Convert dataset callbacks to standard form, for wrapping object IDs, etc.

Also, fix a few attribute issues that I missed.

7 files changed, 513 insertions, 232 deletions

diff --git a/src/H5A.c b/src/H5A.c
index 711897c..13ce41b 100644
--- a/src/H5A.c
+++ b/src/H5A.c
@@ -777,8 +777,7 @@ H5Aget_space(hid_t attr_id)
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, H5I_INVALID_HID, "not an attribute")
 
     /* Get the dataspace */
-    if(H5VL_attr_get(vol_obj->data, vol_obj->plugin->cls, H5VL_ATTR_GET_SPACE, 
-                     H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, &ret_value) < 0)
+    if(H5VL_attr_get(vol_obj, H5VL_ATTR_GET_SPACE, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, &ret_value) < 0)
         HGOTO_ERROR(H5E_ATTR, H5E_CANTGET, H5I_INVALID_HID, "unable to get dataspace of attribute")
 
 done:
@@ -806,7 +805,6 @@ hid_t
 H5Aget_type(hid_t attr_id)
 {
     H5VL_object_t  *vol_obj = NULL;                     /* Attribute object for ID */
-    hbool_t         vol_wrapper_set = FALSE;            /* Whether the VOL object wrapping context was set up */
     hid_t           ret_value   = H5I_INVALID_HID;      /* Return value */
 
     FUNC_ENTER_API(H5I_INVALID_HID)
@@ -816,20 +814,11 @@ H5Aget_type(hid_t attr_id)
     if(NULL == (vol_obj = (H5VL_object_t *)H5I_object_verify(attr_id, H5I_ATTR)))
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, H5I_INVALID_HID, "not an attribute")
 
-    /* Set wrapper info in API context */
-    if(H5VL_set_vol_wrapper(vol_obj->data, vol_obj->plugin) < 0)
-        HGOTO_ERROR(H5E_OHDR, H5E_CANTSET, H5I_INVALID_HID, "can't set VOL wrapper info")
-    vol_wrapper_set = TRUE;
-
     /* Get the datatype */
-    if(H5VL_attr_get(vol_obj->data, vol_obj->plugin->cls, H5VL_ATTR_GET_TYPE, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, &ret_value) < 0)
+    if(H5VL_attr_get(vol_obj, H5VL_ATTR_GET_TYPE, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, &ret_value) < 0)
         HGOTO_ERROR(H5E_ATTR, H5E_CANTGET, H5I_INVALID_HID, "unable to get datatype of attribute")
 
 done:
-    /* Reset object wrapping info in API context */
-    if(vol_wrapper_set && H5VL_reset_vol_wrapper() < 0)
-        HDONE_ERROR(H5E_OHDR, H5E_CANTSET, H5I_INVALID_HID, "can't reset VOL wrapper info")
-
     FUNC_LEAVE_API(ret_value)
 } /* H5Aget_type() */
 
@@ -869,8 +858,7 @@ H5Aget_create_plist(hid_t attr_id)
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, H5I_INVALID_HID, "not an attribute")
 
     /* Get the acpl */
-    if(H5VL_attr_get(vol_obj->data, vol_obj->plugin->cls, H5VL_ATTR_GET_ACPL, 
-                     H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, &ret_value) < 0)
+    if(H5VL_attr_get(vol_obj, H5VL_ATTR_GET_ACPL, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, &ret_value) < 0)
         HGOTO_ERROR(H5E_ATTR, H5E_CANTGET, H5I_INVALID_HID, "unable to get creation property list for attribute")
 
 done:
@@ -920,9 +908,7 @@ H5Aget_name(hid_t attr_id, size_t buf_size, char *buf)
     loc_params.obj_type = H5I_get_type(attr_id);
 
     /* Get the attribute name */
-    if(H5VL_attr_get(vol_obj->data, vol_obj->plugin->cls, H5VL_ATTR_GET_NAME, 
-                     H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, 
-                     loc_params, buf_size, buf, &ret_value) < 0)
+    if(H5VL_attr_get(vol_obj, H5VL_ATTR_GET_NAME, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, loc_params, buf_size, buf, &ret_value) < 0)
         HGOTO_ERROR(H5E_ATTR, H5E_CANTGET, (-1), "unable to get attribute name")
 
 done:
@@ -987,8 +973,7 @@ H5Aget_name_by_idx(hid_t loc_id, const char *obj_name, H5_index_t idx_type,
     loc_params.obj_type = H5I_get_type(loc_id);
 
     /* Get the name */
-    if(H5VL_attr_get(vol_obj->data, vol_obj->plugin->cls, H5VL_ATTR_GET_NAME, 
-                     H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, loc_params, size, name, &ret_value) < 0)
+    if(H5VL_attr_get(vol_obj, H5VL_ATTR_GET_NAME, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, loc_params, size, name, &ret_value) < 0)
         HGOTO_ERROR(H5E_ATTR, H5E_CANTGET, FAIL, "unable to get name")
 
 done:
@@ -1027,8 +1012,7 @@ H5Aget_storage_size(hid_t attr_id)
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, 0, "not an attribute")
 
     /* Get the storage size */
-    if(H5VL_attr_get(vol_obj->data, vol_obj->plugin->cls, H5VL_ATTR_GET_STORAGE_SIZE, 
-                     H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, &ret_value) < 0)
+    if(H5VL_attr_get(vol_obj, H5VL_ATTR_GET_STORAGE_SIZE, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, &ret_value) < 0)
         HGOTO_ERROR(H5E_ATTR, H5E_CANTGET, 0, "unable to get acpl")
 
 done:
@@ -1067,8 +1051,7 @@ H5Aget_info(hid_t attr_id, H5A_info_t *ainfo)
     loc_params.obj_type = H5I_get_type(attr_id);
 
     /* Get the attribute information */
-    if(H5VL_attr_get(vol_obj->data, vol_obj->plugin->cls, H5VL_ATTR_GET_INFO, 
-                     H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, loc_params, ainfo) < 0)
+    if(H5VL_attr_get(vol_obj, H5VL_ATTR_GET_INFO, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, loc_params, ainfo) < 0)
         HGOTO_ERROR(H5E_ATTR, H5E_CANTGET, FAIL, "unable to get attribute info")
 
 done:
@@ -1124,8 +1107,7 @@ H5Aget_info_by_name(hid_t loc_id, const char *obj_name, const char *attr_name,
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "invalid object identifier")
 
     /* Get the attribute information */
-    if(H5VL_attr_get(vol_obj->data, vol_obj->plugin->cls, H5VL_ATTR_GET_INFO, 
-                     H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, loc_params, ainfo, attr_name) < 0)
+    if(H5VL_attr_get(vol_obj, H5VL_ATTR_GET_INFO, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, loc_params, ainfo, attr_name) < 0)
         HGOTO_ERROR(H5E_ATTR, H5E_CANTGET, FAIL, "unable to get attribute info")
 
 done:
@@ -1188,8 +1170,7 @@ H5Aget_info_by_idx(hid_t loc_id, const char *obj_name, H5_index_t idx_type,
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "invalid object identifier")
 
     /* Get the attribute information */
-    if(H5VL_attr_get(vol_obj->data, vol_obj->plugin->cls, H5VL_ATTR_GET_INFO, 
-                     H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, loc_params, ainfo) < 0)
+    if(H5VL_attr_get(vol_obj, H5VL_ATTR_GET_INFO, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, loc_params, ainfo) < 0)
         HGOTO_ERROR(H5E_ATTR, H5E_CANTGET, FAIL, "unable to get attribute info")
 
 done:
diff --git a/src/H5D.c b/src/H5D.c
index 04809cc..5be4c83 100644
--- a/src/H5D.c
+++ b/src/H5D.c
@@ -107,7 +107,6 @@ H5Dcreate2(hid_t loc_id, const char *name, hid_t type_id, hid_t space_id,
     H5VL_object_t      *vol_obj = NULL;                         /* object token of loc_id */
     H5VL_loc_params_t   loc_params;
     H5P_genplist_t     *plist = NULL;                       /* Property list pointer */
-    hbool_t             vol_wrapper_set = FALSE;        /* Whether the VOL object wrapping context was set up */
     hid_t               ret_value = H5I_INVALID_HID;        /* Return value */
 
     FUNC_ENTER_API(H5I_INVALID_HID)
@@ -158,13 +157,8 @@ H5Dcreate2(hid_t loc_id, const char *name, hid_t type_id, hid_t space_id,
     loc_params.type         = H5VL_OBJECT_BY_SELF;
     loc_params.obj_type     = H5I_get_type(loc_id);
 
-    /* Set wrapper info in API context */
-    if(H5VL_set_vol_wrapper(vol_obj->data, vol_obj->plugin) < 0)
-        HGOTO_ERROR(H5E_OHDR, H5E_CANTSET, H5I_INVALID_HID, "can't set VOL wrapper info")
-    vol_wrapper_set = TRUE;
-
     /* Create the dataset */
-    if(NULL == (dset = H5VL_dataset_create(vol_obj->data, loc_params, vol_obj->plugin->cls, name, dcpl_id, dapl_id, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
+    if(NULL == (dset = H5VL_dataset_create(vol_obj, loc_params, name, dcpl_id, dapl_id, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
         HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, H5I_INVALID_HID, "unable to create dataset")
 
     /* Get an atom for the dataset */
@@ -172,12 +166,8 @@ H5Dcreate2(hid_t loc_id, const char *name, hid_t type_id, hid_t space_id,
         HGOTO_ERROR(H5E_DATASET, H5E_CANTREGISTER, H5I_INVALID_HID, "unable to atomize dataset handle")
 
 done:
-    /* Reset object wrapping info in API context */
-    if(vol_wrapper_set && H5VL_reset_vol_wrapper() < 0)
-        HDONE_ERROR(H5E_OHDR, H5E_CANTSET, H5I_INVALID_HID, "can't reset VOL wrapper info")
-
     if(H5I_INVALID_HID == ret_value)
-        if(dset && H5VL_dataset_close(dset, vol_obj->plugin->cls, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
+        if(dset && H5VL_dataset_close(vol_obj, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
             HDONE_ERROR(H5E_DATASET, H5E_CLOSEERROR, H5I_INVALID_HID, "unable to release dataset")
 
