Merge PR #274 to 1.12 Branch (#283)

* Improve performance of multiple calls to H5Sget_select_elem_pointlist (#270)

* Cache the pointer to the next point to process after the last call to
H5S__get_select_elem_pointlist.  This allows the normal process of
iterating over the points in batches to be much more efficient, as the
library does not need to traverse the entirety of the preceding points
every time the funciton is re-entered.

* Update RELEASE.txt for point selection iteration performance fix.

* Fix problems with vlens and refs inside compound using H5VLget_file_type() (#274)

* Fixed problems with vlens and refs inside compound using H5VLget_file_type()

* Fix date in RELEASE.txt

* Add assertions

* Move some manipulation of H5VL_object_t struct fields into the H5VL
package.

* Add fix that was mistakenly left off merge commit.

* Update src/H5Tprivate.h

Co-authored-by: Larry Knox <lrknox@hdfgroup.org>

13 files changed, 191 insertions, 36 deletions

diff --git a/release_docs/RELEASE.txt b/release_docs/RELEASE.txt
index 20acd49..fe9d1f8 100644
--- a/release_docs/RELEASE.txt
+++ b/release_docs/RELEASE.txt
@@ -242,6 +242,15 @@ Bug Fixes since HDF5-1.12.0 release
 ==================================
     Library
     -------
+    - Fixed problems with vlens and refs inside compound using
+      H5VLget_file_type()
+
+        Modified library to properly ref count H5VL_object_t structs and only
+        consider file vlen and reference types to be equal if their files are
+        the same.
+
+        (NAF - 2021/01/22)
+
     - Fix bug and simplify collective metadata write operation when some ranks
         have no entries to contribute.  This fixes parallel regression test
         failures with IBM SpectrumScale MPI on the Summit system at ORNL.
diff --git a/src/H5Odtype.c b/src/H5Odtype.c
index b6e986d..c1effad 100644
--- a/src/H5Odtype.c
+++ b/src/H5Odtype.c
@@ -579,8 +579,10 @@ H5O__dtype_decode_helper(unsigned *ioflags /*in,out*/, const uint8_t **pp, H5T_t
 done:
     if (ret_value < 0)
         if (dt != NULL) {
-            if (dt->shared != NULL)
+            if (dt->shared != NULL) {
+                HDassert(!dt->shared->owned_vol_obj);
                 dt->shared = H5FL_FREE(H5T_shared_t, dt->shared);
+            } /* end if */
             dt = H5FL_FREE(H5T_t, dt);
         } /* end if */
 
diff --git a/src/H5T.c b/src/H5T.c
index c145a04..6f9fa13 100644
--- a/src/H5T.c
+++ b/src/H5T.c
@@ -1477,6 +1477,8 @@ done:
             if (copied_dtype)
                 (void)H5T_close_real(dt);
             else {
+                if (dt->shared->owned_vol_obj && H5VL_free_object(dt->shared->owned_vol_obj) < 0)
+                    HDONE_ERROR(H5E_DATATYPE, H5E_CANTCLOSEOBJ, FAIL, "unable to close owned VOL object")
                 dt->shared = H5FL_FREE(H5T_shared_t, dt->shared);
                 dt         = H5FL_FREE(H5T_t, dt);
             } /* end else */
@@ -3384,6 +3386,8 @@ H5T__create(H5T_class_t type, size_t size)
 done:
     if (NULL == ret_value) {
         if (dt) {
+            if (dt->shared->owned_vol_obj && H5VL_free_object(dt->shared->owned_vol_obj) < 0)
+                HDONE_ERROR(H5E_DATATYPE, H5E_CANTCLOSEOBJ, NULL, "unable to close owned VOL object")
             dt->shared = H5FL_FREE(H5T_shared_t, dt->shared);
             dt         = H5FL_FREE(H5T_t, dt);
         }
@@ -3426,9 +3430,12 @@ H5T__initiate_copy(const H5T_t *old_dt)
     /* Copy shared information */
     *(new_dt->shared) = *(old_dt->shared);
 
