hugetlb: fix surplus pages accounting

Dan Rue has noticed that libhugetlbfs test suite fails counter test:

  # mount_point="/mnt/hugetlb/"
  # echo 200 > /proc/sys/vm/nr_hugepages
  # mkdir -p "${mount_point}"
  # mount -t hugetlbfs hugetlbfs "${mount_point}"
  # export LD_LIBRARY_PATH=/root/libhugetlbfs/libhugetlbfs-2.20/obj64
  # /root/libhugetlbfs/libhugetlbfs-2.20/tests/obj64/counters
  Starting testcase "/root/libhugetlbfs/libhugetlbfs-2.20/tests/obj64/counters", pid 3319
  Base pool size: 0
  Clean...
  FAIL    Line 326: Bad HugePages_Total: expected 0, actual 1

The bug was bisected to 0c397daea1d4 ("mm, hugetlb: further simplify
hugetlb allocation API").

The reason is that alloc_surplus_huge_page() misaccounts per node
surplus pages.  We should increase surplus_huge_pages_node rather than
nr_huge_pages_node which is already handled by alloc_fresh_huge_page.

Link: http://lkml.kernel.org/r/20180221191439.GM2231@dhcp22.suse.cz
Fixes: 0c397daea1d4 ("mm, hugetlb: further simplify hugetlb allocation API")
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reported-by: Dan Rue <dan.rue@linaro.org>
Tested-by: Dan Rue <dan.rue@linaro.org>
Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 7c204e3..a963f20 100644 (file)
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1583,7 +1583,7 @@ static struct page *alloc_surplus_huge_page(struct hstate *h, gfp_t gfp_mask,
                page = NULL;
        } else {
                h->surplus_huge_pages++;
-               h->nr_huge_pages_node[page_to_nid(page)]++;
+               h->surplus_huge_pages_node[page_to_nid(page)]++;
        }
 
 out_unlock: