Convert attribute VOL callbacks to a standard form that sets up the wrapper

object info in a single place.

5 files changed, 373 insertions, 152 deletions

diff --git a/src/H5A.c b/src/H5A.c
index 7a6bd4c..711897c 100644
--- a/src/H5A.c
+++ b/src/H5A.c
@@ -296,8 +296,7 @@ H5Acreate2(hid_t loc_id, const char *attr_name, hid_t type_id, hid_t space_id,
     loc_params.obj_type = H5I_get_type(loc_id);
 
     /* Create the attribute */
-    if(NULL == (attr = H5VL_attr_create(vol_obj->data, loc_params, vol_obj->plugin->cls, attr_name, 
-                                        acpl_id, aapl_id, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
+    if(NULL == (attr = H5VL_attr_create(vol_obj, loc_params, attr_name, acpl_id, aapl_id, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
         HGOTO_ERROR(H5E_ATTR, H5E_CANTINIT, H5I_INVALID_HID, "unable to create attribute")
 
     /* Register the new attribute and get an ID for it */
@@ -307,7 +306,7 @@ H5Acreate2(hid_t loc_id, const char *attr_name, hid_t type_id, hid_t space_id,
 done:
     /* Cleanup on failure */
     if(H5I_INVALID_HID == ret_value)
-        if(attr && H5VL_attr_close(attr, vol_obj->plugin->cls, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
+        if(attr && H5VL_attr_close(vol_obj, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
             HDONE_ERROR(H5E_ATTR, H5E_CLOSEERROR, H5I_INVALID_HID, "can't close attribute")
 
     FUNC_LEAVE_API(ret_value)
@@ -402,8 +401,7 @@ H5Acreate_by_name(hid_t loc_id, const char *obj_name, const char *attr_name,
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, H5I_INVALID_HID, "invalid location identifier")
 
     /* Create the attribute */
-    if(NULL == (attr = H5VL_attr_create(vol_obj->data, loc_params, vol_obj->plugin->cls, attr_name, 
-                                        acpl_id, aapl_id, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
+    if(NULL == (attr = H5VL_attr_create(vol_obj, loc_params, attr_name, acpl_id, aapl_id, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
         HGOTO_ERROR(H5E_ATTR, H5E_CANTINIT, H5I_INVALID_HID, "unable to create attribute")
 
     /* Register the new attribute and get an ID for it */
@@ -413,7 +411,7 @@ H5Acreate_by_name(hid_t loc_id, const char *obj_name, const char *attr_name,
 done:
     /* Cleanup on failure */
     if(H5I_INVALID_HID == ret_value)
-        if(attr && H5VL_attr_close (attr, vol_obj->plugin->cls, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
+        if(attr && H5VL_attr_close(vol_obj, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
             HDONE_ERROR(H5E_ATTR, H5E_CLOSEERROR, H5I_INVALID_HID, "can't close attribute")
 
     FUNC_LEAVE_API(ret_value)
@@ -471,8 +469,7 @@ H5Aopen(hid_t loc_id, const char *attr_name, hid_t aapl_id)
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, H5I_INVALID_HID, "invalid location identifier")
 
     /* Open the attribute */
-    if(NULL == (attr = H5VL_attr_open(vol_obj->data, loc_params, vol_obj->plugin->cls, 
-                                      attr_name, aapl_id, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
+    if(NULL == (attr = H5VL_attr_open(vol_obj, loc_params, attr_name, aapl_id, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
         HGOTO_ERROR(H5E_ATTR, H5E_CANTOPENOBJ, H5I_INVALID_HID, "unable to open attribute: '%s'", attr_name)
 
     /* Register the attribute and get an ID for it */
@@ -482,7 +479,7 @@ H5Aopen(hid_t loc_id, const char *attr_name, hid_t aapl_id)
 done:
     /* Cleanup on failure */
     if(H5I_INVALID_HID == ret_value)
-        if(attr && H5VL_attr_close(attr, vol_obj->plugin->cls, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
+        if(attr && H5VL_attr_close(vol_obj, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
             HDONE_ERROR(H5E_ATTR, H5E_CLOSEERROR, H5I_INVALID_HID, "can't close attribute")
 
     FUNC_LEAVE_API(ret_value)
@@ -554,8 +551,7 @@ H5Aopen_by_name(hid_t loc_id, const char *obj_name, const char *attr_name,
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, H5I_INVALID_HID, "invalid location identifier")
 
     /* Open the attribute */
-    if(NULL == (attr = H5VL_attr_open(vol_obj->data, loc_params, vol_obj->plugin->cls, 
-                                      attr_name, aapl_id, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
+    if(NULL == (attr = H5VL_attr_open(vol_obj, loc_params, attr_name, aapl_id, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
         HGOTO_ERROR(H5E_ATTR, H5E_CANTOPENOBJ, H5I_INVALID_HID, "can't open attribute")
 
     /* Register the attribute and get an ID for it */
@@ -565,7 +561,7 @@ H5Aopen_by_name(hid_t loc_id, const char *obj_name, const char *attr_name,
 done:
     /* Cleanup on failure */
     if(H5I_INVALID_HID == ret_value)
-        if(attr && H5VL_attr_close (attr, vol_obj->plugin->cls, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
+        if(attr && H5VL_attr_close(vol_obj, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
             HDONE_ERROR(H5E_ATTR, H5E_CLOSEERROR, H5I_INVALID_HID, "can't close attribute")
 
     FUNC_LEAVE_API(ret_value)
@@ -646,8 +642,7 @@ H5Aopen_by_idx(hid_t loc_id, const char *obj_name, H5_index_t idx_type,
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, H5I_INVALID_HID, "invalid location identifier")
 
