Introduce fscrypt_dio_supported() to check whether a direct I/O request
is unsupported due to encryption constraints.
Also introduce fscrypt_limit_io_blocks() to limit how many blocks can be
added to a bio being prepared for direct I/O. This is needed for
filesystems that use the iomap direct I/O implementation to avoid DUN
wraparound in the middle of a bio (which is possible with the
IV_INO_LBLK_32 IV generation method). Elsewhere fscrypt_mergeable_bio()
is used for this, but iomap operates on logical ranges directly, so
filesystems using iomap won't have a chance to call fscrypt_mergeable_bio()
on every block added to a bio. So we need this function which limits a
logical range in one go.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Co-developed-by: Satya Tangirala <satyat@google.com>
Signed-off-by: Satya Tangirala <satyat@google.com>
Bug: 162255927
Link: https://lore.kernel.org/r/20200724184501.1651378-2-satyat@google.com
Change-Id: I1dbd4f382d510d9b779d5e44a77fadf7040cf077
Signed-off-by: Eric Biggers <ebiggers@google.com>
bc2933702d