From ea21128d44dc31bc1cd2f9c285dbcf8e3ad1fe18 Mon Sep 17 00:00:00 2001
From: Pablo Galindo <pablogsal@gmail.com>
Date: Fri, 19 Jan 2018 01:53:41 +0000
Subject: [PATCH 01/14] Expose preadv2 in os module

---
 Lib/test/test_posix.py         | 13 +++++++
 Modules/clinic/posixmodule.c.h | 50 +++++++++++++++++++++++++-
 Modules/posixmodule.c          | 66 ++++++++++++++++++++++++++++++++++
 3 files changed, 128 insertions(+), 1 deletion(-)

diff --git a/Lib/test/test_posix.py b/Lib/test/test_posix.py
index 44b8d6a7ad0796..b3c07ff863d32b 100644
--- a/Lib/test/test_posix.py
+++ b/Lib/test/test_posix.py
@@ -272,6 +272,19 @@ def test_pread(self):
         finally:
             os.close(fd)
 
+    @unittest.skipUnless(hasattr(posix, 'pread'), "test needs posix.pread()")
+    def test_preadv2(self):
+        fd = os.open(support.TESTFN, os.O_RDWR | os.O_CREAT)
+        try:
+            os.write(fd, b'test1tt2t3')
+            os.lseek(fd, 0, os.SEEK_SET)
+            buf = [bytearray(i) for i in [5, 3, 2]]
+            self.assertEqual(posix.preadv2(fd, buf, 0, os.RWF_SYNC), 10)
+            self.assertEqual([b'test1', b'tt2', b't3'], [bytes(i) for i in buf])
+        finally:
+            os.close(fd)
+
+
     @unittest.skipUnless(hasattr(posix, 'pwrite'), "test needs posix.pwrite()")
     def test_pwrite(self):
         fd = os.open(support.TESTFN, os.O_RDWR | os.O_CREAT)
diff --git a/Modules/clinic/posixmodule.c.h b/Modules/clinic/posixmodule.c.h
index 6f4c028e7efef5..dd3b9b7faa6835 100644
--- a/Modules/clinic/posixmodule.c.h
+++ b/Modules/clinic/posixmodule.c.h
@@ -3705,6 +3705,50 @@ os_pread(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
 
 #endif /* defined(HAVE_PREAD) */
 
+#if defined(HAVE_PREAD)
+
+PyDoc_STRVAR(os_preadv2__doc__,
+"preadv2($module, fd, buffers, offset, flags, /)\n"
+"--\n"
+"\n"
+"Read a number of bytes from a file descriptor starting at a particular offset.\n"
+"\n"
+"Read length bytes from file descriptor fd, starting at offset bytes from\n"
+"the beginning of the file.  The file offset remains unchanged.");
+
+#define OS_PREADV2_METHODDEF    \
+    {"preadv2", (PyCFunction)os_preadv2, METH_FASTCALL, os_preadv2__doc__},
+
+static Py_ssize_t
+os_preadv2_impl(PyObject *module, int fd, PyObject *buffers, Py_off_t offset,
+                int flags);
+
+static PyObject *
+os_preadv2(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
+{
+    PyObject *return_value = NULL;
+    int fd;
+    PyObject *buffers;
+    Py_off_t offset;
+    int flags;
+    Py_ssize_t _return_value;
+
+    if (!_PyArg_ParseStack(args, nargs, "iOO&i:preadv2",
+        &fd, &buffers, Py_off_t_converter, &offset, &flags)) {
+        goto exit;
+    }
+    _return_value = os_preadv2_impl(module, fd, buffers, offset, flags);
+    if ((_return_value == -1) && PyErr_Occurred()) {
+        goto exit;
+    }
+    return_value = PyLong_FromSsize_t(_return_value);
+
+exit:
+    return return_value;
+}
+
+#endif /* defined(HAVE_PREAD) */
+
 PyDoc_STRVAR(os_write__doc__,
 "write($module, fd, data, /)\n"
 "--\n"
@@ -6239,6 +6283,10 @@ os_getrandom(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObject
     #define OS_PREAD_METHODDEF
 #endif /* !defined(OS_PREAD_METHODDEF) */
 
+#ifndef OS_PREADV2_METHODDEF
+    #define OS_PREADV2_METHODDEF
+#endif /* !defined(OS_PREADV2_METHODDEF) */
+
 #ifndef OS_PIPE_METHODDEF
     #define OS_PIPE_METHODDEF
 #endif /* !defined(OS_PIPE_METHODDEF) */
@@ -6410,4 +6458,4 @@ os_getrandom(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObject
 #ifndef OS_GETRANDOM_METHODDEF
     #define OS_GETRANDOM_METHODDEF
 #endif /* !defined(OS_GETRANDOM_METHODDEF) */
-/*[clinic end generated code: output=6345053cd5992caf input=a9049054013a1b77]*/
+/*[clinic end generated code: output=2b1fdec599a15ea9 input=a9049054013a1b77]*/
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index b0e48dabbd55cf..264e1362183f75 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -8163,6 +8163,64 @@ os_pread_impl(PyObject *module, int fd, int length, Py_off_t offset)
 }
 #endif /* HAVE_PREAD */
 
+#ifdef HAVE_PREAD
+/*[clinic input]
+os.preadv2 -> Py_ssize_t
+
+    fd: int
+    buffers: object
+    offset: Py_off_t
+    flags: int
+    /
+
+Read a number of bytes from a file descriptor starting at a particular offset.
+
+Read length bytes from file descriptor fd, starting at offset bytes from
+the beginning of the file.  The file offset remains unchanged.
+[clinic start generated code]*/
+
+static Py_ssize_t
+os_preadv2_impl(PyObject *module, int fd, PyObject *buffers, Py_off_t offset,
+                int flags)
+/*[clinic end generated code: output=fd040c20cf504631 input=f4a633d90005eb65]*/
+{
+    Py_ssize_t cnt, n;
+    int async_err = 0;
+    struct iovec *iov;
+    Py_buffer *buf;
+
+    if (!PySequence_Check(buffers)) {
+        PyErr_SetString(PyExc_TypeError,
+            "preadv2() arg 2 must be a sequence");
+        return -1;
+    }
+
+    cnt = PySequence_Size(buffers);
+    if (cnt < 0)
+        return -1;
+
+    if (iov_setup(&iov, &buf, buffers, cnt, PyBUF_WRITABLE) < 0)
+        return -1;
+
+    do {
+        Py_BEGIN_ALLOW_THREADS
+        n = preadv2(fd, iov, cnt, offset, flags);
+        Py_END_ALLOW_THREADS
+    } while (n < 0 && errno == EINTR && !(async_err = PyErr_CheckSignals()));
+
+    iov_cleanup(iov, buf, cnt);
+    if (n < 0) {
+        if (!async_err)
+            posix_error();
+        return -1;
+    }
+
+    return n;
+}
+
+
+#endif /* HAVE PREADV2 */
+
 
 /*[clinic input]
 os.write -> Py_ssize_t
@@ -12506,6 +12564,7 @@ static PyMethodDef posix_methods[] = {
     OS_READ_METHODDEF
     OS_READV_METHODDEF
     OS_PREAD_METHODDEF
+    OS_PREADV2_METHODDEF
     OS_WRITE_METHODDEF
     OS_WRITEV_METHODDEF
     OS_PWRITE_METHODDEF
@@ -12953,6 +13012,13 @@ all_ins(PyObject *m)
     if (PyModule_AddIntMacro(m, F_TEST)) return -1;
 #endif
 
+#ifdef HAVE_READV
+    if (PyModule_AddIntConstant(m, "RWF_DSYNC", RWF_DSYNC)) return -1;
+    if (PyModule_AddIntConstant(m, "RWF_HIPRI", RWF_HIPRI)) return -1;
+    if (PyModule_AddIntConstant(m, "RWF_SYNC", RWF_SYNC)) return -1;
+    if (PyModule_AddIntConstant(m, "RWF_NOWAIT", RWF_NOWAIT)) return -1;
+#endif
+
 #ifdef HAVE_SPAWNV
     if (PyModule_AddIntConstant(m, "P_WAIT", _P_WAIT)) return -1;
     if (PyModule_AddIntConstant(m, "P_NOWAIT", _P_NOWAIT)) return -1;

From 4570976db32e695f94ab0ccd07d187eb870b7084 Mon Sep 17 00:00:00 2001
From: Pablo Galindo <pablogsal@gmail.com>
Date: Fri, 19 Jan 2018 01:54:32 +0000
Subject: [PATCH 02/14] Add News entry

---
 .../Core and Builtins/2018-01-19-01-54-22.bpo-31368.kzKqUR.rst   | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 Misc/NEWS.d/next/Core and Builtins/2018-01-19-01-54-22.bpo-31368.kzKqUR.rst

diff --git a/Misc/NEWS.d/next/Core and Builtins/2018-01-19-01-54-22.bpo-31368.kzKqUR.rst b/Misc/NEWS.d/next/Core and Builtins/2018-01-19-01-54-22.bpo-31368.kzKqUR.rst
new file mode 100644
index 00000000000000..a614ab64628423
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2018-01-19-01-54-22.bpo-31368.kzKqUR.rst	
@@ -0,0 +1 @@
+Expose preadv2 system call in the os module. Patch by Pablo Galindo

From 21a3004ea437ae8f036b866460a43d20e475e460 Mon Sep 17 00:00:00 2001
From: Pablo Galindo <pablogsal@gmail.com>
Date: Fri, 19 Jan 2018 02:00:11 +0000
Subject: [PATCH 03/14] Add correct guards for the presence of preadv2

---
 Lib/test/test_posix.py         | 2 +-
 Modules/clinic/posixmodule.c.h | 6 +++---
 Modules/posixmodule.c          | 4 ++--
 3 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/Lib/test/test_posix.py b/Lib/test/test_posix.py
index b3c07ff863d32b..947de6e3efd1db 100644
--- a/Lib/test/test_posix.py
+++ b/Lib/test/test_posix.py
@@ -272,7 +272,7 @@ def test_pread(self):
         finally:
             os.close(fd)
 
-    @unittest.skipUnless(hasattr(posix, 'pread'), "test needs posix.pread()")
+    @unittest.skipUnless(hasattr(posix, 'preadv2'), "test needs posix.preadv2()")
     def test_preadv2(self):
         fd = os.open(support.TESTFN, os.O_RDWR | os.O_CREAT)
         try:
diff --git a/Modules/clinic/posixmodule.c.h b/Modules/clinic/posixmodule.c.h
index dd3b9b7faa6835..c609dba89beaa8 100644
--- a/Modules/clinic/posixmodule.c.h
+++ b/Modules/clinic/posixmodule.c.h
@@ -3705,7 +3705,7 @@ os_pread(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
 
 #endif /* defined(HAVE_PREAD) */
 
-#if defined(HAVE_PREAD)
+#if defined(HAVE_PREADV2)
 
 PyDoc_STRVAR(os_preadv2__doc__,
 "preadv2($module, fd, buffers, offset, flags, /)\n"
@@ -3747,7 +3747,7 @@ os_preadv2(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
     return return_value;
 }
 
