Combo set of async and other changes (#161)

* Update API tracing for new H5VL_request_status_t typedef

* Finish converting internal event set operations to use list iterator callbacks, instead of directly accessing the list structure

* Add H5VL_REQUEST_GET_ERR_STACK operation to request subclass, for retrieving a copy of the error stack for a failed asynchronous operation

* Remove 'canceled' event status from Java constants

* Be safer about releasing resources when inserting a newly opened/created object or file into an event set

* Remove H5EStest, add H5ES_WAIT_NONE for 0 timeout, and revise parameters to H5ESwait, to make it more "aggregate".

* Remove H5ES_STATUS_CANCELED from Java wrappers also

* Apply patch for dynamically registering optional VOL operations

* (a) Add async APIs for H5O module as listed in jira issue ID-283.
(b) Remove verification of name parameter in async related routines for H55A and H5L modules
    because it is checked in H5VL_setup* routine.
(c) Modify h5dump expected output due to the async changes.

* Corrections based on PR feedback.

* Further changes to make based on PR feedback.

* Remove H5Dwait & H5Fwait (moved to the async connector).  Added H5atclose
routine.  Updated 'optional op' operations.

* Fix missed merge marker, and reformatted line

* Update API tracing infrastructure for H5atclose callback

* Clean up some warnings

* Normalize against develop branch

* Correct level of indirection

* Add doxygen info for H5is_library_terminating and regression tests for it and H5atclose

* Relocate prototype (and doxygen info) for H5Aclose

* Align w/changes on develop

* Move group package initialization code to H5Gint.c, and update tracing macros

* Change non-static function declarations to be static

* Correct GCC diagnostic macro

* Ensure that H5TSpublic.h header gets installed (#129)

* Finish moving API routines that invoke VOL framework to main source files.

* Fix position of H5Fmount and H5Funmount

* Add 'wrapper' versions of async calls, to allow language wrappers and layers on top of HDF5 to pass in their application information.

* Add wrappers for dynamically registered optional operations

* Fix typo

* Update doxygen comment for H5atclose with additional detail.

* Add H5VL\*_vararg versions of H5VL routines that use va_list parameters

* Implement and test H5S_BLOCK

* Switch H5Aexists\*_async and H5Lexists\*_async to use flag to return status, instead of return value.  Make the corresponding changes through most of the v1 and v2 B-tree code.  Clean up warnings in H5public.h and cmpd_dtransform.c.

* Add H5Iregister_future routine and tests.

* Correct return value for H5Lexists_async

* Add H5_DLL macro to public H5ES API routines

* Update supported -> flags parameter for introspect_query callback

* Remove my email address.  Update passthrough VOL connector ID.

* Fix comment for post_open_api_common

* Remove unused non-blocking VOL connector

* Minor cleanup in async branch in preparation for merge to develop

* Update CMake and the Autotools to use the new pass-through VOL ID

* Finish another iteration on public H5ES routines, along with running the code reformatter

* Another round of reformatting

* Fix for SWMR daily test failures (#160)

The H5I_register_using_existing_id() call did not initialize the future
ID callbacks, causing the library to segfault when it tried to
resolve those function pointers.

* Added selective async APIs (#150)

* Added selective async APIs

Description:
    Added the following APIs:
        H5Ropen_attr_async
        H5Ropen_object_async
        H5Ropen_region_async

        H5Mcreate_async
        H5Mopen_async
        H5Mput_async
        H5Mget_async
        H5Mclose_async

        H5Tcommit_async
        H5Topen_async
        H5Tcopy_async
        H5Tclose_async
    - Updated an expected output file to include a new internal function
      in the error stack for the failure case.

* Updated async APIs per reviews, including removing async version of
H5Tcopy.

* Removed statements that were added by mistake in the previous commit.

* Fix compile issues in H5M and warnings elsewhere

* Reformat code

* Brings VOL_LIST changes from develop. (#163)

* Remove H5Dwait and H5Fwait calls, which were incorrectly brought back in

* Tiny cleanup of H5Lcreate_hard_async

* Run source formatter

* Allow for canceled operation in wait_cb

* Attempt to fix switch on string value

* Re-run source formatter

* Add H5S_BLOCK testfile to CMake clean target

* Add H5Pset_vol_async API routine and 'get_cap_flags' VOL introspection callback

* Clean up warnings

* Add H5P(set\|get)_vol_implicit_async API routines to allow \/ disallow implicit asynchronous operations (default is disallowed)

* Run formatting script

* Remove H5VL_REQUEST_WAIT\*

* Warning cleanup

* Eliminate strdup()s on statically allocated strings

* Warning cleanup

* Split H5VLrestore_lib_state into H5VLstart_lib_state and H5VLrestore_lib_state, and rename H5VLreset_lib_state to H5VLfinish_lib_state.

* Duplicate strings when building err_info to return to applicatin

* Move connector author routines into seperate header files, all included in the new hdf5dev.h header

* Run bin/trace to add TRACE macros

* Allow H5ES_NONE as a valid, but no-op, parameter to all H5ES API routines that accept an event set ID

* Clean up formatting

* Remove H5Pset/get_vol_implicit_async

* Clean up warning

* Remove H5Pget_vol_async and replace with more generic H5Pget_vol_cap_flags

* Clean up warnings

* Add H5ESfree_err_info convenience routine

* Fix typo

* Correct matching for cached VOL plugins

* Add developer header file

* Update for C99 compatibility

* Add missing trace macro

* Stop clang-format from messing with the trace macros.  Don't set up VOL wrappers for 'infrastructure' objects like requests and blobs

* Fix warning about formatting a directory

* Clean up formatting for H5E_BEGIN_TRY / H5E_END_TRY

* Reduce scope of H5ES__close

* Enable CMake checks for various types on MacOS

* Clean up properly when H5CX_retrieve_state() fails.  Also clean up many compiler warnings.

* Committing clang-format changes

* Merge from develop

* Fix mis-placed assert

* Remove commented-out code

* Re-add macro for unsetenv on Windows (I think it accidentally was merged out)

* Strengthen sanity check from error report to assertion

* Committing clang-format changes

* Add units to the comments for a few fields

* Switch 'get execution time' operation for async request tokens to be an optional operation and query if connector supports operation before retrieving it.

* Committing clang-format changes

* Remove H5ESget_time_estimate

* Committing clang-format changes

* Create developer header for datatype routines and move type conversion register/unregister routines there.

* Simplify internal H5VL_setup_name_args and H5VL_setup_idx_args routines

* Add H5VLlink_optional_op, allowing dynamicly registered optional operations for the link VOL subclass, also added H5VL_loc_params argument to the link 'optional' callback to allow them to work correctly.

* Run bin/format_source on current code

* Add H5VLobject_optional_op, allowing dynamicly registered optional operations for the object VOL subclass, also added H5VL_loc_params argument to the object 'optional' callback to allow them to work correctly.

* Run bin/format_source on current code

* Committing clang-format changes

* Revert "Switch 'get execution time' operation for async request tokens to be an optional operation and query if connector supports operation before retrieving it."

This reverts commit 5ac92014da2682bdba62d7a2524b8d90e38f6b19.

* Committing clang-format changes

* Convert attribute 'get' operation to use struct-of-tagged-union pattern for VOL callback arguments, instead of using varargs.

* Update tracing macros

* Convert attribute 'specific' operation to use struct-of-tagged-union pattern for VOL callback arguments, instead of using varargs.

* Convert dataset 'get' and 'specific' operations to use struct-of-tagged-union pattern for VOL callback arguments, instead of using varargs.  Also, minor tweaks to attribute 'get' and 'specific' operation parameters.

* Convert datatype 'get' and 'specific' operations to use struct-of-tagged-union pattern for VOL callback arguments, instead of using varargs.  Also, minor tweaks to H5O_refresh_metadata arguments.

