mm, swap: delay and unify memcg lookup and charging for swapin

Instead of checking the cgroup private ID during page table walk in
swap_pte_batch(), move the memcg lookup into __swap_cache_add_check()
under the cluster lock.

The first pre-alloc check is speculative and skips the memcg check since
the post-alloc stable check ensures all slots covered by the folio belong
to the same memcg.  It is very rare for contiguous and aligned entries
across a contiguous region of a page table of the same process or shmem
mapping to belong to different memcgs.

This also prepares for recording the memcg info in the cluster's table. 
Also make the order check and fallback more compact.

There should be no user-observable behavior change.

Link: https://lore.kernel.org/20260517-swap-table-p4-v5-8-88ae43e064c7@tencent.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Acked-by: Chris Li <chrisl@kernel.org>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Barry Song <baohua@kernel.org>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: David Hildenbrand <david@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Youngjun Park <youngjun.park@lge.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 3 insertions, 3 deletions

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 7d08128de1fd..a013f37f24aa 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -646,8 +646,8 @@ static inline int mem_cgroup_charge(struct folio *folio, struct mm_struct *mm,
 
 int mem_cgroup_charge_hugetlb(struct folio* folio, gfp_t gfp);
 
-int mem_cgroup_swapin_charge_folio(struct folio *folio, struct mm_struct *mm,
-				  gfp_t gfp, swp_entry_t entry);
+int mem_cgroup_swapin_charge_folio(struct folio *folio, unsigned short id,
+				   struct mm_struct *mm, gfp_t gfp);
 
 void __mem_cgroup_uncharge(struct folio *folio);
 
@@ -1137,7 +1137,7 @@ static inline int mem_cgroup_charge_hugetlb(struct folio* folio, gfp_t gfp)
 }
 
 static inline int mem_cgroup_swapin_charge_folio(struct folio *folio,
-			struct mm_struct *mm, gfp_t gfp, swp_entry_t entry)
+		 unsigned short id, struct mm_struct *mm, gfp_t gfp)
 {
 	return 0;
 }