-#endif /* defined(HAVE_PREAD) */
+#endif /* defined(HAVE_PREADV2) */
 
 PyDoc_STRVAR(os_write__doc__,
 "write($module, fd, data, /)\n"
@@ -6458,4 +6458,4 @@ os_getrandom(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObject
 #ifndef OS_GETRANDOM_METHODDEF
     #define OS_GETRANDOM_METHODDEF
 #endif /* !defined(OS_GETRANDOM_METHODDEF) */
-/*[clinic end generated code: output=2b1fdec599a15ea9 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=efbe9448c1bba1a2 input=a9049054013a1b77]*/
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index 264e1362183f75..ea0841cdacb16e 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -8163,7 +8163,7 @@ os_pread_impl(PyObject *module, int fd, int length, Py_off_t offset)
 }
 #endif /* HAVE_PREAD */
 
-#ifdef HAVE_PREAD
+#ifdef HAVE_PREADV2
 /*[clinic input]
 os.preadv2 -> Py_ssize_t
 
@@ -13012,7 +13012,7 @@ all_ins(PyObject *m)
     if (PyModule_AddIntMacro(m, F_TEST)) return -1;
 #endif
 
-#ifdef HAVE_READV
+#ifdef HAVE_PREADV2
     if (PyModule_AddIntConstant(m, "RWF_DSYNC", RWF_DSYNC)) return -1;
     if (PyModule_AddIntConstant(m, "RWF_HIPRI", RWF_HIPRI)) return -1;
     if (PyModule_AddIntConstant(m, "RWF_SYNC", RWF_SYNC)) return -1;

From 8a2a2a31db2af445f0cfdb987aad42a03f3d1ed1 Mon Sep 17 00:00:00 2001
From: Pablo Galindo <pablogsal@gmail.com>
Date: Fri, 19 Jan 2018 21:07:35 +0000
Subject: [PATCH 04/14] Implement check for individual constants

---
 Modules/posixmodule.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index ea0841cdacb16e..3033accac4bdb8 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -13012,10 +13012,16 @@ all_ins(PyObject *m)
     if (PyModule_AddIntMacro(m, F_TEST)) return -1;
 #endif
 
-#ifdef HAVE_PREADV2
+#ifdef RWF_DSYNC
     if (PyModule_AddIntConstant(m, "RWF_DSYNC", RWF_DSYNC)) return -1;
+#endif
+#ifdef RWF_HIPRI
     if (PyModule_AddIntConstant(m, "RWF_HIPRI", RWF_HIPRI)) return -1;
+#endif
+#ifdef RWF_SYNC
     if (PyModule_AddIntConstant(m, "RWF_SYNC", RWF_SYNC)) return -1;
+#endif
+#ifdef RWF_NOWAIT
     if (PyModule_AddIntConstant(m, "RWF_NOWAIT", RWF_NOWAIT)) return -1;
 #endif
 

From c0c53dc91daabaa8d722607dd49c1b713f40ce64 Mon Sep 17 00:00:00 2001
From: Pablo Galindo <pablogsal@gmail.com>
Date: Fri, 19 Jan 2018 22:06:14 +0000
Subject: [PATCH 05/14] Implemented preadv and join implementation to preadv2

---
 Lib/test/test_posix.py         | 17 ++++++--
 Modules/clinic/posixmodule.c.h | 32 +++++++-------
 Modules/posixmodule.c          | 31 ++++++++-----
 aclocal.m4                     | 80 +++-------------------------------
 configure                      |  2 +-
 configure.ac                   |  2 +-
 pyconfig.h.in                  |  6 +++
 7 files changed, 64 insertions(+), 106 deletions(-)

diff --git a/Lib/test/test_posix.py b/Lib/test/test_posix.py
index 947de6e3efd1db..0e86cda7e991f2 100644
--- a/Lib/test/test_posix.py
+++ b/Lib/test/test_posix.py
@@ -272,18 +272,29 @@ def test_pread(self):
         finally:
             os.close(fd)
 
-    @unittest.skipUnless(hasattr(posix, 'preadv2'), "test needs posix.preadv2()")
-    def test_preadv2(self):
+    @unittest.skipUnless(hasattr(posix, 'preadv'), "test needs posix.preadv()")
+    def test_preadv(self):
         fd = os.open(support.TESTFN, os.O_RDWR | os.O_CREAT)
         try:
             os.write(fd, b'test1tt2t3')
             os.lseek(fd, 0, os.SEEK_SET)
             buf = [bytearray(i) for i in [5, 3, 2]]
-            self.assertEqual(posix.preadv2(fd, buf, 0, os.RWF_SYNC), 10)
+            self.assertEqual(posix.preadv(fd, buf, 0), 10)
             self.assertEqual([b'test1', b'tt2', b't3'], [bytes(i) for i in buf])
         finally:
             os.close(fd)
 
+    @unittest.skipUnless(hasattr(posix, 'RWF_SYNC'), "test needs posix.preadv2()")
+    def test_preadv2(self):
+        fd = os.open(support.TESTFN, os.O_RDWR | os.O_CREAT)
+        try:
+            os.write(fd, b'test1tt2t3')
+            os.lseek(fd, 0, os.SEEK_SET)
+            buf = [bytearray(i) for i in [5, 3, 2]]
+            self.assertEqual(posix.preadv(fd, buf, 0, os.RWF_SYNC), 10)
+            self.assertEqual([b'test1', b'tt2', b't3'], [bytes(i) for i in buf])
+        finally:
+            os.close(fd)
 
     @unittest.skipUnless(hasattr(posix, 'pwrite'), "test needs posix.pwrite()")
     def test_pwrite(self):
diff --git a/Modules/clinic/posixmodule.c.h b/Modules/clinic/posixmodule.c.h
index c609dba89beaa8..c2b7f327346b9c 100644
--- a/Modules/clinic/posixmodule.c.h
+++ b/Modules/clinic/posixmodule.c.h
@@ -3705,10 +3705,10 @@ os_pread(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
 
 #endif /* defined(HAVE_PREAD) */
 
-#if defined(HAVE_PREADV2)
+#if (defined(HAVE_PREADV) || defined (HAVE_PREADV2))
 
-PyDoc_STRVAR(os_preadv2__doc__,
-"preadv2($module, fd, buffers, offset, flags, /)\n"
+PyDoc_STRVAR(os_preadv__doc__,
+"preadv($module, fd, buffers, offset, flags=0, /)\n"
 "--\n"
 "\n"
 "Read a number of bytes from a file descriptor starting at a particular offset.\n"
@@ -3716,28 +3716,28 @@ PyDoc_STRVAR(os_preadv2__doc__,
 "Read length bytes from file descriptor fd, starting at offset bytes from\n"
 "the beginning of the file.  The file offset remains unchanged.");
 
-#define OS_PREADV2_METHODDEF    \
-    {"preadv2", (PyCFunction)os_preadv2, METH_FASTCALL, os_preadv2__doc__},
+#define OS_PREADV_METHODDEF    \
+    {"preadv", (PyCFunction)os_preadv, METH_FASTCALL, os_preadv__doc__},
 
 static Py_ssize_t
-os_preadv2_impl(PyObject *module, int fd, PyObject *buffers, Py_off_t offset,
-                int flags);
+os_preadv_impl(PyObject *module, int fd, PyObject *buffers, Py_off_t offset,
+               int flags);
 
 static PyObject *
-os_preadv2(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
+os_preadv(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
 {
     PyObject *return_value = NULL;
     int fd;
     PyObject *buffers;
     Py_off_t offset;
-    int flags;
+    int flags = 0;
     Py_ssize_t _return_value;
 
-    if (!_PyArg_ParseStack(args, nargs, "iOO&i:preadv2",
+    if (!_PyArg_ParseStack(args, nargs, "iOO&|i:preadv",
         &fd, &buffers, Py_off_t_converter, &offset, &flags)) {
         goto exit;
     }
-    _return_value = os_preadv2_impl(module, fd, buffers, offset, flags);
+    _return_value = os_preadv_impl(module, fd, buffers, offset, flags);
     if ((_return_value == -1) && PyErr_Occurred()) {
         goto exit;
     }
@@ -3747,7 +3747,7 @@ os_preadv2(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
     return return_value;
 }
 
-#endif /* defined(HAVE_PREADV2) */
+#endif /* (defined(HAVE_PREADV) || defined (HAVE_PREADV2)) */
 
 PyDoc_STRVAR(os_write__doc__,
 "write($module, fd, data, /)\n"
@@ -6283,9 +6283,9 @@ os_getrandom(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObject
     #define OS_PREAD_METHODDEF
 #endif /* !defined(OS_PREAD_METHODDEF) */
 
-#ifndef OS_PREADV2_METHODDEF
-    #define OS_PREADV2_METHODDEF
-#endif /* !defined(OS_PREADV2_METHODDEF) */
+#ifndef OS_PREADV_METHODDEF
+    #define OS_PREADV_METHODDEF
+#endif /* !defined(OS_PREADV_METHODDEF) */
 
 #ifndef OS_PIPE_METHODDEF
     #define OS_PIPE_METHODDEF
@@ -6458,4 +6458,4 @@ os_getrandom(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObject
 #ifndef OS_GETRANDOM_METHODDEF
     #define OS_GETRANDOM_METHODDEF
 #endif /* !defined(OS_GETRANDOM_METHODDEF) */
-/*[clinic end generated code: output=efbe9448c1bba1a2 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=52cbdec1822e34f9 input=a9049054013a1b77]*/
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index 3033accac4bdb8..7a514275c7fc70 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -8163,14 +8163,14 @@ os_pread_impl(PyObject *module, int fd, int length, Py_off_t offset)
 }
 #endif /* HAVE_PREAD */
 
-#ifdef HAVE_PREADV2
+#if defined(HAVE_PREADV) || defined (HAVE_PREADV2)
 /*[clinic input]
-os.preadv2 -> Py_ssize_t
+os.preadv -> Py_ssize_t
 
     fd: int
     buffers: object
     offset: Py_off_t
-    flags: int
+    flags: int = 0
     /
 
