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[66.187.233.206]) by smtp.gmail.com with ESMTPSA id z1sm15011603qke.122.2019.07.19.14.47.52 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 19 Jul 2019 14:47:53 -0700 (PDT) Message-ID: <1563572871.11067.2.camel@lca.pw> Subject: Re: [PATCH] be2net: fix adapter->big_page_size miscaculation From: Qian Cai To: David Miller Cc: morbo@google.com, ndesaulniers@google.com, jyknight@google.com, sathya.perla@broadcom.com, ajit.khaparde@broadcom.com, sriharsha.basavapatna@broadcom.com, somnath.kotur@broadcom.com, arnd@arndb.de, dhowells@redhat.com, hpa@zytor.com, netdev@vger.kernel.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, natechancellor@gmail.com Date: Fri, 19 Jul 2019 17:47:51 -0400 In-Reply-To: <20190718.162928.124906203979938369.davem@davemloft.net> References: <75B428FC-734C-4B15-B1A7-A3FC5F9F2FE5@lca.pw> <20190718.162928.124906203979938369.davem@davemloft.net> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.22.6 (3.22.6-10.el7) Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2019-07-18 at 16:29 -0700, David Miller wrote: > From: Qian Cai > Date: Thu, 18 Jul 2019 19:26:47 -0400 > > >  > >  > >> On Jul 18, 2019, at 5:21 PM, Bill Wendling wrote: > >>  > >> [My previous response was marked as spam...] > >>  > >> Top-of-tree clang says that it's const: > >>  > >> $ gcc a.c -O2 && ./a.out > >> a is a const. > >>  > >> $ clang a.c -O2 && ./a.out > >> a is a const. > >  > >  > > I used clang-7.0.1. So, this is getting worse where both GCC and clang will > start to suffer the > > same problem. > > Then rewrite the module parameter macros such that the non-constness > is evident to all compilers regardless of version. > > That is the place to fix this, otherwise we will just be adding hacks > all over the place rather than in just one spot. The problem is that when the compiler is compiling be_main.o, it has no knowledge about what is going to happen in load_module(). The compiler can only see that a "const struct kernel_param_ops" "__param_ops_rx_frag_size" at the time with __param_ops_rx_frag_size.arg = &rx_frag_size but only in load_module()->parse_args()->parse_one()->param_set_ushort(), it changes "__param_ops_rx_frag_size.arg" which in-turn changes the value of "rx_frag_size".