linux/include/linux/writeback.h

/* SPDX-License-Identifier: GPL-2.0 */
/*
 * include/linux/writeback.h
 */
#ifndef WRITEBACK_H
#define WRITEBACK_H

#include <linux/sched.h>
#include <linux/workqueue.h>
#include <linux/fs.h>
#include <linux/flex_proportions.h>
#include <linux/backing-dev-defs.h>
#include <linux/blk_types.h>
#include <linux/pagevec.h>

struct bio;

DECLARE_PER_CPU(int, dirty_throttle_leaks);

/*
 * The global dirty threshold is normally equal to the global dirty limit,
 * except when the system suddenly allocates a lot of anonymous memory and
 * knocks down the global dirty threshold quickly, in which case the global
 * dirty limit will follow down slowly to prevent livelocking all dirtier tasks.
 */
#define DIRTY_SCOPE …

struct backing_dev_info;

/*
 * fs/fs-writeback.c
 */
enum writeback_sync_modes { … };

/*
 * A control structure which tells the writeback code what to do.  These are
 * always on the stack, and hence need no locking.  They are always initialised
 * in a manner such that unspecified fields are set to zero.
 */
struct writeback_control { … };

static inline blk_opf_t wbc_to_write_flags(struct writeback_control *wbc)
{ … }

#ifdef CONFIG_CGROUP_WRITEBACK
#define wbc_blkcg_css(wbc) …
#else
#define wbc_blkcg_css …
#endif /* CONFIG_CGROUP_WRITEBACK */

/*
 * A wb_domain represents a domain that wb's (bdi_writeback's) belong to
 * and are measured against each other in.  There always is one global
 * domain, global_wb_domain, that every wb in the system is a member of.
 * This allows measuring the relative bandwidth of each wb to distribute
 * dirtyable memory accordingly.
 */
struct wb_domain { … };

/**
 * wb_domain_size_changed - memory available to a wb_domain has changed
 * @dom: wb_domain of interest
 *
 * This function should be called when the amount of memory available to
 * @dom has changed.  It resets @dom's dirty limit parameters to prevent
 * the past values which don't match the current configuration from skewing
 * dirty throttling.  Without this, when memory size of a wb_domain is
 * greatly reduced, the dirty throttling logic may allow too many pages to
 * be dirtied leading to consecutive unnecessary OOMs and may get stuck in
 * that situation.
 */
static inline void wb_domain_size_changed(struct wb_domain *dom)
{ … }

/*
 * fs/fs-writeback.c
 */	
struct bdi_writeback;
void writeback_inodes_sb(struct super_block *, enum wb_reason reason);
void writeback_inodes_sb_nr(struct super_block *, unsigned long nr,
							enum wb_reason reason);
void try_to_writeback_inodes_sb(struct super_block *sb, enum wb_reason reason);
void sync_inodes_sb(struct super_block *);
void wakeup_flusher_threads(enum wb_reason reason);
void wakeup_flusher_threads_bdi(struct backing_dev_info *bdi,
				enum wb_reason reason);
void inode_wait_for_writeback(struct inode *inode);
void inode_io_list_del(struct inode *inode);

/* writeback.h requires fs.h; it, too, is not included from here. */
static inline void wait_on_inode(struct inode *inode)
{ … }

#ifdef CONFIG_CGROUP_WRITEBACK

#include <linux/cgroup.h>
#include <linux/bio.h>

void __inode_attach_wb(struct inode *inode, struct folio *folio);
void wbc_attach_and_unlock_inode(struct writeback_control *wbc,
				 struct inode *inode)
	__releases(…);
void wbc_detach_inode(struct writeback_control *wbc);
void wbc_account_cgroup_owner(struct writeback_control *wbc, struct page *page,
			      size_t bytes);
int cgroup_writeback_by_id(u64 bdi_id, int memcg_id,
			   enum wb_reason reason, struct wb_completion *done);
void cgroup_writeback_umount(struct super_block *sb);
bool cleanup_offline_cgwb(struct bdi_writeback *wb);

/**
 * inode_attach_wb - associate an inode with its wb
 * @inode: inode of interest
 * @folio: folio being dirtied (may be NULL)
 *
 * If @inode doesn't have its wb, associate it with the wb matching the
 * memcg of @folio or, if @folio is NULL, %current.  May be called w/ or w/o
 * @inode->i_lock.
 */
static inline void inode_attach_wb(struct inode *inode, struct folio *folio)
{ … }

