Re: kern/38892: msdosfs panic

[Tom Spindler <dogcow%babymeat.com@localhost>]

To summarize the current state of investigation, AFAICT:
<20080616155344.GA5467%aardappel.13thmonkey.org@localhost> on tech-kern
points out that the getblk() semantics changed so that it's possible
for it to return NULL. (This change was made around Jan-Feb by ad.)

Around 15 May, hannken made a bunch of changes to msdosfs and friends
to change the semantics of bread; at that time, sys/kern/vfs_bio.c was
also changed to add a bunch of KASSERT()s. One of the asserts is the
        bp->b_vp == NULL || bp->b_vp->v_tag != VT_UFS ||
            ISSET(bp->b_flags, B_COWDONE)
one that's actually causing the panics. Why UFS gets special treatment,
I don't know.