2 files changed, 48 insertions, 7 deletions

diff --git a/include/linux/res_counter.h b/include/linux/res_counter.h
index fcb9884df618..a5930cb66145 100644
--- a/include/linux/res_counter.h
+++ b/include/linux/res_counter.h
@@ -182,6 +182,26 @@ static inline bool res_counter_check_under_limit(struct res_counter *cnt)
         return ret;
 }
 
+/**
+ * res_counter_check_margin - check if the counter allows charging
+ * @cnt: the resource counter to check
+ * @bytes: the number of bytes to check the remaining space against
+ *
+ * Returns a boolean value on whether the counter can be charged
+ * @bytes or whether this would exceed the limit.
+ */
+static inline bool res_counter_check_margin(struct res_counter *cnt,
+                                            unsigned long bytes)
+{
+        bool ret;
+        unsigned long flags;
+
+        spin_lock_irqsave(&cnt->lock, flags);
+        ret = cnt->limit - cnt->usage >= bytes;
+        spin_unlock_irqrestore(&cnt->lock, flags);
+        return ret;
+}
+
 static inline bool res_counter_check_under_soft_limit(struct res_counter *cnt)
 {
         bool ret;
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 50eb50e100fd..0e81eb5f0aea 100644
--- 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;
 
         /*