memcg: prevent endless loop when charging huge pages to near-limit group

[platform/adaptation/renesas_rcar/renesas_kernel.git] / mm / memcontrol.c

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 50eb50e..0e81eb5 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1111,6 +1111,23 @@ static bool mem_cgroup_check_under_limit(struct mem_cgroup *mem)
        return false;
 }
 
+/**
+ * mem_cgroup_check_margin - check if the memory cgroup allows charging
+ * @mem: memory cgroup to check
+ * @bytes: the number of bytes the caller intends to charge
+ *
+ * Returns a boolean value on whether @mem can be charged @bytes or
+ * whether this would exceed the limit.
+ */
+static bool mem_cgroup_check_margin(struct mem_cgroup *mem, unsigned long bytes)
+{
+       if (!res_counter_check_margin(&mem->res, bytes))
+               return false;
+       if (do_swap_account && !res_counter_check_margin(&mem->memsw, bytes))
+               return false;
+       return true;
+}
+
 static unsigned int get_swappiness(struct mem_cgroup *memcg)
 {
        struct cgroup *cgrp = memcg->css.cgroup;
@@ -1852,15 +1869,19 @@ static int __mem_cgroup_do_charge(struct mem_cgroup *mem, gfp_t gfp_mask,
                return CHARGE_WOULDBLOCK;
 
        ret = mem_cgroup_hierarchical_reclaim(mem_over_limit, NULL,
-                                       gfp_mask, flags);
+                                             gfp_mask, flags);
+       if (mem_cgroup_check_margin(mem_over_limit, csize))
+               return CHARGE_RETRY;
        /*
-        * try_to_free_mem_cgroup_pages() might not give us a full
-        * picture of reclaim. Some pages are reclaimed and might be
-        * moved to swap cache or just unmapped from the cgroup.
-        * Check the limit again to see if the reclaim reduced the
-        * current usage of the cgroup before giving up
+        * Even though the limit is exceeded at this point, reclaim
+        * may have been able to free some pages.  Retry the charge
+        * before killing the task.
+        *
+        * Only for regular pages, though: huge pages are rather
+        * unlikely to succeed so close to the limit, and we fall back
+        * to regular pages anyway in case of failure.
         */
-       if (ret || mem_cgroup_check_under_limit(mem_over_limit))
+       if (csize == PAGE_SIZE && ret)
                return CHARGE_RETRY;
 
        /*