memcg: never OOM when charging huge pages

Huge page coverage should obviously have less priority than the continued
execution of a process.

Never kill a process when charging it a huge page fails.  Instead, give up
after the first failed reclaim attempt and fall back to regular pages.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 0e81eb5..fc75f34 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2351,13 +2351,19 @@ static int mem_cgroup_charge_common(struct page *page, struct mm_struct *mm,
                                gfp_t gfp_mask, enum charge_type ctype)
 {
        struct mem_cgroup *mem = NULL;
+       int page_size = PAGE_SIZE;
        struct page_cgroup *pc;
+       bool oom = true;
        int ret;
-       int page_size = PAGE_SIZE;
 
        if (PageTransHuge(page)) {
                page_size <<= compound_order(page);
                VM_BUG_ON(!PageTransHuge(page));
+               /*
+                * Never OOM-kill a process for a huge page.  The
+                * fault handler will fall back to regular pages.
+                */
+               oom = false;
        }
 
        pc = lookup_page_cgroup(page);
@@ -2366,7 +2372,7 @@ static int mem_cgroup_charge_common(struct page *page, struct mm_struct *mm,
                return 0;
        prefetchw(pc);
 
-       ret = __mem_cgroup_try_charge(mm, gfp_mask, &mem, true, page_size);
+       ret = __mem_cgroup_try_charge(mm, gfp_mask, &mem, oom, page_size);
        if (ret || !mem)
                return ret;