     /* Open the attribute */
-    if(NULL == (attr = H5VL_attr_open(vol_obj->data, loc_params, vol_obj->plugin->cls, 
-                                      NULL, aapl_id, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
+    if(NULL == (attr = H5VL_attr_open(vol_obj, loc_params, NULL, aapl_id, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
         HGOTO_ERROR(H5E_ATTR, H5E_CANTOPENOBJ, H5I_INVALID_HID, "unable to open attribute")
 
     /* Register the attribute and get an ID for it */
@@ -657,7 +652,7 @@ H5Aopen_by_idx(hid_t loc_id, const char *obj_name, H5_index_t idx_type,
 done:
     /* Cleanup on failure */
     if(H5I_INVALID_HID == ret_value)
-        if(attr && H5VL_attr_close(attr, vol_obj->plugin->cls, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
+        if(attr && H5VL_attr_close(vol_obj, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
             HDONE_ERROR(H5E_ATTR, H5E_CLOSEERROR, H5I_INVALID_HID, "can't close attribute")
 
     FUNC_LEAVE_API(ret_value)
@@ -702,8 +697,7 @@ H5Awrite(hid_t attr_id, hid_t dtype_id, const void *buf)
         HGOTO_ERROR(H5E_ATTR, H5E_CANTSET, FAIL, "can't set collective metadata read")
 
     /* Write the attribute data */
-    if((ret_value = H5VL_attr_write(vol_obj->data, vol_obj->plugin->cls, 
-                                    dtype_id, buf, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)) < 0)
+    if((ret_value = H5VL_attr_write(vol_obj, dtype_id, buf, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)) < 0)
         HGOTO_ERROR(H5E_ATTR, H5E_WRITEERROR, FAIL, "unable to write attribute")
 
 done:
@@ -745,8 +739,7 @@ H5Aread(hid_t attr_id, hid_t dtype_id, void *buf)
         HGOTO_ERROR(H5E_ARGS, H5E_BADVALUE, FAIL, "buf parameter can't be NULL")
 
     /* Read the attribute data */
-    if((ret_value = H5VL_attr_read(vol_obj->data, vol_obj->plugin->cls, 
-                                   dtype_id, buf, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)) < 0)
+    if((ret_value = H5VL_attr_read(vol_obj, dtype_id, buf, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)) < 0)
         HGOTO_ERROR(H5E_ATTR, H5E_READERROR, FAIL, "unable to read attribute")
 
 done:
@@ -1247,10 +1240,9 @@ H5Arename(hid_t loc_id, const char *old_name, const char *new_name)
             HGOTO_ERROR(H5E_ATTR, H5E_CANTSET, FAIL, "can't set collective metadata read")
 
         /* Rename the attribute */
-        if((ret_value = H5VL_attr_specific(vol_obj->data, loc_params, vol_obj->plugin->cls, H5VL_ATTR_RENAME,
-                                           H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, old_name, new_name)) < 0)
+        if(H5VL_attr_specific(vol_obj, loc_params, H5VL_ATTR_RENAME, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, old_name, new_name) < 0)
             HGOTO_ERROR(H5E_ATTR, H5E_CANTRENAME, FAIL, "can't rename attribute")
-    }
+    } /* end if */
 
 done:
     FUNC_LEAVE_API(ret_value)
@@ -1308,10 +1300,9 @@ H5Arename_by_name(hid_t loc_id, const char *obj_name, const char *old_attr_name,
             HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "invalid location identifier")
 
         /* Rename the attribute */
-        if((ret_value = H5VL_attr_specific(vol_obj->data, loc_params, vol_obj->plugin->cls, H5VL_ATTR_RENAME,
-                                           H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, old_attr_name, new_attr_name)) < 0)
+        if(H5VL_attr_specific(vol_obj, loc_params, H5VL_ATTR_RENAME, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, old_attr_name, new_attr_name) < 0)
             HGOTO_ERROR(H5E_ATTR, H5E_CANTRENAME, FAIL, "can't rename attribute")
-    }
+    } /* end if */
 
 done:
     FUNC_LEAVE_API(ret_value)
@@ -1365,7 +1356,6 @@ H5Aiterate2(hid_t loc_id, H5_index_t idx_type, H5_iter_order_t order,
 {
     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 */
     herr_t	ret_value;      /* Return value */
 
     FUNC_ENTER_API(FAIL)
@@ -1386,20 +1376,11 @@ H5Aiterate2(hid_t loc_id, H5_index_t idx_type, H5_iter_order_t order,
     if(NULL == (vol_obj = H5VL_vol_object(loc_id)))
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "invalid location 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;
-
     /* Iterate over attributes */
-    if((ret_value = H5VL_attr_specific(vol_obj->data, loc_params, vol_obj->plugin->cls, H5VL_ATTR_ITER, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, idx_type, order, idx, op, op_data)) < 0)
+    if((ret_value = H5VL_attr_specific(vol_obj, loc_params, H5VL_ATTR_ITER, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, idx_type, order, idx, op, op_data)) < 0)
         HERROR(H5E_ATTR, H5E_BADITER, "error iterating over attributes");
 
 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)
 } /* H5Aiterate2() */
 
@@ -1454,7 +1435,6 @@ H5Aiterate_by_name(hid_t loc_id, const char *obj_name, H5_index_t idx_type,
 {
     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 */
     herr_t   ret_value = SUCCEED;      /* Return value */
 
