On Tue, Nov 17, 2020 at 02:07:06PM +0000, Satya Tangirala wrote:

From: Eric Biggers <redacted>

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 <redacted>
Co-developed-by: Satya Tangirala <redacted>
Signed-off-by: Satya Tangirala <redacted>
Reviewed-by: Jaegeuk Kim <jaegeuk@kernel.org>

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