Re: [PATCH 3/4] KVM-S390: Less function calls in kvm_s390_import_bp_data() after error detection

Christian Borntraeger
2016-08-24T15:10:03Z

On 08/17/2016 02:10 PM, SF Markus Elfring wrote:
> From: Markus Elfring <elfring@users.sourceforge.net>
> Date: Wed, 17 Aug 2016 19:25:50 +0200
>
> The kfree() function was called in a few cases by the
> kvm_s390_import_bp_data() function during error handling
> even if a passed variable contained a null pointer.
>
> Adjust jump targets according to the Linux coding style convention.
>
> Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
> ---
> arch/s390/kvm/guestdbg.c | 14 ++++++++------
> 1 file changed, 8 insertions(+), 6 deletions(-)
>
> diff --git a/arch/s390/kvm/guestdbg.c b/arch/s390/kvm/guestdbg.c
> index 8f886ee..f2514af 100644
> --- a/arch/s390/kvm/guestdbg.c
> +++ b/arch/s390/kvm/guestdbg.c
> @@ -239,7 +239,7 @@ int kvm_s390_import_bp_data(struct kvm_vcpu *vcpu,
> wp_info = kmalloc(size, GFP_KERNEL);
> if (!wp_info) {
> ret = -ENOMEM;
> - goto error;
> + goto free_bp_data;
> }
> }
> size = nr_bp * sizeof(*bp_info);
> @@ -247,7 +247,7 @@ int kvm_s390_import_bp_data(struct kvm_vcpu *vcpu,
> bp_info = kmalloc(size, GFP_KERNEL);
> if (!bp_info) {
> ret = -ENOMEM;
> - goto error;
> + goto free_wp_info;
> }
> }
>
> @@ -257,7 +257,7 @@ int kvm_s390_import_bp_data(struct kvm_vcpu *vcpu,
> ret = __import_wp_info(vcpu, &bp_data[i],
> &wp_info[nr_wp]);
> if (ret)
> - goto error;
> + goto free_bp_info;
> nr_wp++;
> break;
> case KVM_HW_BP:
> @@ -273,10 +273,12 @@ int kvm_s390_import_bp_data(struct kvm_vcpu *vcpu,
> vcpu->arch.guestdbg.nr_hw_wp = nr_wp;
> vcpu->arch.guestdbg.hw_wp_info = wp_info;
> return 0;
> -error:
> - kfree(bp_data);
> - kfree(wp_info);
> +free_bp_info:
> kfree(bp_info);
> +free_wp_info:
> + kfree(wp_info);
> +free_bp_data:
> + kfree(bp_data);
> return ret;
> }

I agree with Cornelia, while it seems correct from a technical point of view, it will
make the code harder to maintain. For example if we ever add a new malloc and remove
another one over time we would need to reshuffle the labels and this did went wrong
several times in the past.

Christian