On Thu, 05.03.15 21:39, Goffredo Baroncelli (kreij...@libero.it) wrote: > > Hi All, > the enclosed patches add an option to the journald.conf file to allow > a COW behavior for the journal files. > > The commit 11689d2a force the NOCOW flag of the journal files. This was > needed because systemd-journald has very poor performance when the > filesytem is BTRFS due to its the COW behavior. > > However removing the COW behavior, the journal file also lost the > btrfs checksum protection, and this disables the BTRFS capability to rebuild a > corrupted file  in a RAID filesystem. So this limits one of the biggest > benefit of BTRFS. > > This patch adds the option "CowJournal" to the journald.conf to disable/enable > the NOCOW flag for the journal file, allowing to revert to the old behavior. > > These patches are tagged as RFC, because I am not sure about the > naming of the option (now "CowJournal"). I ask some feedback.
I am pretty strongly against adding an explicit option for this. I consider this all a temporary stopgap, until btrfs's autodefrag makes the problem go away, and I am very conservative with adding new config options where it is already clear that they will eventually be useless. What I'd be open to is: a) beef up the tmpfiles logic to be able to do the equivalent of /usr/bin/chattr on files. (By adding a new line type, make "h" or so). b) remove all code that sets NOCOW explicitly on journal files from journald. c) instead ship a tmpfiles snippet making use of a) that sets the NOCOW flag for /var/lib/journal, which results in the flag being inherited by journal files that are created within it. If people then want to opt-out of NOCOW, they can simply override the tmpfiles snippet and all is good. That way we have a way to configure the bit, without actually introducing a high-level config option for this. Lennart -- Lennart Poettering, Red Hat _______________________________________________ systemd-devel mailing list email@example.com http://lists.freedesktop.org/mailman/listinfo/systemd-devel