From mboxrd@z Thu Jan 1 00:00:00 1970 From: Zoltan Kiss Subject: Re: [PATCH net] xen-netback: Fix slot estimation Date: Fri, 06 Jun 2014 11:20:45 +0100 Message-ID: <539195FD.6080606@schaman.hu> References: <1401802336-25182-1-git-send-email-zoltan.kiss@citrix.com> <20140605.150209.365488173138758921.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: xen-devel@lists.xenproject.org, ian.campbell@citrix.com, wei.liu2@citrix.com, paul.durrant@citrix.com, linux@eikelenboom.it, netdev@vger.kernel.org, david.vrabel@citrix.com To: David Miller Return-path: Received: from mail-we0-f172.google.com ([74.125.82.172]:42782 "EHLO mail-we0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751722AbaFFKUs (ORCPT ); Fri, 6 Jun 2014 06:20:48 -0400 Received: by mail-we0-f172.google.com with SMTP id k48so2616971wev.17 for ; Fri, 06 Jun 2014 03:20:47 -0700 (PDT) In-Reply-To: <20140605.150209.365488173138758921.davem@davemloft.net> Sender: netdev-owner@vger.kernel.org List-ID: On 05/06/14 23:02, David Miller wrote: > From: Zoltan Kiss > Date: Tue, 3 Jun 2014 14:32:16 +0100 > >> A recent commit (a02eb4 "xen-netback: worse-case estimate in xenvif_rx_action is >> underestimating") capped the slot estimation to MAX_SKB_FRAGS, but that triggers >> the next BUG_ON a few lines down, as the packet consumes more slots than >> estimated. >> This patch remove that cap, and if the frontend doesn't provide enough slot, >> put back the skb to the top of the queue and caps rx_last_skb_slots. When the >> next try also fails, it drops the packet. >> Capping rx_last_skb_slots is needed because if the frontend never gives enough >> slots, the ring gets stalled. >> >> Signed-off-by: Zoltan Kiss > Like David Laight, I do not like this patch at all. > > Yes a crash or BUG_ON triggered is bad, but fixing it by deadlocking > TCP connections (a silent failure) is not an improvement. > > I'm not applying this, sorry. > Hi, I haven't wrote it explicitly, but my other patch "xen-netback: Fix handling of skbs requiring too many slots" supersedes this one.