mdmonitor closes mdstat fd if is empty

[Mariusz Tkaczyk]

There was a change in mdadm to fix issue when md_mod is reloaded (not a case for ubuntu because md_mod is build-in). Commit:
https://git.kernel.org/pub/scm/utils/mdadm/mdadm.git/commit/?id=52209d6ee1183581e148791cf6ee4d60a0193b1d

The fix prevents mdmonitor from occupying mdstat file descriptor in there is no any mddevice available.
As a side effect mdmonitor cannot react on md events because it is waiting in undefined resource (probably 1 which in demonize mode case is /dev/null).

When mdmonitor is started form command line and there was one mdmonitor already active, error message also is omitted, because error is thrown after forking. As a result, unexpectedly we may got same same issue after array creation.

[Mariusz Tkaczyk (mtkaczyk)]

Hello,
The main issue is in development, we need to deal with module reload and descriptor handling.

The second one can be easily workaround by using systemctl service (systemctl mdmonitor restart) instead of command line. Here error handling is needed instead of quiet fail.

I will notify if any fix will become available.

[Mariusz Tkaczyk (mtkaczyk)]

Hi,
Patches have been accepted upstream:
https://git.kernel.org/pub/scm/utils/mdadm/mdadm.git/commit/?id=e2308733910a157b0a4d4e78721f239d44b91a24
https://git.kernel.org/pub/scm/utils/mdadm/mdadm.git/commit/?id=cab9c67d461c65a1138359f9f6d39636466b90e4

[Mariusz Tkaczyk (mtkaczyk)]

Hi,
sorry copy-paste mistake, here the correct ones:
https://git.kernel.org/pub/scm/utils/mdadm/mdadm.git/commit/?id=e2308733910a157b0a4d4e78721f239d44b91a24
https://git.kernel.org/pub/scm/utils/mdadm/mdadm.git/commit/?id=007087d0898a045901e4e120296e6d9b845b20a6

[Jeff Lane  (bladernr)]

Just to check, is this resolved in 4.2-rc2?

[Launchpad Janitor (janitor)]

[Expired for mdadm (Ubuntu Impish) because there has been no activity for 60 days.]

[Launchpad Janitor (janitor)]

[Expired for mdadm (Ubuntu) because there has been no activity for 60 days.]