     FUNC_LEAVE_API(ret_value)
@@ -259,7 +249,7 @@ H5Dcreate_anon(hid_t loc_id, hid_t type_id, hid_t space_id, hid_t dcpl_id,
     loc_params.obj_type = H5I_get_type(loc_id);
 
     /* Create the dataset */
-    if(NULL == (dset = H5VL_dataset_create(vol_obj->data, loc_params, vol_obj->plugin->cls, NULL, dcpl_id, dapl_id, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
+    if(NULL == (dset = H5VL_dataset_create(vol_obj, loc_params, NULL, dcpl_id, dapl_id, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
         HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, H5I_INVALID_HID, "unable to create dataset")
 
     /* Get an atom for the dataset */
@@ -269,7 +259,7 @@ H5Dcreate_anon(hid_t loc_id, hid_t type_id, hid_t space_id, hid_t dcpl_id,
 done:
     /* Cleanup on failure */
     if(H5I_INVALID_HID == ret_value)
-        if(dset && H5VL_dataset_close (dset, vol_obj->plugin->cls, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
+        if(dset && H5VL_dataset_close(vol_obj, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
             HDONE_ERROR(H5E_DATASET, H5E_CLOSEERROR, H5I_INVALID_HID, "unable to release dataset")
 
     FUNC_LEAVE_API(ret_value)
@@ -297,7 +287,6 @@ H5Dopen2(hid_t loc_id, const char *name, hid_t dapl_id)
     void               *dset = NULL;        /* dset token from VOL plugin */
     H5VL_object_t      *vol_obj = NULL;         /* object token of loc_id */
     H5VL_loc_params_t   loc_params;
-    hbool_t         vol_wrapper_set = FALSE;            /* Whether the VOL object wrapping context was set up */
     hid_t               ret_value   = H5I_INVALID_HID;  /* Return value */
 
     FUNC_ENTER_API(H5I_INVALID_HID)
@@ -321,13 +310,8 @@ H5Dopen2(hid_t loc_id, const char *name, hid_t dapl_id)
     loc_params.type         = H5VL_OBJECT_BY_SELF;
     loc_params.obj_type     = H5I_get_type(loc_id);
 
-    /* Set wrapper info in API context */
-    if(H5VL_set_vol_wrapper(vol_obj->data, vol_obj->plugin) < 0)
-        HGOTO_ERROR(H5E_OHDR, H5E_CANTSET, H5I_INVALID_HID, "can't set VOL wrapper info")
-    vol_wrapper_set = TRUE;
-
     /* Open the dataset */
-    if(NULL == (dset = H5VL_dataset_open(vol_obj->data, loc_params, vol_obj->plugin->cls, name, dapl_id, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
+    if(NULL == (dset = H5VL_dataset_open(vol_obj, loc_params, name, dapl_id, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
         HGOTO_ERROR(H5E_DATASET, H5E_CANTOPENOBJ, H5I_INVALID_HID, "unable to open dataset")
 
     /* Register an atom for the dataset */
@@ -335,13 +319,10 @@ H5Dopen2(hid_t loc_id, const char *name, hid_t dapl_id)
         HGOTO_ERROR(H5E_DATASET, H5E_CANTREGISTER, H5I_INVALID_HID, "can't register dataset atom")
 
 done:
-    /* Reset object wrapping info in API context */
-    if(vol_wrapper_set && H5VL_reset_vol_wrapper() < 0)
-        HDONE_ERROR(H5E_OHDR, H5E_CANTSET, H5I_INVALID_HID, "can't reset VOL wrapper info")
-
     if(H5I_INVALID_HID == ret_value)
-        if(dset && H5VL_dataset_close(dset, vol_obj->plugin->cls, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
+        if(dset && H5VL_dataset_close(vol_obj, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
             HDONE_ERROR(H5E_DATASET, H5E_CLOSEERROR, H5I_INVALID_HID, "unable to release dataset")
+
     FUNC_LEAVE_API(ret_value)
 } /* end H5Dopen2() */
 
@@ -407,7 +388,7 @@ H5Dget_space(hid_t dset_id)
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, H5I_INVALID_HID, "invalid dataset identifier")
 
     /* Get the dataspace */
-    if(H5VL_dataset_get(vol_obj->data, vol_obj->plugin->cls, H5VL_DATASET_GET_SPACE, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, &ret_value) < 0)
+    if(H5VL_dataset_get(vol_obj, H5VL_DATASET_GET_SPACE, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, &ret_value) < 0)
         HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, H5I_INVALID_HID, "unable to get dataspace")
 
 done:
@@ -438,7 +419,7 @@ H5Dget_space_status(hid_t dset_id, H5D_space_status_t *allocation)
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "invalid dataset identifier")
 
     /* Get dataspace status */
-    if((ret_value = H5VL_dataset_get(vol_obj->data, vol_obj->plugin->cls, H5VL_DATASET_GET_SPACE_STATUS, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, allocation)) < 0)
+    if((ret_value = H5VL_dataset_get(vol_obj, H5VL_DATASET_GET_SPACE_STATUS, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, allocation)) < 0)
         HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "unable to get space status")
 
 done:
@@ -463,7 +444,6 @@ hid_t
 H5Dget_type(hid_t dset_id)
 {
     H5VL_object_t  *vol_obj;                           /* Dataset structure    */
-    hbool_t         vol_wrapper_set = FALSE;            /* Whether the VOL object wrapping context was set up */
     hid_t           ret_value = H5I_INVALID_HID;    /* Return value         */
 
     FUNC_ENTER_API(H5I_INVALID_HID)
@@ -473,20 +453,11 @@ H5Dget_type(hid_t dset_id)
     if(NULL == (vol_obj = (H5VL_object_t *)H5I_object_verify(dset_id, H5I_DATASET)))
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, H5I_INVALID_HID, "invalid dataset identifier")
 
-    /* Set wrapper info in API context */
-    if(H5VL_set_vol_wrapper(vol_obj->data, vol_obj->plugin) < 0)
-        HGOTO_ERROR(H5E_OHDR, H5E_CANTSET, H5I_INVALID_HID, "can't set VOL wrapper info")
-    vol_wrapper_set = TRUE;
-
     /* get the datatype */
-    if(H5VL_dataset_get(vol_obj->data, vol_obj->plugin->cls, H5VL_DATASET_GET_TYPE, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, &ret_value) < 0)
+    if(H5VL_dataset_get(vol_obj, H5VL_DATASET_GET_TYPE, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, &ret_value) < 0)
         HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, H5I_INVALID_HID, "unable to get datatype")
 
 done:
-    /* Reset object wrapping info in API context */
-    if(vol_wrapper_set && H5VL_reset_vol_wrapper() < 0)
-        HDONE_ERROR(H5E_OHDR, H5E_CANTSET, H5I_INVALID_HID, "can't reset VOL wrapper info")
-
     FUNC_LEAVE_API(ret_value)
 } /* end H5Dget_type() */
 
@@ -521,7 +492,7 @@ H5Dget_create_plist(hid_t dset_id)
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, H5I_INVALID_HID, "invalid dataset identifier")
 
     /* Get the dataset creation property list */
-    if(H5VL_dataset_get(vol_obj->data, vol_obj->plugin->cls, H5VL_DATASET_GET_DCPL, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, &ret_value) < 0)
+    if(H5VL_dataset_get(vol_obj, H5VL_DATASET_GET_DCPL, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, &ret_value) < 0)
         HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, H5I_INVALID_HID, "unable to get dataset creation properties")
 
 done:
@@ -576,7 +547,7 @@ H5Dget_access_plist(hid_t dset_id)
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, H5I_INVALID_HID, "invalid dataset identifier")
 
     /* Get the dataset access property list */
-    if(H5VL_dataset_get(vol_obj->data, vol_obj->plugin->cls, H5VL_DATASET_GET_DAPL, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, &ret_value) < 0)
+    if(H5VL_dataset_get(vol_obj, H5VL_DATASET_GET_DAPL, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, &ret_value) < 0)
         HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, H5I_INVALID_HID, "unable to get dataset access properties")
 
 done:
@@ -613,7 +584,7 @@ H5Dget_storage_size(hid_t dset_id)
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, 0, "invalid dataset identifier")
 
     /* Get the storage size */
-    if(H5VL_dataset_get(vol_obj->data, vol_obj->plugin->cls, H5VL_DATASET_GET_STORAGE_SIZE, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, &ret_value) < 0)
+    if(H5VL_dataset_get(vol_obj, H5VL_DATASET_GET_STORAGE_SIZE, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, &ret_value) < 0)
         HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, 0, "unable to get storage size")
 
 done:
@@ -646,7 +617,7 @@ H5Dget_offset(hid_t dset_id)
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, HADDR_UNDEF, "invalid dataset identifier")
 
     /* Get the offset */
-    if(H5VL_dataset_get(vol_obj->data, vol_obj->plugin->cls, H5VL_DATASET_GET_OFFSET, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, &ret_value) < 0)
+    if(H5VL_dataset_get(vol_obj, H5VL_DATASET_GET_OFFSET, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, &ret_value) < 0)
         HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, HADDR_UNDEF, "unable to get offset")
 
 done:
@@ -859,7 +830,7 @@ H5Dvlen_get_buf_size(hid_t dataset_id, hid_t type_id, hid_t space_id,
     vlen_bufsize.mspace_id = H5I_INVALID_HID;
 
     /* Get a copy of the dataset's dataspace */
-    if(H5VL_dataset_get(vol_obj->data, vol_obj->plugin->cls, H5VL_DATASET_GET_SPACE, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, &vlen_bufsize.fspace_id) < 0)
+    if(H5VL_dataset_get(vol_obj, H5VL_DATASET_GET_SPACE, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, &vlen_bufsize.fspace_id) < 0)
         HGOTO_ERROR(H5E_DATASET, H5E_CANTCOPY, FAIL, "can't copy dataspace")
 
