core: pack ova through a loopback device

Simplify OVA creation by mounting disk portions in an OVA file
as loopback devices and then converting the images directly to
the OVA file using those loopback devices with qemu-img.

Change-Id: I4cf1e6275ac6e2355955675f6f5692bb7551871d
Bug-Url: https://bugzilla.redhat.com/1526033
Signed-off-by: Arik Hadas <ahadas@redhat.com>

packaging/playbooks/roles/ovirt-ova-export-pre-pack/tasks/main.yml

@@ -25,7 +25,11 @@
     state: absent
   when: validate_only is not defined
 
-- name: Prepare temporary path for the OVA file
+- name: Allocating the temporary path for the OVA file
+  command: xfs_mkfile -n "{{ ova_size }}" "{{ target_directory }}/{{ ova_name }}.tmp"
+  when: validate_only is not defined
+
+- name: Retrieving the temporary path for the OVA file
   file:
     path: "{{ target_directory }}/{{ ova_name }}.tmp"
     state: touch

packaging/playbooks/roles/ovirt-ova-pack/files/pack_ova.py

@@ -1,20 +1,19 @@
 #!/usr/bin/python
 
 import io
-import mmap
 import os
 import sys
 import tarfile
 import time
 
 
-from contextlib import closing
+from subprocess import call
+from subprocess import check_output
 
 TAR_BLOCK_SIZE = 512
 NUL = b"\0"
-BUF_SIZE = 8 * 1024**2
 
-python2 = sys.version_info < (3, 0)
+path_to_offset = {}
 
 
 def create_tar_info(name, size):
@@ -31,62 +30,46 @@ def pad_to_block_size(file):
         file.write(NUL * padding_size)
 
 
-def write_ovf(ova_path, ovf):
+def write_ovf(ova_file, ovf):
     print ("writing ovf: %s" % ovf)
-    with io.open(ova_path, "r+b") as ova_file:
-        tar_info = create_tar_info("vm.ovf", len(ovf))
-        ova_file.write(tar_info.tobuf())
-        ova_file.write(ovf)
-        pad_to_block_size(ova_file)
-        os.fsync(ova_file.fileno())
-
-
-def write_disk(ova_path, disk_path, disk_size):
-    print ("writing disk: path=%s size=%d" % (disk_path, disk_size))
-    disk_name = os.path.basename(disk_path)
-    tar_info = create_tar_info(disk_name, disk_size)
-    with io.open(ova_path, "a+b") as ova_file:
-        # write tar info
-        ova_file.write(tar_info.tobuf())
-        os.fsync(ova_file.fileno())
-
-    try:
-        fd = os.open(ova_path, os.O_RDWR | os.O_DIRECT | os.O_APPEND)
-    except OSError:
-        fd = os.open(ova_path, os.O_RDWR | os.O_APPEND)
-
-    with io.FileIO(fd, "a+", closefd=True) as ova_file:
-        # write the disk content
-        buf = mmap.mmap(-1, BUF_SIZE)
-        fd = os.open(disk_path, os.O_RDONLY | os.O_DIRECT)
-        with closing(buf), \
-                io.FileIO(fd, "r", closefd=True) as image:
-            while True:
-                read = image.readinto(buf)
-                if read == 0:
-                    break  # done
-                written = 0
-                while written < read:
-                    if python2:
-                        wbuf = buffer(buf, written, read - written)
-                    else:
-                        wbuf = memoryview(buf)[written:read - written]
-                    written += ova_file.write(wbuf)
-        os.fsync(ova_file.fileno())
-
-
-def write_disks(ova_path, disks_info):
+    tar_info = create_tar_info("vm.ovf", len(ovf))
+    ova_file.write(tar_info.tobuf())
+    ova_file.write(ovf)
+    pad_to_block_size(ova_file)
+    os.fsync(ova_file.fileno())
+
+
+def convert_disks(ova_path):
+    for path, offset in path_to_offset.iteritems():
+        print ("converting disk: %s, offset %s" % (path, offset))
+        output = check_output(['losetup', '--find', '--show', '-o', offset,
+                               ova_path])
+        loop = output.splitlines()[0]
+        try:
+            call(['qemu-img', 'convert', '-T', 'none', '-O', 'qcow2', path,
+                  loop])
+        finally:
+            call(['losetup', '-d', loop])
+
+
+def write_disk_headers(ova_file, disks_info):
     for disk_info in disks_info:
         # disk_info is of the following structure: <full path>::<size in bytes>
         idx = disk_info.index('::')
         disk_path = disk_info[:idx]
         disk_size = int(disk_info[idx+2:])
-        write_disk(ova_path, disk_path, disk_size)
+        print ("skipping disk: path=%s size=%d" % (disk_path, disk_size))
+        disk_name = os.path.basename(disk_path)
+        tar_info = create_tar_info(disk_name, disk_size)
+        # write tar info
+        ova_file.write(tar_info.tobuf())
+        path_to_offset[disk_path] = str(ova_file.tell())
+        ova_file.seek(disk_size, 1)
+    os.fsync(ova_file.fileno())
 
 
 def write_null_blocks(ova_file):
-    with io.open(ova_path, "a+b") as ova_file:
-        ova_file.write(NUL * 2 * TAR_BLOCK_SIZE)
+    ova_file.write(NUL * 2 * TAR_BLOCK_SIZE)
 
 
 if len(sys.argv) < 3:
@@ -95,9 +78,11 @@ def write_null_blocks(ova_file):
 
 ova_path = sys.argv[1]
 ovf = sys.argv[2]
-write_ovf(ova_path, ovf)
-if len(sys.argv) > 3:
-    disks_info = sys.argv[3]
-    write_disks(ova_path, disks_info.split('+'))
-# write two null blocks at the end of the file
-write_null_blocks(ova_path)
+with io.open(ova_path, "wb") as ova_file:
+    write_ovf(ova_file, ovf)
+    if len(sys.argv) > 3:
+        disks_info = sys.argv[3]
+        write_disk_headers(ova_file, disks_info.split('+'))
+    # write two null blocks at the end of the file
+    write_null_blocks(ova_file)
+convert_disks(ova_path)