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path: root/fs/ext4/crypto.c
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2023-09-26fscrypt: support crypto data unit size less than filesystem block sizeEric Biggers1-0/+1
Until now, fscrypt has always used the filesystem block size as the granularity of file contents encryption. Two scenarios have come up where a sub-block granularity of contents encryption would be useful: 1. Inline crypto hardware that only supports a crypto data unit size that is less than the filesystem block size. 2. Support for direct I/O at a granularity less than the filesystem block size, for example at the block device's logical block size in order to match the traditional direct I/O alignment requirement. (1) first came up with older eMMC inline crypto hardware that only supports a crypto data unit size of 512 bytes. That specific case ultimately went away because all systems with that hardware continued using out of tree code and never actually upgraded to the upstream inline crypto framework. But, now it's coming back in a new way: some current UFS controllers only support a data unit size of 4096 bytes, and there is a proposal to increase the filesystem block size to 16K. (2) was discussed as a "nice to have" feature, though not essential, when support for direct I/O on encrypted files was being upstreamed. Still, the fact that this feature has come up several times does suggest it would be wise to have available. Therefore, this patch implements it by using one of the reserved bytes in fscrypt_policy_v2 to allow users to select a sub-block data unit size. Supported data unit sizes are powers of 2 between 512 and the filesystem block size, inclusively. Support is implemented for both the FS-layer and inline crypto cases. This patch focuses on the basic support for sub-block data units. Some things are out of scope for this patch but may be addressed later: - Supporting sub-block data units in combination with FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64, in most cases. Unfortunately this combination usually causes data unit indices to exceed 32 bits, and thus fscrypt_supported_policy() correctly disallows it. The users who potentially need this combination are using f2fs. To support it, f2fs would need to provide an option to slightly reduce its max file size. - Supporting sub-block data units in combination with FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32. This has the same problem described above, but also it will need special code to make DUN wraparound still happen on a FS block boundary. - Supporting use case (2) mentioned above. The encrypted direct I/O code will need to stop requiring and assuming FS block alignment. This won't be hard, but it belongs in a separate patch. - Supporting this feature on filesystems other than ext4 and f2fs. (Filesystems declare support for it via their fscrypt_operations.) On UBIFS, sub-block data units don't make sense because UBIFS encrypts variable-length blocks as a result of compression. CephFS could support it, but a bit more work would be needed to make the fscrypt_*_block_inplace functions play nicely with sub-block data units. I don't think there's a use case for this on CephFS anyway. Link: https://lore.kernel.org/r/20230925055451.59499-6-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2023-09-26fscrypt: replace get_ino_and_lblk_bits with just has_32bit_inodesEric Biggers1-8/+1
