Re: [PATCH v6 6/7] fscrypt: document inline encryption support

[Eric Biggers <ebiggers@kernel.org>]

On Fri, Jul 24, 2020 at 06:45:00PM +0000, Satya Tangirala wrote:
> Update the fscrypt documentation file for inline encryption support.
> 
> Signed-off-by: Satya Tangirala <satyat@google.com>
> Reviewed-by: Eric Biggers <ebiggers@google.com>
> Reviewed-by: Jaegeuk Kim <jaegeuk@kernel.org>
> ---
>  Documentation/filesystems/fscrypt.rst | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/filesystems/fscrypt.rst b/Documentation/filesystems/fscrypt.rst
> index 1a6ad6f736b5..423c5a0daf45 100644
> --- a/Documentation/filesystems/fscrypt.rst
> +++ b/Documentation/filesystems/fscrypt.rst
> @@ -1204,6 +1204,18 @@ buffer.  Some filesystems, such as UBIFS, already use temporary
>  buffers regardless of encryption.  Other filesystems, such as ext4 and
>  F2FS, have to allocate bounce pages specially for encryption.
>  
> +Fscrypt is also able to use inline encryption hardware instead of the
> +kernel crypto API for en/decryption of file contents.  When possible,
> +and if directed to do so (by specifying the 'inlinecrypt' mount option
> +for an ext4/F2FS filesystem), it adds encryption contexts to bios and
> +uses blk-crypto to perform the en/decryption instead of making use of
> +the above read/write path changes.  Of course, even if directed to
> +make use of inline encryption, fscrypt will only be able to do so if
> +either hardware inline encryption support is available for the
> +selected encryption algorithm or CONFIG_BLK_INLINE_ENCRYPTION_FALLBACK
> +is selected.  If neither is the case, fscrypt will fall back to using
> +the above mentioned read/write path changes for en/decryption.
> +
>  Filename hashing and encoding
>  -----------------------------
>  
> @@ -1250,7 +1262,9 @@ Tests
>  
>  To test fscrypt, use xfstests, which is Linux's de facto standard
>  filesystem test suite.  First, run all the tests in the "encrypt"
> -group on the relevant filesystem(s).  For example, to test ext4 and
> +group on the relevant filesystem(s).  One can also run the tests
> +with the 'inlinecrypt' mount option to test the implementation for
> +inline encryption support.  For example, to test ext4 and
>  f2fs encryption using `kvm-xfstests
>  <https://github.com/tytso/xfstests-bld/blob/master/Documentation/kvm-quickstart.md>`_::

Since this patch is separate from the direct I/O support, I've applied it to
fscrypt.git#master for 5.9.  I'm not applying the direct I/O patches yet.

- Eric