1/* SPDX-License-Identifier: GPL-2.0 */ 2/* 3 * include/linux/backing-dev.h 4 * 5 * low-level device information and state which is propagated up through 6 * to high-level code. 7 */ 8 9#ifndef _LINUX_BACKING_DEV_H 10#define _LINUX_BACKING_DEV_H 11 12#include <linux/kernel.h> 13#include <linux/fs.h> 14#include <linux/sched.h> 15#include <linux/device.h> 16#include <linux/writeback.h> 17#include <linux/backing-dev-defs.h> 18#include <linux/slab.h> 19 20static inline struct backing_dev_info *bdi_get(struct backing_dev_info *bdi) 21{ 22 kref_get(&bdi->refcnt); 23 return bdi; 24} 25 26struct backing_dev_info *bdi_get_by_id(u64 id); 27void bdi_put(struct backing_dev_info *bdi); 28 29__printf(2, 3) 30int bdi_register(struct backing_dev_info *bdi, const char *fmt, ...); 31__printf(2, 0) 32int bdi_register_va(struct backing_dev_info *bdi, const char *fmt, 33 va_list args); 34void bdi_set_owner(struct backing_dev_info *bdi, struct device *owner); 35void bdi_unregister(struct backing_dev_info *bdi); 36 37struct backing_dev_info *bdi_alloc(int node_id); 38 39void wb_start_background_writeback(struct bdi_writeback *wb); 40void wb_workfn(struct work_struct *work); 41 42void wb_wait_for_completion(struct wb_completion *done); 43 44extern spinlock_t bdi_lock; 45extern struct list_head bdi_list; 46 47extern struct workqueue_struct *bdi_wq; 48 49static inline bool wb_has_dirty_io(struct bdi_writeback *wb) 50{ 51 return test_bit(WB_has_dirty_io, &wb->state); 52} 53 54static inline bool bdi_has_dirty_io(struct backing_dev_info *bdi) 55{ 56 /* 57 * @bdi->tot_write_bandwidth is guaranteed to be > 0 if there are 58 * any dirty wbs. See wb_update_write_bandwidth(). 59 */ 60 return atomic_long_read(&bdi->tot_write_bandwidth); 61} 62 63static inline void wb_stat_mod(struct bdi_writeback *wb, 64 enum wb_stat_item item, s64 amount) 65{ 66 percpu_counter_add_batch(&wb->stat[item], amount, WB_STAT_BATCH); 67} 68 69static inline void inc_wb_stat(struct bdi_writeback *wb, enum wb_stat_item item) 70{ 71 wb_stat_mod(wb, item, 1); 72} 73 74static inline void dec_wb_stat(struct bdi_writeback *wb, enum wb_stat_item item) 75{ 76 wb_stat_mod(wb, item, -1); 77} 78 79static inline s64 wb_stat(struct bdi_writeback *wb, enum wb_stat_item item) 80{ 81 return percpu_counter_read_positive(&wb->stat[item]); 82} 83 84static inline s64 wb_stat_sum(struct bdi_writeback *wb, enum wb_stat_item item) 85{ 86 return percpu_counter_sum_positive(&wb->stat[item]); 87} 88 89extern void wb_writeout_inc(struct bdi_writeback *wb); 90 91/* 92 * maximal error of a stat counter. 93 */ 94static inline unsigned long wb_stat_error(void) 95{ 96#ifdef CONFIG_SMP 97 return nr_cpu_ids * WB_STAT_BATCH; 98#else 99 return 1; 100#endif 101} 102 103/* BDI ratio is expressed as part per 1000000 for finer granularity. */ 104#define BDI_RATIO_SCALE 10000 105 106u64 bdi_get_min_bytes(struct backing_dev_info *bdi); 107u64 bdi_get_max_bytes(struct backing_dev_info *bdi); 108int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio); 109int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio); 110int bdi_set_min_ratio_no_scale(struct backing_dev_info *bdi, unsigned int min_ratio); 111int bdi_set_max_ratio_no_scale(struct backing_dev_info *bdi, unsigned int max_ratio); 112int bdi_set_min_bytes(struct backing_dev_info *bdi, u64 min_bytes); 113int bdi_set_max_bytes(struct backing_dev_info *bdi, u64 max_bytes); 114int bdi_set_strict_limit(struct backing_dev_info *bdi, unsigned int strict_limit); 115 116/* 117 * Flags in backing_dev_info::capability 118 * 119 * BDI_CAP_WRITEBACK: Supports dirty page writeback, and dirty pages 120 * should contribute to accounting 121 * BDI_CAP_WRITEBACK_ACCT: Automatically account writeback pages 122 * BDI_CAP_STRICTLIMIT: Keep number of dirty pages below bdi threshold 123 */ 124#define BDI_CAP_WRITEBACK (1 << 0) 125#define BDI_CAP_WRITEBACK_ACCT (1 << 1) 126#define BDI_CAP_STRICTLIMIT (1 << 2) 127 128extern struct backing_dev_info noop_backing_dev_info; 129 130int bdi_init(struct backing_dev_info *bdi); 131 132/** 133 * writeback_in_progress - determine whether there is writeback in progress 134 * @wb: bdi_writeback of interest 135 * 136 * Determine whether there is writeback waiting to be handled against a 137 * bdi_writeback. 