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memcg: workingset: remove folio_memcg_rcu usage 

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.

[akpm@linux-foundation.org: provide folio_memcg_charged stub for CONFIG_MEMCG=n]
Link: https://lkml.kernel.org/r/20241026163707.2479526-1-shakeel.butt@linux.dev
Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Suggested-by: Yu Zhao <yuzhao@google.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
pull/1085/head
Shakeel Butt 2024-10-26 09:37:07 -07:00 committed by Andrew Morton
parent 642c66d84c
commit 906c38ff52
2 changed files with 4 additions and 44 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

34
include/linux/memcontrol.h
View File

@ -443,35 +443,6 @@ static inline bool folio_memcg_charged(struct folio *folio)
return __folio_memcg(folio) != NULL; 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_memcg_check - Get the memory cgroup associated with a folio.
* @folio: Pointer to the folio. * @folio: Pointer to the folio.
@ -1084,10 +1055,9 @@ static inline struct mem_cgroup *folio_memcg(struct folio *folio)
return NULL; 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 false;
return NULL;
} }
static inline struct mem_cgroup *folio_memcg_check(struct folio *folio) static inline struct mem_cgroup *folio_memcg_check(struct folio *folio)

12
mm/workingset.c
View File

@ -591,22 +591,12 @@ void workingset_refault(struct folio *folio, void *shadow)
*/ */
void workingset_activation(struct folio *folio) void workingset_activation(struct folio *folio)
{ {
struct mem_cgroup *memcg;
rcu_read_lock();
/* /*
* Filter non-memcg pages here, e.g. unmap can call * Filter non-memcg pages here, e.g. unmap can call
* mark_page_accessed() on VDSO pages. * 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() || folio_memcg_charged(folio))
if (!mem_cgroup_disabled() && !memcg)
goto out;
workingset_age_nonresident(folio_lruvec(folio), folio_nr_pages(folio)); workingset_age_nonresident(folio_lruvec(folio), folio_nr_pages(folio));
out:
rcu_read_unlock();
} }
/* /*