From: walter harms <wharms@bfs.de>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Julia Lawall" <julia.lawall@lip6.fr>,
"SF Markus Elfring" <elfring@users.sourceforge.net>,
kvm@vger.kernel.org, linux-s390@vger.kernel.org,
"Christian Bornträger" <borntraeger@de.ibm.com>,
"Cornelia Huck" <cornelia.huck@de.ibm.com>,
"David Hildenbrand" <dahi@linux.vnet.ibm.com>,
"Heiko Carstens" <heiko.carstens@de.ibm.com>,
"Martin Schwidefsky" <schwidefsky@de.ibm.com>,
"Radim Krčmář" <rkrcmar@redhat.com>,
LKML <linux-kernel@vger.kernel.org>,
kernel-janitors@vger.kernel.org
Subject: Re: [PATCH 1/4] KVM-S390: Improve determination of sizes in kvm_s390_import_bp_data()
Date: Thu, 18 Aug 2016 12:52:11 +0200 [thread overview]
Message-ID: <57B5935B.3050602@bfs.de> (raw)
In-Reply-To: <9db1986a-9b93-72ca-f35e-85b5b5e9f351@redhat.com>
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 <elfring@users.sourceforge.net>
>>>> 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 <elfring@users.sourceforge.net>
>>>> ---
>>>> 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
>>>
>>
>
next prev parent reply other threads:[~2016-08-18 10:52 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-17 18:02 [PATCH 0/4] KVM-S390: Fine-tuning for kvm_s390_import_bp_data() SF Markus Elfring
2016-08-17 18:06 ` [PATCH 1/4] KVM-S390: Improve determination of sizes in kvm_s390_import_bp_data() SF Markus Elfring
2016-08-18 7:25 ` walter harms
2016-08-18 9:02 ` Julia Lawall
2016-08-18 9:48 ` Paolo Bonzini
2016-08-18 10:52 ` walter harms [this message]
2016-08-18 10:55 ` Paolo Bonzini
2016-08-22 12:58 ` Cornelia Huck
2016-08-24 12:10 ` Replacing specific kmalloc() calls by kmalloc_array()? SF Markus Elfring
2016-08-24 15:00 ` Paolo Bonzini
2016-08-17 18:08 ` [PATCH 2/4] KVM-S390: Use memdup_user() rather than duplicating its implementation SF Markus Elfring
2016-08-22 13:02 ` David Hildenbrand
2016-08-22 13:05 ` Cornelia Huck
2016-08-24 15:19 ` Christian Borntraeger
2016-08-24 18:30 ` [PATCH v2 0/2] KVM: s390: Fine-tuning for kvm_s390_import_bp_data() SF Markus Elfring
2016-08-24 18:36 ` [PATCH v2 1/2] KVM: s390: Improve determination of sizes in kvm_s390_import_bp_data() SF Markus Elfring
2016-08-25 16:10 ` Cornelia Huck
2016-08-25 16:45 ` SF Markus Elfring
2016-08-25 17:34 ` Software evolution around scripts for the semantic patch langugae SF Markus Elfring
2016-08-25 17:40 ` Cornelia Huck
2016-08-25 17:54 ` SF Markus Elfring
2016-08-25 18:14 ` Julia Lawall
2016-08-25 18:20 ` SF Markus Elfring
2016-08-25 18:23 ` Julia Lawall
2016-08-25 21:04 ` Cornelia Huck
2016-08-24 18:40 ` [PATCH v2 2/2] KVM: s390: Use memdup_user() rather than duplicating code SF Markus Elfring
2016-08-25 16:11 ` Cornelia Huck
2016-10-03 12:11 ` Geert Uytterhoeven
2016-10-03 12:28 ` SF Markus Elfring
2016-10-03 13:10 ` Geert Uytterhoeven
2016-10-03 13:47 ` SF Markus Elfring
2016-10-03 14:00 ` Geert Uytterhoeven
2016-10-03 14:25 ` SF Markus Elfring
2016-08-25 16:12 ` [PATCH v2 0/2] KVM: s390: Fine-tuning for kvm_s390_import_bp_data() Christian Borntraeger
2016-08-17 18:10 ` [PATCH 3/4] KVM-S390: Less function calls in kvm_s390_import_bp_data() after error detection SF Markus Elfring
2016-08-22 12:58 ` David Hildenbrand
2016-08-22 13:00 ` Cornelia Huck
2016-08-22 16:56 ` SF Markus Elfring
2016-08-22 19:37 ` Cornelia Huck
2016-08-22 21:17 ` SF Markus Elfring
2016-08-22 21:28 ` Cornelia Huck
2016-08-31 12:29 ` Paolo Bonzini
2016-08-24 15:10 ` Christian Borntraeger
2016-08-27 16:12 ` SF Markus Elfring
2016-08-17 18:12 ` [PATCH 4/4] KVM-S390: Delete an unnecessary initialisation for a buffer variable SF Markus Elfring
2016-08-22 12:59 ` David Hildenbrand
2016-08-22 13:01 ` Cornelia Huck
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