/*
 * 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 <linux/percpu_counter.h>
#include <linux/log2.h>
#include <linux/proportions.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/sched.h>
#include <linux/writeback.h>
#include <asm/atomic.h>

struct page;
struct device;
struct dentry;

/*
 * Bits in backing_dev_info.state
 */
enum bdi_state {
        BDI_pending,            /* On its way to being activated */
        BDI_wb_alloc,           /* Default embedded wb allocated */
        BDI_async_congested,    /* The async (write) queue is getting full */
        BDI_sync_congested,     /* The sync queue is getting full */
        BDI_registered,         /* bdi_register() was done */
        BDI_unused,             /* Available bits start here */
};

typedef int (congested_fn)(void *, int);

enum bdi_stat_item {
        BDI_RECLAIMABLE,
        BDI_WRITEBACK,
        NR_BDI_STAT_ITEMS
};

#define BDI_STAT_BATCH (8*(1+ilog2(nr_cpu_ids)))

struct bdi_writeback {
        struct list_head list;                  /* hangs off the bdi */

        struct backing_dev_info *bdi;           /* our parent bdi */
        unsigned int nr;

        unsigned long last_old_flush;           /* last old data flush */

        struct task_struct      *task;          /* writeback task */
        struct list_head        b_dirty;        /* dirty inodes */
        struct list_head        b_io;           /* parked for writeback */
        struct list_head        b_more_io;      /* parked for more writeback */
};

struct backing_dev_info {
        struct list_head bdi_list;
        struct rcu_head rcu_head;
        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;

        char *name;

        struct percpu_counter bdi_stat[NR_BDI_STAT_ITEMS];

        struct prop_local_percpu completions;
        int dirty_exceeded;

        unsigned int min_ratio;
        unsigned int max_ratio, max_prop_frac;

        struct bdi_writeback wb;  /* default writeback info for this bdi */
        spinlock_t wb_lock;       /* protects update side of wb_list */
        struct list_head wb_list; /* the flusher threads hanging off this bdi */
        unsigned long wb_mask;    /* bitmask of registered tasks */
        unsigned int wb_cnt;      /* number of registered tasks */

        struct list_head work_list;

        struct device *dev;

#ifdef CONFIG_DEBUG_FS
        struct dentry *debug_dir;
        struct dentry *debug_stats;
#endif
};

int bdi_init(struct backing_dev_info *bdi);
void bdi_destroy(struct backing_dev_info *bdi);

int bdi_register(struct backing_dev_info *bdi, struct device *parent,
                const char *fmt, ...);
int bdi_register_dev(struct backing_dev_info *bdi, dev_t dev);
void bdi_unregister(struct backing_dev_info *bdi);
void bdi_start_writeback(struct backing_dev_info *bdi, struct super_block *sb,
                                long nr_pages);
int bdi_writeback_task(struct bdi_writeback *wb);
int bdi_has_dirty_io(struct backing_dev_info *bdi);

extern spinlock_t bdi_lock;
extern struct list_head bdi_list;

static inline int wb_has_dirty_io(struct bdi_writeback *wb)
{
        return !list_empty(&wb->b_dirty) ||
               !list_empty(&wb->b_io) ||
               !list_empty(&wb->b_more_io);
}

static inline void __add_bdi_stat(struct backing_dev_info *bdi,
                enum bdi_stat_item item, s64 amount)
{
        __percpu_counter_add(&bdi->bdi_stat[item], amount, BDI_STAT_BATCH);
}

static inline void __inc_bdi_stat(struct backing_dev_info *bdi,
                enum bdi_stat_item item)
{
        __add_bdi_stat(bdi, item, 1);
}

static inline void inc_bdi_stat(struct backing_dev_info *bdi,
                enum bdi_stat_item item)
{
        unsigned long flags;

        local_irq_save(flags);
        __inc_bdi_stat(bdi, item);
        local_irq_restore(flags);
}

static inline void __dec_bdi_stat(struct backing_dev_info *bdi,
                enum bdi_stat_item item)
{
        __add_bdi_stat(bdi, item, -1);
}

static inline void dec_bdi_stat(struct backing_dev_info *bdi,
                enum bdi_stat_item item)
{
        unsigned long flags;

        local_irq_save(flags);
        __dec_bdi_stat(bdi, item);
        local_irq_restore(flags);
}

static inline s64 bdi_stat(struct backing_dev_info *bdi,
                enum bdi_stat_item item)
{
        return percpu_counter_read_positive(&bdi->bdi_stat[item]);
}

static inline s64 __bdi_stat_sum(struct backing_dev_info *bdi,
                enum bdi_stat_item item)
{
        return percpu_counter_sum_positive(&bdi->bdi_stat[item]);
}

static inline s64 bdi_stat_sum(struct backing_dev_info *bdi,
                enum bdi_stat_item item)
{
        s64 sum;
        unsigned long flags;

        local_irq_save(flags);
        sum = __bdi_stat_sum(bdi, item);
        local_irq_restore(flags);

        return sum;
}

extern void bdi_writeout_inc(struct backing_dev_info *bdi);

