diff options
Diffstat (limited to 'mm/memcontrol.c')
| -rw-r--r-- | mm/memcontrol.c | 36 |
1 files changed, 11 insertions, 25 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index e064ac0d850a..06caac775abb 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2118,11 +2118,10 @@ void mem_cgroup_print_oom_group(struct mem_cgroup *memcg) * This function protects unlocked LRU pages from being moved to * another cgroup. * - * It ensures lifetime of the returned memcg. Caller is responsible - * for the lifetime of the page; __unlock_page_memcg() is available - * when @page might get freed inside the locked section. + * It ensures lifetime of the locked memcg. Caller is responsible + * for the lifetime of the page. */ -struct mem_cgroup *lock_page_memcg(struct page *page) +void lock_page_memcg(struct page *page) { struct page *head = compound_head(page); /* rmap on tail pages */ struct mem_cgroup *memcg; @@ -2132,21 +2131,15 @@ struct mem_cgroup *lock_page_memcg(struct page *page) * 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. - * - * The RCU lock also protects the memcg from being freed when - * the page state that is going to change is the only thing - * preventing the page itself from being freed. E.g. writeback - * doesn't hold a page reference and relies on PG_writeback to - * keep off truncation, migration and so forth. */ rcu_read_lock(); if (mem_cgroup_disabled()) - return NULL; + return; again: memcg = page_memcg(head); if (unlikely(!memcg)) - return NULL; + return; #ifdef CONFIG_PROVE_LOCKING local_irq_save(flags); @@ -2155,7 +2148,7 @@ again: #endif if (atomic_read(&memcg->moving_account) <= 0) - return memcg; + return; spin_lock_irqsave(&memcg->move_lock, flags); if (memcg != page_memcg(head)) { @@ -2164,24 +2157,17 @@ again: } /* - * When charge migration first begins, we can have locked and - * unlocked page stat updates happening concurrently. Track - * the task who has the lock for unlock_page_memcg(). + * 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 unlock_page_memcg(). */ memcg->move_lock_task = current; memcg->move_lock_flags = flags; - - return memcg; } EXPORT_SYMBOL(lock_page_memcg); -/** - * __unlock_page_memcg - unlock and unpin a memcg - * @memcg: the memcg - * - * Unlock and unpin a memcg returned by lock_page_memcg(). - */ -void __unlock_page_memcg(struct mem_cgroup *memcg) +static void __unlock_page_memcg(struct mem_cgroup *memcg) { if (memcg && memcg->move_lock_task == current) { unsigned long flags = memcg->move_lock_flags; |