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Subject[PATCH 05/10] HWPOISON, hugetlb: add free check to dequeue_hwpoison_huge_page()
Date
This check is necessary to avoid race between dequeue and allocation,
which can cause a free hugepage to be dequeued twice and get kernel unstable.

Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
---
include/linux/hugetlb.h | 4 ++--
mm/hugetlb.c | 29 +++++++++++++++++++++++++----
mm/memory-failure.c | 6 ++++--
3 files changed, 31 insertions(+), 8 deletions(-)

diff --git v2.6.36-rc2/include/linux/hugetlb.h v2.6.36-rc2/include/linux/hugetlb.h
index 9e51f77..796f30e 100644
--- v2.6.36-rc2/include/linux/hugetlb.h
+++ v2.6.36-rc2/include/linux/hugetlb.h
@@ -43,7 +43,7 @@ int hugetlb_reserve_pages(struct inode *inode, long from, long to,
struct vm_area_struct *vma,
int acctflags);
void hugetlb_unreserve_pages(struct inode *inode, long offset, long freed);
-void __isolate_hwpoisoned_huge_page(struct page *page);
+int dequeue_hwpoisoned_huge_page(struct page *page);
void copy_huge_page(struct page *dst, struct page *src);

extern unsigned long hugepages_treat_as_movable;
@@ -102,7 +102,7 @@ static inline void hugetlb_report_meminfo(struct seq_file *m)
#define hugetlb_free_pgd_range(tlb, addr, end, floor, ceiling) ({BUG(); 0; })
#define hugetlb_fault(mm, vma, addr, flags) ({ BUG(); 0; })
#define huge_pte_offset(mm, address) 0
-#define __isolate_hwpoisoned_huge_page(page) 0
+#define dequeue_hwpoisoned_huge_page(page) 0
static inline void copy_huge_page(struct page *dst, struct page *src)
{
}
diff --git v2.6.36-rc2/mm/hugetlb.c v2.6.36-rc2/mm/hugetlb.c
index 55f3e2d..8948abc 100644
--- v2.6.36-rc2/mm/hugetlb.c
+++ v2.6.36-rc2/mm/hugetlb.c
@@ -2953,18 +2953,39 @@ void hugetlb_unreserve_pages(struct inode *inode, long offset, long freed)
hugetlb_acct_memory(h, -(chg - freed));
}

+/* Should be called in hugetlb_lock */
+static int is_hugepage_on_freelist(struct page *hpage)
+{
+ struct page *page;
+ struct page *tmp;
+ struct hstate *h = page_hstate(hpage);
+ int nid = page_to_nid(hpage);
+
+ list_for_each_entry_safe(page, tmp, &h->hugepage_freelists[nid], lru)
+ if (page == hpage)
+ return 1;
+ return 0;
+}
+
+#ifdef CONFIG_MEMORY_FAILURE
/*
* This function is called from memory failure code.
* Assume the caller holds page lock of the head page.
*/
-void __isolate_hwpoisoned_huge_page(struct page *hpage)
+int dequeue_hwpoisoned_huge_page(struct page *hpage)
{
struct hstate *h = page_hstate(hpage);
int nid = page_to_nid(hpage);
+ int ret = -EBUSY;

spin_lock(&hugetlb_lock);
- list_del(&hpage->lru);
- h->free_huge_pages--;
- h->free_huge_pages_node[nid]--;
+ if (is_hugepage_on_freelist(hpage)) {
+ list_del(&hpage->lru);
+ h->free_huge_pages--;
+ h->free_huge_pages_node[nid]--;
+ ret = 0;
+ }
spin_unlock(&hugetlb_lock);
+ return ret;
}
+#endif
diff --git v2.6.36-rc2/mm/memory-failure.c v2.6.36-rc2/mm/memory-failure.c
index 9c26eec..c67f801 100644
--- v2.6.36-rc2/mm/memory-failure.c
+++ v2.6.36-rc2/mm/memory-failure.c
@@ -698,6 +698,7 @@ static int me_swapcache_clean(struct page *p, unsigned long pfn)
*/
static int me_huge_page(struct page *p, unsigned long pfn)
{
+ int res = 0;
struct page *hpage = compound_head(p);
/*
* We can safely recover from error on free or reserved (i.e.
@@ -710,8 +711,9 @@ static int me_huge_page(struct page *p, unsigned long pfn)
* so there is no race between isolation and mapping/unmapping.
*/
if (!(page_mapping(hpage) || PageAnon(hpage))) {
- __isolate_hwpoisoned_huge_page(hpage);
- return RECOVERED;
+ res = dequeue_hwpoisoned_huge_page(hpage);
+ if (!res)
+ return RECOVERED;
}
return DELAYED;
}
--
1.7.2.2


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