     FUNC_ENTER_API(FAIL)
@@ -1484,20 +1464,11 @@ H5Aiterate_by_name(hid_t loc_id, const char *obj_name, H5_index_t idx_type,
     if(NULL == (vol_obj = H5VL_vol_object(loc_id)))
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "invalid location 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;
-
     /* Iterate over attributes */
-    if((ret_value = H5VL_attr_specific(vol_obj->data, loc_params, vol_obj->plugin->cls, H5VL_ATTR_ITER, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, idx_type, order, idx, op, op_data)) < 0)
+    if((ret_value = H5VL_attr_specific(vol_obj, loc_params, H5VL_ATTR_ITER, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, idx_type, order, idx, op, op_data)) < 0)
         HERROR(H5E_ATTR, H5E_BADITER, "attribute iteration failed");
 
 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)
 } /* H5Aiterate_by_name() */
 
@@ -1547,8 +1518,7 @@ H5Adelete(hid_t loc_id, const char *name)
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "invalid object identifier")
 
     /* Delete the attribute */
-    if((ret_value = H5VL_attr_specific(vol_obj->data, loc_params, vol_obj->plugin->cls, H5VL_ATTR_DELETE,
-                                       H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, name)) < 0)
+    if(H5VL_attr_specific(vol_obj, loc_params, H5VL_ATTR_DELETE, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, name) < 0)
         HGOTO_ERROR(H5E_ATTR, H5E_CANTDELETE, FAIL, "unable to delete attribute")
 
 done:
@@ -1606,8 +1576,7 @@ H5Adelete_by_name(hid_t loc_id, const char *obj_name, const char *attr_name,
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "invalid object identifier")
 
     /* Delete the attribute */
-    if((ret_value = H5VL_attr_specific(vol_obj->data, loc_params, vol_obj->plugin->cls, H5VL_ATTR_DELETE,
-                                       H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, attr_name)) < 0)
+    if(H5VL_attr_specific(vol_obj, loc_params, H5VL_ATTR_DELETE, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, attr_name) < 0)
         HGOTO_ERROR(H5E_ATTR, H5E_CANTDELETE, FAIL, "unable to delete attribute")
 
 done:
@@ -1677,8 +1646,7 @@ H5Adelete_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")
 
     /* Delete the attribute through the VOL */
-    if((ret_value = H5VL_attr_specific(vol_obj->data, loc_params, vol_obj->plugin->cls, H5VL_ATTR_DELETE,
-                                       H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, NULL)) < 0)
+    if(H5VL_attr_specific(vol_obj, loc_params, H5VL_ATTR_DELETE, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, NULL) < 0)
         HGOTO_ERROR(H5E_ATTR, H5E_CANTDELETE, FAIL, "unable to delete attribute")
 
 done:
@@ -1756,8 +1724,7 @@ H5Aexists(hid_t obj_id, const char *attr_name)
     loc_params.obj_type = H5I_get_type(obj_id);
 
     /* Check if the attribute exists */
-    if(H5VL_attr_specific(vol_obj->data, loc_params, vol_obj->plugin->cls, H5VL_ATTR_EXISTS,
-                          H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, attr_name, &ret_value) < 0)
+    if(H5VL_attr_specific(vol_obj, loc_params, H5VL_ATTR_EXISTS, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, attr_name, &ret_value) < 0)
         HGOTO_ERROR(H5E_ATTR, H5E_CANTGET, FAIL, "unable to determine if attribute exists")
 
 done:
@@ -1811,8 +1778,7 @@ H5Aexists_by_name(hid_t loc_id, const char *obj_name, const char *attr_name,
     loc_params.obj_type = H5I_get_type(loc_id);
 
     /* Check existence of attribute */
-    if(H5VL_attr_specific(vol_obj->data, loc_params, vol_obj->plugin->cls, H5VL_ATTR_EXISTS,
-                          H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, attr_name, &ret_value) < 0)
+    if(H5VL_attr_specific(vol_obj, loc_params, H5VL_ATTR_EXISTS, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL, attr_name, &ret_value) < 0)
         HGOTO_ERROR(H5E_ATTR, H5E_CANTGET, FAIL, "unable to determine if attribute exists")
 
 done:
diff --git a/src/H5Adeprec.c b/src/H5Adeprec.c
index b7e9ec4..894bbc1 100644
--- a/src/H5Adeprec.c
+++ b/src/H5Adeprec.c
@@ -156,8 +156,7 @@ H5Acreate1(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 attribute */
-    if(NULL == (attr = H5VL_attr_create(vol_obj->data, loc_params, vol_obj->plugin->cls, name, 
-                                        acpl_id, H5P_DEFAULT, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
+    if(NULL == (attr = H5VL_attr_create(vol_obj, loc_params, name, acpl_id, H5P_DEFAULT, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
         HGOTO_ERROR(H5E_ATTR, H5E_CANTINIT, H5I_INVALID_HID, "unable to create attribute")
 
     /* Register the new attribute and get an ID for it */
@@ -167,7 +166,7 @@ H5Acreate1(hid_t loc_id, const char *name, hid_t type_id, hid_t space_id,
 done:
     /* Clean up on failure */
     if(H5I_INVALID_HID == ret_value)
-        if(attr && H5VL_attr_close(attr, vol_obj->plugin->cls, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
+        if(attr && H5VL_attr_close(vol_obj, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
             HDONE_ERROR(H5E_ATTR, H5E_CLOSEERROR, H5I_INVALID_HID, "can't close attribute")
 
