mm/hugetlb: fix total hugetlbfs pages count when using memory overcommit accouting

hugetlb_total_pages is used for overcommit calculations but the current
implementation considers only the default hugetlb page size (which is
either the first defined hugepage size or the one specified by
default_hugepagesz kernel boot parameter).

If the system is configured for more than one hugepage size, which is
possible since a137e1cc ("hugetlbfs: per mount huge page sizes") then the
overcommit estimation done by __vm_enough_memory() (resp.  shown by
meminfo_proc_show) is not precise - there is an impression of more
available/allowed memory.  This can lead to an unexpected ENOMEM/EFAULT
resp.  SIGSEGV when memory is accounted.

Testcase:
boot: hugepagesz=1G hugepages=1
the default overcommit ratio is 50
before patch:
egrep 'CommitLimit' /proc/meminfo
CommitLimit:     55434168 kB
after patch:
egrep 'CommitLimit' /proc/meminfo
CommitLimit:     54909880 kB

Signed-off-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: Hillf Danton <dhillf@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: <stable@vger.kernel.org>		[3.0+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index c65a8a583d132ed0609808a30d1ddd2cc4ca5050..8bf817c72b852a068eb4d442328dade93397051a 100644 (file)
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -2124,8 +2124,11 @@ int hugetlb_report_node_meminfo(int nid, char *buf)
 /* Return the number pages of memory we physically have, in PAGE_SIZE units. */
 unsigned long hugetlb_total_pages(void)
 {
-       struct hstate *h = &default_hstate;
-       return h->nr_huge_pages * pages_per_huge_page(h);
+       struct hstate *h;
+       unsigned long nr_total_pages = 0;
+       for_each_hstate(h)
+               nr_total_pages += h->nr_huge_pages * pages_per_huge_page(h);
+       return nr_total_pages;
 }
 
 static int hugetlb_acct_memory(struct hstate *h, long delta)