Re: [PATCH] iSeries virtual disk

[Jeff Garzik <jgarzik@pobox.com>]

Stephen Rothwell wrote:
> On Thu, 26 Feb 2004 02:29:26 -0500 Jeff Garzik <jgarzik@pobox.com> wrote:
>>2) num_req_outstanding accessed without lock in do_viodasd_request 
>>(driver's request_fn).  all other accesses are inside spinlock.
> 
> 
> This is actually OK because:
> 	1) if we see a value too large, when it get decremented by
> 	handle_read_write, all the queue requst functions will get rerun.
> 	2) in send_request, if we get an error and decrement the count
> 	to zero, then the count could have been at most 1 (sonce sends
> 	are serialised) so in the request funtion, we would not have
> 	stopped processing requests.

That doesn't solve the race though...  IMO protect it with the spinlock 
and be done with it...


>>5) is it really OK to call viodasd_open() and viodasd_release() multiple 
>>times?  These functions do not look guarded against multiple openers.
> 
> 
> It is OK.

I need more explanation than that.

Multiple openers _are_ supported at the block layer, and this driver 
does not guard against multiple openers.

Thanks,

	Jeff