source: svn/trunk/newcon3bcm2_21bu/toolchain/mipsel-linux-uclibc/include/linux/backing-dev.h @ 2

/*
 * 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


/*
 * 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 */