1 /* SPDX-License-Identifier: GPL-2.0 */
3 * include/linux/backing-dev.h
5 * low-level device information and state which is propagated up through
9 #ifndef _LINUX_BACKING_DEV_H
10 #define _LINUX_BACKING_DEV_H
12 #include <linux/kernel.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>
20 static inline struct backing_dev_info *bdi_get(struct backing_dev_info *bdi)
22 kref_get(&bdi->refcnt);
26 struct backing_dev_info *bdi_get_by_id(u64 id);
27 void bdi_put(struct backing_dev_info *bdi);
30 int bdi_register(struct backing_dev_info *bdi, const char *fmt, ...);
32 int bdi_register_va(struct backing_dev_info *bdi, const char *fmt,
34 void bdi_set_owner(struct backing_dev_info *bdi, struct device *owner);
35 void bdi_unregister(struct backing_dev_info *bdi);
37 struct backing_dev_info *bdi_alloc(int node_id);
39 void wb_start_background_writeback(struct bdi_writeback *wb);
40 void wb_workfn(struct work_struct *work);
41 void wb_wakeup_delayed(struct bdi_writeback *wb);
43 void wb_wait_for_completion(struct wb_completion *done);
45 extern spinlock_t bdi_lock;
46 extern struct list_head bdi_list;
48 extern struct workqueue_struct *bdi_wq;
49 extern struct workqueue_struct *bdi_async_bio_wq;
51 static inline bool wb_has_dirty_io(struct bdi_writeback *wb)
53 return test_bit(WB_has_dirty_io, &wb->state);
56 static inline bool bdi_has_dirty_io(struct backing_dev_info *bdi)
59 * @bdi->tot_write_bandwidth is guaranteed to be > 0 if there are
60 * any dirty wbs. See wb_update_write_bandwidth().
62 return atomic_long_read(&bdi->tot_write_bandwidth);
65 static inline void wb_stat_mod(struct bdi_writeback *wb,
66 enum wb_stat_item item, s64 amount)
68 percpu_counter_add_batch(&wb->stat[item], amount, WB_STAT_BATCH);
71 static inline void inc_wb_stat(struct bdi_writeback *wb, enum wb_stat_item item)
73 wb_stat_mod(wb, item, 1);
76 static inline void dec_wb_stat(struct bdi_writeback *wb, enum wb_stat_item item)
78 wb_stat_mod(wb, item, -1);
81 static inline s64 wb_stat(struct bdi_writeback *wb, enum wb_stat_item item)
83 return percpu_counter_read_positive(&wb->stat[item]);
86 static inline s64 wb_stat_sum(struct bdi_writeback *wb, enum wb_stat_item item)
88 return percpu_counter_sum_positive(&wb->stat[item]);
91 extern void wb_writeout_inc(struct bdi_writeback *wb);
94 * maximal error of a stat counter.
96 static inline unsigned long wb_stat_error(void)
99 return nr_cpu_ids * WB_STAT_BATCH;
105 int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio);
106 int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio);
109 * Flags in backing_dev_info::capability
111 * BDI_CAP_WRITEBACK: Supports dirty page writeback, and dirty pages
112 * should contribute to accounting
113 * BDI_CAP_WRITEBACK_ACCT: Automatically account writeback pages
114 * BDI_CAP_STRICTLIMIT: Keep number of dirty pages below bdi threshold
116 #define BDI_CAP_WRITEBACK (1 << 0)
117 #define BDI_CAP_WRITEBACK_ACCT (1 << 1)
118 #define BDI_CAP_STRICTLIMIT (1 << 2)
120 extern struct backing_dev_info noop_backing_dev_info;
123 * writeback_in_progress - determine whether there is writeback in progress
124 * @wb: bdi_writeback of interest
126 * Determine whether there is writeback waiting to be handled against a
129 static inline bool writeback_in_progress(struct bdi_writeback *wb)
131 return test_bit(WB_writeback_running, &wb->state);
134 struct backing_dev_info *inode_to_bdi(struct inode *inode);
136 static inline bool mapping_can_writeback(struct address_space *mapping)
138 return inode_to_bdi(mapping->host)->capabilities & BDI_CAP_WRITEBACK;
141 static inline int bdi_sched_wait(void *word)
147 #ifdef CONFIG_CGROUP_WRITEBACK
149 struct bdi_writeback *wb_get_lookup(struct backing_dev_info *bdi,
150 struct cgroup_subsys_state *memcg_css);
151 struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
152 struct cgroup_subsys_state *memcg_css,
154 void wb_memcg_offline(struct mem_cgroup *memcg);
155 void wb_blkcg_offline(struct cgroup_subsys_state *css);
158 * inode_cgwb_enabled - test whether cgroup writeback is enabled on an inode
159 * @inode: inode of interest
161 * Cgroup writeback requires support from the filesystem. Also, both memcg and
162 * iocg have to be on the default hierarchy. Test whether all conditions are
165 * Note that the test result may change dynamically on the same inode
166 * depending on how memcg and iocg are configured.
168 static inline bool inode_cgwb_enabled(struct inode *inode)
170 struct backing_dev_info *bdi = inode_to_bdi(inode);
172 return cgroup_subsys_on_dfl(memory_cgrp_subsys) &&
173 cgroup_subsys_on_dfl(io_cgrp_subsys) &&
174 (bdi->capabilities & BDI_CAP_WRITEBACK) &&
175 (inode->i_sb->s_iflags & SB_I_CGROUPWB);
179 * wb_find_current - find wb for %current on a bdi
180 * @bdi: bdi of interest
182 * Find the wb of @bdi which matches both the memcg and blkcg of %current.
