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);
34 #define BDI_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))
36 struct backing_dev_info {
37 unsigned long ra_pages; /* max readahead in PAGE_CACHE_SIZE units */
38 unsigned long state; /* Always use atomic bitops on this */
39 unsigned int capabilities; /* Device capabilities */
40 congested_fn *congested_fn; /* Function pointer if device is md/dm */
41 void *congested_data; /* Pointer to aux data for congested func */
42 void (*unplug_io_fn)(struct backing_dev_info *, struct page *);
45 struct percpu_counter bdi_stat[NR_BDI_STAT_ITEMS];
48 int bdi_init(struct backing_dev_info *bdi);
49 void bdi_destroy(struct backing_dev_info *bdi);
51 static inline void __add_bdi_stat(struct backing_dev_info *bdi,
52 enum bdi_stat_item item, s64 amount)
54 __percpu_counter_add(&bdi->bdi_stat[item], amount, BDI_STAT_BATCH);
57 static inline void __inc_bdi_stat(struct backing_dev_info *bdi,
58 enum bdi_stat_item item)
60 __add_bdi_stat(bdi, item, 1);
63 static inline void inc_bdi_stat(struct backing_dev_info *bdi,
64 enum bdi_stat_item item)
68 local_irq_save(flags);
69 __inc_bdi_stat(bdi, item);
70 local_irq_restore(flags);
73 static inline void __dec_bdi_stat(struct backing_dev_info *bdi,
74 enum bdi_stat_item item)
76 __add_bdi_stat(bdi, item, -1);
79 static inline void dec_bdi_stat(struct backing_dev_info *bdi,
80 enum bdi_stat_item item)
84 local_irq_save(flags);
85 __dec_bdi_stat(bdi, item);
86 local_irq_restore(flags);
89 static inline s64 bdi_stat(struct backing_dev_info *bdi,
90 enum bdi_stat_item item)
92 return percpu_counter_read_positive(&bdi->bdi_stat[item]);
95 static inline s64 __bdi_stat_sum(struct backing_dev_info *bdi,
96 enum bdi_stat_item item)
98 return percpu_counter_sum_positive(&bdi->bdi_stat[item]);
101 static inline s64 bdi_stat_sum(struct backing_dev_info *bdi,
102 enum bdi_stat_item item)
107 local_irq_save(flags);
108 sum = __bdi_stat_sum(bdi, item);
109 local_irq_restore(flags);
115 * maximal error of a stat counter.
117 static inline unsigned long bdi_stat_error(struct backing_dev_info *bdi)
120 return nr_cpu_ids * BDI_STAT_BATCH;
127 * Flags in backing_dev_info::capability
128 * - The first two flags control whether dirty pages will contribute to the
129 * VM's accounting and whether writepages() should be called for dirty pages
130 * (something that would not, for example, be appropriate for ramfs)
131 * - These flags let !MMU mmap() govern direct device mapping vs immediate
132 * copying more easily for MAP_PRIVATE, especially for ROM filesystems
134 #define BDI_CAP_NO_ACCT_DIRTY 0x00000001 /* Dirty pages shouldn't contribute to accounting */
135 #define BDI_CAP_NO_WRITEBACK 0x00000002 /* Don't write pages back */
136 #define BDI_CAP_MAP_COPY 0x00000004 /* Copy can be mapped (MAP_PRIVATE) */
137 #define BDI_CAP_MAP_DIRECT 0x00000008 /* Can be mapped directly (MAP_SHARED) */
138 #define BDI_CAP_READ_MAP 0x00000010 /* Can be mapped for reading */
139 #define BDI_CAP_WRITE_MAP 0x00000020 /* Can be mapped for writing */
140 #define BDI_CAP_EXEC_MAP 0x00000040 /* Can be mapped for execution */
141 #define BDI_CAP_VMFLAGS \
142 (BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP)
144 #if defined(VM_MAYREAD) && \
145 (BDI_CAP_READ_MAP != VM_MAYREAD || \
146 BDI_CAP_WRITE_MAP != VM_MAYWRITE || \
147 BDI_CAP_EXEC_MAP != VM_MAYEXEC)
148 #error please change backing_dev_info::capabilities flags
151 extern struct backing_dev_info default_backing_dev_info;
152 void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page);
154 int writeback_acquire(struct backing_dev_info *bdi);
155 int writeback_in_progress(struct backing_dev_info *bdi);
156 void writeback_release(struct backing_dev_info *bdi);
158 static inline int bdi_congested(struct backing_dev_info *bdi, int bdi_bits)
160 if (bdi->congested_fn)
161 return bdi->congested_fn(bdi->congested_data, bdi_bits);
162 return (bdi->state & bdi_bits);
165 static inline int bdi_read_congested(struct backing_dev_info *bdi)
167 return bdi_congested(bdi, 1 << BDI_read_congested);
170 static inline int bdi_write_congested(struct backing_dev_info *bdi)
172 return bdi_congested(bdi, 1 << BDI_write_congested);
175 static inline int bdi_rw_congested(struct backing_dev_info *bdi)
177 return bdi_congested(bdi, (1 << BDI_read_congested)|
178 (1 << BDI_write_congested));
181 void clear_bdi_congested(struct backing_dev_info *bdi, int rw);
182 void set_bdi_congested(struct backing_dev_info *bdi, int rw);
183 long congestion_wait(int rw, long timeout);
185 #define bdi_cap_writeback_dirty(bdi) \
186 (!((bdi)->capabilities & BDI_CAP_NO_WRITEBACK))
188 #define bdi_cap_account_dirty(bdi) \
189 (!((bdi)->capabilities & BDI_CAP_NO_ACCT_DIRTY))
191 #define mapping_cap_writeback_dirty(mapping) \
192 bdi_cap_writeback_dirty((mapping)->backing_dev_info)
194 #define mapping_cap_account_dirty(mapping) \
195 bdi_cap_account_dirty((mapping)->backing_dev_info)
198 #endif /* _LINUX_BACKING_DEV_H */