Re: [RFC,PATCH 8/14] knfsd: centralise SK_CLOSE handling

[Greg Banks <gnb@sgi.com>]

On Thu, May 17, 2007 at 08:59:18PM +1000, Neil Brown wrote:
> On Thursday May 17, gnb@sgi.com wrote:
> > 
> > Centralise the handling of the SK_CLOSE bit to that future
> > sunrpc server transport implementations will be easier to
> > write correctly.  The bit should now not be manipulated
> > directly, inline exist to wrap that.  Also, the sko_recvfrom
> > method does not need to check for SK_CLOSE anymore, that's
> > handled in core code.
> ...
> >  
> >  		if (svsk) {
> > -			svc_sock_enqueue(svsk);
> > +			/*
> > +			 * We're always called in nfsd context so we
> > +			 * don't have to muck around with SK_CLOSE.
> > +			 */
> > +			svc_delete_socket(svsk);
> >  			svc_sock_put(svsk);
> >  		}
> 
> I'm not convinced that this is right.  

I believe it is right, but I'll admit it's not obvious enough ;-)

> svc_delete_socket has a comment:
> 	/*
> 	 * We used to delete the svc_sock from whichever list
> 	 * it's sk_ready node was on, but we don't actually
> 	 * need to.  This is because the only time we're called
> 	 * while still attached to a queue, the queue itself
> 	 * is about to be destroyed (in svc_destroy).
> 	 */
> and I think this change invalidate the premise of that comment.

The hunk above, which now calls svc_delete_socket() directly,
is in svc_tcp_accept(), which is only ever called from svc_recv()
*after* the svc_sock has been dequeued from the pool.  At this
point the svc_sock is not attached to a queue by sk_ready.  So
the premise of the comment is still valid.

I'll improve the comment to read:

			/*
			 * We're always called in nfsd context when not
			 * attached to a queue by sk_ready, so can call
			 * svc_delete_socket() directly and not have to
			 * muck around with SK_CLOSE.
			 */


BTW, I have a patch that moves that code out of svc_tcp_accept()
into more generic code, so that RDMA connection transports are also
subject to a connection limit.  Coming soon.

Greg.
-- 
Greg Banks, R&D Software Engineer, SGI Australian Software Group.
Apparently, I'm Bedevere.  Which MPHG character are you?
I don't speak for SGI.

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