* Reduce warnings

* Reduce warnings

* Track change to datatype 'get' callback

* Fix bug with file pointer getting invalidated when object closed

* Reformat source

* Convert file and group VOL classes 'get' and 'specific' operations to use
struct-of-tagged-union pattern for VOL callback arguments, instead of using
varargs.  Also small cleanup to the attribute get name operation.  Also moved
'mount' and 'unmount' operations to be group specific operations, instead of
file specific, to better align with their behavior (mounted files are on
groups, so a group is what is operated on).

* Remove remainder of merge conflict marking

* Convert link VOL class 'create' operations to use struct-of-tagged-union pattern for VOL callback arguments, instead of using varargs.

* Remove some unused local variables

* Convert link VOL class 'get' operations to use struct-of-tagged-union pattern for VOL callback arguments, instead of using varargs.  Also refactor 'get name by idx' routines to return actual length of name with a parameter instead of the return value, and move some callback context structs for the link interface from the private header file into the source code module, to reduce their visibility scope.

* Update tracing macros

* Convert link VOL class 'specific' operations to use struct-of-tagged-union pattern for VOL callback arguments, instead of using varargs.

* Convert object VOL class 'get' operations to use struct-of-tagged-union pattern for VOL callback arguments, instead of using varargs.

* Convert object VOL class 'specific' operations to use struct-of-tagged-union pattern for VOL callback arguments, instead of using varargs.  Also refactor H5G_loc_exists, et al, to return 'exists' flag in a parameter and errors with the function return value, instead of overloading both into the return value.  And, corrected logic error in test/links.c around non-existant objects in a file.

* Convert request VOL class 'specific' operations to use struct-of-tagged-union pattern for VOL callback arguments, instead of using varargs.

* Convert blob VOL class 'specific' operations to use struct-of-tagged-union pattern for VOL callback arguments, instead of using varargs.  Also removes the H5VL_BLOB_GETSIZE operation, as it's unused in the library and the blob ID size for a container is now returned with H5VL_FILE_GET_CONT_INFO.

* Add 'const' to several parameters that are only queried.

* Convert all VOL classes' 'optional' operations to use struct-of-tagged-union pattern for VOL callback arguments, instead of using varargs.  Convert several 'get' routines to return the length of an array in a parameter instead of combining it into the return value.  Move several routines to be in less public namespace.  Correct direct_chunk test to verify that parameters aren't modified on error.

* Switch get/specific/optional VOL callback argument structures to be 'async-friendly'.  Also other minor cleanups and bug-fixes.

* Add H5Pset_dataset_io_hyperslab_selection / H5S_PLIST feature, to allow skipping H5Dget_space + H5Sselect_hyperslab for async operation

* Add dynamic optional operations for request objects

* Update dynamic operation test for optional request operations

* Update a comment for an operation argument

* Run trace and format_source scripts

* Committing clang-format changes

* Committing clang-format changes

Co-authored-by: vchoi <vchoi@jelly.ad.hdfgroup.org>
Co-authored-by: vchoi-hdfgroup <55293060+vchoi-hdfgroup@users.noreply.github.com>
Co-authored-by: jhendersonHDF <jhenderson@hdfgroup.org>
Co-authored-by: Dana Robinson <derobins@hdfgroup.org>
Co-authored-by: Dana Robinson <43805+derobins@users.noreply.github.com>
Co-authored-by: bmribler <39579120+bmribler@users.noreply.github.com>
Co-authored-by: github-actions <41898282+github-actions[bot]@users.noreply.github.com>

1 files changed, 300 insertions, 150 deletions

diff --git a/src/H5O.c b/src/H5O.c
index 4876bb0..a1c9c2d 100644
--- a/src/H5O.c
+++ b/src/H5O.c
@@ -70,7 +70,7 @@ static herr_t H5O__copy_api_common(hid_t src_loc_id, const char *src_name, hid_t
                                    H5VL_object_t **_vol_obj_ptr);
 static herr_t H5O__flush_api_common(hid_t obj_id, void **token_ptr, H5VL_object_t **_vol_obj_ptr);
 static herr_t H5O__refresh_api_common(hid_t oid, void **token_ptr, H5VL_object_t **_vol_obj_ptr);
-static htri_t H5O__close_check_common(hid_t object_id);
+static htri_t H5O__close_check_type(hid_t object_id);
 
 /*********************/
 /* Package Variables */
@@ -112,7 +112,7 @@ H5O__open_api_common(hid_t loc_id, const char *name, hid_t lapl_id, void **token
 
     /* name is checked in this H5VL_setup_name_args() */
     /* Set up object access arguments */
-    if (H5VL_setup_name_args(loc_id, name, H5P_CLS_LACC, FALSE, lapl_id, vol_obj_ptr, &loc_params) < 0)
+    if (H5VL_setup_name_args(loc_id, name, FALSE, lapl_id, vol_obj_ptr, &loc_params) < 0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTSET, H5I_INVALID_HID, "can't set object access arguments")
 
     /* Open the object */
@@ -239,7 +239,7 @@ H5O__open_by_idx_api_common(hid_t loc_id, const char *group_name, H5_index_t idx
     /* Check args */
     /* group_name, idx_type, order are checked in H5VL_setup_idx-args() */
     /* Set up object access arguments */
-    if (H5VL_setup_idx_args(loc_id, group_name, idx_type, order, n, H5P_CLS_LACC, FALSE, lapl_id, vol_obj_ptr,
+    if (H5VL_setup_idx_args(loc_id, group_name, idx_type, order, n, FALSE, lapl_id, vol_obj_ptr,
                             &loc_params) < 0)
         HGOTO_ERROR(H5E_LINK, H5E_CANTSET, H5I_INVALID_HID, "can't set object access arguments")
 
@@ -448,6 +448,7 @@ H5O__copy_api_common(hid_t src_loc_id, const char *src_name, hid_t dst_loc_id, c
     /* Set the LCPL for the API context */
     H5CX_set_lcpl(lcpl_id);
 
+    /* Setup and check args */
     if (H5VL_setup_loc_args(src_loc_id, &vol_obj1, &loc_params1) < 0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTSET, FAIL, "can't set object access arguments")
 
@@ -616,19 +617,23 @@ H5O__flush_api_common(hid_t obj_id, void **token_ptr, H5VL_object_t **_vol_obj_p
     H5VL_object_t * tmp_vol_obj = NULL; /* Object for loc_id */
     H5VL_object_t **vol_obj_ptr =
         (_vol_obj_ptr ? _vol_obj_ptr : &tmp_vol_obj); /* Ptr to object ptr for loc_id */
-    H5VL_loc_params_t loc_params;                     /* Location parameters for object access */
-    herr_t            ret_value = SUCCEED;            /* Return value */
+    H5VL_object_specific_args_t vol_cb_args;          /* Arguments to VOL callback */
+    H5VL_loc_params_t           loc_params;           /* Location parameters for object access */
+    herr_t                      ret_value = SUCCEED;  /* Return value */
 
     FUNC_ENTER_STATIC
 
-    /* Check args */
-
+    /* Setup and check args */
     if (H5VL_setup_loc_args(obj_id, vol_obj_ptr, &loc_params) < 0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTSET, FAIL, "can't set object access arguments")
 
+    /* Set up VOL callback arguments */
+    vol_cb_args.op_type           = H5VL_OBJECT_FLUSH;
+    vol_cb_args.args.flush.obj_id = obj_id;
+
     /* Flush the object */
-    if (H5VL_object_specific(*vol_obj_ptr, &loc_params, H5VL_OBJECT_FLUSH, H5P_DATASET_XFER_DEFAULT,
-                             token_ptr, obj_id) < 0)
+    if (H5VL_object_specific(*vol_obj_ptr, &loc_params, &vol_cb_args, H5P_DATASET_XFER_DEFAULT, token_ptr) <
+        0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTFLUSH, FAIL, "unable to flush object")
 
 done:
@@ -718,19 +723,23 @@ H5O__refresh_api_common(hid_t oid, void **token_ptr, H5VL_object_t **_vol_obj_pt
     H5VL_object_t * tmp_vol_obj = NULL; /* Object for loc_id */
     H5VL_object_t **vol_obj_ptr =
         (_vol_obj_ptr ? _vol_obj_ptr : &tmp_vol_obj); /* Ptr to object ptr for loc_id */
-    H5VL_loc_params_t loc_params;                     /* Location parameters for object access */
-    herr_t            ret_value = SUCCEED;            /* Return value */
+    H5VL_object_specific_args_t vol_cb_args;          /* Arguments to VOL callback */
+    H5VL_loc_params_t           loc_params;           /* Location parameters for object access */
+    herr_t                      ret_value = SUCCEED;  /* Return value */
 
