On Mon, Mar 04, 2019 at 05:04:23PM +0200, Amir Goldstein wrote: > On Mon, Mar 4, 2019 at 4:44 PM <fdmanana@xxxxxxxxxx> wrote: > > > > From: Filipe Manana <fdmanana@xxxxxxxx> > > > > Test that if we truncate a file to reduce its size, rename it and then > > fsync it, after a power failure the file has a correct size and name. > > > > I am not sure that ext4/xfs semantics guaranty anything about > persisting file name after fsync of file?... They do. It's that pesky "strictly ordered metadata" thing I keep having to explain to people... i.e. if you fsync an inode, then you are persisting all the changes needed to reference that file and it's data. And so if there was a rename in the history of that file, then that is persisted, too. Which means that both the original and the new directory modifications are persisted, too. *POSIX* doesn't require this - it says that if you O_DSYNC data, then it also includes all the metadata needed to reference that data. So even if the data is there, POSIX doesn't define whether the rename is there or noti, just that you can get to the fsync'd data via either the old or new name. IOWs, POSIX allows the behaviour to be implementation specific. In this case, file systems with strictly ordered metadata will end up making the rename visible because the rename occurred before the truncate that the fsync() is persisting... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx
