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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 */
};

struct backing_dev_info {
        unsigned long ra_pages; /* max readahead in PAGE_CACHE_SIZE units */
        unsigned long state;    /* Always use atomic bitops on this */
        int memory_backed;      /* Cannot clean pages with writepage */
};

extern struct backing_dev_info default_backing_dev_info;

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_read_congested(struct backing_dev_info *bdi)
{
        return test_bit(BDI_read_congested, &bdi->state);
}

static inline int bdi_write_congested(struct backing_dev_info *bdi)
{
        return test_bit(BDI_write_congested, &bdi->state);
}

#endif          /* _LINUX_BACKING_DEV_H */