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Date: Mon, 16 Aug 2010 23:51:30 -0700 (PDT)
From: David Rientjes <rientjes@...gle.com>
To: Naoya Horiguchi <n-horiguchi@...jp.nec.com>
cc: Andi Kleen <andi@...stfloor.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Christoph Lameter <cl@...ux-foundation.org>,
Mel Gorman <mel@....ul.ie>,
Wu Fengguang <fengguang.wu@...el.com>,
"Jun'ichi Nomura" <j-nomura@...jp.nec.com>,
linux-mm <linux-mm@...ck.org>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/9] hugetlb: add allocate function for hugepage
migration
On Tue, 10 Aug 2010, Naoya Horiguchi wrote:
> diff --git linux-mce-hwpoison/include/linux/hugetlb.h linux-mce-hwpoison/include/linux/hugetlb.h
> index f479700..142bd4f 100644
> --- linux-mce-hwpoison/include/linux/hugetlb.h
> +++ linux-mce-hwpoison/include/linux/hugetlb.h
> @@ -228,6 +228,8 @@ struct huge_bootmem_page {
> struct hstate *hstate;
> };
>
> +struct page *alloc_huge_page_no_vma_node(struct hstate *h, int nid);
> +
> /* arch callback */
> int __init alloc_bootmem_huge_page(struct hstate *h);
>
> @@ -303,6 +305,7 @@ static inline struct hstate *page_hstate(struct page *page)
>
> #else
> struct hstate {};
> +#define alloc_huge_page_no_vma_node(h, nid) NULL
> #define alloc_bootmem_huge_page(h) NULL
> #define hstate_file(f) NULL
> #define hstate_vma(v) NULL
> diff --git linux-mce-hwpoison/mm/hugetlb.c linux-mce-hwpoison/mm/hugetlb.c
> index 5c77a73..2815b83 100644
> --- linux-mce-hwpoison/mm/hugetlb.c
> +++ linux-mce-hwpoison/mm/hugetlb.c
> @@ -466,11 +466,22 @@ static void enqueue_huge_page(struct hstate *h, struct page *page)
> h->free_huge_pages_node[nid]++;
> }
>
> +static struct page *dequeue_huge_page_node(struct hstate *h, int nid)
> +{
> + struct page *page;
> + if (list_empty(&h->hugepage_freelists[nid]))
> + return NULL;
> + page = list_entry(h->hugepage_freelists[nid].next, struct page, lru);
> + list_del(&page->lru);
> + h->free_huge_pages--;
> + h->free_huge_pages_node[nid]--;
> + return page;
> +}
> +
> static struct page *dequeue_huge_page_vma(struct hstate *h,
> struct vm_area_struct *vma,
> unsigned long address, int avoid_reserve)
> {
> - int nid;
> struct page *page = NULL;
> struct mempolicy *mpol;
> nodemask_t *nodemask;
> @@ -496,19 +507,13 @@ static struct page *dequeue_huge_page_vma(struct hstate *h,
>
> for_each_zone_zonelist_nodemask(zone, z, zonelist,
> MAX_NR_ZONES - 1, nodemask) {
> - nid = zone_to_nid(zone);
> - if (cpuset_zone_allowed_softwall(zone, htlb_alloc_mask) &&
> - !list_empty(&h->hugepage_freelists[nid])) {
> - page = list_entry(h->hugepage_freelists[nid].next,
> - struct page, lru);
> - list_del(&page->lru);
> - h->free_huge_pages--;
> - h->free_huge_pages_node[nid]--;
> -
> - if (!avoid_reserve)
> - decrement_hugepage_resv_vma(h, vma);
> -
> - break;
> + if (cpuset_zone_allowed_softwall(zone, htlb_alloc_mask)) {
> + page = dequeue_huge_page_node(h, zone_to_nid(zone));
> + if (page) {
> + if (!avoid_reserve)
> + decrement_hugepage_resv_vma(h, vma);
> + break;
> + }
> }
> }
> err:
> @@ -616,7 +621,7 @@ int PageHuge(struct page *page)
> }
> EXPORT_SYMBOL_GPL(PageHuge);
>
> -static struct page *alloc_fresh_huge_page_node(struct hstate *h, int nid)
> +static struct page *__alloc_huge_page_node(struct hstate *h, int nid)
> {
> struct page *page;
>
> @@ -627,14 +632,61 @@ static struct page *alloc_fresh_huge_page_node(struct hstate *h, int nid)
> htlb_alloc_mask|__GFP_COMP|__GFP_THISNODE|
> __GFP_REPEAT|__GFP_NOWARN,
> huge_page_order(h));
> + if (page && arch_prepare_hugepage(page)) {
> + __free_pages(page, huge_page_order(h));
> + return NULL;
> + }
> +
> + return page;
> +}
> +
> +static struct page *alloc_fresh_huge_page_node(struct hstate *h, int nid)
> +{
> + struct page *page = __alloc_huge_page_node(h, nid);
> + if (page)
> + prep_new_huge_page(h, page, nid);
> + return page;
> +}
> +
> +static struct page *alloc_buddy_huge_page_node(struct hstate *h, int nid)
> +{
> + struct page *page = __alloc_huge_page_node(h, nid);
> if (page) {
> - if (arch_prepare_hugepage(page)) {
> - __free_pages(page, huge_page_order(h));
> + set_compound_page_dtor(page, free_huge_page);
> + spin_lock(&hugetlb_lock);
> + h->nr_huge_pages++;
> + h->nr_huge_pages_node[nid]++;
> + spin_unlock(&hugetlb_lock);
> + put_page_testzero(page);
> + }
> + return page;
> +}
> +
> +/*
> + * This allocation function is useful in the context where vma is irrelevant.
> + * E.g. soft-offlining uses this function because it only cares physical
> + * address of error page.
> + */
> +struct page *alloc_huge_page_no_vma_node(struct hstate *h, int nid)
> +{
> + struct page *page;
> +
> + spin_lock(&hugetlb_lock);
> + get_mems_allowed();
Why is this calling get_mems_allowed()? dequeue_huge_page_node() isn't
concerned if nid can be allocated by current in this context.
> + page = dequeue_huge_page_node(h, nid);
> + put_mems_allowed();
> + spin_unlock(&hugetlb_lock);
> +
> + if (!page) {
> + page = alloc_buddy_huge_page_node(h, nid);
> + if (!page) {
> + __count_vm_event(HTLB_BUDDY_PGALLOC_FAIL);
> return NULL;
> - }
> - prep_new_huge_page(h, page, nid);
> + } else
> + __count_vm_event(HTLB_BUDDY_PGALLOC);
> }
>
> + set_page_refcounted(page);
Possibility of NULL pointer dereference?
> return page;
> }
>
--
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