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/blkdev.h>
16#include <linux/writeback.h>
17#include <linux/blk-cgroup.h>
18#include <linux/backing-dev-defs.h>
19#include <linux/slab.h>
20
21static inline struct backing_dev_info *bdi_get(struct backing_dev_info *bdi)
22{
23 kref_get(&bdi->refcnt);
24 return bdi;
25}
26
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);
34int bdi_register_owner(struct backing_dev_info *bdi, struct device *owner);
35void bdi_unregister(struct backing_dev_info *bdi);
36
37struct backing_dev_info *bdi_alloc_node(gfp_t gfp_mask, int node_id);
38static inline struct backing_dev_info *bdi_alloc(gfp_t gfp_mask)
39{
40 return bdi_alloc_node(gfp_mask, NUMA_NO_NODE);
41}
42
43void wb_start_background_writeback(struct bdi_writeback *wb);
44void wb_workfn(struct work_struct *work);
45void wb_wakeup_delayed(struct bdi_writeback *wb);
46
47extern spinlock_t bdi_lock;
48extern struct list_head bdi_list;
49
50extern struct workqueue_struct *bdi_wq;
51
52static inline bool wb_has_dirty_io(struct bdi_writeback *wb)
53{
54 return test_bit(WB_has_dirty_io, &wb->state);
55}
56
57static inline bool bdi_has_dirty_io(struct backing_dev_info *bdi)
58{
59 /*
60 * @bdi->tot_write_bandwidth is guaranteed to be > 0 if there are
61 * any dirty wbs. See wb_update_write_bandwidth().
62 */
63 return atomic_long_read(&bdi->tot_write_bandwidth);
64}
65
66static inline void __add_wb_stat(struct bdi_writeback *wb,
67 enum wb_stat_item item, s64 amount)
68{
69 percpu_counter_add_batch(&wb->stat[item], amount, WB_STAT_BATCH);
70}
71
72static inline void inc_wb_stat(struct bdi_writeback *wb, enum wb_stat_item item)
73{
74 __add_wb_stat(wb, item, 1);
75}
76
77static inline void dec_wb_stat(struct bdi_writeback *wb, enum wb_stat_item item)
78{
79 __add_wb_stat(wb, item, -1);
80}
81
82static inline s64 wb_stat(struct bdi_writeback *wb, enum wb_stat_item item)
83{
84 return percpu_counter_read_positive(&wb->stat[item]);
85}
86
87static inline s64 wb_stat_sum(struct bdi_writeback *wb, enum wb_stat_item item)
88{
89 return percpu_counter_sum_positive(&wb->stat[item]);
90}
91
92extern void wb_writeout_inc(struct bdi_writeback *wb);
93
94/*
95 * maximal error of a stat counter.
96 */
97static inline unsigned long wb_stat_error(void)
98{
99#ifdef CONFIG_SMP
100 return nr_cpu_ids * WB_STAT_BATCH;
101#else
102 return 1;
103#endif
104}
105
106int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio);
107int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio);
108
109/*
110 * Flags in backing_dev_info::capability
111 *
112 * The first three flags control whether dirty pages will contribute to the
113 * VM's accounting and whether writepages() should be called for dirty pages
114 * (something that would not, for example, be appropriate for ramfs)
115 *
116 * WARNING: these flags are closely related and should not normally be
117 * used separately. The BDI_CAP_NO_ACCT_AND_WRITEBACK combines these
118 * three flags into a single convenience macro.
119 *
120 * BDI_CAP_NO_ACCT_DIRTY: Dirty pages shouldn't contribute to accounting
121 * BDI_CAP_NO_WRITEBACK: Don't write pages back
122 * BDI_CAP_NO_ACCT_WB: Don't automatically account writeback pages
123 * BDI_CAP_STRICTLIMIT: Keep number of dirty pages below bdi threshold.
124 *
125 * BDI_CAP_CGROUP_WRITEBACK: Supports cgroup-aware writeback.
126 * BDI_CAP_SYNCHRONOUS_IO: Device is so fast that asynchronous IO would be
127 * inefficient.
