From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jarek Poplawski Subject: Re: [PATCH 00/11] DMA sync errors Date: Thu, 21 Jan 2010 12:44:23 +0000 Message-ID: <20100121124423.GA8817@ff.dom.local> References: <20100120204459.820265084@vyatta.com> <20100120.144639.31770545.davem@davemloft.net> <20100120152832.06a905a5@nehalam> <20100120.161805.118613816.davem@davemloft.net> <20100120163410.774f0c4c@nehalam> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: David Miller , netdev@vger.kernel.org To: Stephen Hemminger Return-path: Received: from mail-fx0-f220.google.com ([209.85.220.220]:54422 "EHLO mail-fx0-f220.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752164Ab0AUMo2 (ORCPT ); Thu, 21 Jan 2010 07:44:28 -0500 Received: by fxm20 with SMTP id 20so1270555fxm.1 for ; Thu, 21 Jan 2010 04:44:27 -0800 (PST) Content-Disposition: inline In-Reply-To: <20100120163410.774f0c4c@nehalam> Sender: netdev-owner@vger.kernel.org List-ID: On Wed, Jan 20, 2010 at 04:34:10PM -0800, Stephen Hemminger wrote: > On Wed, 20 Jan 2010 16:18:05 -0800 (PST) > David Miller wrote: > > > From: Stephen Hemminger > > Date: Wed, 20 Jan 2010 15:28:32 -0800 > > > > > This should fix the dma-debug API code (and documentation), to > > > avoid false positives when sync is done on a partial map. > > > > > > Signed-off-by: Stephen Hemminger > > ... > > > --- a/lib/dma-debug.c 2010-01-20 15:22:55.919519883 -0800 > > > +++ b/lib/dma-debug.c 2010-01-20 15:26:31.648895638 -0800 > > > @@ -285,11 +285,9 @@ static struct dma_debug_entry *hash_buck > > > } > > > > > > /* > > > - * If we have multiple matches but no perfect-fit, just return > > > - * NULL. > > > + * If we have multiple matches but no perfect-fit > > > + * return best value and let caller deal with it. > > > */ > > > - ret = (matches == 1) ? ret : NULL; > > > - > > > return ret; > > > } > > > > > > > I think you have to enforce a perfect-fit match for the > > non-SYNC cases. > > > > check_sync() can pass in 'true' for a new bool argument "partial_ok" > > added to hash_bucket_find() whereas check_unmap() can pass 'false'. > > > > get_nr_mapped_entries() should pass 'false' as well. > > check_unmap has checks for different size, different type, > call_ents, direction etc. > > The code for get_nr_mapped_entries() is the only question; > it is used by unmap_sg() and probably needs perfect match only. > Hmm... After looking at it more, mainly dma_sync_single_range() implementations, I didn't find any reasons for these comments in DMA-API.txt, but even if I missed something, this patch definitely shows these lib/dma-debug warnings are buggy if they depend on the number of mapped entries (while otherwise ref->size < entry->size isn't reported). Btw, it seems code should try to return minimum entry->size for such a check. Thanks Stephen, now I feel 99.9% safe ;-) Sorry for mistrust, David! Jarek P.