systemd journal interaction with btrfs, unfixable corruption

[Michal Schmidt]

On 09/25/2013 06:35 AM, Chris Murphy wrote:
> There are some reports of VM images on btrfs being corrupted somehow
> (although I don't think it's related to balance, I could be wrong),
> and the solution is to set VM images to nodatacow.  So I wonder if
> there's some behavior of systemd journaling that's similar?

I don't know about VM images, but systemd-journald writes to journal
files using a bunch of writable mmap windows. It also calls ftruncate to
truncate a journal file to its current size, just to trigger inotify
clients that are watching for changes in the file. Sometimes it calls
fsync.

Michal