-    /* Reset VOL fields */
+    /* Increment ref count on owned VOL object */
+    if (new_dt->shared->owned_vol_obj)
+        (void)H5VL_object_inc_rc(new_dt->shared->owned_vol_obj);
+
+    /* Reset vol_obj field */
     new_dt->vol_obj               = NULL;
-    new_dt->shared->owned_vol_obj = NULL;
 
     /* Set return value */
     ret_value = new_dt;
@@ -3436,8 +3443,11 @@ H5T__initiate_copy(const H5T_t *old_dt)
 done:
     if (ret_value == NULL)
         if (new_dt) {
-            if (new_dt->shared)
+            if (new_dt->shared) {
+                if (new_dt->shared->owned_vol_obj && H5VL_free_object(new_dt->shared->owned_vol_obj) < 0)
+                    HDONE_ERROR(H5E_DATATYPE, H5E_CANTCLOSEOBJ, NULL, "unable to close owned VOL object")
                 new_dt->shared = H5FL_FREE(H5T_shared_t, new_dt->shared);
+            } /* end if */
             new_dt = H5FL_FREE(H5T_t, new_dt);
         } /* end if */
 
@@ -3766,6 +3776,8 @@ done:
     if (ret_value == NULL)
         if (new_dt) {
             HDassert(new_dt->shared);
+            if (new_dt->shared->owned_vol_obj && H5VL_free_object(new_dt->shared->owned_vol_obj) < 0)
+                HDONE_ERROR(H5E_DATATYPE, H5E_CANTCLOSEOBJ, NULL, "unable to close owned VOL object")
             new_dt->shared = H5FL_FREE(H5T_shared_t, new_dt->shared);
             new_dt         = H5FL_FREE(H5T_t, new_dt);
         } /* end if */
@@ -3833,6 +3845,8 @@ H5T_copy_reopen(H5T_t *old_dt)
             /* The object is already open.  Free the H5T_shared_t struct
              * we had been using and use the one that already exists.
              * Not terribly efficient. */
+            if (new_dt->shared->owned_vol_obj && H5VL_free_object(new_dt->shared->owned_vol_obj) < 0)
+                HGOTO_ERROR(H5E_DATATYPE, H5E_CANTCLOSEOBJ, NULL, "unable to close owned VOL object")
             new_dt->shared = H5FL_FREE(H5T_shared_t, new_dt->shared);
             new_dt->shared = reopened_fo;
 
@@ -3869,6 +3883,8 @@ done:
     if (ret_value == NULL)
         if (new_dt) {
             HDassert(new_dt->shared);
+            if (new_dt->shared->owned_vol_obj && H5VL_free_object(new_dt->shared->owned_vol_obj) < 0)
+                HDONE_ERROR(H5E_DATATYPE, H5E_CANTCLOSEOBJ, NULL, "unable to close owned VOL object")
             new_dt->shared = H5FL_FREE(H5T_shared_t, new_dt->shared);
             new_dt         = H5FL_FREE(H5T_t, new_dt);
         } /* end if */
@@ -3963,8 +3979,10 @@ H5T__alloc(void)
 done:
     if (ret_value == NULL)
         if (dt) {
-            if (dt->shared)
+            if (dt->shared) {
+                HDassert(!dt->shared->owned_vol_obj);
                 dt->shared = H5FL_FREE(H5T_shared_t, dt->shared);
+            } /* end if */
             dt = H5FL_FREE(H5T_t, dt);
         } /* end if */
 
@@ -4085,6 +4103,7 @@ H5T_close_real(H5T_t *dt)
         if (H5T__free(dt) < 0)
             HGOTO_ERROR(H5E_DATATYPE, H5E_CANTFREE, FAIL, "unable to free datatype");
 
+        HDassert(!dt->shared->owned_vol_obj);
         dt->shared = H5FL_FREE(H5T_shared_t, dt->shared);
     } /* end if */
     else
@@ -4219,6 +4238,7 @@ H5T__set_size(H5T_t *dt, size_t size)
 
