qemu-iotests: fix cleanup of background processes

Commit 934659c switched the iotests to run qemu and qemu-nbd from a bash
subshell, in order to catch segfaults.  Unfortunately, this means the
process PID cannot be captured via '$!'. We stopped killing qemu and
qemu-nbd processes, leaving a lot of orphaned, running qemu processes
after executing iotests.

Since the process is using exec in the subshell, the PID is the
same as the subshell PID.

Track these PIDs for cleanup using pidfiles in the $TEST_DIR. Only
track the qemu PID, however, if requested - not all usage requires
killing the process.

Reported-by: John Snow <jsnow@redhat.com>
Signed-off-by: Jeff Cody <jcody@redhat.com>
Message-id: 9e4f958b3895b7259b98d845bb46f000ba362869.1446232490.git.jcody@redhat.com
[mreitz@redhat.com: Replaced '! -z "..."' by '-n "..."']
Signed-off-by: Max Reitz <mreitz@redhat.com>

1 files changed, 8 insertions, 4 deletions

diff --git a/tests/qemu-iotests/058 b/tests/qemu-iotests/058
index f2bdd0b..63a6598 100755
--- a/tests/qemu-iotests/058
+++ b/tests/qemu-iotests/058
@@ -32,11 +32,17 @@ status=1	# failure is the default!
 
 nbd_unix_socket=$TEST_DIR/test_qemu_nbd_socket
 nbd_snapshot_img="nbd:unix:$nbd_unix_socket"
+rm -f "${TEST_DIR}/qemu-nbd.pid"
 
 _cleanup_nbd()
 {
-    if [ -n "$NBD_SNAPSHOT_PID" ]; then
-        kill "$NBD_SNAPSHOT_PID"
+    local NBD_SNAPSHOT_PID
+    if [ -f "${TEST_DIR}/qemu-nbd.pid" ]; then
+        read NBD_SNAPSHOT_PID < "${TEST_DIR}/qemu-nbd.pid"
+        rm -f "${TEST_DIR}/qemu-nbd.pid"
+        if [ -n "$NBD_SNAPSHOT_PID" ]; then
+            kill "$NBD_SNAPSHOT_PID"
+        fi
     fi
     rm -f "$nbd_unix_socket"
 }
@@ -60,7 +66,6 @@ _export_nbd_snapshot()
 {
     _cleanup_nbd
     $QEMU_NBD -v -t -k "$nbd_unix_socket" "$TEST_IMG" -l $1 &
-    NBD_SNAPSHOT_PID=$!
     _wait_for_nbd
 }
 
@@ -68,7 +73,6 @@ _export_nbd_snapshot1()
 {
     _cleanup_nbd
     $QEMU_NBD -v -t -k "$nbd_unix_socket" "$TEST_IMG" -l snapshot.name=$1 &
-    NBD_SNAPSHOT_PID=$!
     _wait_for_nbd
 }