128 */
129#define BDI_CAP_NO_ACCT_DIRTY 0x00000001
130#define BDI_CAP_NO_WRITEBACK 0x00000002
131#define BDI_CAP_NO_ACCT_WB 0x00000004
132#define BDI_CAP_STABLE_WRITES 0x00000008
133#define BDI_CAP_STRICTLIMIT 0x00000010
134#define BDI_CAP_CGROUP_WRITEBACK 0x00000020
135#define BDI_CAP_SYNCHRONOUS_IO 0x00000040
136
137#define BDI_CAP_NO_ACCT_AND_WRITEBACK \
138 (BDI_CAP_NO_WRITEBACK | BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_ACCT_WB)
139
140extern struct backing_dev_info noop_backing_dev_info;
141
142/**
143 * writeback_in_progress - determine whether there is writeback in progress
144 * @wb: bdi_writeback of interest
145 *
146 * Determine whether there is writeback waiting to be handled against a
147 * bdi_writeback.
148 */
149static inline bool writeback_in_progress(struct bdi_writeback *wb)
150{
151 return test_bit(WB_writeback_running, &wb->state);
152}
153
154static inline struct backing_dev_info *inode_to_bdi(struct inode *inode)
155{
156 struct super_block *sb;
157
158 if (!inode)
159 return &noop_backing_dev_info;
160
161 sb = inode->i_sb;
162#ifdef CONFIG_BLOCK
163 if (sb_is_blkdev_sb(sb))
164 return I_BDEV(inode)->bd_bdi;
165#endif
166 return sb->s_bdi;
167}
168
169static inline int wb_congested(struct bdi_writeback *wb, int cong_bits)
170{
171 struct backing_dev_info *bdi = wb->bdi;
172
173 if (bdi->congested_fn)
174 return bdi->congested_fn(bdi->congested_data, cong_bits);
175 return wb->congested->state & cong_bits;
176}
177
178long congestion_wait(int sync, long timeout);
179long wait_iff_congested(int sync, long timeout);
180
181static inline bool bdi_cap_synchronous_io(struct backing_dev_info *bdi)
182{
183 return bdi->capabilities & BDI_CAP_SYNCHRONOUS_IO;
184}
185
186static inline bool bdi_cap_stable_pages_required(struct backing_dev_info *bdi)
187{
188 return bdi->capabilities & BDI_CAP_STABLE_WRITES;
189}
190
191static inline bool bdi_cap_writeback_dirty(struct backing_dev_info *bdi)
192{
193 return !(bdi->capabilities & BDI_CAP_NO_WRITEBACK);
194}
195
196static inline bool bdi_cap_account_dirty(struct backing_dev_info *bdi)
197{
198 return !(bdi->capabilities & BDI_CAP_NO_ACCT_DIRTY);
199}
200
201static inline bool bdi_cap_account_writeback(struct backing_dev_info *bdi)
202{
203 /* Paranoia: BDI_CAP_NO_WRITEBACK implies BDI_CAP_NO_ACCT_WB */
204 return !(bdi->capabilities & (BDI_CAP_NO_ACCT_WB |
205 BDI_CAP_NO_WRITEBACK));
206}
207
208static inline bool mapping_cap_writeback_dirty(struct address_space *mapping)
209{
210 return bdi_cap_writeback_dirty(inode_to_bdi(mapping->host));
211}
212
213static inline bool mapping_cap_account_dirty(struct address_space *mapping)
214{
215 return bdi_cap_account_dirty(inode_to_bdi(mapping->host));
216}
217
218static inline int bdi_sched_wait(void *word)
219{
220 schedule();
221 return 0;
222}
223
224#ifdef CONFIG_CGROUP_WRITEBACK
225
226struct bdi_writeback_congested *
227wb_congested_get_create(struct backing_dev_info *bdi, int blkcg_id, gfp_t gfp);
228void wb_congested_put(struct bdi_writeback_congested *congested);
229struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
230 struct cgroup_subsys_state *memcg_css,
231 gfp_t gfp);
232void wb_memcg_offline(struct mem_cgroup *memcg);
233void wb_blkcg_offline(struct blkcg *blkcg);
234int inode_congested(struct inode *inode, int cong_bits);
235
236/**
237 * inode_cgwb_enabled - test whether cgroup writeback is enabled on an inode
238 * @inode: inode of interest
239 *
240 * cgroup writeback requires support from both the bdi and filesystem.
241 * Also, both memcg and iocg have to be on the default hierarchy. Test
242 * whether all conditions are met.
243 *
244 * Note that the test result may change dynamically on the same inode
245 * depending on how memcg and iocg are configured.
