On Wed, Mar 15, 2017 at 02:09:13PM -0400, J. Bruce Fields wrote: > On Thu, Mar 02, 2017 at 11:38:03AM -0500, Olga Kornievskaia wrote: > > > On Mar 2, 2017, at 11:07 AM, Christoph Hellwig <hch@xxxxxx> wrote: > > > NAK, we really should not do operations between different > > > superblocks. > > > > Can you provide some reasoning as to why? What would it break? The > > reasoning for including one is to allow for a file system to achieve > > better performance which seems like a feature that would be of great > > benefit. -- > > Yes, this has come up a few times. What's going on?: > > - There was an explanation, and I missed it. > - The explanation is complicated and Christoph hasn't had time > to write it up. > - Christoph has a strong suspicion there are issues without > being sure exactly where they are. > - Something else? As far as I can tell from talking at LSF: - file system operations crossing superblocks is unusual. No specific known issue. Also not sure I understand why splice isn't precedent. - implementation (with server acting as a client, long-running process, etc.) will be complicated and ugly. Sure, I guess we'll see how complicated and weigh that against any advantages. (Though I'm curious about case e.g. of btrfs clone--can't it easily clone across filesystem boundaries in some cases when they share storage?) Anyway. I'll read the patches. Probably not this week. --b.
