map-unmap.sh: use udevadm settle for synchronization

This script was heuristically using short sleep commands in order to
give udev activity time to complete.

There's a command "udevadm settle" which actually looks at the udev
queue and waits until its processing is done.  Much, much better.

This rearranges the get_id function a bit too, breaking it into one
function that gets the id and another that loops back and tries
again after a short delay in the event the get_id fails.

Signed-off-by: Alex Elder <elder@inktank.com>

diff --git a/qa/workunits/rbd/map-unmap.sh b/qa/workunits/rbd/map-unmap.sh
index 417f95580bfb9ceb8e7adb85b56ee24b2c1cd485..341a0be081c46dfb2ef721810afc2def378db55d 100755 (executable)
--- a/qa/workunits/rbd/map-unmap.sh
+++ b/qa/workunits/rbd/map-unmap.sh
@@ -10,8 +10,6 @@ IMAGE_SIZE="1024"     # MB
 ID_TIMEOUT="10"                # seconds to wait to get rbd id after mapping
 ID_DELAY=".1"          # floating-point seconds to delay before rescan
 
-MAP_DELAY=".25"                # floating-point seconds to delay before unmap
-
 function get_time() {
        date '+%s'
 }
@@ -22,26 +20,34 @@ function times_up() {
        test $(get_time) -ge "${end_time}"
 }
 
-function get_id() {
+function _get_id() {
        [ $# -eq 1 ] || exit 99
        local image_name="$1"
        local id=""
-       local end_time=$(expr $(get_time) + ${ID_TIMEOUT})
 
        cd /sys/bus/rbd/devices
-
-       while [ -z "${id}" ]; do
-               if times_up "${end_time}"; then
-                       break;
+       for i in *; do
+               if [ "$(cat $i/name)" = "${image_name}" ]; then
+                       id="$i"
+                       break
                fi
-               for i in *; do
-                       if [ "$(cat $i/name)" = "${image_name}" ]; then
-                               id=$i
-                               break
-                       fi
-               done
+       done
+       cd - >/dev/null
+
+       echo $id
+       test -n "${id}"         # return code 0 if id was found
+}
+function get_id() {
+       [ $# -eq 1 ] || exit 99
+       local image_name="$1"
+       local id=""
+       local end_time=$(expr $(get_time) + ${ID_TIMEOUT})
+
+       while ! id=$(_get_id "${image_name}") && ! times_up "${end_time}"; do
+               echo "get_id: image not mapped; trying again after delay" >&2
                sleep "${ID_DELAY}"
        done
+
        echo $id
        test -n "${id}"         # return code 0 if id was found
 }
@@ -51,11 +57,12 @@ function map_unmap() {
        local image_name="$1"
 
        rbd map "${image_name}"
-       RBD_ID=$(get_id "${image_name}")
+       udevadm settle
 
-       sleep "${MAP_DELAY}"
+       RBD_ID=$(get_id "${image_name}")
 
        rbd unmap "/dev/rbd${RBD_ID}"
+       udevadm settle
 }
 
 function setup() {