mm: thp: replace folio_memcg() with folio_memcg_charged()

Patch series "reparent the THP split queue", v6.

In the future, we will reparent LRU folios during memcg offline to
eliminate dying memory cgroups, which requires reparenting the THP split
queue to its parent memcg.

Similar to list_lru, the split queue is relatively independent and does
not need to be reparented along with objcg and LRU folios (holding objcg
lock and lru lock).  Therefore, we can apply the same mechanism as
list_lru to reparent the split queue first when memcg is offine.

The first three patches in this series are separated from the series
"Eliminate Dying Memory Cgroup" [1], mainly to do some cleanup and
preparatory work.

The last patch reparents the THP split queue to its parent memcg during
memcg offline.

This patch (of 4):

folio_memcg_charged() is intended for use when the user is unconcerned
about the returned memcg pointer.  It is more efficient than
folio_memcg().  Therefore, replace folio_memcg() with
folio_memcg_charged().

Link: https://lkml.kernel.org/r/56624d537520e33e5a6b3755238b3dfb959a52ee.1762762324.git.zhengqi.arch@bytedance.com
Link: https://lore.kernel.org/all/20250415024532.26632-1-songmuchun@bytedance.com/
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>
Reviewed-by: Harry Yoo <harry.yoo@oracle.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Nico Pache <npache@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Muchun Song <muchun.song@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index e38b0d5e3102fa10bd08481b9933578b15d733f8..9758171d49c99618397f1e20153f35b2fa20e68c 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -4127,7 +4127,7 @@ bool __folio_unqueue_deferred_split(struct folio *folio)
        bool unqueued = false;
 
        WARN_ON_ONCE(folio_ref_count(folio));
-       WARN_ON_ONCE(!mem_cgroup_disabled() && !folio_memcg(folio));
+       WARN_ON_ONCE(!mem_cgroup_disabled() && !folio_memcg_charged(folio));
 
        ds_queue = get_deferred_split_queue(folio);
        spin_lock_irqsave(&ds_queue->split_queue_lock, flags);