Lines Matching +full:background +full:- +full:layer
1 .. SPDX-License-Identifier: GPL-2.0
9 Background chapter
19 keys directly in low-level I/O requests. However, most inline encryption
22 low-level I/O request then just contains a keyslot index and data unit number.
28 managed by the block layer, not the kernel crypto API.
30 Inline encryption hardware is also very different from "self-encrypting drives",
31 such as those based on the TCG Opal or ATA Security standards. Self-encrypting
32 drives don't provide fine-grained control of encryption and provide no way to
34 provides fine-grained control of encryption, including the choice of key and
43 layered devices like device-mapper and loopback (i.e. we want to be able to use
50 - We need a way for upper layers (e.g. filesystems) to specify an encryption
53 Encryption contexts also introduce constraints on bio merging; the block layer
56 - Different inline encryption hardware has different supported algorithms,
61 - Inline encryption hardware usually (but not always) requires that keys be
65 keyslots and reuse an already-programmed keyslot when possible.
67 - Upper layers typically define a specific end-of-life for crypto keys, e.g.
72 - When possible, device-mapper devices must be able to pass through the inline
74 sense for device-mapper devices to have keyslots themselves.
88 of the block layer (e.g. filesystems) to provide an encryption context when
90 layer and device drivers. Note that the encryption context doesn't explicitly
95 encryption-related state for a particular inline encryption device. The
103 This happens in the block layer, so that users of the block layer can just
107 Specifically, for each keyslot, the block layer (via the blk_crypto_profile)
109 in-flight I/O requests are using it. When the block layer creates a
112 keyslot (a keyslot that isn't in-use by any I/O), then programs the key into the
113 least-recently-used idle keyslot using the function the device driver provided.
119 Requests can be built from multiple bios, and the block layer must take the
124 retained, since the remaining bios have been verified to be merge-compatible
132 blk-crypto-fallback
137 likewise for the block layer's keyslot management logic. It is also desirable
141 Therefore, we also introduce *blk-crypto-fallback*, which is an implementation
142 of inline encryption using the kernel crypto API. blk-crypto-fallback is built
143 into the block layer, so it works on any block device without any special setup.
145 block_device that doesn't support that encryption context, the block layer will
146 handle en/decryption of the bio using blk-crypto-fallback.
148 For encryption, the data cannot be encrypted in-place, as callers usually rely
149 on it being unmodified. Instead, blk-crypto-fallback allocates bounce pages,
152 blk-crypto-fallback completes the original bio. If the original bio is too
155 For decryption, blk-crypto-fallback "wraps" the bio's completion callback
158 successfully, blk-crypto-fallback restores the bio's original completion
159 callback and private data, then decrypts the bio's data in-place using the
161 Afterwards, blk-crypto-fallback completes the bio.
163 In both cases, the bios that blk-crypto-fallback submits no longer have an
166 blk-crypto-fallback also defines its own blk_crypto_profile and has its own
174 makes sense for blk-crypto-fallback.
177 blk-crypto-fallback is used, the ciphertext written to disk (and hence the
178 on-disk format of data) will be the same (assuming that both the inline
182 blk-crypto-fallback is optional and is controlled by the
185 API presented to users of the block layer
190 block_device -- either via hardware or via blk-crypto-fallback. This function
193 size, etc. This function can be useful if blk-crypto-fallback is disabled.
199 was called earlier). This is needed to initialize blk-crypto-fallback if it
214 In summary, for users of the block layer, the lifecycle of a blk_crypto_key is
233 must call ``blk_crypto_profile_init()`` (or its resource-managed variant
254 while the device is runtime-suspended, then the driver must also set the ``dev``
256 resumed before any of the low-level operations are called.
269 Request queue based layered devices like dm-rq that wish to support inline
272 pass a clone of that request to another request_queue, blk-crypto will
289 re-generate the integrity info from the ciphertext data and store that on disk