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memcg: move mem_cgroup_swappiness and vm_swappiness to mm/swap.h

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Patch series "mm: vmscan: fix node reclaim ignoring swappiness parameter",
v4.

The per-node proactive reclaim interface
(/sys/devices/system/node/nodeX/reclaim) accepts a swappiness parameter,
but it is silently ignored when CONFIG_MEMCG is disabled.  The root cause
is that sc_swappiness() has separate implementations for CONFIG_MEMCG and
!CONFIG_MEMCG, and the latter never checks proactive_swappiness.

Patch 1 moves mem_cgroup_swappiness() and vm_swappiness out of the public
include/linux/swap.h into the mm-private mm/swap.h, and makes the helper
handle both CONFIG_MEMCG and !CONFIG_MEMCG in a single inline function. 
This is a prerequisite for unifying sc_swappiness().

Patch 2 consolidates sc_swappiness() into a single definition that works
regardless of CONFIG_MEMCG, fixing the node reclaim swappiness bug.


This patch (of 2):

The per-memcg swappiness knob is v1-only; v2 always uses global
vm_swappiness and ignores the per-cgroup field.

Both mem_cgroup_swappiness() and vm_swappiness are only used within mm/
(memcontrol.c, memcontrol-v1.c, vmscan.c), so move them out of the public
include/linux/swap.h into the mm-private mm/swap.h.  This keeps unrelated
declarations out of include/linux/swap.h.

Guard memcg->swappiness with CONFIG_MEMCG_V1 as well, so v2-only
kernels drop the unused field.

No functional change for v1; v2-only kernels drop the unused field.

Link: https://lore.kernel.org/20260723032434.2016749-1-ridong.chen@linux.dev
Link: https://lore.kernel.org/20260723032434.2016749-2-ridong.chen@linux.dev
Signed-off-by: Ridong Chen <chenridong@xiaomi.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Barry Song <baohua@kernel.org>
Reviewed-by: Song Hu <husong@kylinos.cn>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Baoquan He <baoquan.he@linux.dev>
Cc: Chris Li <chrisl@kernel.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Kairui Song <kasong@tencent.com>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Wei Xu <weixugc@google.com>
Cc: Yuanchu Xie <yuanchu@google.com>
Cc: Qi Zheng <qi.zheng@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Ridong Chen 2026-07-23 11:24:33 +08:00 committed by Andrew Morton
parent 0ee06ee38a
commit 1b7c8fe294
4 changed files with 18 additions and 23 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
include/linux/memcontrol.h
View File

@ -239,8 +239,6 @@ struct mem_cgroup {
*/
bool oom_group;
int swappiness;
/* memory.events and memory.events.local */
struct cgroup_file events_file;
struct cgroup_file events_local_file;
@ -318,6 +316,8 @@ struct mem_cgroup {
/* List of events which userspace want to receive */
struct list_head event_list;
spinlock_t event_list_lock;
int swappiness;
#endif /* CONFIG_MEMCG_V1 */
struct mem_cgroup_per_node *nodeinfo[];

19
include/linux/swap.h
View File

@ -309,7 +309,6 @@ static inline bool lru_cache_disabled(void)
}
extern unsigned long shrink_all_memory(unsigned long nr_pages);
extern int vm_swappiness;
long remove_mapping(struct address_space *mapping, struct folio *folio);
#if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
@ -468,25 +467,7 @@ static inline int add_swap_extent(struct swap_info_struct *sis,
}
#endif /* CONFIG_SWAP */
#ifdef CONFIG_MEMCG
static inline int mem_cgroup_swappiness(struct mem_cgroup *memcg)
{
/* Cgroup2 doesn't have per-cgroup swappiness */
if (cgroup_subsys_on_dfl(memory_cgrp_subsys))
return READ_ONCE(vm_swappiness);
/* root ? */
if (mem_cgroup_disabled() || mem_cgroup_is_root(memcg))
return READ_ONCE(vm_swappiness);
return READ_ONCE(memcg->swappiness);
}
void lru_reparent_memcg(struct mem_cgroup *memcg, struct mem_cgroup *parent, int nid);
#else
static inline int mem_cgroup_swappiness(struct mem_cgroup *memcg)
{
return READ_ONCE(vm_swappiness);
}
#endif
#if defined(CONFIG_SWAP) && defined(CONFIG_MEMCG) && defined(CONFIG_BLK_CGROUP)

4
mm/memcontrol.c
View File

@ -63,6 +63,7 @@
#include <linux/sched/isolation.h>
#include <linux/kmemleak.h>
#include "internal.h"
#include "swap.h"
#include "swap_table.h"
#include <net/sock.h>
#include <net/ip.h>
@ -4176,11 +4177,10 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
#endif
page_counter_set_high(&memcg->swap, PAGE_COUNTER_MAX);
if (parent) {
WRITE_ONCE(memcg->swappiness, mem_cgroup_swappiness(parent));
page_counter_init(&memcg->memory, &parent->memory, memcg_on_dfl);
page_counter_init(&memcg->swap, &parent->swap, false);
#ifdef CONFIG_MEMCG_V1
WRITE_ONCE(memcg->swappiness, mem_cgroup_swappiness(parent));
memcg->memory.track_failcnt = !memcg_on_dfl;
memcg->memsw.track_failcnt = !memcg_on_dfl;
WRITE_ONCE(memcg->oom_kill_disable, READ_ONCE(parent->oom_kill_disable));

14
mm/swap.h
View File

@ -4,6 +4,8 @@
#include <linux/atomic.h> /* for atomic_long_t */
#include <linux/mm.h> /* for PAGE_SHIFT */
#include <linux/memcontrol.h> /* for mem_cgroup_swappiness() */
struct mempolicy;
struct swap_iocb;
struct swap_memcg_table;
@ -76,6 +78,18 @@ enum swap_cluster_flags {
CLUSTER_FLAG_MAX,
};
extern int vm_swappiness;
static inline int mem_cgroup_swappiness(struct mem_cgroup *memcg)
{
#ifdef CONFIG_MEMCG_V1
if (!cgroup_subsys_on_dfl(memory_cgrp_subsys) &&
!mem_cgroup_disabled() && !mem_cgroup_is_root(memcg))
return READ_ONCE(memcg->swappiness);
#endif
return READ_ONCE(vm_swappiness);
}
#ifdef CONFIG_SWAP
#include <linux/swapops.h> /* for swp_offset */
#include <linux/blk_types.h> /* for bio_end_io_t */