[Qemu-block] [PATCH for-2.5?] qemu-iotests: Reduce racy output in 028

[Eric Blake]

On my machine, './check -qcow2 028' was failing about 80% of the
time, due to a race in how many times the repeated attempts
to run 'info block-jobs' could occur before the job was done,
showing up as a failure of fewer '(qemu) ' prompts than in the
expected output.  Silence the output during the repetitions, then
add a final clean command to keep the expected output useful;
once patched, I was finally able to run the test 20 times in a
row with no failures.

Signed-off-by: Eric Blake <address@hidden>
---

Not sure if this is the best fix, or if it is even appropriate
for inclusion in 2.5 this late in the game.

 tests/qemu-iotests/028     | 6 ++++--
 tests/qemu-iotests/028.out | 3 ---
 2 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/tests/qemu-iotests/028 b/tests/qemu-iotests/028
index a1f4423..756c335 100755
--- a/tests/qemu-iotests/028
+++ b/tests/qemu-iotests/028
@@ -111,10 +111,12 @@ h=$QEMU_HANDLE
 QEMU_COMM_TIMEOUT=1

 # Silence output since it contains the disk image path and QEMU's readline
-# character echoing makes it very hard to filter the output
+# character echoing makes it very hard to filter the output. Plus, there
+# is no telling how many times the command will repeat before succeeding.
 _send_qemu_cmd $h "drive_backup disk ${TEST_IMG}.copy" "(qemu)" >/dev/null
 _send_qemu_cmd $h "" "Formatting" | _filter_img_create
-qemu_cmd_repeat=20 _send_qemu_cmd $h "info block-jobs" "No active jobs"
+qemu_cmd_repeat=20 _send_qemu_cmd $h "info block-jobs" "No active jobs" 
>/dev/null
+_send_qemu_cmd $h "info block-jobs" "No active jobs"
 _send_qemu_cmd $h 'quit' ""

 # Base image sectors
diff --git a/tests/qemu-iotests/028.out b/tests/qemu-iotests/028.out
index 29c9972..e03452d 100644
--- a/tests/qemu-iotests/028.out
+++ b/tests/qemu-iotests/028.out
@@ -469,10 +469,7 @@ No errors were found on the image.
 block-backup

 Formatting 'TEST_DIR/t.IMGFMT.copy', fmt=IMGFMT size=4294968832 
backing_file=TEST_DIR/t.IMGFMT.base backing_fmt=IMGFMT
-(qemu)
 (qemu) iininfinfoinfo 
info binfo 
blinfo bloinfo 
blocinfo 
blockinfo 
block-info 
block-jinfo 
block-joinfo 
block-jobinfo block-jobs
-Type backup, device disk: Completed 0 of 4294968832 bytes, speed limit 0 
bytes/s
-iininfinfoinfo 
info binfo 
blinfo bloinfo 
blocinfo 
blockinfo 
block-info 
block-jinfo 
block-joinfo 
block-jobinfo block-jobs
 No active jobs
 === IO: pattern 195
 read 512/512 bytes at offset 3221194240
-- 
2.4.3