Re: [PATCH v7 6/8] ext4: support direct I/O with fscrypt using blk-crypto

Theodore Y. Ts'o
2020-12-03T13:47:09Z

On Tue, Nov 17, 2020 at 02:07:06PM +0000, Satya Tangirala wrote:
> From: Eric Biggers <ebiggers@google.com>
>
> Wire up ext4 with fscrypt direct I/O support. Direct I/O with fscrypt is
> only supported through blk-crypto (i.e. CONFIG_BLK_INLINE_ENCRYPTION must
> have been enabled, the 'inlinecrypt' mount option must have been specified,
> and either hardware inline encryption support must be present or
> CONFIG_BLK_INLINE_ENCYRPTION_FALLBACK must have been enabled). Further,
> direct I/O on encrypted files is only supported when the *length* of the
> I/O is aligned to the filesystem block size (which is *not* necessarily the
> same as the block device's block size).
>
> fscrypt_limit_io_blocks() is called before setting up the iomap to ensure
> that the blocks of each bio that iomap will submit will have contiguous
> DUNs. Note that fscrypt_limit_io_blocks() is normally a no-op, as normally
> the DUNs simply increment along with the logical blocks. But it's needed
> to handle an edge case in one of the fscrypt IV generation methods.
>
> Signed-off-by: Eric Biggers <ebiggers@google.com>
> Co-developed-by: Satya Tangirala <satyat@google.com>
> Signed-off-by: Satya Tangirala <satyat@google.com>
> Reviewed-by: Jaegeuk Kim <jaegeuk@kernel.org>

Acked-by: Theodore Ts'o <tytso@mit.edu>