On Fri, 16 Jul 2021, J. Bruce Fields wrote: > On Thu, Jul 15, 2021 at 02:37:52PM +1000, NeilBrown wrote: > > To fix this, we need to report a different fsid for each subvolume, but > > need to use the same fsid that we currently use for the top-level > > volume. Changing this (by rebooting a server to new code), might > > confuse the client. I don't think it would be a major problem (stale > > filehandles shouldn't happen), but it is best avoided. > ... > > Again, we really want an API to get this from the filesystem. Changing > > it later has no cost, so we don't need any commitment from the btrfs team > > that this is what they will provide if/when we do get such an API. > > "No cost" makes me a little nervous, are we sure nobody will notice the > mountd-on-fileid changing? One cannot be 100% sure, but I cannot see how anything would depend on it being stable. Certainly the kernel doesn't. 'ls -i' doesn't report it - even as "ls -if". "find -inum xx" cannot see it. Obviously readdir() will see it but if any application put much weight on the number, it could already get confused when btrfs returns non-unique numbers as I mentioned. I certainly wouldn't lose sleep over changing it. NeilBrown > > Fileid and fsid changes I'd worry about more, though I wouldn't rule it > out if that'd stand in the way of a bug fix. > > Thanks for looking into this. > > --b. > >
