1 /*
2 * include/linux/backing-dev.h
3 *
4 * low-level device information and state which is propagated up through
5 * to high-level code.
6 */
7
8 #ifndef _LINUX_BACKING_DEV_H
9 #define _LINUX_BACKING_DEV_H
10
11 #include <linux/percpu_counter.h>
12 #include <linux/log2.h>
13 #include <linux/proportions.h>
14 #include <linux/kernel.h>
15 #include <linux/fs.h>
16 #include <asm/atomic.h>
17
18 struct page;
19 struct device;
20 struct dentry;
21
22 /*
23 * Bits in backing_dev_info.state
24 */
25 enum bdi_state {
26 BDI_pdflush, /* A pdflush thread is working this device */
27 BDI_async_congested, /* The async (write) queue is getting full */
28 BDI_sync_congested, /* The sync queue is getting full */
29 BDI_unused, /* Available bits start here */
30 };
31
32 typedef int (congested_fn)(void *, int);
33
34 enum bdi_stat_item {
35 BDI_RECLAIMABLE,
36 BDI_WRITEBACK,
37 NR_BDI_STAT_ITEMS
38 };
39
40 #define BDI_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))
41
42 struct backing_dev_info {
43 unsigned long ra_pages; /* max readahead in PAGE_CACHE_SIZE units */
44 unsigned long state; /* Always use atomic bitops on this */
45 unsigned int capabilities; /* Device capabilities */
46 congested_fn *congested_fn; /* Function pointer if device is md/dm */
47 void *congested_data; /* Pointer to aux data for congested func */
48 void (*unplug_io_fn)(struct backing_dev_info *, struct page *);
49 void *unplug_io_data;
50
51 struct percpu_counter bdi_stat[NR_BDI_STAT_ITEMS];
52
53 struct prop_local_percpu completions;
54 int dirty_exceeded;
55
56 unsigned int min_ratio;
57 unsigned int max_ratio, max_prop_frac;
58
59 struct device *dev;
60
61 #ifdef CONFIG_DEBUG_FS
62 struct dentry *debug_dir;
63 struct dentry *debug_stats;
64 #endif
65 };
66
67 int bdi_init(struct backing_dev_info *bdi);
68 void bdi_destroy(struct backing_dev_info *bdi);
69
70 int bdi_register(struct backing_dev_info *bdi, struct device *parent,
71 const char *fmt, ...);
72 int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev);
73 void bdi_unregister(struct backing_dev_info *bdi);
74
75 static inline void __add_bdi_stat(struct backing_dev_info *bdi,
76 enum bdi_stat_item item, s64 amount)
77 {
78 __percpu_counter_add(&bdi->bdi_stat[item], amount, BDI_STAT_BATCH);
79 }
80
81 static inline void __inc_bdi_stat(struct backing_dev_info *bdi,
82 enum bdi_stat_item item)
83 {
84 __add_bdi_stat(bdi, item, 1);
85 }
86
87 static inline void inc_bdi_stat(struct backing_dev_info *bdi,
88 enum bdi_stat_item item)
89 {
90 unsigned long flags;
91
92 local_irq_save(flags);
93 __inc_bdi_stat(bdi, item);
94 local_irq_restore(flags);
95 }
96
97 static inline void __dec_bdi_stat(struct backing_dev_info *bdi,
98 enum bdi_stat_item item)
99 {
100 __add_bdi_stat(bdi, item, -1);
101 }
102
103 static inline void dec_bdi_stat(struct backing_dev_info *bdi,
104 enum bdi_stat_item item)
105 {
106 unsigned long flags;
107
108 local_irq_save(flags);
109 __dec_bdi_stat(bdi, item);
110 local_irq_restore(flags);
111 }
112
113 static inline s64 bdi_stat(struct backing_dev_info *bdi,
114 enum bdi_stat_item item)
115 {
116 return percpu_counter_read_positive(&bdi->bdi_stat[item]);
117 }
118
119 static inline s64 __bdi_stat_sum(struct backing_dev_info *bdi,
120 enum bdi_stat_item item)
121 {
122 return percpu_counter_sum_positive(&bdi->bdi_stat[item]);
123 }
124
125 static inline s64 bdi_stat_sum(struct backing_dev_info *bdi,
126 enum bdi_stat_item item)
127 {
128 s64 sum;
129 unsigned long flags;
130
131 local_irq_save(flags);
132 sum = __bdi_stat_sum(bdi, item);
133 local_irq_restore(flags);
134
135 return sum;
136 }
137
138 extern void bdi_writeout_inc(struct backing_dev_info *bdi);
139
140 /*
141 * maximal error of a stat counter.
142 */
143 static inline unsigned long bdi_stat_error(struct backing_dev_info *bdi)
144 {
145 #ifdef CONFIG_SMP
146 return nr_cpu_ids * BDI_STAT_BATCH;
147 #else
148 return 1;
149 #endif
150 }
151
152 int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio);
153 int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio);
154
155 /*
156 * Flags in backing_dev_info::capability
157 *
158 * The first three flags control whether dirty pages will contribute to the
159 * VM's accounting and whether writepages() should be called for dirty pages
160 * (something that would not, for example, be appropriate for ramfs)
161 *
162 * WARNING: these flags are closely related and should not normally be
163 * used separately. The BDI_CAP_NO_ACCT_AND_WRITEBACK combines these
164 * three flags into a single convenience macro.
