umount of md hangs

[Thomas Quinot]

When I try to make a CompactFlash image with the Nanobsd scripts
(from src/tools/tools/nanobsd), everyghint goes well up to the moment
where, having filled the (vnode-backed) md, the script tries to umount
it, at which point the umount process hangs in wdrain, and the system
slowly crawls to a halt as more processes get blocked too.

This is a 5.2.1-REL-p5 box. Does this problem ring any bell? Any further
info I can provide.

Thomas.

-- 
    Thomas.Quinot at Cuivre.FR.EU.ORG