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