Make btrfs use the library APIs instead of crypto_shash, for all
checksum computations. This has many benefits:
- Allows future checksum types, e.g. XXH3 or CRC64, to be more easily
supported. Only a library API will be needed, not crypto_shash too.
- Eliminates the overhead of the generic crypto layer, including an
indirect call for every function call and other API overhead. A
microbenchmark of btrfs_check_read_bio() with crc32c checksums shows a
speedup from 658 cycles to 608 cycles per 4096-byte block.
- Decreases the stack usage of btrfs by reducing the size of checksum
contexts from 384 bytes to 240 bytes, and by eliminating the need for
some functions to declare a checksum context at all.
- Increases reliability. The library functions always succeed and
return void. In contrast, crypto_shash can fail and return errors.
Also, the library functions are guaranteed to be available when btrfs
is loaded; there's no longer any need to use module softdeps to try to
work around the crypto modules sometimes not being loaded.
- Fixes a bug where blake2b checksums didn't work on kernels booted with
fips=1. Since btrfs checksums are for integrity only, it's fine for
them to use non-FIPS-approved algorithms.
Note that with having to handle 4 algorithms instead of just 1-2, this
commit does result in a slightly positive diffstat. That being said,
this wouldn't have been the case if btrfs had actually checked for
errors from crypto_shash, which technically it should have been doing.
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Neal Gompa <neal@gompa.dev>
Signed-off-by: Eric Biggers <ebiggers@kernel.org>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
fe11ac191c