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 <asm/atomic.h> 12 13 /* 14 * Bits in backing_dev_info.state 15 */ 16 enum bdi_state { 17 BDI_pdflush, /* A pdflush thread is working this device */ 18 BDI_write_congested, /* The write queue is getting full */ 19 BDI_read_congested, /* The read queue is getting full */ 20 BDI_unused, /* Available bits start here */ 21 }; 22 23 typedef int (congested_fn)(void *, int); 24 25 struct backing_dev_info { 26 unsigned long ra_pages; /* max readahead in PAGE_CACHE_SIZE units */ 27 unsigned long state; /* Always use atomic bitops on this */ 28 unsigned int capabilities; /* Device capabilities */ 29 congested_fn *congested_fn; /* Function pointer if device is md/dm */ 30 void *congested_data; /* Pointer to aux data for congested func */ 31 void (*unplug_io_fn)(struct backing_dev_info *, struct page *); 32 void *unplug_io_data; 33 }; 34 35 36 /* 37 * Flags in backing_dev_info::capability 38 * - The first two flags control whether dirty pages will contribute to the 39 * VM's accounting and whether writepages() should be called for dirty pages 40 * (something that would not, for example, be appropriate for ramfs) 41 * - These flags let !MMU mmap() govern direct device mapping vs immediate 42 * copying more easily for MAP_PRIVATE, especially for ROM filesystems 43 */ 44 #define BDI_CAP_NO_ACCT_DIRTY 0x00000001 /* Dirty pages shouldn't contribute to accounting */ 45 #define BDI_CAP_NO_WRITEBACK 0x00000002 /* Don't write pages back */ 46 #define BDI_CAP_MAP_COPY 0x00000004 /* Copy can be mapped (MAP_PRIVATE) */ 47 #define BDI_CAP_MAP_DIRECT 0x00000008 /* Can be mapped directly (MAP_SHARED) */ 48 #define BDI_CAP_READ_MAP 0x00000010 /* Can be mapped for reading */ 49 #define BDI_CAP_WRITE_MAP 0x00000020 /* Can be mapped for writing */ 50 #define BDI_CAP_EXEC_MAP 0x00000040 /* Can be mapped for execution */ 51 #define BDI_CAP_VMFLAGS \ 52 (BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP) 53 54 #if defined(VM_MAYREAD) && \ 55 (BDI_CAP_READ_MAP != VM_MAYREAD || \ 56 BDI_CAP_WRITE_MAP != VM_MAYWRITE || \ 57 BDI_CAP_EXEC_MAP != VM_MAYEXEC) 58 #error please change backing_dev_info::capabilities flags 59 #endif 60 61 extern struct backing_dev_info default_backing_dev_info; 62 void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page); 63 64 int writeback_acquire(struct backing_dev_info *bdi); 65 int writeback_in_progress(struct backing_dev_info *bdi); 66 void writeback_release(struct backing_dev_info *bdi); 67 68 static inline int bdi_congested(struct backing_dev_info *bdi, int bdi_bits) 69 { 70 if (bdi->congested_fn) 71 return bdi->congested_fn(bdi->congested_data, bdi_bits); 72 return (bdi->state & bdi_bits); 73 } 74 75 static inline int bdi_read_congested(struct backing_dev_info *bdi) 76 { 77 return bdi_congested(bdi, 1 << BDI_read_congested); 78 } 79 80 static inline int bdi_write_congested(struct backing_dev_info *bdi) 81 { 82 return bdi_congested(bdi, 1 << BDI_write_congested); 83 } 84 85 static inline int bdi_rw_congested(struct backing_dev_info *bdi) 86 { 87 return bdi_congested(bdi, (1 << BDI_read_congested)| 88 (1 << BDI_write_congested)); 89 } 90 91 #define bdi_cap_writeback_dirty(bdi) \ 92 (!((bdi)->capabilities & BDI_CAP_NO_WRITEBACK)) 93 94 #define bdi_cap_account_dirty(bdi) \ 95 (!((bdi)->capabilities & BDI_CAP_NO_ACCT_DIRTY)) 96 97 #define mapping_cap_writeback_dirty(mapping) \ 98 bdi_cap_writeback_dirty((mapping)->backing_dev_info) 99 100 #define mapping_cap_account_dirty(mapping) \ 101 bdi_cap_account_dirty((mapping)->backing_dev_info) 102 103 104 #endif /* _LINUX_BACKING_DEV_H */ 105