138 */ 139static inline bool writeback_in_progress(struct bdi_writeback *wb) 140{ 141 return test_bit(WB_writeback_running, &wb->state); 142} 143 144struct backing_dev_info *inode_to_bdi(struct inode *inode); 145 146static inline bool mapping_can_writeback(struct address_space *mapping) 147{ 148 return inode_to_bdi(mapping->host)->capabilities & BDI_CAP_WRITEBACK; 149} 150 151#ifdef CONFIG_CGROUP_WRITEBACK 152 153struct bdi_writeback *wb_get_lookup(struct backing_dev_info *bdi, 154 struct cgroup_subsys_state *memcg_css); 155struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi, 156 struct cgroup_subsys_state *memcg_css, 157 gfp_t gfp); 158void wb_memcg_offline(struct mem_cgroup *memcg); 159void wb_blkcg_offline(struct cgroup_subsys_state *css); 160 161/** 162 * inode_cgwb_enabled - test whether cgroup writeback is enabled on an inode 163 * @inode: inode of interest 164 * 165 * Cgroup writeback requires support from the filesystem. Also, both memcg and 166 * iocg have to be on the default hierarchy. Test whether all conditions are 167 * met. 168 * 169 * Note that the test result may change dynamically on the same inode 170 * depending on how memcg and iocg are configured. 171 */ 172static inline bool inode_cgwb_enabled(struct inode *inode) 173{ 174 struct backing_dev_info *bdi = inode_to_bdi(inode); 175 176 return cgroup_subsys_on_dfl(memory_cgrp_subsys) && 177 cgroup_subsys_on_dfl(io_cgrp_subsys) && 178 (bdi->capabilities & BDI_CAP_WRITEBACK) && 179 (inode->i_sb->s_iflags & SB_I_CGROUPWB); 180} 181 182/** 183 * wb_find_current - find wb for %current on a bdi 184 * @bdi: bdi of interest 185 * 186 * Find the wb of @bdi which matches both the memcg and blkcg of %current. 187 * Must be called under rcu_read_lock() which protects the returend wb. 188 * NULL if not found. 189 */ 190static inline struct bdi_writeback *wb_find_current(struct backing_dev_info *bdi) 191{ 192 struct cgroup_subsys_state *memcg_css; 193 struct bdi_writeback *wb; 194 195 memcg_css = task_css(current, memory_cgrp_id); 196 if (!memcg_css->parent) 197 return &bdi->wb; 198 199 wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id); 200 201 /* 202 * %current's blkcg equals the effective blkcg of its memcg. No 203 * need to use the relatively expensive cgroup_get_e_css(). 204 */ 205 if (likely(wb && wb->blkcg_css == task_css(current, io_cgrp_id))) 206 return wb; 207 return NULL; 208} 209 210/** 211 * wb_get_create_current - get or create wb for %current on a bdi 212 * @bdi: bdi of interest 213 * @gfp: allocation mask 214 * 215 * Equivalent to wb_get_create() on %current's memcg. This function is 216 * called from a relatively hot path and optimizes the common cases using 217 * wb_find_current(). 218 */ 219static inline struct bdi_writeback * 220wb_get_create_current(struct backing_dev_info *bdi, gfp_t gfp) 221{ 222 struct bdi_writeback *wb; 223 224 rcu_read_lock(); 225 wb = wb_find_current(bdi); 226 if (wb && unlikely(!wb_tryget(wb))) 227 wb = NULL; 228 rcu_read_unlock(); 229 230 if (unlikely(!wb)) { 231 struct cgroup_subsys_state *memcg_css; 232 233 memcg_css = task_get_css(current, memory_cgrp_id); 234 wb = wb_get_create(bdi, memcg_css, gfp); 235 css_put(memcg_css); 236 } 237 return wb; 238} 239 240/** 241 * inode_to_wb - determine the wb of an inode 242 * @inode: inode of interest 243 * 244 * Returns the wb @inode is currently associated with. The caller