On Wed, Jun 24, 2020 at 07:21:36PM +0900, Johannes Thumshirn wrote:
> With the recent addition of filesystem checksum types other than CRC32c,
> it is not anymore hard-coded which checksum type a btrfs filesystem uses.
>
> Up to now there is no good way to read the filesystem checksum, apart from
> reading the filesystem UUID and then query sysfs for the checksum type.
>
> Add a new csum_type field to the BTRFS_IOC_FS_INFO ioctl command which
> usually is used to query filesystem features. Also add a flags member
> indicating that the kernel responded with a set csum_type field.
>
> Fixes: 3951e7f050ac ("btrfs: add xxhash64 to checksumming algorithms")
> Fixes: 3831bf0094ab ("btrfs: add sha256 to checksumming algorithm")
> Signed-off-by: Johannes Thumshirn <johannes.thumshirn@xxxxxxx>
> ---
> fs/btrfs/ioctl.c | 3 +++
> include/uapi/linux/btrfs.h | 13 ++++++++++++-
> 2 files changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index b3e4c632d80c..16062720f5f3 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -3217,6 +3217,9 @@ static long btrfs_ioctl_fs_info(struct btrfs_fs_info *fs_info,
> fi_args->nodesize = fs_info->nodesize;
> fi_args->sectorsize = fs_info->sectorsize;
> fi_args->clone_alignment = fs_info->sectorsize;
> + fi_args->csum_type =
> + le16_to_cpu(btrfs_super_csum_type(fs_info->super_copy));
> + fi_args->flags |= BTRFS_FS_INFO_FLAG_CSUM_TYPE;
>
> if (copy_to_user(arg, fi_args, sizeof(*fi_args)))
> ret = -EFAULT;
> diff --git a/include/uapi/linux/btrfs.h b/include/uapi/linux/btrfs.h
> index e6b6cb0f8bc6..161d9100c2a6 100644
> --- a/include/uapi/linux/btrfs.h
> +++ b/include/uapi/linux/btrfs.h
> @@ -250,10 +250,21 @@ struct btrfs_ioctl_fs_info_args {
> __u32 nodesize; /* out */
> __u32 sectorsize; /* out */
> __u32 clone_alignment; /* out */
> + __u32 flags; /* out */
> + __u16 csum_type;
> + __u16 reserved16;
> __u32 reserved32;
> - __u64 reserved[122]; /* pad to 1k */
> + __u64 reserved[121]; /* pad to 1k */
Maybe we should just switch to u8 for the reserved field.
