hi,

> Basicly, i've tried to make the nested buffers interface agnostic as much 
> as possible and indifferent to other layers they can be passed to. The 
> buffers can even be brelse()'d or issued with B_ASYNC without a callback; 
> the code will do the right thing. If code uses callbacks they can just 
> brelse() them like it is a normal buffer; no need for special knowledge. 
> This is documented in the source. A patch for manpages is not added yet.

using brelse() for non-buffercache buffers is a bug.

i don't understand what exactly you want to achieve.  can you explain?
to me, it seems that you are going to increase the sizeof(struct buf)
without any benefits.

YAMAMOTO Takashi