     /* Check args */
     HDassert(dt);
+    HDassert(dt->shared);
     HDassert(size != 0);
     HDassert(H5T_REFERENCE != dt->shared->type);
     HDassert(!(H5T_ENUM == dt->shared->type && 0 == dt->shared->u.enumer.nmembs));
@@ -4406,11 +4426,38 @@ H5T_get_size(const H5T_t *dt)
 
     /* check args */
     HDassert(dt);
+    HDassert(dt->shared);
 
     FUNC_LEAVE_NOAPI(dt->shared->size)
 } /* end H5T_get_size() */
 
 /*-------------------------------------------------------------------------
+ * Function:  H5T_get_force_conv
+ *
+ * Purpose:   Determines if the type has forced conversion. This will be
+ *            true if and only if the type keeps a pointer to a file VOL
+ *            object internally.
+ *
+ * Return:    TRUE/FALSE (never fails)
+ *
+ * Programmer:    Neil Fortner
+ *        Thursday, January  21, 2021
+ *-------------------------------------------------------------------------
+ */
+hbool_t
+H5T_get_force_conv(const H5T_t *dt)
+{
+    /* Use FUNC_ENTER_NOAPI_NOINIT_NOERR here to avoid performance issues */
+    FUNC_ENTER_NOAPI_NOINIT_NOERR
+
+    /* check args */
+    HDassert(dt);
+    HDassert(dt->shared);
+
+    FUNC_LEAVE_NOAPI(dt->shared->force_conv)
+} /* end H5T_get_force_conv() */
+
+/*-------------------------------------------------------------------------
  * Function:  H5T_cmp
  *
  * Purpose:   Compares two data types.
@@ -4446,6 +4493,9 @@ H5T_cmp(const H5T_t *dt1, const H5T_t *dt2, hbool_t superset)
     if (dt1 == dt2)
         HGOTO_DONE(0);
 
+    HDassert(dt1->shared);
+    HDassert(dt2->shared);
+
     /* compare */
     if (dt1->shared->type < dt2->shared->type)
         HGOTO_DONE(-1);
@@ -4851,6 +4901,10 @@ H5T_cmp(const H5T_t *dt1, const H5T_t *dt2, hbool_t superset)
                         HGOTO_DONE(-1);
                     if (dt1->shared->u.atomic.u.r.loc > dt2->shared->u.atomic.u.r.loc)
                         HGOTO_DONE(1);
+                    if (dt1->shared->u.atomic.u.r.file < dt2->shared->u.atomic.u.r.file)
+                        HGOTO_DONE(-1);
+                    if (dt1->shared->u.atomic.u.r.file > dt2->shared->u.atomic.u.r.file)
+                        HGOTO_DONE(1);
                     break;
 
                 case H5T_NO_CLASS:
@@ -6229,6 +6283,7 @@ H5T_own_vol_obj(H5T_t *dt, H5VL_object_t *vol_obj)
 
     /* Take ownership */
     dt->shared->owned_vol_obj = vol_obj;
+    (void)H5VL_object_inc_rc(vol_obj);
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
diff --git a/src/H5Tcommit.c b/src/H5Tcommit.c
index 3eecfb3..989f9a5 100644
--- a/src/H5Tcommit.c
+++ b/src/H5Tcommit.c
@@ -147,11 +147,8 @@ H5Tcommit2(hid_t loc_id, const char *name, hid_t type_id, hid_t lcpl_id, hid_t t
         HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "unable to commit datatype")
 
     /* Set up VOL object */
-    if (NULL == (new_obj = H5FL_CALLOC(H5VL_object_t)))
-        HGOTO_ERROR(H5E_DATATYPE, H5E_CANTALLOC, FAIL, "can't allocate top object structure")
-    new_obj->connector = vol_obj->connector;
-    new_obj->connector->nrefs++;
-    new_obj->data = data;
+    if (NULL == (new_obj = H5VL_create_object(data, vol_obj->connector)))
+        HGOTO_ERROR(H5E_DATATYPE, H5E_CANTALLOC, FAIL, "can't create VOL object for committed datatype")
 