     FUNC_LEAVE_API(ret_value)
@@ -218,22 +217,21 @@ H5Aopen_name(hid_t loc_id, const char *name)
     loc_params.obj_type     = H5I_get_type(loc_id);
 
     /* Get the location object */
-    if (NULL == (vol_obj = H5VL_vol_object(loc_id)))
+    if(NULL == (vol_obj = H5VL_vol_object(loc_id)))
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, H5I_INVALID_HID, "invalid location identifier")
 
     /* Open the attribute */
-    if (NULL == (attr = H5VL_attr_open(vol_obj->data, loc_params, vol_obj->plugin->cls, 
-                                      name, H5P_DEFAULT, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
+    if(NULL == (attr = H5VL_attr_open(vol_obj, loc_params, name, H5P_DEFAULT, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
         HGOTO_ERROR(H5E_ATTR, H5E_CANTOPENOBJ, H5I_INVALID_HID, "unable to open attribute")
 
     /* Register the attribute and get an ID for it */
-    if ((ret_value = H5VL_register(H5I_ATTR, attr, vol_obj->plugin, TRUE)) < 0)
+    if((ret_value = H5VL_register(H5I_ATTR, attr, vol_obj->plugin, TRUE)) < 0)
         HGOTO_ERROR(H5E_ATTR, H5E_CANTREGISTER, H5I_INVALID_HID, "unable to atomize attribute handle")
 
 done:
     /* Clean up on failure */
     if(H5I_INVALID_HID == ret_value)
-        if(attr && H5VL_attr_close(attr, vol_obj->plugin->cls, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
+        if(attr && H5VL_attr_close(vol_obj, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
             HDONE_ERROR(H5E_ATTR, H5E_CLOSEERROR, H5I_INVALID_HID, "can't close attribute")
 
     FUNC_LEAVE_API(ret_value)
@@ -291,8 +289,7 @@ H5Aopen_idx(hid_t loc_id, unsigned idx)
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, H5I_INVALID_HID, "invalid location identifier")
 
     /* Open the attribute */
-    if(NULL == (attr = H5VL_attr_open(vol_obj->data, loc_params, vol_obj->plugin->cls, 
-                                      NULL, H5P_DEFAULT, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
+    if(NULL == (attr = H5VL_attr_open(vol_obj, loc_params, NULL, H5P_DEFAULT, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)))
         HGOTO_ERROR(H5E_ATTR, H5E_CANTOPENOBJ, H5I_INVALID_HID, "unable to open attribute")
 
     /* Register the attribute and get an ID for it */
@@ -302,7 +299,7 @@ H5Aopen_idx(hid_t loc_id, unsigned idx)
 done:
     /* Clean up on failure */
     if(H5I_INVALID_HID == ret_value)
-        if(attr && H5VL_attr_close(attr, vol_obj->plugin->cls, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
+        if(attr && H5VL_attr_close(vol_obj, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL) < 0)
             HDONE_ERROR(H5E_ATTR, H5E_CLOSEERROR, H5I_INVALID_HID, "can't close attribute")
 
     FUNC_LEAVE_API(ret_value)
diff --git a/src/H5Aint.c b/src/H5Aint.c
index 44b11a4..97da9a4 100644
--- a/src/H5Aint.c
+++ b/src/H5Aint.c
@@ -1163,7 +1163,7 @@ H5A__close_cb(H5VL_object_t *attr_vol_obj)
     HDassert(attr_vol_obj);
 
     /* Close the attribute */
-    if((ret_value = H5VL_attr_close(attr_vol_obj->data, attr_vol_obj->plugin->cls, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)) < 0)
+    if((ret_value = H5VL_attr_close(attr_vol_obj, H5P_DATASET_XFER_DEFAULT, H5_REQUEST_NULL)) < 0)
         HGOTO_ERROR(H5E_ATTR, H5E_CLOSEERROR, FAIL, "problem closing attribute")
 
     /* Free the VOL object */
diff --git a/src/H5VLcallback.c b/src/H5VLcallback.c
index 7771b07..9610f6a 100644
--- a/src/H5VLcallback.c
+++ b/src/H5VLcallback.c
@@ -56,6 +56,23 @@
 /********************/
 /* Local Prototypes */
 /********************/
+static void *H5VL__attr_create(void *obj, H5VL_loc_params_t loc_params,
+    const H5VL_class_t *cls, const char *name, hid_t acpl_id, hid_t aapl_id,
+    hid_t dxpl_id, void **req);
+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,
+    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,
+    const void *buf, hid_t dxpl_id, void **req);
+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);
+static herr_t H5VL__attr_optional(void *obj, const H5VL_class_t *cls, hid_t dxpl_id,
+    void **req, va_list arguments);
+static herr_t H5VL__attr_close(void *obj, const H5VL_class_t *cls, hid_t dxpl_id,
+    void **req);
 
 
 /*********************/
@@ -642,7 +659,7 @@ done:
 
 
 /*-------------------------------------------------------------------------
- * Function:    H5VL_attr_create
+ * Function:    H5VL__attr_create
  *
  * Purpose:     Creates an attribute through the VOL
  *
@@ -651,23 +668,60 @@ done:
  *
  *-------------------------------------------------------------------------
  */
-void *
-H5VL_attr_create(void *obj, H5VL_loc_params_t loc_params, const H5VL_class_t *cls, const char *name, 
-                 hid_t acpl_id, hid_t aapl_id, hid_t dxpl_id, void **req)
+static void *
+H5VL__attr_create(void *obj, H5VL_loc_params_t loc_params, const H5VL_class_t *cls,
+    const char *name, hid_t acpl_id, hid_t aapl_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 create callback exists */
+    /* Check if the corresponding VOL callback exists */
     if(NULL == cls->attr_cls.create)
         HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, NULL, "VOL plugin has no 'attr create' method")
 
