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

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

[Andrew Morton]

The quilt patch titled
     Subject: mm, memcg: prevent memory.swappiness load/store tearing
has been removed from the -mm tree.  Its filename was
     mm-memcg-prevent-memoryswappiness-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.swappiness load/store tearing
Date: Mon, 6 Mar 2023 23:41:36 +0800

The knob for cgroup v1 memory controller: memory.swappiness 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->swappiness and vm_swappiness is lockless, so both of
them can be concurrently set at the same time as we are trying to read
them.  All occurrences of memcg->swappiness and vm_swappiness are updated
with [READ|WRITE]_ONCE.

[findns94@gmail.com: v3]
  Link: https://lkml.kernel.org/r/20230308162555.14195-3-findns94@gmail.com
Link: https://lkml.kernel.org/r/20230306154138.3775-3-findns94@gmail.com
Signed-off-by: Yue Zhao <findns94@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
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>
---

 include/linux/swap.h |    8 ++++----
 mm/memcontrol.c      |    6 +++---
 2 files changed, 7 insertions(+), 7 deletions(-)

--- a/include/linux/swap.h~mm-memcg-prevent-memoryswappiness-load-store-tearing
+++ a/include/linux/swap.h
@@ -620,18 +620,18 @@ static inline int mem_cgroup_swappiness(
 {
 	/* Cgroup2 doesn't have per-cgroup swappiness */
 	if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
-		return vm_swappiness;
+		return READ_ONCE(vm_swappiness);
 
 	/* root ? */
 	if (mem_cgroup_disabled() || mem_cgroup_is_root(memcg))
-		return vm_swappiness;
+		return READ_ONCE(vm_swappiness);
 
-	return memcg->swappiness;
+	return READ_ONCE(memcg->swappiness);
 }
 #else
 static inline int mem_cgroup_swappiness(struct mem_cgroup *mem)
 {
-	return vm_swappiness;
+	return READ_ONCE(vm_swappiness);
 }
 #endif
 
--- a/mm/memcontrol.c~mm-memcg-prevent-memoryswappiness-load-store-tearing
+++ a/mm/memcontrol.c
@@ -4179,9 +4179,9 @@ static int mem_cgroup_swappiness_write(s
 		return -EINVAL;
 
 	if (!mem_cgroup_is_root(memcg))
-		memcg->swappiness = val;
+		WRITE_ONCE(memcg->swappiness, val);
 	else
-		vm_swappiness = val;
+		WRITE_ONCE(vm_swappiness, val);
 
 	return 0;
 }
@@ -5353,7 +5353,7 @@ mem_cgroup_css_alloc(struct cgroup_subsy
 #endif
 	page_counter_set_high(&memcg->swap, PAGE_COUNTER_MAX);
 	if (parent) {
-		memcg->swappiness = mem_cgroup_swappiness(parent);
+		WRITE_ONCE(memcg->swappiness, mem_cgroup_swappiness(parent));
 		memcg->oom_kill_disable = parent->oom_kill_disable;
 
 		page_counter_init(&memcg->memory, &parent->memory);
_

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