From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753886AbeAZQSS (ORCPT ); Fri, 26 Jan 2018 11:18:18 -0500 Received: from mail-pg0-f68.google.com ([74.125.83.68]:45413 "EHLO mail-pg0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753820AbeAZQSP (ORCPT ); Fri, 26 Jan 2018 11:18:15 -0500 X-Google-Smtp-Source: AH8x2245uDA7wyC5bdsDDyBVyj2o1rgy+shcOb44Dfzy4chZCqBJ3S+zjai+sNwOy/bmda5SoNR3LA== Subject: Re: [PATCH] atm: firestream: Replace GFP_ATOMIC with GFP_KERNEL in fs_send To: David Miller , viro@ZenIV.linux.org.uk Cc: 3chas3@gmail.com, linux-atm-general@lists.sourceforge.net, netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <1516953627-30983-1-git-send-email-baijiaju1990@gmail.com> <20180126120522.GX13338@ZenIV.linux.org.uk> <20180126.110739.419621238821097728.davem@davemloft.net> From: Jia-Ju Bai Message-ID: Date: Sat, 27 Jan 2018 00:17:53 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 In-Reply-To: <20180126.110739.419621238821097728.davem@davemloft.net> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2018/1/27 0:07, David Miller wrote: > From: Al Viro > Date: Fri, 26 Jan 2018 12:05:22 +0000 > >> On Fri, Jan 26, 2018 at 04:00:27PM +0800, Jia-Ju Bai wrote: >>> After checking all possible call chains to fs_send() here, >>> my tool finds that fs_send() is never called in atomic context. >>> And this function is assigned to a function pointer "dev->ops->send", >>> which is only called by vcc_sendmsg() (net/atm/common.c) >>> through vcc->dev->ops->send(), and vcc_sendmsg() calls schedule(), >>> it indicates that fs_send() can call functions which may sleep. >>> Thus GFP_ATOMIC is not necessary, and it can be replaced with GFP_KERNEL. >>> >>> This is found by a static analysis tool named DCNS written by myself. >> The trouble is, places like >> net/atm/raw.c:65: vcc->send = atm_send_aal0; >> net/atm/raw.c:74: vcc->send = vcc->dev->ops->send; >> net/atm/raw.c:83: vcc->send = vcc->dev->ops->send; >> mean extra call chains. It's *not* just vcc_sendmsg(), and e.g. >> ret = ATM_SKB(skb)->vcc->send(ATM_SKB(skb)->vcc, skb) >> ? DROP_PACKET : 1; >> bh_unlock_sock(sk_atm(vcc)); >> in pppoatm_send() definitely is called under a spinlock. >> >> Looking through the driver (in advanced bitrot, as usual for drivers/atm), >> I'd say that submit_queue() is fucked in head in the "queue full" case. >> And judging by the history, had been thus since the original merge... > Jia-Ju, I'm probably not going to apply any of your GFP_KERNEL > conversions. > > Al's analysis above is similar to how things looked for other patches > you submited of this nature. > > So because of the lack of care and serious auditing you put into these > conversions, I really have no choice but to drop them from my queue > because on the whole they are adding bugs rather than improving the > code. > > Thank you. Okay, I can understand that careless GFP_KERNEL conversions will introduce bugs. Your concern is right. Sorry for my previous incorrect patches... I will manually carefully check and audit my patches before I submit them. Thanks, Jia-Ju Bai