1. 04 Jun, 2023 1 commit
    • Eric Biggers's avatar
      fsverity: use shash API instead of ahash API · 8fcd94ad
      Eric Biggers authored
      The "ahash" API, like the other scatterlist-based crypto APIs such as
      "skcipher", comes with some well-known limitations.  First, it can't
      easily be used with vmalloc addresses.  Second, the request struct can't
      be allocated on the stack.  This adds complexity and a possible failure
      point that needs to be worked around, e.g. using a mempool.
      
      The only benefit of ahash over "shash" is that ahash is needed to access
      traditional memory-to-memory crypto accelerators, i.e. drivers/crypto/.
      However, this style of crypto acceleration has largely fallen out of
      favor and been superseded by CPU-based acceleration or inline crypto
      engines.  Also, ahash needs to be used asynchronously to take full
      advantage of such hardware, but fs/verity/ has never done this.
      
      On all systems that aren't actually using one of these ahash-only crypto
      accelerators, ahash just adds unnecessary overhead as it sits between
      the user and the underlying shash algorithms.
      
      Also, XFS is planned to cache fsverity Merkle tree blocks in the
      existing XFS buffer cache.  As a result, it will be possible for a
      single Merkle tree block to be split across discontiguous pages
      (https://lore.kernel.org/r/20230405233753.GU3223426@dread.disaster.area).
      This data will need to be hashed.  It is easiest to work with a vmapped
      address in this case.  However, ahash is incompatible with this.
      
      Therefore, let's convert fs/verity/ from ahash to shash.  This
      simplifies the code, and it should also slightly improve performance for
      everyone who wasn't actually using one of these ahash-only crypto
      accelerators, i.e. almost everyone (or maybe even everyone)!
      
      Link: https://lore.kernel.org/r/20230516052306.99600-1-ebiggers@kernel.orgReviewed-by: default avatarChristoph Hellwig <hch@lst.de>
      Acked-by: default avatarArd Biesheuvel <ardb@kernel.org>
      Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
      8fcd94ad
  2. 14 May, 2023 13 commits
  3. 13 May, 2023 17 commits
  4. 12 May, 2023 9 commits