MSDOSFSMNT_RONLY
if (!(pmp->pm_flags & MSDOSFSMNT_RONLY) &&
pmp->pm_flags |= MSDOSFSMNT_RONLY;
if ((pmp->pm_flags & MSDOSFSMNT_RONLY) &&
pmp->pm_flags &= ~MSDOSFSMNT_RONLY;
pmp->pm_flags |= MSDOSFSMNT_RONLY;
pmp->pm_flags & MSDOSFSMNT_RONLY ? FREAD : FREAD|FWRITE, NOCRED, p);
if (pmp->pm_flags & MSDOSFSMNT_RONLY)
pmp->pm_flags |= MSDOSFSMNT_RONLY;