246 */
247static inline bool inode_cgwb_enabled(struct inode *inode)
248{
249 struct backing_dev_info *bdi = inode_to_bdi(inode);
250
251 return cgroup_subsys_on_dfl(memory_cgrp_subsys) &&
252 cgroup_subsys_on_dfl(io_cgrp_subsys) &&
253 bdi_cap_account_dirty(bdi) &&
254 (bdi->capabilities & BDI_CAP_CGROUP_WRITEBACK) &&
255 (inode->i_sb->s_iflags & SB_I_CGROUPWB);
256}
257
258/**
259 * wb_find_current - find wb for %current on a bdi
260 * @bdi: bdi of interest
261 *
262 * Find the wb of @bdi which matches both the memcg and blkcg of %current.
263 * Must be called under rcu_read_lock() which protects the returend wb.
264 * NULL if not found.
265 */
266static inline struct bdi_writeback *wb_find_current(struct backing_dev_info *bdi)
267{
268 struct cgroup_subsys_state *memcg_css;
269 struct bdi_writeback *wb;
270
271 memcg_css = task_css(current, memory_cgrp_id);
272 if (!memcg_css->parent)
273 return &bdi->wb;
274
275 wb = radix_tree_lookup(&bdi->cgwb_tree, memcg_css->id);
276
277 /*
278 * %current's blkcg equals the effective blkcg of its memcg. No
279 * need to use the relatively expensive cgroup_get_e_css().
280 */
281 if (likely(wb && wb->blkcg_css == task_css(current, io_cgrp_id)))
282 return wb;
283 return NULL;
284}
285
286/**
287 * wb_get_create_current - get or create wb for %current on a bdi
288 * @bdi: bdi of interest
289 * @gfp: allocation mask
290 *
291 * Equivalent to wb_get_create() on %current's memcg. This function is
292 * called from a relatively hot path and optimizes the common cases using
293 * wb_find_current().
294 */
295static inline struct bdi_writeback *
296wb_get_create_current(struct backing_dev_info *bdi, gfp_t gfp)
297{
298 struct bdi_writeback *wb;
299
300 rcu_read_lock();
301 wb = wb_find_current(bdi);
302 if (wb && unlikely(!wb_tryget(wb)))
303 wb = NULL;
304 rcu_read_unlock();
305
306 if (unlikely(!wb)) {
307 struct cgroup_subsys_state *memcg_css;
308
309 memcg_css = task_get_css(current, memory_cgrp_id);
310 wb = wb_get_create(bdi, memcg_css, gfp);
311 css_put(memcg_css);
312 }
313 return wb;
314}
315
316/**
317 * inode_to_wb_is_valid - test whether an inode has a wb associated
318 * @inode: inode of interest
319 *
320 * Returns %true if @inode has a wb associated. May be called without any
321 * locking.
322 */
323static inline bool inode_to_wb_is_valid(struct inode *inode)
324{
325 return inode->i_wb;
326}
327
328/**
329 * inode_to_wb - determine the wb of an inode
330 * @inode: inode of interest
331 *
332 * Returns the wb @inode is currently associated with. The caller must be
333 * holding either @inode->i_lock, the i_pages lock, or the
334 * associated wb's list_lock.
335 */
336static inline struct bdi_writeback *inode_to_wb(const struct inode *inode)
337{
338#ifdef CONFIG_LOCKDEP
339 WARN_ON_ONCE(debug_locks &&
340 (!lockdep_is_held(&inode->i_lock) &&
341 !lockdep_is_held(&inode->i_mapping->i_pages.xa_lock) &&
342 !lockdep_is_held(&inode->i_wb->list_lock)));
343#endif
344 return inode->i_wb;
345}
346
347/**
348 * unlocked_inode_to_wb_begin - begin unlocked inode wb access transaction
349 * @inode: target inode
350 * @cookie: output param, to be passed to the end function
351 *
352 * The caller wants to access the wb associated with @inode but isn't
353 * holding inode->i_lock, the i_pages lock or wb->list_lock. This
354 * function determines the wb associated with @inode and ensures that the
355 * association doesn't change until the transaction is finished with
356 * unlocked_inode_to_wb_end().
357 *
358 * The caller must call unlocked_inode_to_wb_end() with *@cookie afterwards and
359 * can't sleep during the transaction. IRQs may or may not be disabled on
360 * return.
