mm/memcg, swap: tidy up cgroup v1 memsw swap helpers

The cgroup v1 swap helpers always operate on swap cache folios whose swap
entry is stable: the folio is locked and in the swap cache.  There is no
need to pass the swap entry or page count as separate parameters when they
can be derived from the folio itself.

Simplify the redundant parameters and add sanity checks to document the
required preconditions.

Also rename memcg1_swapout to __memcg1_swapout to indicate it requires
special calling context: the folio must be isolated and dying, and the
call must be made with interrupts disabled.

No functional change.

Link: https://lore.kernel.org/20260517-swap-table-p4-v5-6-88ae43e064c7@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>

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index dc3fa687759b45748b2acee6d7f43da325eb50c1..7d08128de1fdc44e507075ca675380a370fb56e2 100644 (file)
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -1899,8 +1899,8 @@ static inline void mem_cgroup_exit_user_fault(void)
        current->in_user_fault = 0;
 }
 
-void memcg1_swapout(struct folio *folio, swp_entry_t entry);
-void memcg1_swapin(swp_entry_t entry, unsigned int nr_pages);
+void __memcg1_swapout(struct folio *folio);
+void memcg1_swapin(struct folio *folio);
 
 #else /* CONFIG_MEMCG_V1 */
 static inline
@@ -1929,11 +1929,11 @@ static inline void mem_cgroup_exit_user_fault(void)
 {
 }
 
-static inline void memcg1_swapout(struct folio *folio, swp_entry_t entry)
+static inline void __memcg1_swapout(struct folio *folio)
 {
 }
 
-static inline void memcg1_swapin(swp_entry_t entry, unsigned int nr_pages)
+static inline void memcg1_swapin(struct folio *folio)
 {
 }
 

diff --git a/include/linux/swap.h b/include/linux/swap.h
index 7a09df6977a5f36fb040662fa93d2328daaa34ec..f907d3df52d0f0b13d531e311e4a8c8878e86a39 100644 (file)
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -571,13 +571,12 @@ static inline void folio_throttle_swaprate(struct folio *folio, gfp_t gfp)
 #endif
 
 #if defined(CONFIG_MEMCG) && defined(CONFIG_SWAP)
-int __mem_cgroup_try_charge_swap(struct folio *folio, swp_entry_t entry);
-static inline int mem_cgroup_try_charge_swap(struct folio *folio,
-               swp_entry_t entry)
+int __mem_cgroup_try_charge_swap(struct folio *folio);
+static inline int mem_cgroup_try_charge_swap(struct folio *folio)
 {
        if (mem_cgroup_disabled())
                return 0;
-       return __mem_cgroup_try_charge_swap(folio, entry);
+       return __mem_cgroup_try_charge_swap(folio);
 }
 
 extern void __mem_cgroup_uncharge_swap(swp_entry_t entry, unsigned int nr_pages);
@@ -591,8 +590,7 @@ static inline void mem_cgroup_uncharge_swap(swp_entry_t entry, unsigned int nr_p
 extern long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg);
 extern bool mem_cgroup_swap_full(struct folio *folio);
 #else
-static inline int mem_cgroup_try_charge_swap(struct folio *folio,
-                                            swp_entry_t entry)
+static inline int mem_cgroup_try_charge_swap(struct folio *folio)
 {
        return 0;
 }

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index b7df167f7acbf26a77b3034dd0f35fe77bf6217d..1f14c5c48b4a43db6870063720c7552dc8c3ccc6 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -4446,7 +4446,7 @@ void deferred_split_folio(struct folio *folio, bool partially_mapped)
 
        /*
         * Exclude swapcache: originally to avoid a corrupt deferred split
-        * queue. Nowadays that is fully prevented by memcg1_swapout();
+        * queue. Nowadays that is fully prevented by __memcg1_swapout();
         * but if page reclaim is already handling the same folio, it is
         * unnecessary to handle it again in the shrinker, so excluding
         * swapcache here may still be a useful optimization.

diff --git a/mm/memcontrol-v1.c b/mm/memcontrol-v1.c
index 433bba9dfe715c9dbab878bd119ce23c59ac326e..36c507d81dc514d75c737cb8980e8060415fbd7a 100644 (file)
--- a/mm/memcontrol-v1.c
+++ b/mm/memcontrol-v1.c
@@ -604,18 +604,23 @@ void memcg1_commit_charge(struct folio *folio, struct mem_cgroup *memcg)
 }
 
 /**
- * memcg1_swapout - transfer a memsw charge to swap
+ * __memcg1_swapout - transfer a memsw charge to swap
  * @folio: folio whose memsw charge to transfer
- * @entry: swap entry to move the charge to
  *
- * Transfer the memsw charge of @folio to @entry.
+ * Transfer the memsw charge of @folio to the swap entry stored in
+ * folio->swap.
+ *
+ * Context: folio must be isolated, unmapped, locked and is just about
+ * to be freed, and caller must disable IRQs.
  */
-void memcg1_swapout(struct folio *folio, swp_entry_t entry)
+void __memcg1_swapout(struct folio *folio)
 {
        struct mem_cgroup *memcg, *swap_memcg;
        struct obj_cgroup *objcg;
        unsigned int nr_entries;
 
+       VM_WARN_ON_ONCE_FOLIO(!folio_test_swapcache(folio), folio);
+       VM_WARN_ON_ONCE_FOLIO(!folio_test_locked(folio), folio);
        VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
        VM_BUG_ON_FOLIO(folio_ref_count(folio), folio);
 
