From: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Subject: mm: hugetlb: fix hugepage memory leak caused by wrong reserve count
When dequeue_huge_page_vma() in alloc_huge_page() fails, we fall back to
alloc_buddy_huge_page() to directly create a hugepage from the buddy allocator.
In that case, however, if alloc_buddy_huge_page() succeeds we don't decrement
h->resv_huge_pages, which means that successful hugetlb_fault() returns without
releasing the reserve count. As a result, subsequent hugetlb_fault() might fail
despite that there are still free hugepages.
This patch simply adds decrementing code on that code path.
I reproduced this problem when testing v4.3 kernel in the following situation:
- the test machine/VM is a NUMA system,
- hugepage overcommiting is enabled,
- most of hugepages are allocated and there's only one free hugepage
which is on node 0 (for example),
- another program, which calls set_mempolicy(MPOL_BIND) to bind itself to
node 1, tries to allocate a hugepage,
- the allocation should fail but the reserve count is still hold.
Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [3.16+]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/hugetlb.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff -puN mm/hugetlb.c~mm-hugetlb-fix-hugepage-memory-leak-caused-by-wrong-reserve-count mm/hugetlb.c
--- a/mm/hugetlb.c~mm-hugetlb-fix-hugepage-memory-leak-caused-by-wrong-reserve-count
+++ a/mm/hugetlb.c
@@ -1886,7 +1886,10 @@ struct page *alloc_huge_page(struct vm_a
page = __alloc_buddy_huge_page_with_mpol(h, vma, addr);
if (!page)
goto out_uncharge_cgroup;
-
+ if (!avoid_reserve && vma_has_reserves(vma, gbl_chg)) {
+ SetPagePrivate(page);
+ h->resv_huge_pages--;
+ }
spin_lock(&hugetlb_lock);
list_move(&page->lru, &h->hugepage_activelist);
/* Fall through */
_
--
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