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[23.128.96.18]) by mx.google.com with ESMTP id a90si2199383edf.486.2020.07.29.17.31.32; Wed, 29 Jul 2020 17:32:02 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; dkim=fail header.i=@embeddedor.com header.s=default header.b="gd3/GZhD"; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728219AbgG3A21 (ORCPT + 99 others); Wed, 29 Jul 2020 20:28:27 -0400 Received: from gateway20.websitewelcome.com ([192.185.54.2]:31082 "EHLO gateway20.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728053AbgG3A21 (ORCPT ); Wed, 29 Jul 2020 20:28:27 -0400 X-Greylist: delayed 1245 seconds by postgrey-1.27 at vger.kernel.org; Wed, 29 Jul 2020 20:28:26 EDT Received: from cm10.websitewelcome.com (cm10.websitewelcome.com [100.42.49.4]) by gateway20.websitewelcome.com (Postfix) with ESMTP id 3AAAB40515241 for ; Wed, 29 Jul 2020 17:44:15 -0500 (CDT) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id 0w5fkCwuSRQIV0w5fkeyFv; Wed, 29 Jul 2020 19:06:31 -0500 X-Authority-Reason: nr=8 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=embeddedor.com; s=default; h=Content-Transfer-Encoding:Content-Type: In-Reply-To:MIME-Version:Date:Message-ID:Subject:From:References:Cc:To:Sender :Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help: List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=O9pd5wZFyMlo2KIw2w7Jr68x5gB033RYBnB9J5fYDs8=; b=gd3/GZhDMc/bVV0PV5dtEt3bWR EMH5E0gwCIB5xwWmdRUGdRutDmV5ckeKvscXTN6jlaVrfbzSTLtnVdo0O7dbeNVCDfkjydN5ktvvw lcl982UJNymyU2OKDizVuZwZCcveNsgCLq+c5XytdvZxnx6CeHVD2VgOyJkg0bBCvCTYvzA4GsaaA WoiPJS3LD+K3NC58oCl8EYiTuFxkTv9Ea7loz+9F36IcZyqr8PBouVL4IaE1GQ8aL7xF60WTVNa/H l1u9u+wEd/NCPQ704rbRxP8I8+EvLELU0r8JHKSVo1DgKixKUgMo0etiJscBj+CrbL7fjqJ97PT5v 78BmJkuQ==; Received: from 187-162-31-110.static.axtel.net ([187.162.31.110]:51790 helo=[192.168.15.3]) by gator4166.hostgator.com with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.93) (envelope-from ) id 1k0w5f-0031yi-A5; Wed, 29 Jul 2020 19:06:31 -0500 To: Qianli Zhao , cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com, zhaoqianli@xiaomi.com References: <1596034214-15010-1-git-send-email-zhaoqianligood@gmail.com> From: "Gustavo A. R. Silva" Autocrypt: addr=gustavo@embeddedor.com; keydata= xsFNBFssHAwBEADIy3ZoPq3z5UpsUknd2v+IQud4TMJnJLTeXgTf4biSDSrXn73JQgsISBwG 2Pm4wnOyEgYUyJd5tRWcIbsURAgei918mck3tugT7AQiTUN3/5aAzqe/4ApDUC+uWNkpNnSV tjOx1hBpla0ifywy4bvFobwSh5/I3qohxDx+c1obd8Bp/B/iaOtnq0inli/8rlvKO9hp6Z4e DXL3PlD0QsLSc27AkwzLEc/D3ZaqBq7ItvT9Pyg0z3Q+2dtLF00f9+663HVC2EUgP25J3xDd 496SIeYDTkEgbJ7WYR0HYm9uirSET3lDqOVh1xPqoy+U9zTtuA9NQHVGk+hPcoazSqEtLGBk YE2mm2wzX5q2uoyptseSNceJ+HE9L+z1KlWW63HhddgtRGhbP8pj42bKaUSrrfDUsicfeJf6 m1iJRu0SXYVlMruGUB1PvZQ3O7TsVfAGCv85pFipdgk8KQnlRFkYhUjLft0u7CL1rDGZWDDr NaNj54q2CX9zuSxBn9XDXvGKyzKEZ4NY1Jfw+TAMPCp4buawuOsjONi2X0DfivFY+ZsjAIcx