 Read a number of bytes from a file descriptor starting at a particular offset.
@@ -8180,9 +8180,9 @@ the beginning of the file.  The file offset remains unchanged.
 [clinic start generated code]*/
 
 static Py_ssize_t
-os_preadv2_impl(PyObject *module, int fd, PyObject *buffers, Py_off_t offset,
-                int flags)
-/*[clinic end generated code: output=fd040c20cf504631 input=f4a633d90005eb65]*/
+os_preadv_impl(PyObject *module, int fd, PyObject *buffers, Py_off_t offset,
+               int flags)
+/*[clinic end generated code: output=26fc9c6e58e7ada5 input=5b07b7e2d1825627]*/
 {
     Py_ssize_t cnt, n;
     int async_err = 0;
@@ -8201,12 +8201,23 @@ os_preadv2_impl(PyObject *module, int fd, PyObject *buffers, Py_off_t offset,
 
     if (iov_setup(&iov, &buf, buffers, cnt, PyBUF_WRITABLE) < 0)
         return -1;
-
+    #ifdef HAVE_PREADV2
     do {
         Py_BEGIN_ALLOW_THREADS
         n = preadv2(fd, iov, cnt, offset, flags);
         Py_END_ALLOW_THREADS
     } while (n < 0 && errno == EINTR && !(async_err = PyErr_CheckSignals()));
+    #else
+    if(flags != 0){
+        PyErr_SetString(PyExc_OSError, "preadv2() not available in this system");
+        return -1;
+    }
+    do {
+        Py_BEGIN_ALLOW_THREADS
+        n = preadv(fd, iov, cnt, offset);
+        Py_END_ALLOW_THREADS
+    } while (n < 0 && errno == EINTR && !(async_err = PyErr_CheckSignals()));
+    #endif
 
     iov_cleanup(iov, buf, cnt);
     if (n < 0) {
@@ -8217,9 +8228,7 @@ os_preadv2_impl(PyObject *module, int fd, PyObject *buffers, Py_off_t offset,
 
     return n;
 }
-
-
-#endif /* HAVE PREADV2 */
+#endif /* HAVE_PREADV2 */
 
 
 /*[clinic input]
@@ -12564,7 +12573,7 @@ static PyMethodDef posix_methods[] = {
     OS_READ_METHODDEF
     OS_READV_METHODDEF
     OS_PREAD_METHODDEF
-    OS_PREADV2_METHODDEF
+    OS_PREADV_METHODDEF
     OS_WRITE_METHODDEF
     OS_WRITEV_METHODDEF
     OS_PWRITE_METHODDEF
diff --git a/aclocal.m4 b/aclocal.m4
index 09694962914b79..8ed232fb515f90 100644
--- a/aclocal.m4
+++ b/aclocal.m4
@@ -13,7 +13,7 @@
 
 m4_ifndef([AC_CONFIG_MACRO_DIRS], [m4_defun([_AM_CONFIG_MACRO_DIRS], [])m4_defun([AC_CONFIG_MACRO_DIRS], [_AM_CONFIG_MACRO_DIRS($@)])])
 # pkg.m4 - Macros to locate and utilise pkg-config.   -*- Autoconf -*-
-# serial 11 (pkg-config-0.29.1)
+# serial 12 (pkg-config-0.29.2)
 
 dnl Copyright © 2004 Scott James Remnant <scott@netsplit.com>.
 dnl Copyright © 2012-2015 Dan Nicholson <dbn.lists@gmail.com>
@@ -55,7 +55,7 @@ dnl
 dnl See the "Since" comment for each macro you use to see what version
 dnl of the macros you require.
 m4_defun([PKG_PREREQ],
-[m4_define([PKG_MACROS_VERSION], [0.29.1])
+[m4_define([PKG_MACROS_VERSION], [0.29.2])
 m4_if(m4_version_compare(PKG_MACROS_VERSION, [$1]), -1,
     [m4_fatal([pkg.m4 version $1 or higher is required but ]PKG_MACROS_VERSION[ found])])
 ])dnl PKG_PREREQ
@@ -156,7 +156,7 @@ AC_ARG_VAR([$1][_CFLAGS], [C compiler flags for $1, overriding pkg-config])dnl
 AC_ARG_VAR([$1][_LIBS], [linker flags for $1, overriding pkg-config])dnl
 
 pkg_failed=no
-AC_MSG_CHECKING([for $1])
+AC_MSG_CHECKING([for $2])
 
 _PKG_CONFIG([$1][_CFLAGS], [cflags], [$2])
 _PKG_CONFIG([$1][_LIBS], [libs], [$2])
@@ -166,11 +166,11 @@ and $1[]_LIBS to avoid the need to call pkg-config.
 See the pkg-config man page for more details.])
 
 if test $pkg_failed = yes; then
-   	AC_MSG_RESULT([no])
+        AC_MSG_RESULT([no])
         _PKG_SHORT_ERRORS_SUPPORTED
         if test $_pkg_short_errors_supported = yes; then
 	        $1[]_PKG_ERRORS=`$PKG_CONFIG --short-errors --print-errors --cflags --libs "$2" 2>&1`
-        else 
+        else
 	        $1[]_PKG_ERRORS=`$PKG_CONFIG --print-errors --cflags --libs "$2" 2>&1`
         fi
 	# Put the nasty error message in config.log where it belongs
@@ -187,7 +187,7 @@ installed software in a non-standard prefix.
 _PKG_TEXT])[]dnl
         ])
 elif test $pkg_failed = untried; then
-     	AC_MSG_RESULT([no])
+        AC_MSG_RESULT([no])
 	m4_default([$4], [AC_MSG_FAILURE(
 [The pkg-config script could not be found or is too old.  Make sure it
 is in your PATH or set the PKG_CONFIG environment variable to the full
@@ -288,72 +288,4 @@ AS_VAR_COPY([$1], [pkg_cv_][$1])
 AS_VAR_IF([$1], [""], [$5], [$4])dnl
 ])dnl PKG_CHECK_VAR
 
-dnl PKG_WITH_MODULES(VARIABLE-PREFIX, MODULES,
-dnl   [ACTION-IF-FOUND],[ACTION-IF-NOT-FOUND],
-dnl   [DESCRIPTION], [DEFAULT])
-dnl ------------------------------------------
-dnl
-dnl Prepare a "--with-" configure option using the lowercase
-dnl [VARIABLE-PREFIX] name, merging the behaviour of AC_ARG_WITH and
-dnl PKG_CHECK_MODULES in a single macro.
-AC_DEFUN([PKG_WITH_MODULES],
-[
-m4_pushdef([with_arg], m4_tolower([$1]))
-
-m4_pushdef([description],
-           [m4_default([$5], [build with ]with_arg[ support])])
-
-m4_pushdef([def_arg], [m4_default([$6], [auto])])
-m4_pushdef([def_action_if_found], [AS_TR_SH([with_]with_arg)=yes])
-m4_pushdef([def_action_if_not_found], [AS_TR_SH([with_]with_arg)=no])
-
-m4_case(def_arg,
-            [yes],[m4_pushdef([with_without], [--without-]with_arg)],
-            [m4_pushdef([with_without],[--with-]with_arg)])
-
-AC_ARG_WITH(with_arg,
-     AS_HELP_STRING(with_without, description[ @<:@default=]def_arg[@:>@]),,
-    [AS_TR_SH([with_]with_arg)=def_arg])
-
-AS_CASE([$AS_TR_SH([with_]with_arg)],
-            [yes],[PKG_CHECK_MODULES([$1],[$2],$3,$4)],
-            [auto],[PKG_CHECK_MODULES([$1],[$2],
-                                        [m4_n([def_action_if_found]) $3],
-                                        [m4_n([def_action_if_not_found]) $4])])
-
-m4_popdef([with_arg])
-m4_popdef([description])
-m4_popdef([def_arg])
-
-])dnl PKG_WITH_MODULES
-
-dnl PKG_HAVE_WITH_MODULES(VARIABLE-PREFIX, MODULES,
-dnl   [DESCRIPTION], [DEFAULT])
-dnl -----------------------------------------------
-dnl
-dnl Convenience macro to trigger AM_CONDITIONAL after PKG_WITH_MODULES
-dnl check._[VARIABLE-PREFIX] is exported as make variable.
-AC_DEFUN([PKG_HAVE_WITH_MODULES],
-[
-PKG_WITH_MODULES([$1],[$2],,,[$3],[$4])
-
-AM_CONDITIONAL([HAVE_][$1],
-               [test "$AS_TR_SH([with_]m4_tolower([$1]))" = "yes"])
-])dnl PKG_HAVE_WITH_MODULES
-
-dnl PKG_HAVE_DEFINE_WITH_MODULES(VARIABLE-PREFIX, MODULES,
-dnl   [DESCRIPTION], [DEFAULT])
-dnl ------------------------------------------------------
-dnl
-dnl Convenience macro to run AM_CONDITIONAL and AC_DEFINE after
-dnl PKG_WITH_MODULES check. HAVE_[VARIABLE-PREFIX] is exported as make
-dnl and preprocessor variable.
-AC_DEFUN([PKG_HAVE_DEFINE_WITH_MODULES],
-[
-PKG_HAVE_WITH_MODULES([$1],[$2],[$3],[$4])
-
-AS_IF([test "$AS_TR_SH([with_]m4_tolower([$1]))" = "yes"],
-        [AC_DEFINE([HAVE_][$1], 1, [Enable ]m4_tolower([$1])[ support])])
-])dnl PKG_HAVE_DEFINE_WITH_MODULES
-
 m4_include([m4/ax_check_openssl.m4])
diff --git a/configure b/configure
index 420c07639b5cc4..ca1557ef118beb 100755
--- a/configure
+++ b/configure
@@ -11201,7 +11201,7 @@ for ac_func in alarm accept4 setitimer getitimer bind_textdomain_codeset chown \
  initgroups kill killpg lchmod lchown lockf linkat lstat lutimes mmap \
  memrchr mbrtowc mkdirat mkfifo \
  mkfifoat mknod mknodat mktime mremap nice openat pathconf pause pipe2 plock poll \
- posix_fallocate posix_fadvise pread \
+ posix_fallocate posix_fadvise pread preadv preadv2 \
  pthread_init pthread_kill putenv pwrite readlink readlinkat readv realpath renameat \
  sem_open sem_timedwait sem_getvalue sem_unlink sendfile setegid seteuid \
  setgid sethostname \
diff --git a/configure.ac b/configure.ac
index 39e2e8e769e973..df92ea8dd33c30 100644
--- a/configure.ac
+++ b/configure.ac
@@ -3435,7 +3435,7 @@ AC_CHECK_FUNCS(alarm accept4 setitimer getitimer bind_textdomain_codeset chown \
  initgroups kill killpg lchmod lchown lockf linkat lstat lutimes mmap \
  memrchr mbrtowc mkdirat mkfifo \
  mkfifoat mknod mknodat mktime mremap nice openat pathconf pause pipe2 plock poll \
- posix_fallocate posix_fadvise pread \
+ posix_fallocate posix_fadvise pread preadv preadv2 \
  pthread_init pthread_kill putenv pwrite readlink readlinkat readv realpath renameat \
  sem_open sem_timedwait sem_getvalue sem_unlink sendfile setegid seteuid \
  setgid sethostname \
diff --git a/pyconfig.h.in b/pyconfig.h.in
index dd7c62bad1bacb..d98d6e7cb2628a 100644
--- a/pyconfig.h.in
+++ b/pyconfig.h.in
@@ -707,6 +707,12 @@
 /* Define to 1 if you have the `pread' function. */
 #undef HAVE_PREAD
 
+/* Define to 1 if you have the `preadv' function. */
+#undef HAVE_PREADV
+
+/* Define to 1 if you have the `preadv2' function. */
+#undef HAVE_PREADV2
+
 /* Define if you have the 'prlimit' functions. */
 #undef HAVE_PRLIMIT
 

From 4ddbca92005c9a3876cc54685083a4363fb2b020 Mon Sep 17 00:00:00 2001
From: Pablo Galindo <pablogsal@gmail.com>
Date: Sat, 20 Jan 2018 16:32:34 +0000
Subject: [PATCH 06/14] Clean iov on error

