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>
22 * Bits in backing_dev_info.state
25 BDI_pdflush, /* A pdflush thread is working this device */
26 BDI_write_congested, /* The write queue is getting full */
27 BDI_read_congested, /* The read queue is getting full */
28 BDI_unused, /* Available bits start here */
31 typedef int (congested_fn)(void *, int);
39 #define BDI_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))
41 struct backing_dev_info {
42 unsigned long ra_pages; /* max readahead in PAGE_CACHE_SIZE units */
43 unsigned long state; /* Always use atomic bitops on this */
44 unsigned int capabilities; /* Device capabilities */
45 congested_fn *congested_fn; /* Function pointer if device is md/dm */
46 void *congested_data; /* Pointer to aux data for congested func */
47 void (*unplug_io_fn)(struct backing_dev_info *, struct page *);
50 struct percpu_counter bdi_stat[NR_BDI_STAT_ITEMS];
52 struct prop_local_percpu completions;
55 unsigned int min_ratio;
56 unsigned int max_ratio, max_prop_frac;
60 #ifdef CONFIG_DEBUG_FS
61 struct dentry *debug_dir;
62 struct dentry *debug_stats;
66 int bdi_init(struct backing_dev_info *bdi);
67 void bdi_destroy(struct backing_dev_info *bdi);
69 int bdi_register(struct backing_dev_info *bdi, struct device *parent,
70 const char *fmt, ...);
71 int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev);
72 void bdi_unregister(struct backing_dev_info *bdi);
74 static inline void __add_bdi_stat(struct backing_dev_info *bdi,
75 enum bdi_stat_item item, s64 amount)
77 __percpu_counter_add(&bdi->bdi_stat[item], amount, BDI_STAT_BATCH);
80 static inline void __inc_bdi_stat(struct backing_dev_info *bdi,
81 enum bdi_stat_item item)
83 __add_bdi_stat(bdi, item, 1);
86 static inline void inc_bdi_stat(struct backing_dev_info *bdi,
87 enum bdi_stat_item item)
91 local_irq_save(flags);
92 __inc_bdi_stat(bdi, item);
93 local_irq_restore(flags);
96 static inline void __dec_bdi_stat(struct backing_dev_info *bdi,
97 enum bdi_stat_item item)
99 __add_bdi_stat(bdi, item, -1);
102 static inline void dec_bdi_stat(struct backing_dev_info *bdi,
103 enum bdi_stat_item item)
107 local_irq_save(flags);
108 __dec_bdi_stat(bdi, item);
109 local_irq_restore(flags);
112 static inline s64 bdi_stat(struct backing_dev_info *bdi,
113 enum bdi_stat_item item)
115 return percpu_counter_read_positive(&bdi->bdi_stat[item]);
118 static inline s64 __bdi_stat_sum(struct backing_dev_info *bdi,
119 enum bdi_stat_item item)
121 return percpu_counter_sum_positive(&bdi->bdi_stat[item]);
124 static inline s64 bdi_stat_sum(struct backing_dev_info *bdi,
125 enum bdi_stat_item item)
130 local_irq_save(flags);
131 sum = __bdi_stat_sum(bdi, item);
132 local_irq_restore(flags);
138 * maximal error of a stat counter.
140 static inline unsigned long bdi_stat_error(struct backing_dev_info *bdi)
143 return nr_cpu_ids * BDI_STAT_BATCH;
149 int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio);
150 int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio);
153 * Flags in backing_dev_info::capability
154 * - The first two flags control whether dirty pages will contribute to the
155 * VM's accounting and whether writepages() should be called for dirty pages
156 * (something that would not, for example, be appropriate for ramfs)
157 * - These flags let !MMU mmap() govern direct device mapping vs immediate
158 * copying more easily for MAP_PRIVATE, especially for ROM filesystems
160 #define BDI_CAP_NO_ACCT_DIRTY 0x00000001 /* Dirty pages shouldn't contribute to accounting */
161 #define BDI_CAP_NO_WRITEBACK 0x00000002 /* Don't write pages back */
162 #define BDI_CAP_MAP_COPY 0x00000004 /* Copy can be mapped (MAP_PRIVATE) */
163 #define BDI_CAP_MAP_DIRECT 0x00000008 /* Can be mapped directly (MAP_SHARED) */
164 #define BDI_CAP_READ_MAP 0x00000010 /* Can be mapped for reading */
165 #define BDI_CAP_WRITE_MAP 0x00000020 /* Can be mapped for writing */
166 #define BDI_CAP_EXEC_MAP 0x00000040 /* Can be mapped for execution */
167 #define BDI_CAP_VMFLAGS \
168 (BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP)
170 #if defined(VM_MAYREAD) && \
171 (BDI_CAP_READ_MAP != VM_MAYREAD || \
172 BDI_CAP_WRITE_MAP != VM_MAYWRITE || \
173 BDI_CAP_EXEC_MAP != VM_MAYEXEC)
174 #error please change backing_dev_info::capabilities flags
177 extern struct backing_dev_info default_backing_dev_info;
178 void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page);
180 int writeback_in_progress(struct backing_dev_info *bdi);
182 static inline int bdi_congested(struct backing_dev_info *bdi, int bdi_bits)
184 if (bdi->congested_fn)
185 return bdi->congested_fn(bdi->congested_data, bdi_bits);
186 return (bdi->state & bdi_bits);
189 static inline int bdi_read_congested(struct backing_dev_info *bdi)
191 return bdi_congested(bdi, 1 << BDI_read_congested);
194 static inline int bdi_write_congested(struct backing_dev_info *bdi)
196 return bdi_congested(bdi, 1 << BDI_write_congested);
199 static inline int bdi_rw_congested(struct backing_dev_info *bdi)
201 return bdi_congested(bdi, (1 << BDI_read_congested)|
202 (1 << BDI_write_congested));
205 void clear_bdi_congested(struct backing_dev_info *bdi, int rw);
206 void set_bdi_congested(struct backing_dev_info *bdi, int rw);
207 long congestion_wait(int rw, long timeout);
209 #define bdi_cap_writeback_dirty(bdi) \
210 (!((bdi)->capabilities & BDI_CAP_NO_WRITEBACK))
212 #define bdi_cap_account_dirty(bdi) \
213 (!((bdi)->capabilities & BDI_CAP_NO_ACCT_DIRTY))
215 #define mapping_cap_writeback_dirty(mapping) \
216 bdi_cap_writeback_dirty((mapping)->backing_dev_info)
218 #define mapping_cap_account_dirty(mapping) \
219 bdi_cap_account_dirty((mapping)->backing_dev_info)
222 #endif /* _LINUX_BACKING_DEV_H */