     /* Create a scalar for the memory dataspace */
@@ -940,7 +911,7 @@ H5Dset_extent(hid_t dset_id, const hsize_t size[])
         HGOTO_ERROR(H5E_DATASET, H5E_CANTSET, FAIL, "can't set collective metadata read info")
 
     /* Set the extent */
-    if ((ret_value = H5VL_dataset_specific(vol_obj->data, vol_obj->plugin->cls, H5VL_DATASET_SET_EXTENT, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, size)) < 0)
+    if ((ret_value = H5VL_dataset_specific(vol_obj, H5VL_DATASET_SET_EXTENT, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, size)) < 0)
         HGOTO_ERROR(H5E_DATASET, H5E_CANTSET, FAIL, "unable to set dataset extent")
 
 done:
@@ -978,7 +949,7 @@ H5Dflush(hid_t dset_id)
      * XXX: Note that we need to pass the ID to the VOL since the H5F_flush_cb_t
      *      callback needs it and that's in the public API.
      */
-    if((ret_value = H5VL_dataset_specific(vol_obj->data, vol_obj->plugin->cls, H5VL_DATASET_FLUSH, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, dset_id)) < 0)
+    if((ret_value = H5VL_dataset_specific(vol_obj, H5VL_DATASET_FLUSH, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, dset_id)) < 0)
         HGOTO_ERROR(H5E_DATASET, H5E_CANTFLUSH, FAIL, "unable to flush dataset")
 
 done:
@@ -999,7 +970,6 @@ herr_t
 H5Drefresh(hid_t dset_id)
 {
     H5VL_object_t  *vol_obj;                   /* Dataset for this operation   */
-    hbool_t             vol_wrapper_set = FALSE;        /* Whether the VOL object wrapping context was set up */
     herr_t          ret_value = SUCCEED;    /* Return value                 */
 
     FUNC_ENTER_API(FAIL)
@@ -1013,20 +983,11 @@ H5Drefresh(hid_t dset_id)
     if(H5CX_set_loc(dset_id) < 0)
         HGOTO_ERROR(H5E_DATASET, H5E_CANTSET, FAIL, "can't set collective metadata read info")
 
-    /* Set wrapper info in API context */
-    if(H5VL_set_vol_wrapper(vol_obj->data, vol_obj->plugin) < 0)
-        HGOTO_ERROR(H5E_DATASET, H5E_CANTSET, FAIL, "can't set VOL wrapper info")
-    vol_wrapper_set = TRUE;
-
     /* Refresh the dataset object */
-    if((ret_value = H5VL_dataset_specific(vol_obj->data, vol_obj->plugin->cls, H5VL_DATASET_REFRESH, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, dset_id)) < 0)
+    if((ret_value = H5VL_dataset_specific(vol_obj, H5VL_DATASET_REFRESH, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, dset_id)) < 0)
         HGOTO_ERROR(H5E_DATASET, H5E_CANTLOAD, FAIL, "unable to refresh dataset")
 
 done:
-    /* Reset object wrapping info in API context */
-    if(vol_wrapper_set && H5VL_reset_vol_wrapper() < 0)
-        HDONE_ERROR(H5E_DATASET, H5E_CANTSET, FAIL, "can't reset VOL wrapper info")
-
     FUNC_LEAVE_API(ret_value)
 } /* end H5Drefresh() */
 
@@ -1066,7 +1027,7 @@ H5Dformat_convert(hid_t dset_id)
         HGOTO_ERROR(H5E_DATASET, H5E_CANTSET, FAIL, "can't set collective metadata read info")
 
     /* Convert the dataset */
-    if(H5VL_dataset_optional(vol_obj->data, vol_obj->plugin->cls, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, H5VL_DATASET_FORMAT_CONVERT) < 0)
+    if(H5VL_dataset_optional(vol_obj, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, H5VL_DATASET_FORMAT_CONVERT) < 0)
         HGOTO_ERROR(H5E_DATASET, H5E_INTERNAL, FAIL, "can't convert dataset format")
 
 done:
@@ -1102,7 +1063,7 @@ H5Dget_chunk_index_type(hid_t dset_id, H5D_chunk_index_t *idx_type)
         HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "idx_type parameter cannot be NULL")
 
     /* Get the chunk indexing type */
-    if(H5VL_dataset_optional(vol_obj->data, vol_obj->plugin->cls, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, H5VL_DATASET_GET_CHUNK_INDEX_TYPE, idx_type) < 0)
+    if(H5VL_dataset_optional(vol_obj, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, H5VL_DATASET_GET_CHUNK_INDEX_TYPE, idx_type) < 0)
         HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "can't get chunk index type")
 
 done:
@@ -1143,7 +1104,7 @@ H5Dget_chunk_storage_size(hid_t dset_id, const hsize_t *offset, hsize_t *chunk_n
         HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "chunk_nbytes parameter cannot be NULL")
 
     /* Get the dataset creation property list */
-    if(H5VL_dataset_optional(vol_obj->data, vol_obj->plugin->cls, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, H5VL_DATASET_GET_CHUNK_STORAGE_SIZE, offset, chunk_nbytes) < 0)
+    if(H5VL_dataset_optional(vol_obj, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, H5VL_DATASET_GET_CHUNK_STORAGE_SIZE, offset, chunk_nbytes) < 0)
         HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "can't get storage size of chunk")
 
 done:
diff --git a/src/H5Ddeprec.c b/src/H5Ddeprec.c
index 426e33c..87b3d8d 100644
--- a/src/H5Ddeprec.c
+++ b/src/H5Ddeprec.c
@@ -161,7 +161,7 @@ H5Dcreate1(hid_t loc_id, const char *name, hid_t type_id, hid_t space_id,
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, H5I_INVALID_HID, "invalid location identifier")
 
     /* Create the dataset through the VOL */
-    if(NULL == (dset = H5VL_dataset_create(vol_obj->data, loc_params, vol_obj->plugin->cls, name, dcpl_id, H5P_DATASET_ACCESS_DEFAULT, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
+    if(NULL == (dset = H5VL_dataset_create(vol_obj, loc_params, name, dcpl_id, H5P_DATASET_ACCESS_DEFAULT, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
         HGOTO_ERROR(H5E_DATASET, H5E_CANTINIT, H5I_INVALID_HID, "unable to create dataset")
 
     /* Get an atom for the dataset */
@@ -170,7 +170,7 @@ H5Dcreate1(hid_t loc_id, const char *name, hid_t type_id, hid_t space_id,
 
 done:
     if (H5I_INVALID_HID == ret_value)
-        if(dset && H5VL_dataset_close(dset, vol_obj->plugin->cls, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
+        if(dset && H5VL_dataset_close(vol_obj, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
             HDONE_ERROR(H5E_DATASET, H5E_CLOSEERROR, H5I_INVALID_HID, "unable to release dataset")
 
     FUNC_LEAVE_API(ret_value)
@@ -220,7 +220,7 @@ H5Dopen1(hid_t loc_id, const char *name)
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, H5I_INVALID_HID, "invalid location identifier")
 
     /* Open the dataset */
-    if(NULL == (dset = H5VL_dataset_open(vol_obj->data, loc_params, vol_obj->plugin->cls, name, H5P_DATASET_ACCESS_DEFAULT, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
+    if(NULL == (dset = H5VL_dataset_open(vol_obj, loc_params, name, H5P_DATASET_ACCESS_DEFAULT, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
         HGOTO_ERROR(H5E_DATASET, H5E_CANTOPENOBJ, H5I_INVALID_HID, "unable to open dataset")
 
     /* Get an atom for the dataset */
@@ -229,7 +229,7 @@ H5Dopen1(hid_t loc_id, const char *name)
 
 done:
     if(H5I_INVALID_HID == ret_value)
-        if(dset && H5VL_dataset_close(dset, vol_obj->plugin->cls, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
+        if(dset && H5VL_dataset_close(vol_obj, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
             HDONE_ERROR(H5E_DATASET, H5E_CLOSEERROR, H5I_INVALID_HID, "unable to release dataset")
 
     FUNC_LEAVE_API(ret_value)
@@ -273,7 +273,7 @@ H5Dextend(hid_t dset_id, const hsize_t size[])
         HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "no size specified")
 
     /* Get the dataspace pointer for the dataset */
-    if(H5VL_dataset_get(vol_obj->data, vol_obj->plugin->cls, H5VL_DATASET_GET_SPACE, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, &sid) < 0)
+    if(H5VL_dataset_get(vol_obj, H5VL_DATASET_GET_SPACE, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, &sid) < 0)
         HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "unable to get dataspace")
     if(H5I_INVALID_HID == sid)
         HGOTO_ERROR(H5E_DATASET, H5E_CANTGET, FAIL, "received an invalid dataspace from the dataset")
@@ -303,7 +303,7 @@ H5Dextend(hid_t dset_id, const hsize_t size[])
         HGOTO_ERROR(H5E_DATASET, H5E_CANTSET, FAIL, "can't set collective metadata read info")
 
     /* Increase size */
-    if ((ret_value = H5VL_dataset_specific(vol_obj->data, vol_obj->plugin->cls, H5VL_DATASET_SET_EXTENT, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, dset_dims)) < 0)
+    if ((ret_value = H5VL_dataset_specific(vol_obj, H5VL_DATASET_SET_EXTENT, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, dset_dims)) < 0)
         HGOTO_ERROR(H5E_DATASET, H5E_CANTSET, FAIL, "unable to extend dataset")
 
 done:
diff --git a/src/H5Dint.c b/src/H5Dint.c
index 44a9d88..67889e6 100644
--- a/src/H5Dint.c
+++ b/src/H5Dint.c
@@ -300,7 +300,7 @@ H5D__close_cb(H5VL_object_t *dset_vol_obj)
     HDassert(dset_vol_obj);
 
     /* Close the dataset */
-    if(H5VL_dataset_close(dset_vol_obj->data, dset_vol_obj->plugin->cls, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
+    if(H5VL_dataset_close(dset_vol_obj, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
         HGOTO_ERROR(H5E_DATASET, H5E_CLOSEERROR, FAIL, "unable to close dataset");
 
 done:
@@ -2459,10 +2459,7 @@ H5D__vlen_get_buf_size(void H5_ATTR_UNUSED *elem, hid_t type_id,
         HGOTO_ERROR(H5E_DATASET, H5E_CANTCREATE, FAIL, "can't select point")
 
