Colin Walters wrote: > On Thu, Apr 10, 2014 at 3:15 PM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> > wrote: >> >> >> COW links can do this already, I think. Of course, you'll have to >> use a >> filesystem that supports them. > > COW is nice if the filesystem supports them, but my userspace code > needs to be filesystem agnostic. Because of that, the design for > userspace simply doesn't allow arbitrary writes. > > Instead, I have to painfully audit every rpm %post/dpkg postinst type > script to ensure they break hardlinks, and furthermore only allow > executing scripts that are known to do so. > > But I think even in a btrfs world it'd still be useful to mark files as > content-immutable. If you create each tree as a subvolume and when it's complete put it in place with btrfs subvolume snapshot -r FOO_inprogress /ostree/repo/FOO, you get exactly that. You can even use the new(ish) btrfs out-of-band dedup functionality to deduplicate read-only snapshots safely. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>