linux-kernel - Re: [patch] mm, hugetlb: generalize writes to nr

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Message-ID: <alpine.DEB.2.02.1407021743340.4970@chino.kir.corp.google.com>
Date:	Wed, 2 Jul 2014 17:44:46 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Luiz Capitulino <lcapitulino@...hat.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [patch] mm, hugetlb: generalize writes to nr_hugepages

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().

> > -
> > -	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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