c654b8a9cb
ext4 supports a real NFSv4 change attribute, which is bumped whenever the ctime would be updated, including times when two updates arrive within a jiffy of each other. (Note that although ext4 has space for nanosecond-precision ctime, the real resolution is lower: it actually uses jiffies as the time-source.) This ensures clients will invalidate their caches when they need to. There is some fear that keeping the i_version up-to-date could have performance drawbacks, so for now it's turned on only by a mount option. We hope to do something better eventually. Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu> Cc: Theodore Tso <tytso@mit.edu>