iotests: add O_DIRECT alignment probing test

This test case checks that image files can be opened even if I/O
produces EIO errors.  QEMU should not refuse opening failed disks since
the guest may be configured for multipath I/O where accessing failed
disks is expected.
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

tests/qemu-iotests/128

+#!/bin/bash
+#
+# Test that opening O_DIRECT succeeds when image file I/O produces EIO
+#
+# Copyright (C) 2015 Red Hat, Inc.
+#
+# 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=stefanha@redhat.com
+
+seq=`basename $0`
+echo "QA output created by $seq"
+
+here=`pwd`
+tmp=/tmp/$$
+status=1	# failure is the default!
+
+devname="eiodev$$"
+
+_setup_eiodev()
+{
+	# This test should either be run as root or with passwordless sudo
+	for cmd in "" "sudo -n"; do
+		echo "0 $((1024 * 1024 * 1024 / 512)) error" | \
+			$cmd dmsetup create "$devname" 2>/dev/null
+		if [ "$?" -eq 0 ]; then
+			return
+		fi
+	done
+	_notrun "root privileges required to run dmsetup"
+}
+
+_cleanup_eiodev()
+{
+	for cmd in "" "sudo -n"; do
+		$cmd dmsetup remove "$devname" 2>/dev/null
+		if [ "$?" -eq 0 ]; then
+			return
+		fi
+	done
+}
+
+_cleanup()
+{
+	_cleanup_eiodev
+}
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+# get standard environment, filters and checks
+. ./common.rc
+. ./common.filter
+
+_supported_fmt raw
+_supported_proto file
+_supported_os Linux
+
+_setup_eiodev
+
+TEST_IMG="/dev/mapper/$devname"
+
+echo
+echo "== reading from error device =="
+# Opening image should succeed but the read operation should fail
+$QEMU_IO --format "$IMGFMT" --nocache -c "read 0 65536" "$TEST_IMG" | _filter_qemu_io
+
+# success, all done
+echo "*** done"
+rm -f $seq.full
+status=0

tests/qemu-iotests/128.out

+QA output created by 128
+
+== reading from error device ==
+read failed: Input/output error
+*** done

tests/qemu-iotests/group

@@ -121,3 +121,4 @@
 114 rw auto quick
 116 rw auto quick
 123 rw auto quick
+128 rw auto quick