Now that fs/crypto/ computes the filesystem's lblk_bits from its maximum file size, it is no longer necessary for filesystems to provide lblk_bits via fscrypt_operations::get_ino_and_lblk_bits. It is still necessary for fs/crypto/ to retrieve ino_bits from the filesystem. However, this is used only to decide whether inode numbers fit in 32 bits. Also, ino_bits is static for all relevant filesystems, i.e. it doesn't depend on the filesystem instance. Therefore, in the interest of keeping things as simple as possible, replace 'get_ino_and_lblk_bits' with a flag 'has_32bit_inodes'. This can always be changed back to a function if a filesystem needs it to be dynamic, but for now a static flag is all that's needed. Link: https://lore.kernel.org/r/20230925055451.59499-5-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2023-09-25fscrypt: make the bounce page pool opt-in instead of opt-outEric Biggers1-0/+1
Replace FS_CFLG_OWN_PAGES with a bit flag 'needs_bounce_pages' which has the opposite meaning. I.e., filesystems now opt into the bounce page pool instead of opt out. Make fscrypt_alloc_bounce_page() check that the bounce page pool has been initialized. I believe the opt-in makes more sense, since nothing else in fscrypt_operations is opt-out, and these days filesystems can choose to use blk-crypto which doesn't need the fscrypt bounce page pool. Also, I happen to be planning to add two more flags, and I wanted to fix the "FS_CFLG_" name anyway as it wasn't prefixed with "FSCRYPT_". Link: https://lore.kernel.org/r/20230925055451.59499-3-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2023-09-25fscrypt: make it clearer that key_prefix is deprecatedEric Biggers1-1/+1
fscrypt_operations::key_prefix should not be set by any filesystems that aren't setting it already. This is already documented, but apparently it's not sufficiently clear, as both ceph and btrfs have tried to set it. Rename the field to legacy_key_prefix and improve the documentation to hopefully make it clearer. Link: https://lore.kernel.org/r/20230925055451.59499-2-ebiggers@kernel.org Signed-off-by: Eric Biggers <ebiggers@google.com>
2023-08-05ext4: fix memory leaks in ext4_fname_{setup_filename,prepare_lookup}Luís Henriques1-0/+4
If the filename casefolding fails, we'll be leaking memory from the fscrypt_name struct, namely from the 'crypto_buf.name' member. Make sure we free it in the error path on both ext4_fname_setup_filename() and ext4_fname_prepare_lookup() functions. Cc: stable@kernel.org Fixes: 1ae98e295fa2 ("ext4: optimize match for casefolded encrypted dirs") Signed-off-by: Luís Henriques <lhenriques@suse.de> Reviewed-by: Eric Biggers <ebiggers@google.com> Link: https://lore.kernel.org/r/20230803091713.13239-1-lhenriques@suse.de Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2022-05-22ext4: refactor and move ext4_ioctl_get_encryption_pwsalt()Ritesh Harjani1-0/+54
This patch move code for FS_IOC_GET_ENCRYPTION_PWSALT case into ext4's crypto.c file, i.e. ext4_ioctl_get_encryption_pwsalt() and uuid_is_zero(). This is mostly refactoring logic and should not affect any functionality change. Suggested-by: Eric Biggers <ebiggers@google.com> Reviewed-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Ritesh Harjani <ritesh.list@gmail.com> Link: https://lore.kernel.org/r/5af98b17152a96b245b4f7d2dfb8607fc93e36aa.1652595565.git.ritesh.list@gmail.com Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2022-05-22ext4: cleanup function defs from ext4.h into crypto.cRitesh Harjani1-0/+65
Some of these functions when CONFIG_FS_ENCRYPTION is enabled are not really inline (let compiler be the best judge of it). Remove inline and move them into crypto.c where they should be present. Reviewed-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Ritesh Harjani <ritesh.list@gmail.com> Link: https://lore.kernel.org/r/b7b9de2c7226298663fb5a0c28909135e2ab220f.1652595565.git.ritesh.list@gmail.com Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2022-05-22ext4: move ext4 crypto code to its own file crypto.cRitesh Harjani1-0/+127
