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memcg-workingset-remove-folio_memcg_rcu-usage.patch removed from -mm tree

merged mm-stable Andrew Morton 1 participant 1 message Nov 6, 2024

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The quilt patch titled
Subject: memcg: workingset: remove folio_memcg_rcu usage
has been removed from the -mm tree. Its filename was
memcg-workingset-remove-folio_memcg_rcu-usage.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: Shakeel Butt <[email protected]>
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.

[[email protected]: provide folio_memcg_charged stub for CONFIG_MEMCG=n]
Link https://lkml.kernel.org/r/[email protected] open here
Signed-off-by Shakeel Butt <[email protected]>
Suggested-by Yu Zhao <[email protected]>
Cc Michal Hocko <[email protected]>
Cc Roman Gushchin <[email protected]>
Cc Johannes Weiner <[email protected]>
Cc Muchun Song <[email protected]>
Cc Hugh Dickins <[email protected]>
Cc Yosry Ahmed <[email protected]>
Signed-off-by Andrew Morton <[email protected]>

---

 include/linux/memcontrol.h |   34 ++--------------------------------
 mm/workingset.c            |   14 ++------------
 2 files changed, 4 insertions(+), 44 deletions(-)
include/linux/memcontrol.h renamed from include/linux/memcontrol.h~memcg-workingset-remove-folio_memcg_rcu-usage +2 -32
@@ -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.

@@ -1084,10 +1055,9 @@ static inline struct mem_cgroup *folio_m
 	return NULL;
 }
 
-static inline struct mem_cgroup *folio_memcg_rcu(struct folio *folio)
+static inline bool folio_memcg_charged(struct folio *folio)
 {
-	WARN_ON_ONCE(!rcu_read_lock_held());
-	return NULL;
+	return false;
 }
 
 static inline struct mem_cgroup *folio_memcg_check(struct folio *folio)
mm/workingset.c renamed from mm/workingset.c~memcg-workingset-remove-folio_memcg_rcu-usage +2 -12
@@ -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 [email protected] are