linux-kernel - [PATCH 1/2] memcg, oom: no oom-kill for __GFP_RETRY

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Date:   Mon, 29 Apr 2019 10:13:31 -0700
From:   Shakeel Butt <shakeelb@...gle.com>
To:     Johannes Weiner <hannes@...xchg.org>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Michal Hocko <mhocko@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <guro@...com>, Jan Kara <jack@...e.cz>,
        Amir Goldstein <amir73il@...il.com>
Cc:     linux-mm@...ck.org, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Shakeel Butt <shakeelb@...gle.com>
Subject: [PATCH 1/2] memcg, oom: no oom-kill for __GFP_RETRY_MAYFAIL

The documentation of __GFP_RETRY_MAYFAIL clearly mentioned that the
OOM killer will not be triggered and indeed the page alloc does not
invoke OOM killer for such allocations. However we do trigger memcg
OOM killer for __GFP_RETRY_MAYFAIL. Fix that. This flag will used later
to not trigger oom-killer in the charging path for fanotify and inotify
event allocations.

Signed-off-by: Shakeel Butt <shakeelb@...gle.com>
Acked-by: Michal Hocko <mhocko@...e.com>
---
Changelog since v1:
- commit message updated.

 mm/memcontrol.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 2713b45ec3f0..99eca724ed3b 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2294,7 +2294,6 @@ static int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
 	unsigned long nr_reclaimed;
 	bool may_swap = true;
 	bool drained = false;
-	bool oomed = false;
 	enum oom_status oom_status;
 
 	if (mem_cgroup_is_root(memcg))
@@ -2381,7 +2380,7 @@ static int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
 	if (nr_retries--)
 		goto retry;
 
-	if (gfp_mask & __GFP_RETRY_MAYFAIL && oomed)
+	if (gfp_mask & __GFP_RETRY_MAYFAIL)
 		goto nomem;
 
 	if (gfp_mask & __GFP_NOFAIL)
@@ -2400,7 +2399,6 @@ static int try_charge(struct mem_cgroup *memcg, gfp_t gfp_mask,
 	switch (oom_status) {
 	case OOM_SUCCESS:
 		nr_retries = MEM_CGROUP_RECLAIM_RETRIES;
-		oomed = true;
 		goto retry;
 	case OOM_FAILED:
 		goto force;
-- 
2.21.0.593.g511ec345e18-goog