1 /* SPDX-License-Identifier: GPL-2.0 */ 2 /* 3 * include/linux/writeback.h 4 */ 5 #ifndef WRITEBACK_H 6 #define WRITEBACK_H 7 8 #include <linux/sched.h> 9 #include <linux/workqueue.h> 10 #include <linux/fs.h> 11 #include <linux/flex_proportions.h> 12 #include <linux/backing-dev-defs.h> 13 #include <linux/blk_types.h> 14 15 struct bio; 16 17 DECLARE_PER_CPU(int, dirty_throttle_leaks); 18 19 /* 20 * The global dirty threshold is normally equal to the global dirty limit, 21 * except when the system suddenly allocates a lot of anonymous memory and 22 * knocks down the global dirty threshold quickly, in which case the global 23 * dirty limit will follow down slowly to prevent livelocking all dirtier tasks. 24 */ 25 #define DIRTY_SCOPE 8 26 27 struct backing_dev_info; 28 29 /* 30 * fs/fs-writeback.c 31 */ 32 enum writeback_sync_modes { 33 WB_SYNC_NONE, /* Don't wait on anything */ 34 WB_SYNC_ALL, /* Wait on every mapping */ 35 }; 36 37 /* 38 * A control structure which tells the writeback code what to do. These are 39 * always on the stack, and hence need no locking. They are always initialised 40 * in a manner such that unspecified fields are set to zero. 41 */ 42 struct writeback_control { 43 long nr_to_write; /* Write this many pages, and decrement 44 this for each page written */ 45 long pages_skipped; /* Pages which were not written */ 46 47 /* 48 * For a_ops->writepages(): if start or end are non-zero then this is 49 * a hint that the filesystem need only write out the pages inside that 50 * byterange. The byte at `end' is included in the writeout request. 51 */ 52 loff_t range_start; 53 loff_t range_end; 54 55 enum writeback_sync_modes sync_mode; 56 57 unsigned for_kupdate:1; /* A kupdate writeback */ 58 unsigned for_background:1; /* A background writeback */ 59 unsigned tagged_writepages:1; /* tag-and-write to avoid livelock */ 60 unsigned for_reclaim:1; /* Invoked from the page allocator */ 61 unsigned range_cyclic:1; /* range_start is cyclic */ 62 unsigned for_sync:1; /* sync(2) WB_SYNC_ALL writeback */ 63 unsigned unpinned_netfs_wb:1; /* Cleared I_PINNING_NETFS_WB */ 64 65 /* 66 * When writeback IOs are bounced through async layers, only the 67 * initial synchronous phase should be accounted towards inode 68 * cgroup ownership arbitration to avoid confusion. Later stages 69 * can set the following flag to disable the accounting. 70 */ 71 unsigned no_cgroup_owner:1; 72 73 /* To enable batching of swap writes to non-block-device backends, 74 * "plug" can be set point to a 'struct swap_iocb *'. When all swap 75 * writes have been submitted, if with swap_iocb is not NULL, 76 * swap_write_unplug() should be called. 77 */ 78 struct swap_iocb **swap_plug; 79 80 #ifdef CONFIG_CGROUP_WRITEBACK 81 struct bdi_writeback *wb; /* wb this writeback is issued under */ 82 struct inode *inode; /* inode being written out */ 83 84 /* foreign inode detection, see wbc_detach_inode() */ 85 int wb_id; /* current wb id */ 86 int wb_lcand_id; /* last foreign candidate wb id */ 87 int wb_tcand_id; /* this foreign candidate wb id */ 88 size_t wb_bytes; /* bytes written by current wb */ 89 size_t wb_lcand_bytes; /* bytes written by last candidate */ 90 size_t wb_tcand_bytes; /* bytes written by this candidate */ 91 #endif 92 }; 93 94 static inline blk_opf_t wbc_to_write_flags(struct writeback_control *wbc) 95 { 96 blk_opf_t flags = 0; 97 98 if (wbc->sync_mode == WB_SYNC_ALL) 99 flags |= REQ_SYNC; 100 else if (wbc->for_kupdate || wbc->for_background) 101 flags |= REQ_BACKGROUND; 102 103 return flags; 104 } 105 106 #ifdef CONFIG_CGROUP_WRITEBACK 107 #define wbc_blkcg_css(wbc) \ 108 ((wbc)->wb ? (wbc)->wb->blkcg_css : blkcg_root_css) 109 #else 110 #define wbc_blkcg_css(wbc) (blkcg_root_css) 111 #endif /* CONFIG_CGROUP_WRITEBACK */ 112 113 /* 114 * A wb_domain represents a domain that wb's (bdi_writeback's) belong to 115 * and are measured against each other in. There always is one global 116 * domain, global_wb_domain, that every wb in the system is a member of. 117 * This allows measuring the relative bandwidth of each wb to distribute 118 * dirtyable memory accordingly. 119 */ 120 struct wb_domain { 121 spinlock_t lock; 122 123 /* 124 * Scale the writeback cache size proportional to the relative 125 * writeout speed. 126 * 127 * We do this by keeping a floating proportion between BDIs, based 128 * on page writeback completions [end_page_writeback()]. Those 129 * devices that write out pages fastest will get the larger share, 130 * while the slower will get a smaller share. 