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 <linux/proportions.h>
14 #include <linux/kernel.h>
15 #include <asm/atomic.h>
21 * Bits in backing_dev_info.state
24 BDI_pdflush, /* A pdflush thread is working this device */
25 BDI_write_congested, /* The write queue is getting full */
26 BDI_read_congested, /* The read queue is getting full */
27 BDI_unused, /* Available bits start here */
30 typedef int (congested_fn)(void *, int);
38 #define BDI_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))
40 struct backing_dev_info {
41 unsigned long ra_pages; /* max readahead in PAGE_CACHE_SIZE units */
42 unsigned long state; /* Always use atomic bitops on this */
43 unsigned int capabilities; /* Device capabilities */
44 congested_fn *congested_fn; /* Function pointer if device is md/dm */
45 void *congested_data; /* Pointer to aux data for congested func */
46 void (*unplug_io_fn)(struct backing_dev_info *, struct page *);
49 struct percpu_counter bdi_stat[NR_BDI_STAT_ITEMS];
51 struct prop_local_percpu completions;
54 unsigned int min_ratio;
59 int bdi_init(struct backing_dev_info *bdi);
60 void bdi_destroy(struct backing_dev_info *bdi);
62 int bdi_register(struct backing_dev_info *bdi, struct device *parent,
63 const char *fmt, ...);
64 int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev);
65 void bdi_unregister(struct backing_dev_info *bdi);
67 static inline void __add_bdi_stat(struct backing_dev_info *bdi,
68 enum bdi_stat_item item, s64 amount)
70 __percpu_counter_add(&bdi->bdi_stat[item], amount, BDI_STAT_BATCH);
73 static inline void __inc_bdi_stat(struct backing_dev_info *bdi,
74 enum bdi_stat_item item)
76 __add_bdi_stat(bdi, item, 1);
79 static inline void inc_bdi_stat(struct backing_dev_info *bdi,
80 enum bdi_stat_item item)
84 local_irq_save(flags);
85 __inc_bdi_stat(bdi, item);
86 local_irq_restore(flags);
89 static inline void __dec_bdi_stat(struct backing_dev_info *bdi,
90 enum bdi_stat_item item)
92 __add_bdi_stat(bdi, item, -1);
95 static inline void dec_bdi_stat(struct backing_dev_info *bdi,
96 enum bdi_stat_item item)
100 local_irq_save(flags);
101 __dec_bdi_stat(bdi, item);
102 local_irq_restore(flags);
105 static inline s64 bdi_stat(struct backing_dev_info *bdi,
106 enum bdi_stat_item item)
108 return percpu_counter_read_positive(&bdi->bdi_stat[item]);
111 static inline s64 __bdi_stat_sum(struct backing_dev_info *bdi,
112 enum bdi_stat_item item)
114 return percpu_counter_sum_positive(&bdi->bdi_stat[item]);
117 static inline s64 bdi_stat_sum(struct backing_dev_info *bdi,
118 enum bdi_stat_item item)
123 local_irq_save(flags);
124 sum = __bdi_stat_sum(bdi, item);
125 local_irq_restore(flags);
131 * maximal error of a stat counter.
133 static inline unsigned long bdi_stat_error(struct backing_dev_info *bdi)
136 return nr_cpu_ids * BDI_STAT_BATCH;
142 int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio);
145 * Flags in backing_dev_info::capability
146 * - The first two flags control whether dirty pages will contribute to the
147 * VM's accounting and whether writepages() should be called for dirty pages
148 * (something that would not, for example, be appropriate for ramfs)
149 * - These flags let !MMU mmap() govern direct device mapping vs immediate
150 * copying more easily for MAP_PRIVATE, especially for ROM filesystems
152 #define BDI_CAP_NO_ACCT_DIRTY 0x00000001 /* Dirty pages shouldn't contribute to accounting */
153 #define BDI_CAP_NO_WRITEBACK 0x00000002 /* Don't write pages back */
154 #define BDI_CAP_MAP_COPY 0x00000004 /* Copy can be mapped (MAP_PRIVATE) */
155 #define BDI_CAP_MAP_DIRECT 0x00000008 /* Can be mapped directly (MAP_SHARED) */
156 #define BDI_CAP_READ_MAP 0x00000010 /* Can be mapped for reading */
157 #define BDI_CAP_WRITE_MAP 0x00000020 /* Can be mapped for writing */
158 #define BDI_CAP_EXEC_MAP 0x00000040 /* Can be mapped for execution */
159 #define BDI_CAP_VMFLAGS \
160 (BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP)
162 #if defined(VM_MAYREAD) && \
163 (BDI_CAP_READ_MAP != VM_MAYREAD || \
164 BDI_CAP_WRITE_MAP != VM_MAYWRITE || \
165 BDI_CAP_EXEC_MAP != VM_MAYEXEC)
166 #error please change backing_dev_info::capabilities flags
169 extern struct backing_dev_info default_backing_dev_info;
170 void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page);
172 int writeback_in_progress(struct backing_dev_info *bdi);
174 static inline int bdi_congested(struct backing_dev_info *bdi, int bdi_bits)
176 if (bdi->congested_fn)
177 return bdi->congested_fn(bdi->congested_data, bdi_bits);
178 return (bdi->state & bdi_bits);
181 static inline int bdi_read_congested(struct backing_dev_info *bdi)
183 return bdi_congested(bdi, 1 << BDI_read_congested);
186 static inline int bdi_write_congested(struct backing_dev_info *bdi)
188 return bdi_congested(bdi, 1 << BDI_write_congested);
191 static inline int bdi_rw_congested(struct backing_dev_info *bdi)
193 return bdi_congested(bdi, (1 << BDI_read_congested)|
194 (1 << BDI_write_congested));
197 void clear_bdi_congested(struct backing_dev_info *bdi, int rw);
198 void set_bdi_congested(struct backing_dev_info *bdi, int rw);
199 long congestion_wait(int rw, long timeout);
201 #define bdi_cap_writeback_dirty(bdi) \
202 (!((bdi)->capabilities & BDI_CAP_NO_WRITEBACK))
204 #define bdi_cap_account_dirty(bdi) \
205 (!((bdi)->capabilities & BDI_CAP_NO_ACCT_DIRTY))
207 #define mapping_cap_writeback_dirty(mapping) \
208 bdi_cap_writeback_dirty((mapping)->backing_dev_info)
210 #define mapping_cap_account_dirty(mapping) \
211 bdi_cap_account_dirty((mapping)->backing_dev_info)
214 #endif /* _LINUX_BACKING_DEV_H */