Re: [patch] mm, hugetlb: generalize writes to nr_hugepages

[Luiz Capitulino <lcapitulino@redhat.com>]

On Wed, 2 Jul 2014 17:44:46 -0700 (PDT)
David Rientjes <rientjes@google.com> wrote:

> On Wed, 2 Jul 2014, Luiz Capitulino wrote:
> 
> > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> > > --- a/mm/hugetlb.c
> > > +++ b/mm/hugetlb.c
> > > @@ -1734,21 +1734,13 @@ static ssize_t nr_hugepages_show_common(struct kobject *kobj,
> > >  	return sprintf(buf, "%lu\n", nr_huge_pages);
> > >  }
> > >  
> > > -static ssize_t nr_hugepages_store_common(bool obey_mempolicy,
> > > -			struct kobject *kobj, struct kobj_attribute *attr,
> > > -			const char *buf, size_t len)
> > > +static ssize_t __nr_hugepages_store_common(bool obey_mempolicy,
> > > +					   struct hstate *h, int nid,
> > > +					   unsigned long count, size_t len)
> > >  {
> > >  	int err;
> > > -	int nid;
> > > -	unsigned long count;
> > > -	struct hstate *h;
> > >  	NODEMASK_ALLOC(nodemask_t, nodes_allowed, GFP_KERNEL | __GFP_NORETRY);
> > >  
> > > -	err = kstrtoul(buf, 10, &count);
> > > -	if (err)
> > > -		goto out;
> > > -
> > > -	h = kobj_to_hstate(kobj, &nid);
> > >  	if (hstate_is_gigantic(h) && !gigantic_page_supported()) {
> > >  		err = -EINVAL;
> > >  		goto out;
> > > @@ -1784,6 +1776,23 @@ out:
> > >  	return err;
> > >  }
> > >  
> > > +static ssize_t nr_hugepages_store_common(bool obey_mempolicy,
> > > +					 struct kobject *kobj, const char *buf,
> > > +					 size_t len)
> > > +{
> > > +	struct hstate *h;
> > > +	unsigned long count;
> > > +	int nid;
> > > +	int err;
> > > +
> > > +	err = kstrtoul(buf, 10, &count);
> > > +	if (err)
> > > +		return err;
> > > +
> > > +	h = kobj_to_hstate(kobj, &nid);
> > > +	return __nr_hugepages_store_common(obey_mempolicy, h, nid, count, len);
> > > +}
> > > +
> > >  static ssize_t nr_hugepages_show(struct kobject *kobj,
> > >  				       struct kobj_attribute *attr, char *buf)
> > >  {
> > > @@ -1793,7 +1802,7 @@ static ssize_t nr_hugepages_show(struct kobject *kobj,
> > >  static ssize_t nr_hugepages_store(struct kobject *kobj,
> > >  	       struct kobj_attribute *attr, const char *buf, size_t len)
> > >  {
> > > -	return nr_hugepages_store_common(false, kobj, attr, buf, len);
> > > +	return nr_hugepages_store_common(false, kobj, buf, len);
> > >  }
> > >  HSTATE_ATTR(nr_hugepages);
> > >  
> > > @@ -1812,7 +1821,7 @@ static ssize_t nr_hugepages_mempolicy_show(struct kobject *kobj,
> > >  static ssize_t nr_hugepages_mempolicy_store(struct kobject *kobj,
> > >  	       struct kobj_attribute *attr, const char *buf, size_t len)
> > >  {
> > > -	return nr_hugepages_store_common(true, kobj, attr, buf, len);
> > > +	return nr_hugepages_store_common(true, kobj, buf, len);
> > >  }
> > >  HSTATE_ATTR(nr_hugepages_mempolicy);
> > >  #endif
> > > @@ -2248,36 +2257,18 @@ static int hugetlb_sysctl_handler_common(bool obey_mempolicy,
> > >  			 void __user *buffer, size_t *length, loff_t *ppos)
> > >  {
> > >  	struct hstate *h = &default_hstate;
> > > -	unsigned long tmp;
> > > +	unsigned long tmp = h->max_huge_pages;
> > >  	int ret;
> > >  
> > > -	if (!hugepages_supported())
> > > -		return -ENOTSUPP;
> > 
> > Shouldn't you add this check to __nr_hugepages_store_common()? Otherwise
> > looks good to me.
> > 
> 
> Hmm, I think you're right but I don't think __nr_hugepages_store_common() 
> is the right place: if we have a legitimate hstate for the sysfs tunables 
> then we should support hugepages.  I think this should be kept in 
> hugetlb_sysctl_handler_common().

You seem to be right. Feel free to add if you respin:

Reviewed-by: Luiz Capitulino <lcapitulino@redhat.com>

> 
> > > -
> > > -	tmp = h->max_huge_pages;
> > > -
> > > -	if (write && hstate_is_gigantic(h) && !gigantic_page_supported())
> > > -		return -EINVAL;
> > > -
> > >  	table->data = &tmp;
> > >  	table->maxlen = sizeof(unsigned long);
> > >  	ret = proc_doulongvec_minmax(table, write, buffer, length, ppos);
> > >  	if (ret)
> > >  		goto out;
> > >  
> > > -	if (write) {
> > > -		NODEMASK_ALLOC(nodemask_t, nodes_allowed,
> > > -						GFP_KERNEL | __GFP_NORETRY);
> > > -		if (!(obey_mempolicy &&
> > > -			       init_nodemask_of_mempolicy(nodes_allowed))) {
> > > -			NODEMASK_FREE(nodes_allowed);
> > > -			nodes_allowed = &node_states[N_MEMORY];
> > > -		}
> > > -		h->max_huge_pages = set_max_huge_pages(h, tmp, nodes_allowed);
> > > -
> > > -		if (nodes_allowed != &node_states[N_MEMORY])
> > > -			NODEMASK_FREE(nodes_allowed);
> > > -	}
> > > +	if (write)
> > > +		ret = __nr_hugepages_store_common(obey_mempolicy, h,
> > > +						  NUMA_NO_NODE, tmp, *length);
> > >  out:
> > >  	return ret;
> > >  }
> 

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