On Sun, Mar 04, 2012 at 06:14:39PM +0100, Olaf van der Spek wrote: > On 2-3-2012 14:12, Christoph Hellwig wrote: > >>I'd like to ask: > >>- Is there a tool to log all unsafe operations? > > > >What is an unsafe operation? Anything that's dumb and might lose data? > > For example > > >The possibilities are sheer endless. > > And? > > >>- What is the *right* way to update a file? > > > > fd = open(tmpfile, ...); > > write(fd, ...); // or any other update > > fdatasync(fd); > > rename(tmpfile, realfile); > > Argh, come on. > That's not real and it's not complete. tmpfile is undefined, errors > aren't handled and you have lots of unlisted assumptions or > regressions. The above is perfectly reasonable psuedo code for quickly describing how to safely overwriting a file. If you want to know about error handling and assumptions, read the man pages for operation. To make it easy for you, I'll just point out this has already been dealt with early in in the LWN thread for that article, here's the link to the comment and the relevant LWN article providing you with all the information you want: http://lwn.net/Articles/476606/ https://lwn.net/Articles/457667/ And that my stance on this atomic rename subject is simply this: If we want to change reanme behaviour, then the filesystem is not the right place to do it - atomic rename semantics need to be defined and enforced at the VFS. See here: http://lwn.net/Articles/479152/ This has all been hashed out before - we don't need to revisit this discussion here. If you want to solve the problem once and for all, submit patches to LKML to implement the new rename semantics in a new syscall.... Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
