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    Subject[PATCH 14/51] writeback: move bandwidth related fields from backing_dev_info into bdi_writeback
    Date
    Currently, a bdi (backing_dev_info) embeds single wb (bdi_writeback)
    and the role of the separation is unclear. For cgroup support for
    writeback IOs, a bdi will be updated to host multiple wb's where each
    wb serves writeback IOs of a different cgroup on the bdi. To achieve
    that, a wb should carry all states necessary for servicing writeback
    IOs for a cgroup independently.

    This patch moves bandwidth related fields from backing_dev_info into
    bdi_writeback.

    * The moved fields are: bw_time_stamp, dirtied_stamp, written_stamp,
    write_bandwidth, avg_write_bandwidth, dirty_ratelimit,
    balanced_dirty_ratelimit, completions and dirty_exceeded.

    * writeback_chunk_size() and over_bground_thresh() now take @wb
    instead of @bdi.

    * bdi_writeout_fraction(bdi, ...) -> wb_writeout_fraction(wb, ...)
    bdi_dirty_limit(bdi, ...) -> wb_dirty_limit(wb, ...)
    bdi_position_ration(bdi, ...) -> wb_position_ratio(wb, ...)
    bdi_update_writebandwidth(bdi, ...) -> wb_update_write_bandwidth(wb, ...)
    [__]bdi_update_bandwidth(bdi, ...) -> [__]wb_update_bandwidth(wb, ...)
    bdi_{max|min}_pause(bdi, ...) -> wb_{max|min}_pause(wb, ...)
    bdi_dirty_limits(bdi, ...) -> wb_dirty_limits(wb, ...)

    * Init/exits of the relocated fields are moved to bdi_wb_init/exit()
    respectively. Note that explicit zeroing is dropped in the process
    as wb's are cleared in entirety anyway.

    * As there's still only one bdi_writeback per backing_dev_info, all
    uses of bdi->stat[] are mechanically replaced with bdi->wb.stat[]
    introducing no behavior changes.

    v2: Typo in description fixed as suggested by Jan.

    Signed-off-by: Tejun Heo <tj@kernel.org>
    Reviewed-by: Jan Kara <jack@suse.cz>
    Cc: Jens Axboe <axboe@kernel.dk>
    Cc: Wu Fengguang <fengguang.wu@intel.com>
    Cc: Jaegeuk Kim <jaegeuk@kernel.org>
    Cc: Steven Whitehouse <swhiteho@redhat.com>
    ---
    fs/f2fs/node.c | 4 +-
    fs/f2fs/segment.h | 2 +-
    fs/fs-writeback.c | 17 ++-
    fs/gfs2/super.c | 2 +-
    include/linux/backing-dev.h | 20 +--
    include/linux/writeback.h | 19 ++-
    include/trace/events/writeback.h | 8 +-
    mm/backing-dev.c | 45 +++----
    mm/page-writeback.c | 262 ++++++++++++++++++++-------------------
    9 files changed, 187 insertions(+), 192 deletions(-)

    diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
    index 8ab0cf1..d211602 100644
    --- a/fs/f2fs/node.c
    +++ b/fs/f2fs/node.c
    @@ -53,7 +53,7 @@ bool available_free_memory(struct f2fs_sb_info *sbi, int type)
    PAGE_CACHE_SHIFT;
    res = mem_size < ((avail_ram * nm_i->ram_thresh / 100) >> 2);
    } else if (type == DIRTY_DENTS) {
    - if (sbi->sb->s_bdi->dirty_exceeded)
    + if (sbi->sb->s_bdi->wb.dirty_exceeded)
    return false;
    mem_size = get_pages(sbi, F2FS_DIRTY_DENTS);
    res = mem_size < ((avail_ram * nm_i->ram_thresh / 100) >> 1);
    @@ -70,7 +70,7 @@ bool available_free_memory(struct f2fs_sb_info *sbi, int type)
    sizeof(struct extent_node)) >> PAGE_CACHE_SHIFT;
    res = mem_size < ((avail_ram * nm_i->ram_thresh / 100) >> 1);
    } else {
    - if (sbi->sb->s_bdi->dirty_exceeded)
    + if (sbi->sb->s_bdi->wb.dirty_exceeded)
    return false;
    }
    return res;
    diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h
    index 85d7fa7..6408989 100644
    --- a/fs/f2fs/segment.h
    +++ b/fs/f2fs/segment.h
    @@ -713,7 +713,7 @@ static inline unsigned int max_hw_blocks(struct f2fs_sb_info *sbi)
    */
    static inline int nr_pages_to_skip(struct f2fs_sb_info *sbi, int type)
    {
    - if (sbi->sb->s_bdi->dirty_exceeded)
    + if (sbi->sb->s_bdi->wb.dirty_exceeded)
    return 0;

    if (type == DATA)
    diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
    index 8873ecd..1945cb9 100644
    --- a/fs/fs-writeback.c
    +++ b/fs/fs-writeback.c
    @@ -624,7 +624,7 @@ writeback_single_inode(struct inode *inode, struct bdi_writeback *wb,
    return ret;
    }

