On Mon, Jul 01, 2024 at 06:26:36AM -0400, Jeff Layton wrote: > This set is essentially unchanged from the last one, aside from the > new file in Documentation/. I had a review comment from Andi Kleen > suggesting that the ctime_floor should be per time_namespace, but I > think that's incorrect as the realtime clock is not namespaced. > > At LSF/MM this year, we had a discussion about the inode change > attribute. At the time I mentioned that I thought I could salvage the > multigrain timestamp work that had to be reverted last year [1]. That > version had to be reverted because it was possible for a file to get a > coarse grained timestamp that appeared to be earlier than another file > that had recently gotten a fine-grained stamp. > > This version corrects the problem by establishing a per-time_namespace > ctime_floor value that should prevent this from occurring. In the above > situation that was problematic before, the two files might end up with > the same timestamp value, but they won't appear to have been modified in > the wrong order. > > That problem was discovered by the test-stat-time gnulib test. Note that > that test still fails on multigrain timestamps, but that's because its > method of determining the minimum delay that will show a timestamp > change will no longer work with multigrain timestamps. I have a patch to > change the testcase to use a different method that I've posted to the > bug-gnulib mailing list. > > The big question with this set is whether the performance will be > suitable. The testing I've done seems to show performance parity with > multigrain timestamps enabled, but it's hard to rule this out regressing > some workload. > > This set is based on top of Christian's vfs.misc branch (which has the > earlier change to track inode timestamps as discrete integers). If there > are no major objections, I'd like to let this soak in linux-next for a > bit to see if any problems shake out. > > [1]: https://lore.kernel.org/linux-fsdevel/20230807-mgctime-v7-0-d1dec143a704@xxxxxxxxxx/ > > Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx> I have a few nits that need to be addressed, but you can add Reviewed-by: Josef Bacik <josef@xxxxxxxxxxxxxx> to the series once they're addressed. Thanks, Josef
