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Hi, This is v3 series to add support to btrfs qgroup related commands, inclduing quota commands, and two leftover of subvolume commands. Regards, Hu changes: v3: - don't intialize fs_buf (patch 1) - check the return value of sysroot_path (patch 1) - check fs_buf rather than fs (patch 1) - fprintf (stderr,...) -> reply_with_error() v2: - add tests for new APIs - combine