On Wed, May 22, 2019 at 10:19:10AM +0200, Johannes Thumshirn wrote:
> Now that we everything in place, we can add SHA-256 as another checksum
> algorithm.
>
> SHA-256 was taken as it was the cryptographically strongest algorithm that
> can fit into the 32 Bytes we have left.
>
> Signed-off-by: Johannes Thumshirn <jthumshirn@xxxxxxx>
>
> ---
> changes to v2:
> - Add pre dependency on sha256
> Changes to v1:
> - Select SHA-256 in KConfig
> - Minimalize switch() in btrfs_supported_super_csum() (Nikolay)
> - Use enum for new on-disk checksum type (Nikolay/David)
> - Format SHA256 using sprintf()'s hexdump mode
> ---
> fs/btrfs/Kconfig | 1 +
> fs/btrfs/btrfs_inode.h | 3 +++
> fs/btrfs/ctree.h | 4 ++--
> fs/btrfs/disk-io.c | 1 +
> fs/btrfs/super.c | 1 +
> include/uapi/linux/btrfs_tree.h | 6 ++++--
> 6 files changed, 12 insertions(+), 4 deletions(-)
>
> diff --git a/fs/btrfs/Kconfig b/fs/btrfs/Kconfig
> index 212b4a854f2c..2521a24f74be 100644
> --- a/fs/btrfs/Kconfig
> +++ b/fs/btrfs/Kconfig
> @@ -4,6 +4,7 @@ config BTRFS_FS
> tristate "Btrfs filesystem support"
> select CRYPTO
> select CRYPTO_CRC32C
> + select CRYPTO_SHA256
> select ZLIB_INFLATE
> select ZLIB_DEFLATE
> select LZO_COMPRESS
> diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h
> index e79fd9129075..125bc7f3b871 100644
> --- a/fs/btrfs/btrfs_inode.h
> +++ b/fs/btrfs/btrfs_inode.h
> @@ -346,6 +346,9 @@ static inline void btrfs_csum_format(struct btrfs_super_block *sb,
> case BTRFS_CSUM_TYPE_CRC32:
> snprintf(cbuf, size, "0x%08x", *(u32 *)csum);
> break;
> + case BTRFS_CSUM_TYPE_SHA256:
> + snprintf(cbuf, size, "%*phN", (int)size / 8, csum);
This seems to print the buffer in the host order ('h', other formats use
that). I wonder if there needs to be some caution about endianity here.
Ideally we won't need to care and just use the right format that will
printk handle transparently for us.
