From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ed1-f72.google.com (mail-ed1-f72.google.com [209.85.208.72]) by kanga.kvack.org (Postfix) with ESMTP id 5AF688E0038 for ; Tue, 8 Jan 2019 09:52:48 -0500 (EST) Received: by mail-ed1-f72.google.com with SMTP id v4so1678957edm.18 for ; Tue, 08 Jan 2019 06:52:48 -0800 (PST) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id 24si29696edu.308.2019.01.08.06.52.46 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 08 Jan 2019 06:52:47 -0800 (PST) Date: Tue, 8 Jan 2019 15:52:45 +0100 From: Michal Hocko Subject: Re: [PATCH] mm: memcontrol: use struct_size() in kmalloc() Message-ID: <20190108145245.GW31793@dhcp22.suse.cz> References: <20190104183726.GA6374@embeddedor> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190104183726.GA6374@embeddedor> Sender: owner-linux-mm@kvack.org List-ID: To: "Gustavo A. R. Silva" Cc: Johannes Weiner , Vladimir Davydov , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton Cc Andrew (original patch is here http://lkml.kernel.org/r/20190104183726.GA6374@embeddedor) On Fri 04-01-19 12:37:26, Gustavo A. R. Silva wrote: > One of the more common cases of allocation size calculations is finding > the size of a structure that has a zero-sized array at the end, along > with memory for some number of elements for that array. For example: > > struct foo { > int stuff; > void *entry[]; > }; > > instance = kmalloc(sizeof(struct foo) + sizeof(void *) * count, GFP_KERNEL); > > Instead of leaving these open-coded and prone to type mistakes, we can > now use the new struct_size() helper: > > instance = kmalloc(struct_size(instance, entry, count), GFP_KERNEL); This looks indeed neater > This code was detected with the help of Coccinelle. > > Signed-off-by: Gustavo A. R. Silva Acked-by: Michal Hocko Thanks > --- > mm/memcontrol.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index af7f18b32389..ad256cf7da47 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -3626,8 +3626,7 @@ static int __mem_cgroup_usage_register_event(struct mem_cgroup *memcg, > size = thresholds->primary ? thresholds->primary->size + 1 : 1; > > /* Allocate memory for new array of thresholds */ > - new = kmalloc(sizeof(*new) + size * sizeof(struct mem_cgroup_threshold), > - GFP_KERNEL); > + new = kmalloc(struct_size(new, entries, size), GFP_KERNEL); > if (!new) { > ret = -ENOMEM; > goto unlock; > -- > 2.20.1 -- Michal Hocko SUSE Labs