183 * Must be called under rcu_read_lock() which protects the returend wb.
186 static inline struct bdi_writeback *wb_find_current(struct backing_dev_info *bdi)
188 struct cgroup_subsys_state *memcg_css;
189 struct bdi_writeback *wb;
191 memcg_css = task_css(current, memory_cgrp_id);
192 if (!memcg_css->parent)
195 wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
198 * %current's blkcg equals the effective blkcg of its memcg. No
199 * need to use the relatively expensive cgroup_get_e_css().
201 if (likely(wb && wb->blkcg_css == task_css(current, io_cgrp_id)))
207 * wb_get_create_current - get or create wb for %current on a bdi
208 * @bdi: bdi of interest
209 * @gfp: allocation mask
211 * Equivalent to wb_get_create() on %current's memcg. This function is
212 * called from a relatively hot path and optimizes the common cases using
215 static inline struct bdi_writeback *
216 wb_get_create_current(struct backing_dev_info *bdi, gfp_t gfp)
218 struct bdi_writeback *wb;
221 wb = wb_find_current(bdi);
222 if (wb && unlikely(!wb_tryget(wb)))
227 struct cgroup_subsys_state *memcg_css;
229 memcg_css = task_get_css(current, memory_cgrp_id);
230 wb = wb_get_create(bdi, memcg_css, gfp);
237 * inode_to_wb_is_valid - test whether an inode has a wb associated
238 * @inode: inode of interest
240 * Returns %true if @inode has a wb associated. May be called without any
243 static inline bool inode_to_wb_is_valid(struct inode *inode)
249 * inode_to_wb - determine the wb of an inode
250 * @inode: inode of interest
252 * Returns the wb @inode is currently associated with. The caller must be
253 * holding either @inode->i_lock, the i_pages lock, or the
254 * associated wb's list_lock.
256 static inline struct bdi_writeback *inode_to_wb(const struct inode *inode)
258 #ifdef CONFIG_LOCKDEP
259 WARN_ON_ONCE(debug_locks &&
260 (!lockdep_is_held(&inode->i_lock) &&
261 !lockdep_is_held(&inode->i_mapping->i_pages.xa_lock) &&
262 !lockdep_is_held(&inode->i_wb->list_lock)));
267 static inline struct bdi_writeback *inode_to_wb_wbc(
269 struct writeback_control *wbc)
272 * If wbc does not have inode attached, it means cgroup writeback was
273 * disabled when wbc started. Just use the default wb in that case.
275 return wbc->wb ? wbc->wb : &inode_to_bdi(inode)->wb;
279 * unlocked_inode_to_wb_begin - begin unlocked inode wb access transaction
280 * @inode: target inode
281 * @cookie: output param, to be passed to the end function
283 * The caller wants to access the wb associated with @inode but isn't
284 * holding inode->i_lock, the i_pages lock or wb->list_lock. This
285 * function determines the wb associated with @inode and ensures that the
286 * association doesn't change until the transaction is finished with
287 * unlocked_inode_to_wb_end().
289 * The caller must call unlocked_inode_to_wb_end() with *@cookie afterwards and
290 * can't sleep during the transaction. IRQs may or may not be disabled on
293 static inline struct bdi_writeback *
294 unlocked_inode_to_wb_begin(struct inode *inode, struct wb_lock_cookie *cookie)
299 * Paired with store_release in inode_switch_wbs_work_fn() and
300 * ensures that we see the new wb if we see cleared I_WB_SWITCH.
302 cookie->locked = smp_load_acquire(&inode->i_state) & I_WB_SWITCH;
304 if (unlikely(cookie->locked))
305 xa_lock_irqsave(&inode->i_mapping->i_pages, cookie->flags);
308 * Protected by either !I_WB_SWITCH + rcu_read_lock() or the i_pages
309 * lock. inode_to_wb() will bark. Deref directly.
315 * unlocked_inode_to_wb_end - end inode wb access transaction
316 * @inode: target inode
317 * @cookie: @cookie from unlocked_inode_to_wb_begin()
319 static inline void unlocked_inode_to_wb_end(struct inode *inode,
320 struct wb_lock_cookie *cookie)
322 if (unlikely(cookie->locked))
323 xa_unlock_irqrestore(&inode->i_mapping->i_pages, cookie->flags);
328 #else /* CONFIG_CGROUP_WRITEBACK */
330 static inline bool inode_cgwb_enabled(struct inode *inode)
335 static inline struct bdi_writeback *wb_find_current(struct backing_dev_info *bdi)
340 static inline struct bdi_writeback *
341 wb_get_create_current(struct backing_dev_info *bdi, gfp_t gfp)
346 static inline bool inode_to_wb_is_valid(struct inode *inode)
351 static inline struct bdi_writeback *inode_to_wb(struct inode *inode)
353 return &inode_to_bdi(inode)->wb;
356 static inline struct bdi_writeback *inode_to_wb_wbc(
358 struct writeback_control *wbc)
360 return inode_to_wb(inode);
364 static inline struct bdi_writeback *
365 unlocked_inode_to_wb_begin(struct inode *inode, struct wb_lock_cookie *cookie)
367 return inode_to_wb(inode);
370 static inline void unlocked_inode_to_wb_end(struct inode *inode,
371 struct wb_lock_cookie *cookie)
375 static inline void wb_memcg_offline(struct mem_cgroup *memcg)
379 static inline void wb_blkcg_offline(struct cgroup_subsys_state *css)
383 #endif /* CONFIG_CGROUP_WRITEBACK */
385 const char *bdi_dev_name(struct backing_dev_info *bdi);
387 #endif /* _LINUX_BACKING_DEV_H */