Re: block devices don't work without plugging in 2.4.3

[Jens Axboe <axboe@suse.de>]

On Tue, Apr 17 2001, Peter T. Breuer wrote:
> Well, anyway, as far as I can tell, the following has been lost from
> __make_request() in ll_rw_blk.c since the 2.4.0 days:
> 
>  out:
> -       if (!q->plugged)
> -               (q->request_fn)(q);
>         if (freereq)
> 
> The result appears to be that if a block device has called
> blk_queue_pluggable() to register a no-op plug_fn, then
> q->plugged will never be set (it's the duty of the plug_fn),
> and the devices registered request function wil never be called.
> 
> This behaviour is distinct from 2.4.0, where registering a 
> no-op made things work fine.
> 
> Is the policy now supposed to be that we do some more work
> in the "no-op"?  What am I supposed to do if I don't want
> plugging(1)(2)?
> 
> (1) goes away and looks ....
> (2) actually, I do want plugging, but I like to keep the
>     no-plug option around so that I can benchmark the difference
>     and also provide a very conservative option setting.

Not using plugging is dead, blk_queue_pluggable has been killed in the
current 2.4.4-pre tree.

-- 
Jens Axboe