131 * 132 * We use page writeout completions because we are interested in 133 * getting rid of dirty pages. Having them written out is the 134 * primary goal. 135 * 136 * We introduce a concept of time, a period over which we measure 137 * these events, because demand can/will vary over time. The length 138 * of this period itself is measured in page writeback completions. 139 */ 140 struct fprop_global completions; 141 struct timer_list period_timer; /* timer for aging of completions */ 142 unsigned long period_time; 143 144 /* 145 * The dirtyable memory and dirty threshold could be suddenly 146 * knocked down by a large amount (eg. on the startup of KVM in a 147 * swapless system). This may throw the system into deep dirty 148 * exceeded state and throttle heavy/light dirtiers alike. To 149 * retain good responsiveness, maintain global_dirty_limit for 150 * tracking slowly down to the knocked down dirty threshold. 151 * 152 * Both fields are protected by ->lock. 153 */ 154 unsigned long dirty_limit_tstamp; 155 unsigned long dirty_limit; 156 }; 157 158 /** 159 * wb_domain_size_changed - memory available to a wb_domain has changed 160 * @dom: wb_domain of interest 161 * 162 * This function should be called when the amount of memory available to 163 * @dom has changed. It resets @dom's dirty limit parameters to prevent 164 * the past values which don't match the current configuration from skewing 165 * dirty throttling. Without this, when memory size of a wb_domain is 166 * greatly reduced, the dirty throttling logic may allow too many pages to 167 * be dirtied leading to consecutive unnecessary OOMs and may get stuck in 168 * that situation. 169 */ 170 static inline void wb_domain_size_changed(struct wb_domain *dom) 171 { 172 spin_lock(&dom->lock); 173 dom->dirty_limit_tstamp = jiffies; 174 dom->dirty_limit = 0; 175 spin_unlock(&dom->lock); 176 } 177 178 /* 179 * fs/fs-writeback.c 180 */ 181 struct bdi_writeback; 182 void writeback_inodes_sb(struct super_block *, enum wb_reason reason); 183 void writeback_inodes_sb_nr(struct super_block *, unsigned long nr, 184 enum wb_reason reason); 185 void try_to_writeback_inodes_sb(struct super_block *sb, enum wb_reason reason); 186 void sync_inodes_sb(struct super_block *); 187 void wakeup_flusher_threads(enum wb_reason reason); 188 void wakeup_flusher_threads_bdi(struct backing_dev_info *bdi, 189 enum wb_reason reason); 190 void inode_wait_for_writeback(struct inode *inode); 191 void inode_io_list_del(struct inode *inode); 192 193 /* writeback.h requires fs.h; it, too, is not included from here. */ 194 static inline void wait_on_inode(struct inode *inode) 195 { 196 wait_on_bit(&inode->i_state, __I_NEW, TASK_UNINTERRUPTIBLE); 197 } 198 199 #ifdef CONFIG_CGROUP_WRITEBACK 200 201 #include <linux/cgroup.h> 202 #include <linux/bio.h> 203 204 void __inode_attach_wb(struct inode *inode, struct folio *folio); 205 void wbc_attach_and_unlock_inode(struct writeback_control *wbc, 206 struct inode *inode) 207 __releases(&inode->i_lock); 208 void wbc_detach_inode(struct writeback_control *wbc); 209 void wbc_account_cgroup_owner(struct writeback_control *wbc, struct page *page, 210 size_t bytes); 211 int cgroup_writeback_by_id(u64 bdi_id, int memcg_id, 212 enum wb_reason reason, struct wb_completion *done); 213 void cgroup_writeback_umount(void); 214 bool cleanup_offline_cgwb(struct bdi_writeback *wb); 215 216 /** 217 * inode_attach_wb - associate an inode with its wb 218 * @inode: inode of interest 219 * @folio: folio being dirtied (may be NULL) 220 * 221 * If @inode doesn't have its wb, associate it with the wb matching the 222 * memcg of @folio or, if @folio is NULL, %current. May be called w/ or w/o 223 * @inode->i_lock. 224 */ 225 static inline void inode_attach_wb(struct inode *inode, struct folio *folio) 226 { 227 if (!inode->i_wb) 228 __inode_attach_wb(inode, folio); 229 } 230 231 /** 232 * inode_detach_wb - disassociate an inode from its wb 233 * @inode: inode of interest 234 * 235 * @inode is being freed. Detach from its wb. 236 */ 237 static inline void inode_detach_wb(struct inode *inode) 238 { 239 if (inode->i_wb) { 240 WARN_ON_ONCE(!