Add flags parameter on mmap.flush

Author: aisk

Doc/library/mmap.rst

@@ -212,7 +212,7 @@ To map anonymous memory, -1 should be passed as the fileno along with the length
          Writable :term:`bytes-like object` is now accepted.
 
 
-   .. method:: flush([offset[, size]])
+   .. method:: flush([offset[, size]], *, flags=MS_SYNC)
 
       Flushes changes made to the in-memory copy of a file back to disk. Without
       use of this call there is no guarantee that changes are written back before
@@ -221,6 +221,12 @@ To map anonymous memory, -1 should be passed as the fileno along with the length
       whole extent of the mapping is flushed.  *offset* must be a multiple of the
       :const:`PAGESIZE` or :const:`ALLOCATIONGRANULARITY`.
 
+      The *flags* parameter specifies the synchronization behavior.
+      *flags* must be one of the :ref:`MS_* constants <ms-constants>` available
+      on the system.
+
+      On Windows, the *flags* parameter is ignored.
+
       ``None`` is returned to indicate success.  An exception is raised when the
       call failed.
 
@@ -235,6 +241,9 @@ To map anonymous memory, -1 should be passed as the fileno along with the length
          specified alone, and the flush operation will extend from *offset*
          to the end of the mmap.
 
+      .. versionchanged:: next
+         Added *flags* parameter to control synchronization behavior.
+
 
    .. method:: madvise(option[, start[, length]])
 
@@ -450,3 +459,22 @@ MAP_* Constants
        :data:`MAP_TPRO`, :data:`MAP_TRANSLATED_ALLOW_EXECUTE`, and
        :data:`MAP_UNIX03` constants.
 
+.. _ms-constants:
+
+MS_* Constants
+++++++++++++++
+
+.. data:: MS_SYNC
+          MS_ASYNC
+          MS_INVALIDATE
+
+    These flags control the synchronization behavior for :meth:`mmap.flush`:
+
+    * :data:`MS_SYNC` - Synchronous flush: writes are scheduled and the call
+      blocks until they are physically written to storage.
+    * :data:`MS_ASYNC` - Asynchronous flush: writes are scheduled but the call
+      returns immediately without waiting for completion.
+    * :data:`MS_INVALIDATE` - Invalidate cached data: invalidates other mappings
+      of the same file so they can see the changes.
+
+    .. versionadded:: next

Lib/test/test_mmap.py

@@ -1157,6 +1157,15 @@ def test_flush_parameters(self):
             m.flush(PAGESIZE)
             m.flush(PAGESIZE, PAGESIZE)
 
+            if hasattr(mmap, 'MS_SYNC'):
+                m.flush(0, PAGESIZE, flags=mmap.MS_SYNC)
+            if hasattr(mmap, 'MS_ASYNC'):
+                m.flush(flags=mmap.MS_ASYNC)
+            if hasattr(mmap, 'MS_INVALIDATE'):
+                m.flush(PAGESIZE * 2, flags=mmap.MS_INVALIDATE)
+            if hasattr(mmap, 'MS_ASYNC') and hasattr(mmap, 'MS_INVALIDATE'):
+                m.flush(0, PAGESIZE, flags=mmap.MS_ASYNC | mmap.MS_INVALIDATE)
+
 
 class LargeMmapTests(unittest.TestCase):
 

Misc/NEWS.d/next/Core_and_Builtins/2025-10-04-20-48-02.gh-issue-63016.EC9QN_.rst

@@ -0,0 +1 @@
+Add a ``flags`` parameter to :meth:`mmap.mmap.flush` to control synchronization behavior.

Modules/mmapmodule.c

@@ -930,13 +930,16 @@ mmap_tell_method(PyObject *op, PyObject *Py_UNUSED(ignored))
 }
 
 static PyObject *
-mmap_flush_method(PyObject *op, PyObject *args)
+mmap_flush_method(PyObject *op, PyObject *args, PyObject *kwargs)
 {
     Py_ssize_t offset = 0;
     Py_ssize_t size = -1;
+    int flags = MS_SYNC;
     mmap_object *self = mmap_object_CAST(op);
+    static char *kwlist[] = {"offset", "size", "flags", NULL};
     CHECK_VALID(NULL);
-    if (!PyArg_ParseTuple(args, "|nn:flush", &offset, &size)) {
+    if (!PyArg_ParseTupleAndKeywords(args, kwargs, "|nn$i:flush", kwlist,
+                                     &offset, &size, &flags)) {
         return NULL;
     }
     if (size == -1) {
@@ -957,8 +960,7 @@ mmap_flush_method(PyObject *op, PyObject *args)
     }
     Py_RETURN_NONE;
 #elif defined(UNIX)
-    /* XXX flags for msync? */
-    if (-1 == msync(self->data + offset, size, MS_SYNC)) {
+    if (-1 == msync(self->data + offset, size, flags)) {
         PyErr_SetFromErrno(PyExc_OSError);
         return NULL;
     }
@@ -1203,7 +1205,7 @@ static struct PyMethodDef mmap_object_methods[] = {
     {"close",           mmap_close_method,        METH_NOARGS},
     {"find",            mmap_find_method,         METH_VARARGS},
     {"rfind",           mmap_rfind_method,        METH_VARARGS},
-    {"flush",           mmap_flush_method,        METH_VARARGS},
+    {"flush",           _PyCFunction_CAST(mmap_flush_method), METH_VARARGS | METH_KEYWORDS},
 #ifdef HAVE_MADVISE
     {"madvise",         mmap_madvise_method,      METH_VARARGS},
 #endif
@@ -2047,6 +2049,16 @@ mmap_exec(PyObject *module)
     ADD_INT_MACRO(module, ACCESS_WRITE);
     ADD_INT_MACRO(module, ACCESS_COPY);
 
+#ifdef MS_INVALIDATE
+    ADD_INT_MACRO(module, MS_INVALIDATE);
+#endif
+#ifdef MS_ASYNC
+    ADD_INT_MACRO(module, MS_ASYNC);
+#endif
+#ifdef MS_SYNC
+    ADD_INT_MACRO(module, MS_SYNC);
+#endif
+
 #ifdef HAVE_MADVISE
     // Conventional advice values
 #ifdef MADV_NORMAL