From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1947148AbcHRKwX (ORCPT ); Thu, 18 Aug 2016 06:52:23 -0400 Received: from mx01-fr.bfs.de ([193.174.231.67]:16151 "EHLO mx01-fr.bfs.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1945918AbcHRKwQ (ORCPT ); Thu, 18 Aug 2016 06:52:16 -0400 Message-ID: <57B5935B.3050602@bfs.de> Date: Thu, 18 Aug 2016 12:52:11 +0200 From: walter harms Reply-To: wharms@bfs.de User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; de; rv:1.9.1.16) Gecko/20101125 SUSE/3.0.11 Thunderbird/3.0.11 MIME-Version: 1.0 To: Paolo Bonzini CC: Julia Lawall , SF Markus Elfring , kvm@vger.kernel.org, linux-s390@vger.kernel.org, =?UTF-8?B?Q2hyaXN0aWFuIA==?= =?UTF-8?B?Qm9ybnRyw6RnZXI=?= , Cornelia Huck , David Hildenbrand , Heiko Carstens , Martin Schwidefsky , =?UTF-8?B?UmFkaW0gS3LEjW3DoQ==?= =?UTF-8?B?xZk=?= , LKML , kernel-janitors@vger.kernel.org Subject: Re: [PATCH 1/4] KVM-S390: Improve determination of sizes in kvm_s390_import_bp_data() References: <82b84c9c-38a4-4d17-910f-312668dbae01@users.sourceforge.net> <033d8595-d051-1fa8-95b1-5d2056eb5667@users.sourceforge.net> <57B562F3.1080004@bfs.de> <9db1986a-9b93-72ca-f35e-85b5b5e9f351@redhat.com> In-Reply-To: <9db1986a-9b93-72ca-f35e-85b5b5e9f351@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 18.08.2016 11:48, schrieb Paolo Bonzini: > > > On 18/08/2016 11:02, Julia Lawall wrote: >> >> >> On Thu, 18 Aug 2016, walter harms wrote: >> >>> >>> >>> Am 17.08.2016 20:06, schrieb SF Markus Elfring: >>>> From: Markus Elfring >>>> Date: Wed, 17 Aug 2016 18:29:04 +0200 >>>> >>>> Replace the specification of data structures by pointer dereferences >>>> to make the corresponding size determination a bit safer according to >>>> the Linux coding style convention. >>>> >>>> Signed-off-by: Markus Elfring >>>> --- >>>> arch/s390/kvm/guestdbg.c | 6 +++--- >>>> 1 file changed, 3 insertions(+), 3 deletions(-) >>>> >>>> diff --git a/arch/s390/kvm/guestdbg.c b/arch/s390/kvm/guestdbg.c >>>> index d1f8241..b68db4b 100644 >>>> --- a/arch/s390/kvm/guestdbg.c >>>> +++ b/arch/s390/kvm/guestdbg.c >>>> @@ -216,7 +216,7 @@ int kvm_s390_import_bp_data(struct kvm_vcpu *vcpu, >>>> else if (dbg->arch.nr_hw_bp > MAX_BP_COUNT) >>>> return -EINVAL; >>>> >>>> - size = dbg->arch.nr_hw_bp * sizeof(struct kvm_hw_breakpoint); >>>> + size = dbg->arch.nr_hw_bp * sizeof(*bp_data); >>>> bp_data = kmalloc(size, GFP_KERNEL); >>>> if (!bp_data) { >>>> ret = -ENOMEM; >>>> @@ -241,7 +241,7 @@ int kvm_s390_import_bp_data(struct kvm_vcpu *vcpu, >>>> } >>>> } >>>> >>>> - size = nr_wp * sizeof(struct kvm_hw_wp_info_arch); >>>> + size = nr_wp * sizeof(*wp_info); >>>> if (size > 0) { >>>> wp_info = kmalloc(size, GFP_KERNEL); >>>> if (!wp_info) { >>>> @@ -249,7 +249,7 @@ int kvm_s390_import_bp_data(struct kvm_vcpu *vcpu, >>>> goto error; >>>> } >>>> } >>>> - size = nr_bp * sizeof(struct kvm_hw_bp_info_arch); >>>> + size = nr_bp * sizeof(*bp_info); >>>> if (size > 0) { >>>> bp_info = kmalloc(size, GFP_KERNEL); >>>> if (!bp_info) { >>> >>> >>> IMHO the common pattern for kmalloc is >>> bp_info = kmalloc( nr_bp * sizeof(*bp_info), GFP_KERNEL); >>> >>> i can not remember code with a check for size < 0, i guess it is here >>> to avoid an overflow ? since kmalloc takes a size_t argument this would cause >>> a malloc failure an can be ignored. >> >> Shoudn't it be kcalloc? > > Or kmalloc_array, since zeroing is not necessary. Might be an idea for > a new Coccinelle script, like > > - kmalloc (N * sizeof T, GFP) > + kmalloc_array(N, sizeof T, GFP) > my personal taste is to stay close to the libc functions. technical there is no difference static inline void *kcalloc(size_t n, size_t size, gfp_t flags) { return kmalloc_array(n, size, flags | __GFP_ZERO); } and i do not see any time critical things here, re, wh > Thanks, > > Paolo > >> >> julia >> >>> >>> >>> just my 2 cents. >>> re, >>> wh >>> >> >