SF_ATTACHPENDING
if (sd->s_flags & SF_ATTACHPENDING) {
sd->s_flags |= SF_ATTACHPENDING;
if (!(sd->s_flags & SF_ATTACHPENDING)) {
sd->s_flags &= ~SF_ATTACHPENDING;
if (!(sd->s_flags & SF_ATTACHPENDING)) {
sd->s_flags &= ~SF_ATTACHPENDING;