-    /* Call the corresponding VOL create callback */
+    /* Call the corresponding VOL callback */
     if(NULL == (ret_value = (cls->attr_cls.create)(obj, loc_params, name, acpl_id, aapl_id, dxpl_id, req)))
-        HGOTO_ERROR(H5E_VOL, H5E_CANTCREATE, NULL, "create failed")
+        HGOTO_ERROR(H5E_VOL, H5E_CANTCREATE, NULL, "attribute create failed")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5VL_attr_create() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5VL_attr_create
+ *
+ * Purpose:     Creates an attribute through the VOL
+ *
+ * Return:      Success: Pointer to the new attribute 
+ *              Failure: NULL
+ *
+ *-------------------------------------------------------------------------
+ */
+void *
+H5VL_attr_create(const H5VL_object_t *vol_obj, H5VL_loc_params_t loc_params, 
+    const char *name, hid_t acpl_id, hid_t aapl_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__attr_create(vol_obj->data, loc_params, vol_obj->plugin->cls, name, acpl_id, aapl_id, dxpl_id, req)))
+        HGOTO_ERROR(H5E_VOL, H5E_CANTCREATE, NULL, "attribute 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_attr_create() */
 
@@ -683,8 +737,8 @@ done:
  *-------------------------------------------------------------------------
  */
 void *
-H5VLattr_create(void *obj, H5VL_loc_params_t loc_params, hid_t plugin_id, const char *name,
-                hid_t acpl_id, hid_t aapl_id, hid_t dxpl_id, void **req)
+H5VLattr_create(void *obj, H5VL_loc_params_t loc_params, hid_t plugin_id,
+    const char *name, hid_t acpl_id, hid_t aapl_id, hid_t dxpl_id, void **req)
 {
     H5VL_class_t *cls;          /* VOL plugin's class struct */
     void *ret_value = NULL;     /* Return value */
@@ -700,7 +754,7 @@ H5VLattr_create(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_attr_create(obj, loc_params, cls, name, acpl_id, aapl_id, dxpl_id, req)))
+    if(NULL == (ret_value = H5VL__attr_create(obj, loc_params, cls, name, acpl_id, aapl_id, dxpl_id, req)))
         HGOTO_ERROR(H5E_VOL, H5E_CANTCREATE, NULL, "unable to create attribute")
 
 done:
@@ -709,7 +763,7 @@ done:
 
 
 /*-------------------------------------------------------------------------
- * Function:	H5VL_attr_open
+ * Function:	H5VL__attr_open
  *
  * Purpose:	Opens an attribute through the VOL
  *
@@ -718,23 +772,60 @@ done:
  *
  *-------------------------------------------------------------------------
  */
-void *
-H5VL_attr_open(void *obj, H5VL_loc_params_t loc_params, const H5VL_class_t *cls, const char *name, 
+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)
 {
     void *ret_value = NULL;     /* Return value */
 
-    FUNC_ENTER_NOAPI(NULL)
+    FUNC_ENTER_STATIC
 
     /* Check if the corresponding VOL callback exists */
     if(NULL == cls->attr_cls.open)
         HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, NULL, "VOL plugin has no 'attr open' method")
 
     /* Call the corresponding VOL open callback */
-    if(NULL == (ret_value = (cls->attr_cls.open) (obj, loc_params, name, aapl_id, dxpl_id, req)))
+    if(NULL == (ret_value = (cls->attr_cls.open)(obj, loc_params, name, aapl_id, dxpl_id, req)))
+        HGOTO_ERROR(H5E_VOL, H5E_CANTOPENOBJ, NULL, "attribute open failed")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5VL__attr_open() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5VL_attr_open
+ *
+ * Purpose:	Opens an attribute through the VOL
+ *
+ * Return:      Success: Pointer to the attribute
+ *		Failure: NULL
+ *
+ *-------------------------------------------------------------------------
+ */
+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)
+{
+    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, FAIL, "can't set VOL wrapper info")
+    vol_wrapper_set = TRUE;
+
+    /* Call the corresponding internal VOL routine */
+    if(NULL == (ret_value = H5VL__attr_open(vol_obj->data, loc_params, vol_obj->plugin->cls, name, aapl_id, dxpl_id, req)))
         HGOTO_ERROR(H5E_VOL, H5E_CANTOPENOBJ, NULL, "attribute 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, FAIL, "can't reset VOL wrapper info")
+
     FUNC_LEAVE_NOAPI(ret_value)
 } /* end H5VL_attr_open() */
 
@@ -750,8 +841,8 @@ done:
  *-------------------------------------------------------------------------
  */
 void *
-H5VLattr_open(void *obj, H5VL_loc_params_t loc_params, hid_t plugin_id, const char *name,
-              hid_t aapl_id, hid_t dxpl_id, void **req)
+H5VLattr_open(void *obj, H5VL_loc_params_t loc_params, hid_t plugin_id,
+    const char *name, hid_t aapl_id, hid_t dxpl_id, void **req)
 {
     H5VL_class_t *cls;          /* VOL plugin's class struct */
     void *ret_value = NULL;     /* Return value */
@@ -767,7 +858,7 @@ H5VLattr_open(void *obj, H5VL_loc_params_t loc_params, hid_t plugin_id, const ch
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, NULL, "not a VOL plugin ID")
 