     FUNC_ENTER_STATIC
 
-    /* Check args */
-
+    /* Setup and check args */
     if (H5VL_setup_loc_args(oid, vol_obj_ptr, &loc_params) < 0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTSET, FAIL, "can't set object access arguments")
 
+    /* Set up VOL callback arguments */
+    vol_cb_args.op_type             = H5VL_OBJECT_REFRESH;
+    vol_cb_args.args.refresh.obj_id = oid;
+
     /* Refresh the object */
-    if (H5VL_object_specific(*vol_obj_ptr, &loc_params, H5VL_OBJECT_REFRESH, H5P_DATASET_XFER_DEFAULT,
-                             token_ptr, oid) < 0)
+    if (H5VL_object_specific(*vol_obj_ptr, &loc_params, &vol_cb_args, H5P_DATASET_XFER_DEFAULT, token_ptr) <
+        0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTLOAD, FAIL, "unable to refresh object")
 
 done:
@@ -829,12 +838,12 @@ done:
 herr_t
 H5Olink(hid_t obj_id, hid_t new_loc_id, const char *new_name, hid_t lcpl_id, hid_t lapl_id)
 {
-    H5VL_object_t *   vol_obj1 = NULL; /* object of obj_id */
-    H5VL_object_t *   vol_obj2 = NULL; /* object of new_loc_id */
-    H5VL_object_t     tmp_vol_obj;     /* Temporary object */
-    H5VL_loc_params_t loc_params1;
-    H5VL_loc_params_t loc_params2;
-    herr_t            ret_value = SUCCEED; /* Return value */
+    H5VL_object_t *         vol_obj1 = NULL; /* object of obj_id */
+    H5VL_object_t *         vol_obj2 = NULL; /* object of new_loc_id */
+    H5VL_object_t           tmp_vol_obj;     /* Temporary object */
+    H5VL_link_create_args_t vol_cb_args;     /* Arguments to VOL callback */
+    H5VL_loc_params_t       new_loc_params;
+    herr_t                  ret_value = SUCCEED; /* Return value */
 
     FUNC_ENTER_API(FAIL)
     H5TRACE5("e", "ii*sii", obj_id, new_loc_id, new_name, lcpl_id, lapl_id);
@@ -864,36 +873,45 @@ H5Olink(hid_t obj_id, hid_t new_loc_id, const char *new_name, hid_t lcpl_id, hid
     if (H5CX_set_apl(&lapl_id, H5P_CLS_LACC, obj_id, TRUE) < 0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTSET, FAIL, "can't set access property list info")
 
-    loc_params1.type     = H5VL_OBJECT_BY_SELF;
-    loc_params1.obj_type = H5I_get_type(obj_id);
-
-    loc_params2.type                         = H5VL_OBJECT_BY_NAME;
-    loc_params2.obj_type                     = H5I_get_type(new_loc_id);
-    loc_params2.loc_data.loc_by_name.name    = new_name;
-    loc_params2.loc_data.loc_by_name.lapl_id = lapl_id;
+    /* Set up new location struct */
+    new_loc_params.type                         = H5VL_OBJECT_BY_NAME;
+    new_loc_params.obj_type                     = H5I_get_type(new_loc_id);
+    new_loc_params.loc_data.loc_by_name.name    = new_name;
+    new_loc_params.loc_data.loc_by_name.lapl_id = lapl_id;
 
-    if (H5L_SAME_LOC != obj_id)
-        /* get the location object */
-        if (NULL == (vol_obj1 = H5VL_vol_object(obj_id)))
-            HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "invalid location identifier")
+    /* Get the first location object */
+    if (NULL == (vol_obj1 = H5VL_vol_object(obj_id)))
+        HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "invalid location identifier")
     if (H5L_SAME_LOC != new_loc_id)
         /* get the location object */
         if (NULL == (vol_obj2 = H5VL_vol_object(new_loc_id)))
             HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "invalid location identifier")
 
     /* Make sure that the VOL connectors are the same */
-    if (vol_obj1 && vol_obj2)
-        if (vol_obj1->connector->cls->value != vol_obj2->connector->cls->value)
+    if (vol_obj1 && vol_obj2) {
+        int same_connector = 0;
+
+        /* Check if both objects are associated with the same VOL connector */
+        if (H5VL_cmp_connector_cls(&same_connector, vol_obj1->connector->cls, vol_obj2->connector->cls) < 0)
+            HGOTO_ERROR(H5E_FILE, H5E_CANTCOMPARE, FAIL, "can't compare connector classes")
+        if (same_connector)
             HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL,
                         "Objects are accessed through different VOL connectors and can't be linked")
+    } /* end if */
 
     /* Construct a temporary VOL object */
     tmp_vol_obj.data      = vol_obj2->data;
-    tmp_vol_obj.connector = (vol_obj1 != NULL ? vol_obj1->connector : vol_obj2->connector);
+    tmp_vol_obj.connector = vol_obj1->connector;
+
+    /* Set up VOL callback arguments */
+    vol_cb_args.op_type                            = H5VL_LINK_CREATE_HARD;
+    vol_cb_args.args.hard.curr_obj                 = vol_obj1->data;
+    vol_cb_args.args.hard.curr_loc_params.type     = H5VL_OBJECT_BY_SELF;
+    vol_cb_args.args.hard.curr_loc_params.obj_type = H5I_get_type(obj_id);
 
     /* Create a link to the object */
-    if (H5VL_link_create(H5VL_LINK_CREATE_HARD, &tmp_vol_obj, &loc_params2, lcpl_id, lapl_id,
-                         H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, vol_obj1->data, &loc_params1) < 0)
+    if (H5VL_link_create(&vol_cb_args, &tmp_vol_obj, &new_loc_params, lcpl_id, lapl_id,
+                         H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTCREATE, FAIL, "unable to create link")
 
 done:
@@ -923,9 +941,10 @@ done:
 herr_t
 H5Oincr_refcount(hid_t object_id)
 {
-    H5VL_object_t *   vol_obj; /* Object of loc_id */
-    H5VL_loc_params_t loc_params;
-    herr_t            ret_value = SUCCEED;
+    H5VL_object_t *             vol_obj;     /* Object of loc_id */
+    H5VL_object_specific_args_t vol_cb_args; /* Arguments to VOL callback */
+    H5VL_loc_params_t           loc_params;  /* Location parameters for object access */
+    herr_t                      ret_value = SUCCEED;
 
     FUNC_ENTER_API(FAIL)
     H5TRACE1("e", "i", object_id);
@@ -941,9 +960,13 @@ H5Oincr_refcount(hid_t object_id)
     if (H5CX_set_loc(object_id) < 0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTSET, FAIL, "can't set access property list info")
 
+    /* Set up VOL callback arguments */
+    vol_cb_args.op_type              = H5VL_OBJECT_CHANGE_REF_COUNT;
+    vol_cb_args.args.change_rc.delta = 1;
+
     /* Change the object's reference count */
-    if (H5VL_object_specific(vol_obj, &loc_params, H5VL_OBJECT_CHANGE_REF_COUNT, H5P_DATASET_XFER_DEFAULT,
-                             H5_REQUEST_NULL, 1) < 0)
+    if (H5VL_object_specific(vol_obj, &loc_params, &vol_cb_args, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) <
+        0)
         HGOTO_ERROR(H5E_OHDR, H5E_LINKCOUNT, FAIL, "modifying object link count failed")
 
 done:
@@ -973,9 +996,10 @@ done:
 herr_t
 H5Odecr_refcount(hid_t object_id)
 {
-    H5VL_object_t *   vol_obj; /* Object of loc_id */
-    H5VL_loc_params_t loc_params;
-    herr_t            ret_value = SUCCEED; /* Return value */
+    H5VL_object_t *             vol_obj;             /* Object of loc_id */
+    H5VL_object_specific_args_t vol_cb_args;         /* Arguments to VOL callback */
+    H5VL_loc_params_t           loc_params;          /* Location parameters for object access */
+    herr_t                      ret_value = SUCCEED; /* Return value */
 
