On Mon, Jan 11, 2016 at 11:56:25PM +0100, Richard Weinberger wrote: > Hi! > > I consider adding file encryption to UBIFS. > While looking into ext4 and f2fs I realized that both > use the same data structures/concepts. When the ext4 code was first posted, I noted that 90% of the implementation was not ext4 specific at all. I asked that the encryption part of it be lifted to fs/ and the API made generic so that it can be shared without needing to copy and re-review encryption code (which is notoriously hard to get right) when others implement the same fucntionality. This was considered SEP. > f2fs copy&pasted a lot from ext4. Yes, they did, even though I asked them not to, but to instead pull all the code that is non-ext4 specific up to the VFS first and then use that. Again, this was considered SEP. > Before I do the next copy&paste, I'd to ask whether it would make sense > to more parts of the ioctl() interface out to VFS? Yes, unfortunately you're the first "somebody else" who is going to have to deal with this problem. It's not just the API - most of the encryption implementation is also copy and pasted, too. This simply hasn't got to the top of my list of stuff to do for XFS yet, so I haven't started down this path yet. However, if you do start on the hard work to pull all this stuff up into the VFS and generic helpers, I'll do what I can to get the necessary parts of XFS working with it as well.... [snip] > So, the data structures are identical and AFAIK also the supported cipher modes are. > But as both use their own ioctls having a single tool to control file encryption > can be error prone in future. > Interestingly the current ioctls for ext4 and f2fs resolve to the same integers, > is this on purpose? :) Yes, so that when someone factors it all into a generic implementation the new "FS_IOC*" ioctl API will be binary compatible with the existing ext4 and f2fs ioctl implementations and the existing userspace tools will just continue to work. > Wouldn't it be worthwhile having exactly the same ioctls such that util-linux could offer > a decent file encryption tool which can be used by all file systems with file encryption > support? Yes, it should have been done that way in the first place. > Another thing are semantics, ext4 implemented a policy which controls > under which conditions encrypted files are allowed to be unlinked, moved, etc... > f2fs adopted these from ext4. But can't we do that in VFS or at least > agree one a policy and document it? :-) Yes, we should. Having a single set of policies implemented and enforced at the VFS is how this should be done. Users will absolutely hate us if per-file encryption devolves into APIs and policies that differ between filesystems. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
