On Wed, Aug 14, 2013 at 11:18 PM, David Lang <david@xxxxxxx> wrote: > On Wed, 14 Aug 2013, Andy Lutomirski wrote: > >>> The big problem with this approach is that not doing the >>> timestamp update on page faults is going to break the inode change >>> version counting because for ext4, btrfs and XFS it takes a >>> transaction to bump that counter. NFS needs to know the moment a >>> file is changed in memory, not when it is written to disk. Also, NFS >>> requires the change to the counter to be persistent over server >>> failures, so it needs to be changed as part of a transaction.... >> >> >> NFS can do whatever it wants, although I suspect that even NFS can get >> away with deferring cmtime updates. > > > NFS already has to do syncs to make sure the data is safe on disk, have a > flag that NFS can use to make the ctime safe, everyone else can get the > performance improvement and NFS can have it's slow-but-safe approach. > I don't see the current code that updates times for NFS. I'm not planning on making any changes that'll affect NFS at all (i.e. I don't think any flag will be needed), but I'd be more confident if I understand why it worked in the first place. (For filesystems that provide page_mkwrite, there hasn't been a file_update_time call in the core code for several kernel versions.) --Andy -- 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