165 *
166 * BDI_CAP_NO_ACCT_DIRTY: Dirty pages shouldn't contribute to accounting
167 * BDI_CAP_NO_WRITEBACK: Don't write pages back
168 * BDI_CAP_NO_ACCT_WB: Don't automatically account writeback pages
169 *
170 * These flags let !MMU mmap() govern direct device mapping vs immediate
171 * copying more easily for MAP_PRIVATE, especially for ROM filesystems.
172 *
173 * BDI_CAP_MAP_COPY: Copy can be mapped (MAP_PRIVATE)
174 * BDI_CAP_MAP_DIRECT: Can be mapped directly (MAP_SHARED)
175 * BDI_CAP_READ_MAP: Can be mapped for reading
176 * BDI_CAP_WRITE_MAP: Can be mapped for writing
177 * BDI_CAP_EXEC_MAP: Can be mapped for execution
178 *
179 * BDI_CAP_SWAP_BACKED: Count shmem/tmpfs objects as swap-backed.
180 */
181 #define BDI_CAP_NO_ACCT_DIRTY 0x00000001
182 #define BDI_CAP_NO_WRITEBACK 0x00000002
183 #define BDI_CAP_MAP_COPY 0x00000004
184 #define BDI_CAP_MAP_DIRECT 0x00000008
185 #define BDI_CAP_READ_MAP 0x00000010
186 #define BDI_CAP_WRITE_MAP 0x00000020
187 #define BDI_CAP_EXEC_MAP 0x00000040
188 #define BDI_CAP_NO_ACCT_WB 0x00000080
189 #define BDI_CAP_SWAP_BACKED 0x00000100
190
191 #define BDI_CAP_VMFLAGS \
192 (BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP)
193
194 #define BDI_CAP_NO_ACCT_AND_WRITEBACK \
195 (BDI_CAP_NO_WRITEBACK | BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_ACCT_WB)
196
197 #if defined(VM_MAYREAD) && \
198 (BDI_CAP_READ_MAP != VM_MAYREAD || \
199 BDI_CAP_WRITE_MAP != VM_MAYWRITE || \
200 BDI_CAP_EXEC_MAP != VM_MAYEXEC)
201 #error please change backing_dev_info::capabilities flags
202 #endif
203
204 extern struct backing_dev_info default_backing_dev_info;
205 void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page);
206
207 int writeback_in_progress(struct backing_dev_info *bdi);
208
209 static inline int bdi_congested(struct backing_dev_info *bdi, int bdi_bits)
210 {
211 if (bdi->congested_fn)
212 return bdi->congested_fn(bdi->congested_data, bdi_bits);
213 return (bdi->state & bdi_bits);
214 }
215
216 static inline int bdi_read_congested(struct backing_dev_info *bdi)
217 {
218 return bdi_congested(bdi, 1 << BDI_sync_congested);
219 }
220
221 static inline int bdi_write_congested(struct backing_dev_info *bdi)
222 {
223 return bdi_congested(bdi, 1 << BDI_async_congested);
224 }
225
226 static inline int bdi_rw_congested(struct backing_dev_info *bdi)
227 {
228 return bdi_congested(bdi, (1 << BDI_sync_congested) |
229 (1 << BDI_async_congested));
230 }
231
232 enum {
233 BLK_RW_ASYNC = 0,
234 BLK_RW_SYNC = 1,
235 };
236
237 void clear_bdi_congested(struct backing_dev_info *bdi, int sync);
238 void set_bdi_congested(struct backing_dev_info *bdi, int sync);
239 long congestion_wait(int sync, long timeout);
240
241
242 static inline bool bdi_cap_writeback_dirty(struct backing_dev_info *bdi)
243 {
244 return !(bdi->capabilities & BDI_CAP_NO_WRITEBACK);
245 }
246
247 static inline bool bdi_cap_account_dirty(struct backing_dev_info *bdi)
248 {
249 return !(bdi->capabilities & BDI_CAP_NO_ACCT_DIRTY);
250 }
251
252 static inline bool bdi_cap_account_writeback(struct backing_dev_info *bdi)
253 {
254 /* Paranoia: BDI_CAP_NO_WRITEBACK implies BDI_CAP_NO_ACCT_WB */
255 return !(bdi->capabilities & (BDI_CAP_NO_ACCT_WB |
256 BDI_CAP_NO_WRITEBACK));
257 }
258
259 static inline bool bdi_cap_swap_backed(struct backing_dev_info *bdi)
260 {
261 return bdi->capabilities & BDI_CAP_SWAP_BACKED;
262 }
263
264 static inline bool mapping_cap_writeback_dirty(struct address_space *mapping)
265 {
266 return bdi_cap_writeback_dirty(mapping->backing_dev_info);
267 }
268
269 static inline bool mapping_cap_account_dirty(struct address_space *mapping)
270 {
271 return bdi_cap_account_dirty(mapping->backing_dev_info);
272 }
273
274 static inline bool mapping_cap_swap_backed(struct address_space *mapping)
275 {
276 return bdi_cap_swap_backed(mapping->backing_dev_info);
277 }
278
279 #endif /* _LINUX_BACKING_DEV_H */
280
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