TEST-17-UDEV: fix the device watch test

- Match the watch rules against the root block device's kernel name instead
  of a hard-coded 'sda', which is not portable (e.g. 'vda' on virtio).
- The nowatch check used 'test ! -e', but the watch symlinks form a
  bidirectional (circular) pair (ID -> wd -> ID), so dereferencing them with
  -e always fails with ELOOP and 'test ! -e' always succeeds, regardless of
  whether the watch is still present. Use '(! test -L ...)', which does not
  dereference the symlink.
- Drop never worked checks for the 1st and 2nd invocations.
- Drop unnecessary 'function' keyword.
- Drop unnecessary 00-debug.rules.
- Fix broken drop-in config file.
- Restart udevd after the drop-in config file.
- Trigger block devices after rules change to restore the original watches.
- Also verify that the device's inode is listed in the inotify fd's fdinfo.

(cherry picked from commit 8bcd2c8ee03b16ed84b5f5554c02a3bf2e900587)

test/units/TEST-17-UDEV.watch.sh

@@ -8,7 +8,7 @@ set -o pipefail
 # shellcheck source=test/units/util.sh
 . "$(dirname "$0")"/util.sh
 
-function check_validity() {
+check_validity() {
     local f ID_OR_HANDLE
 
     for f in /run/udev/watch/*; do
@@ -22,7 +22,7 @@ function check_validity() {
     done
 }
 
-function check() {
+check() {
     for _ in {1..2}; do
         systemctl reset-failed systemd-udevd.service
         systemctl restart systemd-udevd.service
@@ -52,32 +52,56 @@ function check() {
     done
 }
 
-# Check if the first invocation (should be in initrd) pushed the inotify fd to fdstore,
-# and the next invocation gained the fd from service manager.
-# TNote the service may be started without generating debugging logs. Let's check failure log.
-if ! journalctl -n 1 -q -u systemd-udevd.service --invocation=1 --grep 'Pushed inotify fd to service manager.'; then
-    assert_eq "$(journalctl -n 1 -q -u systemd-udevd.service --invocation=1 --grep 'Failed to push inotify fd to service manager.' || :)" ""
-fi
-if ! journalctl -n 1 -q -u systemd-udevd.service --invocation=2 --grep 'Received inotify fd \(\d+\) from service manager.'; then
-    assert_eq "$(journalctl -n 1 -q -u systemd-udevd.service --invocation=2 --grep 'Pushed inotify fd to service manager.' || :)" ""
-fi
+udevd_inotify_fdinfo() {
+    local pid fd
+
+    # Print the path of systemd-udevd's inotify group fdinfo.
+
+    pid="$(systemctl show --property MainPID --value systemd-udevd.service)"
+    [[ "${pid:-0}" -gt 0 ]] || return 1
+
+    for fd in /proc/"$pid"/fd/*; do
+        if [[ "$(readlink "$fd" 2>/dev/null)" == "anon_inode:inotify" ]]; then
+            echo "/proc/$pid/fdinfo/${fd##*/}"
+            return 0
+        fi
+    done
+
+    return 1
+}
+
+device_is_watched() {
+    local devnode="${1:?}"
+    local ino fdinfo
+
+    fdinfo="$(udevd_inotify_fdinfo)" || exit 1
+    ino="$(printf '%x' "$(stat -c '%i' "$devnode")")"
+    grep -qE "^inotify wd:[0-9a-f]+ ino:${ino} " "$fdinfo"
+}
+
+device_is_watched_by_link() {
+    local devnode="${1:?}"
+    local id
+
+    id="$(udevadm info "$devnode" | awk '$1 == "J:" { print $2 }')"
+    test -L "/run/udev/watch/${id}"
+}
 
 mkdir -p /run/systemd/system/systemd-udevd.service.d/
 cat >/run/systemd/system/systemd-udevd.service.d/10-debug.conf <<EOF
 [Service]
-SYSTEMD_LOG_LEVEL=debug
+Environment=SYSTEMD_LOG_LEVEL=debug
 EOF
 
 systemctl daemon-reload
 
 mkdir -p /run/udev/rules.d/
 
-cat >/run/udev/rules.d/00-debug.rules <<EOF
-SUBSYSTEM=="block", KERNEL=="sda*", OPTIONS="log_level=debug"
-EOF
+ROOTDEV="$(bootctl -RR)"
+ROOTDEV_NAME="$(udevadm info --query=name "$ROOTDEV")"
 
-cat >/run/udev/rules.d/50-testsuite.rules <<EOF
-ACTION=="add", SUBSYSTEM=="block", KERNEL=="sda", OPTIONS:="watch"
+cat >/run/udev/rules.d/99-testsuite.rules <<EOF
+ACTION=="add", SUBSYSTEM=="block", KERNEL=="${ROOTDEV_NAME}", OPTIONS:="watch"
 EOF
 
 # Unfortunately, journalctl --invocation= is unstable when debug logging is enabled on service manager.
@@ -86,28 +110,25 @@ systemctl log-level info
 
 check
 
-ROOTDEV="$(bootctl -RR)"
+device_is_watched "$ROOTDEV"
+device_is_watched_by_link "$ROOTDEV"
 
-MAJOR="$(udevadm info "$ROOTDEV" | grep -e '^E: MAJOR=' | sed -e 's/^E: MAJOR=//')"
-MINOR="$(udevadm info "$ROOTDEV" | grep -e '^E: MINOR=' | sed -e 's/^E: MINOR=//')"
-test -L "/run/udev/watch/b${MAJOR}:${MINOR}"
-
-cat >/run/udev/rules.d/50-testsuite.rules <<EOF
-ACTION=="change", SUBSYSTEM=="block", KERNEL=="sda", OPTIONS:="nowatch"
+cat >/run/udev/rules.d/99-testsuite.rules <<EOF
+ACTION=="change", SUBSYSTEM=="block", KERNEL=="${ROOTDEV_NAME}", OPTIONS:="nowatch"
 EOF
 
 check
 
-MAJOR="$(udevadm info "$ROOTDEV" | grep -e '^E: MAJOR=' | sed -e 's/^E: MAJOR=//')"
-MINOR="$(udevadm info "$ROOTDEV" | grep -e '^E: MINOR=' | sed -e 's/^E: MINOR=//')"
-test ! -e "/run/udev/watch/b${MAJOR}:${MINOR}"
+(! device_is_watched "$ROOTDEV")
+(! device_is_watched_by_link "$ROOTDEV")
 
-rm /run/udev/rules.d/00-debug.rules
-rm /run/udev/rules.d/50-testsuite.rules
-udevadm control --reload
+rm /run/udev/rules.d/99-testsuite.rules
 
 rm -f /run/systemd/system/systemd-udevd.service.d/10-debug.conf
 systemctl daemon-reload
+systemctl restart systemd-udevd.service
+
+udevadm trigger -w --action change --subsystem-match=block
 
 systemctl log-level "$SAVED_LOG_LEVEL"