The patch titled
Subject: memcg: workingset: remove folio_memcg_rcu usage
has been added to the -mm mm-unstable branch. Its filename is
memcg-workingset-remove-folio_memcg_rcu-usage.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/memcg-workingset-remove-folio_memcg_rcu-usage.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Shakeel Butt <shakeel.butt@xxxxxxxxx>
Subject: memcg: workingset: remove folio_memcg_rcu usage
Date: Sat, 26 Oct 2024 09:37:07 -0700
The function workingset_activation() is called from folio_mark_accessed()
with the guarantee that the given folio can not be freed under us in
workingset_activation(). In addition, the association of the folio and
its memcg can not be broken here because charge migration is no more.
There is no need to use folio_memcg_rcu. Simply use folio_memcg_charged()
because that is what this function cares about.
Link: https://lkml.kernel.org/r/20241026163707.2479526-1-shakeel.butt@xxxxxxxxx
Signed-off-by: Shakeel Butt <shakeel.butt@xxxxxxxxx>
Suggested-by: Yu Zhao <yuzhao@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Roman Gushchin <roman.gushchin@xxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Muchun Song <songmuchun@xxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Yosry Ahmed <yosryahmed@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/memcontrol.h | 35 -----------------------------------
mm/workingset.c | 14 ++------------
2 files changed, 2 insertions(+), 47 deletions(-)
--- a/include/linux/memcontrol.h~memcg-workingset-remove-folio_memcg_rcu-usage
+++ a/include/linux/memcontrol.h
@@ -443,35 +443,6 @@ static inline bool folio_memcg_charged(s
return __folio_memcg(folio) != NULL;
}
-/**
- * folio_memcg_rcu - Locklessly get the memory cgroup associated with a folio.
- * @folio: Pointer to the folio.
- *
- * This function assumes that the folio is known to have a
- * proper memory cgroup pointer. It's not safe to call this function
- * against some type of folios, e.g. slab folios or ex-slab folios.
- *
- * Return: A pointer to the memory cgroup associated with the folio,
- * or NULL.
- */
-static inline struct mem_cgroup *folio_memcg_rcu(struct folio *folio)
-{
- unsigned long memcg_data = READ_ONCE(folio->memcg_data);
-
- VM_BUG_ON_FOLIO(folio_test_slab(folio), folio);
-
- if (memcg_data & MEMCG_DATA_KMEM) {
- struct obj_cgroup *objcg;
-
- objcg = (void *)(memcg_data & ~OBJEXTS_FLAGS_MASK);
- return obj_cgroup_memcg(objcg);
- }
-
- WARN_ON_ONCE(!rcu_read_lock_held());
-
- return (struct mem_cgroup *)(memcg_data & ~OBJEXTS_FLAGS_MASK);
-}
-
/*
* folio_memcg_check - Get the memory cgroup associated with a folio.
* @folio: Pointer to the folio.
@@ -1084,12 +1055,6 @@ static inline struct mem_cgroup *folio_m
return NULL;
}
-static inline struct mem_cgroup *folio_memcg_rcu(struct folio *folio)
-{
- WARN_ON_ONCE(!rcu_read_lock_held());
- return NULL;
-}
-
static inline struct mem_cgroup *folio_memcg_check(struct folio *folio)
{
return NULL;
--- a/mm/workingset.c~memcg-workingset-remove-folio_memcg_rcu-usage
+++ a/mm/workingset.c
@@ -591,22 +591,12 @@ void workingset_refault(struct folio *fo
*/
void workingset_activation(struct folio *folio)
{
- struct mem_cgroup *memcg;
-
- rcu_read_lock();
/*
* Filter non-memcg pages here, e.g. unmap can call
* mark_page_accessed() on VDSO pages.
- *
- * XXX: See workingset_refault() - this should return
- * root_mem_cgroup even for !CONFIG_MEMCG.
*/
- memcg = folio_memcg_rcu(folio);
- if (!mem_cgroup_disabled() && !memcg)
- goto out;
- workingset_age_nonresident(folio_lruvec(folio), folio_nr_pages(folio));
-out:
- rcu_read_unlock();
+ if (mem_cgroup_disabled() || folio_memcg_charged(folio))
+ workingset_age_nonresident(folio_lruvec(folio), folio_nr_pages(folio));
}
/*
_
Patches currently in -mm which might be from shakeel.butt@xxxxxxxxx are
mm-optimize-truncation-of-shadow-entries.patch
mm-optimize-invalidation-of-shadow-entries.patch
mm-truncate-reset-xa_has_values-flag-on-each-iteration.patch
memcg-add-tracing-for-memcg-stat-updates.patch
memcg-add-tracing-for-memcg-stat-updates-v2.patch
memcg-v1-fully-deprecate-move_charge_at_immigrate.patch
memcg-v1-remove-charge-move-code.patch
memcg-v1-no-need-for-memcg-locking-for-dirty-tracking.patch
memcg-v1-no-need-for-memcg-locking-for-writeback-tracking.patch
memcg-v1-no-need-for-memcg-locking-for-mglru.patch
memcg-v1-remove-memcg-move-locking-code.patch
memcg-workingset-remove-folio_memcg_rcu-usage.patch
