On Tue, Feb 8, 2011 at 9:28 AM, Lennart Poettering <lennart@xxxxxxxxxxxxxx> wrote: > On Tue, 08.02.11 16:54, Andrey Borzenkov (arvidjaar@xxxxxxx) wrote: > >> >> a) mdmon is perfectly capable of restarting, it is already used to >> >> take over mdmon launched in initrd. The problem is to know when to >> >> restart - i.e. when respective libraries are changed. This is a job >> >> for package management in distribution. It is already employed for >> >> glibc, systemd and some others and can just as well be employed for >> >> mdmon. And this is totally unrelated to systemd :) >> > >> > Really, you are sying there is a synchronous way to make mdmon reexec >> > itself? How does that work? >> > >> >> I am not sure whether it qualifies as synchronous, but "mdmon >> --takeover" will kill any existing mdmon for this and start monitoring >> itself. > > I wonder if this is really fully synchronous, i.e. that a) there is no > point in time where mdmon is not running during this restart and b) the > mdmom --takeover command returns when the new daemon is fully up, and > not right-away. > >> > Well, the root file systems cannot be unmounted, only remounted. >> > >> > So, is there a way to invoke mdmon so that it flushes all metadata >> > changes to disk and immediately terminates then this should be all we >> > need for a clean solution. We'd then shutdown the normal instances of >> > mdmon down like any other daemon and simply invoke this metadata >> > flushing command as part of late shutdown. >> >> >> Hmm ... it looks like you just need to >> >> start mdmon >> do mdadm --wait-clean >> >> After this you can kill mdmon again (assuming decide is no more in >> use). > > > Well, it would be nice if the md utils would offer something doing this > without spawning multiple processes and killing them again. > /me wonders why his raid5 resyncs every boot on Fedora 15 and has found this old thread. I'm tempted to: 1/ teach ignore_proc() to scan for pid files in /dev/md/ (MDMON_DIR on Fedora) 2/ arrange for mdadm --wait-clean --scan to be called after all filesytems have been mounted read only ...but a few things strike me. This does not seem to be what was being proposed above. Systemd does not treat dm devices like a service and takes care to shut them down explicitly (but in that case there is an api that it can call). Is it time for a libmd.so, so systemd can invoke the "--wait-clean --scan" process itself? Probably simpler to just SIGTERM mdmon and wait for it. -- Dan -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