     /* Read in the point (with the custom VL memory allocator) */
-    if(H5VL_dataset_read(vol_obj->data, vol_obj->plugin->cls, 
-                         type_id, vlen_bufsize->mspace_id, 
-                         vlen_bufsize->fspace_id, H5P_DATASET_XFER_DEFAULT, 
-                         vlen_bufsize->fl_tbuf, H5_REQUEST_NULL) < 0)
+    if(H5VL_dataset_read(vol_obj, type_id, vlen_bufsize->mspace_id, vlen_bufsize->fspace_id, H5P_DATASET_XFER_DEFAULT, vlen_bufsize->fl_tbuf, H5_REQUEST_NULL) < 0)
         HGOTO_ERROR(H5E_DATASET, H5E_READERROR, FAIL, "can't read point")
 
 done:
diff --git a/src/H5Dio.c b/src/H5Dio.c
index b30e0c9..ed43f8f 100644
--- a/src/H5Dio.c
+++ b/src/H5Dio.c
@@ -191,8 +191,7 @@ H5Dread(hid_t dset_id, hid_t mem_type_id, hid_t mem_space_id,
     H5CX_set_dxpl(dxpl_id);
 
     /* Read the data */
-    if ((ret_value = H5VL_dataset_read(vol_obj->data, vol_obj->plugin->cls, mem_type_id, mem_space_id, 
-                                      file_space_id, dxpl_id, buf, H5_REQUEST_NULL)) < 0)
+    if ((ret_value = H5VL_dataset_read(vol_obj, mem_type_id, mem_space_id, file_space_id, dxpl_id, buf, H5_REQUEST_NULL)) < 0)
         HGOTO_ERROR(H5E_DATASET, H5E_READERROR, FAIL, "can't read data")
 
 done:
@@ -243,8 +242,7 @@ H5Dread_chunk(hid_t dset_id, hid_t dxpl_id, const hsize_t *offset, uint32_t *fil
     H5CX_set_dxpl(dxpl_id);
 
     /* Read the raw chunk */
-    if (H5VL_dataset_optional(vol_obj->data, vol_obj->plugin->cls, dxpl_id,
-            H5_REQUEST_NULL, H5VL_DATASET_CHUNK_READ, offset, filters, buf) < 0)
+    if (H5VL_dataset_optional(vol_obj, dxpl_id, H5_REQUEST_NULL, H5VL_DATASET_CHUNK_READ, offset, filters, buf) < 0)
         HGOTO_ERROR(H5E_DATASET, H5E_READERROR, FAIL, "can't read unprocessed chunk data")
 
 done:
@@ -315,8 +313,7 @@ H5Dwrite(hid_t dset_id, hid_t mem_type_id, hid_t mem_space_id,
     H5CX_set_dxpl(dxpl_id);
 
     /* Write the data */
-    if ((ret_value = H5VL_dataset_write(vol_obj->data, vol_obj->plugin->cls, mem_type_id, mem_space_id, 
-                                       file_space_id, dxpl_id, buf, H5_REQUEST_NULL)) < 0)
+    if ((ret_value = H5VL_dataset_write(vol_obj, mem_type_id, mem_space_id, file_space_id, dxpl_id, buf, H5_REQUEST_NULL)) < 0)
         HGOTO_ERROR(H5E_DATASET, H5E_WRITEERROR, FAIL, "can't write data")
 
 done:
@@ -373,8 +370,7 @@ H5Dwrite_chunk(hid_t dset_id, hid_t dxpl_id, uint32_t filters, const hsize_t *of
     H5CX_set_dxpl(dxpl_id);
 
     /* Write chunk */
-    if (H5VL_dataset_optional(vol_obj->data, vol_obj->plugin->cls, dxpl_id,
-            H5_REQUEST_NULL, H5VL_DATASET_CHUNK_WRITE, filters, offset, data_size_32, buf) < 0)
+    if (H5VL_dataset_optional(vol_obj, dxpl_id, H5_REQUEST_NULL, H5VL_DATASET_CHUNK_WRITE, filters, offset, data_size_32, buf) < 0)
         HGOTO_ERROR(H5E_DATASET, H5E_WRITEERROR, FAIL, "can't write unprocessed chunk data")
 
 done:
diff --git a/src/H5VLcallback.c b/src/H5VLcallback.c
index 9610f6a..a543379 100644
--- a/src/H5VLcallback.c
+++ b/src/H5VLcallback.c
@@ -62,10 +62,12 @@ static void *H5VL__attr_create(void *obj, H5VL_loc_params_t loc_params,
 static void *H5VL__attr_open(void *obj, H5VL_loc_params_t loc_params,
     const H5VL_class_t *cls, const char *name, hid_t aapl_id, hid_t dxpl_id,
     void **req);
-static herr_tH5VL__attr_read(void *obj, const H5VL_class_t *cls, hid_t mem_type_id,
+static herr_t H5VL__attr_read(void *obj, const H5VL_class_t *cls, hid_t mem_type_id,
     void *buf, hid_t dxpl_id, void **req);
-static herr_t H5VL___attr_write(void *obj, const H5VL_class_t *cls, hid_t mem_type_id,
+static herr_t H5VL__attr_write(void *obj, const H5VL_class_t *cls, hid_t mem_type_id,
     const void *buf, hid_t dxpl_id, void **req);
+static herr_t H5VL__attr_get(void *obj, const H5VL_class_t *cls, H5VL_attr_get_t get_type, 
+    hid_t dxpl_id, void **req, va_list arguments);
 static herr_t H5VL__attr_specific(void *obj, H5VL_loc_params_t loc_params,
     const H5VL_class_t *cls, H5VL_attr_specific_t specific_type, hid_t dxpl_id,
     void **req, va_list arguments);
@@ -73,6 +75,26 @@ static herr_t H5VL__attr_optional(void *obj, const H5VL_class_t *cls, hid_t dxpl
     void **req, va_list arguments);
 static herr_t H5VL__attr_close(void *obj, const H5VL_class_t *cls, hid_t dxpl_id,
     void **req);
+static void *H5VL__dataset_create(void *obj, H5VL_loc_params_t loc_params,
+    const H5VL_class_t *cls, const char *name, hid_t dcpl_id, hid_t dapl_id,
+    hid_t dxpl_id, void **req);
+static void *H5VL__dataset_open(void *obj, 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 plist_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 plist_id,
+    const void *buf, void **req);
+static herr_t H5VL__dataset_get(void *obj, const H5VL_class_t *cls, H5VL_dataset_get_t get_type, 
+    hid_t dxpl_id, void **req, va_list arguments);
+static herr_t H5VL__dataset_specific(void *obj, const H5VL_class_t *cls,
+    H5VL_dataset_specific_t specific_type, hid_t dxpl_id, void **req, va_list arguments);
+static herr_t H5VL__dataset_optional(void *obj, const H5VL_class_t *cls,
+    hid_t dxpl_id, void **req, va_list arguments);
+static herr_t H5VL__dataset_close(void *obj, const H5VL_class_t *cls, hid_t dxpl_id,
+    void **req);
 
 
 /*********************/
@@ -814,7 +836,7 @@ H5VL_attr_open(const H5VL_object_t *vol_obj, H5VL_loc_params_t loc_params,
 
     /* Set wrapper info in API context */
     if(H5VL_set_vol_wrapper(vol_obj->data, vol_obj->plugin) < 0)
-        HGOTO_ERROR(H5E_VOL, H5E_CANTSET, FAIL, "can't set VOL wrapper info")
+        HGOTO_ERROR(H5E_VOL, H5E_CANTSET, NULL, "can't set VOL wrapper info")
     vol_wrapper_set = TRUE;
 
     /* Call the corresponding internal VOL routine */
@@ -824,7 +846,7 @@ H5VL_attr_open(const H5VL_object_t *vol_obj, H5VL_loc_params_t loc_params,
 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")
+        HDONE_ERROR(H5E_VOL, H5E_CANTRESET, NULL, "can't reset VOL wrapper info")
 
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5VL_attr_open() */
@@ -978,7 +1000,7 @@ done:
  *-------------------------------------------------------------------------
  */
 static herr_t
-H5VL___attr_write(void *obj, const H5VL_class_t *cls, hid_t mem_type_id, const void *buf, 
+H5VL__attr_write(void *obj, const H5VL_class_t *cls, hid_t mem_type_id, const void *buf, 
     hid_t dxpl_id, void **req)
 {
     herr_t ret_value = SUCCEED;         /* Return value */
@@ -1070,6 +1092,37 @@ done:
 
 
 /*-------------------------------------------------------------------------
+ * Function:	H5VL__attr_get
+ *
+ * Purpose:	Get specific information about the attribute through the VOL
+ *
+ * Return:      Success:    Non-negative
+ *              Failure:    Negative
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5VL__attr_get(void *obj, const H5VL_class_t *cls, H5VL_attr_get_t get_type, 
+    hid_t dxpl_id, void **req, va_list arguments)
+{
+    herr_t ret_value = SUCCEED;         /* Return value */
+
+    FUNC_ENTER_STATIC
+
+    /* Check if the corresponding VOL callback exists */
+    if(NULL == cls->attr_cls.get)
+        HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL plugin has no 'attr get' method")
+
+    /* Call the corresponding VOL callback */
+    if((cls->attr_cls.get)(obj, get_type, dxpl_id, req, arguments) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTGET, FAIL, "attribute get failed")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5VL__attr_get() */
+
+
+/*-------------------------------------------------------------------------
  * Function:	H5VL_attr_get
  *
  * Purpose:	Get specific information about the attribute through the VOL
@@ -1080,30 +1133,36 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5VL_attr_get(void *obj, const H5VL_class_t *cls, H5VL_attr_get_t get_type, 
+H5VL_attr_get(const H5VL_object_t *vol_obj, H5VL_attr_get_t get_type, 
     hid_t dxpl_id, void **req, ...)
 {
     va_list arguments;                  /* Argument list passed from the API call */
     hbool_t arg_started = FALSE;        /* Whether the va_list has been started */
+    hbool_t vol_wrapper_set = FALSE;    /* Whether the VOL object wrapping context was set up */
     herr_t ret_value = SUCCEED;         /* Return value */
 
