linux/mm/swap_cgroup.c

// SPDX-License-Identifier: GPL-2.0
#include <linux/swap_cgroup.h>
#include <linux/vmalloc.h>
#include <linux/mm.h>

#include <linux/swapops.h> /* depends on mm.h include */

static DEFINE_MUTEX(swap_cgroup_mutex);
struct swap_cgroup_ctrl { … };

static struct swap_cgroup_ctrl swap_cgroup_ctrl[MAX_SWAPFILES];

struct swap_cgroup { … };
#define SC_PER_PAGE …

/*
 * SwapCgroup implements "lookup" and "exchange" operations.
 * In typical usage, this swap_cgroup is accessed via memcg's charge/uncharge
 * against SwapCache. At swap_free(), this is accessed directly from swap.
 *
 * This means,
 *  - we have no race in "exchange" when we're accessed via SwapCache because
 *    SwapCache(and its swp_entry) is under lock.
 *  - When called via swap_free(), there is no user of this entry and no race.
 * Then, we don't need lock around "exchange".
 *
 * TODO: we can push these buffers out to HIGHMEM.
 */

/*
 * allocate buffer for swap_cgroup.
 */
static int swap_cgroup_prepare(int type)
{ … }

static struct swap_cgroup *__lookup_swap_cgroup(struct swap_cgroup_ctrl *ctrl,
						pgoff_t offset)
{ … }

static struct swap_cgroup *lookup_swap_cgroup(swp_entry_t ent,
					struct swap_cgroup_ctrl **ctrlp)
{ … }

/**
 * swap_cgroup_cmpxchg - cmpxchg mem_cgroup's id for this swp_entry.
 * @ent: swap entry to be cmpxchged
 * @old: old id
 * @new: new id
 *
 * Returns old id at success, 0 at failure.
 * (There is no mem_cgroup using 0 as its id)
 */
unsigned short swap_cgroup_cmpxchg(swp_entry_t ent,
					unsigned short old, unsigned short new)
{ … }

/**
 * swap_cgroup_record - record mem_cgroup for a set of swap entries
 * @ent: the first swap entry to be recorded into
 * @id: mem_cgroup to be recorded
 * @nr_ents: number of swap entries to be recorded
 *
 * Returns old value at success, 0 at failure.
 * (Of course, old value can be 0.)
 */
unsigned short swap_cgroup_record(swp_entry_t ent, unsigned short id,
				  unsigned int nr_ents)
{ … }

/**
 * lookup_swap_cgroup_id - lookup mem_cgroup id tied to swap entry
 * @ent: swap entry to be looked up.
 *
 * Returns ID of mem_cgroup at success. 0 at failure. (0 is invalid ID)
 */
unsigned short lookup_swap_cgroup_id(swp_entry_t ent)
{ … }

int swap_cgroup_swapon(int type, unsigned long max_pages)
{ … }

void swap_cgroup_swapoff(int type)
{ … }