On Wed, Jul 29, 2009 at 03:14:49PM +0100, Pádraig Brady wrote: > Chris Mason wrote: > > On Tue, Jul 28, 2009 at 10:06:35PM +0200, Giuseppe Scrivano wrote: > >> > >> I can't replicate it now, all tests I am doing report that blocks used > >> before and after the clone are the same. Probably yesterday the > >> difference I noticed was in reality the original file flushed to the > >> disk. > > > > The clone will use some additional space for the metadata required to > > point to the cloned blocks. It isn't exactly O(1) it is O(metadata for > > the file). > > Thanks for the clarification Chris. > So the just committed change in cp will > link the destination file to the extents of the source. > > We may need to play around with fallocate() > if we want to get back to the original > cp semantics of actually allocating space > on the file system for the new file.
Well, best to just use the original cp code. I was talking with Giuseppe about this as well, I think we should the option to do regular cp via a flag. There will soon be a reflink system call that can be used on ocfs2 and btrfs as well. Thanks for adding this to glibc! -chris -- 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
