common: add _require_block_device() helper

Add _require_block_device() helper and use it in _require_dm_flakey()
and generic/076.

_require_dm_flakey() assumes $SCRATCH_DEV is a block device, now it can
also be a NFS export.

generic/076 does "cat $SCRATCH_DEV" which will fail when testing on NFS.

Signed-off-by: Eryu Guan <eguan@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>

common/rc

@@ -1247,10 +1247,25 @@ _require_command()
     [ -n "$1" -a -x "$1" ] || _notrun "$_cmd utility required, skipped this test"
 }
 
+# this test requires the device to be valid block device
+# $1 - device
+_require_block_device()
+{
+	if [ -z "$1" ]; then
+		echo "Usage: _require_block_device <dev>" 1>&2
+		exit 1
+	fi
+	if [ "`_is_block_dev $SCRATCH_DEV`" == "" ]; then
+		_notrun "require $1 to be valid block disk"
+	fi
+}
+
 # this test requires the device mapper flakey target
 #
 _require_dm_flakey()
 {
+    # require SCRATCH_DEV to be a valid block device
+    _require_block_device $SCRATCH_DEV
     _require_command $DMSETUP_PROG
 
     modprobe dm-flakey >/dev/null 2>&1

tests/generic/076

@@ -56,6 +56,7 @@ _supported_fs generic
 _supported_os IRIX Linux
 
 _require_scratch
+_require_block_device $SCRATCH_DEV
 
 echo "*** init fs"