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Dear folks,

i've been fighting struct buf{} again and really the whole buf system needs 
a spanking... its uses are so diverse and its getting such a clutter IMHO. 
This time i was bitten by the fact that biodone() unlike physio() doesn't 
use a workqueue and gets called from interrupt context(!)

Would it be good to inventarise the uses of struct buf and come up with a 
more clean solution? I've seen it use for :
	- buffer cache, i.e. caching data
	- passing of data to device driver
	- using the B_CALL as initiator of new actions when one finishes 
	  (cgd f.e.)
	- splitting up a request using nestiobuf() (and B_CALL)
	- providing a vehicle to have multiple callbacks/contexts using 
	  nestiobuf's B_CALL
	- counting of pending actions
	- ....

I think its better to split the functions up:
	- buffering of metadata (also proven to work fine with UBC (see 
	  UDF))
	- passing of data to drivers (getiobuf() was initial start of this)
	- nested buffer for splitting up a request.
	- all finished bufs ought to called back on a kthread (workqueue 
	  like in physio())
	- call back queueing, a TAILQ() of functions with private data 
	  pointer? with an abort function to prevent further calling?
	- adding of pending/finished callbacks counters? (clustering of 
	  reads/writes)
	- .....

Implementing changes to struct buf{} is indeed difficult due to the many, 
many uses but the current situation gets more and more out-of-control.

With regards,
Reinoud


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