On 11/30/21 5:03 AM, Eric Biggers wrote:
From: Eric Biggers <ebiggers@xxxxxxxxxx>
Add sysfs files that expose the inline encryption capabilities of
request queues:
/sys/class/block/$disk/queue/crypto/max_dun_bits
/sys/class/block/$disk/queue/crypto/modes/$mode
/sys/class/block/$disk/queue/crypto/num_keyslots
Userspace can use these new files to decide what encryption settings to
use, or whether to use inline encryption at all. This also brings the
crypto capabilities in line with the other queue properties, which are
already discoverable via the queue directory in sysfs.
Design notes:
- Place the new files in a new subdirectory "crypto" to group them
together and to avoid complicating the main "queue" directory. This
also makes it possible to replace "crypto" with a symlink later if
we ever make the blk_crypto_profiles into real kobjects (see below).
- It was necessary to define a new kobject that corresponds to the
crypto subdirectory. For now, this kobject just contains a pointer
to the blk_crypto_profile. Note that multiple queues (and hence
multiple such kobjects) may refer to the same blk_crypto_profile.
An alternative design would more closely match the current kernel
data structures: the blk_crypto_profile could be a kobject itself,
located directly under the host controller device's kobject, while
/sys/class/block/$disk/queue/crypto would be a symlink to it.
I decided not to do that for now because it would require a lot more
changes, such as no longer embedding blk_crypto_profile in other
structures, and also because I'm not sure we can rule out moving the
crypto capabilities into 'struct queue_limits' in the future. (Even
if multiple queues share the same crypto engine, maybe the supported
data unit sizes could differ due to other queue properties.) It
would also still be possible to switch to that design later without
breaking userspace, by replacing the directory with a symlink.
- Use "max_dun_bits" instead of "max_dun_bytes". Currently, the
kernel internally stores this value in bytes, but that's an
implementation detail. It probably makes more sense to talk about
this value in bits, and choosing bits is more future-proof.
- "modes" is a sub-subdirectory, since there may be multiple supported
crypto modes, and sysfs is supposed to have one value per file.
Why do you have a sub-directory here?
From what I can see, that subdirectory just contains the supported
modes, so wouldn't it be easier to create individual files like
'mode_<modename>' instead of a subdirectory?
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@xxxxxxx +49 911 74053 688
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