     FUNC_ENTER_NOAPI(FAIL)
 
-    /* Check if the corresponding VOL callback exists */
-    if(NULL == cls->attr_cls.get)
-        HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL plugin has no 'attr get' method")
+    /* Set wrapper info in API context */
+    if(H5VL_set_vol_wrapper(vol_obj->data, vol_obj->plugin) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTSET, FAIL, "can't set VOL wrapper info")
+    vol_wrapper_set = TRUE;
 
-    /* Call the corresponding VOL callback */
+    /* Call the corresponding internal VOL routine */
     va_start(arguments, req);
     arg_started = TRUE;
-    if((cls->attr_cls.get)(obj, get_type, dxpl_id, req, arguments) < 0)
-        HGOTO_ERROR(H5E_VOL, H5E_CANTGET, FAIL, "get failed")
+    if(H5VL__attr_get(vol_obj->data, vol_obj->plugin->cls, get_type, dxpl_id, req, arguments) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTGET, FAIL, "attribute get failed")
 
 done:
     /* End access to the va_list, if we started it */
     if(arg_started)
         va_end(arguments);
 
+    /* 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_attr_get() */
 
@@ -1134,12 +1193,8 @@ H5VLattr_get(void *obj, hid_t plugin_id, H5VL_attr_get_t get_type, hid_t dxpl_id
     if(NULL == (cls = (H5VL_class_t *)H5I_object_verify(plugin_id, H5I_VOL)))
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a VOL plugin ID")
 
-    /* Check if the corresponding VOL callback exists */
-    if(NULL == cls->attr_cls.get)
-        HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL plugin has no `attr get' method")
-
-    /* Bypass the H5VLint layer, calling the VOL callback directly */
-    if((cls->attr_cls.get)(obj, get_type, dxpl_id, req, arguments) < 0)
+    /* Call the corresponding internal VOL routine */
+    if(H5VL__attr_get(obj, cls, get_type, dxpl_id, req, arguments) < 0)
         HGOTO_ERROR(H5E_VOL, H5E_CANTGET, FAIL, "Unable to get attribute information")
 
 done:
@@ -1270,7 +1325,7 @@ done:
  *
  *-------------------------------------------------------------------------
  */
-herr_t
+static herr_t
 H5VL__attr_optional(void *obj, const H5VL_class_t *cls, hid_t dxpl_id,
     void **req, va_list arguments)
 {
@@ -1302,8 +1357,7 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5VL_attr_optional(const H5VL_object_t *vol_obj, const H5VL_class_t *cls,
-    hid_t dxpl_id, void **req, ...)
+H5VL_attr_optional(const H5VL_object_t *vol_obj, hid_t dxpl_id, void **req, ...)
 {
     va_list arguments;                  /* Argument list passed from the API call */
     hbool_t arg_started = FALSE;        /* Whether the va_list has been started */
@@ -1446,7 +1500,7 @@ H5VLattr_close(void *obj, hid_t plugin_id, hid_t dxpl_id, void **req)
     herr_t ret_value = SUCCEED;         /* Return value */
 
     FUNC_ENTER_API_NOINIT
-    H5TRACE4("e", "*xii**x", attr, plugin_id, dxpl_id, req);
+    H5TRACE4("e", "*xii**x", obj, plugin_id, dxpl_id, req);
 
     /* Check args and get class pointer */
     if(NULL == obj)
@@ -1464,7 +1518,7 @@ done:
 
 
 /*-------------------------------------------------------------------------
- * Function:	H5VL_dataset_create
+ * Function:	H5VL__dataset_create
  *
  * Purpose:	Creates a dataset through the VOL
  *
@@ -1473,13 +1527,13 @@ done:
  *
  *-------------------------------------------------------------------------
  */
-void *
-H5VL_dataset_create(void *obj, H5VL_loc_params_t loc_params, const H5VL_class_t *cls, const char *name, 
-    hid_t dcpl_id, hid_t dapl_id, hid_t dxpl_id, void **req)
+static void *
+H5VL__dataset_create(void *obj, H5VL_loc_params_t loc_params, const H5VL_class_t *cls,
+    const char *name, hid_t dcpl_id, hid_t dapl_id, hid_t dxpl_id, void **req)
 {
     void *ret_value = NULL;     /* Return value */
 
-    FUNC_ENTER_NOAPI(NULL)
+    FUNC_ENTER_STATIC
 
     /* Check if the corresponding VOL callback exists */
     if(NULL == cls->dataset_cls.create)
@@ -1491,6 +1545,43 @@ H5VL_dataset_create(void *obj, H5VL_loc_params_t loc_params, const H5VL_class_t
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5VL__dataset_create() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5VL_dataset_create
+ *
+ * Purpose:	Creates a dataset through the VOL
+ *
+ * Return:      Success: Pointer to new dataset
+ *		Failure: NULL
+ *
+ *-------------------------------------------------------------------------
+ */
+void *
+H5VL_dataset_create(const H5VL_object_t *vol_obj, H5VL_loc_params_t loc_params,
+    const char *name, hid_t dcpl_id, hid_t dapl_id, hid_t dxpl_id, void **req)
+{
+    hbool_t vol_wrapper_set = FALSE;    /* Whether the VOL object wrapping context was set up */
+    void *ret_value = NULL;             /* Return value */
+
+    FUNC_ENTER_NOAPI(NULL)
+
+    /* Set wrapper info in API context */
+    if(H5VL_set_vol_wrapper(vol_obj->data, vol_obj->plugin) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTSET, NULL, "can't set VOL wrapper info")
+    vol_wrapper_set = TRUE;
+
+    /* Call the corresponding internal VOL routine */
+    if(NULL == (ret_value = H5VL__dataset_create(vol_obj->data, loc_params, vol_obj->plugin->cls, name, dcpl_id, dapl_id, dxpl_id, req)))
+        HGOTO_ERROR(H5E_VOL, H5E_CANTCREATE, NULL, "create failed")
+
+done:
+    /* Reset object wrapping info in API context */
+    if(vol_wrapper_set && H5VL_reset_vol_wrapper() < 0)
+        HDONE_ERROR(H5E_VOL, H5E_CANTRESET, NULL, "can't reset VOL wrapper info")
+
+    FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5VL_dataset_create() */
 
 
@@ -1505,8 +1596,8 @@ done:
  *-------------------------------------------------------------------------
  */
 void *
-H5VLdataset_create(void *obj, H5VL_loc_params_t loc_params, hid_t plugin_id, const char *name,
-    hid_t dcpl_id, hid_t dapl_id, hid_t dxpl_id, void **req)
+H5VLdataset_create(void *obj, H5VL_loc_params_t loc_params, hid_t plugin_id,
+    const char *name, hid_t dcpl_id, hid_t dapl_id, hid_t dxpl_id, void **req)
 {
     H5VL_class_t *cls;                  /* VOL plugin's class struct */
     void *ret_value = NULL;             /* Return value */
@@ -1522,7 +1613,7 @@ H5VLdataset_create(void *obj, H5VL_loc_params_t loc_params, hid_t plugin_id, con
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, NULL, "not a VOL plugin ID")
 
     /* Call the corresponding internal VOL routine */
-    if(NULL == (ret_value = H5VL_dataset_create(obj, loc_params, cls, name, dcpl_id, dapl_id, dxpl_id, req)))
+    if(NULL == (ret_value = H5VL__dataset_create(obj, loc_params, cls, name, dcpl_id, dapl_id, dxpl_id, req)))
         HGOTO_ERROR(H5E_VOL, H5E_CANTCREATE, NULL, "unable to create dataset")
 
 done:
@@ -1531,7 +1622,7 @@ done:
 
 
 /*-------------------------------------------------------------------------
- * Function:	H5VL_dataset_open
+ * Function:	H5VL__dataset_open
  *
  * Purpose:	Opens a dataset through the VOL
  *
@@ -1540,13 +1631,13 @@ done:
  *
  *-------------------------------------------------------------------------
  */
-void *
-H5VL_dataset_open(void *obj, H5VL_loc_params_t loc_params, const H5VL_class_t *cls, const char *name, 
+static void *
+H5VL__dataset_open(void *obj, H5VL_loc_params_t loc_params, const H5VL_class_t *cls, const char *name, 
     hid_t dapl_id, hid_t dxpl_id, void **req)
 {
-    void *ret_value = NULL; /* Return value */
+    void *ret_value = NULL;             /* Return value */
 
-    FUNC_ENTER_NOAPI(NULL)
+    FUNC_ENTER_STATIC
 
     /* Check if the corresponding VOL callback exists */
     if(NULL == cls->dataset_cls.open)
@@ -1558,6 +1649,43 @@ H5VL_dataset_open(void *obj, H5VL_loc_params_t loc_params, const H5VL_class_t *c
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5VL__dataset_open() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5VL_dataset_open
+ *
+ * Purpose:	Opens a dataset through the VOL
+ *
+ * Return:      Success: Pointer to dataset 
+ *		Failure: NULL
+ *
+ *-------------------------------------------------------------------------
+ */
+void *
+H5VL_dataset_open(const H5VL_object_t *vol_obj, H5VL_loc_params_t loc_params,
+    const char *name, hid_t dapl_id, hid_t dxpl_id, void **req)
+{
+    hbool_t vol_wrapper_set = FALSE;    /* Whether the VOL object wrapping context was set up */
+    void *ret_value = NULL;             /* Return value */
+
+    FUNC_ENTER_NOAPI(NULL)
+
+    /* Set wrapper info in API context */
+    if(H5VL_set_vol_wrapper(vol_obj->data, vol_obj->plugin) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTSET, NULL, "can't set VOL wrapper info")
+    vol_wrapper_set = TRUE;
+
+    /* Call the corresponding internal VOL routine */
+    if(NULL == (ret_value = H5VL__dataset_open(vol_obj->data, loc_params, vol_obj->plugin->cls, name, dapl_id, dxpl_id, req)))
+        HGOTO_ERROR(H5E_VOL, H5E_CANTOPENOBJ, NULL, "dataset open failed")
+
+done:
+    /* Reset object wrapping info in API context */
+    if(vol_wrapper_set && H5VL_reset_vol_wrapper() < 0)
+        HDONE_ERROR(H5E_VOL, H5E_CANTRESET, NULL, "can't reset VOL wrapper info")
+
+    FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5VL_dataset_open() */
 
