memcg-v1: remove memcg move locking code

The memcg v1's charge move feature has been deprecated.  All the places
using the memcg move lock, have stopped using it as they don't need the
protection any more.  Let's proceed to remove all the locking code related
to charge moving.

Link: https://lkml.kernel.org/r/20241025012304.2473312-7-shakeel.butt@linux.dev
Signed-off-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

5 files changed, 0 insertions, 143 deletions

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 0b113267b2de..bb49e0d4b377 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -299,20 +299,10 @@ struct mem_cgroup {
 	/* For oom notifier event fd */
 	struct list_head oom_notify;
 
-	/* taken only while moving_account > 0 */
-	spinlock_t move_lock;
-	unsigned long move_lock_flags;
-
 	/* Legacy tcp memory accounting */
 	bool tcpmem_active;
 	int tcpmem_pressure;
 
-	/*
-	 * set > 0 if pages under this cgroup are moving to other cgroup.
-	 */
-	atomic_t moving_account;
-	struct task_struct *move_lock_task;
-
 	/* List of events which userspace want to receive */
 	struct list_head event_list;
 	spinlock_t event_list_lock;
@@ -428,9 +418,7 @@ static inline struct obj_cgroup *__folio_objcg(struct folio *folio)
  *
  * - the folio lock
  * - LRU isolation
- * - folio_memcg_lock()
  * - exclusive reference
- * - mem_cgroup_trylock_pages()
  *
  * For a kmem folio a caller should hold an rcu read lock to protect memcg
  * associated with a kmem folio from being released.
@@ -499,9 +487,7 @@ static inline struct mem_cgroup *folio_memcg_rcu(struct folio *folio)
  *
  * - the folio lock
  * - LRU isolation
- * - lock_folio_memcg()
  * - exclusive reference
- * - mem_cgroup_trylock_pages()
  *
  * For a kmem folio a caller should hold an rcu read lock to protect memcg
  * associated with a kmem folio from being released.
@@ -1867,26 +1853,6 @@ static inline bool task_in_memcg_oom(struct task_struct *p)
 	return p->memcg_in_oom;
 }
 
-void folio_memcg_lock(struct folio *folio);
-void folio_memcg_unlock(struct folio *folio);
-
-/* try to stablize folio_memcg() for all the pages in a memcg */
-static inline bool mem_cgroup_trylock_pages(struct mem_cgroup *memcg)
-{
-	rcu_read_lock();
-
-	if (mem_cgroup_disabled() || !atomic_read(&memcg->moving_account))
-		return true;
-
-	rcu_read_unlock();
-	return false;
-}
-
-static inline void mem_cgroup_unlock_pages(void)
-{
-	rcu_read_unlock();
-}
-
 static inline void mem_cgroup_enter_user_fault(void)
 {
 	WARN_ON(current->in_user_fault);
@@ -1908,26 +1874,6 @@ unsigned long memcg1_soft_limit_reclaim(pg_data_t *pgdat, int order,
 	return 0;
 }
 
-static inline void folio_memcg_lock(struct folio *folio)
-{
-}
-
-static inline void folio_memcg_unlock(struct folio *folio)
-{
-}
-
-static inline bool mem_cgroup_trylock_pages(struct mem_cgroup *memcg)
-{
-	/* to match folio_memcg_rcu() */
-	rcu_read_lock();
-	return true;
-}
-
-static inline void mem_cgroup_unlock_pages(void)
-{
-	rcu_read_unlock();
-}
-
 static inline bool task_in_memcg_oom(struct task_struct *p)
 {
 	return false;
diff --git a/mm/filemap.c b/mm/filemap.c
index 630a1c431ea1..e582a1545d2a 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -119,7 +119,6 @@
  *    ->i_pages lock		(folio_remove_rmap_pte->set_page_dirty)
  *    bdi.wb->list_lock		(folio_remove_rmap_pte->set_page_dirty)
  *    ->inode->i_lock		(folio_remove_rmap_pte->set_page_dirty)
- *    ->memcg->move_lock	(folio_remove_rmap_pte->folio_memcg_lock)
  *    bdi.wb->list_lock		(zap_pte_range->set_page_dirty)
  *    ->inode->i_lock		(zap_pte_range->set_page_dirty)
  *    ->private_lock		(zap_pte_range->block_dirty_folio)
diff --git a/mm/memcontrol-v1.c b/mm/memcontrol-v1.c
index 9c0fba8c8a83..539ceefa9d2d 100644
--- a/mm/memcontrol-v1.c
+++ b/mm/memcontrol-v1.c
@@ -401,87 +401,6 @@ unsigned long memcg1_soft_limit_reclaim(pg_data_t *pgdat, int order,
 	return nr_reclaimed;
 }
 