    -static long writeback_chunk_size(struct backing_dev_info *bdi,
    +static long writeback_chunk_size(struct bdi_writeback *wb,
    struct wb_writeback_work *work)
    {
    long pages;
    @@ -645,7 +645,7 @@ static long writeback_chunk_size(struct backing_dev_info *bdi,
    if (work->sync_mode == WB_SYNC_ALL || work->tagged_writepages)
    pages = LONG_MAX;
    else {
    - pages = min(bdi->avg_write_bandwidth / 2,
    + pages = min(wb->avg_write_bandwidth / 2,
    global_dirty_limit / DIRTY_SCOPE);
    pages = min(pages, work->nr_pages);
    pages = round_down(pages + MIN_WRITEBACK_PAGES,
    @@ -743,7 +743,7 @@ static long writeback_sb_inodes(struct super_block *sb,
    inode->i_state |= I_SYNC;
    spin_unlock(&inode->i_lock);

    - write_chunk = writeback_chunk_size(wb->bdi, work);
    + write_chunk = writeback_chunk_size(wb, work);
    wbc.nr_to_write = write_chunk;
    wbc.pages_skipped = 0;

    @@ -830,7 +830,7 @@ static long writeback_inodes_wb(struct bdi_writeback *wb, long nr_pages,
    return nr_pages - work.nr_pages;
    }

    -static bool over_bground_thresh(struct backing_dev_info *bdi)
    +static bool over_bground_thresh(struct bdi_writeback *wb)
    {
    unsigned long background_thresh, dirty_thresh;

    @@ -840,8 +840,7 @@ static bool over_bground_thresh(struct backing_dev_info *bdi)
    global_page_state(NR_UNSTABLE_NFS) > background_thresh)
    return true;

    - if (wb_stat(&bdi->wb, WB_RECLAIMABLE) >
    - bdi_dirty_limit(bdi, background_thresh))
    + if (wb_stat(wb, WB_RECLAIMABLE) > wb_dirty_limit(wb, background_thresh))
    return true;

    return false;
    @@ -854,7 +853,7 @@ static bool over_bground_thresh(struct backing_dev_info *bdi)
    static void wb_update_bandwidth(struct bdi_writeback *wb,
    unsigned long start_time)
    {
    - __bdi_update_bandwidth(wb->bdi, 0, 0, 0, 0, 0, start_time);
    + __wb_update_bandwidth(wb, 0, 0, 0, 0, 0, start_time);
    }

    /*
    @@ -906,7 +905,7 @@ static long wb_writeback(struct bdi_writeback *wb,
    * For background writeout, stop when we are below the
    * background dirty threshold
    */
    - if (work->for_background && !over_bground_thresh(wb->bdi))
    + if (work->for_background && !over_bground_thresh(wb))
    break;

    /*
    @@ -998,7 +997,7 @@ static unsigned long get_nr_dirty_pages(void)

    static long wb_check_background_flush(struct bdi_writeback *wb)
    {
    - if (over_bground_thresh(wb->bdi)) {
    + if (over_bground_thresh(wb)) {

    struct wb_writeback_work work = {
    .nr_pages = LONG_MAX,
    diff --git a/fs/gfs2/super.c b/fs/gfs2/super.c
    index 859c6ed..2982445 100644
    --- a/fs/gfs2/super.c
    +++ b/fs/gfs2/super.c
    @@ -748,7 +748,7 @@ static int gfs2_write_inode(struct inode *inode, struct writeback_control *wbc)