 
@@ -1572,8 +1700,8 @@ done:
  *-------------------------------------------------------------------------
  */
 void *
-H5VLdataset_open(void *obj, H5VL_loc_params_t loc_params, hid_t plugin_id, const char *name,
-    hid_t dapl_id, hid_t dxpl_id, void **req)
+H5VLdataset_open(void *obj, H5VL_loc_params_t loc_params, hid_t plugin_id,
+    const char *name, hid_t dapl_id, hid_t dxpl_id, void **req)
 {
     H5VL_class_t *cls;                  /* VOL plugin's class struct */
     void *ret_value = NULL;             /* Return value */
@@ -1589,7 +1717,7 @@ H5VLdataset_open(void *obj, H5VL_loc_params_t loc_params, hid_t plugin_id, const
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, NULL, "not a VOL plugin ID")
 
     /* Call the corresponding internal VOL routine */
-    if(NULL == (ret_value = H5VL_dataset_open(obj, loc_params, cls, name, dapl_id, dxpl_id, req)))
+    if(NULL == (ret_value = H5VL__dataset_open(obj, loc_params, cls, name, dapl_id, dxpl_id, req)))
         HGOTO_ERROR(H5E_VOL, H5E_CANTOPENOBJ, NULL, "unable to open dataset")
 
 done:
@@ -1598,7 +1726,7 @@ done:
 
 
 /*-------------------------------------------------------------------------
- * Function:	H5VL_dataset_read
+ * Function:	H5VL__dataset_read
  *
  * Purpose:	Reads data from dataset through the VOL
 *
@@ -1607,24 +1735,62 @@ done:
  *
  *-------------------------------------------------------------------------
  */
-herr_t 
-H5VL_dataset_read(void *dset, const H5VL_class_t *cls, hid_t mem_type_id,
+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 plist_id, void *buf,
     void **req)
 {
     herr_t ret_value = SUCCEED;         /* Return value */
 
-    FUNC_ENTER_NOAPI(FAIL)
+    FUNC_ENTER_STATIC
 
     /* Check if the corresponding VOL callback exists */
     if(NULL == cls->dataset_cls.read)
         HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL plugin has no 'dataset read' method")
 
     /* Call the corresponding VOL callback */
-    if((cls->dataset_cls.read)(dset, mem_type_id, mem_space_id, file_space_id, plist_id, buf, req) < 0)
-        HGOTO_ERROR(H5E_VOL, H5E_READERROR, FAIL, "read failed")
+    if((cls->dataset_cls.read)(obj, mem_type_id, mem_space_id, file_space_id, plist_id, buf, req) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_READERROR, FAIL, "dataset read failed")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5VL__dataset_read() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5VL_dataset_read
+ *
+ * Purpose:	Reads data from dataset through the VOL
+*
+ * Return:      Success:    Non-negative
+ *              Failure:    Negative
+ *
+ *-------------------------------------------------------------------------
+ */
+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 plist_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 */
+
+    FUNC_ENTER_NOAPI(FAIL)
+
+    /* Set wrapper info in API context */
+    if(H5VL_set_vol_wrapper(vol_obj->data, vol_obj->plugin) < 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(vol_obj->data, vol_obj->plugin->cls, mem_type_id, mem_space_id, file_space_id, plist_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() */
 
@@ -1640,24 +1806,24 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5VLdataset_read(void *dset, hid_t plugin_id, hid_t mem_type_id, hid_t mem_space_id,
+H5VLdataset_read(void *obj, hid_t plugin_id, hid_t mem_type_id, hid_t mem_space_id,
     hid_t file_space_id, hid_t plist_id, void *buf, void **req)
 {
     H5VL_class_t *cls;                  /* VOL plugin's class struct */
     herr_t ret_value = SUCCEED;         /* Return value */
 
     FUNC_ENTER_API_NOINIT
-    H5TRACE8("e", "*xiiiii*x**x", dset, plugin_id, mem_type_id, mem_space_id,
+    H5TRACE8("e", "*xiiiii*x**x", obj, plugin_id, mem_type_id, mem_space_id,
              file_space_id, plist_id, buf, req);
 
     /* Check args and get class pointer */
-    if(NULL == dset)
+    if(NULL == obj)
         HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "invalid object")
     if(NULL == (cls = (H5VL_class_t *)H5I_object_verify(plugin_id, H5I_VOL)))
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a VOL plugin ID")
 
     /* Call the corresponding internal VOL routine */
-    if(H5VL_dataset_read(dset, cls, mem_type_id, mem_space_id, file_space_id, plist_id, buf, req) < 0)
+    if(H5VL__dataset_read(obj, cls, mem_type_id, mem_space_id, file_space_id, plist_id, buf, req) < 0)
         HGOTO_ERROR(H5E_VOL, H5E_CANTINIT, FAIL, "unable to read dataset")
 
 done:
@@ -1666,7 +1832,7 @@ done:
 
 
 /*-------------------------------------------------------------------------
- * Function:	H5VL_dataset_write
+ * Function:	H5VL__dataset_write
  *
  * Purpose:	Writes data from dataset through the VOL
  *
@@ -1675,24 +1841,62 @@ done:
  *
  *-------------------------------------------------------------------------
  */
-herr_t 
-H5VL_dataset_write(void *dset, const H5VL_class_t *cls, hid_t mem_type_id,
+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 plist_id, const void *buf,
     void **req)
 {
     herr_t ret_value = SUCCEED;         /* Return value */
 
-    FUNC_ENTER_NOAPI(FAIL)
+    FUNC_ENTER_STATIC
 
     /* Check if the corresponding VOL callback exists */
     if(NULL == cls->dataset_cls.write)
         HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL plugin has no 'dataset write' method")
 
     /* Call the corresponding VOL callback */
-    if((cls->dataset_cls.write)(dset, mem_type_id, mem_space_id, file_space_id, plist_id, buf, req) < 0)
-        HGOTO_ERROR(H5E_VOL, H5E_WRITEERROR, FAIL, "write failed")
+    if((cls->dataset_cls.write)(obj, mem_type_id, mem_space_id, file_space_id, plist_id, buf, req) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_WRITEERROR, FAIL, "dataset write failed")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5VL__dataset_write() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5VL_dataset_write
+ *
+ * Purpose:	Writes data from dataset through the VOL
+ *
+ * Return:      Success:    Non-negative
+ *              Failure:    Negative
+ *
+ *-------------------------------------------------------------------------
+ */
+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 plist_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 */
+
+    FUNC_ENTER_NOAPI(FAIL)
+
+    /* Set wrapper info in API context */
+    if(H5VL_set_vol_wrapper(vol_obj->data, vol_obj->plugin) < 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(vol_obj->data, vol_obj->plugin->cls, mem_type_id, mem_space_id, file_space_id, plist_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() */
 
@@ -1708,24 +1912,24 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5VLdataset_write(void *dset, hid_t plugin_id, hid_t mem_type_id, hid_t mem_space_id,
+H5VLdataset_write(void *obj, hid_t plugin_id, hid_t mem_type_id, hid_t mem_space_id,
     hid_t file_space_id, hid_t plist_id, const void *buf, void **req)
 {
     H5VL_class_t *cls;                  /* VOL plugin's class struct */
     herr_t ret_value = SUCCEED;         /* Return value */
 
     FUNC_ENTER_API_NOINIT
-    H5TRACE8("e", "*xiiiii*x**x", dset, plugin_id, mem_type_id, mem_space_id,
+    H5TRACE8("e", "*xiiiii*x**x", obj, plugin_id, mem_type_id, mem_space_id,
              file_space_id, plist_id, buf, req);
 
     /* Check args and get class pointer */
-    if(NULL == dset)
+    if(NULL == obj)
         HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "invalid object")
     if(NULL == (cls = (H5VL_class_t *)H5I_object_verify(plugin_id, H5I_VOL)))
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a VOL plugin ID")
 
     /* Call the corresponding internal VOL routine */
-    if(H5VL_dataset_write(dset, cls, mem_type_id, mem_space_id, file_space_id, plist_id, buf, req) < 0)
+    if(H5VL__dataset_write(obj, cls, mem_type_id, mem_space_id, file_space_id, plist_id, buf, req) < 0)
         HGOTO_ERROR(H5E_VOL, H5E_CANTINIT, FAIL, "unable to write dataset")
 
 done:
@@ -1734,6 +1938,37 @@ done:
 
 
 /*-------------------------------------------------------------------------
+ * Function:	H5VL__dataset_get
+ *
+ * Purpose:	Get specific information about the dataset through the VOL
+ *
+ * Return:      Success:    Non-negative
+ *              Failure:    Negative
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5VL__dataset_get(void *obj, const H5VL_class_t *cls, H5VL_dataset_get_t get_type, 
+    hid_t dxpl_id, void **req, va_list arguments)
+{
+    herr_t ret_value = SUCCEED;         /* Return value */
+
+    FUNC_ENTER_STATIC
+
+    /* Check if the corresponding VOL callback exists */
+    if(NULL == cls->dataset_cls.get)
+        HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL plugin has no 'dataset get' method")
+
+    /* Call the corresponding VOL callback */
+    if((cls->dataset_cls.get)(obj, get_type, dxpl_id, req, arguments) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTGET, FAIL, "dataset get failed")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5VL__dataset_get() */
+
+
+/*-------------------------------------------------------------------------
  * Function:	H5VL_dataset_get
  *
  * Purpose:	Get specific information about the dataset through the VOL
@@ -1744,30 +1979,36 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5VL_dataset_get(void *dset, const H5VL_class_t *cls, H5VL_dataset_get_t get_type, 
+H5VL_dataset_get(const H5VL_object_t *vol_obj, H5VL_dataset_get_t get_type, 
     hid_t dxpl_id, void **req, ...)
 {
     va_list arguments;                  /* Argument list passed from the API call */
     hbool_t arg_started = FALSE;        /* Whether the va_list has been started */
+    hbool_t vol_wrapper_set = FALSE;    /* Whether the VOL object wrapping context was set up */
     herr_t ret_value = SUCCEED;         /* Return value */
 
