projects/linux·blob v6.14-rc6 · refs

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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 */