On Tue, 2009-05-05 at 17:03 +0100, Jamie Lokier wrote: > Chris Mason wrote: > > > > The main difference between reflink and the btrfs ioctl is that in the > > > > btrfs ioctl the destination file must already exist. The btrfs code can > > > > also do range replacements in the destination file, but I'd agree with > > > > Joel that we don't want to toss the kitchen sink into something nice and > > > > clean like reflink. > > > > > > Ah, now that I know about the BTRFS data-cloning ioctl... :-) > > > > > > I'm wondering why reflink() is needed at all. Can't it be done in > > > userspace, using the BTRFS ioctl? The hard part in userspace seems to > > > be copying the file attributes, but "cp -a" and other tools manage. > > > > > > > reflink is a subset of what the btrfs ioctl does, and that's a good > > thing. The way they've added support for this to ocfs2 is really cool, > > and the same ideas could be used in other filesystems. > > > > So, I'd rather see a system call that everyone can implement, and if > > btrfs hangs on to the ioctl for extra features, even better. > > Realistically, very few existing filesystems can implement this system call. > I'd say that if the shared disk clustering filesystem can do it, pretty much anyone can ;) This doesn't mean its easy, but it is a good set of semantics to have as the baseline. -chris -- 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
