qemu-iotests: 026: Reduce output changes for cache=none qcow2

qemu-iotests supports the -nocache option which makes the tests run with
cache=none. For blkdebug tests with qcow2 this means that we may see
test results that differ from cache=writethrough. This patch makes the
diff a bit smaller and therefore easier to review.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>

tests/qemu-iotests/026

@@ -87,6 +87,12 @@ _make_test_img 1G
 
 echo
 echo "Event: $event; errno: $errno; imm: $imm; once: $once; write $vmstate"
+
+# We want to catch a simple L2 update, not the allocation of the first L2 table
+if [ "$event" == "l2_update" ]; then
+    $QEMU_IO -c "write $vmstate 0 512" $TEST_IMG > /dev/null 2>&1
+fi
+
 $QEMU_IO -c "write $vmstate 0 128k " $BLKDBG_TEST_IMG | _filter_qemu_io
 
 # l2_load is not called on allocation, so issue a second write

tests/qemu-iotests/check

@@ -243,7 +243,7 @@ do
 		echo " - no qualified output"
 		err=true
 	    else
-		if diff $seq.out $tmp.out >/dev/null 2>&1
+		if diff -w $seq.out $tmp.out >/dev/null 2>&1
 		then
 		    echo ""
 		    if $err
@@ -255,7 +255,7 @@ do
 		else
 		    echo " - output mismatch (see $seq.out.bad)"
 		    mv $tmp.out $seq.out.bad
-		    $diff $seq.out $seq.out.bad
+		    $diff -w $seq.out $seq.out.bad
 		    err=true
 		fi
 	    fi