qQMglPtKk/wBs7q2lvJ+pHpgvLhLZyGqzAvKM1sVtRJ5j+ARKA0w4pYs5a5ufqcfT7dN6TBk LXZeD9xlVic93Ju08JSUx2ozlcfxq+BVNyA+dtv7elXUZ2DrYwARAQABzStHdXN0YXZvIEEu IFIuIFNpbHZhIDxndXN0YXZvYXJzQGtlcm5lbC5vcmc+wsGrBBMBCAA+FiEEkmRahXBSurMI g1YvRwW0y0cG2zEFAl6zFvQCGyMFCQlmAYAFCwkIBwIGFQoJCAsCBBYCAwECHgECF4AAIQkQ RwW0y0cG2zEWIQSSZFqFcFK6swiDVi9HBbTLRwbbMZsEEACWjJyXLjtTAF21Vuf1VDoGzitP oE69rq9UhXIGR+e0KACyIFoB9ibG/1j/ESMa0RPSwLpJDLgfvi/I18H/9cKtdo2uz0XNbDT8 i3llIu0b43nzGIDzRudINBXC8Coeob+hrp/MMZueyzt0CUoAnY4XqpHQbQsTfTrpFeHT02Qz ITw6kTSmK7dNbJj2naH2vSrU11qGdU7aFzI7jnVvGgv4NVQLPxm/t4jTG1o+P1Xk4N6vKafP zqzkxj99JrUAPt+LyPS2VpNvmbSNq85PkQ9gpeTHpkio/D9SKsMW62njITPgy6M8TFAmx8JF ZAI6k8l1eU29F274WnlQ6ZokkJoNctwHa+88euWKHWUDolCmQpegJJ8932www83GLn1mdUZn NsymjFSdMWE+y8apWaV9QsDOKWf7pY2uBuE6GMPRhX7e7h5oQwa1lYeO2L9LTDeXkEOJe+hE qQdEEvkC/nok0eoRlBlZh433DQlv4+IvSsfN/uWld2TuQFyjDCLIm1CPRfe7z0TwiCM27F+O lHnUspCFSgpnrxqNH6CM4aj1EF4fEX+ZyknTSrKL9BGZ/qRz7Xe9ikU2/7M1ov6rOXCI4NR9 THsNax6etxCBMzZs2bdMHMcajP5XdRsOIARuN08ytRjDolR2r8SkTN2YMwxodxNWWDC3V8X2 RHZ4UwQw487BTQRbLBwMARAAsHCE31Ffrm6uig1BQplxMV8WnRBiZqbbsVJBH1AAh8tq2ULl 7udfQo1bsPLGGQboJSVN9rckQQNahvHAIK8ZGfU4Qj8+CER+fYPp/MDZj+t0DbnWSOrG7z9H IZo6PR9z4JZza3Hn/35jFggaqBtuydHwwBANZ7A6DVY+W0COEU4of7CAahQo5NwYiwS0lGis LTqks5R0Vh+QpvDVfuaF6I8LUgQR/cSgLkR//V1uCEQYzhsoiJ3zc1HSRyOPotJTApqGBq80 X0aCVj1LOiOF4rrdvQnj6iIlXQssdb+WhSYHeuJj1wD0ZlC7ds5zovXh+FfFl5qH5RFY/qVn 3mNIVxeO987WSF0jh+T5ZlvUNdhedGndRmwFTxq2Li6GNMaolgnpO/CPcFpDjKxY/HBUSmaE 9rNdAa1fCd4RsKLlhXda+IWpJZMHlmIKY8dlUybP+2qDzP2lY7kdFgPZRU+ezS/pzC/YTzAv CWM3tDgwoSl17vnZCr8wn2/1rKkcLvTDgiJLPCevqpTb6KFtZosQ02EGMuHQI6Zk91jbx96n rdsSdBLGH3hbvLvjZm3C+fNlVb9uvWbdznObqcJxSH3SGOZ7kCHuVmXUcqozol6ioMHMb+In rHPP16aVDTBTPEGwgxXI38f7SUEn+NpbizWdLNz2hc907DvoPm6HEGCanpcAEQEAAcLBZQQY AQgADwUCWywcDAIbDAUJCWYBgAAKCRBHBbTLRwbbMdsZEACUjmsJx2CAY+QSUMebQRFjKavw XB/xE7fTt2ahuhHT8qQ/lWuRQedg4baInw9nhoPE+VenOzhGeGlsJ0Ys52sdXvUjUocKgUQq 6ekOHbcw919nO5L9J2ejMf/VC/quN3r3xijgRtmuuwZjmmi8ct24TpGeoBK4WrZGh/1hAYw4 ieARvKvgjXRstcEqM5thUNkOOIheud/VpY+48QcccPKbngy//zNJWKbRbeVnimua0OpqRXhC rEVm/xomeOvl1WK1BVO7z8DjSdEBGzbV76sPDJb/fw+y+VWrkEiddD/9CSfgfBNOb1p1jVnT 2mFgGneIWbU0zdDGhleI9UoQTr0e0b/7TU+Jo6TqwosP9nbk5hXw6uR5k5PF8ieyHVq3qatJ 9K1jPkBr8YWtI5uNwJJjTKIA1jHlj8McROroxMdI6qZ/wZ1ImuylpJuJwCDCORYf5kW61fcr HEDlIvGc371OOvw6ejF8ksX5+L2zwh43l/pKkSVGFpxtMV6d6J3eqwTafL86YJWH93PN+ZUh 6i6Rd2U/i8jH5WvzR57UeWxE4P8bQc0hNGrUsHQH6bpHV2lbuhDdqo+cM9ehGZEO3+gCDFmK rjspZjkJbB5Gadzvts5fcWGOXEvuT8uQSvl+vEL0g6vczsyPBtqoBLa9SNrSVtSixD1uOgyt AP7RWS474w== Subject: Re: [PATCH] mm: slab: Avoid the use of one-element array and use struct_size() helper Message-ID: <90b2c9f3-cc2b-b2e6-51ef-998d2f79123a@embeddedor.com> Date: Wed, 29 Jul 2020 19:12:31 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.8.0 MIME-Version: 1.0 In-Reply-To: <1596034214-15010-1-git-send-email-zhaoqianligood@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - gator4166.hostgator.com X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - embeddedor.com X-BWhitelist: no X-Source-IP: 187.162.31.110 X-Source-L: No X-Exim-ID: 1k0w5f-0031yi-A5 X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: 187-162-31-110.static.axtel.net ([192.168.15.3]) [187.162.31.110]:51790 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 8 X-Source-Cap: Z3V6aWRpbmU7Z3V6aWRpbmU7Z2F0b3I0MTY2Lmhvc3RnYXRvci5jb20= X-Local-Domain: yes Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, If you are going to copy/paste this, please at least CC the people that is originally working on these changes, in this case _me_. One needs to be very careful when doing these transformations. This code doesn't even exist in linux-next. If you want to land your first kernel patch, I encourage you to start in drivers/staging/, while you get the hang of the kernel development process and you know how to work with linux-next. :) Thanks -- Gustavo On 7/29/20 09:50, Qianli Zhao wrote: > From: Qianli Zhao > > There is a regular need in the kernel to provide a way to declare having a > dynamically sized set of trailing elements in a structure. Kernel code should > always use “flexible array members”[1] for these cases. The older style of > one-element or zero-length arrays should no longer be used[2]. > > Make use of the struct_size() helper instead of an open-coded version > in order to avoid any potential type mistakes. > > [1] https://en.wikipedia.org/wiki/Flexible_array_member > [2] https://github.com/KSPP/linux/issues/21 > > Signed-off-by: Qianli Zhao > --- > mm/slab.h | 2 +- > mm/slab_common.c | 7 ++----- > 2 files changed, 3 insertions(+), 6 deletions(-) > > diff --git a/mm/slab.h b/mm/slab.h > index 74f7e09..c12fb65 100644 > --- a/mm/slab.h > +++ b/mm/slab.h > @@ -34,7 +34,7 @@ struct kmem_cache { > > struct memcg_cache_array { > struct rcu_head rcu; > - struct kmem_cache *entries[0]; > + struct kmem_cache *entries[]; > }; > > /* > diff --git a/mm/slab_common.c b/mm/slab_common.c > index fe8b684..56f4818 100644 > --- a/mm/slab_common.c > +++ b/mm/slab_common.c > @@ -166,9 +166,7 @@ static int init_memcg_params(struct kmem_cache *s, > if (!memcg_nr_cache_ids) > return 0; > > - arr = kvzalloc(sizeof(struct memcg_cache_array) + > - memcg_nr_cache_ids * sizeof(void *), > - GFP_KERNEL); > + arr = kvzalloc(struct_size(arr, entries, memcg_nr_cache_ids), GFP_KERNEL); > if (!arr) > return -ENOMEM; > > @@ -199,8 +197,7 @@ static int update_memcg_params(struct kmem_cache *s, int new_array_size) > { > struct memcg_cache_array *old, *new; > > - new = kvzalloc(sizeof(struct memcg_cache_array) + > - new_array_size * sizeof(void *), GFP_KERNEL); > + new = kvzalloc(struct_size(new, entries, new_array_size), GFP_KERNEL); > if (!new) > return -ENOMEM; > >