Re: [PATCH 0/1] userspace support for F2FS metadata encryption

[Eric Biggers <ebiggers@kernel.org>]

On Mon, Oct 05, 2020 at 07:41:32AM +0000, Satya Tangirala wrote:
> The kernel patches for F2FS metadata encryption are at:
> 
> https://lore.kernel.org/linux-fscrypt/20201005073606.1949772-4-satyat@google.com/
> 
> This patch implements the userspace changes required for metadata
> encryption support as implemented in the kernel changes above. All blocks
> in the filesystem are encrypted with the user provided metadata encryption
> key except for the superblock (and its redundant copy). The DUN for a block
> is its offset from the start of the filesystem.
> 
> This patch introduces two new options for the userspace tools: '-A' to
> specify the encryption algorithm, and '-M' to specify the encryption key.
> mkfs.f2fs will store the encryption algorithm used for metadata encryption
> in the superblock itself, so '-A' is only applicable to mkfs.f2fs. The rest
> of the tools only take the '-M' option, and will obtain the encryption
> algorithm from the superblock of the FS.

As I mentioned on the kernel patches, it might make sense to compute a
metadata_key_identifier and store it in the super_block so that it can be
automatically requested without needing to provide an option.

> 
> Limitations: 
> Metadata encryption with sparse storage has not been implemented yet in
> this patch.
> 
> This patch requires the metadata encryption key to be readable from
> userspace, and does not ensure that it is zeroed before the program exits
> for any reason.
> 
> Satya Tangirala (1):
>   f2fs-tools: Introduce metadata encryption support

A cover letter shouldn't be used for a 1-patch series.  Just include these
details in the patch instead.

- Eric