On Fri, 09 Sep 2022, NeilBrown wrote: > On Fri, 09 Sep 2022, Trond Myklebust wrote: > > > > > IOW: the minimal condition needs to be that for all cases below, the > > application reads 'state B' as having occurred if any data was > > committed to disk before the crash. > > > > Application Filesystem > > =========== ========= > > read change attr <- 'state A' > > read data <- 'state A' > > write data -> 'state B' > > <crash>+<reboot> > > read change attr <- 'state B' > > The important thing here is to not see 'state A'. Seeing 'state C' > should be acceptable. Worst case we could merge in wall-clock time of > system boot, but the filesystem should be able to be more helpful than > that. > Actually, without the crash+reboot it would still be acceptable to see "state A" at the end there - but preferably not for long. >From the NFS perspective, the changeid needs to update by the time of a close or unlock (so it is visible to open or lock), but before that it is just best-effort. NeilBrown