---
 Modules/posixmodule.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index 7a514275c7fc70..d146a00c98b466 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -8201,15 +8201,16 @@ os_preadv_impl(PyObject *module, int fd, PyObject *buffers, Py_off_t offset,
 
     if (iov_setup(&iov, &buf, buffers, cnt, PyBUF_WRITABLE) < 0)
         return -1;
-    #ifdef HAVE_PREADV2
+#ifdef HAVE_PREADV2
     do {
         Py_BEGIN_ALLOW_THREADS
         n = preadv2(fd, iov, cnt, offset, flags);
         Py_END_ALLOW_THREADS
     } while (n < 0 && errno == EINTR && !(async_err = PyErr_CheckSignals()));
-    #else
+#else
     if(flags != 0){
         PyErr_SetString(PyExc_OSError, "preadv2() not available in this system");
+        iov_cleanup(iov, buf, cnt);
         return -1;
     }
     do {
@@ -8217,7 +8218,7 @@ os_preadv_impl(PyObject *module, int fd, PyObject *buffers, Py_off_t offset,
         n = preadv(fd, iov, cnt, offset);
         Py_END_ALLOW_THREADS
     } while (n < 0 && errno == EINTR && !(async_err = PyErr_CheckSignals()));
-    #endif
+#endif
 
     iov_cleanup(iov, buf, cnt);
     if (n < 0) {
@@ -8228,7 +8229,7 @@ os_preadv_impl(PyObject *module, int fd, PyObject *buffers, Py_off_t offset,
 
     return n;
 }
-#endif /* HAVE_PREADV2 */
+#endif /* HAVE_PREADV */
 
 
 /*[clinic input]

From cac62acc1dd6d5f994ad420f8602ef3cbc52a7d6 Mon Sep 17 00:00:00 2001
From: Pablo Galindo <pablogsal@gmail.com>
Date: Mon, 22 Jan 2018 20:30:20 +0000
Subject: [PATCH 07/14] Add documentation in the os module

---
 Doc/library/os.rst | 26 ++++++++++++++++++++++++++
 1 file changed, 26 insertions(+)

diff --git a/Doc/library/os.rst b/Doc/library/os.rst
index ee08853087f71e..49221743223644 100644
--- a/Doc/library/os.rst
+++ b/Doc/library/os.rst
@@ -1195,6 +1195,32 @@ or `the MSDN <https://msdn.microsoft.com/en-us/library/z0kc8e3z.aspx>`_ on Windo
    .. versionadded:: 3.3
 
 
+.. function:: preadv(fd, buffers, offset, flags = None)
+
+   Combines the functionality of :func:`os.readv` and :func:`os.pread`. It
+   performs the same task as :func:`os.readv`, but adds a fourth argument,
+   offset, which specifies the file offset at which the input operation is
+   to be performed.
+
+   If the *flags* argument is provided it will invoke the *preadv2* system
+   call, which modifies the behavior on a per-call basis based on the value
+   of the *flags* argument. If this argument is ommited, the *preadv* system
+   call will be called instead.
+
+   The flags argument contains a bitwise OR of zero or more of the following
+   flags:
+
+.. data:: RWF_HIPRI
+          RWF_NOWAIT
+
+   The above constants are available on Linux Kernel 4.11 and 4.6 (or newer)
+   respectively.
+
+   Availability: Unix.
+
+   .. versionadded:: 3.7
+
+
 .. function:: tcgetpgrp(fd)
 
    Return the process group associated with the terminal given by *fd* (an open

From c7b7285c2d9473537553c4d8ceeae7e9e317c999 Mon Sep 17 00:00:00 2001
From: Pablo Galindo <pablogsal@gmail.com>
Date: Mon, 22 Jan 2018 22:00:37 +0000
Subject: [PATCH 08/14] Add information about the rest of the parameters

---
 Doc/library/os.rst | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/Doc/library/os.rst b/Doc/library/os.rst
index 49221743223644..9765f10a44a9d4 100644
--- a/Doc/library/os.rst
+++ b/Doc/library/os.rst
@@ -1195,12 +1195,16 @@ or `the MSDN <https://msdn.microsoft.com/en-us/library/z0kc8e3z.aspx>`_ on Windo
    .. versionadded:: 3.3
 
 
-.. function:: preadv(fd, buffers, offset, flags = None)
+.. function:: preadv(fd, buffers, offset, flags=0)
 
    Combines the functionality of :func:`os.readv` and :func:`os.pread`. It
-   performs the same task as :func:`os.readv`, but adds a fourth argument,
-   offset, which specifies the file offset at which the input operation is
-   to be performed.
+   reads from a file descriptor *fd* into a number of mutable :term:`bytes-like
+   objects <bytes-like object>` *buffers*. As :func:`os.readv`, it will transfer
+   data into each buffer until it is full and then move on to the next buffer in
+   the sequence to hold the rest of the data. Its fourth argument, *offset*,
+   specifies the file offset at which the input operation is to be performed.
+   :func:`~os.preadv` return the total number of bytes read (which may be less than
+   the total capacity of all the objects).
 
    If the *flags* argument is provided it will invoke the *preadv2* system
    call, which modifies the behavior on a per-call basis based on the value

From 58910d018cd56b814cc1fe2e0025838180c31b31 Mon Sep 17 00:00:00 2001
From: Pablo Galindo <pablogsal@gmail.com>
Date: Tue, 23 Jan 2018 00:08:10 +0000
Subject: [PATCH 09/14] Expose pwritev and pwritev2 in os module

---
 Doc/library/os.rst                            | 29 +++++++
 Lib/test/test_posix.py                        | 32 +++++++-
 .../2018-01-19-01-54-22.bpo-31368.kzKqUR.rst  |  3 +-
 Modules/clinic/posixmodule.c.h                | 51 +++++++++++-
 Modules/posixmodule.c                         | 81 +++++++++++++++++++
 configure                                     |  2 +-
 configure.ac                                  |  2 +-
 pyconfig.h.in                                 |  6 ++
 8 files changed, 200 insertions(+), 6 deletions(-)

diff --git a/Doc/library/os.rst b/Doc/library/os.rst
index 9765f10a44a9d4..739726e96717c8 100644
--- a/Doc/library/os.rst
+++ b/Doc/library/os.rst
@@ -1101,6 +1101,35 @@ or `the MSDN <https://msdn.microsoft.com/en-us/library/z0kc8e3z.aspx>`_ on Windo
    .. versionadded:: 3.3
 
 
+.. function:: pwritev(fd, buffers, offset, flags=0)
+
+   Combines the functionality of :func:`os.writev` and :func:`os.pwrite`. It
+   writes the contents of *buffers* to file descriptor *fd*. *buffers* must be
+   a sequence of :term:`bytes-like objects <bytes-like object>`. Buffers are
+   processed in array order. Entire contents of first buffer is written before
+   proceeding to second, and so on. The operating system may set a limit
+   (sysconf() value SC_IOV_MAX) on the number of buffers that can be used.
+   :func:`~os.pwritev` writes the contents of each object to the file descriptor
+   and returns the total number of bytes written.
+
+   If the *flags* argument is provided it will invoke the *pwritev2* system
+   call, which modifies the behavior on a per-call basis based on the value
+   of the *flags* argument. If this argument is ommited, the *pwritev* system
+   call will be called instead.
+
+   The flags argument contains a bitwise OR of zero or more of the following
+   flags:
+
+.. data:: RWF_DSYNC
+          RWF_SYNC
+
+   The above constants are available on Linux Kernel 4.7 (or newer).
+
+   Availability: Unix.
+
+   .. versionadded:: 3.7
+
+
 .. function:: read(fd, n)
 
    Read at most *n* bytes from file descriptor *fd*. Return a bytestring containing the
diff --git a/Lib/test/test_posix.py b/Lib/test/test_posix.py
index 0e86cda7e991f2..ddf576a58955b1 100644
--- a/Lib/test/test_posix.py
+++ b/Lib/test/test_posix.py
@@ -284,14 +284,14 @@ def test_preadv(self):
         finally:
             os.close(fd)
 
-    @unittest.skipUnless(hasattr(posix, 'RWF_SYNC'), "test needs posix.preadv2()")
+    @unittest.skipUnless(hasattr(posix, 'RWF_HIPRI'), "test needs posix.preadv2()")
     def test_preadv2(self):
         fd = os.open(support.TESTFN, os.O_RDWR | os.O_CREAT)
         try:
             os.write(fd, b'test1tt2t3')
             os.lseek(fd, 0, os.SEEK_SET)
             buf = [bytearray(i) for i in [5, 3, 2]]
-            self.assertEqual(posix.preadv(fd, buf, 0, os.RWF_SYNC), 10)
+            self.assertEqual(posix.preadv(fd, buf, 0, os.RWF_HIPRI), 10)
             self.assertEqual([b'test1', b'tt2', b't3'], [bytes(i) for i in buf])
         finally:
             os.close(fd)
@@ -307,6 +307,34 @@ def test_pwrite(self):
         finally:
             os.close(fd)
 
+    @unittest.skipUnless(hasattr(posix, 'pwritev'), "test needs posix.pwritev()")
+    def test_pwritev(self):
+        fd = os.open(support.TESTFN, os.O_RDWR | os.O_CREAT)
+        try:
+            n = os.pwritev(fd, [b'test1tt2t3'],2)
+            self.assertEqual(n, 10)
+
+            os.lseek(fd, 0, os.SEEK_SET)
+            self.assertEqual(b'\x00\x00test1tt2', posix.read(fd, 10))
+
+        finally:
+            os.close(fd)
+
+
+    @unittest.skipUnless(hasattr(posix, 'os.RWF_SYNC'), "test needs posix.pwritev2()")
+    def test_pwritev2(self):
+        fd = os.open(support.TESTFN, os.O_RDWR | os.O_CREAT)
+        try:
+            n = os.pwritev(fd, [b'test1tt2t3'],2, os.RWF_SYNC)
+            self.assertEqual(n, 10)
+
+            os.lseek(fd, 0, os.SEEK_SET)
+            self.assertEqual(b'\x00\x00test1tt2', posix.read(fd, 10))
+
+        finally:
+            os.close(fd)
+
+
     @unittest.skipUnless(hasattr(posix, 'posix_fallocate'),
         "test needs posix.posix_fallocate()")
     def test_posix_fallocate(self):
diff --git a/Misc/NEWS.d/next/Core and Builtins/2018-01-19-01-54-22.bpo-31368.kzKqUR.rst b/Misc/NEWS.d/next/Core and Builtins/2018-01-19-01-54-22.bpo-31368.kzKqUR.rst
index a614ab64628423..97314d833cda0f 100644
--- a/Misc/NEWS.d/next/Core and Builtins/2018-01-19-01-54-22.bpo-31368.kzKqUR.rst	
+++ b/Misc/NEWS.d/next/Core and Builtins/2018-01-19-01-54-22.bpo-31368.kzKqUR.rst	
@@ -1 +1,2 @@
-Expose preadv2 system call in the os module. Patch by Pablo Galindo
+Expose preadv (preadv2) and pwritev (pwritev2) system calls in the os module.
+Patch by Pablo Galindo
diff --git a/Modules/clinic/posixmodule.c.h b/Modules/clinic/posixmodule.c.h
index c2b7f327346b9c..dfbbf1f44be62f 100644
--- a/Modules/clinic/posixmodule.c.h
+++ b/Modules/clinic/posixmodule.c.h
@@ -4007,6 +4007,51 @@ os_pwrite(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
 