This is to cleanup super.c file which has grown quite large. So, start moving ext4 crypto related code to where it should be in the first place i.e. fs/ext4/crypto.c Reviewed-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Ritesh Harjani <ritesh.list@gmail.com> Link: https://lore.kernel.org/r/7d637e093cbc34d727397e8d41a53a1b9ca7d7a4.1652595565.git.ritesh.list@gmail.com Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2016-07-10ext4 crypto: migrate into vfs's crypto engineJaegeuk Kim1-536/+0
This patch removes the most parts of internal crypto codes. And then, it modifies and adds some ext4-specific crypt codes to use the generic facility. Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2016-04-13ext4/fscrypto: avoid RCU lookup in d_revalidateJaegeuk Kim1-0/+4
As Al pointed, d_revalidate should return RCU lookup before using d_inode. This was originally introduced by: commit 34286d666230 ("fs: rcu-walk aware d_revalidate method"). Reported-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org> Cc: Theodore Ts'o <tytso@mit.edu> Cc: stable <stable@vger.kernel.org>
2016-04-08Merge tag 'ext4_for_linus_stable' of ↵Linus Torvalds1-20/+29
git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4 Pull ext4 bugfixes from Ted Ts'o: "These changes contains a fix for overlayfs interacting with some (badly behaved) dentry code in various file systems. These have been reviewed by Al and the respective file system mtinainers and are going through the ext4 tree for convenience. This also has a few ext4 encryption bug fixes that were discovered in Android testing (yes, we will need to get these sync'ed up with the fs/crypto code; I'll take care of that). It also has some bug fixes and a change to ignore the legacy quota options to allow for xfstests regression testing of ext4's internal quota feature and to be more consistent with how xfs handles this case" * tag 'ext4_for_linus_stable' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4: ext4: ignore quota mount options if the quota feature is enabled ext4 crypto: fix some error handling ext4: avoid calling dquot_get_next_id() if quota is not enabled ext4: retry block allocation for failed DIO and DAX writes ext4: add lockdep annotations for i_data_sem ext4: allow readdir()'s of large empty directories to be interrupted btrfs: fix crash/invalid memory access on fsync when using overlayfs ext4 crypto: use dget_parent() in ext4_d_revalidate() ext4: use file_dentry() ext4: use dget_parent() in ext4_file_open() nfs: use file_dentry() fs: add file_dentry() ext4 crypto: don't let data integrity writebacks fail with ENOMEM ext4: check if in-inode xattr is corrupted in ext4_expand_extra_isize_ea()
2016-04-04mm, fs: get rid of PAGE_CACHE_* and page_cache_{get,release} macrosKirill A. Shutemov1-4/+4
PAGE_CACHE_{SIZE,SHIFT,MASK,ALIGN} macros were introduced *long* time ago with promise that one day it will be possible to implement page cache with bigger chunks than PAGE_SIZE. This promise never materialized. And unlikely will. We have many places where PAGE_CACHE_SIZE assumed to be equal to PAGE_SIZE. And it's constant source of confusion on whether PAGE_CACHE_* or PAGE_* constant should be used in a particular case, especially on the border between fs and mm. Global switching to PAGE_CACHE_SIZE != PAGE_SIZE would cause to much breakage to be doable. Let's stop pretending that pages in page cache are special. They are not. The changes are pretty straight-forward: - <foo> << (PAGE_CACHE_SHIFT - PAGE_SHIFT) -> <foo>; - <foo> >> (PAGE_CACHE_SHIFT - PAGE_SHIFT) -> <foo>; - PAGE_CACHE_{SIZE,SHIFT,MASK,ALIGN} -> PAGE_{SIZE,SHIFT,MASK,ALIGN}; - page_cache_get() -> get_page(); - page_cache_release() -> put_page(); This patch contains automated changes generated with coccinelle using script below. For some reason, coccinelle doesn't patch header files. I've called spatch for them manually. The only adjustment after coccinelle is revert of changes to PAGE_CAHCE_ALIGN definition: we are going to drop it later. There are few places in the code where coccinelle didn't reach. I'll fix them manually in a separate