     FUNC_ENTER_API(FAIL)
     H5TRACE1("e", "i", object_id);
@@ -991,9 +1015,13 @@ H5Odecr_refcount(hid_t object_id)
     if (H5CX_set_loc(object_id) < 0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTSET, FAIL, "can't set access property list info")
 
+    /* Set up VOL callback arguments */
+    vol_cb_args.op_type              = H5VL_OBJECT_CHANGE_REF_COUNT;
+    vol_cb_args.args.change_rc.delta = -1;
+
     /* Change the object's reference count */
-    if (H5VL_object_specific(vol_obj, &loc_params, H5VL_OBJECT_CHANGE_REF_COUNT, H5P_DATASET_XFER_DEFAULT,
-                             H5_REQUEST_NULL, -1) < 0)
+    if (H5VL_object_specific(vol_obj, &loc_params, &vol_cb_args, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) <
+        0)
         HGOTO_ERROR(H5E_OHDR, H5E_LINKCOUNT, FAIL, "modifying object link count failed")
 
 done:
@@ -1016,9 +1044,11 @@ done:
 htri_t
 H5Oexists_by_name(hid_t loc_id, const char *name, hid_t lapl_id)
 {
-    H5VL_object_t *   vol_obj; /* Object of loc_id */
-    H5VL_loc_params_t loc_params;
-    htri_t            ret_value = FAIL; /* Return value */
+    H5VL_object_t *             vol_obj;            /* Object of loc_id */
+    H5VL_object_specific_args_t vol_cb_args;        /* Arguments to VOL callback */
+    H5VL_loc_params_t           loc_params;         /* Location parameters for object access */
+    hbool_t                     obj_exists = FALSE; /* Whether object exists */
+    htri_t                      ret_value  = FAIL;  /* Return value */
 
     FUNC_ENTER_API(FAIL)
     H5TRACE3("t", "i*si", loc_id, name, lapl_id);
@@ -1043,11 +1073,18 @@ H5Oexists_by_name(hid_t loc_id, const char *name, hid_t lapl_id)
     loc_params.loc_data.loc_by_name.lapl_id = lapl_id;
     loc_params.obj_type                     = H5I_get_type(loc_id);
 
+    /* Set up VOL callback arguments */
+    vol_cb_args.op_type            = H5VL_OBJECT_EXISTS;
+    vol_cb_args.args.exists.exists = &obj_exists;
+
     /* Check if the object exists */
-    if (H5VL_object_specific(vol_obj, &loc_params, H5VL_OBJECT_EXISTS, H5P_DATASET_XFER_DEFAULT,
-                             H5_REQUEST_NULL, &ret_value) < 0)
+    if (H5VL_object_specific(vol_obj, &loc_params, &vol_cb_args, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) <
+        0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTGET, FAIL, "unable to determine if '%s' exists", name)
 
+    /* Set return value */
+    ret_value = (htri_t)obj_exists;
+
 done:
     FUNC_LEAVE_API(ret_value)
 } /* end H5Oexists_by_name() */
@@ -1067,9 +1104,10 @@ done:
 herr_t
 H5Oget_info3(hid_t loc_id, H5O_info2_t *oinfo /*out*/, unsigned fields)
 {
-    H5VL_object_t *   vol_obj; /* Object of loc_id */
-    H5VL_loc_params_t loc_params;
-    herr_t            ret_value = SUCCEED; /* Return value */
+    H5VL_object_t *        vol_obj;     /* Object of loc_id */
+    H5VL_object_get_args_t vol_cb_args; /* Arguments to VOL callback */
+    H5VL_loc_params_t      loc_params;
+    herr_t                 ret_value = SUCCEED; /* Return value */
 
     FUNC_ENTER_API(FAIL)
     H5TRACE3("e", "ixIu", loc_id, oinfo, fields);
@@ -1088,9 +1126,13 @@ H5Oget_info3(hid_t loc_id, H5O_info2_t *oinfo /*out*/, unsigned fields)
     if (NULL == (vol_obj = H5VL_vol_object(loc_id)))
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "invalid location identifier")
 
+    /* Set up VOL callback arguments */
+    vol_cb_args.op_type              = H5VL_OBJECT_GET_INFO;
+    vol_cb_args.args.get_info.oinfo  = oinfo;
+    vol_cb_args.args.get_info.fields = fields;
+
     /* Retrieve the object's information */
-    if (H5VL_object_get(vol_obj, &loc_params, H5VL_OBJECT_GET_INFO, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL,
-                        oinfo, fields) < 0)
+    if (H5VL_object_get(vol_obj, &loc_params, &vol_cb_args, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTGET, FAIL, "can't get data model info for object")
 
 done:
@@ -1114,8 +1156,9 @@ H5O__get_info_by_name_api_common(hid_t loc_id, const char *name, H5O_info2_t *oi
     H5VL_object_t * tmp_vol_obj = NULL; /* Object for loc_id */
     H5VL_object_t **vol_obj_ptr =
         (_vol_obj_ptr ? _vol_obj_ptr : &tmp_vol_obj); /* Ptr to object ptr for loc_id */
-    H5VL_loc_params_t loc_params;                     /* Location parameters for object access */
-    herr_t            ret_value = SUCCEED;            /* Return value */
+    H5VL_object_get_args_t vol_cb_args;               /* Arguments to VOL callback */
+    H5VL_loc_params_t      loc_params;                /* Location parameters for object access */
+    herr_t                 ret_value = SUCCEED;       /* Return value */
 
     FUNC_ENTER_STATIC
 
@@ -1127,12 +1170,16 @@ H5O__get_info_by_name_api_common(hid_t loc_id, const char *name, H5O_info2_t *oi
 
     /* "name" is checked in H5VL_setup_name_args() */
     /* Set up object access arguments */
-    if (H5VL_setup_name_args(loc_id, name, H5P_CLS_LACC, FALSE, lapl_id, vol_obj_ptr, &loc_params) < 0)
+    if (H5VL_setup_name_args(loc_id, name, FALSE, lapl_id, vol_obj_ptr, &loc_params) < 0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTSET, FAIL, "can't set object access arguments")
 
+    /* Set up VOL callback arguments */
+    vol_cb_args.op_type              = H5VL_OBJECT_GET_INFO;
+    vol_cb_args.args.get_info.oinfo  = oinfo;
+    vol_cb_args.args.get_info.fields = fields;
+
     /* Retrieve the object's information */
-    if (H5VL_object_get(*vol_obj_ptr, &loc_params, H5VL_OBJECT_GET_INFO, H5P_DATASET_XFER_DEFAULT, token_ptr,
-                        oinfo, fields) < 0)
+    if (H5VL_object_get(*vol_obj_ptr, &loc_params, &vol_cb_args, H5P_DATASET_XFER_DEFAULT, token_ptr) < 0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTGET, FAIL, "can't get data model info for object")
 
 done:
@@ -1230,9 +1277,10 @@ herr_t
 H5Oget_info_by_idx3(hid_t loc_id, const char *group_name, H5_index_t idx_type, H5_iter_order_t order,
                     hsize_t n, H5O_info2_t *oinfo /*out*/, unsigned fields, hid_t lapl_id)
 {
-    H5VL_object_t *   vol_obj; /* Object of loc_id */
-    H5VL_loc_params_t loc_params;
-    herr_t            ret_value = SUCCEED; /* Return value */
+    H5VL_object_t *        vol_obj;     /* Object of loc_id */
+    H5VL_object_get_args_t vol_cb_args; /* Arguments to VOL callback */
+    H5VL_loc_params_t      loc_params;
+    herr_t                 ret_value = SUCCEED; /* Return value */
 
