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: <stable@xxxxxxxxxxxxxxx> [3.16+] --- - the reason why I set stable target to "3.16+" is that this patch can be applied easily/automatically on these versions. But this bug seems to be old one, so if you are interested in backporting to older kernels, please let me know. --- mm/hugetlb.c | 5 ++++- 1 files changed, 4 insertions(+), 1 deletions(-) diff --git v4.3/mm/hugetlb.c v4.3_patched/mm/hugetlb.c index 9cc7734..77c518c 100644 --- v4.3/mm/hugetlb.c +++ v4.3_patched/mm/hugetlb.c @@ -1790,7 +1790,10 @@ struct page *alloc_huge_page(struct vm_area_struct *vma, page = alloc_buddy_huge_page(h, NUMA_NO_NODE); 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 */ -- 1.7.1 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>