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422 giacomo 1
/*
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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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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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        int memory_backed;      /* Cannot clean pages with writepage */
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};
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extern struct backing_dev_info default_backing_dev_info;
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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_read_congested(struct backing_dev_info *bdi)
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{
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        return test_bit(BDI_read_congested, &bdi->state);
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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 test_bit(BDI_write_congested, &bdi->state);
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}
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#endif          /* _LINUX_BACKING_DEV_H */