     FUNC_ENTER_API(FAIL)
     H5TRACE8("e", "i*sIiIohxIui", loc_id, group_name, idx_type, order, n, oinfo, fields, lapl_id);
@@ -1253,6 +1301,7 @@ H5Oget_info_by_idx3(hid_t loc_id, const char *group_name, H5_index_t idx_type, H
     if (H5CX_set_apl(&lapl_id, H5P_CLS_LACC, loc_id, FALSE) < 0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTSET, FAIL, "can't set access property list info")
 
+    /* Set location struct fields */
     loc_params.type                         = H5VL_OBJECT_BY_IDX;
     loc_params.loc_data.loc_by_idx.name     = group_name;
     loc_params.loc_data.loc_by_idx.idx_type = idx_type;
@@ -1265,9 +1314,13 @@ H5Oget_info_by_idx3(hid_t loc_id, const char *group_name, H5_index_t idx_type, H
     if (NULL == (vol_obj = H5VL_vol_object(loc_id)))
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "invalid location identifier")
 
+    /* Set up VOL callback arguments */
+    vol_cb_args.op_type              = H5VL_OBJECT_GET_INFO;
+    vol_cb_args.args.get_info.oinfo  = oinfo;
+    vol_cb_args.args.get_info.fields = fields;
+
     /* Retrieve the object's information */
-    if (H5VL_object_get(vol_obj, &loc_params, H5VL_OBJECT_GET_INFO, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL,
-                        oinfo, fields) < 0)
+    if (H5VL_object_get(vol_obj, &loc_params, &vol_cb_args, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTGET, FAIL, "can't get data model info for object")
 
 done:
@@ -1289,9 +1342,11 @@ done:
 herr_t
 H5Oget_native_info(hid_t loc_id, H5O_native_info_t *oinfo /*out*/, unsigned fields)
 {
-    H5VL_object_t *   vol_obj; /* Object of loc_id */
-    H5VL_loc_params_t loc_params;
-    herr_t            ret_value = SUCCEED; /* Return value */
+    H5VL_object_t *                    vol_obj;      /* Object of loc_id */
+    H5VL_optional_args_t               vol_cb_args;  /* Arguments to VOL callback */
+    H5VL_native_object_optional_args_t obj_opt_args; /* Arguments for optional operation */
+    H5VL_loc_params_t                  loc_params;
+    herr_t                             ret_value = SUCCEED; /* Return value */
 
     FUNC_ENTER_API(FAIL)
     H5TRACE3("e", "ixIu", loc_id, oinfo, fields);
@@ -1310,9 +1365,15 @@ H5Oget_native_info(hid_t loc_id, H5O_native_info_t *oinfo /*out*/, unsigned fiel
     if (NULL == (vol_obj = H5VL_vol_object(loc_id)))
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "invalid location identifier")
 
+    /* Set up VOL callback arguments */
+    obj_opt_args.get_native_info.fields = fields;
+    obj_opt_args.get_native_info.ninfo  = oinfo;
+    vol_cb_args.op_type                 = H5VL_NATIVE_OBJECT_GET_NATIVE_INFO;
+    vol_cb_args.args                    = &obj_opt_args;
+
     /* Retrieve the object's information */
-    if (H5VL_object_optional(vol_obj, H5VL_NATIVE_OBJECT_GET_NATIVE_INFO, H5P_DATASET_XFER_DEFAULT,
-                             H5_REQUEST_NULL, &loc_params, oinfo, fields) < 0)
+    if (H5VL_object_optional(vol_obj, &loc_params, &vol_cb_args, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) <
+        0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTGET, FAIL, "can't get native file format info for object")
 
 done:
@@ -1335,9 +1396,11 @@ herr_t
 H5Oget_native_info_by_name(hid_t loc_id, const char *name, H5O_native_info_t *oinfo /*out*/, unsigned fields,
                            hid_t lapl_id)
 {
-    H5VL_object_t *   vol_obj; /* Object of loc_id */
-    H5VL_loc_params_t loc_params;
-    herr_t            ret_value = SUCCEED; /* Return value */
+    H5VL_object_t *                    vol_obj;      /* Object of loc_id */
+    H5VL_optional_args_t               vol_cb_args;  /* Arguments to VOL callback */
+    H5VL_native_object_optional_args_t obj_opt_args; /* Arguments for optional operation */
+    H5VL_loc_params_t                  loc_params;
+    herr_t                             ret_value = SUCCEED; /* Return value */
 
     FUNC_ENTER_API(FAIL)
     H5TRACE5("e", "i*sxIui", loc_id, name, oinfo, fields, lapl_id);
@@ -1366,9 +1429,15 @@ H5Oget_native_info_by_name(hid_t loc_id, const char *name, H5O_native_info_t *oi
     if (NULL == (vol_obj = H5VL_vol_object(loc_id)))
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "invalid location identifier")
 
+    /* Set up VOL callback arguments */
+    obj_opt_args.get_native_info.fields = fields;
+    obj_opt_args.get_native_info.ninfo  = oinfo;
+    vol_cb_args.op_type                 = H5VL_NATIVE_OBJECT_GET_NATIVE_INFO;
+    vol_cb_args.args                    = &obj_opt_args;
+
     /* Retrieve the object's information */
-    if (H5VL_object_optional(vol_obj, H5VL_NATIVE_OBJECT_GET_NATIVE_INFO, H5P_DATASET_XFER_DEFAULT,
-                             H5_REQUEST_NULL, &loc_params, oinfo, fields) < 0)
+    if (H5VL_object_optional(vol_obj, &loc_params, &vol_cb_args, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) <
+        0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTGET, FAIL, "can't get native file format info for object: '%s'", name)
 
 done:
@@ -1393,9 +1462,11 @@ herr_t
 H5Oget_native_info_by_idx(hid_t loc_id, const char *group_name, H5_index_t idx_type, H5_iter_order_t order,
                           hsize_t n, H5O_native_info_t *oinfo /*out*/, unsigned fields, hid_t lapl_id)
 {
-    H5VL_object_t *   vol_obj; /* Object of loc_id */
-    H5VL_loc_params_t loc_params;
-    herr_t            ret_value = SUCCEED; /* Return value */
+    H5VL_object_t *                    vol_obj;      /* Object of loc_id */
+    H5VL_optional_args_t               vol_cb_args;  /* Arguments to VOL callback */
+    H5VL_native_object_optional_args_t obj_opt_args; /* Arguments for optional operation */
+    H5VL_loc_params_t                  loc_params;
+    herr_t                             ret_value = SUCCEED; /* Return value */
 
     FUNC_ENTER_API(FAIL)
     H5TRACE8("e", "i*sIiIohxIui", loc_id, group_name, idx_type, order, n, oinfo, fields, lapl_id);
@@ -1416,6 +1487,7 @@ H5Oget_native_info_by_idx(hid_t loc_id, const char *group_name, H5_index_t idx_t
     if (H5CX_set_apl(&lapl_id, H5P_CLS_LACC, loc_id, FALSE) < 0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTSET, FAIL, "can't set access property list info")
 
+    /* Set location struct fields */
     loc_params.type                         = H5VL_OBJECT_BY_IDX;
     loc_params.loc_data.loc_by_idx.name     = group_name;
     loc_params.loc_data.loc_by_idx.idx_type = idx_type;
@@ -1428,9 +1500,15 @@ H5Oget_native_info_by_idx(hid_t loc_id, const char *group_name, H5_index_t idx_t
     if (NULL == (vol_obj = H5VL_vol_object(loc_id)))
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "invalid location identifier")
 