     /* Set the committed type object to the VOL connector pointer in the H5T_t struct */
     dt->vol_obj = new_obj;
@@ -301,11 +298,8 @@ H5Tcommit_anon(hid_t loc_id, hid_t type_id, hid_t tcpl_id, hid_t tapl_id)
         HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "unable to commit datatype")
 
     /* Setup VOL object */
-    if (NULL == (new_obj = H5FL_CALLOC(H5VL_object_t)))
-        HGOTO_ERROR(H5E_DATATYPE, H5E_CANTALLOC, FAIL, "can't allocate top object structure")
-    new_obj->connector = vol_obj->connector;
-    new_obj->connector->nrefs++;
-    new_obj->data = dt;
+    if (NULL == (new_obj = H5VL_create_object(dt, vol_obj->connector)))
+        HGOTO_ERROR(H5E_DATATYPE, H5E_CANTALLOC, FAIL, "can't create VOL object for committed datatype")
 
     /* Set the committed type object to the VOL connector pointer in the H5T_t struct */
     type->vol_obj = new_obj;
@@ -976,8 +970,11 @@ H5T_open(const H5G_loc_t *loc)
 done:
     if (ret_value == NULL) {
         if (dt) {
-            if (shared_fo == NULL) /* Need to free shared fo */
+            if (shared_fo == NULL) { /* Need to free shared fo */
+                if (dt->shared->owned_vol_obj && H5VL_free_object(dt->shared->owned_vol_obj) < 0)
+                    HDONE_ERROR(H5E_DATATYPE, H5E_CANTCLOSEOBJ, NULL, "unable to close owned VOL object")
                 dt->shared = H5FL_FREE(H5T_shared_t, dt->shared);
+            } /* end if */
 
             H5O_loc_free(&(dt->oloc));
             H5G_name_free(&(dt->path));
diff --git a/src/H5Tconv.c b/src/H5Tconv.c
index d8e4759..92b8ae1 100644
--- a/src/H5Tconv.c
+++ b/src/H5Tconv.c
@@ -2010,7 +2010,7 @@ H5T__conv_struct_init(H5T_t *src, H5T_t *dst, H5T_cdata_t *cdata)
         priv->subset_info.copy_size = 0;
 
         /*
-         * Insure that members are sorted.
+         * Ensure that members are sorted.
          */
         H5T__sort_value(src, NULL);
         H5T__sort_value(dst, NULL);
diff --git a/src/H5Tdeprec.c b/src/H5Tdeprec.c
index 89de9e1..fa14151 100644
--- a/src/H5Tdeprec.c
+++ b/src/H5Tdeprec.c
@@ -134,11 +134,8 @@ H5Tcommit1(hid_t loc_id, const char *name, hid_t type_id)
         HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "unable to commit datatype")
 
     /* Set up VOL object */
-    if (NULL == (new_obj = H5FL_CALLOC(H5VL_object_t)))
-        HGOTO_ERROR(H5E_VOL, H5E_NOSPACE, FAIL, "can't allocate top object structure")
-    new_obj->connector = vol_obj->connector;
-    new_obj->connector->nrefs++;
-    new_obj->data = data;
+    if (NULL == (new_obj = H5VL_create_object(data, vol_obj->connector)))
+        HGOTO_ERROR(H5E_DATATYPE, H5E_CANTALLOC, FAIL, "can't create VOL object for committed datatype")
 
