Steffen Daode Nurpmeso <sdao...@googlemail.com> added the comment:
I don't agree with you and i don't believe it is implemented like
that. But it seems i am the only one on this issue who sees it
like that. Thus i apply 11877.6.diff.
> Declaring variables as "auto" is not necessary in C code and not
> used anywhere else in Python's source code
Changed.
> Steffen, you changed the default to doing a "full sync" in your
> last patch
Changed all through.
> The reason being that Apple and NetBSD folks should know what
> they're doing [.]
> People requiring write durability will probably manage to find
> this full_sync parameter.
This sounds logical. I've changed the doc in os.rst so that it
includes a note on *which* operating systems actually do something
dependend on that argument.
I should have done that from the very beginning.
> Finally, depending on the workload, it could have a significant
> performance impact.
:-)
----------
Added file: http://bugs.python.org/file21953/11877.6.diff
_______________________________________
Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue11877>
_______________________________________
diff --git a/Doc/library/os.rst b/Doc/library/os.rst
--- a/Doc/library/os.rst
+++ b/Doc/library/os.rst
@@ -798,7 +798,7 @@
Availability: Unix.
-.. function:: fsync(fd)
+.. function:: fsync(fd, full_fsync=False)
Force write of file with filedescriptor *fd* to disk. On Unix, this calls
the
native :c:func:`fsync` function; on Windows, the MS :c:func:`_commit`
function.
@@ -807,6 +807,13 @@
``f.flush()``, and then do ``os.fsync(f.fileno())``, to ensure that all
internal
buffers associated with *f* are written to disk.
+ The POSIX standart only requires that :c:func:`fsync` must transfer the
+ buffered data to the storage device, not that the data is actually
+ written by the device itself. On operating systems where it is
+ necessary and possible the optional *full_fsync* argument can be used to
+ initiate additional steps to synchronize the physical backing store.
+ At the time of this writing this affects Apple Mac OS X and NetBSD.
+
Availability: Unix, and Windows.
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -2121,13 +2121,46 @@
#ifdef HAVE_FSYNC
PyDoc_STRVAR(posix_fsync__doc__,
-"fsync(fildes)\n\n\
-force write of file with filedescriptor to disk.");
-
-static PyObject *
-posix_fsync(PyObject *self, PyObject *fdobj)
-{
- return posix_fildes(fdobj, fsync);
+"fsync(fildes, full_fsync=False)\n\n"
+"force write of file buffers with fildes to disk;\n"
+"full_fsync forces flush of disk caches in case fsync() alone is not enough.");
+
+static PyObject *
+posix_fsync(PyObject *self, PyObject *args, PyObject *kwargs)
+{
+ PyObject *fdobj;
+ int full_fsync = 0;
+ static char *keywords[] = {"fd", "full_fsync", NULL };
+
+ if (!PyArg_ParseTupleAndKeywords(args, kwargs, "O|i", keywords,
+ &fdobj, &full_fsync))
+ return NULL;
+
+ /* See issue 11877 discussion */
+# if ((defined __APPLE__ && defined F_FULLFSYNC) || \
+ (defined __NetBSD__ && defined FDISKSYNC))
+ if (full_fsync != 0) {
+ int res, fd = PyObject_AsFileDescriptor(fdobj);
+ if (fd < 0)
+ return NULL;
+ if (!_PyVerify_fd(fd))
+ return posix_error();
+
+ Py_BEGIN_ALLOW_THREADS
+# if defined __APPLE__
+ res = fcntl(fd, F_FULLFSYNC);
+# elif defined __NetBSD__
+ res = fsync_range(fd, FFILESYNC|FDISKSYNC, 0, 0);
+# endif
+ Py_END_ALLOW_THREADS
+
+ if (res < 0)
+ return posix_error();
+ Py_INCREF(Py_None);
+ return Py_None;
+ } else
+# endif
+ return posix_fildes(fdobj, fsync);
}
#endif /* HAVE_FSYNC */
@@ -9472,7 +9505,8 @@
{"fchdir", posix_fchdir, METH_O, posix_fchdir__doc__},
#endif
#ifdef HAVE_FSYNC
- {"fsync", posix_fsync, METH_O, posix_fsync__doc__},
+ {"fsync", (PyCFunction)posix_fsync, METH_VARARGS|METH_KEYWORDS,
+ posix_fsync__doc__},
#endif
#ifdef HAVE_SYNC
{"sync", posix_sync, METH_NOARGS, posix_sync__doc__},
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