+    /* Set up VOL callback arguments */
+    obj_opt_args.get_native_info.fields = fields;
+    obj_opt_args.get_native_info.ninfo  = oinfo;
+    vol_cb_args.op_type                 = H5VL_NATIVE_OBJECT_GET_NATIVE_INFO;
+    vol_cb_args.args                    = &obj_opt_args;
+
     /* Retrieve the object's information */
-    if (H5VL_object_optional(vol_obj, H5VL_NATIVE_OBJECT_GET_NATIVE_INFO, H5P_DATASET_XFER_DEFAULT,
-                             H5_REQUEST_NULL, &loc_params, oinfo, fields) < 0)
+    if (H5VL_object_optional(vol_obj, &loc_params, &vol_cb_args, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) <
+        0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTGET, FAIL, "can't get native file format info for object")
 
 done:
@@ -1457,9 +1535,11 @@ done:
 herr_t
 H5Oset_comment(hid_t obj_id, const char *comment)
 {
-    H5VL_object_t *   vol_obj; /* Object of loc_id */
-    H5VL_loc_params_t loc_params;
-    herr_t            ret_value = SUCCEED; /* Return value */
+    H5VL_object_t *                    vol_obj;      /* Object of loc_id */
+    H5VL_optional_args_t               vol_cb_args;  /* Arguments to VOL callback */
+    H5VL_native_object_optional_args_t obj_opt_args; /* Arguments for optional operation */
+    H5VL_loc_params_t                  loc_params;
+    herr_t                             ret_value = SUCCEED; /* Return value */
 
     FUNC_ENTER_API(FAIL)
     H5TRACE2("e", "i*s", obj_id, comment);
@@ -1476,9 +1556,14 @@ H5Oset_comment(hid_t obj_id, const char *comment)
     loc_params.type     = H5VL_OBJECT_BY_SELF;
     loc_params.obj_type = H5I_get_type(obj_id);
 
+    /* Set up VOL callback arguments */
+    obj_opt_args.set_comment.comment = comment;
+    vol_cb_args.op_type              = H5VL_NATIVE_OBJECT_SET_COMMENT;
+    vol_cb_args.args                 = &obj_opt_args;
+
     /* (Re)set the object's comment */
-    if (H5VL_object_optional(vol_obj, H5VL_NATIVE_OBJECT_SET_COMMENT, H5P_DATASET_XFER_DEFAULT,
-                             H5_REQUEST_NULL, &loc_params, comment) < 0)
+    if (H5VL_object_optional(vol_obj, &loc_params, &vol_cb_args, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) <
+        0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTSET, FAIL, "can't set comment for object")
 
 done:
@@ -1505,9 +1590,11 @@ done:
 herr_t
 H5Oset_comment_by_name(hid_t loc_id, const char *name, const char *comment, hid_t lapl_id)
 {
-    H5VL_object_t *   vol_obj; /* Object of loc_id */
-    H5VL_loc_params_t loc_params;
-    herr_t            ret_value = SUCCEED; /* Return value */
+    H5VL_object_t *                    vol_obj;      /* Object of loc_id */
+    H5VL_optional_args_t               vol_cb_args;  /* Arguments to VOL callback */
+    H5VL_native_object_optional_args_t obj_opt_args; /* Arguments for optional operation */
+    H5VL_loc_params_t                  loc_params;
+    herr_t                             ret_value = SUCCEED; /* Return value */
 
     FUNC_ENTER_API(FAIL)
     H5TRACE4("e", "i*s*si", loc_id, name, comment, lapl_id);
@@ -1530,9 +1617,14 @@ H5Oset_comment_by_name(hid_t loc_id, const char *name, const char *comment, hid_
     if (NULL == (vol_obj = H5VL_vol_object(loc_id)))
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "invalid location identifier")
 
+    /* Set up VOL callback arguments */
+    obj_opt_args.set_comment.comment = comment;
+    vol_cb_args.op_type              = H5VL_NATIVE_OBJECT_SET_COMMENT;
+    vol_cb_args.args                 = &obj_opt_args;
+
     /* (Re)set the object's comment */
-    if (H5VL_object_optional(vol_obj, H5VL_NATIVE_OBJECT_SET_COMMENT, H5P_DATASET_XFER_DEFAULT,
-                             H5_REQUEST_NULL, &loc_params, comment) < 0)
+    if (H5VL_object_optional(vol_obj, &loc_params, &vol_cb_args, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) <
+        0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTSET, FAIL, "can't set comment for object: '%s'", name)
 
 done:
@@ -1558,9 +1650,12 @@ done:
 ssize_t
 H5Oget_comment(hid_t obj_id, char *comment /*out*/, size_t bufsize)
 {
-    H5VL_object_t *   vol_obj; /* Object of loc_id */
-    H5VL_loc_params_t loc_params;
-    ssize_t           ret_value = -1; /* Return value */
+    H5VL_object_t *                    vol_obj;      /* Object of loc_id */
+    H5VL_optional_args_t               vol_cb_args;  /* Arguments to VOL callback */
+    H5VL_native_object_optional_args_t obj_opt_args; /* Arguments for optional operation */
+    H5VL_loc_params_t                  loc_params;
+    size_t                             comment_len = 0;  /* Length of comment string */
+    ssize_t                            ret_value   = -1; /* Return value */
 
     FUNC_ENTER_API((-1))
     H5TRACE3("Zs", "ixz", obj_id, comment, bufsize);
@@ -1573,11 +1668,21 @@ H5Oget_comment(hid_t obj_id, char *comment /*out*/, size_t bufsize)
     loc_params.type     = H5VL_OBJECT_BY_SELF;
     loc_params.obj_type = H5I_get_type(obj_id);
 
+    /* Set up VOL callback arguments */
+    obj_opt_args.get_comment.buf         = comment;
+    obj_opt_args.get_comment.buf_size    = bufsize;
+    obj_opt_args.get_comment.comment_len = &comment_len;
+    vol_cb_args.op_type                  = H5VL_NATIVE_OBJECT_GET_COMMENT;
+    vol_cb_args.args                     = &obj_opt_args;
+
     /* Retrieve the object's comment */
-    if (H5VL_object_optional(vol_obj, H5VL_NATIVE_OBJECT_GET_COMMENT, H5P_DATASET_XFER_DEFAULT,
-                             H5_REQUEST_NULL, &loc_params, comment, bufsize, &ret_value) < 0)
+    if (H5VL_object_optional(vol_obj, &loc_params, &vol_cb_args, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) <
+        0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTGET, (-1), "can't get comment for object")
 
+    /* Set return value */
+    ret_value = (ssize_t)comment_len;
+
 done:
     FUNC_LEAVE_API(ret_value)
 } /* end H5Oget_comment() */
@@ -1601,9 +1706,12 @@ done:
 ssize_t
 H5Oget_comment_by_name(hid_t loc_id, const char *name, char *comment /*out*/, size_t bufsize, hid_t lapl_id)
 {
-    H5VL_object_t *   vol_obj; /* Object of loc_id */
-    H5VL_loc_params_t loc_params;
-    ssize_t           ret_value = -1; /* Return value */
+    H5VL_object_t *                    vol_obj;      /* Object of loc_id */
+    H5VL_optional_args_t               vol_cb_args;  /* Arguments to VOL callback */
+    H5VL_native_object_optional_args_t obj_opt_args; /* Arguments for optional operation */
+    H5VL_loc_params_t                  loc_params;
+    size_t                             comment_len = 0;  /* Length of comment string */
+    ssize_t                            ret_value   = -1; /* Return value */
 
     FUNC_ENTER_API((-1))
     H5TRACE5("Zs", "i*sxzi", loc_id, name, comment, bufsize, lapl_id);
@@ -1626,11 +1734,21 @@ H5Oget_comment_by_name(hid_t loc_id, const char *name, char *comment /*out*/, si
     if (NULL == (vol_obj = H5VL_vol_object(loc_id)))
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, (-1), "invalid location identifier")
 
+    /* Set up VOL callback arguments */
+    obj_opt_args.get_comment.buf         = comment;
+    obj_opt_args.get_comment.buf_size    = bufsize;
+    obj_opt_args.get_comment.comment_len = &comment_len;
+    vol_cb_args.op_type                  = H5VL_NATIVE_OBJECT_GET_COMMENT;
+    vol_cb_args.args                     = &obj_opt_args;
+
     /* Retrieve the object's comment */
-    if (H5VL_object_optional(vol_obj, H5VL_NATIVE_OBJECT_GET_COMMENT, H5P_DATASET_XFER_DEFAULT,
-                             H5_REQUEST_NULL, &loc_params, comment, bufsize, &ret_value) < 0)
+    if (H5VL_object_optional(vol_obj, &loc_params, &vol_cb_args, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) <
+        0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTGET, (-1), "can't get comment for object: '%s'", name)
 
