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SubjectRe: [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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