On 6/24/20 5:31 PM, David Sterba wrote:
> 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.
And then quadruplecheck the result, so that it does not end up like
struct btrfs_ioctl_get_dev_stats, 'when adding the flags field' :D
K