     /* Call the corresponding internal VOL routine */
-    if(NULL == (ret_value = H5VL_attr_open(obj, loc_params, cls, name, aapl_id, dxpl_id, req)))
+    if(NULL == (ret_value = H5VL__attr_open(obj, loc_params, cls, name, aapl_id, dxpl_id, req)))
         HGOTO_ERROR(H5E_VOL, H5E_CANTOPENOBJ, NULL, "unable to open attribute")
 
 done:
@@ -776,7 +867,7 @@ done:
 
 
 /*-------------------------------------------------------------------------
- * Function:	H5VL_attr_read
+ * Function:	H5VL__attr_read
  *
  * Purpose:	Reads data from attr through the VOL
  *
@@ -785,22 +876,60 @@ done:
  *
  *-------------------------------------------------------------------------
  */
-herr_t H5VL_attr_read(void *attr, const H5VL_class_t *cls, hid_t mem_type_id, void *buf, 
+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)
 {
     herr_t ret_value = SUCCEED;         /* Return value */
 
-    FUNC_ENTER_NOAPI(FAIL)
+    FUNC_ENTER_STATIC
 
     /* Check if the corresponding VOL callback exists */
     if(NULL == cls->attr_cls.read)
         HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL plugin has no 'attr read' method")
 
     /* Call the corresponding VOL callback */
-    if((cls->attr_cls.read)(attr, mem_type_id, buf, dxpl_id, req) < 0)
+    if((cls->attr_cls.read)(obj, mem_type_id, buf, dxpl_id, req) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_READERROR, FAIL, "attribute read failed")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5VL__attr_read() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5VL_attr_read
+ *
+ * Purpose:	Reads data from attr through the VOL
+ *
+ * Return:      Success:    Non-negative
+ *              Failure:    Negative
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5VL_attr_read(const H5VL_object_t *vol_obj, hid_t mem_type_id, void *buf, 
+    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)
+
+    /* 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__attr_read(vol_obj->data, vol_obj->plugin->cls, mem_type_id, buf, dxpl_id, req) < 0)
         HGOTO_ERROR(H5E_VOL, H5E_READERROR, FAIL, "attribute 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_attr_read() */
 
@@ -816,7 +945,7 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5VLattr_read(void *attr, hid_t plugin_id, hid_t mem_type_id, void *buf, hid_t dxpl_id, void **req)
+H5VLattr_read(void *obj, hid_t plugin_id, hid_t mem_type_id, void *buf, hid_t dxpl_id, void **req)
 {
     H5VL_class_t *cls;                  /* VOL plugin's class struct */
     herr_t ret_value = SUCCEED;         /* Return value */
@@ -824,14 +953,14 @@ H5VLattr_read(void *attr, hid_t plugin_id, hid_t mem_type_id, void *buf, hid_t d
     FUNC_ENTER_API_NOINIT
 
     /* Check args and get class pointer */
-    if(NULL == attr)
+    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_attr_read(attr, cls, mem_type_id, buf, dxpl_id, req) < 0)
-        HGOTO_ERROR(H5E_VOL, H5E_CANTINIT, FAIL, "unable to read attribute")
+    if(H5VL__attr_read(obj, cls, mem_type_id, buf, dxpl_id, req) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_READERROR, FAIL, "unable to read attribute")
 
 done:
     FUNC_LEAVE_API_NOINIT(ret_value)
@@ -839,7 +968,7 @@ done:
 
 
 /*-------------------------------------------------------------------------
- * Function:	H5VL_attr_write
+ * Function:	H5VL__attr_write
  *
  * Purpose:	Writes data to attr through the VOL
  *
@@ -848,23 +977,60 @@ done:
  *
  *-------------------------------------------------------------------------
  */
-herr_t
-H5VL_attr_write(void *attr, const H5VL_class_t *cls, hid_t mem_type_id, const void *buf, 
+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)
 {
     herr_t ret_value = SUCCEED;         /* Return value */
 
-    FUNC_ENTER_NOAPI(FAIL)
+    FUNC_ENTER_STATIC
 
     /* Check if the corresponding VOL callback exists */
     if(NULL == cls->attr_cls.write)
         HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL plugin has no 'attr write' method")
 
     /* Call the corresponding VOL callback */
-    if((cls->attr_cls.write)(attr, mem_type_id, buf, dxpl_id, req) < 0)
+    if((cls->attr_cls.write)(obj, mem_type_id, buf, dxpl_id, req) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_WRITEERROR, FAIL, "write failed")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5VL__attr_write() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5VL_attr_write
+ *
+ * Purpose:	Writes data to attr through the VOL
+ *
+ * Return:      Success:    Non-negative
+ *              Failure:    Negative
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5VL_attr_write(const H5VL_object_t *vol_obj, hid_t mem_type_id, const void *buf, 
+    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)
+
+    /* 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__attr_write(vol_obj->data, vol_obj->plugin->cls, mem_type_id, buf, dxpl_id, req) < 0)
         HGOTO_ERROR(H5E_VOL, H5E_WRITEERROR, FAIL, "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_attr_write() */
 
@@ -880,7 +1046,7 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5VLattr_write(void *attr, hid_t plugin_id, hid_t mem_type_id, const void *buf,
+H5VLattr_write(void *obj, hid_t plugin_id, hid_t mem_type_id, const void *buf,
     hid_t dxpl_id, void **req)
 {
     H5VL_class_t *cls;                  /* VOL plugin's class struct */
@@ -889,13 +1055,13 @@ H5VLattr_write(void *attr, hid_t plugin_id, hid_t mem_type_id, const void *buf,
     FUNC_ENTER_API_NOINIT
 