patch. Comments and documentation also will be addressed with the separate patch. virtual patch @@ expression E; @@ - E << (PAGE_CACHE_SHIFT - PAGE_SHIFT) + E @@ expression E; @@ - E >> (PAGE_CACHE_SHIFT - PAGE_SHIFT) + E @@ @@ - PAGE_CACHE_SHIFT + PAGE_SHIFT @@ @@ - PAGE_CACHE_SIZE + PAGE_SIZE @@ @@ - PAGE_CACHE_MASK + PAGE_MASK @@ expression E; @@ - PAGE_CACHE_ALIGN(E) + PAGE_ALIGN(E) @@ expression E; @@ - page_cache_get(E) + get_page(E) @@ expression E; @@ - page_cache_release(E) + put_page(E) Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Acked-by: Michal Hocko <mhocko@suse.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-03-26ext4 crypto: use dget_parent() in ext4_d_revalidate()Theodore Ts'o1-4/+8
This avoids potential problems caused by a race where the inode gets renamed out from its parent directory and the parent directory is deleted while ext4_d_revalidate() is running. Fixes: 28b4c263961c Reported-by: Al Viro <viro@ZenIV.linux.org.uk> Signed-off-by: Theodore Ts'o <tytso@mit.edu> Cc: stable@vger.kernel.org
2016-03-26ext4 crypto: don't let data integrity writebacks fail with ENOMEMTheodore Ts'o1-16/+21
We don't want the writeback triggered from the journal commit (in data=writeback mode) to cause the journal to abort due to generic_writepages() returning an ENOMEM error. In addition, if fsync() fails with ENOMEM, most applications will probably not do the right thing. So if we are doing a data integrity sync, and ext4_encrypt() returns ENOMEM, we will submit any queued I/O to date, and then retry the allocation using GFP_NOFAIL. Google-Bug-Id: 27641567 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2016-03-17Merge branch 'linus' of ↵Linus Torvalds1-13/+11
git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 Pull crypto update from Herbert Xu: "Here is the crypto update for 4.6: API: - Convert remaining crypto_hash users to shash or ahash, also convert blkcipher/ablkcipher users to skcipher. - Remove crypto_hash interface. - Remove crypto_pcomp interface. - Add crypto engine for async cipher drivers. - Add akcipher documentation. - Add skcipher documentation. Algorithms: - Rename crypto/crc32 to avoid name clash with lib/crc32. - Fix bug in keywrap where we zero the wrong pointer. Drivers: - Support T5/M5, T7/M7 SPARC CPUs in n2 hwrng driver. - Add PIC32 hwrng driver. - Support BCM6368 in bcm63xx hwrng driver. - Pack structs for 32-bit compat users in qat. - Use crypto engine in omap-aes. - Add support for sama5d2x SoCs in atmel-sha. - Make atmel-sha available again. - Make sahara hashing available again. - Make ccp hashing available again. - Make sha1-mb available again. - Add support for multiple devices in ccp. - Improve DMA performance in caam. - Add hashing support to rockchip" * 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6: (116 commits) crypto: qat - remove redundant arbiter configuration crypto: ux500 - fix checks of error code returned by devm_ioremap_resource() crypto: atmel - fix checks of error code returned by devm_ioremap_resource() crypto: qat - Change the definition of icp_qat_uof_regtype hwrng: exynos - use __maybe_unused to hide pm functions crypto: ccp - Add abstraction for device-specific calls crypto: ccp - CCP versioning support crypto: ccp - Support for multiple CCPs crypto: ccp - Remove check for x86 family and model crypto: ccp - memset request context to zero during import lib/mpi: use "static inline" instead of "extern inline" lib/mpi: avoid assembler warning hwrng: bcm63xx - fix non device tree compatibility crypto: testmgr - allow rfc3686 aes-ctr variants in fips mode. crypto: qat - The AE id should be less than the maximal AE number lib/mpi: Endianness fix crypto: rockchip - add hash support for crypto engine in rk3288 crypto: xts - fix compile errors crypto: doc - add skcipher API documentation crypto: doc - update AEAD AD handling ...
