[PATCH v2.1 1/3] xfstests: btrfs: add functions to create dm-error device

[Anand Jain <anand.jain@oracle.com>]

From: Anand Jain <Anand.Jain@oracle.com>

Controlled EIO from the device is achieved using the dm device.
Helper functions are at common/dmerror.

Broadly steps will include calling _init_dmerror().
_init_dmerror() will use SCRATCH_DEV to create dm linear device and assign
DMERROR_DEV to /dev/mapper/error-test.

When test script is ready to get EIO, the test cases can call
_load_dmerror_table() which then it will load the dm error.
so that reading DMERROR_DEV will cause EIO. After the test case is
complete, cleanup must be done by calling _cleanup_dmerror().

Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
v2->v2.1: fixed missed typo error fixup in the commit.
v1->v2: accepts Dave Chinner's review comments, thanks

 common/dmerror | 69 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 common/rc      | 15 +++++++++++++
 2 files changed, 84 insertions(+)
 create mode 100644 common/dmerror

diff --git a/common/dmerror b/common/dmerror
new file mode 100644
index 0000000..f895d90
--- /dev/null
+++ b/common/dmerror
@@ -0,0 +1,69 @@
+##/bin/bash
+#
+# Copyright (c) 2015 Oracle.  All Rights Reserved.
+#
+# 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.
+#
+# This program is distributed in the hope that it would 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, write the Free Software Foundation,
+# Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+#
+#
+# common functions for setting up and tearing down a dmerror device
+
+_init_dmerror()
+{
+	$DMSETUP_PROG remove error-test > /dev/null 2>&1
+
+	local BLK_DEV_SIZE=`blockdev --getsz $SCRATCH_DEV`
+
+	DMERROR_DEV='/dev/mapper/error-test'
+
+	DMLINEAR_TABLE="0 $BLK_DEV_SIZE linear $SCRATCH_DEV 0"
+
+	$DMSETUP_PROG create error-test --table "$DMLINEAR_TABLE" || \
+		_fatal "failed to create dm linear device"
+
+	DMERROR_TABLE="0 $BLK_DEV_SIZE error $SCRATCH_DEV 0"
+}
+
+_scratch_mkfs_dmerror()
+{
+	$MKFS_BTRFS_PROG $* $DMERROR_DEV >> $seqres.full 2>&1 || \
+			_fatal "failed to create mkfs.btrfs $* $DMERROR_DEV"
+}
+
+_mount_dmerror()
+{
+	mount -t $FSTYP $MOUNT_OPTIONS $DMERROR_DEV $SCRATCH_MNT
+}
+
+_unmount_dmerror()
+{
+	$UMOUNT_PROGS $SCRATCH_MNT
+}
+
+_cleanup_dmerror()
+{
+	$UMOUNT_PROG $SCRATCH_MNT > /dev/null 2>&1
+	$DMSETUP_PROG remove error-test > /dev/null 2>&1
+}
+
+_load_dmerror_table()
+{
+	$DMSETUP_PROG suspend error-test
+	[ $? -ne 0 ] && _fatal  "failed to suspend error-test"
+
+	$DMSETUP_PROG load error-test --table "$DMERROR_TABLE"
+	[ $? -ne 0 ] && _fatal "failed to load error table error-test"
+
+	$DMSETUP_PROG resume error-test
+	[ $? -ne 0 ] && _fatal  "failed to resume error-test"
+}
diff --git a/common/rc b/common/rc
index c5db0dd..447ab7f 100644
--- a/common/rc
+++ b/common/rc
@@ -1305,6 +1305,21 @@ _require_block_device()
 	fi
 }
 
+# this test requires the device mapper error target
+#
+_require_dmerror()
+{
+    _require_command "$DMSETUP_PROG" dmsetup
+
+    $DMSETUP_PROG targets | grep error >/dev/null 2>&1
+    if [ $? -eq 0 ]
+    then
+	:
+    else
+	_notrun "This test requires dm error support"
+    fi
+}
+
 # this test requires the device mapper flakey target
 #
 _require_dm_flakey()
-- 
2.0.0.153.g79dcccc