/**
 * inode_detach_wb - disassociate an inode from its wb
 * @inode: inode of interest
 *
 * @inode is being freed.  Detach from its wb.
 */
static inline void inode_detach_wb(struct inode *inode)
{ … }

/**
 * wbc_attach_fdatawrite_inode - associate wbc and inode for fdatawrite
 * @wbc: writeback_control of interest
 * @inode: target inode
 *
 * This function is to be used by __filemap_fdatawrite_range(), which is an
 * alternative entry point into writeback code, and first ensures @inode is
 * associated with a bdi_writeback and attaches it to @wbc.
 */
static inline void wbc_attach_fdatawrite_inode(struct writeback_control *wbc,
					       struct inode *inode)
{ … }

/**
 * wbc_init_bio - writeback specific initializtion of bio
 * @wbc: writeback_control for the writeback in progress
 * @bio: bio to be initialized
 *
 * @bio is a part of the writeback in progress controlled by @wbc.  Perform
 * writeback specific initialization.  This is used to apply the cgroup
 * writeback context.  Must be called after the bio has been associated with
 * a device.
 */
static inline void wbc_init_bio(struct writeback_control *wbc, struct bio *bio)
{ … }

#else	/* CONFIG_CGROUP_WRITEBACK */

static inline void inode_attach_wb(struct inode *inode, struct folio *folio)
{
}

static inline void inode_detach_wb(struct inode *inode)
{
}

static inline void wbc_attach_and_unlock_inode(struct writeback_control *wbc,
					       struct inode *inode)
	__releases(&inode->i_lock)
{
	spin_unlock(&inode->i_lock);
}

static inline void wbc_attach_fdatawrite_inode(struct writeback_control *wbc,
					       struct inode *inode)
{
}

static inline void wbc_detach_inode(struct writeback_control *wbc)
{
}

static inline void wbc_init_bio(struct writeback_control *wbc, struct bio *bio)
{
}

static inline void wbc_account_cgroup_owner(struct writeback_control *wbc,
					    struct page *page, size_t bytes)
{
}

static inline void cgroup_writeback_umount(struct super_block *sb)
{
}

#endif	/* CONFIG_CGROUP_WRITEBACK */

/*
 * mm/page-writeback.c
 */
void laptop_io_completion(struct backing_dev_info *info);
void laptop_sync_completion(void);
void laptop_mode_timer_fn(struct timer_list *t);
bool node_dirty_ok(struct pglist_data *pgdat);
int wb_domain_init(struct wb_domain *dom, gfp_t gfp);
#ifdef CONFIG_CGROUP_WRITEBACK
void wb_domain_exit(struct wb_domain *dom);
#endif

extern struct wb_domain global_wb_domain;

/* These are exported to sysctl. */
extern unsigned int dirty_writeback_interval;
extern unsigned int dirty_expire_interval;
extern unsigned int dirtytime_expire_interval;
extern int laptop_mode;

int dirtytime_interval_handler(const struct ctl_table *table, int write,
		void *buffer, size_t *lenp, loff_t *ppos);

void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty);
unsigned long wb_calc_thresh(struct bdi_writeback *wb, unsigned long thresh);
unsigned long cgwb_calc_thresh(struct bdi_writeback *wb);

void wb_update_bandwidth(struct bdi_writeback *wb);

/* Invoke balance dirty pages in async mode. */
#define BDP_ASYNC …

void balance_dirty_pages_ratelimited(struct address_space *mapping);
int balance_dirty_pages_ratelimited_flags(struct address_space *mapping,
		unsigned int flags);

bool wb_over_bg_thresh(struct bdi_writeback *wb);

struct folio *writeback_iter(struct address_space *mapping,
		struct writeback_control *wbc, struct folio *folio, int *error);

writepage_t;

int write_cache_pages(struct address_space *mapping,
		      struct writeback_control *wbc, writepage_t writepage,
		      void *data);
int do_writepages(struct address_space *mapping, struct writeback_control *wbc);
void writeback_set_ratelimit(void);
void tag_pages_for_writeback(struct address_space *mapping,
			     pgoff_t start, pgoff_t end);

bool filemap_dirty_folio(struct address_space *mapping, struct folio *folio);
bool folio_redirty_for_writepage(struct writeback_control *, struct folio *);
bool redirty_page_for_writepage(struct writeback_control *, struct page *);

void sb_mark_inode_writeback(struct inode *inode);
void sb_clear_inode_writeback(struct inode *inode);

#endif		/* WRITEBACK_H */