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(kref: &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);
41void wb_wakeup_delayed(struct bdi_writeback *wb);
42
43void wb_wait_for_completion(struct wb_completion *done);
44
45extern spinlock_t bdi_lock;
46extern struct list_head bdi_list;
47
48extern struct workqueue_struct *bdi_wq;
49
50static inline bool wb_has_dirty_io(struct bdi_writeback *wb)
51{
52 return test_bit(WB_has_dirty_io, &wb->state);
53}
54
55static inline bool bdi_has_dirty_io(struct backing_dev_info *bdi)
56{
57 /*
58 * @bdi->tot_write_bandwidth is guaranteed to be > 0 if there are
59 * any dirty wbs. See wb_update_write_bandwidth().
60 */
61 return atomic_long_read(v: &bdi->tot_write_bandwidth);
62}
63
64static inline void wb_stat_mod(struct bdi_writeback *wb,
65 enum wb_stat_item item, s64 amount)
66{
67 percpu_counter_add_batch(fbc: &wb->stat[item], amount, WB_STAT_BATCH);
68}
69
70static inline void inc_wb_stat(struct bdi_writeback *wb, enum wb_stat_item item)
71{
72 wb_stat_mod(wb, item, amount: 1);
73}
74
75static inline void dec_wb_stat(struct bdi_writeback *wb, enum wb_stat_item item)
76{
77 wb_stat_mod(wb, item, amount: -1);
78}
79
80static inline s64 wb_stat(struct bdi_writeback *wb, enum wb_stat_item item)
81{
82 return percpu_counter_read_positive(fbc: &wb->stat[item]);
83}
84
85static inline s64 wb_stat_sum(struct bdi_writeback *wb, enum wb_stat_item item)
86{
87 return percpu_counter_sum_positive(fbc: &wb->stat[item]);
88}
89
90extern void wb_writeout_inc(struct bdi_writeback *wb);
91
92/*
93 * maximal error of a stat counter.
94 */
95static inline unsigned long wb_stat_error(void)
96{
97#ifdef CONFIG_SMP
98 return nr_cpu_ids * WB_STAT_BATCH;
99#else
100 return 1;
101#endif
102}
103
104/* BDI ratio is expressed as part per 1000000 for finer granularity. */
105#define BDI_RATIO_SCALE 10000
106
107u64 bdi_get_min_bytes(struct backing_dev_info *bdi);
108u64 bdi_get_max_bytes(struct backing_dev_info *bdi);
109int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio);
110int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio);
111int bdi_set_min_ratio_no_scale(struct backing_dev_info *bdi, unsigned int min_ratio);
112int bdi_set_max_ratio_no_scale(struct backing_dev_info *bdi, unsigned int max_ratio);
113int bdi_set_min_bytes(struct backing_dev_info *bdi, u64 min_bytes);
114int bdi_set_max_bytes(struct backing_dev_info *bdi, u64 max_bytes);
115int bdi_set_strict_limit(struct backing_dev_info *bdi, unsigned int strict_limit);
116
117/*
118 * Flags in backing_dev_info::capability
119 *
120 * BDI_CAP_WRITEBACK: Supports dirty page writeback, and dirty pages
121 * should contribute to accounting
122 * BDI_CAP_WRITEBACK_ACCT: Automatically account writeback pages
123 * BDI_CAP_STRICTLIMIT: Keep number of dirty pages below bdi threshold
124 */
125#define BDI_CAP_WRITEBACK (1 << 0)
126#define BDI_CAP_WRITEBACK_ACCT (1 << 1)
127#define BDI_CAP_STRICTLIMIT (1 << 2)
128
129extern struct backing_dev_info noop_backing_dev_info;
130
131int bdi_init(struct backing_dev_info *bdi);
132
133/**
134 * writeback_in_progress - determine whether there is writeback in progress
135 * @wb: bdi_writeback of interest
136 *
137 * Determine whether there is writeback waiting to be handled against a
138 * bdi_writeback.
139 */
140static inline bool writeback_in_progress(struct bdi_writeback *wb)
141{
142 return test_bit(WB_writeback_running, &wb->state);
143}
144
145struct backing_dev_info *inode_to_bdi(struct inode *inode);
146
147static inline bool mapping_can_writeback(struct address_space *mapping)
148{
149 return inode_to_bdi(inode: mapping->host)->capabilities & BDI_CAP_WRITEBACK;
150}
151
152#ifdef CONFIG_CGROUP_WRITEBACK
153
154struct bdi_writeback *wb_get_lookup(struct backing_dev_info *bdi,
155 struct cgroup_subsys_state *memcg_css);
156struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
157 struct cgroup_subsys_state *memcg_css,
158 gfp_t gfp);
159void wb_memcg_offline(struct mem_cgroup *memcg);
160void wb_blkcg_offline(struct cgroup_subsys_state *css);
161
162/**
163 * inode_cgwb_enabled - test whether cgroup writeback is enabled on an inode
164 * @inode: inode of interest
165 *
166 * Cgroup writeback requires support from the filesystem. Also, both memcg and
167 * iocg have to be on the default hierarchy. Test whether all conditions are
168 * met.
169 *
170 * Note that the test result may change dynamically on the same inode
171 * depending on how memcg and iocg are configured.
172 */
173static inline bool inode_cgwb_enabled(struct inode *inode)
174{
175 struct backing_dev_info *bdi = inode_to_bdi(inode);
176
177 return cgroup_subsys_on_dfl(memory_cgrp_subsys) &&
178 cgroup_subsys_on_dfl(io_cgrp_subsys) &&
179 (bdi->capabilities & BDI_CAP_WRITEBACK) &&
180 (inode->i_sb->s_iflags & SB_I_CGROUPWB);
181}
182
183/**
184 * wb_find_current - find wb for %current on a bdi
185 * @bdi: bdi of interest
186 *
187 * Find the wb of @bdi which matches both the memcg and blkcg of %current.
188 * Must be called under rcu_read_lock() which protects the returend wb.
189 * NULL if not found.
190 */
191static inline struct bdi_writeback *wb_find_current(struct backing_dev_info *bdi)
192{
193 struct cgroup_subsys_state *memcg_css;
194 struct bdi_writeback *wb;
195
196 memcg_css = task_css(current, subsys_id: memory_cgrp_id);
197 if (!memcg_css->parent)
198 return &bdi->wb;
199
200 wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
201
202 /*
203 * %current's blkcg equals the effective blkcg of its memcg. No
204 * need to use the relatively expensive cgroup_get_e_css().
205 */
206 if (likely(wb && wb->blkcg_css == task_css(current, io_cgrp_id)))
207 return wb;
208 return NULL;
209}
210
211/**
212 * wb_get_create_current - get or create wb for %current on a bdi
213 * @bdi: bdi of interest
214 * @gfp: allocation mask
215 *
216 * Equivalent to wb_get_create() on %current's memcg. This function is
217 * called from a relatively hot path and optimizes the common cases using
218 * wb_find_current().
219 */
220static inline struct bdi_writeback *
221wb_get_create_current(struct backing_dev_info *bdi, gfp_t gfp)
222{
223 struct bdi_writeback *wb;
224
225 rcu_read_lock();
226 wb = wb_find_current(bdi);
227 if (wb && unlikely(!wb_tryget(wb)))
228 wb = NULL;
229 rcu_read_unlock();
230
231 if (unlikely(!wb)) {
232 struct cgroup_subsys_state *memcg_css;
233
234 memcg_css = task_get_css(current, subsys_id: memory_cgrp_id);
235 wb = wb_get_create(bdi, memcg_css, gfp);
236 css_put(css: memcg_css);
237 }
238 return wb;
239}
240
241/**
242 * inode_to_wb - determine the wb of an inode
243 * @inode: inode of interest
244 *
245 * Returns the wb @inode is currently associated with. The caller must be
246 * holding either @inode->i_lock, the i_pages lock, or the
247 * associated wb's list_lock.
