On Mon, 10.04.17 16:14, Michael Chapman (m...@very.puzzling.org) wrote: > On Mon, 10 Apr 2017, Chris Murphy wrote: > > On Sun, Apr 9, 2017 at 5:17 AM, Lennart Poettering > > <lenn...@poettering.net> wrote: > > > > > That said, are you sure FIFREEZE is really what we want there? it > > > appears to also pause any further writes to disk (until FITHAW is > > > called). > > > > > So, I am still puzzled why the file system people think that "sync()" > > > isn't supposed to actually sync things to disk... > > > > https://www.spinics.net/lists/linux-xfs/msg05113.html > > Ah good, Dave actually suggests using a freeze there. A freeze without a > corresponding thaw should be OK if it's definitely after all processes have > been killed, since we're just about to reboot anyway. (Obviously we'd want > to avoid the whole lot when running in a container or when doing > kexec.)
No, there is no such guarantee. We support initrds that run userspace stuff from the initrd at boot, that stays around in the background is only killed after we transition back into the initrd. And we really don't control what they do, they can do anything they like, access any file they want at any time. We added this primarily to support storage services backing the root file system (think iscsid, nbd, ...), but it actually can be anything that hsa the "feel" of a kernel component in being around since the time before systemd initialiazes until after the time it shut down again, but is actually implemented in userspace. In fact, this is precisely what plymouth is making use of: by marking a process with argv[0][0] = '@' we permit any privileged process to be excluded from the final killing spree, so that it will survive until the initrd shutdown transition. So no, "freeze" is not an option. That sounds like a recipe to make shutdown hang. We need a sync() that actually does what is documented and sync the file system properly. Lennart -- Lennart Poettering, Red Hat _______________________________________________ systemd-devel mailing list systemd-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/systemd-devel
