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