     FUNC_ENTER_NOAPI(FAIL)
 
-    /* Check if the corresponding VOL callback exists */
-    if(NULL == cls->dataset_cls.get)
-        HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL plugin has no 'dataset get' method")
+    /* Set wrapper info in API context */
+    if(H5VL_set_vol_wrapper(vol_obj->data, vol_obj->plugin) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTSET, FAIL, "can't set VOL wrapper info")
+    vol_wrapper_set = TRUE;
 
-    /* Call the corresponding VOL callback */
+    /* Call the corresponding internal VOL routine */
     va_start(arguments, req);
     arg_started = TRUE;
-    if((cls->dataset_cls.get)(dset, get_type, dxpl_id, req, arguments) < 0)
-        HGOTO_ERROR(H5E_VOL, H5E_CANTGET, FAIL, "get failed")
+    if(H5VL__dataset_get(vol_obj->data, vol_obj->plugin->cls, get_type, dxpl_id, req, arguments) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTGET, FAIL, "dataset get failed")
 
 done:
     /* End access to the va_list, if we started it */
     if(arg_started)
         va_end(arguments);
 
+    /* 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_get() */
 
@@ -1783,27 +2024,23 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5VLdataset_get(void *dset, hid_t plugin_id, H5VL_dataset_get_t get_type,
+H5VLdataset_get(void *obj, hid_t plugin_id, H5VL_dataset_get_t get_type,
     hid_t dxpl_id, void **req, va_list arguments)
 {
     H5VL_class_t *cls;                  /* VOL plugin's class struct */
     herr_t ret_value = SUCCEED;         /* Return value */
 
     FUNC_ENTER_API_NOINIT
-    H5TRACE6("e", "*xiVci**xx", dset, plugin_id, get_type, dxpl_id, req, arguments);
+    H5TRACE6("e", "*xiVci**xx", obj, plugin_id, get_type, dxpl_id, req, arguments);
 
     /* Check args and get class pointer */
-    if(NULL == dset)
+    if(NULL == obj)
         HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "invalid object")
     if(NULL == (cls = (H5VL_class_t *)H5I_object_verify(plugin_id, H5I_VOL)))
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a VOL plugin ID")
 
-    /* Check if the corresponding VOL callback exists */
-    if(NULL == cls->dataset_cls.get)
-        HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL plugin has no `dataset get' method")
-
-    /* Bypass the H5VLint layer, calling the VOL callback directly */
-    if((cls->dataset_cls.get)(dset, get_type, dxpl_id, req, arguments) < 0)
+    /* Call the corresponding internal VOL routine */
+    if(H5VL__dataset_get(obj, cls, get_type, dxpl_id, req, arguments) < 0)
         HGOTO_ERROR(H5E_VOL, H5E_CANTGET, FAIL, "Unable to execute dataset get callback")
 
 done:
@@ -1812,9 +2049,40 @@ done:
 
 
 /*-------------------------------------------------------------------------
+ * Function:	H5VL__dataset_specific
+ *
+ * Purpose:	Specific operation on datasets through the VOL
+ *
+ * Return:      Success:    Non-negative
+ *              Failure:    Negative
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5VL__dataset_specific(void *obj, const H5VL_class_t *cls, H5VL_dataset_specific_t specific_type, 
+    hid_t dxpl_id, void **req, va_list arguments)
+{
+    herr_t ret_value = SUCCEED;         /* Return value */
+
+    FUNC_ENTER_STATIC
+
+    /* Check if the corresponding VOL callback exists */
+    if(NULL == cls->dataset_cls.specific)
+        HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL plugin has no 'dataset specific' method")
+
+    /* Call the corresponding VOL callback */
+    if((cls->dataset_cls.specific)(obj, specific_type, dxpl_id, req, arguments) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTOPERATE, FAIL, "unable to execute dataset specific callback")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5VL__dataset_specific() */
+
+
+/*-------------------------------------------------------------------------
  * Function:	H5VL_dataset_specific
  *
- * Purpose:	specific operation on datasets through the VOL
+ * Purpose:	Specific operation on datasets through the VOL
  *
  * Return:      Success:    Non-negative
  *              Failure:    Negative
@@ -1822,30 +2090,36 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5VL_dataset_specific(void *obj, const H5VL_class_t *cls, H5VL_dataset_specific_t specific_type, 
+H5VL_dataset_specific(const H5VL_object_t *vol_obj, H5VL_dataset_specific_t specific_type, 
     hid_t dxpl_id, void **req, ...)
 {
     va_list arguments;                  /* Argument list passed from the API call */
     hbool_t arg_started = FALSE;        /* Whether the va_list has been started */
+    hbool_t vol_wrapper_set = FALSE;    /* Whether the VOL object wrapping context was set up */
     herr_t ret_value = SUCCEED;         /* Return value */
 
     FUNC_ENTER_NOAPI(FAIL)
 
-    /* Check if the corresponding VOL callback exists */
-    if(NULL == cls->dataset_cls.specific)
-        HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL plugin has no 'dataset specific' method")
+    /* Set wrapper info in API context */
+    if(H5VL_set_vol_wrapper(vol_obj->data, vol_obj->plugin) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTSET, FAIL, "can't set VOL wrapper info")
+    vol_wrapper_set = TRUE;
 
-    /* Call the corresponding VOL callback */
+    /* Call the corresponding internal VOL routine */
     va_start(arguments, req);
     arg_started = TRUE;
-    if((cls->dataset_cls.specific)(obj, specific_type, dxpl_id, req, arguments) < 0)
-        HGOTO_ERROR(H5E_VOL, H5E_CANTOPERATE, FAIL, "Unable to execute dataset specific callback")
+    if(H5VL__dataset_specific(vol_obj->data, vol_obj->plugin->cls, specific_type, dxpl_id, req, arguments) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTOPERATE, FAIL, "unable to execute dataset specific callback")
 
 done:
     /* End access to the va_list, if we started it */
     if(arg_started)
         va_end(arguments);
 
+    /* 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_specific() */
 
@@ -1877,13 +2151,9 @@ H5VLdataset_specific(void *obj, hid_t plugin_id, H5VL_dataset_specific_t specifi
     if(NULL == (cls = (H5VL_class_t *)H5I_object_verify(plugin_id, H5I_VOL)))
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a VOL plugin ID")
 
-    /* Check if the corresponding VOL callback exists */
-    if(NULL == cls->dataset_cls.specific)
-        HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL plugin has no `dataset specific' method")
-
-    /* Bypass the H5VLint layer, calling the VOL callback directly */
-    if((cls->dataset_cls.specific)(obj, specific_type, dxpl_id, req, arguments) < 0)
-        HGOTO_ERROR(H5E_VOL, H5E_CANTOPERATE, FAIL, "Unable to execute dataset specific callback")
+    /* Call the corresponding internal VOL routine */
+    if(H5VL__dataset_specific(obj, cls, specific_type, dxpl_id, req, arguments) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTOPERATE, FAIL, "unable to execute dataset specific callback")
 
 done:
     FUNC_LEAVE_API_NOINIT(ret_value)
@@ -1891,9 +2161,40 @@ done:
 
 
 /*-------------------------------------------------------------------------
+ * Function:	H5VL__dataset_optional
+ *
+ * Purpose:	Optional operation specific to plugins.
+ *
+ * Return:      Success:    Non-negative
+ *              Failure:    Negative
+ *
+ *-------------------------------------------------------------------------
+ */
+static herr_t
+H5VL__dataset_optional(void *obj, const H5VL_class_t *cls, hid_t dxpl_id,
+    void **req, va_list arguments)
+{
+    herr_t ret_value = SUCCEED;         /* Return value */
+
+    FUNC_ENTER_STATIC
+
+    /* Check if the corresponding VOL callback exists */
+    if(NULL == cls->dataset_cls.optional)
+        HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL plugin has no 'dataset optional' method")
+
+    /* Call the corresponding VOL callback */
+    if((cls->dataset_cls.optional)(obj, dxpl_id, req, arguments) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTOPERATE, FAIL, "unable to execute dataset optional callback")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5VL__dataset_optional() */
+
+
+/*-------------------------------------------------------------------------
  * Function:	H5VL_dataset_optional
  *
- * Purpose:	optional operation specific to plugins.
+ * Purpose:	Optional operation specific to plugins.
  *
  * Return:      Success:    Non-negative
  *              Failure:    Negative
@@ -1901,30 +2202,37 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5VL_dataset_optional(void *obj, const H5VL_class_t *cls, hid_t dxpl_id,
+H5VL_dataset_optional(const H5VL_object_t *vol_obj, hid_t dxpl_id,
     void **req, ...)
 {
     va_list arguments;                  /* Argument list passed from the API call */
     hbool_t arg_started = FALSE;        /* Whether the va_list has been started */
+    hbool_t vol_wrapper_set = FALSE;    /* Whether the VOL object wrapping context was set up */
     herr_t ret_value = SUCCEED;         /* Return value */
 
     FUNC_ENTER_NOAPI(FAIL)
 