248 */
249static inline struct bdi_writeback *inode_to_wb(const struct inode *inode)
250{
251#ifdef CONFIG_LOCKDEP
252 WARN_ON_ONCE(debug_locks &&
253 (!lockdep_is_held(&inode->i_lock) &&
254 !lockdep_is_held(&inode->i_mapping->i_pages.xa_lock) &&
255 !lockdep_is_held(&inode->i_wb->list_lock)));
256#endif
257 return inode->i_wb;
258}
259
260static inline struct bdi_writeback *inode_to_wb_wbc(
261 struct inode *inode,
262 struct writeback_control *wbc)
263{
264 /*
265 * If wbc does not have inode attached, it means cgroup writeback was
266 * disabled when wbc started. Just use the default wb in that case.
267 */
268 return wbc->wb ? wbc->wb : &inode_to_bdi(inode)->wb;
269}
270
271/**
272 * unlocked_inode_to_wb_begin - begin unlocked inode wb access transaction
273 * @inode: target inode
274 * @cookie: output param, to be passed to the end function
275 *
276 * The caller wants to access the wb associated with @inode but isn't
277 * holding inode->i_lock, the i_pages lock or wb->list_lock. This
278 * function determines the wb associated with @inode and ensures that the
279 * association doesn't change until the transaction is finished with
280 * unlocked_inode_to_wb_end().
281 *
282 * The caller must call unlocked_inode_to_wb_end() with *@cookie afterwards and
283 * can't sleep during the transaction. IRQs may or may not be disabled on
284 * return.
285 */
286static inline struct bdi_writeback *
287unlocked_inode_to_wb_begin(struct inode *inode, struct wb_lock_cookie *cookie)
288{
289 rcu_read_lock();
290
291 /*
292 * Paired with store_release in inode_switch_wbs_work_fn() and
293 * ensures that we see the new wb if we see cleared I_WB_SWITCH.
294 */
295 cookie->locked = smp_load_acquire(&inode->i_state) & I_WB_SWITCH;
296
297 if (unlikely(cookie->locked))
298 xa_lock_irqsave(&inode->i_mapping->i_pages, cookie->flags);
299
300 /*
301 * Protected by either !I_WB_SWITCH + rcu_read_lock() or the i_pages
302 * lock. inode_to_wb() will bark. Deref directly.
303 */
304 return inode->i_wb;
305}
306
307/**
308 * unlocked_inode_to_wb_end - end inode wb access transaction
309 * @inode: target inode
310 * @cookie: @cookie from unlocked_inode_to_wb_begin()
311 */
312static inline void unlocked_inode_to_wb_end(struct inode *inode,
313 struct wb_lock_cookie *cookie)
314{
315 if (unlikely(cookie->locked))
316 xa_unlock_irqrestore(&inode->i_mapping->i_pages, cookie->flags);
317
318 rcu_read_unlock();
319}
320
321#else /* CONFIG_CGROUP_WRITEBACK */
322
323static inline bool inode_cgwb_enabled(struct inode *inode)
324{
325 return false;
326}
327
328static inline struct bdi_writeback *wb_find_current(struct backing_dev_info *bdi)
329{
330 return &bdi->wb;
331}
332
333static inline struct bdi_writeback *
334wb_get_create_current(struct backing_dev_info *bdi, gfp_t gfp)
335{
336 return &bdi->wb;
337}
338
339static inline struct bdi_writeback *inode_to_wb(struct inode *inode)
340{
341 return &inode_to_bdi(inode)->wb;
342}
343
344static inline struct bdi_writeback *inode_to_wb_wbc(
345 struct inode *inode,
346 struct writeback_control *wbc)
347{
348 return inode_to_wb(inode);
349}
350
351
352static inline struct bdi_writeback *
353unlocked_inode_to_wb_begin(struct inode *inode, struct wb_lock_cookie *cookie)
354{
355 return inode_to_wb(inode);
356}
357
358static inline void unlocked_inode_to_wb_end(struct inode *inode,
359 struct wb_lock_cookie *cookie)
360{
361}
362
363static inline void wb_memcg_offline(struct mem_cgroup *memcg)
364{
365}
366
367static inline void wb_blkcg_offline(struct cgroup_subsys_state *css)
368{
369}
370
371#endif /* CONFIG_CGROUP_WRITEBACK */
372
373const char *bdi_dev_name(struct backing_dev_info *bdi);
374
375#endif /* _LINUX_BACKING_DEV_H */
376

source code of linux/include/linux/backing-dev.h