    if (wbc->sync_mode == WB_SYNC_ALL)
    gfs2_log_flush(GFS2_SB(inode), ip->i_gl, NORMAL_FLUSH);
    - if (bdi->dirty_exceeded)
    + if (bdi->wb.dirty_exceeded)
    gfs2_ail1_flush(sdp, wbc);
    else
    filemap_fdatawrite(metamapping);
    diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
    index fe7a907..2ab0604 100644
    --- a/include/linux/backing-dev.h
    +++ b/include/linux/backing-dev.h
    @@ -60,16 +60,6 @@ struct bdi_writeback {
    spinlock_t list_lock; /* protects the b_* lists */

    struct percpu_counter stat[NR_WB_STAT_ITEMS];
    -};
    -
    -struct backing_dev_info {
    - struct list_head bdi_list;
    - unsigned long ra_pages; /* max readahead in PAGE_CACHE_SIZE units */
    - 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;

    unsigned long bw_time_stamp; /* last time write bw is updated */
    unsigned long dirtied_stamp;
    @@ -88,6 +78,16 @@ struct backing_dev_info {

    struct fprop_local_percpu completions;
    int dirty_exceeded;
    +};
    +
    +struct backing_dev_info {
    + struct list_head bdi_list;
    + unsigned long ra_pages; /* max readahead in PAGE_CACHE_SIZE units */
    + 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;

    unsigned int min_ratio;
    unsigned int max_ratio, max_prop_frac;
    diff --git a/include/linux/writeback.h b/include/linux/writeback.h
    index b2dd371e..a6b9db7 100644
    --- a/include/linux/writeback.h
    +++ b/include/linux/writeback.h
    @@ -155,16 +155,15 @@ int dirty_writeback_centisecs_handler(struct ctl_table *, int,
    void __user *, size_t *, loff_t *);

    void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty);
    -unsigned long bdi_dirty_limit(struct backing_dev_info *bdi,
    - unsigned long dirty);
    -
    -void __bdi_update_bandwidth(struct backing_dev_info *bdi,
    - unsigned long thresh,
    - unsigned long bg_thresh,
    - unsigned long dirty,
    - unsigned long bdi_thresh,
    - unsigned long bdi_dirty,
    - unsigned long start_time);
    +unsigned long wb_dirty_limit(struct bdi_writeback *wb, unsigned long dirty);
    +
    +void __wb_update_bandwidth(struct bdi_writeback *wb,
    + unsigned long thresh,
    + unsigned long bg_thresh,
    + unsigned long dirty,
    + unsigned long bdi_thresh,
    + unsigned long bdi_dirty,
    + unsigned long start_time);

    void page_writeback_init(void);
    void balance_dirty_pages_ratelimited(struct address_space *mapping);
    diff --git a/include/trace/events/writeback.h b/include/trace/events/writeback.h
    index 880dd74..9b876f6 100644
    --- a/include/trace/events/writeback.h
    +++ b/include/trace/events/writeback.h
    @@ -400,13 +400,13 @@ TRACE_EVENT(bdi_dirty_ratelimit,

    TP_fast_assign(
    strlcpy(__entry->bdi, dev_name(bdi->dev), 32);
    - __entry->write_bw = KBps(bdi->write_bandwidth);
    - __entry->avg_write_bw = KBps(bdi->avg_write_bandwidth);
    + __entry->write_bw = KBps(bdi->wb.write_bandwidth);
    + __entry->avg_write_bw = KBps(bdi->wb.avg_write_bandwidth);
    __entry->dirty_rate = KBps(dirty_rate);
    - __entry->dirty_ratelimit = KBps(bdi->dirty_ratelimit);
    + __entry->dirty_ratelimit = KBps(bdi->wb.dirty_ratelimit);
    __entry->task_ratelimit = KBps(task_ratelimit);
    __entry->balanced_dirty_ratelimit =
    - KBps(bdi->balanced_dirty_ratelimit);
    + KBps(bdi->wb.balanced_dirty_ratelimit);
    ),

    TP_printk("bdi %s: "
    diff --git a/mm/backing-dev.c b/mm/backing-dev.c
    index 7b1d191..9a6c472 100644
    --- a/mm/backing-dev.c
    +++ b/mm/backing-dev.c
    @@ -66,7 +66,7 @@ static int bdi_debug_stats_show(struct seq_file *m, void *v)
    spin_unlock(&wb->list_lock);

    global_dirty_limits(&background_thresh, &dirty_thresh);
    - bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh);
    + bdi_thresh = wb_dirty_limit(wb, dirty_thresh);