@@ -641,7 +646,7 @@ void memcg1_swapout(struct folio *folio, swp_entry_t entry)
        swap_memcg = mem_cgroup_private_id_get_online(memcg, nr_entries);
        mod_memcg_state(swap_memcg, MEMCG_SWAP, nr_entries);
 
-       swap_cgroup_record(folio, mem_cgroup_private_id(swap_memcg), entry);
+       swap_cgroup_record(folio, mem_cgroup_private_id(swap_memcg), folio->swap);
 
        folio_unqueue_deferred_split(folio);
        folio->memcg_data = 0;
@@ -671,18 +676,20 @@ void memcg1_swapout(struct folio *folio, swp_entry_t entry)
        obj_cgroup_put(objcg);
 }
 
-/*
+/**
  * memcg1_swapin - uncharge swap slot
- * @entry: the first swap entry for which the pages are charged
- * @nr_pages: number of pages which will be uncharged
+ * @folio: folio being swapped in
  *
- * Call this function after successfully adding the charged page to swapcache.
+ * Call this function after successfully adding the charged
+ * folio to swapcache.
  *
- * Note: This function assumes the page for which swap slot is being uncharged
- * is order 0 page.
+ * Context: The folio has to be in swap cache and locked.
  */
-void memcg1_swapin(swp_entry_t entry, unsigned int nr_pages)
+void memcg1_swapin(struct folio *folio)
 {
+       VM_WARN_ON_ONCE_FOLIO(!folio_test_swapcache(folio), folio);
+       VM_WARN_ON_ONCE_FOLIO(!folio_test_locked(folio), folio);
+
        /*
         * Cgroup1's unified memory+swap counter has been charged with the
         * new swapcache page, finish the transfer by uncharging the swap
@@ -701,7 +708,7 @@ void memcg1_swapin(swp_entry_t entry, unsigned int nr_pages)
                 * let's not wait for it.  The page already received a
                 * memory+swap charge, drop the swap entry duplicate.
                 */
-               mem_cgroup_uncharge_swap(entry, nr_pages);
+               mem_cgroup_uncharge_swap(folio->swap, folio_nr_pages(folio));
        }
 }
 

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 431cad99189f97ab14f5c8b4130363c2cecafbd1..c3d0f79dc84e1cb979ce5c60bf3eb2df974f5320 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5473,13 +5473,12 @@ int __init mem_cgroup_init(void)
 /**
  * __mem_cgroup_try_charge_swap - try charging swap space for a folio
  * @folio: folio being added to swap
- * @entry: swap entry to charge
  *
- * Try to charge @folio's memcg for the swap space at @entry.
+ * Try to charge @folio's memcg for the swap space at folio->swap.
  *
  * Returns 0 on success, -ENOMEM on failure.
  */
-int __mem_cgroup_try_charge_swap(struct folio *folio, swp_entry_t entry)
+int __mem_cgroup_try_charge_swap(struct folio *folio)
 {
        unsigned int nr_pages = folio_nr_pages(folio);
        struct page_counter *counter;
@@ -5496,7 +5495,7 @@ int __mem_cgroup_try_charge_swap(struct folio *folio, swp_entry_t entry)
 
        rcu_read_lock();
        memcg = obj_cgroup_memcg(objcg);
-       if (!entry.val) {
+       if (!folio_test_swapcache(folio)) {
                memcg_memory_event(memcg, MEMCG_SWAP_FAIL);
                rcu_read_unlock();
                return 0;
@@ -5515,7 +5514,7 @@ int __mem_cgroup_try_charge_swap(struct folio *folio, swp_entry_t entry)
        }
        mod_memcg_state(memcg, MEMCG_SWAP, nr_pages);
 
-       swap_cgroup_record(folio, mem_cgroup_private_id(memcg), entry);
+       swap_cgroup_record(folio, mem_cgroup_private_id(memcg), folio->swap);
 
        return 0;
 }

diff --git a/mm/swap_state.c b/mm/swap_state.c
index 98c8691826fb51746120d582a27a83461e963142..7a80494fa37fbd439040c97689ee8a23492b8a74 100644 (file)
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -455,8 +455,8 @@ static struct folio *__swap_cache_alloc(struct swap_cluster_info *ci,
                return ERR_PTR(-ENOMEM);
        }
 
-       /* For memsw accounting, swap is uncharged when folio is added to swap cache */
-       memcg1_swapin(entry, 1 << order);
+       /* memsw uncharges swap when folio is added to swap cache */
+       memcg1_swapin(folio);
        if (shadow)
                workingset_refault(folio, shadow);
 

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 4ffd491cacca52880dd18dbced24ca80df0f136d..4875b3d3e6588678edd4259427f34a25800eed23 100644 (file)
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -1757,7 +1757,7 @@ again:
        }
 
        /* Need to call this even if allocation failed, for MEMCG_SWAP_FAIL. */
-       if (unlikely(mem_cgroup_try_charge_swap(folio, folio->swap)))
+       if (unlikely(mem_cgroup_try_charge_swap(folio)))
                swap_cache_del_folio(folio);
 
        if (unlikely(!folio_test_swapcache(folio)))

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 4b09843876583abc6624d5d2ba972b5abd079af2..3231af682fa739c1d7c2132f5cb28591e426a608 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -739,7 +739,7 @@ static int __remove_mapping(struct address_space *mapping, struct folio *folio,
 
                if (reclaimed && !mapping_exiting(mapping))
                        shadow = workingset_eviction(folio, target_memcg);
-               memcg1_swapout(folio, swap);
+               __memcg1_swapout(folio);
                __swap_cache_del_folio(ci, folio, swap, shadow);
                swap_cluster_unlock_irq(ci);
        } else {