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SubjectRe: [PATCH v13 03/11] cpuset: Simply allocation and freeing of cpumasks
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On 10/12/2018 11:55 AM, Waiman Long wrote:
> The previous commit introduces a new subparts_cpus mask into the cpuset
> data structure and a new tmpmasks structure. Managing the allocation
> and freeing of those cpumasks is becoming more complex.
>
> So a number of helper functions are added to simplify and streamline
> the management of those cpumasks. To make it simple, all the cpumasks
> are now pre-cleared on allocation.
>
> Signed-off-by: Waiman Long <longman@redhat.com>
> ---
> kernel/cgroup/cpuset.c | 104 +++++++++++++++++++++++++++++++++----------------
> 1 file changed, 71 insertions(+), 33 deletions(-)
>
> diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
> index 29a2bdc..9ac5f94 100644
> --- a/kernel/cgroup/cpuset.c
> +++ b/kernel/cgroup/cpuset.c
> @@ -456,6 +456,57 @@ static int is_cpuset_subset(const struct cpuset *p, const struct cpuset *q)
> }
>
> /**
> + * alloc_cpumasks - allocate three cpumasks for cpuset
> + * @cs: the cpuset that have cpumasks to be allocated.
> + * @tmp: the tmpmasks structure pointer
> + * Return: 0 if successful, -ENOMEM otherwise.
> + *
> + * Only one of the two input arguments should be non-NULL.
> + */
> +static inline int alloc_cpumasks(struct cpuset *cs, struct tmpmasks *tmp)
> +{
> + cpumask_var_t *pmask1, *pmask2, *pmask3;
> +
> + if (cs) {
> + pmask1 = &cs->cpus_allowed;
> + pmask2 = &cs->effective_cpus;
> + pmask3 = &cs->subparts_cpus;
> + } else {
> + pmask1 = &tmp->new_cpus;
> + pmask2 = &tmp->addmask;
> + pmask3 = &tmp->delmask;
> + }
> +
> + if (!zalloc_cpumask_var(pmask1, GFP_KERNEL))
> + return -ENOMEM;
> +
> + if (!zalloc_cpumask_var(pmask2, GFP_KERNEL))
> + goto free_one;
> +
> + if (!zalloc_cpumask_var(pmask3, GFP_KERNEL))
> + goto free_two;
> +
> + return 0;
> +
> +free_two:
> + free_cpumask_var(*pmask2);
> +free_one:
> + free_cpumask_var(*pmask1);
> + return -ENOMEM;
> +}
> +
> +/**
> + * free_cpumasks - free cpumasks in a tmpmasks structure
> + * @tmp: the tmpmasks structure pointer
> + */
> +static inline void free_cpumasks(struct tmpmasks *tmp)
> +{
> + free_cpumask_var(tmp->new_cpus);
> + free_cpumask_var(tmp->addmask);
> + free_cpumask_var(tmp->delmask);
> +}
> +

I hesitate to bring this up, but since you're respinning this
patch for a different bug...

Would it make sense to have free_cpumasks() have a similar
API and behavior to alloc_cpumasks()?  I could see this potentially
causing bugs/confusion in future patches.

Thanks.

Tom


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