must be 245 * holding either @inode->i_lock, the i_pages lock, or the 246 * associated wb's list_lock. 247 */ 248static inline struct bdi_writeback *inode_to_wb(const struct inode *inode) 249{ 250#ifdef CONFIG_LOCKDEP 251 WARN_ON_ONCE(debug_locks && 252 (!lockdep_is_held(&inode->i_lock) && 253 !lockdep_is_held(&inode->i_mapping->i_pages.xa_lock) && 254 !lockdep_is_held(&inode->i_wb->list_lock))); 255#endif 256 return inode->i_wb; 257} 258 259static inline struct bdi_writeback *inode_to_wb_wbc( 260 struct inode *inode, 261 struct writeback_control *wbc) 262{ 263 /* 264 * If wbc does not have inode attached, it means cgroup writeback was 265 * disabled when wbc started. Just use the default wb in that case. 266 */ 267 return wbc->wb ? wbc->wb : &inode_to_bdi(inode)->wb; 268} 269 270/** 271 * unlocked_inode_to_wb_begin - begin unlocked inode wb access transaction 272 * @inode: target inode 273 * @cookie: output param, to be passed to the end function 274 * 275 * The caller wants to access the wb associated with @inode but isn't 276 * holding inode->i_lock, the i_pages lock or wb->list_lock. This 277 * function determines the wb associated with @inode and ensures that the 278 * association doesn't change until the transaction is finished with 279 * unlocked_inode_to_wb_end(). 280 * 281 * The caller must call unlocked_inode_to_wb_end() with *@cookie afterwards and 282 * can't sleep during the transaction. IRQs may or may not be disabled on 283 * return. 284 */ 285static inline struct bdi_writeback * 286unlocked_inode_to_wb_begin(struct inode *inode, struct wb_lock_cookie *cookie) 287{ 288 rcu_read_lock(); 289 290 /* 291 * Paired with store_release in inode_switch_wbs_work_fn() and 292 * ensures that we see the new wb if we see cleared I_WB_SWITCH. 293 */ 294 cookie->locked = smp_load_acquire(&inode->i_state) & I_WB_SWITCH; 295 296 if (unlikely(cookie->locked)) 297 xa_lock_irqsave(&inode->i_mapping->i_pages, cookie->flags); 298 299 /* 300 * Protected by either !I_WB_SWITCH + rcu_read_lock() or the i_pages 301 * lock. inode_to_wb() will bark. Deref directly. 302 */ 303 return inode->i_wb; 304} 305 306/** 307 * unlocked_inode_to_wb_end - end inode wb access transaction 308 * @inode: target inode 309 * @cookie: @cookie from unlocked_inode_to_wb_begin() 310 */ 311static inline void unlocked_inode_to_wb_end(struct inode *inode, 312 struct wb_lock_cookie *cookie) 313{ 314 if (unlikely(cookie->locked)) 315 xa_unlock_irqrestore(&inode->i_mapping->i_pages, cookie->flags); 316 317 rcu_read_unlock(); 318} 319 320#else /* CONFIG_CGROUP_WRITEBACK */ 321 322static inline bool inode_cgwb_enabled(struct inode *inode) 323{ 324 return false; 325} 326 327static inline struct bdi_writeback *wb_find_current(struct backing_dev_info *bdi) 328{ 329 return &bdi->wb; 330} 331 332static inline struct bdi_writeback * 333wb_get_create_current(struct backing_dev_info *bdi, gfp_t gfp) 334{ 335 return &bdi->wb; 336} 337 338static inline struct bdi_writeback *inode_to_wb(struct inode *inode) 339{ 340 return &inode_to_bdi(inode)->wb; 341} 342 343static inline struct bdi_writeback *inode_to_wb_wbc( 344 struct inode *inode, 345 struct writeback_control *wbc) 346{ 347 return inode_to_wb(inode); 348} 349 350 351static inline struct bdi_writeback * 352unlocked_inode_to_wb_begin(struct inode *inode, struct wb_lock_cookie *cookie) 353{ 354 return inode_to_wb(inode); 355} 356 357static inline void unlocked_inode_to_wb_end(struct inode *inode, 358 struct wb_lock_cookie *cookie) 359{ 360} 361 362static inline void wb_memcg_offline(struct mem_cgroup *memcg) 363{ 364} 365 366static inline void wb_blkcg_offline(struct cgroup_subsys_state *css) 367{ 368} 369 370#endif /* CONFIG_CGROUP_WRITEBACK */ 371 372const char *bdi_dev_name(struct backing_dev_info *bdi); 373 374#endif /* _LINUX_BACKING_DEV_H */ 375