------------------------
  * Function:	H5VL_dataset_read
  *
  * Purpose:	Reads data from dataset through the VOL
@@ -2060,21 +2110,44 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5VL_dataset_read(const H5VL_object_t *vol_obj, hid_t mem_type_id, hid_t mem_space_id, hid_t file_space_id,
-                  hid_t dxpl_id, void *buf, void **req)
+H5VL_dataset_read(size_t count, const H5VL_object_t *vol_obj[], hid_t mem_type_id[], hid_t mem_space_id[],
+                  hid_t file_space_id[], hid_t dxpl_id, void *buf[], void **req)
 {
-    hbool_t vol_wrapper_set = FALSE;   /* Whether the VOL object wrapping context was set up */
-    herr_t  ret_value       = SUCCEED; /* Return value */
+    hbool_t vol_wrapper_set = FALSE; /* Whether the VOL object wrapping context was set up */
+    void   *obj_local;               /* Local buffer for obj */
+    void  **obj = &obj_local;        /* Array of object pointers */
+    size_t  i;                       /* Local index variable */
+    herr_t  ret_value = SUCCEED;     /* Return value */
 
     FUNC_ENTER_NOAPI(FAIL)
 
+    HDassert(vol_obj);
+    HDassert(vol_obj[0]);
+
     /* Set wrapper info in API context */
-    if (H5VL_set_vol_wrapper(vol_obj) < 0)
+    if (H5VL_set_vol_wrapper(vol_obj[0]) < 0)
         HGOTO_ERROR(H5E_VOL, H5E_CANTSET, FAIL, "can't set VOL wrapper info")
     vol_wrapper_set = TRUE;
 
+    /* Allocate obj array if necessary */
+    if (count > 1)
+        if (NULL == (obj = (void **)H5MM_malloc(count * sizeof(void *))))
+            HGOTO_ERROR(H5E_VOL, H5E_CANTALLOC, FAIL, "can't allocate space for object array")
+
+    /* Build obj array */
+    for (i = 0; i < count; i++) {
+        /* Get the object */
+        obj[i] = vol_obj[i]->data;
+
+        /* Make sure the class matches */
+        if (vol_obj[i]->connector->cls->value != vol_obj[0]->connector->cls->value)
+            HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL,
+                        "datasets are accessed through different VOL connectors and can't be used in the "
+                        "same I/O call")
+    }
+
     /* Call the corresponding internal VOL routine */
-    if (H5VL__dataset_read(vol_obj->data, vol_obj->connector->cls, mem_type_id, mem_space_id, file_space_id,
+    if (H5VL__dataset_read(count, obj, vol_obj[0]->connector->cls, mem_type_id, mem_space_id, file_space_id,
                            dxpl_id, buf, req) < 0)
         HGOTO_ERROR(H5E_VOL, H5E_READERROR, FAIL, "dataset read failed")
 
@@ -2083,6 +2156,10 @@ done:
     if (vol_wrapper_set && H5VL_reset_vol_wrapper() < 0)
         HDONE_ERROR(H5E_VOL, H5E_CANTRESET, FAIL, "can't reset VOL wrapper info")
 
+    /* Free memory */
+    if (obj != &obj_local)
+        H5MM_free(obj);
+
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5VL_dataset_read() */
 
@@ -2097,24 +2174,36 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5VLdataset_read(void *obj, hid_t connector_id, hid_t mem_type_id, hid_t mem_space_id, hid_t file_space_id,
-                 hid_t dxpl_id, void *buf, void **req /*out*/)
+H5VLdataset_read(size_t count, void *obj[], hid_t connector_id, hid_t mem_type_id[], hid_t mem_space_id[],
+                 hid_t file_space_id[], hid_t dxpl_id, void *buf[], void **req /*out*/)
 {
     H5VL_class_t *cls;                 /* VOL connector's class struct */
+    size_t        i;                   /* Local index variable */
     herr_t        ret_value = SUCCEED; /* Return value */
 
     FUNC_ENTER_API_NOINIT
-    H5TRACE8("e", "*xiiiii*xx", obj, connector_id, mem_type_id, mem_space_id, file_space_id, dxpl_id, buf,
-             req);
+    H5TRACE9("e", "z**xi*i*i*ii**xx", count, obj, connector_id, mem_type_id, mem_space_id, file_space_id,
+             dxpl_id, buf, req);
 
     /* Check args and get class pointer */
     if (NULL == obj)
-        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "invalid object")
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "obj array not provided")
+    for (i = 1; i < count; i++)
+        if (NULL == obj[i])
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "invalid object")
+    if (NULL == mem_type_id)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "mem_type_id array not provided")
+    if (NULL == mem_space_id)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "mem_space_id array not provided")
+    if (NULL == file_space_id)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "file_space_id array not provided")
+    if (NULL == buf)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "buf array not provided")
     if (NULL == (cls = (H5VL_class_t *)H5I_object_verify(connector_id, H5I_VOL)))
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a VOL connector ID")
 