(inode->i_state & I_CLEAR)); 241 wb_put(inode->i_wb); 242 inode->i_wb = NULL; 243 } 244 } 245 246 /** 247 * wbc_attach_fdatawrite_inode - associate wbc and inode for fdatawrite 248 * @wbc: writeback_control of interest 249 * @inode: target inode 250 * 251 * This function is to be used by __filemap_fdatawrite_range(), which is an 252 * alternative entry point into writeback code, and first ensures @inode is 253 * associated with a bdi_writeback and attaches it to @wbc. 254 */ 255 static inline void wbc_attach_fdatawrite_inode(struct writeback_control *wbc, 256 struct inode *inode) 257 { 258 spin_lock(&inode->i_lock); 259 inode_attach_wb(inode, NULL); 260 wbc_attach_and_unlock_inode(wbc, inode); 261 } 262 263 /** 264 * wbc_init_bio - writeback specific initializtion of bio 265 * @wbc: writeback_control for the writeback in progress 266 * @bio: bio to be initialized 267 * 268 * @bio is a part of the writeback in progress controlled by @wbc. Perform 269 * writeback specific initialization. This is used to apply the cgroup 270 * writeback context. Must be called after the bio has been associated with 271 * a device. 272 */ 273 static inline void wbc_init_bio(struct writeback_control *wbc, struct bio *bio) 274 { 275 /* 276 * pageout() path doesn't attach @wbc to the inode being written 277 * out. This is intentional as we don't want the function to block 278 * behind a slow cgroup. Ultimately, we want pageout() to kick off 279 * regular writeback instead of writing things out itself. 280 */ 281 if (wbc->wb) 282 bio_associate_blkg_from_css(bio, wbc->wb->blkcg_css); 283 } 284 285 #else /* CONFIG_CGROUP_WRITEBACK */ 286 287 static inline void inode_attach_wb(struct inode *inode, struct folio *folio) 288 { 289 } 290 291 static inline void inode_detach_wb(struct inode *inode) 292 { 293 } 294 295 static inline void wbc_attach_and_unlock_inode(struct writeback_control *wbc, 296 struct inode *inode) 297 __releases(&inode->i_lock) 298 { 299 spin_unlock(&inode->i_lock); 300 } 301 302 static inline void wbc_attach_fdatawrite_inode(struct writeback_control *wbc, 303 struct inode *inode) 304 { 305 } 306 307 static inline void wbc_detach_inode(struct writeback_control *wbc) 308 { 309 } 310 311 static inline void wbc_init_bio(struct writeback_control *wbc, struct bio *bio) 312 { 313 } 314 315 static inline void wbc_account_cgroup_owner(struct writeback_control *wbc, 316 struct page *page, size_t bytes) 317 { 318 } 319 320 static inline void cgroup_writeback_umount(void) 321 { 322 } 323 324 #endif /* CONFIG_CGROUP_WRITEBACK */ 325 326 /* 327 * mm/page-writeback.c 328 */ 329 void laptop_io_completion(struct backing_dev_info *info); 330 void laptop_sync_completion(void); 331 void laptop_mode_timer_fn(struct timer_list *t); 332 bool node_dirty_ok(struct pglist_data *pgdat); 333 int wb_domain_init(struct wb_domain *dom, gfp_t gfp); 334 #ifdef CONFIG_CGROUP_WRITEBACK 335 void wb_domain_exit(struct wb_domain *dom); 336 #endif 337 338 extern struct wb_domain global_wb_domain; 339 340 /* These are exported to sysctl. */ 341 extern unsigned int dirty_writeback_interval; 342 extern unsigned int dirty_expire_interval; 343 extern unsigned int dirtytime_expire_interval; 344 extern int laptop_mode; 345 346 int dirtytime_interval_handler(struct ctl_table *table, int write, 347 void *buffer, size_t *lenp, loff_t *ppos); 348 349 void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty); 350 unsigned long wb_calc_thresh(struct bdi_writeback *wb, unsigned long thresh); 351 352 void wb_update_bandwidth(struct bdi_writeback *wb); 353 354 /* Invoke balance dirty pages in async mode. */ 355 #define BDP_ASYNC 0x0001 356 357 void balance_dirty_pages_ratelimited(struct address_space *mapping); 358 int balance_dirty_pages_ratelimited_flags(struct address_space *mapping, 359 unsigned int flags); 360 361 bool wb_over_bg_thresh(struct bdi_writeback *wb); 362 363 typedef int (*writepage_t)(struct folio *folio, struct writeback_control *wbc, 364 void *data); 365 366 void tag_pages_for_writeback(struct address_space *mapping, 367 pgoff_t start, pgoff_t end); 368 int write_cache_pages(struct address_space *mapping, 369 struct writeback_control *wbc, writepage_t writepage, 370 void *data); 371 int do_writepages(struct address_space *mapping, struct writeback_control *wbc); 372 void writeback_set_ratelimit(void); 373 void tag_pages_for_writeback(struct address_space *mapping, 374 pgoff_t start, pgoff_t end); 375 376 bool filemap_dirty_folio(struct address_space *mapping, struct folio *folio); 377 bool folio_redirty_for_writepage(struct writeback_control *, struct folio *); 378 bool redirty_page_for_writepage(struct writeback_control *, struct page *); 379 380 void sb_mark_inode_writeback(struct inode *inode); 381 void sb_clear_inode_writeback(struct inode *inode); 382 383 #endif /* WRITEBACK_H */ 384