Just to be explicit what I've had in mind. This hasn't been even compile
tested but it should provide at least an idea where I am trying to go..
---
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index d5f3a62887cf..91fa05372114 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1528,26 +1528,36 @@ static void memcg_oom_recover(struct mem_cgroup *memcg)
static void mem_cgroup_oom(struct mem_cgroup *memcg, gfp_t mask, int order)
{
- if (!current->memcg_may_oom)
- return;
/*
* We are in the middle of the charge context here, so we
* don't want to block when potentially sitting on a callstack
* that holds all kinds of filesystem and mm locks.
*
- * Also, the caller may handle a failed allocation gracefully
- * (like optional page cache readahead) and so an OOM killer
- * invocation might not even be necessary.
+ * cgroup v1 allowes sync users space handling so we cannot afford
+ * to get stuck here for that configuration. That's why we don't do
+ * anything here except remember the OOM context and then deal with
+ * it at the end of the page fault when the stack is unwound, the
+ * locks are released, and when we know whether the fault was overall
+ * successful.
*
- * That's why we don't do anything here except remember the
- * OOM context and then deal with it at the end of the page
- * fault when the stack is unwound, the locks are released,
- * and when we know whether the fault was overall successful.
+ * On the other hand, in-kernel OOM killer allows for an async victim
+ * memory reclaim (oom_reaper) and that means that we are not solely
+ * relying on the oom victim to make a forward progress so we can stay
+ * in the the try_charge context and keep retrying as long as there
+ * are oom victims to select.
*/
- css_get(&memcg->css);
- current->memcg_in_oom = memcg;
- current->memcg_oom_gfp_mask = mask;
- current->memcg_oom_order = order;
+ if (memcg->oom_kill_disable) {
+ if (!current->memcg_may_oom)
+ return false;
+ css_get(&memcg->css);
+ current->memcg_in_oom = memcg;
+ current->memcg_oom_gfp_mask = mask;
+ current->memcg_oom_order = order;
+
+ return false;
+ }
+
+ return mem_cgroup_out_of_memory(memcg, mask, order);
}
/**
@@ -2007,8 +2017,11 @@ static int try_charge(struct mem_cgroup *memcg, gfp_t
gfp_mask,
mem_cgroup_event(mem_over_limit, MEMCG_OOM);
- mem_cgroup_oom(mem_over_limit, gfp_mask,
- get_order(nr_pages * PAGE_SIZE));
+ if (mem_cgroup_oom(mem_over_limit, gfp_mask,
+ get_order(nr_pages * PAGE_SIZE))) {
+ nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
+ goto retry;
+ }
nomem:
if (!(gfp_mask & __GFP_NOFAIL))
return -ENOMEM;
--
Michal Hocko
SUSE Labs