     /* Call the corresponding internal VOL routine */
-    if (H5VL__dataset_read(obj, cls, mem_type_id, mem_space_id, file_space_id, dxpl_id, buf, req) < 0)
+    if (H5VL__dataset_read(count, obj, cls, mem_type_id, mem_space_id, file_space_id, dxpl_id, buf, req) < 0)
         HGOTO_ERROR(H5E_VOL, H5E_CANTINIT, FAIL, "unable to read dataset")
 
 done:
@@ -2122,9 +2211,9 @@ done:
 } /* end H5VLdataset_read() */
 
 /*-------------------------------------------------------------------------
- * Function:	H5VL__dataset_write
+ * Function:    H5VL__dataset_write
  *
- * Purpose:	Writes data from dataset through the VOL
+ * Purpose:     Writes data from dataset through the VOL
  *
  * Return:      Success:    Non-negative
  *              Failure:    Negative
@@ -2132,8 +2221,8 @@ done:
  *-------------------------------------------------------------------------
  */
 static herr_t
-H5VL__dataset_write(void *obj, const H5VL_class_t *cls, hid_t mem_type_id, hid_t mem_space_id,
-                    hid_t file_space_id, hid_t dxpl_id, const void *buf, void **req)
+H5VL__dataset_write(size_t count, void *obj[], const H5VL_class_t *cls, hid_t mem_type_id[],
+                    hid_t mem_space_id[], hid_t file_space_id[], hid_t dxpl_id, const void *buf[], void **req)
 {
     herr_t ret_value = SUCCEED; /* Return value */
 
@@ -2144,7 +2233,7 @@ H5VL__dataset_write(void *obj, const H5VL_class_t *cls, hid_t mem_type_id, hid_t
         HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL connector has no 'dataset write' method")
 
     /* Call the corresponding VOL callback */
-    if ((cls->dataset_cls.write)(obj, mem_type_id, mem_space_id, file_space_id, dxpl_id, buf, req) < 0)
+    if ((cls->dataset_cls.write)(count, obj, mem_type_id, mem_space_id, file_space_id, dxpl_id, buf, req) < 0)
         HGOTO_ERROR(H5E_VOL, H5E_WRITEERROR, FAIL, "dataset write failed")
 
 done:
@@ -2152,6 +2241,55 @@ done:
 } /* end H5VL__dataset_write() */
 
 /*-------------------------------------------------------------------------
+ * Function:    H5VL_dataset_write_direct
+ *
+ * Purpose:     Writes data from dataset through the VOL.  This is like
+ *              H5VL_dataset_write, but takes an array of void * for the
+ *              objects and a class pointer instead of an array of
+ *              H5VL_object_t.  This allows us to avoid allocating and
+ *              copying an extra array (of H5VL_object_ts).
+ *
+ * Return:      Success:    Non-negative
+ *              Failure:    Negative
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5VL_dataset_write_direct(size_t count, void *obj[], H5VL_t *connector, hid_t mem_type_id[],
+                          hid_t mem_space_id[], hid_t file_space_id[], hid_t dxpl_id, const void *buf[],
+                          void **req)
+{
+    hbool_t       vol_wrapper_set = FALSE; /* Whether the VOL object wrapping context was set up */
+    H5VL_object_t tmp_vol_obj;             /* Temporary VOL object for setting VOL wrapper */
+    herr_t        ret_value = SUCCEED;     /* Return value */
+
+    FUNC_ENTER_NOAPI(FAIL)
+
+    HDassert(obj);
+    HDassert(connector);
+
+    /* Set wrapper info in API context */
+    tmp_vol_obj.data      = obj[0];
+    tmp_vol_obj.connector = connector;
+    tmp_vol_obj.rc        = 1;
+    if (H5VL_set_vol_wrapper(&tmp_vol_obj) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTSET, FAIL, "can't set VOL wrapper info")
+    vol_wrapper_set = TRUE;
+
+    /* Call the corresponding internal VOL routine */
+    if (H5VL__dataset_write(count, obj, connector->cls, mem_type_id, mem_space_id, file_space_id, dxpl_id,
+                            buf, req) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_WRITEERROR, FAIL, "dataset write failed")
+
+done:
+    /* Reset object wrapping info in API context */
+    if (vol_wrapper_set && H5VL_reset_vol_wrapper() < 0)
+        HDONE_ERROR(H5E_VOL, H5E_CANTRESET, FAIL, "can't reset VOL wrapper info")
+
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5VL_dataset_write_direct() */
+
+/*-------------------------------------------------------------------------
  * Function:	H5VL_dataset_write
  *
  * Purpose:	Writes data from dataset through the VOL
@@ -2162,21 +2300,44 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5VL_dataset_write(const H5VL_object_t *vol_obj, hid_t mem_type_id, hid_t mem_space_id, hid_t file_space_id,
-                   hid_t dxpl_id, const void *buf, void **req)
+H5VL_dataset_write(size_t count, const H5VL_object_t *vol_obj[], hid_t mem_type_id[], hid_t mem_space_id[],
+                   hid_t file_space_id[], hid_t dxpl_id, const void *buf[], void **req)
 {
-    hbool_t vol_wrapper_set = FALSE;   /* Whether the VOL object wrapping context was set up */
-    herr_t  ret_value       = SUCCEED; /* Return value */
+    hbool_t vol_wrapper_set = FALSE; /* Whether the VOL object wrapping context was set up */
+    void   *obj_local;               /* Local buffer for obj */
+    void  **obj = &obj_local;        /* Array of object pointers */
+    size_t  i;                       /* Local index variable */
+    herr_t  ret_value = SUCCEED;     /* Return value */
 
