On Thu, 2010-12-02 at 10:49 +0100, Arne Jansen wrote: > Josef Bacik wrote: > > > > 1) Scrap the 256 inode number thing. Instead we'll just put a flag in the > > inode > > to say "Hey, I'm a subvolume" and then we can do all of the appropriate > > magic > > that way. This unfortunately will be an incompatible format change, but the > > sooner we get this adressed the easier it will be in the long run. > > Obviously > > when I say format change I mean via the incompat bits we have, so old fs's > > won't > > be broken and such. > > > > 2) Do something like NFS's referral mounts when we cd into a subvolume. > > Now we > > just do dentry trickery, but that doesn't make the boundary between > > subvolumes > > clear, so it will confuse people (and samba) when they walk into a > > subvolume and > > all of a sudden the inode numbers are the same as in the directory behind > > them. > > With doing the referral mount thing, each subvolume appears to be its own > > mount > > and that way things like NFS and samba will work properly. > > > > What about the alternative and allocating inode numbers globally? The only > problem would be with snapshots as they share the inum with the source, but > one could just remap inode numbers in snapshots by sparing some bits at the > top of this 64 bit field. > > Having one mount per subvolume/snapshots is the cleaner solution, but > quickly leads to situations where you have _lots_ of mounts, especially when > you export them via NFS and mount it somewhere else. I've seen a machine > which had to handle > 100,000 mounts from a zfs server. This definitely > brings it's own problems, so I'd love to see a full fs exported as a single > mount. This will also keep output from tools like iostat (for nfs mounts) > and df readable.
Having a lot of mounts will be a problem when the mount table is exposed directly from the kernel, something that must be done, and is being done in the latest util-linux. Ian -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