    #define K(x) ((x) << (PAGE_SHIFT - 10))
    seq_printf(m,
    @@ -91,7 +91,7 @@ static int bdi_debug_stats_show(struct seq_file *m, void *v)
    K(background_thresh),
    (unsigned long) K(wb_stat(wb, WB_DIRTIED)),
    (unsigned long) K(wb_stat(wb, WB_WRITTEN)),
    - (unsigned long) K(bdi->write_bandwidth),
    + (unsigned long) K(wb->write_bandwidth),
    nr_dirty,
    nr_io,
    nr_more_io,
    @@ -376,6 +376,11 @@ void bdi_unregister(struct backing_dev_info *bdi)
    }
    EXPORT_SYMBOL(bdi_unregister);

    +/*
    + * Initial write bandwidth: 100 MB/s
    + */
    +#define INIT_BW (100 << (20 - PAGE_SHIFT))
    +
    static int bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
    {
    int i, err;
    @@ -391,11 +396,22 @@ static int bdi_wb_init(struct bdi_writeback *wb, struct backing_dev_info *bdi)
    spin_lock_init(&wb->list_lock);
    INIT_DELAYED_WORK(&wb->dwork, bdi_writeback_workfn);

    + wb->bw_time_stamp = jiffies;
    + wb->balanced_dirty_ratelimit = INIT_BW;
    + wb->dirty_ratelimit = INIT_BW;
    + wb->write_bandwidth = INIT_BW;
    + wb->avg_write_bandwidth = INIT_BW;
    +
    + err = fprop_local_init_percpu(&wb->completions, GFP_KERNEL);
    + if (err)
    + return err;
    +
    for (i = 0; i < NR_WB_STAT_ITEMS; i++) {
    err = percpu_counter_init(&wb->stat[i], 0, GFP_KERNEL);
    if (err) {
    while (--i)
    percpu_counter_destroy(&wb->stat[i]);
    + fprop_local_destroy_percpu(&wb->completions);
    return err;
    }
    }
    @@ -411,12 +427,9 @@ static void bdi_wb_exit(struct bdi_writeback *wb)

    for (i = 0; i < NR_WB_STAT_ITEMS; i++)
    percpu_counter_destroy(&wb->stat[i]);
    -}

    -/*
    - * Initial write bandwidth: 100 MB/s
    - */
    -#define INIT_BW (100 << (20 - PAGE_SHIFT))
    + fprop_local_destroy_percpu(&wb->completions);
    +}

    int bdi_init(struct backing_dev_info *bdi)
    {
    @@ -435,22 +448,6 @@ int bdi_init(struct backing_dev_info *bdi)
    if (err)
    return err;

    - bdi->dirty_exceeded = 0;
    -
    - bdi->bw_time_stamp = jiffies;
    - bdi->written_stamp = 0;
    -
    - bdi->balanced_dirty_ratelimit = INIT_BW;
    - bdi->dirty_ratelimit = INIT_BW;
    - bdi->write_bandwidth = INIT_BW;
    - bdi->avg_write_bandwidth = INIT_BW;
    -
    - err = fprop_local_init_percpu(&bdi->completions, GFP_KERNEL);
    - if (err) {
    - bdi_wb_exit(&bdi->wb);
    - return err;
    - }
    -
    return 0;
    }
    EXPORT_SYMBOL(bdi_init);
    @@ -468,8 +465,6 @@ void bdi_destroy(struct backing_dev_info *bdi)
    }

    bdi_wb_exit(&bdi->wb);
    -
    - fprop_local_destroy_percpu(&bdi->completions);
    }
    EXPORT_SYMBOL(bdi_destroy);

    diff --git a/mm/page-writeback.c b/mm/page-writeback.c
    index dc673a0..cd39ee9 100644
    --- a/mm/page-writeback.c
    +++ b/mm/page-writeback.c
    @@ -399,7 +399,7 @@ static unsigned long wp_next_time(unsigned long cur_time)
    static inline void __wb_writeout_inc(struct bdi_writeback *wb)
    {
    __inc_wb_stat(wb, WB_WRITTEN);
    - __fprop_inc_percpu_max(&writeout_completions, &wb->bdi->completions,
    + __fprop_inc_percpu_max(&writeout_completions, &wb->completions,
    wb->bdi->max_prop_frac);
    /* First event after period switching was turned off? */
    if (!unlikely(writeout_period_time)) {
    @@ -427,10 +427,10 @@ EXPORT_SYMBOL_GPL(wb_writeout_inc);
    /*
    * Obtain an accurate fraction of the BDI's portion.
    */
    -static void bdi_writeout_fraction(struct backing_dev_info *bdi,
    - long *numerator, long *denominator)
    +static void wb_writeout_fraction(struct bdi_writeback *wb,
    + long *numerator, long *denominator)
    {
    - fprop_fraction_percpu(&writeout_completions, &bdi->completions,
    + fprop_fraction_percpu(&writeout_completions, &wb->completions,
    numerator, denominator);
    }