/*
 * maximal error of a stat counter.
 */
static inline unsigned long bdi_stat_error(struct backing_dev_info *bdi)
{
#ifdef CONFIG_SMP
        return nr_cpu_ids * BDI_STAT_BATCH;
#else
        return 1;
#endif
}

int bdi_set_min_ratio(struct backing_dev_info *bdi, unsigned int min_ratio);
int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio);

/*
 * Flags in backing_dev_info::capability
 *
 * The first three 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)
 *
 * WARNING: these flags are closely related and should not normally be
 * used separately.  The BDI_CAP_NO_ACCT_AND_WRITEBACK combines these
 * three flags into a single convenience macro.
 *
 * BDI_CAP_NO_ACCT_DIRTY:  Dirty pages shouldn't contribute to accounting
 * BDI_CAP_NO_WRITEBACK:   Don't write pages back
 * BDI_CAP_NO_ACCT_WB:     Don't automatically account writeback pages
 *
 * These flags let !MMU mmap() govern direct device mapping vs immediate
 * copying more easily for MAP_PRIVATE, especially for ROM filesystems.
 *
 * BDI_CAP_MAP_COPY:       Copy can be mapped (MAP_PRIVATE)
 * BDI_CAP_MAP_DIRECT:     Can be mapped directly (MAP_SHARED)
 * BDI_CAP_READ_MAP:       Can be mapped for reading
 * BDI_CAP_WRITE_MAP:      Can be mapped for writing
 * BDI_CAP_EXEC_MAP:       Can be mapped for execution
 *
 * BDI_CAP_SWAP_BACKED:    Count shmem/tmpfs objects as swap-backed.
 */
#define BDI_CAP_NO_ACCT_DIRTY   0x00000001
#define BDI_CAP_NO_WRITEBACK    0x00000002
#define BDI_CAP_MAP_COPY        0x00000004
#define BDI_CAP_MAP_DIRECT      0x00000008
#define BDI_CAP_READ_MAP        0x00000010
#define BDI_CAP_WRITE_MAP       0x00000020
#define BDI_CAP_EXEC_MAP        0x00000040
#define BDI_CAP_NO_ACCT_WB      0x00000080
#define BDI_CAP_SWAP_BACKED     0x00000100

#define BDI_CAP_VMFLAGS \
        (BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP)

#define BDI_CAP_NO_ACCT_AND_WRITEBACK \
        (BDI_CAP_NO_WRITEBACK | BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_ACCT_WB)

#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_in_progress(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_sync_congested);
}

static inline int bdi_write_congested(struct backing_dev_info *bdi)
{
        return bdi_congested(bdi, 1 << BDI_async_congested);
}

static inline int bdi_rw_congested(struct backing_dev_info *bdi)
{
        return bdi_congested(bdi, (1 << BDI_sync_congested) |
                                  (1 << BDI_async_congested));
}

enum {
        BLK_RW_ASYNC    = 0,
        BLK_RW_SYNC     = 1,
};

void clear_bdi_congested(struct backing_dev_info *bdi, int sync);
void set_bdi_congested(struct backing_dev_info *bdi, int sync);
long congestion_wait(int sync, long timeout);


static inline bool bdi_cap_writeback_dirty(struct backing_dev_info *bdi)
{
        return !(bdi->capabilities & BDI_CAP_NO_WRITEBACK);
}

static inline bool bdi_cap_account_dirty(struct backing_dev_info *bdi)
{
        return !(bdi->capabilities & BDI_CAP_NO_ACCT_DIRTY);
}

static inline bool bdi_cap_account_writeback(struct backing_dev_info *bdi)
{
        /* Paranoia: BDI_CAP_NO_WRITEBACK implies BDI_CAP_NO_ACCT_WB */
        return !(bdi->capabilities & (BDI_CAP_NO_ACCT_WB |
                                      BDI_CAP_NO_WRITEBACK));
}

static inline bool bdi_cap_swap_backed(struct backing_dev_info *bdi)
{
        return bdi->capabilities & BDI_CAP_SWAP_BACKED;
}

static inline bool bdi_cap_flush_forker(struct backing_dev_info *bdi)
{
        return bdi == &default_backing_dev_info;
}

static inline bool mapping_cap_writeback_dirty(struct address_space *mapping)
{
        return bdi_cap_writeback_dirty(mapping->backing_dev_info);
}

static inline bool mapping_cap_account_dirty(struct address_space *mapping)
{
        return bdi_cap_account_dirty(mapping->backing_dev_info);
}

static inline bool mapping_cap_swap_backed(struct address_space *mapping)
{
        return bdi_cap_swap_backed(mapping->backing_dev_info);
}

static inline int bdi_sched_wait(void *word)
{
        schedule();
        return 0;
}

#endif          /* _LINUX_BACKING_DEV_H */