On 9/10/21 3:39 PM, Vasily Averin wrote:
> The kernel currently allows dying tasks to exceed the memcg limits.
> The allocation is expected to be the last one and the occupied memory
> will be freed soon.
> This is not always true because it can be part of the huge vmalloc
> allocation. Allowed once, they will repeat over and over again.
> Moreover lifetime of the allocated object can differ from
> In addition the lifetime of the dying task.
> Multiple such allocations running concurrently can not only overuse
> the memcg limit, but can lead to a global out of memory and,
> in the worst case, cause the host to panic.
btw should_force_charge() function name become wrong with this.
Is it make sense to replace it by something like is_task_dying() ?
> Signed-off-by: Vasily Averin <vvs@xxxxxxxxxxxxx>
> ---
> mm/memcontrol.c | 23 +++++------------------
> 1 file changed, 5 insertions(+), 18 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 389b5766e74f..67195fcfbddf 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1834,6 +1834,9 @@ static enum oom_status mem_cgroup_oom(struct mem_cgroup *memcg, gfp_t mask, int
> return OOM_ASYNC;
> }
>
> + if (should_force_charge())
> + return OOM_SKIPPED;
> +
> mem_cgroup_mark_under_oom(memcg);
>
> locked = mem_cgroup_oom_trylock(memcg);
> @@ -2622,15 +2625,6 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask,
> if (gfp_mask & __GFP_ATOMIC)
> goto force;
>
> - /*
> - * Unlike in global OOM situations, memcg is not in a physical
> - * memory shortage. Allow dying and OOM-killed tasks to
> - * bypass the last charges so that they can exit quickly and
> - * free their memory.
> - */
> - if (unlikely(should_force_charge()))
> - goto force;
> -
> /*
> * Prevent unbounded recursion when reclaim operations need to
> * allocate memory. This might exceed the limits temporarily,
> @@ -2688,9 +2682,6 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask,
> if (gfp_mask & __GFP_RETRY_MAYFAIL)
> goto nomem;
>
> - if (fatal_signal_pending(current))
> - goto force;
> -
> /*
> * keep retrying as long as the memcg oom killer is able to make
> * a forward progress or bypass the charge if the oom killer
> @@ -2698,15 +2689,11 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask,
> */
> oom_status = mem_cgroup_oom(mem_over_limit, gfp_mask,
> get_order(nr_pages * PAGE_SIZE));
> - switch (oom_status) {
> - case OOM_SUCCESS:
> + if (oom_status == OOM_SUCCESS) {
> nr_retries = MAX_RECLAIM_RETRIES;
> goto retry;
> - case OOM_FAILED:
> + } else if (oom_status == OOM_FAILED)
> goto force;
> - default:
> - goto nomem;
> - }
> nomem:
> if (!(gfp_mask & __GFP_NOFAIL))
> return -ENOMEM;
>