    @@ -516,11 +516,11 @@ static unsigned long hard_dirty_limit(unsigned long thresh)
    }

    /**
    - * bdi_dirty_limit - @bdi's share of dirty throttling threshold
    - * @bdi: the backing_dev_info to query
    + * wb_dirty_limit - @wb's share of dirty throttling threshold
    + * @wb: bdi_writeback to query
    * @dirty: global dirty limit in pages
    *
    - * Returns @bdi's dirty limit in pages. The term "dirty" in the context of
    + * Returns @wb's dirty limit in pages. The term "dirty" in the context of
    * dirty balancing includes all PG_dirty, PG_writeback and NFS unstable pages.
    *
    * Note that balance_dirty_pages() will only seriously take it as a hard limit
    @@ -528,34 +528,35 @@ static unsigned long hard_dirty_limit(unsigned long thresh)
    * control. For example, when the device is completely stalled due to some error
    * conditions, or when there are 1000 dd tasks writing to a slow 10MB/s USB key.
    * In the other normal situations, it acts more gently by throttling the tasks
    - * more (rather than completely block them) when the bdi dirty pages go high.
    + * more (rather than completely block them) when the wb dirty pages go high.
    *
    * It allocates high/low dirty limits to fast/slow devices, in order to prevent
    * - starving fast devices
    * - piling up dirty pages (that will take long time to sync) on slow devices
    *
    - * The bdi's share of dirty limit will be adapting to its throughput and
    + * The wb's share of dirty limit will be adapting to its throughput and
    * bounded by the bdi->min_ratio and/or bdi->max_ratio parameters, if set.
    */
    -unsigned long bdi_dirty_limit(struct backing_dev_info *bdi, unsigned long dirty)
    +unsigned long wb_dirty_limit(struct bdi_writeback *wb, unsigned long dirty)
    {
    - u64 bdi_dirty;
    + struct backing_dev_info *bdi = wb->bdi;
    + u64 wb_dirty;
    long numerator, denominator;

    /*
    * Calculate this BDI's share of the dirty ratio.
    */
    - bdi_writeout_fraction(bdi, &numerator, &denominator);
    + wb_writeout_fraction(wb, &numerator, &denominator);

    - bdi_dirty = (dirty * (100 - bdi_min_ratio)) / 100;
    - bdi_dirty *= numerator;
    - do_div(bdi_dirty, denominator);
    + wb_dirty = (dirty * (100 - bdi_min_ratio)) / 100;
    + wb_dirty *= numerator;
    + do_div(wb_dirty, denominator);

    - bdi_dirty += (dirty * bdi->min_ratio) / 100;
    - if (bdi_dirty > (dirty * bdi->max_ratio) / 100)
    - bdi_dirty = dirty * bdi->max_ratio / 100;
    + wb_dirty += (dirty * bdi->min_ratio) / 100;
    + if (wb_dirty > (dirty * bdi->max_ratio) / 100)
    + wb_dirty = dirty * bdi->max_ratio / 100;

