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