mount -u -r drops nosuid ?

[Andriy Gapon]

Not sure if this is a bug or a feature, but it seems like potential
security risk: I have a ufs fs mounted rw+nosuid, then I needed to
downgrade it to ro, so I executed mount -u -r on it - imagine my surpise
when I found that nosuid flag was removed as well. I know I could have
used mount -u -r -o nosuid, but the present behavior seems to be
non-obvious (update one flag, orthogonal flags dropped as well) and
dangerously so.

System is 5.4-RELEASE-p3 i386

-- 
Andriy Gapon