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/* 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 8 struct backing_dev_info; /* * fs/fs-writeback.c */ enum writeback_sync_modes { WB_SYNC_NONE, /* Don't wait on anything */ WB_SYNC_ALL, /* Wait on every mapping */ }; /* * 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 { /* public fields that can be set and/or consumed by the caller: */ long nr_to_write; /* Write this many pages, and decrement this for each page written */ long pages_skipped; /* Pages which were not written */ /* * For a_ops->writepages(): if start or end are non-zero then this is * a hint that the filesystem need only write out the pages inside that * byterange. The byte at `end' is included in the writeout request. */ loff_t range_start; loff_t range_end; enum writeback_sync_modes sync_mode; unsigned for_kupdate:1; /* A kupdate writeback */ unsigned for_background:1; /* A background writeback */ unsigned tagged_writepages:1; /* tag-and-write to avoid livelock */ unsigned for_reclaim:1; /* Invoked from the page allocator */ unsigned range_cyclic:1; /* range_start is cyclic */ unsigned for_sync:1; /* sync(2) WB_SYNC_ALL writeback */ unsigned unpinned_netfs_wb:1; /* Cleared I_PINNING_NETFS_WB */ /* * When writeback IOs are bounced through async layers, only the * initial synchronous phase should be accounted towards inode * cgroup ownership arbitration to avoid confusion. Later stages * can set the following flag to disable the accounting. */ unsigned no_cgroup_owner:1; /* To enable batching of swap writes to non-block-device backends, * "plug" can be set point to a 'struct swap_iocb *'. When all swap * writes have been submitted, if with swap_iocb is not NULL, * swap_write_unplug() should be called. */ struct swap_iocb **swap_plug; /* Target list for splitting a large folio */ struct list_head *list; /* internal fields used by the ->writepages implementation: */ struct folio_batch fbatch; pgoff_t index; int saved_err; #ifdef CONFIG_CGROUP_WRITEBACK struct bdi_writeback *wb; /* wb this writeback is issued under */ struct inode *inode; /* inode being written out */ /* foreign inode detection, see wbc_detach_inode() */ int wb_id; /* current wb id */ int wb_lcand_id; /* last foreign candidate wb id */ int wb_tcand_id; /* this foreign candidate wb id */ size_t wb_bytes; /* bytes written by current wb */ size_t wb_lcand_bytes; /* bytes written by last candidate */ size_t wb_tcand_bytes; /* bytes written by this candidate */ #endif }; static inline blk_opf_t wbc_to_write_flags(struct writeback_control *wbc) { blk_opf_t flags = 0; if (wbc->sync_mode == WB_SYNC_ALL) flags |= REQ_SYNC; else if (wbc->for_kupdate || wbc->for_background) flags |= REQ_BACKGROUND; return flags; } #ifdef CONFIG_CGROUP_WRITEBACK #define wbc_blkcg_css(wbc) \ ((wbc)->wb ? (wbc)->wb->blkcg_css : blkcg_root_css) #else #define wbc_blkcg_css(wbc) (blkcg_root_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 { spinlock_t lock; /* * Scale the writeback cache size proportional to the relative * writeout speed. * * We do this by keeping a floating proportion between BDIs, based * on page writeback completions [end_page_writeback()]. Those * devices that write out pages fastest will get the larger share, * while the slower will get a smaller share. * * We use page writeout completions because we are interested in * getting rid of dirty pages. Having them written out is the * primary goal. * * We introduce a concept of time, a period over which we measure * these events, because demand can/will vary over time. The length * of this period itself is measured in page writeback completions. */ struct fprop_global completions; struct timer_list period_timer; /* timer for aging of completions */ unsigned long period_time; /* * The dirtyable memory and dirty threshold could be suddenly * knocked down by a large amount (eg. on the startup of KVM in a * swapless system). This may throw the system into deep dirty * exceeded state and throttle heavy/light dirtiers alike. To * retain good responsiveness, maintain global_dirty_limit for * tracking slowly down to the knocked down dirty threshold. * * Both fields are protected by ->lock. */ unsigned long dirty_limit_tstamp; unsigned long dirty_limit; }; /** * 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) { spin_lock(&dom->lock); dom->dirty_limit_tstamp = jiffies; dom->dirty_limit = 0; spin_unlock(&dom->lock); } /* * 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) { wait_var_event(inode_state_wait_address(inode, __I_NEW), !(READ_ONCE(inode->i_state) & I_NEW)); } #ifdef CONFIG_CGROUP_WRITEBACK #include <linux/cgroup.h> #include <linux/bio.h> void __inode_attach_wb(struct inode *inode, struct folio *folio); void wbc_detach_inode(struct writeback_control *wbc); void wbc_account_cgroup_owner(struct writeback_control *wbc, struct folio *folio, 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) { if (!inode->i_wb) __inode_attach_wb(inode, 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) { if (inode->i_wb) { WARN_ON_ONCE(!(inode->i_state & I_CLEAR)); wb_put(inode->i_wb); inode->i_wb = NULL; } } 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) { /* * pageout() path doesn't attach @wbc to the inode being written * out. This is intentional as we don't want the function to block * behind a slow cgroup. Ultimately, we want pageout() to kick off * regular writeback instead of writing things out itself. */ if (wbc->wb) bio_associate_blkg_from_css(bio, wbc->wb->blkcg_css); } #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_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 folio *folio, size_t bytes) { } static inline void cgroup_writeback_umount(struct super_block *sb) { } #endif /* CONFIG_CGROUP_WRITEBACK */ /* * mm/page-writeback.c */ /* consolidated parameters for balance_dirty_pages() and its subroutines */ struct dirty_throttle_control { #ifdef CONFIG_CGROUP_WRITEBACK struct wb_domain *dom; struct dirty_throttle_control *gdtc; /* only set in memcg dtc's */ #endif struct bdi_writeback *wb; struct fprop_local_percpu *wb_completions; unsigned long avail; /* dirtyable */ unsigned long dirty; /* file_dirty + write + nfs */ unsigned long thresh; /* dirty threshold */ unsigned long bg_thresh; /* dirty background threshold */ unsigned long limit; /* hard dirty limit */ unsigned long wb_dirty; /* per-wb counterparts */ unsigned long wb_thresh; unsigned long wb_bg_thresh; unsigned long pos_ratio; bool freerun; bool dirty_exceeded; }; 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 0x0001 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); typedef int (*writepage_t)(struct folio *folio, struct writeback_control *wbc, void *data); 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 */