     /* Check args and get class pointer */
-    if(NULL == attr)
+    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_attr_write(attr, cls, mem_type_id, buf, dxpl_id, req) < 0)
+    if(H5VL__attr_write(obj, cls, mem_type_id, buf, dxpl_id, req) < 0)
         HGOTO_ERROR(H5E_VOL, H5E_WRITEERROR, FAIL, "unable to write attribute")
 
 done:
@@ -982,9 +1148,41 @@ done:
 
 
 /*-------------------------------------------------------------------------
+ * Function:	H5VL__attr_specific
+ *
+ * Purpose:	Specific operation on attributes through the VOL
+ *
+ * Return:      Success:    Non-negative
+ *              Failure:    Negative
+ *
+ *-------------------------------------------------------------------------
+ */
+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)
+{
+    herr_t ret_value = SUCCEED;         /* Return value */
+
+    FUNC_ENTER_STATIC
+
+    /* Check if the corresponding VOL callback exists */
+    if(NULL == cls->attr_cls.specific)
+        HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL plugin has no 'attr specific' method")
+
+    /* Call the corresponding VOL callback */
+    if((ret_value = (cls->attr_cls.specific)(obj, loc_params, specific_type, dxpl_id, req, arguments)) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTOPERATE, FAIL, "Unable to execute attribute specific callback")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5VL__attr_specific() */
+
+
+/*-------------------------------------------------------------------------
  * Function:	H5VL_attr_specific
  *
- * Purpose:	specific operation on attributes through the VOL
+ * Purpose:	Specific operation on attributes through the VOL
  *
  * Return:      Success:    Non-negative
  *              Failure:    Negative
@@ -992,23 +1190,25 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5VL_attr_specific(void *obj, H5VL_loc_params_t loc_params, const H5VL_class_t *cls, 
+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, ...)
 {
     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.specific)
-        HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL plugin has no 'attr 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((ret_value = (cls->attr_cls.specific)(obj, loc_params, specific_type, dxpl_id, req, arguments)) < 0)
+    if((ret_value = H5VL__attr_specific(vol_obj->data, loc_params, vol_obj->plugin->cls, specific_type, dxpl_id, req, arguments)) < 0)
         HGOTO_ERROR(H5E_VOL, H5E_CANTOPERATE, FAIL, "Unable to execute attribute specific callback")
 
 done:
@@ -1016,6 +1216,10 @@ done:
     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_specific() */
 
@@ -1047,13 +1251,8 @@ H5VLattr_specific(void *obj, H5VL_loc_params_t loc_params, hid_t plugin_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")
 
-    /* Bypass the H5VLint layer */
-    /* Check if the corresponding VOL callback exists */
-    if(NULL == cls->attr_cls.specific)
-        HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL plugin has no `attr specific' method")
-
-    /* Bypass the H5VLint layer, calling the VOL callback directly */
-    if((ret_value = (cls->attr_cls.specific)(obj, loc_params, specific_type, dxpl_id, req, arguments)) < 0)
+    /* Call the corresponding internal VOL routine */
+    if((ret_value = H5VL__attr_specific(obj, loc_params, cls, specific_type, dxpl_id, req, arguments)) < 0)
         HGOTO_ERROR(H5E_VOL, H5E_CANTOPERATE, FAIL, "Unable to execute attribute specific callback")
 
 done:
@@ -1062,9 +1261,9 @@ done:
 
 
 /*-------------------------------------------------------------------------
- * Function:	H5VL_attr_optional
+ * Function:	H5VL__attr_optional
  *
- * Purpose:	optional operation specific to plugins.
+ * Purpose:	Optional operation specific to plugins.
  *
  * Return:      Success:    Non-negative
  *              Failure:    Negative
@@ -1072,22 +1271,56 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5VL_attr_optional(void *obj, const H5VL_class_t *cls, hid_t dxpl_id, void **req, ...)
+H5VL__attr_optional(void *obj, const H5VL_class_t *cls, hid_t dxpl_id,
+    void **req, va_list arguments)
 {
-    va_list arguments;                  /* Argument list passed from the API call */
-    hbool_t arg_started = FALSE;        /* Whether the va_list has been started */
     herr_t ret_value = SUCCEED;         /* Return value */
 
-    FUNC_ENTER_NOAPI(FAIL)
+    FUNC_ENTER_STATIC
 
     /* Check if the corresponding VOL callback exists */
     if(NULL == cls->attr_cls.optional)
         HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL plugin has no 'attr optional' method")
 
     /* Call the corresponding VOL callback */
+    if((cls->attr_cls.optional)(obj, dxpl_id, req, arguments) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTOPERATE, FAIL, "Unable to execute attribute optional callback")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5VL__attr_optional() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:	H5VL_attr_optional
+ *
+ * Purpose:	Optional operation specific to plugins.
+ *
+ * Return:      Success:    Non-negative
+ *              Failure:    Negative
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5VL_attr_optional(const H5VL_object_t *vol_obj, const H5VL_class_t *cls,
+    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)
+
+    /* 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 */
     va_start(arguments, req);
     arg_started = TRUE;
-    if((cls->attr_cls.optional)(obj, dxpl_id, req, arguments) < 0)
+    if(H5VL__attr_optional(vol_obj->data, vol_obj->plugin->cls, dxpl_id, req, arguments) < 0)
         HGOTO_ERROR(H5E_VOL, H5E_CANTOPERATE, FAIL, "Unable to execute attribute optional callback")
 
 done:
@@ -1095,6 +1328,10 @@ done:
     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_optional() */
 