-    /* Check if the corresponding VOL callback exists */
-    if(NULL == cls->dataset_cls.optional)
-        HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL plugin has no 'dataset optional' method")
-
     /* Call the corresponding VOL callback */
+    /* Set wrapper info in API context */
+    if(H5VL_set_vol_wrapper(vol_obj->data, vol_obj->plugin) < 1)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTSET, FAIL, "can't set VOL wrapper info")
+    vol_wrapper_set = TRUE;
+
+    /* Call the corresponding internal VOL routine */
     va_start(arguments, req);
     arg_started = TRUE;
-    if((cls->dataset_cls.optional)(obj, dxpl_id, req, arguments) < 0)
-        HGOTO_ERROR(H5E_VOL, H5E_CANTOPERATE, FAIL, "Unable to execute dataset optional callback")
+    if(H5VL__dataset_optional(vol_obj->data, vol_obj->plugin->cls, dxpl_id, req, arguments) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTOPERATE, FAIL, "unable to execute dataset optional callback")
 
 done:
     /* End access to the va_list, if we started it */
     if(arg_started)
         va_end(arguments);
 
+    /* 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_optional() */
 
@@ -1955,13 +2263,9 @@ H5VLdataset_optional(void *obj, hid_t plugin_id, hid_t dxpl_id, void **req,
     if(NULL == (cls = (H5VL_class_t *)H5I_object_verify(plugin_id, H5I_VOL)))
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a VOL plugin ID")
 
-    /* Check if the corresponding VOL callback exists */
-    if(NULL == cls->dataset_cls.optional)
-        HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL plugin has no `dataset optional' method")
-
-    /* Bypass the H5VLint layer, calling the VOL callback directly */
-    if((cls->dataset_cls.optional)(obj, dxpl_id, req, arguments) < 0)
-        HGOTO_ERROR(H5E_VOL, H5E_CANTOPERATE, FAIL, "Unable to execute dataset optional callback")
+    /* Call the corresponding internal VOL routine */
+    if(H5VL__dataset_optional(obj, cls, dxpl_id, req, arguments) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTOPERATE, FAIL, "unable to execute dataset optional callback")
 
 done:
     FUNC_LEAVE_API_NOINIT(ret_value)
@@ -1969,7 +2273,7 @@ done:
 
 
 /*-------------------------------------------------------------------------
- * Function:    H5VL_dataset_close
+ * Function:    H5VL__dataset_close
  *
  * Purpose:     Closes a dataset through the VOL
  *
@@ -1978,26 +2282,68 @@ done:
  *
  *-------------------------------------------------------------------------
  */
-herr_t
-H5VL_dataset_close(void *dset, const H5VL_class_t *cls, hid_t dxpl_id, void **req)
+static herr_t
+H5VL__dataset_close(void *obj, const H5VL_class_t *cls, hid_t dxpl_id, void **req)
 {
     herr_t ret_value = SUCCEED;         /* Return value */
 
-    FUNC_ENTER_NOAPI(FAIL)
+    FUNC_ENTER_STATIC
 
     /* Sanity check */
-    HDassert(dset);
+    HDassert(obj);
     HDassert(cls);
 
     /* Check if the corresponding VOL callback exists */
     if(NULL == cls->dataset_cls.close)
-        HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL plugin has no 'dset close' method")
+        HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL plugin has no 'dataset close' method")
 
     /* Call the corresponding VOL callback */
-    if((cls->dataset_cls.close)(dset, dxpl_id, req) < 0)
-        HGOTO_ERROR(H5E_VOL, H5E_CANTCLOSEOBJ, FAIL, "close failed")
+    if((cls->dataset_cls.close)(obj, dxpl_id, req) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTCLOSEOBJ, FAIL, "dataset close failed")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5VL__dataset_close() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5VL_dataset_close
+ *
+ * Purpose:     Closes a dataset through the VOL
+ *
+ * Return:      Success:    Non-negative
+ *              Failure:    Negative
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5VL_dataset_close(const H5VL_object_t *vol_obj, hid_t dxpl_id, void **req)
+{
+    hbool_t vol_wrapper_set = FALSE;    /* Whether the VOL object wrapping context was set up */
+    herr_t ret_value = SUCCEED;         /* Return value */
+
+    FUNC_ENTER_NOAPI(FAIL)
+
+    /* Sanity check */
+    HDassert(vol_obj);
+    HDassert(vol_obj->data);
+    HDassert(vol_obj->plugin);
+    HDassert(vol_obj->plugin->cls);
+
+    /* Set wrapper info in API context */
+    if(H5VL_set_vol_wrapper(vol_obj->data, vol_obj->plugin) < 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_close(vol_obj->data, vol_obj->plugin->cls, dxpl_id, req) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTCLOSEOBJ, FAIL, "dataset close 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_close() */
 
@@ -2013,22 +2359,22 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5VLdataset_close(void *dset, hid_t plugin_id, hid_t dxpl_id, void **req)
+H5VLdataset_close(void *obj, hid_t plugin_id, hid_t dxpl_id, void **req)
 {
     H5VL_class_t *cls;                  /* VOL plugin's class struct */
     herr_t ret_value = SUCCEED;         /* Return value */
 
     FUNC_ENTER_API_NOINIT
-    H5TRACE4("e", "*xii**x", dset, plugin_id, dxpl_id, req);
+    H5TRACE4("e", "*xii**x", obj, plugin_id, dxpl_id, req);
 
     /* Check args and get class pointer */
-    if(NULL == dset)
+    if(NULL == obj)
         HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "invalid object")
     if(NULL == (cls = (H5VL_class_t *)H5I_object_verify(plugin_id, H5I_VOL)))
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a VOL plugin ID")
 
     /* Call the corresponding internal VOL routine */
-    if(H5VL_dataset_close(dset, cls, dxpl_id, req) < 0)
+    if(H5VL__dataset_close(obj, cls, dxpl_id, req) < 0)
         HGOTO_ERROR(H5E_VOL, H5E_CANTCLOSEOBJ, FAIL, "unable to close dataset")
 
 done:
diff --git a/src/H5VLprivate.h b/src/H5VLprivate.h
index b2ca1ba..51d99b4 100644
--- a/src/H5VLprivate.h
+++ b/src/H5VLprivate.h
@@ -107,20 +107,20 @@ H5_DLL void *H5VL_attr_create(const H5VL_object_t *vol_obj, H5VL_loc_params_t lo
 H5_DLL void *H5VL_attr_open(const H5VL_object_t *vol_obj, H5VL_loc_params_t loc_params, const char *name, hid_t aapl_id, hid_t dxpl_id, void **req);
 H5_DLL herr_t H5VL_attr_read(const H5VL_object_t *vol_obj, hid_t dtype_id, void *buf, hid_t dxpl_id, void **req);
 H5_DLL herr_t H5VL_attr_write(const H5VL_object_t *vol_obj, hid_t dtype_id, const void *buf, hid_t dxpl_id, void **req);
-H5_DLL herr_t H5VL_attr_get(void *obj, const H5VL_class_t *cls, H5VL_attr_get_t get_type, hid_t dxpl_id, void **req, ...);
+H5_DLL herr_t H5VL_attr_get(const H5VL_object_t *vol_obj, H5VL_attr_get_t get_type, hid_t dxpl_id, void **req, ...);
 H5_DLL herr_t H5VL_attr_specific(const H5VL_object_t *vol_obj, H5VL_loc_params_t loc_params, H5VL_attr_specific_t specific_type, hid_t dxpl_id, void **req, ...);
 H5_DLL herr_t H5VL_attr_optional(const H5VL_object_t *vol_obj, hid_t dxpl_id, void **req, ...);
 H5_DLL herr_t H5VL_attr_close(const H5VL_object_t *vol_obj, hid_t dxpl_id, void **req);
 
 /* Dataset functions */
-H5_DLL void *H5VL_dataset_create(void *obj, H5VL_loc_params_t loc_params, const H5VL_class_t *cls, const char *name, hid_t dcpl_id, hid_t dapl_id, hid_t dxpl_id, void **req);
-H5_DLL void *H5VL_dataset_open(void *obj, H5VL_loc_params_t loc_params, const H5VL_class_t *cls, const char *name, hid_t dapl_id, hid_t dxpl_id, void **req);
-H5_DLL 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 plist_id, void *buf, void **req);
-H5_DLL herr_t H5VL_dataset_write(void *dset, const H5VL_class_t *cls, hid_t mem_type_id, hid_t mem_space_id, hid_t file_space_id, hid_t plist_id, const void *buf, void **req);
-H5_DLL herr_t H5VL_dataset_get(void *dset, const H5VL_class_t *cls, H5VL_dataset_get_t get_type, hid_t dxpl_id, void **req, ...);
-H5_DLL herr_t H5VL_dataset_specific(void *obj, const H5VL_class_t *cls, H5VL_dataset_specific_t specific_type, hid_t dxpl_id, void **req, ...);
-H5_DLL herr_t H5VL_dataset_optional(void *obj, const H5VL_class_t *cls, hid_t dxpl_id, void **req, ...);
-H5_DLL herr_t H5VL_dataset_close(void *dset, const H5VL_class_t *cls, hid_t dxpl_id, void **req);
+H5_DLL void *H5VL_dataset_create(const H5VL_object_t *vol_obj, H5VL_loc_params_t loc_params, const char *name, hid_t dcpl_id, hid_t dapl_id, hid_t dxpl_id, void **req);
+H5_DLL void * H5VL_dataset_open(const H5VL_object_t *vol_obj, H5VL_loc_params_t loc_params, const char *name, hid_t dapl_id, hid_t dxpl_id, void **req);
+H5_DLL 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 plist_id, void *buf, void **req);
+H5_DLL 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 plist_id, const void *buf, void **req);
+H5_DLL herr_t H5VL_dataset_get(const H5VL_object_t *vol_obj, H5VL_dataset_get_t get_type, hid_t dxpl_id, void **req, ...);
+H5_DLL herr_t H5VL_dataset_specific(const H5VL_object_t *cls, H5VL_dataset_specific_t specific_type, hid_t dxpl_id, void **req, ...);
+H5_DLL herr_t H5VL_dataset_optional(const H5VL_object_t *vol_obj, hid_t dxpl_id, void **req, ...);
+H5_DLL herr_t H5VL_dataset_close(const H5VL_object_t *vol_obj, hid_t dxpl_id, void **req);
 
 /* File functions */
 H5_DLL void *H5VL_file_create(const H5VL_class_t *cls, const char *name, unsigned flags, hid_t fcpl_id, hid_t fapl_id, hid_t dxpl_id, void **req);