add qemu-img convert -n option (skip target volume creation)

Add a -n option to skip volume creation on qemu-img convert.
This is useful for targets such as rbd / ceph, where the
target volume may already exist; we cannot always rely on
qemu-img convert to create the image, as dependent on the
output format, there may be parameters which are not possible
to specify through the qemu-img convert command line.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Alexandre Derumier <aderumier@odiso.com>
Signed-off-by: Alex Bligh <alex@alex.org.uk>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

tests/qemu-iotests/063

@@ -0,0 +1,97 @@
+#!/bin/bash
+#
+# test of qemu-img convert -n - convert without creation
+#
+# Copyright (C) 2009 Red Hat, Inc.
+# Copyright (C) 2013 Alex Bligh (alex@alex.org.uk)
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+# creator
+owner=alex@alex.org.uk
+
+seq=`basename $0`
+echo "QA output created by $seq"
+
+here=`pwd`
+tmp=/tmp/$$
+status=1	# failure is the default!
+
+_cleanup()
+{
+	_cleanup_test_img
+	rm -f $TEST_IMG.orig $TEST_IMG.raw $TEST_IMG.raw2
+}
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+# get standard environment, filters and checks
+. ./common.rc
+. ./common.filter
+. ./common.pattern
+
+_supported_fmt qcow qcow2 vmdk qed raw
+_supported_proto generic
+_supported_os Linux
+
+_make_test_img 4M
+
+echo "== Testing conversion with -n fails with no target file =="
+# check .orig file does not exist
+rm -f $TEST_IMG.orig
+if $QEMU_IMG convert -f $IMGFMT -O $IMGFMT -n $TEST_IMG $TEST_IMG.orig >/dev/null 2>&1; then
+    exit 1
+fi
+
+echo "== Testing conversion with -n succeeds with a target file =="
+rm -f $TEST_IMG.orig
+cp $TEST_IMG $TEST_IMG.orig
+if ! $QEMU_IMG convert -f $IMGFMT -O $IMGFMT -n $TEST_IMG $TEST_IMG.orig ; then
+    exit 1
+fi
+
+echo "== Testing conversion to raw is the same after conversion with -n =="
+# compare the raw files
+if ! $QEMU_IMG convert -f $IMGFMT -O raw $TEST_IMG $TEST_IMG.raw1 ; then
+    exit 1
+fi
+
+if ! $QEMU_IMG convert -f $IMGFMT -O raw $TEST_IMG.orig $TEST_IMG.raw2 ; then
+    exit 1
+fi
+
+if ! cmp $TEST_IMG.raw1 $TEST_IMG.raw2 ; then
+    exit 1
+fi
+
+echo "== Testing conversion back to original format =="
+if ! $QEMU_IMG convert -f raw -O $IMGFMT -n $TEST_IMG.raw2 $TEST_IMG ; then
+    exit 1
+fi
+_check_test_img
+
+echo "== Testing conversion to a smaller file fails =="
+rm -f $TEST_IMG.orig
+mv $TEST_IMG $TEST_IMG.orig
+_make_test_img 2M
+if $QEMU_IMG convert -f $IMGFMT -O $IMGFMT -n $TEST_IMG.orig $TEST_IMG >/dev/null 2>&1; then
+    exit 1
+fi
+
+rm -f $TEST_IMG.orig $TEST_IMG.raw $TEST_IMG.raw2
+
+echo "*** done"
+rm -f $seq.full
+status=0
+exit 0

tests/qemu-iotests/063.out

@@ -0,0 +1,10 @@
+QA output created by 063
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=4194304
+== Testing conversion with -n fails with no target file ==
+== Testing conversion with -n succeeds with a target file ==
+== Testing conversion to raw is the same after conversion with -n ==
+== Testing conversion back to original format ==
+No errors were found on the image.
+== Testing conversion to a smaller file fails ==
+Formatting 'TEST_DIR/t.IMGFMT', fmt=IMGFMT size=2097152
+*** done

tests/qemu-iotests/group

@@ -66,3 +66,4 @@
 059 rw auto
 060 rw auto
 062 rw auto
+063 rw auto