backing-dev.h

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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 <linux/percpu_counter.h>
#include <linux/log2.h>
#include <linux/flex_proportions.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/sched.h>
#include <linux/timer.h>
#include <linux/writeback.h>
#include <linux/atomic.h>
#include <linux/sysctl.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_writeback_running,  /* Writeback is in progress */
    BDI_unused,     /* Available bits start here */
};

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

enum bdi_stat_item {
    BDI_RECLAIMABLE,
    BDI_WRITEBACK,
    BDI_DIRTIED,
    BDI_WRITTEN,
    NR_BDI_STAT_ITEMS
};

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

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

    unsigned long last_old_flush;   /* last old data flush */
    unsigned long last_active;  /* last time bdi thread was active */

    struct task_struct *task;   /* writeback thread */
    struct timer_list wakeup_timer; /* used for delayed bdi thread wakeup */
    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 */
    spinlock_t list_lock;       /* protects the b_* lists */
};

struct backing_dev_info {
    struct list_head bdi_list;
    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 */

    char *name;

    struct percpu_counter bdi_stat[NR_BDI_STAT_ITEMS];

    unsigned long bw_time_stamp;    /* last time write bw is updated */
    unsigned long dirtied_stamp;
    unsigned long written_stamp;    /* pages written at bw_time_stamp */
    unsigned long write_bandwidth;  /* the estimated write bandwidth */
    unsigned long avg_write_bandwidth; /* further smoothed write bw */

    /*
     * The base dirty throttle rate, re-calculated on every 200ms.
     * All the bdi tasks' dirty rate will be curbed under it.
     * @dirty_ratelimit tracks the estimated @balanced_dirty_ratelimit
     * in small steps and is much more smooth/stable than the latter.
     */
    unsigned long dirty_ratelimit;
    unsigned long balanced_dirty_ratelimit;

    struct fprop_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 work_list */

    struct list_head work_list;

    struct device *dev;

    struct timer_list laptop_mode_wb_timer;

#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);
int bdi_setup_and_register(struct backing_dev_info *, char *, unsigned int);
void bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
            enum wb_reason reason);
void bdi_start_background_writeback(struct backing_dev_info *bdi);
int bdi_writeback_thread(void *data);
int bdi_has_dirty_io(struct backing_dev_info *bdi);
void bdi_wakeup_thread_delayed(struct backing_dev_info *bdi);
void bdi_lock_two(struct bdi_writeback *wb1, struct bdi_writeback *wb2);

extern spinlock_t bdi_lock;
extern struct list_head bdi_list;
extern struct list_head bdi_pending_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;
extern struct backing_dev_info noop_backing_dev_info;

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);
long wait_iff_congested(struct zone *zone, int sync, long timeout);
int pdflush_proc_obsolete(struct ctl_table *table, int write,
        void __user *buffer, size_t *lenp, loff_t *ppos);

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 */