     FUNC_ENTER_NOAPI(FAIL)
 
+    HDassert(vol_obj);
+    HDassert(vol_obj[0]);
+
     /* Set wrapper info in API context */
-    if (H5VL_set_vol_wrapper(vol_obj) < 0)
+    if (H5VL_set_vol_wrapper(vol_obj[0]) < 0)
         HGOTO_ERROR(H5E_VOL, H5E_CANTSET, FAIL, "can't set VOL wrapper info")
     vol_wrapper_set = TRUE;
 
+    /* Allocate obj array if necessary */
+    if (count > 1)
+        if (NULL == (obj = (void **)H5MM_malloc(count * sizeof(void *))))
+            HGOTO_ERROR(H5E_VOL, H5E_CANTALLOC, FAIL, "can't allocate space for object array")
+
+    /* Build obj array */
+    for (i = 0; i < count; i++) {
+        /* Get the object */
+        obj[i] = vol_obj[i]->data;
+
+        /* Make sure the class matches */
+        if (vol_obj[i]->connector->cls->value != vol_obj[0]->connector->cls->value)
+            HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL,
+                        "datasets are accessed through different VOL connectors and can't be used in the "
+                        "same I/O call")
+    }
+
     /* Call the corresponding internal VOL routine */
-    if (H5VL__dataset_write(vol_obj->data, vol_obj->connector->cls, mem_type_id, mem_space_id, file_space_id,
+    if (H5VL__dataset_write(count, obj, vol_obj[0]->connector->cls, mem_type_id, mem_space_id, file_space_id,
                             dxpl_id, buf, req) < 0)
         HGOTO_ERROR(H5E_VOL, H5E_WRITEERROR, FAIL, "dataset write failed")
 
@@ -2185,6 +2346,10 @@ done:
     if (vol_wrapper_set && H5VL_reset_vol_wrapper() < 0)
         HDONE_ERROR(H5E_VOL, H5E_CANTRESET, FAIL, "can't reset VOL wrapper info")
 
+    /* Free memory */
+    if (obj != &obj_local)
+        H5MM_free(obj);
+
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5VL_dataset_write() */
 
@@ -2199,24 +2364,36 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5VLdataset_write(void *obj, hid_t connector_id, hid_t mem_type_id, hid_t mem_space_id, hid_t file_space_id,
-                  hid_t dxpl_id, const void *buf, void **req /*out*/)
+H5VLdataset_write(size_t count, void *obj[], hid_t connector_id, hid_t mem_type_id[], hid_t mem_space_id[],
+                  hid_t file_space_id[], hid_t dxpl_id, const void *buf[], void **req /*out*/)
 {
     H5VL_class_t *cls;                 /* VOL connector's class struct */
+    size_t        i;                   /* Local index variable */
     herr_t        ret_value = SUCCEED; /* Return value */
 
     FUNC_ENTER_API_NOINIT
-    H5TRACE8("e", "*xiiiii*xx", obj, connector_id, mem_type_id, mem_space_id, file_space_id, dxpl_id, buf,
-             req);
+    H5TRACE9("e", "z**xi*i*i*ii**xx", count, obj, connector_id, mem_type_id, mem_space_id, file_space_id,
+             dxpl_id, buf, req);
 
     /* Check args and get class pointer */
     if (NULL == obj)
-        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "invalid object")
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "obj array not provided")
+    for (i = 1; i < count; i++)
+        if (NULL == obj[i])
+            HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "invalid object")
+    if (NULL == mem_type_id)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "mem_type_id array not provided")
+    if (NULL == mem_space_id)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "mem_space_id array not provided")
+    if (NULL == file_space_id)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "file_space_id array not provided")
+    if (NULL == buf)
+        HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "buf array not provided")
     if (NULL == (cls = (H5VL_class_t *)H5I_object_verify(connector_id, H5I_VOL)))
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a VOL connector ID")
 
     /* Call the corresponding internal VOL routine */
-    if (H5VL__dataset_write(obj, cls, mem_type_id, mem_space_id, file_space_id, dxpl_id, buf, req) < 0)
+    if (H5VL__dataset_write(count, obj, cls, mem_type_id, mem_space_id, file_space_id, dxpl_id, buf, req) < 0)
         HGOTO_ERROR(H5E_VOL, H5E_CANTINIT, FAIL, "unable to write dataset")
 
 done: