ARC_FLAG_L2_WRITING
#define HDR_L2_WRITING(hdr) ((hdr)->b_flags & ARC_FLAG_L2_WRITING)
arc_hdr_clear_flags(hdr, ARC_FLAG_L2_WRITING);
arc_hdr_set_flags(hdr, ARC_FLAG_L2_WRITING);
ARC_FLAG_L2_WRITING);
ARC_FLAG_L2_WRITING | ARC_FLAG_HAS_L2HDR);