+    /* Set return value */
+    ret_value = (ssize_t)comment_len;
+
 done:
     FUNC_LEAVE_API(ret_value)
 } /* end H5Oget_comment_by_name() */
@@ -1674,9 +1792,10 @@ herr_t
 H5Ovisit3(hid_t obj_id, H5_index_t idx_type, H5_iter_order_t order, H5O_iterate2_t op, void *op_data,
           unsigned fields)
 {
-    H5VL_object_t *   vol_obj; /* Object of loc_id */
-    H5VL_loc_params_t loc_params;
-    herr_t            ret_value; /* Return value */
+    H5VL_object_t *             vol_obj;     /* Object of loc_id */
+    H5VL_object_specific_args_t vol_cb_args; /* Arguments to VOL callback */
+    H5VL_loc_params_t           loc_params;  /* Location parameters for object access */
+    herr_t                      ret_value;   /* Return value */
 
     FUNC_ENTER_API(FAIL)
     H5TRACE6("e", "iIiIoOI*xIu", obj_id, idx_type, order, op, op_data, fields);
@@ -1699,10 +1818,17 @@ H5Ovisit3(hid_t obj_id, H5_index_t idx_type, H5_iter_order_t order, H5O_iterate2
     loc_params.type     = H5VL_OBJECT_BY_SELF;
     loc_params.obj_type = H5I_get_type(obj_id);
 
+    /* Set up VOL callback arguments */
+    vol_cb_args.op_type             = H5VL_OBJECT_VISIT;
+    vol_cb_args.args.visit.idx_type = idx_type;
+    vol_cb_args.args.visit.order    = order;
+    vol_cb_args.args.visit.op       = op;
+    vol_cb_args.args.visit.op_data  = op_data;
+    vol_cb_args.args.visit.fields   = fields;
+
     /* Visit the objects */
-    if ((ret_value = H5VL_object_specific(vol_obj, &loc_params, H5VL_OBJECT_VISIT, H5P_DATASET_XFER_DEFAULT,
-                                          H5_REQUEST_NULL, (int)idx_type, (int)order, op, op_data, fields)) <
-        0)
+    if ((ret_value = H5VL_object_specific(vol_obj, &loc_params, &vol_cb_args, H5P_DATASET_XFER_DEFAULT,
+                                          H5_REQUEST_NULL)) < 0)
         HGOTO_ERROR(H5E_OHDR, H5E_BADITER, FAIL, "object iteration failed")
 
 done:
@@ -1748,9 +1874,10 @@ herr_t
 H5Ovisit_by_name3(hid_t loc_id, const char *obj_name, H5_index_t idx_type, H5_iter_order_t order,
                   H5O_iterate2_t op, void *op_data, unsigned fields, hid_t lapl_id)
 {
-    H5VL_object_t *   vol_obj; /* Object of loc_id */
-    H5VL_loc_params_t loc_params;
-    herr_t            ret_value; /* Return value */
+    H5VL_object_t *             vol_obj;     /* Object of loc_id */
+    H5VL_object_specific_args_t vol_cb_args; /* Arguments to VOL callback */
+    H5VL_loc_params_t           loc_params;  /* Location parameters for object access */
+    herr_t                      ret_value;   /* Return value */
 
     FUNC_ENTER_API(FAIL)
     H5TRACE8("e", "i*sIiIoOI*xIui", loc_id, obj_name, idx_type, order, op, op_data, fields, lapl_id);
@@ -1783,10 +1910,17 @@ H5Ovisit_by_name3(hid_t loc_id, const char *obj_name, H5_index_t idx_type, H5_it
     loc_params.loc_data.loc_by_name.lapl_id = lapl_id;
     loc_params.obj_type                     = H5I_get_type(loc_id);
 
+    /* Set up VOL callback arguments */
+    vol_cb_args.op_type             = H5VL_OBJECT_VISIT;
+    vol_cb_args.args.visit.idx_type = idx_type;
+    vol_cb_args.args.visit.order    = order;
+    vol_cb_args.args.visit.op       = op;
+    vol_cb_args.args.visit.op_data  = op_data;
+    vol_cb_args.args.visit.fields   = fields;
+
     /* Visit the objects */
-    if ((ret_value = H5VL_object_specific(vol_obj, &loc_params, H5VL_OBJECT_VISIT, H5P_DATASET_XFER_DEFAULT,
-                                          H5_REQUEST_NULL, (int)idx_type, (int)order, op, op_data, fields)) <
-        0)
+    if ((ret_value = H5VL_object_specific(vol_obj, &loc_params, &vol_cb_args, H5P_DATASET_XFER_DEFAULT,
+                                          H5_REQUEST_NULL)) < 0)
         HGOTO_ERROR(H5E_OHDR, H5E_BADITER, FAIL, "object iteration failed")
 
 done:
@@ -1794,23 +1928,23 @@ done:
 } /* end H5Ovisit_by_name3() */
 
 /*-------------------------------------------------------------------------
- * Function:    H5O__close_check_common
+ * Function:    H5O__close_check_type
  *
  * Purpose:     This is the common function to validate an object
- *              when closing it.
+ *              before closing it.
  *
  * Return:      TRUE/FALSE/FAIL
  *
  *-------------------------------------------------------------------------
  */
 static htri_t
-H5O__close_check_common(hid_t object_id)
+H5O__close_check_type(hid_t object_id)
 {
     htri_t ret_value = TRUE; /* Return value */
 
     FUNC_ENTER_STATIC
 
-    /* Get the type of the object and close it in the correct way */
+    /* Check for closeable object */
     switch (H5I_get_type(object_id)) {
         case H5I_GROUP:
         case H5I_DATATYPE:
@@ -1836,14 +1970,13 @@ H5O__close_check_common(hid_t object_id)
         case H5I_EVENTSET:
         case H5I_NTYPES:
         default:
-            HGOTO_ERROR(H5E_ARGS, H5E_CANTRELEASE, FALSE,
-                        "not a valid file object ID (dataset, group, or datatype)")
+            HGOTO_DONE(FALSE);
             break;
     } /* end switch */
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
-} /* H5O__close_check_common() */
+} /* H5O__close_check_type() */
 
 /*-------------------------------------------------------------------------
  * Function:    H5Oclose
@@ -1871,7 +2004,7 @@ H5Oclose(hid_t object_id)
     H5TRACE1("e", "i", object_id);
 
     /* Validate the object type before closing */
-    if (H5O__close_check_common(object_id) <= 0)
+    if (H5O__close_check_type(object_id) <= 0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTRELEASE, FAIL, "not a valid object")
 
     if (H5I_dec_app_ref(object_id) < 0)
@@ -1903,7 +2036,7 @@ H5Oclose_async(const char *app_file, const char *app_func, unsigned app_line, hi
     H5TRACE5("e", "*s*sIuii", app_file, app_func, app_line, object_id, es_id);
 
     /* Validate the object type before closing */
-    if (H5O__close_check_common(object_id) <= 0)
+    if (H5O__close_check_type(object_id) <= 0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTRELEASE, FAIL, "not a valid object")
 
     /* Prepare for possible asynchronous operation */
@@ -1943,7 +2076,7 @@ done:
 } /* end H5Oclose_async() */
 
 /*-------------------------------------------------------------------------
- * Function:    H5O_disable_mdc_flushes
+ * Function:    H5O__disable_mdc_flushes
  *
  * Purpose:     Private version of the metadata cache cork function.
  *
@@ -1952,18 +2085,18 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5O_disable_mdc_flushes(H5O_loc_t *oloc)
+H5O__disable_mdc_flushes(H5O_loc_t *oloc)
 {
     herr_t ret_value = SUCCEED;
 
