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>

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
 }
 

tests/qemu-iotests/common.config

@@ -44,6 +44,8 @@ export HOST_OPTIONS=${HOST_OPTIONS:=local.config}
 export CHECK_OPTIONS=${CHECK_OPTIONS:="-g auto"}
 export PWD=`pwd`
 
+export _QEMU_HANDLE=0
+
 # $1 = prog to look for, $2* = default pathnames if not found in $PATH
 set_prog_path()
 {
@@ -105,7 +107,12 @@ fi
 
 _qemu_wrapper()
 {
-    (exec "$QEMU_PROG" $QEMU_OPTIONS "$@")
+    (
+        if [ -n "${QEMU_NEED_PID}" ]; then
+            echo $BASHPID > "${TEST_DIR}/qemu-${_QEMU_HANDLE}.pid"
+        fi
+        exec "$QEMU_PROG" $QEMU_OPTIONS "$@"
+    )
 }
 
 _qemu_img_wrapper()
@@ -120,7 +127,10 @@ _qemu_io_wrapper()
 
 _qemu_nbd_wrapper()
 {
-    (exec "$QEMU_NBD_PROG" $QEMU_NBD_OPTIONS "$@")
+    (
+        echo $BASHPID > "${TEST_DIR}/qemu-nbd.pid"
+        exec "$QEMU_NBD_PROG" $QEMU_NBD_OPTIONS "$@"
+    )
 }
 
 export QEMU=_qemu_wrapper

tests/qemu-iotests/common.qemu

@@ -30,8 +30,6 @@ QEMU_COMM_TIMEOUT=10
 QEMU_FIFO_IN="${TEST_DIR}/qmp-in-$$"
 QEMU_FIFO_OUT="${TEST_DIR}/qmp-out-$$"
 
-QEMU_PID=
-_QEMU_HANDLE=0
 QEMU_HANDLE=0
 
 # If bash version is >= 4.1, these will be overwritten and dynamic
@@ -153,11 +151,11 @@ function _launch_qemu()
     mkfifo "${fifo_out}"
     mkfifo "${fifo_in}"
 
+    QEMU_NEED_PID='y'\
     ${QEMU} -nographic -serial none ${comm} -machine accel=qtest "${@}" \
                                                                 >"${fifo_out}" \
                                                                 2>&1 \
                                                                 <"${fifo_in}" &
-    QEMU_PID[${_QEMU_HANDLE}]=$!
 
     if [[ "${BASH_VERSINFO[0]}" -ge "5" ||
         ("${BASH_VERSINFO[0]}" -ge "4"  &&  "${BASH_VERSINFO[1]}" -ge "1") ]]
@@ -196,10 +194,18 @@ function _cleanup_qemu()
     # QEMU_PID[], QEMU_IN[], QEMU_OUT[] all use same indices
     for i in "${!QEMU_OUT[@]}"
     do
-        if [ -z "${wait}" ]; then
-            kill -KILL ${QEMU_PID[$i]} 2>/dev/null
+        local QEMU_PID
+        if [ -f "${TEST_DIR}/qemu-${i}.pid" ]; then
+            read QEMU_PID < "${TEST_DIR}/qemu-${i}.pid"
+            rm -f "${TEST_DIR}/qemu-${i}.pid"
+            if [ -z "${wait}" ] && [ -n "${QEMU_PID}" ]; then
+                kill -KILL ${QEMU_PID} 2>/dev/null
+            fi
+            if [ -n "${QEMU_PID}" ]; then
+                wait ${QEMU_PID} 2>/dev/null # silent kill
+            fi
         fi
-        wait ${QEMU_PID[$i]} 2>/dev/null # silent kill
+
         if [ -n "${wait}" ]; then
             cat <&${QEMU_OUT[$i]} | _filter_testdir | _filter_qemu \
                                   | _filter_qemu_io | _filter_qmp

tests/qemu-iotests/common.rc

@@ -154,7 +154,6 @@ _make_test_img()
     # Start an NBD server on the image file, which is what we'll be talking to
     if [ $IMGPROTO = "nbd" ]; then
         eval "$QEMU_NBD -v -t -b 127.0.0.1 -p 10810 -f $IMGFMT  $TEST_IMG_FILE &"
-        QEMU_NBD_PID=$!
         sleep 1 # FIXME: qemu-nbd needs to be listening before we continue
     fi
 }
@@ -175,8 +174,11 @@ _cleanup_test_img()
     case "$IMGPROTO" in
 
         nbd)
-            if [ -n "$QEMU_NBD_PID" ]; then
-                kill $QEMU_NBD_PID
+            if [ -f "${TEST_DIR}/qemu-nbd.pid" ]; then
+                local QEMU_NBD_PID
+                read QEMU_NBD_PID < "${TEST_DIR}/qemu-nbd.pid"
+                kill ${QEMU_NBD_PID}
+                rm -f "${TEST_DIR}/qemu-nbd.pid"
             fi
             rm -f "$TEST_IMG_FILE"
             ;;