Move image conversion to privsep.

Following a similar pattern to previous changes, move calls to
qemu-img to convert between image formats to use privsep.

Change-Id: I2c3df909a783e1480d3ab4ca10b34b84ac9e4b5f
blueprint: hurrah-for-privsep

nova/utils.py

@@ -20,11 +20,9 @@
 import contextlib
 import copy
 import datetime
-import errno
 import functools
 import hashlib
 import inspect
-import mmap
 import os
 import pyclbr
 import random
@@ -1341,53 +1339,6 @@ def get_endpoint(ksa_adapter):
         "interfaces: %s" % interfaces)
 
 
-def supports_direct_io(dirpath):
-
-    if not hasattr(os, 'O_DIRECT'):
-        LOG.debug("This python runtime does not support direct I/O")
-        return False
-
-    testfile = os.path.join(dirpath, ".directio.test")
-
-    hasDirectIO = True
-    fd = None
-    try:
-        fd = os.open(testfile, os.O_CREAT | os.O_WRONLY | os.O_DIRECT)
-        # Check is the write allowed with 512 byte alignment
-        align_size = 512
-        m = mmap.mmap(-1, align_size)
-        m.write(b"x" * align_size)
-        os.write(fd, m)
-        LOG.debug("Path '%(path)s' supports direct I/O",
-                  {'path': dirpath})
-    except OSError as e:
-        if e.errno == errno.EINVAL:
-            LOG.debug("Path '%(path)s' does not support direct I/O: "
-                      "'%(ex)s'", {'path': dirpath, 'ex': e})
-            hasDirectIO = False
-        else:
-            with excutils.save_and_reraise_exception():
-                LOG.error("Error on '%(path)s' while checking "
-                          "direct I/O: '%(ex)s'",
-                          {'path': dirpath, 'ex': e})
-    except Exception as e:
-        with excutils.save_and_reraise_exception():
-            LOG.error("Error on '%(path)s' while checking direct I/O: "
-                      "'%(ex)s'", {'path': dirpath, 'ex': e})
-    finally:
-        # ensure unlink(filepath) will actually remove the file by deleting
-        # the remaining link to it in close(fd)
-        if fd is not None:
-            os.close(fd)
-
-        try:
-            os.unlink(testfile)
-        except Exception:
-            pass
-
-    return hasDirectIO
-
-
 def generate_hostid(host, project_id):
     """Generate an obfuscated host id representing the host.