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/* * include/linux/backing-dev.h * * low-level device information and state which is propagated up through * to high-level code. */ #ifndef _LINUX_BACKING_DEV_H #define _LINUX_BACKING_DEV_H #include <asm/atomic.h> /* * Bits in backing_dev_info.state */ enum bdi_state { BDI_pdflush, /* A pdflush thread is working this device */ BDI_write_congested, /* The write queue is getting full */ BDI_read_congested, /* The read queue is getting full */ BDI_unused, /* Available bits start here */ }; typedef int (congested_fn)(void *, int); struct backing_dev_info { unsigned long ra_pages; /* max readahead in PAGE_CACHE_SIZE units */ unsigned long state; /* Always use atomic bitops on this */ unsigned int capabilities; /* Device capabilities */ congested_fn *congested_fn; /* Function pointer if device is md/dm */ void *congested_data; /* Pointer to aux data for congested func */ void (*unplug_io_fn)(struct backing_dev_info *, struct page *); void *unplug_io_data; }; /* * Flags in backing_dev_info::capability * - The first two flags control whether dirty pages will contribute to the * VM's accounting and whether writepages() should be called for dirty pages * (something that would not, for example, be appropriate for ramfs) * - These flags let !MMU mmap() govern direct device mapping vs immediate * copying more easily for MAP_PRIVATE, especially for ROM filesystems */ #define BDI_CAP_NO_ACCT_DIRTY 0x00000001 /* Dirty pages shouldn't contribute to accounting */ #define BDI_CAP_NO_WRITEBACK 0x00000002 /* Don't write pages back */ #define BDI_CAP_MAP_COPY 0x00000004 /* Copy can be mapped (MAP_PRIVATE) */ #define BDI_CAP_MAP_DIRECT 0x00000008 /* Can be mapped directly (MAP_SHARED) */ #define BDI_CAP_READ_MAP 0x00000010 /* Can be mapped for reading */ #define BDI_CAP_WRITE_MAP 0x00000020 /* Can be mapped for writing */ #define BDI_CAP_EXEC_MAP 0x00000040 /* Can be mapped for execution */ #define BDI_CAP_VMFLAGS \ (BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP) #if defined(VM_MAYREAD) && \ (BDI_CAP_READ_MAP != VM_MAYREAD || \ BDI_CAP_WRITE_MAP != VM_MAYWRITE || \ BDI_CAP_EXEC_MAP != VM_MAYEXEC) #error please change backing_dev_info::capabilities flags #endif extern struct backing_dev_info default_backing_dev_info; void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page); int writeback_acquire(struct backing_dev_info *bdi); int writeback_in_progress(struct backing_dev_info *bdi); void writeback_release(struct backing_dev_info *bdi); static inline int bdi_congested(struct backing_dev_info *bdi, int bdi_bits) { if (bdi->congested_fn) return bdi->congested_fn(bdi->congested_data, bdi_bits); return (bdi->state & bdi_bits); } static inline int bdi_read_congested(struct backing_dev_info *bdi) { return bdi_congested(bdi, 1 << BDI_read_congested); } static inline int bdi_write_congested(struct backing_dev_info *bdi) { return bdi_congested(bdi, 1 << BDI_write_congested); } static inline int bdi_rw_congested(struct backing_dev_info *bdi) { return bdi_congested(bdi, (1 << BDI_read_congested)| (1 << BDI_write_congested)); } #define bdi_cap_writeback_dirty(bdi) \ (!((bdi)->capabilities & BDI_CAP_NO_WRITEBACK)) #define bdi_cap_account_dirty(bdi) \ (!((bdi)->capabilities & BDI_CAP_NO_ACCT_DIRTY)) #define mapping_cap_writeback_dirty(mapping) \ bdi_cap_writeback_dirty((mapping)->backing_dev_info) #define mapping_cap_account_dirty(mapping) \ bdi_cap_account_dirty((mapping)->backing_dev_info) #endif /* _LINUX_BACKING_DEV_H */