Mdmonitor: Improve udev event handling

Mdmonitor is waiting for udev queue to become empty.
Even if the queue becomes empty, udev might still be processing last event.
However we want to wait and wake up mdmonitor when udev finished
processing events..

Also, the udev queue interface is considered legacy and should not be
used outside of udev.

Use udev monitor instead, and wake up mdmonitor on every event triggered
by udev for md block device.

We need to generate more change events from kernel, because they are
missing in some situations, for example, when rebuild started.
This will be addressed in a separate patch.

Move udev specific code into separate functions, and place them in udev.c file.
Also move use_udev() logic from lib.c into newly created file.

Signed-off-by: Mateusz Grzonka <mateusz.grzonka@intel.com>
Signed-off-by: Kinga Tanska <kinga.tanska@intel.com>
Signed-off-by: Jes Sorensen <jes@trained-monkey.org>

1 files changed, 37 insertions, 0 deletions

diff --git a/udev.h b/udev.h
new file mode 100644
index 00000000..33884861
--- /dev/null
+++ b/udev.h
@@ -0,0 +1,37 @@
+/*
+ * mdadm - manage Linux "md" devices aka RAID arrays.
+ *
+ * Copyright (C) 2022 Mateusz Grzonka <mateusz.grzonka@intel.com>
+ *
+ *    This program is free software; you can redistribute it and/or modify
+ *    it under the terms of the GNU General Public License as published by
+ *    the Free Software Foundation; either version 2 of the License, or
+ *    (at your option) any later version.
+ *
+ *    This program is distributed in the hope that it will be useful,
+ *    but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *    GNU General Public License for more details.
+ *
+ *    You should have received a copy of the GNU General Public License
+ *    along with this program; if not, write to the Free Software
+ *    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+#ifndef MONITOR_UDEV_H
+#define MONITOR_UDEV_H
+
+enum udev_status {
+	UDEV_STATUS_ERROR_NO_UDEV = -2,
+	UDEV_STATUS_ERROR,
+	UDEV_STATUS_SUCCESS = 0,
+	UDEV_STATUS_TIMEOUT
+};
+
+bool udev_is_available(void);
+
+#ifndef NO_LIBUDEV
+enum udev_status udev_wait_for_events(int seconds);
+#endif
+
+#endif