 #endif /* defined(HAVE_PWRITE) */
 
+#if (defined(HAVE_PWRITEV) || defined (HAVE_PWRITEV2))
+
+PyDoc_STRVAR(os_pwritev__doc__,
+"pwritev($module, fd, buffers, offset, flags=0, /)\n"
+"--\n"
+"\n"
+"Write bytes to a file descriptor starting at a particular offset.\n"
+"\n"
+"Write buffer to fd, starting at offset bytes from the beginning of\n"
+"the file.  Returns the number of bytes writte.  Does not change the\n"
+"current file offset.");
+
+#define OS_PWRITEV_METHODDEF    \
+    {"pwritev", (PyCFunction)os_pwritev, METH_FASTCALL, os_pwritev__doc__},
+
+static Py_ssize_t
+os_pwritev_impl(PyObject *module, int fd, PyObject *buffers, Py_off_t offset,
+                int flags);
+
+static PyObject *
+os_pwritev(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
+{
+    PyObject *return_value = NULL;
+    int fd;
+    PyObject *buffers;
+    Py_off_t offset;
+    int flags = 0;
+    Py_ssize_t _return_value;
+
+    if (!_PyArg_ParseStack(args, nargs, "iOO&|i:pwritev",
+        &fd, &buffers, Py_off_t_converter, &offset, &flags)) {
+        goto exit;
+    }
+    _return_value = os_pwritev_impl(module, fd, buffers, offset, flags);
+    if ((_return_value == -1) && PyErr_Occurred()) {
+        goto exit;
+    }
+    return_value = PyLong_FromSsize_t(_return_value);
+
+exit:
+    return return_value;
+}
+
+#endif /* (defined(HAVE_PWRITEV) || defined (HAVE_PWRITEV2)) */
+
 #if defined(HAVE_MKFIFO)
 
 PyDoc_STRVAR(os_mkfifo__doc__,
@@ -6303,6 +6348,10 @@ os_getrandom(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObject
     #define OS_PWRITE_METHODDEF
 #endif /* !defined(OS_PWRITE_METHODDEF) */
 
+#ifndef OS_PWRITEV_METHODDEF
+    #define OS_PWRITEV_METHODDEF
+#endif /* !defined(OS_PWRITEV_METHODDEF) */
+
 #ifndef OS_MKFIFO_METHODDEF
     #define OS_MKFIFO_METHODDEF
 #endif /* !defined(OS_MKFIFO_METHODDEF) */
@@ -6458,4 +6507,4 @@ os_getrandom(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObject
 #ifndef OS_GETRANDOM_METHODDEF
     #define OS_GETRANDOM_METHODDEF
 #endif /* !defined(OS_GETRANDOM_METHODDEF) */
-/*[clinic end generated code: output=52cbdec1822e34f9 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=d50830cf566cb297 input=a9049054013a1b77]*/
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index d146a00c98b466..baf9c8a0fa7ee6 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -8204,7 +8204,9 @@ os_preadv_impl(PyObject *module, int fd, PyObject *buffers, Py_off_t offset,
 #ifdef HAVE_PREADV2
     do {
         Py_BEGIN_ALLOW_THREADS
+        _Py_BEGIN_SUPPRESS_IPH
         n = preadv2(fd, iov, cnt, offset, flags);
+        _Py_END_SUPPRESS_IPH
         Py_END_ALLOW_THREADS
     } while (n < 0 && errno == EINTR && !(async_err = PyErr_CheckSignals()));
 #else
@@ -8215,7 +8217,9 @@ os_preadv_impl(PyObject *module, int fd, PyObject *buffers, Py_off_t offset,
     }
     do {
         Py_BEGIN_ALLOW_THREADS
+        _Py_BEGIN_SUPPRESS_IPH
         n = preadv(fd, iov, cnt, offset);
+        _Py_END_SUPPRESS_IPH
         Py_END_ALLOW_THREADS
     } while (n < 0 && errno == EINTR && !(async_err = PyErr_CheckSignals()));
 #endif
@@ -8681,6 +8685,82 @@ os_pwrite_impl(PyObject *module, int fd, Py_buffer *buffer, Py_off_t offset)
 }
 #endif /* HAVE_PWRITE */
 
+#if defined(HAVE_PWRITEV) || defined (HAVE_PWRITEV2)
+/*[clinic input]
+os.pwritev -> Py_ssize_t
+
+    fd: int
+    buffers: object
+    offset: Py_off_t
+    flags: int = 0
+    /
+
+Write bytes to a file descriptor starting at a particular offset.
+
+Write buffer to fd, starting at offset bytes from the beginning of
+the file.  Returns the number of bytes writte.  Does not change the
+current file offset.
+[clinic start generated code]*/
+
+static Py_ssize_t
+os_pwritev_impl(PyObject *module, int fd, PyObject *buffers, Py_off_t offset,
+                int flags)
+/*[clinic end generated code: output=e3dd3e9d11a6a5c7 input=76ec1699089ae61c]*/
+{
+    Py_ssize_t cnt;
+    Py_ssize_t result;
+    int async_err = 0;
+    struct iovec *iov;
+    Py_buffer *buf;
+
+    if (!PySequence_Check(buffers)) {
+        PyErr_SetString(PyExc_TypeError,
+            "pwritev() arg 2 must be a sequence");
+        return -1;
+    }
+
+    cnt = PySequence_Size(buffers);
+    if (cnt < 0)
+        return -1;
+
+    if (iov_setup(&iov, &buf, buffers, cnt, PyBUF_SIMPLE) < 0)
+        return -1;
+#ifdef HAVE_PWRITEV2
+    do {
+        Py_BEGIN_ALLOW_THREADS
+        _Py_BEGIN_SUPPRESS_IPH
+        result = pwritev2(fd, iov, cnt, offset, flags);
+        _Py_END_SUPPRESS_IPH
+        Py_END_ALLOW_THREADS
+    } while (result < 0 && errno == EINTR && !(async_err = PyErr_CheckSignals()));
+#else
+    if(flags != 0){
+        PyErr_SetString(PyExc_OSError, "pwritev2() not available in this system");
+        iov_cleanup(iov, buf, cnt);
+        return -1;
+    }
+    do {
+        Py_BEGIN_ALLOW_THREADS
+        _Py_BEGIN_SUPPRESS_IPH
+        result = pwritev(fd, iov, cnt, offset);
+        _Py_END_SUPPRESS_IPH
+        Py_END_ALLOW_THREADS
+    } while (result < 0 && errno == EINTR && !(async_err = PyErr_CheckSignals()));
+#endif
+
+    iov_cleanup(iov, buf, cnt);
+    if (result < 0) {
+        if (!async_err)
+            posix_error();
+        return -1;
+    }
+
+    return result;
+}
+#endif /* HAVE_PWRITEV */
+
+
+
 
 #ifdef HAVE_MKFIFO
 /*[clinic input]
@@ -12578,6 +12658,7 @@ static PyMethodDef posix_methods[] = {
     OS_WRITE_METHODDEF
     OS_WRITEV_METHODDEF
     OS_PWRITE_METHODDEF
+    OS_PWRITEV_METHODDEF
 #ifdef HAVE_SENDFILE
     {"sendfile",        (PyCFunction)posix_sendfile, METH_VARARGS | METH_KEYWORDS,
                             posix_sendfile__doc__},
diff --git a/configure b/configure
index ca1557ef118beb..2603cd9dbc5082 100755
--- a/configure
+++ b/configure
@@ -11202,7 +11202,7 @@ for ac_func in alarm accept4 setitimer getitimer bind_textdomain_codeset chown \
  memrchr mbrtowc mkdirat mkfifo \
  mkfifoat mknod mknodat mktime mremap nice openat pathconf pause pipe2 plock poll \
  posix_fallocate posix_fadvise pread preadv preadv2 \
- pthread_init pthread_kill putenv pwrite readlink readlinkat readv realpath renameat \
+ pthread_init pthread_kill putenv pwrite pwritev pwritev2 readlink readlinkat readv realpath renameat \
  sem_open sem_timedwait sem_getvalue sem_unlink sendfile setegid seteuid \
  setgid sethostname \
  setlocale setregid setreuid setresuid setresgid setsid setpgid setpgrp setpriority setuid setvbuf \
diff --git a/configure.ac b/configure.ac
index df92ea8dd33c30..1002788cd9e587 100644
--- a/configure.ac
+++ b/configure.ac
@@ -3436,7 +3436,7 @@ AC_CHECK_FUNCS(alarm accept4 setitimer getitimer bind_textdomain_codeset chown \
  memrchr mbrtowc mkdirat mkfifo \
  mkfifoat mknod mknodat mktime mremap nice openat pathconf pause pipe2 plock poll \
  posix_fallocate posix_fadvise pread preadv preadv2 \
- pthread_init pthread_kill putenv pwrite readlink readlinkat readv realpath renameat \
+ pthread_init pthread_kill putenv pwrite pwritev pwritev2 readlink readlinkat readv realpath renameat \
  sem_open sem_timedwait sem_getvalue sem_unlink sendfile setegid seteuid \
  setgid sethostname \
  setlocale setregid setreuid setresuid setresgid setsid setpgid setpgrp setpriority setuid setvbuf \
diff --git a/pyconfig.h.in b/pyconfig.h.in
index d98d6e7cb2628a..03beda6623e978 100644
--- a/pyconfig.h.in
+++ b/pyconfig.h.in
@@ -749,6 +749,12 @@
 /* Define to 1 if you have the `pwrite' function. */
 #undef HAVE_PWRITE
 
+/* Define to 1 if you have the `pwritev' function. */
+#undef HAVE_PWRITEV
+
+/* Define to 1 if you have the `pwritev2' function. */
+#undef HAVE_PWRITEV2
+
 /* Define to 1 if you have the `readlink' function. */
 #undef HAVE_READLINK
 

From f7cdf227c9c96a1216b9ecaec55164f7de89f63e Mon Sep 17 00:00:00 2001
From: Pablo Galindo <pablogsal@gmail.com>
Date: Tue, 23 Jan 2018 01:12:48 +0000
Subject: [PATCH 10/14] Fix style issues and Docs

---
 Doc/library/os.rst    | 34 ++++++++++++++++++++++++++--------
 Modules/posixmodule.c | 36 ++++++++++++++++++++++--------------
 2 files changed, 48 insertions(+), 22 deletions(-)

diff --git a/Doc/library/os.rst b/Doc/library/os.rst
index 739726e96717c8..b6a411f9b5f98b 100644
--- a/Doc/library/os.rst
+++ b/Doc/library/os.rst
@@ -1112,14 +1112,23 @@ or `the MSDN <https://msdn.microsoft.com/en-us/library/z0kc8e3z.aspx>`_ on Windo
    :func:`~os.pwritev` writes the contents of each object to the file descriptor
    and returns the total number of bytes written.
 
