Linux kernel mirror (for testing)
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linux
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
16struct page;
17
18/*
19 * Bits in backing_dev_info.state
20 */
21enum 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
28typedef int (congested_fn)(void *, int);
29
30enum 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
38struct 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
53int bdi_init(struct backing_dev_info *bdi);
54void bdi_destroy(struct backing_dev_info *bdi);
55
56static 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
62static 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
68static 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
78static 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
84static 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
94static 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
100static 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
106static 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 */
122static 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
156extern struct backing_dev_info default_backing_dev_info;
157void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page);
158
159int writeback_acquire(struct backing_dev_info *bdi);
160int writeback_in_progress(struct backing_dev_info *bdi);
161void writeback_release(struct backing_dev_info *bdi);
162
163static 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
170static inline int bdi_read_congested(struct backing_dev_info *bdi)
171{
172 return bdi_congested(bdi, 1 << BDI_read_congested);
173}
174
175static inline int bdi_write_congested(struct backing_dev_info *bdi)
176{
177 return bdi_congested(bdi, 1 << BDI_write_congested);
178}
179
180static 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
186void clear_bdi_congested(struct backing_dev_info *bdi, int rw);
187void set_bdi_congested(struct backing_dev_info *bdi, int rw);
188long 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 */