361 */
362static inline struct bdi_writeback *
363unlocked_inode_to_wb_begin(struct inode *inode, struct wb_lock_cookie *cookie)
364{
365 rcu_read_lock();
366
367 /*
368 * Paired with store_release in inode_switch_wbs_work_fn() and
369 * ensures that we see the new wb if we see cleared I_WB_SWITCH.
370 */
371 cookie->locked = smp_load_acquire(&inode->i_state) & I_WB_SWITCH;
372
373 if (unlikely(cookie->locked))
374 xa_lock_irqsave(&inode->i_mapping->i_pages, cookie->flags);
375
376 /*
377 * Protected by either !I_WB_SWITCH + rcu_read_lock() or the i_pages
378 * lock. inode_to_wb() will bark. Deref directly.
379 */
380 return inode->i_wb;
381}
382
383/**
384 * unlocked_inode_to_wb_end - end inode wb access transaction
385 * @inode: target inode
386 * @cookie: @cookie from unlocked_inode_to_wb_begin()
387 */
388static inline void unlocked_inode_to_wb_end(struct inode *inode,
389 struct wb_lock_cookie *cookie)
390{
391 if (unlikely(cookie->locked))
392 xa_unlock_irqrestore(&inode->i_mapping->i_pages, cookie->flags);
393
394 rcu_read_unlock();
395}
396
397#else /* CONFIG_CGROUP_WRITEBACK */
398
399static inline bool inode_cgwb_enabled(struct inode *inode)
400{
401 return false;
402}
403
404static inline struct bdi_writeback_congested *
405wb_congested_get_create(struct backing_dev_info *bdi, int blkcg_id, gfp_t gfp)
406{
407 refcount_inc(&bdi->wb_congested->refcnt);
408 return bdi->wb_congested;
409}
410
411static inline void wb_congested_put(struct bdi_writeback_congested *congested)
412{
413 if (refcount_dec_and_test(&congested->refcnt))
414 kfree(congested);
415}
416
417static inline struct bdi_writeback *wb_find_current(struct backing_dev_info *bdi)
418{
419 return &bdi->wb;
420}
421
422static inline struct bdi_writeback *
423wb_get_create_current(struct backing_dev_info *bdi, gfp_t gfp)
424{
425 return &bdi->wb;
426}
427
428static inline bool inode_to_wb_is_valid(struct inode *inode)
429{
430 return true;
431}
432
433static inline struct bdi_writeback *inode_to_wb(struct inode *inode)
434{
435 return &inode_to_bdi(inode)->wb;
436}
437
438static inline struct bdi_writeback *
439unlocked_inode_to_wb_begin(struct inode *inode, struct wb_lock_cookie *cookie)
440{
441 return inode_to_wb(inode);
442}
443
444static inline void unlocked_inode_to_wb_end(struct inode *inode,
445 struct wb_lock_cookie *cookie)
446{
447}
448
449static inline void wb_memcg_offline(struct mem_cgroup *memcg)
450{
451}
452
453static inline void wb_blkcg_offline(struct blkcg *blkcg)
454{
455}
456
457static inline int inode_congested(struct inode *inode, int cong_bits)
458{
459 return wb_congested(&inode_to_bdi(inode)->wb, cong_bits);
460}
461
462#endif /* CONFIG_CGROUP_WRITEBACK */
463
464static inline int inode_read_congested(struct inode *inode)
465{
466 return inode_congested(inode, 1 << WB_sync_congested);
467}
468
469static inline int inode_write_congested(struct inode *inode)
470{
471 return inode_congested(inode, 1 << WB_async_congested);
472}
473
474static inline int inode_rw_congested(struct inode *inode)
475{
476 return inode_congested(inode, (1 << WB_sync_congested) |
477 (1 << WB_async_congested));
478}
479
480static inline int bdi_congested(struct backing_dev_info *bdi, int cong_bits)
481{
482 return wb_congested(&bdi->wb, cong_bits);
483}
484
485static inline int bdi_read_congested(struct backing_dev_info *bdi)
486{
487 return bdi_congested(bdi, 1 << WB_sync_congested);
488}
489
490static inline int bdi_write_congested(struct backing_dev_info *bdi)
491{
492 return bdi_congested(bdi, 1 << WB_async_congested);
493}
494
495static inline int bdi_rw_congested(struct backing_dev_info *bdi)
496{
497 return bdi_congested(bdi, (1 << WB_sync_congested) |
498 (1 << WB_async_congested));
499}
500
501#endif /* _LINUX_BACKING_DEV_H */
502