path: root/include/linux/pagemap.h

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _LINUX_PAGEMAP_H
#define _LINUX_PAGEMAP_H

/*
 * Copyright 1995 Linus Torvalds
 */
#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/list.h>
#include <linux/highmem.h>
#include <linux/compiler.h>
#include <linux/uaccess.h>
#include <linux/gfp.h>
#include <linux/bitops.h>
#include <linux/hardirq.h> /* for in_interrupt() */
#include <linux/hugetlb_inline.h>

struct folio_batch;

static inline bool mapping_empty(struct address_space *mapping)
{
	return xa_empty(&mapping->i_pages);
}

/*
 * mapping_shrinkable - test if page cache state allows inode reclaim
 * @mapping: the page cache mapping
 *
 * This checks the mapping's cache state for the pupose of inode
 * reclaim and LRU management.
 *
 * The caller is expected to hold the i_lock, but is not required to
 * hold the i_pages lock, which usually protects cache state. That's
 * because the i_lock and the list_lru lock that protect the inode and
 * its LRU state don't nest inside the irq-safe i_pages lock.
 *
 * Cache deletions are performed under the i_lock, which ensures that
 * when an inode goes empty, it will reliably get queued on the LRU.
 *
 * Cache additions do not acquire the i_lock and may race with this
 * check, in which case we'll report the inode as shrinkable when it
 * has cache pages. This is okay: the shrinker also checks the
 * refcount and the referenced bit, which will be elevated or set in
 * the process of adding new cache pages to an inode.
 */
static inline bool mapping_shrinkable(struct address_space *mapping)
{
	void *head;

	/*
	 * On highmem systems, there could be lowmem pressure from the
	 * inodes before there is highmem pressure from the page
	 * cache. Make inodes shrinkable regardless of cache state.
	 */
	if (IS_ENABLED(CONFIG_HIGHMEM))
		return true;

	/* Cache completely empty? Shrink away. */
	head = rcu_access_pointer(mapping->i_pages.xa_head);
	if (!head)
		return true;

	/*
	 * The xarray stores single offset-0 entries directly in the
	 * head pointer, which allows non-resident page cache entries
	 * to escape the shadow shrinker's list of xarray nodes. The
	 * inode shrinker needs to pick them up under memory pressure.
	 */
	if (!xa_is_node(head) && xa_is_value(head))
		return true;

	return false;
}

/*
 * Bits in mapping->flags.
 */
enum mapping_flags {
	AS_EIO		= 0,	/* IO error on async write */
	AS_ENOSPC	= 1,	/* ENOSPC on async write */
	AS_MM_ALL_LOCKS	= 2,	/* under mm_take_all_locks() */
	AS_UNEVICTABLE	= 3,	/* e.g., ramdisk, SHM_LOCK */
	AS_EXITING	= 4, 	/* final truncate in progress */
	/* writeback related tags are not used */
	AS_NO_WRITEBACK_TAGS = 5,
	AS_LARGE_FOLIO_SUPPORT = 6,
};

/**
 * mapping_set_error - record a writeback error in the address_space
 * @mapping: the mapping in which an error should be set
 * @error: the error to set in the mapping
 *
 * When writeback fails in some way, we must record that error so that
 * userspace can be informed when fsync and the like are called.  We endeavor
 * to report errors on any file that was open at the time of the error.  Some
 * internal callers also need to know when writeback errors have occurred.
 *
 * When a writeback error occurs, most filesystems will want to call
 * mapping_set_error to record the error in the mapping so that it can be
 * reported when the application calls fsync(2).
 */
static inline void mapping_set_error(struct address_space *mapping, int error)
{
	if (likely(!error))
		return;

	/* Record in wb_err for checkers using errseq_t based tracking */
	__filemap_set_wb_err(mapping, error);

	/* Record it in superblock */
	if (mapping->host)
		errseq_set(&mapping->host->i_sb->s_wb_err, error);

	/* Record it in flags for now, for legacy callers */
	if (error == -ENOSPC)
		set_bit(AS_ENOSPC, &mapping->flags);
	else
		set_bit(AS_EIO, &mapping->flags);
}

static inline void mapping_set_unevictable(struct address_space *mapping)
{
	set_bit(AS_UNEVICTABLE, &mapping->flags);
}

static inline void mapping_clear_unevictable(struct address_space *mapping)