2016-02-08ext4 crypto: revalidate dentry after adding or removing the keyTheodore Ts'o1-0/+56
Add a validation check for dentries for encrypted directory to make sure we're not caching stale data after a key has been added or removed. Also check to make sure that status of the encryption key is updated when readdir(2) is executed. Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2016-01-27ext4: Use skcipherHerbert Xu1-13/+11
This patch replaces uses of ablkcipher with skcipher. Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2015-12-07ext4: provide ext4_issue_zeroout()Jan Kara1-4/+2
Create new function ext4_issue_zeroout() to zeroout contiguous (both logically and physically) part of inode data. We will need to issue zeroout when extent structure is not readily available and this function will allow us to do it without making up fake extent structures. Signed-off-by: Jan Kara <jack@suse.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2015-11-26ext4: fix an endianness bug in ext4_encrypted_zeroout()Al Viro1-1/+1
ex->ee_block is not host-endian (note that accesses of other fields of *ex right next to that line go through the helpers that do proper conversion from little-endian to host-endian; it might make sense to add similar for ->ee_block to avoid reintroducing that kind of bugs...) Cc: stable@vger.kernel.org # v4.1+ Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2015-10-03ext4 crypto: fix bugs in ext4_encrypted_zeroout()Theodore Ts'o1-4/+19
Fix multiple bugs in ext4_encrypted_zeroout(), including one that could cause us to write an encrypted zero page to the wrong location on disk, potentially causing data and file system corruption. Fortunately, this tends to only show up in stress tests, but even with these fixes, we are seeing some test failures with generic/127 --- but these are now caused by data failures instead of metadata corruption. Since ext4_encrypted_zeroout() is only used for some optimizations to keep the extent tree from being too fragmented, and ext4_encrypted_zeroout() itself isn't all that optimized from a time or IOPS perspective, disable the extent tree optimization for encrypted inodes for now. This prevents the data corruption issues reported by generic/127 until we can figure out what's going wrong. Signed-off-by: Theodore Ts'o <tytso@mit.edu> Cc: stable@vger.kernel.org
2015-10-03ext4 crypto: replace some BUG_ON()'s with error checksTheodore Ts'o1-1/+0
Buggy (or hostile) userspace should not be able to cause the kernel to crash. Signed-off-by: Theodore Ts'o <tytso@mit.edu> Cc: stable@vger.kernel.org
2015-10-03ext4 crypto: ext4_page_crypto() doesn't need a encryption contextTheodore Ts'o1-23/+5
Since ext4_page_crypto() doesn't need an encryption context (at least not any more), this allows us to simplify a number function signature and also allows us to avoid needing to allocate a context in ext4_block_write_begin(). It also means we no longer need a separate ext4_decrypt_one() function. Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2015-06-08ext4 crypto: fix ext4_get_crypto_ctx()'s calling convention in ext4_decrypt_oneTheodore Ts'o1-2/+2
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2015-06-03ext4 crypto: allocate bounce pages using GFP_NOWAITTheodore Ts'o1-21/+6
Previously we allocated bounce pages using a combination of alloc_page() and mempool_alloc() with the __GFP_WAIT bit set. Instead, use mempool_alloc() with GFP_NOWAIT. The mempool_alloc() function will try using alloc_pages() initially, and then only use the mempool reserve of pages if alloc_pages() is unable to fulfill the request. This minimizes the the impact on the mm layer when we need to do a large amount of writeback of encrypted files, as Jaeguk Kim had reported that under a heavy fio workload on a system with restricted amounts memory (which unfortunately, includes many mobile handsets), he had observed the the OOM killer getting triggered several times. Using GFP_NOWAIT If the mempool_alloc() function fails, we will retry the page writeback at a later time; the function of the mempool is to ensure that we can writeback at least 32 pages at a time, so we can more efficiently dispatch I/O under high memory pressure situations. In the future we should make this be a tunable so we can determine the best tradeoff between permanently sequestering memory and the ability to quickly launder pages so we can free up memory quickly when necessary. Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2015-05-31ext4 crypto: handle unexpected lack of encryption keysTheodore Ts'o1-1/+2
Fix up attempts by users to try to write to a file when they don't have access to the encryption key. Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2015-05-31ext4 crypto: fix memory leaks in ext4_encrypted_zerooutTheodore Ts'o1-31/+31