-   If the *flags* argument is provided it will invoke the *pwritev2* system
-   call, which modifies the behavior on a per-call basis based on the value
-   of the *flags* argument. If this argument is ommited, the *pwritev* system
-   call will be called instead.
+   :func:`~os.pwritev` will call *pwritev2* system call if available, which modifies
+   the behavior on a per-call basis based on the value of the *flags* argument. If
+   the *flags* argument is provided and different than zero, and *pwritev2* is not
+   available, it will raise a :exc:`NotImplementedError`.
+
+   *pwritev2* and flags different than zero are available since Linux version
+   4.7 and newer.
 
    The flags argument contains a bitwise OR of zero or more of the following
    flags:
 
+   Availability: Unix (version 2.6.30), FreeBSD (version 6.0 and newer),
+   OpenBSD (version 2.7 and newer).
+
+   .. versionadded:: 3.7
+
+
 .. data:: RWF_DSYNC
           RWF_SYNC
 
@@ -1235,14 +1244,23 @@ or `the MSDN <https://msdn.microsoft.com/en-us/library/z0kc8e3z.aspx>`_ on Windo
    :func:`~os.preadv` return the total number of bytes read (which may be less than
    the total capacity of all the objects).
 
-   If the *flags* argument is provided it will invoke the *preadv2* system
-   call, which modifies the behavior on a per-call basis based on the value
-   of the *flags* argument. If this argument is ommited, the *preadv* system
-   call will be called instead.
+   :func:`~os.preadv` will call *preadv2* system call if available, which modifies
+   the behavior on a per-call basis based on the value of the *flags* argument. If
+   the *flags* argument is provided and different than zero, and *preadv2* is not
+   available, it will raise a :exc:`NotImplementedError`.
+
+   *preadv2* and flags different than zero are available since Linux version
+   4.6 and newer.
 
    The flags argument contains a bitwise OR of zero or more of the following
    flags:
 
+   Availability: Unix (version 2.6.30), FreeBSD (version 6.0 and newer),
+   OpenBSD (version 2.7 and newer).
+
+   .. versionadded:: 3.7
+
+
 .. data:: RWF_HIPRI
           RWF_NOWAIT
 
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index baf9c8a0fa7ee6..d416de8c635520 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -8196,11 +8196,20 @@ os_preadv_impl(PyObject *module, int fd, PyObject *buffers, Py_off_t offset,
     }
 
     cnt = PySequence_Size(buffers);
-    if (cnt < 0)
+    if (cnt < 0){
         return -1;
+    }
 
-    if (iov_setup(&iov, &buf, buffers, cnt, PyBUF_WRITABLE) < 0)
+#ifndef HAVE_PREADV2
+    if(flags != 0){
+        argument_unavailable_error("preadv2", "preadv2() not available in this system");
+        return -1;
+    }
+#endif
+
+    if (iov_setup(&iov, &buf, buffers, cnt, PyBUF_WRITABLE) < 0){
         return -1;
+    }
 #ifdef HAVE_PREADV2
     do {
         Py_BEGIN_ALLOW_THREADS
@@ -8210,11 +8219,6 @@ os_preadv_impl(PyObject *module, int fd, PyObject *buffers, Py_off_t offset,
         Py_END_ALLOW_THREADS
     } while (n < 0 && errno == EINTR && !(async_err = PyErr_CheckSignals()));
 #else
-    if(flags != 0){
-        PyErr_SetString(PyExc_OSError, "preadv2() not available in this system");
-        iov_cleanup(iov, buf, cnt);
-        return -1;
-    }
     do {
         Py_BEGIN_ALLOW_THREADS
         _Py_BEGIN_SUPPRESS_IPH
@@ -8720,11 +8724,20 @@ os_pwritev_impl(PyObject *module, int fd, PyObject *buffers, Py_off_t offset,
     }
 
     cnt = PySequence_Size(buffers);
-    if (cnt < 0)
+    if (cnt < 0){
         return -1;
+    }
 
-    if (iov_setup(&iov, &buf, buffers, cnt, PyBUF_SIMPLE) < 0)
+#ifndef HAVE_PWRITEV2
+    if(flags != 0){
+        argument_unavailable_error("pwritev2", "pwritev2() not available in this system");
         return -1;
+    }
+#endif
+
+    if (iov_setup(&iov, &buf, buffers, cnt, PyBUF_SIMPLE) < 0){
+        return -1;
+    }
 #ifdef HAVE_PWRITEV2
     do {
         Py_BEGIN_ALLOW_THREADS
@@ -8734,11 +8747,6 @@ os_pwritev_impl(PyObject *module, int fd, PyObject *buffers, Py_off_t offset,
         Py_END_ALLOW_THREADS
     } while (result < 0 && errno == EINTR && !(async_err = PyErr_CheckSignals()));
 #else
-    if(flags != 0){
-        PyErr_SetString(PyExc_OSError, "pwritev2() not available in this system");
-        iov_cleanup(iov, buf, cnt);
-        return -1;
-    }
     do {
         Py_BEGIN_ALLOW_THREADS
         _Py_BEGIN_SUPPRESS_IPH

From 47f65b53ae5c27a040b48ba666f015464119b9cf Mon Sep 17 00:00:00 2001
From: Pablo Galindo <pablogsal@gmail.com>
Date: Tue, 23 Jan 2018 01:50:41 +0000
Subject: [PATCH 11/14] Correct style, update docs, fix misused API

---
 Doc/library/os.rst    | 39 +++++++++++++++++++++++----------------
 Modules/posixmodule.c | 16 ++++++++--------
 2 files changed, 31 insertions(+), 24 deletions(-)

diff --git a/Doc/library/os.rst b/Doc/library/os.rst
index b6a411f9b5f98b..f978d1f71be4db 100644
--- a/Doc/library/os.rst
+++ b/Doc/library/os.rst
@@ -1112,18 +1112,23 @@ or `the MSDN <https://msdn.microsoft.com/en-us/library/z0kc8e3z.aspx>`_ on Windo
    :func:`~os.pwritev` writes the contents of each object to the file descriptor
    and returns the total number of bytes written.
 
+
+   The *flags* argument contains a bitwise OR of zero or more of the following
+   flags:
+
+       - RWF_DSYNC
+       - RWF_SYNC
+
    :func:`~os.pwritev` will call *pwritev2* system call if available, which modifies
-   the behavior on a per-call basis based on the value of the *flags* argument. If
-   the *flags* argument is provided and different than zero, and *pwritev2* is not
-   available, it will raise a :exc:`NotImplementedError`.
+   the behavior on a per-call basis based on the value of the *flags* argument. The
+   :func:`~os.pwritev2` function is required to pass flags.
 
-   *pwritev2* and flags different than zero are available since Linux version
+   *pwritev2* and *flags* different than zero are available since Linux version
    4.7 and newer.
 
-   The flags argument contains a bitwise OR of zero or more of the following
-   flags:
+   The :func:`~os.pwritev2` function is required to pass flags.
 
-   Availability: Unix (version 2.6.30), FreeBSD (version 6.0 and newer),
+   Availability: Linux (version 2.6.30), FreeBSD 6.0 and newer,
    OpenBSD (version 2.7 and newer).
 
    .. versionadded:: 3.7
@@ -1134,7 +1139,7 @@ or `the MSDN <https://msdn.microsoft.com/en-us/library/z0kc8e3z.aspx>`_ on Windo
 
    The above constants are available on Linux Kernel 4.7 (or newer).
 
-   Availability: Unix.
+   Availability: Linux.
 
    .. versionadded:: 3.7
 
@@ -1244,18 +1249,20 @@ or `the MSDN <https://msdn.microsoft.com/en-us/library/z0kc8e3z.aspx>`_ on Windo
    :func:`~os.preadv` return the total number of bytes read (which may be less than
    the total capacity of all the objects).
 
+   The flags argument contains a bitwise OR of zero or more of the following
+   flags:
+
+       - RWF_HIPRI
+       - RWF_NOWAIT
+
    :func:`~os.preadv` will call *preadv2* system call if available, which modifies
-   the behavior on a per-call basis based on the value of the *flags* argument. If
-   the *flags* argument is provided and different than zero, and *preadv2* is not
-   available, it will raise a :exc:`NotImplementedError`.
+   the behavior on a per-call basis based on the value of the *flags* argument. The
+   :func:`~os.preadv2` function is required to pass flags.
 
    *preadv2* and flags different than zero are available since Linux version
    4.6 and newer.
 
-   The flags argument contains a bitwise OR of zero or more of the following
-   flags:
-
-   Availability: Unix (version 2.6.30), FreeBSD (version 6.0 and newer),
+   Availability: Linux (version 2.6.30), FreeBSD 6.0 and newer,
    OpenBSD (version 2.7 and newer).
 
    .. versionadded:: 3.7
@@ -1267,7 +1274,7 @@ or `the MSDN <https://msdn.microsoft.com/en-us/library/z0kc8e3z.aspx>`_ on Windo
    The above constants are available on Linux Kernel 4.11 and 4.6 (or newer)
    respectively.
 
-   Availability: Unix.
+   Availability: Linux.
 
    .. versionadded:: 3.7
 
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index d416de8c635520..10e6aaf5b6745d 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -8196,18 +8196,18 @@ os_preadv_impl(PyObject *module, int fd, PyObject *buffers, Py_off_t offset,
     }
 
     cnt = PySequence_Size(buffers);
-    if (cnt < 0){
+    if (cnt < 0) {
         return -1;
     }
 
 #ifndef HAVE_PREADV2
-    if(flags != 0){
-        argument_unavailable_error("preadv2", "preadv2() not available in this system");
+    if(flags != 0) {
+        argument_unavailable_error("preadv2", "flags");
         return -1;
     }
 #endif
 
-    if (iov_setup(&iov, &buf, buffers, cnt, PyBUF_WRITABLE) < 0){
+    if (iov_setup(&iov, &buf, buffers, cnt, PyBUF_WRITABLE) < 0) {
         return -1;
     }
 #ifdef HAVE_PREADV2
@@ -8724,18 +8724,18 @@ os_pwritev_impl(PyObject *module, int fd, PyObject *buffers, Py_off_t offset,
     }
 
     cnt = PySequence_Size(buffers);
-    if (cnt < 0){
+    if (cnt < 0) {
         return -1;
     }
 
 #ifndef HAVE_PWRITEV2
-    if(flags != 0){
-        argument_unavailable_error("pwritev2", "pwritev2() not available in this system");
+    if(flags != 0) {
+        argument_unavailable_error("pwritev2", "flags");
         return -1;
     }
 #endif
 
-    if (iov_setup(&iov, &buf, buffers, cnt, PyBUF_SIMPLE) < 0){
+    if (iov_setup(&iov, &buf, buffers, cnt, PyBUF_SIMPLE) < 0) {
         return -1;
     }
 #ifdef HAVE_PWRITEV2

From 87c69701afdab34eaf1492a9821262441da4b96e Mon Sep 17 00:00:00 2001
From: Pablo Galindo <pablogsal@gmail.com>
Date: Fri, 26 Jan 2018 11:57:12 -0500
Subject: [PATCH 12/14] Improve tests, clean names and correct style

