On Tue, Jul 10, 2007 at 04:31:44PM -0700, Andrew Morton wrote: > On Sun, 01 Jul 2007 03:37:53 -0400 > Mingming Cao <cmm@xxxxxxxxxx> wrote: > > > Add a "noversion" mount option to disable inode version updates. > > Why is this option being offered to our users? To reduce disk traffic, > like noatime? > > If so, what are the implications of this? What would the user lose? This has been removed in the latest patch set; it's needed only for Lustre, because they set the version field themselves. Lustre needs the inode version to be globally monotonically increasing, so it can order updates between two different files, so it does this itself. NFSv4 only uses i_version to detect changes, and so there's no need to use a global atomic counter for i_version. So the thinking was that there was no point doing the global atomic counter if it was not necessary. Since "noversion" is Lustre specific, we've dropped that from the list of patches that we'll push, and so the inode version will only have local per-inode significance, and not have any global ordering properties. We have not actually benchmarked whether or not doing the global ordering actually *matters* in terms of being actually noticeable. If it isn't noticeable, I wouldn't mind changing things so that we always make i_version globally significant (without a mount option), and make life a bit easier for the Lustre folks. Or if someone other distributed filesystem requests a globally significant i_version. But we can cross that bridge when we get to it.... - Ted - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
