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

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Message-Id: <20140708151113.dd1469faea6177959356620b@linux-foundation.org>
Date:	Tue, 8 Jul 2014 15:11:13 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Luiz Capitulino <lcapitulino@...hat.com>,
	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 17:44:46 -0700 (PDT) David Rientjes <rientjes@...gle.com> wrote:

> > > @@ -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().

This?

--- a/mm/hugetlb.c~mm-hugetlb-generalize-writes-to-nr_hugepages-fix
+++ a/mm/hugetlb.c
@@ -2260,6 +2260,9 @@ static int hugetlb_sysctl_handler_common
 	unsigned long tmp = h->max_huge_pages;
 	int ret;
 
+	if (!hugepages_supported())
+		return -ENOTSUPP;
+
 	table->data = &tmp;
 	table->maxlen = sizeof(unsigned long);
 	ret = proc_doulongvec_minmax(table, write, buffer, length, ppos);
_

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