Re: [PATCH 0/3] add support for metadata encryption to F2FS

[Chao Yu]

On 2020/12/18 19:53, Satya Tangirala wrote:
> On Fri, Dec 18, 2020 at 05:02:23PM +0800, Chao Yu wrote:
> > On 2020/12/17 23:44, Satya Tangirala wrote:
> > > On Sat, Oct 10, 2020 at 05:53:06PM +0800, Chao Yu wrote:
> > > > Why not using nid as DUN, then GC could migrate encrypted node block directly via
> > > > meta inode's address space like we do for encrypted data block, rather than
> > > > decrypting node block to node page and then encrypting node page with DUN of new
> > > > blkaddr it migrates to.
> > > The issue is, the bi_crypt_context in a bio holds a single DUN value,
> > > which is the DUN for the first data unit in the bio. blk-crypto assumes
> > > that the DUN of each subsequent data unit can be computed by simply
> > > incrementing the DUN. So physically contiguous data units can only be put
> > > into the same bio if they also have contiguous DUNs. I don't know much
> > > about nids, but if the nid is invariant w.r.t the physical block location,
> > > then there might be more fragmentation of bios in regular read/writes
> >
> > Correct, considering performance of in batch node flush, it will be better to
> > use pba as IV value.
> >
> > But, what's the plan about supporting software encryption for metadata? Current
> > f2fs write flow will handle all operations which may encounter failure before
> > allocating block address for node, if we do allocation first, and then use pba
> > as IV to encrypt node block, it will be a little complicated to revert allocation
> > if we fail to encrypt node block.
> Software encryption for metadata is supported through the blk-crypto

blk-crypto will encrypt all data in filesystem, if FBE is enabled, data may
be encrypted twice?

And why not supporting hardware encryption for metadata in blk-crypto? then
both f2fs and ext4 can use inline-encryption based blk-crypto?

Thanks,

> framework - so encryption will happen in the block layer, not the
> filesystem layer. So there's nothing extra/special we need to do if
> there's an encryption failure - an encryption failure is no different
> from a read/write failure in a lower layer from f2fs' perspective.
> .