     /* Set the committed type object to the VOL connector pointer in the H5T_t struct */
     dt->vol_obj = new_obj;
diff --git a/src/H5Tpkg.h b/src/H5Tpkg.h
index 4f3d89d..4b96e12 100644
--- a/src/H5Tpkg.h
+++ b/src/H5Tpkg.h
@@ -859,7 +859,7 @@ H5_DLL void     H5T__bit_neg(uint8_t *buf, size_t start, size_t size);
 /* VL functions */
 H5_DLL H5T_t *H5T__vlen_create(const H5T_t *base);
 H5_DLL herr_t H5T__vlen_reclaim(void *elem, const H5T_t *dt, H5T_vlen_alloc_info_t *alloc_info);
-H5_DLL htri_t H5T__vlen_set_loc(const H5T_t *dt, H5VL_object_t *file, H5T_loc_t loc);
+H5_DLL htri_t H5T__vlen_set_loc(H5T_t *dt, H5VL_object_t *file, H5T_loc_t loc);
 
 /* Array functions */
 H5_DLL H5T_t *H5T__array_create(H5T_t *base, unsigned ndims, const hsize_t dim[/* ndims */]);
@@ -868,7 +868,7 @@ H5_DLL int    H5T__get_array_dims(const H5T_t *dt, hsize_t dims[]);
 
 /* Reference functions */
 H5_DLL herr_t H5T__ref_reclaim(void *elem, const H5T_t *dt);
-H5_DLL htri_t H5T__ref_set_loc(const H5T_t *dt, H5VL_object_t *file, H5T_loc_t loc);
+H5_DLL htri_t H5T__ref_set_loc(H5T_t *dt, H5VL_object_t *file, H5T_loc_t loc);
 
 /* Compound functions */
 H5_DLL herr_t H5T__insert(H5T_t *parent, const char *name, size_t offset, const H5T_t *member);
diff --git a/src/H5Tprivate.h b/src/H5Tprivate.h
index b3dc064..97804f1 100644
--- a/src/H5Tprivate.h
+++ b/src/H5Tprivate.h
@@ -41,11 +41,13 @@ typedef struct H5T_t H5T_t;
 #define H5T_GET_SHARED(T)           ((T)->shared)
 #define H5T_GET_MEMBER_OFFSET(T, I) ((T)->u.compnd.memb[I].offset)
 #define H5T_GET_MEMBER_SIZE(T, I)   ((T)->u.compnd.memb[I].shared->size)
+#define H5T_GET_FORCE_CONV(T)       ((T)->shared->force_conv)
 #else /* H5T_MODULE */
 #define H5T_GET_SIZE(T)             (H5T_get_size(T))
 #define H5T_GET_SHARED(T)           (H5T_get_shared(T))
 #define H5T_GET_MEMBER_OFFSET(T, I) (H5T_get_member_offset((T), (I)))
 #define H5T_GET_MEMBER_SIZE(T, I)   (H5T_get_member_size((T), (I)))
+#define H5T_GET_FORCE_CONV(T)       (H5T_get_force_conv(T))
 #endif /* H5T_MODULE */
 
 /* Forward references of package typedefs (declared in H5Tpkg.h) */
@@ -114,6 +116,7 @@ H5_DLL H5T_t *     H5T_get_super(const H5T_t *dt);
 H5_DLL H5T_class_t H5T_get_class(const H5T_t *dt, htri_t internal);
 H5_DLL htri_t      H5T_detect_class(const H5T_t *dt, H5T_class_t cls, hbool_t from_api);
 H5_DLL size_t      H5T_get_size(const H5T_t *dt);
+H5_DLL hbool_t     H5T_get_force_conv(const H5T_t *dt);
 H5_DLL int         H5T_cmp(const H5T_t *dt1, const H5T_t *dt2, hbool_t superset);
 H5_DLL herr_t      H5T_encode(H5T_t *obj, unsigned char *buf, size_t *nalloc);
 H5_DLL H5T_t *           H5T_decode(size_t buf_size, const unsigned char *buf);
diff --git a/src/H5Tref.c b/src/H5Tref.c
index 0c17d49..bea0963 100644
--- a/src/H5Tref.c
+++ b/src/H5Tref.c
@@ -156,7 +156,7 @@ static const H5T_ref_class_t H5T_ref_dsetreg_disk_g = {
  *-------------------------------------------------------------------------
  */
 htri_t
-H5T__ref_set_loc(const H5T_t *dt, H5VL_object_t *file, H5T_loc_t loc)
+H5T__ref_set_loc(H5T_t *dt, H5VL_object_t *file, H5T_loc_t loc)
 {
     htri_t ret_value = FALSE; /* Indicate success, but no location change */
 
