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 <asm/atomic.h>
15
16 struct page;
17
18 /*
19 * Bits in backing_dev_info.state
20 */
21 enum bdi_state {
22 BDI_pdflush, /* A pdflush thread is working this device */
23 BDI_write_congested, /* The write queue is getting full */
24 BDI_read_congested, /* The read queue is getting full */
25 BDI_unused, /* Available bits start here */
26 };
27
28 typedef int (congested_fn)(void *, int);
29
30 enum bdi_stat_item {
31 BDI_RECLAIMABLE,
32 BDI_WRITEBACK,
33 NR_BDI_STAT_ITEMS
34 };
35
36 #define BDI_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))
37
38 struct backing_dev_info {
39 unsigned long ra_pages; /* max readahead in PAGE_CACHE_SIZE units */
40 unsigned long state; /* Always use atomic bitops on this */
41 unsigned int capabilities; /* Device capabilities */
42 congested_fn *congested_fn; /* Function pointer if device is md/dm */
43 void *congested_data; /* Pointer to aux data for congested func */
44 void (*unplug_io_fn)(struct backing_dev_info *, struct page *);
45 void *unplug_io_data;
46
47 struct percpu_counter bdi_stat[NR_BDI_STAT_ITEMS];
48
49 struct prop_local_percpu completions;
50 int dirty_exceeded;
51 };
52
53 int bdi_init(struct backing_dev_info *bdi);
54 void bdi_destroy(struct backing_dev_info *bdi);
55
56 static inline void __add_bdi_stat(struct backing_dev_info *bdi,
57 enum bdi_stat_item item, s64 amount)
58 {
59 __percpu_counter_add(&bdi->bdi_stat[item], amount, BDI_STAT_BATCH);
60 }
61
62 static inline void __inc_bdi_stat(struct backing_dev_info *bdi,
63 enum bdi_stat_item item)
64 {
65 __add_bdi_stat(bdi, item, 1);
66 }
67
68 static inline void inc_bdi_stat(struct backing_dev_info *bdi,
69 enum bdi_stat_item item)
70 {
71 unsigned long flags;
72
73 local_irq_save(flags);
74 __inc_bdi_stat(bdi, item);
75 local_irq_restore(flags);
76 }
77
78 static inline void __dec_bdi_stat(struct backing_dev_info *bdi,
79 enum bdi_stat_item item)
80 {
81 __add_bdi_stat(bdi, item, -1);
82 }
83
84 static inline void dec_bdi_stat(struct backing_dev_info *bdi,
85 enum bdi_stat_item item)
86 {
87 unsigned long flags;
88
89 local_irq_save(flags);
90 __dec_bdi_stat(bdi, item);
91 local_irq_restore(flags);
92 }
93
94 static inline s64 bdi_stat(struct backing_dev_info *bdi,
95 enum bdi_stat_item item)
96 {
97 return percpu_counter_read_positive(&bdi->bdi_stat[item]);
98 }
99
100 static inline s64 __bdi_stat_sum(struct backing_dev_info *bdi,
101 enum bdi_stat_item item)
102 {
103 return percpu_counter_sum_positive(&bdi->bdi_stat[item]);
104 }
105
106 static inline s64 bdi_stat_sum(struct backing_dev_info *bdi,
107 enum bdi_stat_item item)
108 {
109 s64 sum;
110 unsigned long flags;
111
112 local_irq_save(flags);
113 sum = __bdi_stat_sum(bdi, item);
114 local_irq_restore(flags);
115
116 return sum;
117 }
118
119 /*
120 * maximal error of a stat counter.
121 */
122 static inline unsigned long bdi_stat_error(struct backing_dev_info *bdi)
123 {
124 #ifdef CONFIG_SMP
125 return nr_cpu_ids * BDI_STAT_BATCH;
126 #else
127 return 1;
128 #endif
129 }
130
131 /*
132 * Flags in backing_dev_info::capability
133 * - The first two flags control whether dirty pages will contribute to the
134 * VM's accounting and whether writepages() should be called for dirty pages
135 * (something that would not, for example, be appropriate for ramfs)
136 * - These flags let !MMU mmap() govern direct device mapping vs immediate
137 * copying more easily for MAP_PRIVATE, especially for ROM filesystems
138 */
139 #define BDI_CAP_NO_ACCT_DIRTY 0x00000001 /* Dirty pages shouldn't contribute to accounting */
140 #define BDI_CAP_NO_WRITEBACK 0x00000002 /* Don't write pages back */
141 #define BDI_CAP_MAP_COPY 0x00000004 /* Copy can be mapped (MAP_PRIVATE) */
142 #define BDI_CAP_MAP_DIRECT 0x00000008 /* Can be mapped directly (MAP_SHARED) */
143 #define BDI_CAP_READ_MAP 0x00000010 /* Can be mapped for reading */
144 #define BDI_CAP_WRITE_MAP 0x00000020 /* Can be mapped for writing */
145 #define BDI_CAP_EXEC_MAP 0x00000040 /* Can be mapped for execution */
146 #define BDI_CAP_VMFLAGS \
147 (BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP)
148
149 #if defined(VM_MAYREAD) && \
150 (BDI_CAP_READ_MAP != VM_MAYREAD || \
151 BDI_CAP_WRITE_MAP != VM_MAYWRITE || \
152 BDI_CAP_EXEC_MAP != VM_MAYEXEC)
153 #error please change backing_dev_info::capabilities flags
154 #endif
155
156 extern struct backing_dev_info default_backing_dev_info;
157 void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page);
158
159 int writeback_acquire(struct backing_dev_info *bdi);
160 int writeback_in_progress(struct backing_dev_info *bdi);
161 void writeback_release(struct backing_dev_info *bdi);
162
163 static inline int bdi_congested(struct backing_dev_info *bdi, int bdi_bits)
164 {
165 if (bdi->congested_fn)
166 return bdi->congested_fn(bdi->congested_data, bdi_bits);
167 return (bdi->state & bdi_bits);
168 }
169
170 static inline int bdi_read_congested(struct backing_dev_info *bdi)
171 {
172 return bdi_congested(bdi, 1 << BDI_read_congested);
173 }
174
175 static inline int bdi_write_congested(struct backing_dev_info *bdi)
176 {
177 return bdi_congested(bdi, 1 << BDI_write_congested);
178 }
179
180 static inline int bdi_rw_congested(struct backing_dev_info *bdi)
181 {
182 return bdi_congested(bdi, (1 << BDI_read_congested)|
183 (1 << BDI_write_congested));
184 }
185
186 void clear_bdi_congested(struct backing_dev_info *bdi, int rw);
187 void set_bdi_congested(struct backing_dev_info *bdi, int rw);
188 long congestion_wait(int rw, long timeout);
189
190 #define bdi_cap_writeback_dirty(bdi) \
191 (!((bdi)->capabilities & BDI_CAP_NO_WRITEBACK))
192
193 #define bdi_cap_account_dirty(bdi) \
194 (!((bdi)->capabilities & BDI_CAP_NO_ACCT_DIRTY))
195
196 #define mapping_cap_writeback_dirty(mapping) \
197 bdi_cap_writeback_dirty((mapping)->backing_dev_info)
198
199 #define mapping_cap_account_dirty(mapping) \
200 bdi_cap_account_dirty((mapping)->backing_dev_info)
201
202
203 #endif /* _LINUX_BACKING_DEV_H */
204
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