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SubjectRe: [patch] mm, hugetlb: generalize writes to nr_hugepages
On Mon, 30 Jun 2014 16:57:06 -0700 (PDT)
David Rientjes <rientjes@google.com> wrote:

> Three different interfaces alter the maximum number of hugepages for an
> hstate:
>
> - /proc/sys/vm/nr_hugepages for global number of hugepages of the default
> hstate,
>
> - /sys/kernel/mm/hugepages/hugepages-X/nr_hugepages for global number of
> hugepages for a specific hstate, and
>
> - /sys/kernel/mm/hugepages/hugepages-X/nr_hugepages/mempolicy for number of
> hugepages for a specific hstate over the set of allowed nodes.
>
> Generalize the code so that a single function handles all of these writes
> instead of duplicating the code in two different functions.
>
> This decreases the number of lines of code, but also reduces the size of
> .text by about half a percent since set_max_huge_pages() can be inlined.
>
> Signed-off-by: David Rientjes <rientjes@google.com>
> ---
> mm/hugetlb.c | 61 ++++++++++++++++++++++++++----------------------------------
> 1 file changed, 26 insertions(+), 35 deletions(-)
>
> 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.

> -
> - 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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