-/**
- * folio_memcg_lock - Bind a folio to its memcg.
- * @folio: The folio.
- *
- * This function prevents unlocked LRU folios from being moved to
- * another cgroup.
- *
- * It ensures lifetime of the bound memcg.  The caller is responsible
- * for the lifetime of the folio.
- */
-void folio_memcg_lock(struct folio *folio)
-{
-	struct mem_cgroup *memcg;
-	unsigned long flags;
-
-	/*
-	 * The RCU lock is held throughout the transaction.  The fast
-	 * path can get away without acquiring the memcg->move_lock
-	 * because page moving starts with an RCU grace period.
-         */
-	rcu_read_lock();
-
-	if (mem_cgroup_disabled())
-		return;
-again:
-	memcg = folio_memcg(folio);
-	if (unlikely(!memcg))
-		return;
-
-#ifdef CONFIG_PROVE_LOCKING
-	local_irq_save(flags);
-	might_lock(&memcg->move_lock);
-	local_irq_restore(flags);
-#endif
-
-	if (atomic_read(&memcg->moving_account) <= 0)
-		return;
-
-	spin_lock_irqsave(&memcg->move_lock, flags);
-	if (memcg != folio_memcg(folio)) {
-		spin_unlock_irqrestore(&memcg->move_lock, flags);
-		goto again;
-	}
-
-	/*
-	 * When charge migration first begins, we can have multiple
-	 * critical sections holding the fast-path RCU lock and one
-	 * holding the slowpath move_lock. Track the task who has the
-	 * move_lock for folio_memcg_unlock().
-	 */
-	memcg->move_lock_task = current;
-	memcg->move_lock_flags = flags;
-}
-
-static void __folio_memcg_unlock(struct mem_cgroup *memcg)
-{
-	if (memcg && memcg->move_lock_task == current) {
-		unsigned long flags = memcg->move_lock_flags;
-
-		memcg->move_lock_task = NULL;
-		memcg->move_lock_flags = 0;
-
-		spin_unlock_irqrestore(&memcg->move_lock, flags);
-	}
-
-	rcu_read_unlock();
-}
-
-/**
- * folio_memcg_unlock - Release the binding between a folio and its memcg.
- * @folio: The folio.
- *
- * This releases the binding created by folio_memcg_lock().  This does
- * not change the accounting of this folio to its memcg, but it does
- * permit others to change it.
- */
-void folio_memcg_unlock(struct folio *folio)
-{
-	__folio_memcg_unlock(folio_memcg(folio));
-}
-
 static u64 mem_cgroup_move_charge_read(struct cgroup_subsys_state *css,
 				struct cftype *cft)
 {
@@ -1189,7 +1108,6 @@ void memcg1_memcg_init(struct mem_cgroup *memcg)
 {
 	INIT_LIST_HEAD(&memcg->oom_notify);
 	mutex_init(&memcg->thresholds_lock);
-	spin_lock_init(&memcg->move_lock);
 	INIT_LIST_HEAD(&memcg->event_list);
 	spin_lock_init(&memcg->event_list_lock);
 }
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index ec4ac6eb650b..39e902c1dd9f 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1189,7 +1189,6 @@ void lruvec_memcg_debug(struct lruvec *lruvec, struct folio *folio)
  * These functions are safe to use under any of the following conditions:
  * - folio locked
  * - folio_test_lru false
- * - folio_memcg_lock()
  * - folio frozen (refcount of 0)
  *
  * Return: The lruvec this folio is on with its lock held.
@@ -1211,7 +1210,6 @@ struct lruvec *folio_lruvec_lock(struct folio *folio)
  * These functions are safe to use under any of the following conditions:
  * - folio locked
  * - folio_test_lru false
- * - folio_memcg_lock()
  * - folio frozen (refcount of 0)
  *
  * Return: The lruvec this folio is on with its lock held and interrupts
@@ -1235,7 +1233,6 @@ struct lruvec *folio_lruvec_lock_irq(struct folio *folio)
  * These functions are safe to use under any of the following conditions:
  * - folio locked
  * - folio_test_lru false
- * - folio_memcg_lock()
  * - folio frozen (refcount of 0)
  *
  * Return: The lruvec this folio is on with its lock held and interrupts
@@ -2375,9 +2372,7 @@ static void commit_charge(struct folio *folio, struct mem_cgroup *memcg)
 	 *
 	 * - the page lock
 	 * - LRU isolation
-	 * - folio_memcg_lock()
 	 * - exclusive reference
-	 * - mem_cgroup_trylock_pages()
 	 */
 	folio->memcg_data = (unsigned long)memcg;
 }
diff --git a/mm/rmap.c b/mm/rmap.c
index 73d5998677d4..4d75433330f9 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -32,7 +32,6 @@
  *                   swap_lock (in swap_duplicate, swap_info_get)
  *                     mmlist_lock (in mmput, drain_mmlist and others)
  *                     mapping->private_lock (in block_dirty_folio)
- *                       folio_lock_memcg move_lock (in block_dirty_folio)
  *                         i_pages lock (widely used)
  *                           lruvec->lru_lock (in folio_lruvec_lock_irq)
  *                     inode->i_lock (in set_page_dirty's __mark_inode_dirty)