On Tue, Aug 17, 2010 at 12:04 PM, J. Bruce Fields <bfields@xxxxxxxxxxxx> wrote: > > Right, I think that we probably have to give up ext3 as a lost cause. > But perhaps we could get away with a hack like this on filesystems that > can store nanoseconds. I do not think so. The problem with "increment mtime by a nanosecond when necessary" is that timestamps can wind up out of order. As in: 1) Do a bunch of operations on file A 2) Do one operation on file B Imagine each operation on A incrementing its timestamp by a nanosecond "just because". If all of these operations happen in less than 4 ms, you can wind up with the timestamp on B being EARLIER than the timestamp on A. That is a big no-no (think "make" or anything else relying on timestamps for relative times). If you can prove that the last modification on B happens after the last modification on A, then it is very bad for the mtime on B to be earlier than the mtime on A. I guarantee that will break things in the real world. As you say, high-resolution timestamps "will extend the useful lifetime of NFSv3 by quite a bit". They are also a good idea in principle, IMO. Correctness is almost always more important than performance. - Pat -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
