On Tue, Apr 04, 2017 at 10:34:14PM +1000, Dave Chinner wrote: > On Mon, Apr 03, 2017 at 04:00:55PM +0200, Jan Kara wrote: > > What filesystems can or cannot easily do obviously differs. Ext4 has a > > recovery flag set in superblock on RW mount/remount and cleared on > > umount/RO remount. > > Even this doesn't help. A recent bug that was reported to the XFS > list - turns out that systemd can't remount-ro the root > filesystem sucessfully on shutdown because there are open write fds > on the root filesystem when it attempts the remount. So it just > reboots without a remount-ro. I'd certainly rather not invalidate caches on *every* boot. On the other hand, if the only cases involve the root filesystem, then from the point of view of NFS, we probably don't care much. > > This flag being set on mount would imply incrementing the crash > > counter. It should be pretty easy for each filesystem to implement > > such flag and the counter but I agree it requires an on-disk > > format change. > > Yup, anything we want that is persistent and consistent across > filesystems will need on-disk format changes. Hence we need a solid > specification first, not to mention tests to validate correct > behaviour across all filesystems in xfstests... For xfstests we'll need a way to get i_version (patch it into statx, I guess?). Ideally we'd have a way to test behavior across crashes too, any advice there? --b.
