On Wed, Jul 16, 2014 at 12:38 PM, J. Bruce Fields <bfields@xxxxxxxxxxxx> wrote: > As of (a backport of) 3a1556e8662 "NFSv2/v3: Simulate the change > attribute" we have a user complaining about chmod on the client > invalidating data caches. (They have some sort of pipeline running on > the client where output from one stage is has ownership and permissions, > but not data, change before being used as input to the next.) > > Looks like that's expected? Yes, that's expected. There is a tradeoff here: we could either use the ctime, in which case there is the problem of false negative cache revalidations (in cases such as the above), or we could use the mtime, which has a problem of false positive cache revalidations (after an application deliberately sets the mtime value). The choice fell on ctime because that's what was being used for NFSv4 and, because false positive revalidations can lead to data corruption, whereas false negatives do not. -- Trond Myklebust Linux NFS client maintainer, PrimaryData trond.myklebust@xxxxxxxxxxxxxxx -- 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
