btrfs: ioctl: return device fsid from DEV_INFO ioctl
Currently user space utilizes dev info ioctl to grab the info of a certain devid, this includes its device uuid. But the returned info is not enough to determine if a device is a seed. Commit a26d60de ("btrfs: sysfs: add devinfo/fsid to retrieve actual fsid from the device") exports the same value in sysfs so this is for parity with ioctl. Add a new member, fsid, into btrfs_ioctl_dev_info_args, and populate the member with fsid value. This should not cause any compatibility problem, following the combinations: - Old user space, old kernel - Old user space, new kernel User space tool won't even check the new member. - New user space, old kernel The kernel won't touch the new member, and user space tool should zero out its argument, thus the new member is all zero. User space tool can then know the kernel doesn't support this fsid reporting, and falls back to whatever they can. - New user space, new kernel Go as planned. Would find the fsid member is no longer zero, and trust its value. Reviewed-by: Anand Jain <anand.jain@oracle.com> Signed-off-by: Qu Wenruo <wqu@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
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