On Wed, Dec 20, 2017 at 03:11:48PM +0800, Fu.Lin wrote: > Hi, > > Currently the lock manager infrastructure has implementation of nop, sanlock > and lockd. The first do nothing, while sanlock and lockd all requires the > share > stroage, and lockd is not provided fence mechanism, sanlock would force to > restart OS when stopping daemon. > > The first half of 2017, QEMU introduced the `share-rw` and `file.locking` to > handle a problem: https://bugzilla.redhat.com/show_bug.cgi?id=1080152 , > someone > said: > > There is also scope for creating new plugins for libvirt to use other > mechanism if someone comes up with other ideas. > > So what about dlm-corosync? > > DLM(distributed lock manage) is implemented by kernel, it provides some > userspace > API by "libdlm" to lock/unlock resource, using these API need a daemon named > dlm_controld. "Corosync" is cluster messager layer using TCP or UDP, > responsible > for members management in cluster. dlm_controld and corosync are formed a > kind of > lock which could be used in cluster. And there is another component named > "sbd" > providing fence mechanism, it's not necessary, `dlm_controld -f 0` would > disable it. I don't have any direct experiance with DLM - just aware of it as a concept. I think it can be considered in scope for a libvirt lock manager plugin if you want to try writnig one. > As for implement, I think we could make use of virtlockd daemon, just add > some RPC callback in micro-on. How are locks acquired by libdlm scoped ? The reason we have virtlockd is that the fcntl() locks need to be held by a running process, and we wanted them to persist across libvirtd restarts. This required holding them in a separate process. Are libdlm locks automatically released when the process that acquired them dies, or is a manual release action required ? If they always require a manual release, then there would be no need to use virtlockd - the plugin can just take care of acquire & release, and still cope with lbivirtd restarts. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :| -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list
