linux-imx

// SPDX-License-Identifier: GPL-2.0

/*

 * Manage cache of swap slots to be used for and returned from

 * swap.

 *

 * Copyright(c) 2016 Intel Corporation.

 *

 * Author: Tim Chen <tim.c.chen@linux.intel.com>

 *

 * We allocate the swap slots from the global pool and put

 * it into local per cpu caches.  This has the advantage

 * of no needing to acquire the swap_info lock every time

 * we need a new slot.

 *

 * There is also opportunity to simply return the slot

 * to local caches without needing to acquire swap_info

 * lock.  We do not reuse the returned slots directly but

 * move them back to the global pool in a batch.  This

 * allows the slots to coaellesce and reduce fragmentation.

 *

 * The swap entry allocated is marked with SWAP_HAS_CACHE

 * flag in map_count that prevents it from being allocated

 * again from the global pool.

 *

 * The swap slots cache is protected by a mutex instead of

 * a spin lock as when we search for slots with scan_swap_map,

 * we can possibly sleep.

 */

​

#include <linux/swap_slots.h>

#include <linux/cpu.h>

#include <linux/cpumask.h>

#include <linux/vmalloc.h>

#include <linux/mutex.h>

#include <linux/mm.h>

​

static DEFINE_PER_CPU(struct swap_slots_cache, swp_slots);

static bool swap_slot_cache_active;

bool    swap_slot_cache_enabled;

static bool swap_slot_cache_initialized;

static DEFINE_MUTEX(swap_slots_cache_mutex);

/* Serialize swap slots cache enable/disable operations */

static DEFINE_MUTEX(swap_slots_cache_enable_mutex);

​

static void __drain_swap_slots_cache(unsigned int type);

static void deactivate_swap_slots_cache(void);

static void reactivate_swap_slots_cache(void);

​

#define use_swap_slot_cache (swap_slot_cache_active && \

        swap_slot_cache_enabled && swap_slot_cache_initialized)

#define SLOTS_CACHE 0x1

#define SLOTS_CACHE_RET 0x2

​

static void deactivate_swap_slots_cache(void)

{

    mutex_lock(&swap_slots_cache_mutex);

    swap_slot_cache_active = false;

    __drain_swap_slots_cache(SLOTS_CACHE|SLOTS_CACHE_RET);

    mutex_unlock(&swap_slots_cache_mutex);

}

​

static void reactivate_swap_slots_cache(void)

{