// SPDX-License-Identifier: GPL-2.0-only
/*
 *  linux/mm/swap.c
 *
 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
 */

/*
 * This file contains the default values for the operation of the
 * Linux VM subsystem. Fine-tuning documentation can be found in
 * Documentation/admin-guide/sysctl/vm.rst.
 * Started 18.12.91
 * Swap aging added 23.2.95, Stephen Tweedie.
 * Buffermem limits added 12.3.98, Rik van Riel.
 */

/* Extracted unchanged from Linux v6.0, mm/swap.c:902-924.
 * Complete function definition; surrounding kernel context is required.
 * Source: https://github.com/torvalds/linux/blob/v6.0/mm/swap.c#L902
 * License text: GPL-2.0.txt (in this directory).
 */
void lru_cache_disable(void)
{
	atomic_inc(&lru_disable_count);
	/*
	 * Readers of lru_disable_count are protected by either disabling
	 * preemption or rcu_read_lock:
	 *
	 * preempt_disable, local_irq_disable  [bh_lru_lock()]
	 * rcu_read_lock		       [rt_spin_lock CONFIG_PREEMPT_RT]
	 * preempt_disable		       [local_lock !CONFIG_PREEMPT_RT]
	 *
	 * Since v5.1 kernel, synchronize_rcu() is guaranteed to wait on
	 * preempt_disable() regions of code. So any CPU which sees
	 * lru_disable_count = 0 will have exited the critical
	 * section when synchronize_rcu() returns.
	 */
	synchronize_rcu_expedited();
#ifdef CONFIG_SMP
	__lru_add_drain_all(true);
#else
	lru_add_and_bh_lrus_drain();
#endif
}