@@ -1124,12 +1361,8 @@ H5VLattr_optional(void *obj, hid_t plugin_id, hid_t dxpl_id, void **req, va_list
     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.optional)
-        HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL plugin has no `attr optional' method")
-
-    /* Bypass the H5VLint layer, calling the VOL callback directly */
-    if((cls->attr_cls.optional)(obj, dxpl_id, req, arguments) < 0)
+    /* Call the corresponding internal VOL routine */
+    if(H5VL__attr_optional(obj, cls, dxpl_id, req, arguments) < 0)
         HGOTO_ERROR(H5E_VOL, H5E_CANTOPERATE, FAIL, "Unable to execute attribute optional callback")
 
 done:
@@ -1138,7 +1371,7 @@ done:
 
 
 /*-------------------------------------------------------------------------
- * Function:    H5VL_attr_close
+ * Function:    H5VL__attr_close
  *
  * Purpose:     Closes an attribute through the VOL
  *
@@ -1147,24 +1380,49 @@ done:
  *
  *-------------------------------------------------------------------------
  */
-herr_t
-H5VL_attr_close(void *attr, const H5VL_class_t *cls, hid_t dxpl_id, void **req)
+static herr_t
+H5VL__attr_close(void *obj, const H5VL_class_t *cls, hid_t dxpl_id, void **req)
 {
     herr_t ret_value = SUCCEED;         /* Return value */
 
-    /* Sanity check */
-    HDassert(attr);
-    HDassert(cls);
-
-    FUNC_ENTER_NOAPI(FAIL)
+    FUNC_ENTER_STATIC
             
     /* Check if the corresponding VOL callback exists */
     if(NULL == cls->attr_cls.close)
         HGOTO_ERROR(H5E_VOL, H5E_UNSUPPORTED, FAIL, "VOL plugin has no 'attr close' method")
 
     /* Call the corresponding VOL callback */
-    if((cls->attr_cls.close)(attr, dxpl_id, req) < 0)
-        HGOTO_ERROR(H5E_VOL, H5E_CANTCLOSEOBJ, FAIL, "close failed")
+    if((cls->attr_cls.close)(obj, dxpl_id, req) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTCLOSEOBJ, FAIL, "attribute close failed")
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5VL__attr_close() */
+
+
+/*-------------------------------------------------------------------------
+ * Function:    H5VL_attr_close
+ *
+ * Purpose:     Closes an attribute through the VOL
+ *
+ * Return:      Success:    Non-negative
+ *              Failure:    Negative
+ *
+ *-------------------------------------------------------------------------
+ */
+herr_t
+H5VL_attr_close(const H5VL_object_t *vol_obj, hid_t dxpl_id, void **req)
+{
+    herr_t ret_value = SUCCEED;         /* Return value */
+
+    FUNC_ENTER_NOAPI(FAIL)
+            
+    /* Sanity check */
+    HDassert(vol_obj);
+
+    /* Call the corresponding internal VOL routine */
+    if(H5VL__attr_close(vol_obj->data, vol_obj->plugin->cls, dxpl_id, req) < 0)
+        HGOTO_ERROR(H5E_VOL, H5E_CANTCLOSEOBJ, FAIL, "attribute close failed")
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
@@ -1182,7 +1440,7 @@ done:
  *-------------------------------------------------------------------------
  */
 herr_t
-H5VLattr_close(void *attr, hid_t plugin_id, hid_t dxpl_id, void **req)
+H5VLattr_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 */
@@ -1191,13 +1449,13 @@ H5VLattr_close(void *attr, hid_t plugin_id, hid_t dxpl_id, void **req)
     H5TRACE4("e", "*xii**x", attr, plugin_id, dxpl_id, req);
 
     /* Check args and get class pointer */
-    if(NULL == attr)
+    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_attr_close(attr, cls, dxpl_id, req) < 0)
+    if(H5VL__attr_close(obj, cls, dxpl_id, req) < 0)
         HGOTO_ERROR(H5E_VOL, H5E_CANTCLOSEOBJ, FAIL, "unable to close attribute")
 
 done:
diff --git a/src/H5VLprivate.h b/src/H5VLprivate.h
index fd44c3b..b2ca1ba 100644
--- a/src/H5VLprivate.h
+++ b/src/H5VLprivate.h
@@ -103,14 +103,14 @@ H5_DLL herr_t H5VL_register_using_existing_id(H5I_type_t type, void *object, H5V
  *****************************/
 
 /* Attribute functions */
-H5_DLL void *H5VL_attr_create(void *obj, H5VL_loc_params_t loc_params, const H5VL_class_t *cls, const char *attr_name, hid_t acpl_id, hid_t aapl_id, hid_t dxpl_id, void **req);
-H5_DLL 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);
-H5_DLL herr_t H5VL_attr_read(void *attr, const H5VL_class_t *cls, hid_t dtype_id, void *buf, hid_t dxpl_id, void **req);
-H5_DLL herr_t H5VL_attr_write(void *attr, const H5VL_class_t *cls, hid_t dtype_id, const void *buf, hid_t dxpl_id, void **req);
+H5_DLL void *H5VL_attr_create(const H5VL_object_t *vol_obj, H5VL_loc_params_t loc_params, const char *attr_name, hid_t acpl_id, hid_t aapl_id, hid_t dxpl_id, void **req);
+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_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, ...);
-H5_DLL herr_t H5VL_attr_optional(void *obj, const H5VL_class_t *cls, hid_t dxpl_id, void **req, ...);
-H5_DLL herr_t H5VL_attr_close(void *attr, const H5VL_class_t *cls, 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);