ext4_encrypted_zeroout() could end up leaking a bio and bounce page. Fortunately it's not used much. While we're fixing things up, refactor out common code into the static function alloc_bounce_page() and fix up error handling if mempool_alloc() fails. Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2015-05-31ext4 crypto: use per-inode tfm structureTheodore Ts'o1-60/+4
As suggested by Herbert Xu, we shouldn't allocate a new tfm each time we read or write a page. Instead we can use a single tfm hanging off the inode's crypt_info structure for all of our encryption needs for that inode, since the tfm can be used by multiple crypto requests in parallel. Also use cmpxchg() to avoid races that could result in crypt_info structure getting doubly allocated or doubly freed. Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2015-05-31ext4 crypto: shrink size of the ext4_crypto_ctx structureTheodore Ts'o1-21/+10
Some fields are only used when the crypto_ctx is being used on the read path, some are only used on the write path, and some are only used when the structure is on free list. Optimize memory use by using a union. Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2015-05-18ext4 crypto: get rid of ci_mode from struct ext4_crypt_infoTheodore Ts'o1-6/+5
The ci_mode field was superfluous, and getting rid of it gets rid of an unused hole in the structure. Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2015-05-18ext4 crypto: use slab cachesTheodore Ts'o1-31/+29
Use slab caches the ext4_crypto_ctx and ext4_crypt_info structures for slighly better memory efficiency and debuggability. Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2015-05-18ext4 crypto: reorganize how we store keys in the inodeTheodore Ts'o1-4/+5
This is a pretty massive patch which does a number of different things: 1) The per-inode encryption information is now stored in an allocated data structure, ext4_crypt_info, instead of directly in the node. This reduces the size usage of an in-memory inode when it is not using encryption. 2) We drop the ext4_fname_crypto_ctx entirely, and use the per-inode encryption structure instead. This remove an unnecessary memory allocation and free for the fname_crypto_ctx as well as allowing us to reuse the ctfm in a directory for multiple lookups and file creations. 3) We also cache the inode's policy information in the ext4_crypt_info structure so we don't have to continually read it out of the extended attributes. 4) We now keep the keyring key in the inode's encryption structure instead of releasing it after we are done using it to derive the per-inode key. This allows us to test to see if the key has been revoked; if it has, we prevent the use of the derived key and free it. 5) When an inode is released (or when the derived key is freed), we will use memset_explicit() to zero out the derived key, so it's not left hanging around in memory. This implies that when a user logs out, it is important to first revoke the key, and then unlink it, and then finally, to use "echo 3 > /proc/sys/vm/drop_caches" to release any decrypted pages and dcache entries from the system caches. 6) All this, and we also shrink the number of lines of code by around 100. :-) Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2015-05-18ext4 crypto: separate kernel and userspace structure for the keyTheodore Ts'o1-9/+9
Use struct ext4_encryption_key only for the master key passed via the kernel keyring. For internal kernel space users, we now use struct ext4_crypt_info. This will allow us to put information from the policy structure so we can cache it and avoid needing to constantly looking up the extended attribute. We will do this in a spearate patch. This patch is mostly mechnical to make it easier for patch review. Signed-off-by: Theodore Ts'o <tytso@mit.edu>
2015-04-12ext4 crypto: add ext4 encryption facilitiesMichael Halcrow1-0/+558
On encrypt, we will re-assign the buffer_heads to point to a bounce page rather than the control_page (which is the original page to write that contains the plaintext). The block I/O occurs against the bounce page. On write completion, we re-assign the buffer_heads to the original plaintext page. On decrypt, we will attach a read completion callback to the bio struct. This read completion will decrypt the read contents in-place prior to setting the page up-to-date. The current encryption mode, AES-256-XTS, lacks cryptographic integrity. AES-256-GCM is in-plan, but we will need to devise a mechanism for handling the integrity data. Signed-off-by: Michael Halcrow <mhalcrow@google.com> Signed-off-by: Ildar Muslukhov <ildarm@google.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu>