live
     Е€Щв„ZiЇШАд ?ч     Е/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_SWAP_H
#define _LINUX_SWAP_H

#include <linux/spinlock.h>
#include <linux/linkage.h>
#include <linux/mmzone.h>
#include <linux/list.h>
#include <linux/memcontrol.h>
#include <linux/sched.h>
#include <linux/node.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/atomic.h>
#include <linux/page-flags.h>
#include <uapi/linux/mempolicy.h>
#include <asm/page.h>

struct notifier_block;

struct bio;

struct pagevec;

#define SWAP_FLAG_PREFER	0x8000	/* set if swap priority specified */
#define SWAP_FLAG_PRIO_MASK	0x7fff
#define SWAP_FLAG_PRIO_SHIFT	0
#define SWAP_FLAG_DISCARD	0x10000 /* enable discard for swap */
#define SWAP_FLAG_DISCARD_ONCE	0x20000 /* discard swap area at swapon-time */
#define SWAP_FLAG_DISCARD_PAGES 0x40000 /* discard page-clusters after use */

#define SWAP_FLAGS_VALID	(SWAP_FLAG_PRIO_MASK | SWAP_FLAG_PREFER | \
				 SWAP_FLAG_DISCARD | SWAP_FLAG_DISCARD_ONCE | \
				 SWAP_FLAG_DISCARD_PAGES)
#define SWAP_BATCH 64

static inline int current_is_kswapd(void)
{
	return current->flags & PF_KSWAPD;
}

/*
 * MAX_SWAPFILES defines the maximum number of swaptypes: things which can
 * be swapped to.  The swap type and the offset into that swap type are
 * encoded into pte's and into pgoff_t's in the swapcache.  Using five bits
 * for the type means that the maximum number of swapcache pages is 27 bits
 * on 32-bit-pgoff_t architectures.  And that assumes that the architecture packs
 * the type/offset into the pte as 5/27 as well.
 */
#define MAX_SWAPFILES_SHIFT	5

/*
 * Use some of the swap files numbers for other purposes. This
 * is a convenient way to hook into the VM to trigger special
 * actions on faults.
 */

/*
 * PTE markers are used to persist information onto PTEs that otherwise
 * should be a none pte.  As its name "PTE" hints, it should only be
 * applied to the leaves of pgtables.
*/
#define SWP_PTE_MARKER_NUM 1
#define SWP_PTE_MARKER     (MAX_SWAPFILES + SWP_HWPOISON_NUM + \
			    SWP_MIGRATION_NUM + SWP_DEVICE_NUM)

/*
 * Unaddressable device memory support. See include/linux/hmm.h and
 * Documentation/mm/hmm.rst. Short description is we need struct pages for
 * device memory that is unaddressable (inaccessible) by CPU, so that we can
 * migrate part of a process memory to device memory.
 *
 * When a page is migrated from CPU to device, we set the CPU page table entry
 * to a special SWP_DEVICE_{READ|WRITE} entry.
 *
 * When a page is mapped by the device for exclusive access we set the CPU page
 * table entries to special SWP_DEVICE_EXCLUSIVE_* entries.
 */
#ifdef CONFIG_DEVICE_PRIVATE
#define SWP_DEVICE_NUM 4
#define SWP_DEVICE_WRITE (MAX_SWAPFILES+SWP_HWPOISON_NUM+SWP_MIGRATION_NUM)
#define SWP_DEVICE_READ (MAX_SWAPFILES+SWP_HWPOISON_NUM+SWP_MIGRATION_NUM+1)
#define SWP_DEVICE_EXCLUSIVE_WRITE (MAX_SWAPFILES+SWP_HWPOISON_NUM+SWP_MIGRATION_NUM+2)
#define SWP_DEVICE_EXCLUSIVE_READ (MAX_SWAPFILES+SWP_HWPOISON_NUM+SWP_MIGRATION_NUM+3)
#else
#define SWP_DEVICE_NUM 0
#endif

/*
 * Page migration support.
 *
 * SWP_MIGRATION_READ_EXCLUSIVE is only applicable to anonymous pages and
 * indicates that the referenced (part of) an anonymous page is exclusive to
 * a single process. For SWP_MIGRATION_WRITE, that information is implicit:
 * (part of) an anonymous page that are mapped writable are exclusive to a
 * single process.
 */
#ifdef CONFIG_MIGRATION
#define SWP_MIGRATION_NUM 3
#define SWP_MIGRATION_READ (MAX_SWAPFILES + SWP_HWPOISON_NUM)
#define SWP_MIGRATION_READ_EXCLUSIVE (MAX_SWAPFILES + SWP_HWPOISON_NUM + 1)
#define SWP_MIGRATION_WRITE (MAX_SWAPFILES + SWP_HWPOISON_NUM + 2)
#else
#define SWP_MIGRATION_NUM 0
#endif

/*
 * Handling of hardware poisoned pages with memory corruption.
 */
#ifdef CONFIG_MEMORY_FAILURE
#define SWP_HWPOISON_NUM 1
#define SWP_HWPOISON		MAX_SWAPFILES
#else
#define SWP_HWPOISON_NUM 0
#endif

#define MAX_SWAPFILES \
	((1 << MAX_SWAPFILES_SHIFT) - SWP_DEVICE_NUM - \
	SWP_MIGRATION_NUM - SWP_HWPOISON_NUM - \
	SWP_PTE_MARKER_NUM)

/*
 * Magic header for a swap area. The first