2 * include/linux/backing-dev.h
4 * low-level device information and state which is propagated up through
8 #ifndef _LINUX_BACKING_DEV_H
9 #define _LINUX_BACKING_DEV_H
11 #include <linux/percpu_counter.h>
12 #include <linux/log2.h>
13 #include <asm/atomic.h>
18 * Bits in backing_dev_info.state
21 BDI_pdflush
, /* A pdflush thread is working this device */
22 BDI_write_congested
, /* The write queue is getting full */
23 BDI_read_congested
, /* The read queue is getting full */
24 BDI_unused
, /* Available bits start here */
27 typedef int (congested_fn
)(void *, int);
35 #define BDI_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))
37 struct backing_dev_info
{
38 unsigned long ra_pages
; /* max readahead in PAGE_CACHE_SIZE units */
39 unsigned long state
; /* Always use atomic bitops on this */
40 unsigned int capabilities
; /* Device capabilities */
41 congested_fn
*congested_fn
; /* Function pointer if device is md/dm */
42 void *congested_data
; /* Pointer to aux data for congested func */
43 void (*unplug_io_fn
)(struct backing_dev_info
*, struct page
*);
46 struct percpu_counter bdi_stat
[NR_BDI_STAT_ITEMS
];
49 int bdi_init(struct backing_dev_info
*bdi
);
50 void bdi_destroy(struct backing_dev_info
*bdi
);
52 static inline void __add_bdi_stat(struct backing_dev_info
*bdi
,
53 enum bdi_stat_item item
, s64 amount
)
55 __percpu_counter_add(&bdi
->bdi_stat
[item
], amount
, BDI_STAT_BATCH
);
58 static inline void __inc_bdi_stat(struct backing_dev_info
*bdi
,
59 enum bdi_stat_item item
)
61 __add_bdi_stat(bdi
, item
, 1);
64 static inline void inc_bdi_stat(struct backing_dev_info
*bdi
,
65 enum bdi_stat_item item
)
69 local_irq_save(flags
);
70 __inc_bdi_stat(bdi
, item
);
71 local_irq_restore(flags
);
74 static inline void __dec_bdi_stat(struct backing_dev_info
*bdi
,
75 enum bdi_stat_item item
)
77 __add_bdi_stat(bdi
, item
, -1);
80 static inline void dec_bdi_stat(struct backing_dev_info
*bdi
,
81 enum bdi_stat_item item
)
85 local_irq_save(flags
);
86 __dec_bdi_stat(bdi
, item
);
87 local_irq_restore(flags
);
90 static inline s64
bdi_stat(struct backing_dev_info
*bdi
,
91 enum bdi_stat_item item
)
93 return percpu_counter_read_positive(&bdi
->bdi_stat
[item
]);
96 static inline s64
__bdi_stat_sum(struct backing_dev_info
*bdi
,
97 enum bdi_stat_item item
)
99 return percpu_counter_sum_positive(&bdi
->bdi_stat
[item
]);
102 static inline s64
bdi_stat_sum(struct backing_dev_info
*bdi
,
103 enum bdi_stat_item item
)
108 local_irq_save(flags
);
109 sum
= __bdi_stat_sum(bdi
, item
);
110 local_irq_restore(flags
);
116 * maximal error of a stat counter.
118 static inline unsigned long bdi_stat_error(struct backing_dev_info
*bdi
)
121 return nr_cpu_ids
* BDI_STAT_BATCH
;
128 * Flags in backing_dev_info::capability
129 * - The first two flags control whether dirty pages will contribute to the
130 * VM's accounting and whether writepages() should be called for dirty pages
131 * (something that would not, for example, be appropriate for ramfs)
132 * - These flags let !MMU mmap() govern direct device mapping vs immediate
133 * copying more easily for MAP_PRIVATE, especially for ROM filesystems
135 #define BDI_CAP_NO_ACCT_DIRTY 0x00000001 /* Dirty pages shouldn't contribute to accounting */
136 #define BDI_CAP_NO_WRITEBACK 0x00000002 /* Don't write pages back */
137 #define BDI_CAP_MAP_COPY 0x00000004 /* Copy can be mapped (MAP_PRIVATE) */
138 #define BDI_CAP_MAP_DIRECT 0x00000008 /* Can be mapped directly (MAP_SHARED) */
139 #define BDI_CAP_READ_MAP 0x00000010 /* Can be mapped for reading */
140 #define BDI_CAP_WRITE_MAP 0x00000020 /* Can be mapped for writing */
141 #define BDI_CAP_EXEC_MAP 0x00000040 /* Can be mapped for execution */
142 #define BDI_CAP_VMFLAGS \
143 (BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP)
145 #if defined(VM_MAYREAD) && \
146 (BDI_CAP_READ_MAP != VM_MAYREAD || \
147 BDI_CAP_WRITE_MAP != VM_MAYWRITE || \
148 BDI_CAP_EXEC_MAP != VM_MAYEXEC)
149 #error please change backing_dev_info::capabilities flags
152 extern struct backing_dev_info default_backing_dev_info
;
153 void default_unplug_io_fn(struct backing_dev_info
*bdi
, struct page
*page
);
155 int writeback_acquire(struct backing_dev_info
*bdi
);
156 int writeback_in_progress(struct backing_dev_info
*bdi
);
157 void writeback_release(struct backing_dev_info
*bdi
);
159 static inline int bdi_congested(struct backing_dev_info
*bdi
, int bdi_bits
)
161 if (bdi
->congested_fn
)
162 return bdi
->congested_fn(bdi
->congested_data
, bdi_bits
);
163 return (bdi
->state
& bdi_bits
);
166 static inline int bdi_read_congested(struct backing_dev_info
*bdi
)
168 return bdi_congested(bdi
, 1 << BDI_read_congested
);
171 static inline int bdi_write_congested(struct backing_dev_info
*bdi
)
173 return bdi_congested(bdi
, 1 << BDI_write_congested
);
176 static inline int bdi_rw_congested(struct backing_dev_info
*bdi
)
178 return bdi_congested(bdi
, (1 << BDI_read_congested
)|
179 (1 << BDI_write_congested
));
182 void clear_bdi_congested(struct backing_dev_info
*bdi
, int rw
);
183 void set_bdi_congested(struct backing_dev_info
*bdi
, int rw
);
184 long congestion_wait(int rw
, long timeout
);
186 #define bdi_cap_writeback_dirty(bdi) \
187 (!((bdi)->capabilities & BDI_CAP_NO_WRITEBACK))
189 #define bdi_cap_account_dirty(bdi) \
190 (!((bdi)->capabilities & BDI_CAP_NO_ACCT_DIRTY))
192 #define mapping_cap_writeback_dirty(mapping) \
193 bdi_cap_writeback_dirty((mapping)->backing_dev_info)
195 #define mapping_cap_account_dirty(mapping) \
196 bdi_cap_account_dirty((mapping)->backing_dev_info)
199 #endif /* _LINUX_BACKING_DEV_H */