@@ -180,6 +180,13 @@ H5T__ref_set_loc(const H5T_t *dt, H5VL_object_t *file, H5T_loc_t loc)
             /* Mark this type as being stored in memory */
             dt->shared->u.atomic.u.r.loc = H5T_LOC_MEMORY;
 
+            /* Release owned file */
+            if (dt->shared->owned_vol_obj) {
+                if(H5VL_free_object(dt->shared->owned_vol_obj) < 0)
+                    HGOTO_ERROR(H5E_REFERENCE, H5E_CANTCLOSEOBJ, FAIL, "unable to close owned VOL object")
+                dt->shared->owned_vol_obj = NULL;
+            } /* end if */
+
             /* Reset file ID (since this reference is in memory) */
             dt->shared->u.atomic.u.r.file = file; /* file is NULL */
 
@@ -220,6 +227,10 @@ H5T__ref_set_loc(const H5T_t *dt, H5VL_object_t *file, H5T_loc_t loc)
             /* Set file pointer (since this reference is on disk) */
             dt->shared->u.atomic.u.r.file = file;
 
+            /* dt now owns a reference to file */
+            if (H5T_own_vol_obj(dt, file) < 0)
+                HGOTO_ERROR(H5E_REFERENCE, H5E_CANTINIT, FAIL, "can't give ownership of VOL object")
+
             if (dt->shared->u.atomic.u.r.rtype == H5R_OBJECT1) {
                 H5F_t *f;
 
diff --git a/src/H5Tvlen.c b/src/H5Tvlen.c
index 2d373d1..4564e0a 100644
--- a/src/H5Tvlen.c
+++ b/src/H5Tvlen.c
@@ -245,7 +245,7 @@ done:
  *-------------------------------------------------------------------------
  */
 htri_t
-H5T__vlen_set_loc(const H5T_t *dt, H5VL_object_t *file, H5T_loc_t loc)
+H5T__vlen_set_loc(H5T_t *dt, H5VL_object_t *file, H5T_loc_t loc)
 {
     H5VL_file_cont_info_t cont_info = {H5VL_CONTAINER_INFO_VERSION, 0, 0, 0};
     htri_t                ret_value = FALSE; /* Indicate success, but no location change */
@@ -282,6 +282,13 @@ H5T__vlen_set_loc(const H5T_t *dt, H5VL_object_t *file, H5T_loc_t loc)
                 else
                     HDassert(0 && "Invalid VL type");
 
+                /* Release owned file */
+                if (dt->shared->owned_vol_obj) {
+                    if(H5VL_free_object(dt->shared->owned_vol_obj) < 0)
+                        HGOTO_ERROR(H5E_DATATYPE, H5E_CANTCLOSEOBJ, FAIL, "unable to close owned VOL object")
+                    dt->shared->owned_vol_obj = NULL;
+                } /* end if */
+
                 /* Reset file pointer (since this VL is in memory) */
                 dt->shared->u.vlen.file = NULL;
                 break;
@@ -307,6 +314,10 @@ H5T__vlen_set_loc(const H5T_t *dt, H5VL_object_t *file, H5T_loc_t loc)
 
                 /* Set file ID (since this VL is on disk) */
                 dt->shared->u.vlen.file = file;
+
+                /* dt now owns a reference to file */
+                if (H5T_own_vol_obj(dt, file) < 0)
+                    HGOTO_ERROR(H5E_DATATYPE, H5E_CANTINIT, FAIL, "can't give ownership of VOL object")
                 break;
 
             case H5T_LOC_BADLOC:
diff --git a/src/H5VL.c b/src/H5VL.c
index 92b1e4c..2e63ed9 100644
--- a/src/H5VL.c
+++ b/src/H5VL.c
@@ -704,8 +704,9 @@ H5VLget_file_type(void *file_obj, hid_t connector_id, hid_t dtype_id)
     if (NULL == (dtype = (H5T_t *)H5I_object_verify(dtype_id, H5I_DATATYPE)))
         HGOTO_ERROR(H5E_ARGS, H5E_BADTYPE, FAIL, "not a data type")
 
