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 16 struct page; 17 18 /* 19 * Bits in backing_dev_info.state 20 */ 21 enum 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 28 typedef int (congested_fn)(void *, int); 29 30 enum 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 38 struct 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 53 int bdi_init(struct backing_dev_info *bdi); 54 void bdi_destroy(struct backing_dev_info *bdi); 55 56 static 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 62 static 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 68 static 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 78 static 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 84 static 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 94 static 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 } 99 100 static 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 } 105 106 static 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 */ 122 static 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 155 156 extern struct backing_dev_info default_backing_dev_info; 157 void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page); 158 159 int writeback_acquire(struct backing_dev_info *bdi); 160 int writeback_in_progress(struct backing_dev_info *bdi); 161 void writeback_release(struct backing_dev_info *bdi); 162 163 static 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 } 169 170 static inline int bdi_read_congested(struct backing_dev_info *bdi) 171 { 172 return bdi_congested(bdi, 1 << BDI_read_congested); 173 } 174 175 static inline int bdi_write_congested(struct backing_dev_info *bdi) 176 { 177 return bdi_congested(bdi, 1 << BDI_write_congested); 178 } 179 180 static 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 } 185 186 void clear_bdi_congested(struct backing_dev_info *bdi, int rw); 187 void set_bdi_congested(struct backing_dev_info *bdi, int rw); 188 long 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 */ 204