---
 Lib/test/test_posix.py | 35 ++++++++++++++++++-----------------
 Modules/posixmodule.c  |  6 ++++--
 2 files changed, 22 insertions(+), 19 deletions(-)

diff --git a/Lib/test/test_posix.py b/Lib/test/test_posix.py
index ddf576a58955b1..362b826149c651 100644
--- a/Lib/test/test_posix.py
+++ b/Lib/test/test_posix.py
@@ -276,23 +276,21 @@ def test_pread(self):
     def test_preadv(self):
         fd = os.open(support.TESTFN, os.O_RDWR | os.O_CREAT)
         try:
-            os.write(fd, b'test1tt2t3')
-            os.lseek(fd, 0, os.SEEK_SET)
+            os.write(fd, b'test1tt2t3t5t6t6t8')
             buf = [bytearray(i) for i in [5, 3, 2]]
-            self.assertEqual(posix.preadv(fd, buf, 0), 10)
-            self.assertEqual([b'test1', b'tt2', b't3'], [bytes(i) for i in buf])
+            self.assertEqual(posix.preadv(fd, buf, 3), 10)
+            self.assertEqual([b't1tt2', b't3t', b'5t'], list(buf))
         finally:
             os.close(fd)
 
-    @unittest.skipUnless(hasattr(posix, 'RWF_HIPRI'), "test needs posix.preadv2()")
-    def test_preadv2(self):
+    @unittest.skipUnless(hasattr(posix, 'RWF_HIPRI'), "test needs posix.RWF_HIPRI")
+    def test_preadv_flags(self):
         fd = os.open(support.TESTFN, os.O_RDWR | os.O_CREAT)
         try:
-            os.write(fd, b'test1tt2t3')
-            os.lseek(fd, 0, os.SEEK_SET)
+            os.write(fd, b'test1tt2t3t5t6t6t8')
             buf = [bytearray(i) for i in [5, 3, 2]]
-            self.assertEqual(posix.preadv(fd, buf, 0, os.RWF_HIPRI), 10)
-            self.assertEqual([b'test1', b'tt2', b't3'], [bytes(i) for i in buf])
+            self.assertEqual(posix.preadv(fd, buf, 3, os.RWF_HIPRI), 10)
+            self.assertEqual([b't1tt2', b't3t', b'5t'], list(buf))
         finally:
             os.close(fd)
 
@@ -311,26 +309,29 @@ def test_pwrite(self):
     def test_pwritev(self):
         fd = os.open(support.TESTFN, os.O_RDWR | os.O_CREAT)
         try:
-            n = os.pwritev(fd, [b'test1tt2t3'],2)
+            os.write(fd,b"xx")
+            os.lseek(fd, 0, os.SEEK_SET)
+            n = os.pwritev(fd, [b'test1', b'tt2', b't3'], 2)
             self.assertEqual(n, 10)
 
             os.lseek(fd, 0, os.SEEK_SET)
-            self.assertEqual(b'\x00\x00test1tt2', posix.read(fd, 10))
+            self.assertEqual(b'xxtest1tt2', posix.read(fd, 10))
 
         finally:
             os.close(fd)
 
 
-    @unittest.skipUnless(hasattr(posix, 'os.RWF_SYNC'), "test needs posix.pwritev2()")
-    def test_pwritev2(self):
+    @unittest.skipUnless(hasattr(posix, 'os.RWF_SYNC'), "test needs os.RWF_SYNC")
+    def test_pwritev_flags(self):
         fd = os.open(support.TESTFN, os.O_RDWR | os.O_CREAT)
         try:
-            n = os.pwritev(fd, [b'test1tt2t3'],2, os.RWF_SYNC)
+            os.write(fd,b"xx")
+            os.lseek(fd, 0, os.SEEK_SET)
+            n = os.pwritev(fd, [b'test1', b'tt2', b't3'], 2, os.RWF_SYNC)
             self.assertEqual(n, 10)
 
             os.lseek(fd, 0, os.SEEK_SET)
-            self.assertEqual(b'\x00\x00test1tt2', posix.read(fd, 10))
-
+            self.assertEqual(b'xxtest1tt2', posix.read(fd, 10))
         finally:
             os.close(fd)
 
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index 10e6aaf5b6745d..4f0e7fdcb3a9d7 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -8230,8 +8230,9 @@ os_preadv_impl(PyObject *module, int fd, PyObject *buffers, Py_off_t offset,
 
     iov_cleanup(iov, buf, cnt);
     if (n < 0) {
-        if (!async_err)
+        if (!async_err) {
             posix_error();
+        }
         return -1;
     }
 
@@ -8758,8 +8759,9 @@ os_pwritev_impl(PyObject *module, int fd, PyObject *buffers, Py_off_t offset,
 
     iov_cleanup(iov, buf, cnt);
     if (result < 0) {
-        if (!async_err)
+        if (!async_err) {
             posix_error();
+        }
         return -1;
     }
 

From cb74d38bb0f4ff1a9e28279afeca908d92cf0634 Mon Sep 17 00:00:00 2001
From: Pablo Galindo <pablogsal@gmail.com>
Date: Fri, 26 Jan 2018 12:03:01 -0500
Subject: [PATCH 13/14] Correct documentation

---
 Doc/library/os.rst | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/Doc/library/os.rst b/Doc/library/os.rst
index f978d1f71be4db..49a5ad043b516f 100644
--- a/Doc/library/os.rst
+++ b/Doc/library/os.rst
@@ -1104,10 +1104,10 @@ or `the MSDN <https://msdn.microsoft.com/en-us/library/z0kc8e3z.aspx>`_ on Windo
 .. function:: pwritev(fd, buffers, offset, flags=0)
 
    Combines the functionality of :func:`os.writev` and :func:`os.pwrite`. It
-   writes the contents of *buffers* to file descriptor *fd*. *buffers* must be
-   a sequence of :term:`bytes-like objects <bytes-like object>`. Buffers are
-   processed in array order. Entire contents of first buffer is written before
-   proceeding to second, and so on. The operating system may set a limit
+   writes the contents of *buffers* to file descriptor *fd* at offset *offset*.
+   *buffers* must be a sequence of :term:`bytes-like objects <bytes-like object>`.
+   Buffers are processed in array order. Entire contents of first buffer is written
+   before proceeding to second, and so on. The operating system may set a limit
    (sysconf() value SC_IOV_MAX) on the number of buffers that can be used.
    :func:`~os.pwritev` writes the contents of each object to the file descriptor
    and returns the total number of bytes written.
@@ -1116,18 +1116,18 @@ or `the MSDN <https://msdn.microsoft.com/en-us/library/z0kc8e3z.aspx>`_ on Windo
    The *flags* argument contains a bitwise OR of zero or more of the following
    flags:
 
-       - RWF_DSYNC
-       - RWF_SYNC
+   - RWF_DSYNC
+   - RWF_SYNC
 
    :func:`~os.pwritev` will call *pwritev2* system call if available, which modifies
    the behavior on a per-call basis based on the value of the *flags* argument. The
    :func:`~os.pwritev2` function is required to pass flags.
 
-   *pwritev2* and *flags* different than zero are available since Linux version
-   4.7 and newer.
-
    The :func:`~os.pwritev2` function is required to pass flags.
 
+   *pwritev2* and *flags* different than zero are available since Linux version
+   4.7.
+
    Availability: Linux (version 2.6.30), FreeBSD 6.0 and newer,
    OpenBSD (version 2.7 and newer).
 
@@ -1246,7 +1246,7 @@ or `the MSDN <https://msdn.microsoft.com/en-us/library/z0kc8e3z.aspx>`_ on Windo
    data into each buffer until it is full and then move on to the next buffer in
    the sequence to hold the rest of the data. Its fourth argument, *offset*,
    specifies the file offset at which the input operation is to be performed.
-   :func:`~os.preadv` return the total number of bytes read (which may be less than
+   :func:`~os.preadv` return the total number of bytes read (which can be less than
    the total capacity of all the objects).
 
    The flags argument contains a bitwise OR of zero or more of the following
@@ -1257,7 +1257,7 @@ or `the MSDN <https://msdn.microsoft.com/en-us/library/z0kc8e3z.aspx>`_ on Windo
 
    :func:`~os.preadv` will call *preadv2* system call if available, which modifies
    the behavior on a per-call basis based on the value of the *flags* argument. The
-   :func:`~os.preadv2` function is required to pass flags.
+   :c:func:`preadv2` function is required to pass flags.
 
    *preadv2* and flags different than zero are available since Linux version
    4.6 and newer.

From 5563b8db0c784e0cf545bdcba1fc6b7075e87701 Mon Sep 17 00:00:00 2001
From: Pablo Galindo <pablogsal@gmail.com>
Date: Sat, 27 Jan 2018 12:51:05 +0000
Subject: [PATCH 14/14] Correct typos, docstring and improve Docs

---
 Doc/library/os.rst                            | 54 +++++++++----------
 Lib/test/test_posix.py                        |  9 ++--
 .../2018-01-19-01-54-22.bpo-31368.kzKqUR.rst  |  3 +-
 Modules/clinic/posixmodule.c.h                | 37 ++++++++++---
 Modules/posixmodule.c                         | 39 ++++++++++----
 5 files changed, 90 insertions(+), 52 deletions(-)

diff --git a/Doc/library/os.rst b/Doc/library/os.rst
index 49a5ad043b516f..6ea8cdce678678 100644
--- a/Doc/library/os.rst
+++ b/Doc/library/os.rst
@@ -1112,34 +1112,30 @@ or `the MSDN <https://msdn.microsoft.com/en-us/library/z0kc8e3z.aspx>`_ on Windo
    :func:`~os.pwritev` writes the contents of each object to the file descriptor
    and returns the total number of bytes written.
 
-
    The *flags* argument contains a bitwise OR of zero or more of the following
    flags:
 
    - RWF_DSYNC
    - RWF_SYNC
 
-   :func:`~os.pwritev` will call *pwritev2* system call if available, which modifies
-   the behavior on a per-call basis based on the value of the *flags* argument. The
-   :func:`~os.pwritev2` function is required to pass flags.
-
-   The :func:`~os.pwritev2` function is required to pass flags.
-
-   *pwritev2* and *flags* different than zero are available since Linux version
-   4.7.
+   Using non-zero flags requires Linux 4.7 or newer.
 
    Availability: Linux (version 2.6.30), FreeBSD 6.0 and newer,
    OpenBSD (version 2.7 and newer).
 
    .. versionadded:: 3.7
 
+.. data:: RWF_DSYNC (since Linux 4.7)
+   Provide a per-write equivalent of the O_DSYNC open(2) flag. This flag
+   is meaningful only for pwritev2(), and its effect applies only to the
+   data range written by the system call.
 
-.. data:: RWF_DSYNC
-          RWF_SYNC
-
-   The above constants are available on Linux Kernel 4.7 (or newer).
+   .. versionadded:: 3.7
 
-   Availability: Linux.
+.. data:: RWF_SYNC (since Linux 4.7)
+   Provide a per-write equivalent of the O_SYNC open(2) flag. This flag is
+   meaningful only for pwritev2(), and its effect applies only to the data
+   range written by the system call.
 
