[merged mm-stable] mm-memcg-prevent-memoryoom_control-load-store-tearing.patch removed from -mm tree

[merged mm-stable] mm-memcg-prevent-memoryoom_control-load-store-tearing.patch removed from -mm tree

[Andrew Morton]

The quilt patch titled
     Subject: mm, memcg: prevent memory.oom_control load/store tearing
has been removed from the -mm tree.  Its filename was
     mm-memcg-prevent-memoryoom_control-load-store-tearing.patch

This patch was dropped because it was merged into the mm-stable branch
of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

------------------------------------------------------
From: Yue Zhao <findns94@gmail.com>
Subject: mm, memcg: Prevent memory.oom_control load/store tearing
Date: Mon, 6 Mar 2023 23:41:37 +0800

The knob for cgroup v1 memory controller: memory.oom_control is not
protected by any locking so it can be modified while it is used.  This is
not an actual problem because races are unlikely.  But it is better to use
[READ|WRITE]_ONCE to prevent compiler from doing anything funky.

The access of memcg->oom_kill_disable is lockless, so it can be
concurrently set at the same time as we are trying to read it.  All
occurrences of memcg->oom_kill_disable are updated with [READ|WRITE]_ONCE.

[findns94@gmail.com: v3]
  Link: https://lkml.kernel.org/r/20230308162555.14195-4-findns94@gmail.com
Link: https://lkml.kernel.org/r/20230306154138.377-4-findns94@gmail.com
Signed-off-by: Yue Zhao <findns94@gmail.com>
Acked-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Tang Yizhou <tangyeechou@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/memcontrol.c |   10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

--- a/mm/memcontrol.c~mm-memcg-prevent-memoryoom_control-load-store-tearing
+++ a/mm/memcontrol.c
@@ -1929,7 +1929,7 @@ static bool mem_cgroup_oom(struct mem_cg
 	 * Please note that mem_cgroup_out_of_memory might fail to find a
 	 * victim and then we have to bail out from the charge path.
 	 */
-	if (memcg->oom_kill_disable) {
+	if (READ_ONCE(memcg->oom_kill_disable)) {
 		if (current->in_user_fault) {
 			css_get(&memcg->css);
 			current->memcg_in_oom = memcg;
@@ -1999,7 +1999,7 @@ bool mem_cgroup_oom_synchronize(bool han
 	if (locked)
 		mem_cgroup_oom_notify(memcg);
 
-	if (locked && !memcg->oom_kill_disable) {
+	if (locked && !READ_ONCE(memcg->oom_kill_disable)) {
 		mem_cgroup_unmark_under_oom(memcg);
 		finish_wait(&memcg_oom_waitq, &owait.wait);
 		mem_cgroup_out_of_memory(memcg, current->memcg_oom_gfp_mask,
@@ -4515,7 +4515,7 @@ static int mem_cgroup_oom_control_read(s
 {
 	struct mem_cgroup *memcg = mem_cgroup_from_seq(sf);
 
-	seq_printf(sf, "oom_kill_disable %d\n", memcg->oom_kill_disable);
+	seq_printf(sf, "oom_kill_disable %d\n", READ_ONCE(memcg->oom_kill_disable));
 	seq_printf(sf, "under_oom %d\n", (bool)memcg->under_oom);
 	seq_printf(sf, "oom_kill %lu\n",
 		   atomic_long_read(&memcg->memory_events[MEMCG_OOM_KILL]));
@@ -4531,7 +4531,7 @@ static int mem_cgroup_oom_control_write(
 	if (mem_cgroup_is_root(memcg) || !((val == 0) || (val == 1)))
 		return -EINVAL;
 
-	memcg->oom_kill_disable = val;
+	WRITE_ONCE(memcg->oom_kill_disable, val);
 	if (!val)
 		memcg_oom_recover(memcg);
 
@@ -5354,7 +5354,7 @@ mem_cgroup_css_alloc(struct cgroup_subsy
 	page_counter_set_high(&memcg->swap, PAGE_COUNTER_MAX);
 	if (parent) {
 		WRITE_ONCE(memcg->swappiness, mem_cgroup_swappiness(parent));
-		memcg->oom_kill_disable = parent->oom_kill_disable;
+		WRITE_ONCE(memcg->oom_kill_disable, READ_ONCE(parent->oom_kill_disable));
 
 		page_counter_init(&memcg->memory, &parent->memory);
 		page_counter_init(&memcg->swap, &parent->swap);
_

Patches currently in -mm which might be from findns94@gmail.com are