-    /* Create VOL object for file */
-    if (NULL == (file_vol_obj = H5VL_create_object_using_vol_id(H5I_FILE, file_obj, connector_id)))
+    /* Create VOL object for file if necessary (force_conv will be TRUE if and
+     * only if file needs to be passed to H5T_set_loc) */
+    if (H5T_GET_FORCE_CONV(dtype) && (NULL == (file_vol_obj = H5VL_create_object_using_vol_id(H5I_FILE, file_obj, connector_id))))
         HGOTO_ERROR(H5E_VOL, H5E_CANTCREATE, FAIL, "can't create VOL object")
 
     /* Copy the datatype */
@@ -722,10 +723,12 @@ H5VLget_file_type(void *file_obj, hid_t connector_id, hid_t dtype_id)
     if (H5T_set_loc(file_type, file_vol_obj, H5T_LOC_DISK) < 0)
         HGOTO_ERROR(H5E_VOL, H5E_CANTINIT, FAIL, "can't set datatype location")
 
-    /* file_type now owns file_vol_obj */
-    if (H5T_own_vol_obj(file_type, file_vol_obj) < 0)
-        HGOTO_ERROR(H5E_VOL, H5E_CANTINIT, FAIL, "can't give ownership of VOL object")
-    file_vol_obj = NULL;
+    /* Release our reference to file_type */
+    if (file_vol_obj) {
+        if (H5VL_free_object(file_vol_obj) < 0)
+            HGOTO_ERROR(H5E_VOL, H5E_CANTDEC, FAIL, "unable to free VOL object")
+        file_vol_obj = NULL;
+    } /* end if */
 
     /* Set return value */
     ret_value = file_type_id;
diff --git a/src/H5VLint.c b/src/H5VLint.c
index aed397b..b44d436 100644
--- a/src/H5VLint.c
+++ b/src/H5VLint.c
@@ -570,6 +570,7 @@ H5VL__new_vol_obj(H5I_type_t type, void *object, H5VL_t *vol_connector, hbool_t
     } /* end if */
     else
         new_vol_obj->data = object;
+    new_vol_obj->rc = 1;
 
     /* Bump the reference count on the VOL connector */
     H5VL__conn_inc_rc(vol_connector);
@@ -816,6 +817,46 @@ done:
 } /* end H5VL_register_using_vol_id() */
 
 /*-------------------------------------------------------------------------
+ * Function:    H5VL_create_object
+ *
+ * Purpose:     Similar to H5VL_register but does not create an ID.
+ *              Creates a new VOL object for the provided generic object
+ *              using the provided vol connector.  Should only be used for
+ *              internal objects returned from the connector such as
+ *              requests.
+ *
+ * Return:      Success:    A valid VOL object
+ *              Failure:    NULL
+ *
+ *-------------------------------------------------------------------------
+ */
+H5VL_object_t *
+H5VL_create_object(void *object, H5VL_t *vol_connector)
+{
+    H5VL_object_t *ret_value = NULL; /* Return value */
+
+    FUNC_ENTER_NOAPI(NULL)
+
+    /* Check arguments */
+    HDassert(object);
+    HDassert(vol_connector);
+
+    /* Set up VOL object for the passed-in data */
+    /* (Does not wrap object, since it's from a VOL callback) */
+    if (NULL == (ret_value = H5FL_CALLOC(H5VL_object_t)))
+        HGOTO_ERROR(H5E_VOL, H5E_CANTALLOC, NULL, "can't allocate memory for VOL object")
+    ret_value->connector = vol_connector;
+    ret_value->data      = object;
+    ret_value->rc        = 1;
+
+    /* Bump the reference count on the VOL connector */
+    H5VL__conn_inc_rc(vol_connector);
+
+done:
+    FUNC_LEAVE_NOAPI(ret_value)
+} /* end H5VL_create_object() */
+
+/*-------------------------------------------------------------------------
  * Function:	H5VL_create_object_using_vol_id
  *
  * Purpose:     Similar to H5VL_register_using_vol_id but does not create
@@ -939,6 +980,27 @@ done:
 } /* end H5VL__conn_dec_rc() */
 