    .. versionadded:: 3.7
 
@@ -1252,15 +1248,10 @@ or `the MSDN <https://msdn.microsoft.com/en-us/library/z0kc8e3z.aspx>`_ on Windo
    The flags argument contains a bitwise OR of zero or more of the following
    flags:
 
-       - RWF_HIPRI
-       - RWF_NOWAIT
+   - RWF_HIPRI
+   - RWF_NOWAIT
 
-   :func:`~os.preadv` will call *preadv2* system call if available, which modifies
-   the behavior on a per-call basis based on the value of the *flags* argument. The
-   :c:func:`preadv2` function is required to pass flags.
-
-   *preadv2* and flags different than zero are available since Linux version
-   4.6 and newer.
+   Using non-zero flags requires Linux 4.6 or newer.
 
    Availability: Linux (version 2.6.30), FreeBSD 6.0 and newer,
    OpenBSD (version 2.7 and newer).
@@ -1268,13 +1259,22 @@ or `the MSDN <https://msdn.microsoft.com/en-us/library/z0kc8e3z.aspx>`_ on Windo
    .. versionadded:: 3.7
 
 
-.. data:: RWF_HIPRI
-          RWF_NOWAIT
+.. data:: RWF_HIPRI (since Linux 4.6)
+   High priority read/write. Allows block-based filesystems to use polling
+   of the device, which provides lower latency, but may use additional
+   resources. (Currently, this feature is usable only on a file descriptor
+   opened using the O_DIRECT flag.)
+
+   .. versionadded:: 3.7
 
-   The above constants are available on Linux Kernel 4.11 and 4.6 (or newer)
-   respectively.
 
-   Availability: Linux.
+.. data:: RWF_NOWAIT (since Linux 4.14)
+   Do not wait for data which is not immediately available. If this flag
+   is  specified, the preadv2() system call will return instantly
+   if it would have to read data from the backing storage or wait for a lock.
+   If some data was successfully read, it will return the number of bytes
+   read. If no bytes were read, it will return -1 and set errno to EAGAIN.
+   Currently, this flag is meaningful only for preadv2().
 
    .. versionadded:: 3.7
 
diff --git a/Lib/test/test_posix.py b/Lib/test/test_posix.py
index 362b826149c651..f2d63666c750af 100644
--- a/Lib/test/test_posix.py
+++ b/Lib/test/test_posix.py
@@ -309,18 +309,16 @@ def test_pwrite(self):
     def test_pwritev(self):
         fd = os.open(support.TESTFN, os.O_RDWR | os.O_CREAT)
         try:
-            os.write(fd,b"xx")
+            os.write(fd, b"xx")
             os.lseek(fd, 0, os.SEEK_SET)
             n = os.pwritev(fd, [b'test1', b'tt2', b't3'], 2)
             self.assertEqual(n, 10)
 
             os.lseek(fd, 0, os.SEEK_SET)
-            self.assertEqual(b'xxtest1tt2', posix.read(fd, 10))
-
+            self.assertEqual(b'xxtest1tt2t3', posix.read(fd, 100))
         finally:
             os.close(fd)
 
-
     @unittest.skipUnless(hasattr(posix, 'os.RWF_SYNC'), "test needs os.RWF_SYNC")
     def test_pwritev_flags(self):
         fd = os.open(support.TESTFN, os.O_RDWR | os.O_CREAT)
@@ -331,11 +329,10 @@ def test_pwritev_flags(self):
             self.assertEqual(n, 10)
 
             os.lseek(fd, 0, os.SEEK_SET)
-            self.assertEqual(b'xxtest1tt2', posix.read(fd, 10))
+            self.assertEqual(b'xxtest1tt2', posix.read(fd, 100))
         finally:
             os.close(fd)
 
-
     @unittest.skipUnless(hasattr(posix, 'posix_fallocate'),
         "test needs posix.posix_fallocate()")
     def test_posix_fallocate(self):
diff --git a/Misc/NEWS.d/next/Core and Builtins/2018-01-19-01-54-22.bpo-31368.kzKqUR.rst b/Misc/NEWS.d/next/Core and Builtins/2018-01-19-01-54-22.bpo-31368.kzKqUR.rst
index 97314d833cda0f..e13a58bb2c208a 100644
--- a/Misc/NEWS.d/next/Core and Builtins/2018-01-19-01-54-22.bpo-31368.kzKqUR.rst	
+++ b/Misc/NEWS.d/next/Core and Builtins/2018-01-19-01-54-22.bpo-31368.kzKqUR.rst	
@@ -1,2 +1 @@
-Expose preadv (preadv2) and pwritev (pwritev2) system calls in the os module.
-Patch by Pablo Galindo
+Expose preadv and pwritev system calls in the os module. Patch by Pablo Galindo
diff --git a/Modules/clinic/posixmodule.c.h b/Modules/clinic/posixmodule.c.h
index dfbbf1f44be62f..f432437e99efe1 100644
--- a/Modules/clinic/posixmodule.c.h
+++ b/Modules/clinic/posixmodule.c.h
@@ -3711,10 +3711,21 @@ PyDoc_STRVAR(os_preadv__doc__,
 "preadv($module, fd, buffers, offset, flags=0, /)\n"
 "--\n"
 "\n"
-"Read a number of bytes from a file descriptor starting at a particular offset.\n"
+"Reads from a file descriptor into a number of mutable bytes-like objects.\n"
 "\n"
-"Read length bytes from file descriptor fd, starting at offset bytes from\n"
-"the beginning of the file.  The file offset remains unchanged.");
+"Combines the functionality of readv() and pread(). As readv(), it will\n"
+"transfer data into each buffer until it is full and then move on to the next\n"
+"buffer in the sequence to hold the rest of the data. Its fourth argument,\n"
+"specifies the file offset at which the input operation is to be performed. It\n"
+"will return the total number of bytes read (which can be less than the total\n"
+"capacity of all the objects).\n"
+"\n"
+"The flags argument contains a bitwise OR of zero or more of the following flags:\n"
+"\n"
+"- RWF_HIPRI\n"
+"- RWF_NOWAIT\n"
+"\n"
+"Using non-zero flags requires Linux 4.6 or newer.");
 
 #define OS_PREADV_METHODDEF    \
     {"preadv", (PyCFunction)os_preadv, METH_FASTCALL, os_preadv__doc__},
@@ -4013,11 +4024,21 @@ PyDoc_STRVAR(os_pwritev__doc__,
 "pwritev($module, fd, buffers, offset, flags=0, /)\n"
 "--\n"
 "\n"
-"Write bytes to a file descriptor starting at a particular offset.\n"
+"Writes the contents of bytes-like objects to a file descriptor at a given offset.\n"
 "\n"
-"Write buffer to fd, starting at offset bytes from the beginning of\n"
-"the file.  Returns the number of bytes writte.  Does not change the\n"
-"current file offset.");
+"Combines the functionality of writev() and pwrite(). All buffers must be a sequence\n"
+"of bytes-like objects. Buffers are processed in array order. Entire contents of first\n"
+"buffer is written before proceeding to second, and so on. The operating system may\n"
+"set a limit (sysconf() value SC_IOV_MAX) on the number of buffers that can be used.\n"
+"This function writes the contents of each object to the file descriptor and returns\n"
+"the total number of bytes written.\n"
+"\n"
+"The flags argument contains a bitwise OR of zero or more of the following flags:\n"
+"\n"
+"- RWF_DSYNC\n"
+"- RWF_SYNC\n"
+"\n"
+"Using non-zero flags requires Linux 4.7 or newer.");
 
 #define OS_PWRITEV_METHODDEF    \
     {"pwritev", (PyCFunction)os_pwritev, METH_FASTCALL, os_pwritev__doc__},
@@ -6507,4 +6528,4 @@ os_getrandom(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObject
 #ifndef OS_GETRANDOM_METHODDEF
     #define OS_GETRANDOM_METHODDEF
 #endif /* !defined(OS_GETRANDOM_METHODDEF) */
-/*[clinic end generated code: output=d50830cf566cb297 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=06ace805893aa10c input=a9049054013a1b77]*/
diff --git a/Modules/posixmodule.c b/Modules/posixmodule.c
index 4f0e7fdcb3a9d7..a1a38ebda387f5 100644
--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -8173,16 +8173,27 @@ os.preadv -> Py_ssize_t
     flags: int = 0
     /
 
-Read a number of bytes from a file descriptor starting at a particular offset.
+Reads from a file descriptor into a number of mutable bytes-like objects.
 
-Read length bytes from file descriptor fd, starting at offset bytes from
-the beginning of the file.  The file offset remains unchanged.
+Combines the functionality of readv() and pread(). As readv(), it will
+transfer data into each buffer until it is full and then move on to the next
+buffer in the sequence to hold the rest of the data. Its fourth argument,
+specifies the file offset at which the input operation is to be performed. It
+will return the total number of bytes read (which can be less than the total
+capacity of all the objects).
+
+The flags argument contains a bitwise OR of zero or more of the following flags:
+
+- RWF_HIPRI
+- RWF_NOWAIT
+
+Using non-zero flags requires Linux 4.6 or newer.
 [clinic start generated code]*/
 
 static Py_ssize_t
 os_preadv_impl(PyObject *module, int fd, PyObject *buffers, Py_off_t offset,
                int flags)
-/*[clinic end generated code: output=26fc9c6e58e7ada5 input=5b07b7e2d1825627]*/
+/*[clinic end generated code: output=26fc9c6e58e7ada5 input=4173919dc1f7ed99]*/
 {
     Py_ssize_t cnt, n;
     int async_err = 0;
@@ -8700,17 +8711,27 @@ os.pwritev -> Py_ssize_t
     flags: int = 0
     /
 
-Write bytes to a file descriptor starting at a particular offset.
+Writes the contents of bytes-like objects to a file descriptor at a given offset.
 
-Write buffer to fd, starting at offset bytes from the beginning of
-the file.  Returns the number of bytes writte.  Does not change the
-current file offset.
+Combines the functionality of writev() and pwrite(). All buffers must be a sequence
+of bytes-like objects. Buffers are processed in array order. Entire contents of first
+buffer is written before proceeding to second, and so on. The operating system may
+set a limit (sysconf() value SC_IOV_MAX) on the number of buffers that can be used.
+This function writes the contents of each object to the file descriptor and returns
+the total number of bytes written.
+
+The flags argument contains a bitwise OR of zero or more of the following flags:
+
+- RWF_DSYNC
+- RWF_SYNC
+
+Using non-zero flags requires Linux 4.7 or newer.
 [clinic start generated code]*/
 
 static Py_ssize_t
 os_pwritev_impl(PyObject *module, int fd, PyObject *buffers, Py_off_t offset,
                 int flags)
-/*[clinic end generated code: output=e3dd3e9d11a6a5c7 input=76ec1699089ae61c]*/
+/*[clinic end generated code: output=e3dd3e9d11a6a5c7 input=803dc5ddbf0cfd3b]*/
 {
     Py_ssize_t cnt;
     Py_ssize_t result;