.

bigfile/_bigfile.c

@@ -51,6 +51,9 @@ typedef struct _frame PyFrameObject;
 // waiting for numpy to start accept it on python2
 #define BIGFILE_USE_OLD_BUFFER  (PY_VERSION_HEX < 0x03000000)
 
+void PyBufferObject_Unpin(PyBufferObject *bufo);
+void PyBuffer_Unpin(Py_buffer *view);
+
 
 /*
  * python representation of VMA - exposes vma memory as python buffer
@@ -544,9 +547,19 @@ out:
     PySys_SetObject("exc_traceback",  Py_None);
 
 
+#if BIGFILE_USE_OLD_BUFFER
+    PyBufferObject *pybufo = (PyBufferObject *)pybuf;
+    PyBufferObject_Unpin(pybufo);
+#else
+    PyMemoryViewObject *pybufm = (PyMemoryViewObject *)pybuf;
+    PyBuffer_Unpin(&pybufm->view);
+#endif
+
+#if 0
     /* verify pybuf is not held - its memory will go away right after return */
     if (pybuf)
         BUG_ON(pybuf->ob_refcnt != 1);
+#endif
 
     /* drop pybuf
      *
@@ -633,22 +646,28 @@ static int pybigfile_storeblk(BigFile *file, blk_t blk, const void *buf)
     /* we need to know only whether storeret != NULL, decref it now */
     Py_XDECREF(storeret);
 
-    /* repoint pybuf to empty region - the original memory attached to it can
+    /* repoint pybuf to empty region - the original memory attached to it can	XXX do the same for loadblk()
      * go away right after we return (if e.g. dirty page was not mapped in any
      * vma), but we need pybuf to stay not corrupt - for printing full
      * traceback in case of storeblk() error. */
 #if BIGFILE_USE_OLD_BUFFER
     PyBufferObject *pybufo = (PyBufferObject *)pybuf;
+    PyBufferObject_Unpin(pybufo);
+/*
     pybufo->b_ptr    = NULL;
     pybufo->b_size   = 0;
     pybufo->b_offset = 0;
     pybufo->b_hash   = -1;
     Py_CLEAR(pybufo->b_base);
+*/
 #else
     PyMemoryViewObject *pybufm = (PyMemoryViewObject *)pybuf;
+    PyBuffer_Unpin(&pybufm->view);
+/*
     pybufm->view.buf = NULL;
     pybufm->view.len = 0;
     Py_CLEAR(pybufm->view.obj);
+*/
 #endif
 
     /* verify that we actually tweaked pybuf ok */
@@ -775,6 +794,23 @@ static /*const*/ PyMethodDef pybigfile_modulemeths[] = {
 };
 
 
+/* buffer utilities: unpin buffer from its buffer - make it zero-length
+ * pointing to NULL but staying a vailid python object */
+void PyBufferObject_Unpin(PyBufferObject *bufo)
+{
+    bufo->b_ptr    = NULL;
+    bufo->b_size   = 0;
+    bufo->b_offset = 0;
+    bufo->b_hash   = -1;
+    Py_CLEAR(bufo->b_base);
+}
+
+void PyBuffer_Unpin(Py_buffer *view)
+{
+    view->buf = NULL;
+    view->len = 0;
+    Py_CLEAR(view->obj);
+}
 
 /* GIL hooks for virtmem big lock */
 static void *py_gil_ensure_unlocked(void)

bigfile/tests/test_basic.py

@@ -151,16 +151,20 @@ def test_pagefault_savestate():
             #     v     .f_localsplus
             #    frame
             #
-            # Since upon returning we can't hold a reference to buf, let's
-            # break the loop explicitly.
-            #
-            # Otherwise both exc_traceback and frame will be alive until next
-            # gc.collect() which cannot be perform in pagefault handler.
-            #
-            # Not breaking this loop will BUG with `buf.refcnt != 1` on return
-            del exc_traceback
+
+            # # Since upon returning we can't hold a reference to buf, let's
+            # # break the loop explicitly.
+            # #
+            # # Otherwise both exc_traceback and frame will be alive until next
+            # # gc.collect() which cannot be perform in pagefault handler.
+            # #
+            # # Not breaking this loop will BUG with `buf.refcnt != 1` on return
+            # del exc_traceback
+
+            assert len(buf) > 0
 
             self.loadblk_run = 1
+            self.loadblk_buf = buf
 
 
     f   = BadFile(PS)
@@ -184,6 +188,11 @@ def test_pagefault_savestate():
         assert exc_value is exc_value2
         assert exc_tb    is exc_tb2
 
+        # TODO check f.loadblk_buf for access -- len=0, read/write - index error
+        assert len(f.loadblk_buf) == 0
+        raises(IndexError, "f.loadblk_buf[0]")
+        raises(IndexError, "f.loadblk_buf[0] = b'1'")
+
 
     # TODO close f
 

include/wendelin/compat_py2.h

@@ -58,6 +58,7 @@ static inline PyThreadState * _PyThreadState_UncheckedGet(void)
 {
     return _PyThreadState_Current;
 }
+
 /* _PyThreadState_UncheckedGet() was added in CPython 3.5.2rc1
  * https://github.com/python/cpython/commit/df858591
  *