 /*-------------------------------------------------------------------------
+ * Function:    H5VL_object_inc_rc
+ *
+ * Purpose:     Wrapper to increment the ref count on a VOL object.
+ *
+ * Return:      SUCCEED/FAIL
+ *
+ *-------------------------------------------------------------------------
+ */
+hsize_t
+H5VL_object_inc_rc(H5VL_object_t *vol_obj)
+{
+    FUNC_ENTER_NOAPI_NOERR_NOFS
+
+    /* Check arguments */
+    HDassert(vol_obj);
+
+    /* Increment refcount for object and return */
+    FUNC_LEAVE_NOAPI(++vol_obj->rc)
+} /* end H5VL_object_inc_rc() */
+
+/*-------------------------------------------------------------------------
  * Function:    H5VL_free_object
  *
  * Purpose:     Wrapper to unregister an object ID with a VOL aux struct
@@ -958,11 +1020,13 @@ H5VL_free_object(H5VL_object_t *vol_obj)
     /* Check arguments */
     HDassert(vol_obj);
 
-    /* Decrement refcount on connector */
-    if (H5VL__conn_dec_rc(vol_obj->connector) < 0)
-        HGOTO_ERROR(H5E_VOL, H5E_CANTDEC, FAIL, "unable to decrement ref count on VOL connector")
+    if(--vol_obj->rc == 0) {
+        /* Decrement refcount on connector */
+        if (H5VL__conn_dec_rc(vol_obj->connector) < 0)
+            HGOTO_ERROR(H5E_VOL, H5E_CANTDEC, FAIL, "unable to decrement ref count on VOL connector")
 
-    vol_obj = H5FL_FREE(H5VL_object_t, vol_obj);
+        vol_obj = H5FL_FREE(H5VL_object_t, vol_obj);
+    } /* end if */
 
 done:
     FUNC_LEAVE_NOAPI(ret_value)
diff --git a/src/H5VLprivate.h b/src/H5VLprivate.h
index 581a24d..e3ff040 100644
--- a/src/H5VLprivate.h
+++ b/src/H5VLprivate.h
@@ -37,6 +37,7 @@ typedef struct H5VL_t {
 typedef struct H5VL_object_t {
     void *  data;      /* Pointer to connector-managed data for this object    */
     H5VL_t *connector; /* Pointer to VOL connector struct                      */
+    size_t rc;         /* Reference count                                      */
 } H5VL_object_t;
 
 /* Internal structure to hold the connector ID & info for FAPLs */
@@ -86,7 +87,9 @@ H5_DLL void *H5VL_object_data(const H5VL_object_t *vol_obj);
 H5_DLL void *H5VL_object_unwrap(const H5VL_object_t *vol_obj);
 H5_DLL void *H5VL_object_verify(hid_t id, H5I_type_t obj_type);
 H5_DLL H5VL_object_t *H5VL_vol_object(hid_t id);
+H5_DLL H5VL_object_t *H5VL_create_object(void *object, H5VL_t *vol_connector);
 H5_DLL H5VL_object_t *H5VL_create_object_using_vol_id(H5I_type_t type, void *obj, hid_t connector_id);
+H5_DLL hsize_t        H5VL_object_inc_rc(H5VL_object_t *obj);
 H5_DLL herr_t         H5VL_free_object(H5VL_object_t *obj);
 H5_DLL herr_t         H5VL_object_is_native(const H5VL_object_t *obj, hbool_t *is_native);
 H5_DLL herr_t         H5VL_file_is_same(const H5VL_object_t *vol_obj1, const H5VL_object_t *vol_obj2,