-    FUNC_ENTER_NOAPI(FAIL);
+    FUNC_ENTER_PACKAGE
 
     if (H5AC_cork(oloc->file, oloc->addr, H5AC__SET_CORK, NULL) < 0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTCORK, FAIL, "unable to cork object");
 
 done:
     FUNC_LEAVE_NOAPI(ret_value);
-} /* H5O_disable_mdc_flushes() */
+} /* H5O__disable_mdc_flushes() */
 
 /*-------------------------------------------------------------------------
  * Function:    H5Odisable_mdc_flushes
@@ -1982,9 +2115,10 @@ done:
 herr_t
 H5Odisable_mdc_flushes(hid_t object_id)
 {
-    H5VL_object_t *   vol_obj;             /* Object of loc_id */
-    H5VL_loc_params_t loc_params;          /* Location parameters */
-    herr_t            ret_value = SUCCEED; /* Return value */
+    H5VL_object_t *      vol_obj;             /* Object of loc_id */
+    H5VL_optional_args_t vol_cb_args;         /* Arguments to VOL callback */
+    H5VL_loc_params_t    loc_params;          /* Location parameters */
+    herr_t               ret_value = SUCCEED; /* Return value */
 
     FUNC_ENTER_API(FAIL);
     H5TRACE1("e", "i", object_id);
@@ -2001,9 +2135,13 @@ H5Odisable_mdc_flushes(hid_t object_id)
     loc_params.type     = H5VL_OBJECT_BY_SELF;
     loc_params.obj_type = H5I_get_type(object_id);
 
+    /* Set up VOL callback arguments */
+    vol_cb_args.op_type = H5VL_NATIVE_OBJECT_DISABLE_MDC_FLUSHES;
+    vol_cb_args.args    = NULL;
+
     /* Cork the object */
-    if (H5VL_object_optional(vol_obj, H5VL_NATIVE_OBJECT_DISABLE_MDC_FLUSHES, H5P_DATASET_XFER_DEFAULT,
-                             H5_REQUEST_NULL, &loc_params) < 0)
+    if (H5VL_object_optional(vol_obj, &loc_params, &vol_cb_args, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) <
+        0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTCORK, FAIL, "unable to cork object");
 
 done:
@@ -2011,7 +2149,7 @@ done:
 } /* H5Odisable_mdc_flushes() */
 
 /*-------------------------------------------------------------------------
- * Function:    H5O_enable_mdc_flushes
+ * Function:    H5O__enable_mdc_flushes
  *
  * Purpose:     Private version of the metadata cache uncork function.
  *
@@ -2020,18 +2158,18 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5O_enable_mdc_flushes(H5O_loc_t *oloc)
+H5O__enable_mdc_flushes(H5O_loc_t *oloc)
 {
     herr_t ret_value = SUCCEED;
 
-    FUNC_ENTER_NOAPI(FAIL);
+    FUNC_ENTER_PACKAGE
 
     if (H5AC_cork(oloc->file, oloc->addr, H5AC__UNCORK, NULL) < 0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTUNCORK, FAIL, "unable to uncork object");
 
 done:
     FUNC_LEAVE_NOAPI(ret_value);
-} /* H5O_enable_mdc_flushes() */
+} /* H5O__enable_mdc_flushes() */
 
 /*-------------------------------------------------------------------------
  * Function:    H5Oenable_mdc_flushes
@@ -2050,9 +2188,10 @@ done:
 herr_t
 H5Oenable_mdc_flushes(hid_t object_id)
 {
-    H5VL_object_t *   vol_obj;             /* Object of loc_id */
-    H5VL_loc_params_t loc_params;          /* Location parameters */
-    herr_t            ret_value = SUCCEED; /* Return value */
+    H5VL_object_t *      vol_obj;             /* Object of loc_id */
+    H5VL_optional_args_t vol_cb_args;         /* Arguments to VOL callback */
+    H5VL_loc_params_t    loc_params;          /* Location parameters */
+    herr_t               ret_value = SUCCEED; /* Return value */
 
     FUNC_ENTER_API(FAIL);
     H5TRACE1("e", "i", object_id);
@@ -2069,9 +2208,13 @@ H5Oenable_mdc_flushes(hid_t object_id)
     loc_params.type     = H5VL_OBJECT_BY_SELF;
     loc_params.obj_type = H5I_get_type(object_id);
 
+    /* Set up VOL callback arguments */
+    vol_cb_args.op_type = H5VL_NATIVE_OBJECT_ENABLE_MDC_FLUSHES;
+    vol_cb_args.args    = NULL;
+
     /* Uncork the object */
-    if (H5VL_object_optional(vol_obj, H5VL_NATIVE_OBJECT_ENABLE_MDC_FLUSHES, H5P_DATASET_XFER_DEFAULT,
-                             H5_REQUEST_NULL, &loc_params) < 0)
+    if (H5VL_object_optional(vol_obj, &loc_params, &vol_cb_args, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) <
+        0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTUNCORK, FAIL, "unable to uncork object");
 
 done:
@@ -2079,7 +2222,7 @@ done:
 } /* H5Oenable_mdc_flushes() */
 
 /*-------------------------------------------------------------------------
- * Function:    H5O_are_mdc_flushes_disabled
+ * Function:    H5O__are_mdc_flushes_disabled
  *
  * Purpose:     Private version of cork status getter.
  *
@@ -2088,11 +2231,11 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5O_are_mdc_flushes_disabled(H5O_loc_t *oloc, hbool_t *are_disabled)
+H5O__are_mdc_flushes_disabled(const H5O_loc_t *oloc, hbool_t *are_disabled)
 {
     herr_t ret_value = SUCCEED;
 
-    FUNC_ENTER_NOAPI(FAIL);
+    FUNC_ENTER_PACKAGE
 
     HDassert(are_disabled);
 
@@ -2101,7 +2244,7 @@ H5O_are_mdc_flushes_disabled(H5O_loc_t *oloc, hbool_t *are_disabled)
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
-} /* H5O_are_mdc_flushes_disabled() */
+} /* H5O__are_mdc_flushes_disabled() */
 
 /*-------------------------------------------------------------------------
  * Function:    H5Oare_mdc_flushes_disabled
@@ -2123,9 +2266,11 @@ done:
 herr_t
 H5Oare_mdc_flushes_disabled(hid_t object_id, hbool_t *are_disabled)
 {
-    H5VL_object_t *   vol_obj;             /* Object of loc_id */
-    H5VL_loc_params_t loc_params;          /* Location parameters */
-    herr_t            ret_value = SUCCEED; /* Return value */
+    H5VL_object_t *                    vol_obj;             /* Object of loc_id */
+    H5VL_optional_args_t               vol_cb_args;         /* Arguments to VOL callback */
+    H5VL_native_object_optional_args_t obj_opt_args;        /* Arguments for optional operation */
+    H5VL_loc_params_t                  loc_params;          /* Location parameters */
+    herr_t                             ret_value = SUCCEED; /* Return value */
 
     FUNC_ENTER_API(FAIL);
     H5TRACE2("e", "i*b", object_id, are_disabled);
@@ -2146,9 +2291,14 @@ H5Oare_mdc_flushes_disabled(hid_t object_id, hbool_t *are_disabled)
     loc_params.type     = H5VL_OBJECT_BY_SELF;
     loc_params.obj_type = H5I_get_type(object_id);
 
+    /* Set up VOL callback arguments */
+    obj_opt_args.are_mdc_flushes_disabled.flag = are_disabled;
+    vol_cb_args.op_type                        = H5VL_NATIVE_OBJECT_ARE_MDC_FLUSHES_DISABLED;
+    vol_cb_args.args                           = &obj_opt_args;
+
     /* Get the cork status */
-    if (H5VL_object_optional(vol_obj, H5VL_NATIVE_OBJECT_ARE_MDC_FLUSHES_DISABLED, H5P_DATASET_XFER_DEFAULT,
-                             H5_REQUEST_NULL, &loc_params, are_disabled) < 0)
+    if (H5VL_object_optional(vol_obj, &loc_params, &vol_cb_args, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) <
+        0)
         HGOTO_ERROR(H5E_OHDR, H5E_CANTGET, FAIL, "unable to retrieve object's cork status");
 
 done: