patches/old/mm-kmem-add-direct-objcg-pointer-to-task_struct-v4.patch

From: Roman Gushchin <roman.gushchin@linux.dev>
Subject: mm-kmem-add-direct-objcg-pointer-to-task_struct-v4
Date: Wed, 18 Oct 2023 11:08:20 -0700

add comment, s/0/CURRENT_OBJCG_UPDATE_BIT/

Link: https://lkml.kernel.org/r/ZTAfFOsvlbqPI0Uk@P9FQF9L96D.corp.robot.car
Signed-off-by: Roman Gushchin (Cruise) <roman.gushchin@linux.dev>
Tested-by: Naresh Kamboju <naresh.kamboju@linaro.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/memcontrol.c |   12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

--- a/mm/memcontrol.c~mm-kmem-add-direct-objcg-pointer-to-task_struct-v4
+++ a/mm/memcontrol.c
@@ -249,7 +249,8 @@ struct mem_cgroup *vmpressure_to_memcg(s
 	return container_of(vmpr, struct mem_cgroup, vmpressure);
 }
 
-#define CURRENT_OBJCG_UPDATE_FLAG 0x1UL
+#define CURRENT_OBJCG_UPDATE_BIT 0
+#define CURRENT_OBJCG_UPDATE_FLAG (1UL << CURRENT_OBJCG_UPDATE_BIT)
 
 #ifdef CONFIG_MEMCG_KMEM
 static DEFINE_SPINLOCK(objcg_lock);
@@ -3126,6 +3127,13 @@ static struct obj_cgroup *current_objcg_
 			old = NULL;
 		}
 
+		/*
+		 * Release the objcg pointer from the previous iteration,
+		 * if try_cmpxcg() below fails.
+		 */
+		if (unlikely(objcg))
+			obj_cgroup_put(objcg);
+
 		/* Obtain the new objcg pointer. */
 		rcu_read_lock();
 		memcg = mem_cgroup_from_task(current);
@@ -6596,7 +6604,7 @@ static void mem_cgroup_kmem_attach(struc
 
 	cgroup_taskset_for_each(task, css, tset) {
 		/* atomically set the update bit */
-		set_bit(0, (unsigned long *)&task->objcg);
+		set_bit(CURRENT_OBJCG_UPDATE_BIT, (unsigned long *)&task->objcg);
 	}
 }
 #else
_