    - return bdi_dirty;
    + return wb_dirty;
    }

    /*
    @@ -664,14 +665,14 @@ static long long pos_ratio_polynom(unsigned long setpoint,
    * card's bdi_dirty may rush to many times higher than bdi_setpoint.
    * - the bdi dirty thresh drops quickly due to change of JBOD workload
    */
    -static unsigned long bdi_position_ratio(struct backing_dev_info *bdi,
    - unsigned long thresh,
    - unsigned long bg_thresh,
    - unsigned long dirty,
    - unsigned long bdi_thresh,
    - unsigned long bdi_dirty)
    +static unsigned long wb_position_ratio(struct bdi_writeback *wb,
    + unsigned long thresh,
    + unsigned long bg_thresh,
    + unsigned long dirty,
    + unsigned long bdi_thresh,
    + unsigned long bdi_dirty)
    {
    - unsigned long write_bw = bdi->avg_write_bandwidth;
    + unsigned long write_bw = wb->avg_write_bandwidth;
    unsigned long freerun = dirty_freerun_ceiling(thresh, bg_thresh);
    unsigned long limit = hard_dirty_limit(thresh);
    unsigned long x_intercept;
    @@ -702,12 +703,12 @@ static unsigned long bdi_position_ratio(struct backing_dev_info *bdi,
    * consume arbitrary amount of RAM because it is accounted in
    * NR_WRITEBACK_TEMP which is not involved in calculating "nr_dirty".
    *
    - * Here, in bdi_position_ratio(), we calculate pos_ratio based on
    + * Here, in wb_position_ratio(), we calculate pos_ratio based on
    * two values: bdi_dirty and bdi_thresh. Let's consider an example:
    * total amount of RAM is 16GB, bdi->max_ratio is equal to 1%, global
    * limits are set by default to 10% and 20% (background and throttle).
    * Then bdi_thresh is 1% of 20% of 16GB. This amounts to ~8K pages.
    - * bdi_dirty_limit(bdi, bg_thresh) is about ~4K pages. bdi_setpoint is
    + * wb_dirty_limit(wb, bg_thresh) is about ~4K pages. bdi_setpoint is
    * about ~6K pages (as the average of background and throttle bdi
    * limits). The 3rd order polynomial will provide positive feedback if
    * bdi_dirty is under bdi_setpoint and vice versa.
    @@ -717,7 +718,7 @@ static unsigned long bdi_position_ratio(struct backing_dev_info *bdi,
    * much earlier than global "freerun" is reached (~23MB vs. ~2.3GB
    * in the example above).
    */
    - if (unlikely(bdi->capabilities & BDI_CAP_STRICTLIMIT)) {
    + if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT)) {
    long long bdi_pos_ratio;
    unsigned long bdi_bg_thresh;

    @@ -842,13 +843,13 @@ static unsigned long bdi_position_ratio(struct backing_dev_info *bdi,
    return pos_ratio;
    }

    -static void bdi_update_write_bandwidth(struct backing_dev_info *bdi,
    - unsigned long elapsed,
    - unsigned long written)
    +static void wb_update_write_bandwidth(struct bdi_writeback *wb,
    + unsigned long elapsed,
    + unsigned long written)
    {
    const unsigned long period = roundup_pow_of_two(3 * HZ);
    - unsigned long avg = bdi->avg_write_bandwidth;
    - unsigned long old = bdi->write_bandwidth;
    + unsigned long avg = wb->avg_write_bandwidth;
    + unsigned long old = wb->write_bandwidth;
    u64 bw;

    /*
    @@ -861,14 +862,14 @@ static void bdi_update_write_bandwidth(struct backing_dev_info *bdi,
    * @written may have decreased due to account_page_redirty().
    * Avoid underflowing @bw calculation.
    */
    - bw = written - min(written, bdi->written_stamp);
    + bw = written - min(written, wb->written_stamp);
    bw *= HZ;
    if (unlikely(elapsed > period)) {
    do_div(bw, elapsed);
    avg = bw;
    goto out;
    }
    - bw += (u64)bdi->write_bandwidth * (period - elapsed);
    + bw += (u64)wb->write_bandwidth * (period - elapsed);
    bw >>= ilog2(period);

    /*
    @@ -881,8 +882,8 @@ static void bdi_update_write_bandwidth(struct backing_dev_info *bdi,
    avg += (old - avg) >> 3;

    out:
    - bdi->write_bandwidth = bw;
    - bdi->avg_write_bandwidth = avg;
    + wb->write_bandwidth = bw;
    + wb->avg_write_bandwidth = avg;
    }

    /*
    @@ -947,20 +948,20 @@ static void global_update_bandwidth(unsigned long thresh,
    * Normal bdi tasks will be curbed at or below it in long term.
    * Obviously it should be around (write_bw / N) when there are N dd tasks.
    */
    -static void bdi_update_dirty_ratelimit(struct backing_dev_info *bdi,
    - unsigned long thresh,
    - unsigned long bg_thresh,
    - unsigned long dirty,
    - unsigned long bdi_thresh,
    - unsigned long bdi_dirty,
    - unsigned long dirtied,
    - unsigned long elapsed)
    +static void wb_update_dirty_ratelimit(struct bdi_writeback *wb,
    + unsigned long thresh,
    + unsigned long bg_thresh,
    + unsigned long dirty,
    + unsigned long bdi_thresh,
    + unsigned long bdi_dirty,
    + unsigned long dirtied,
    + unsigned long elapsed)
    {
    unsigned long freerun = dirty_freerun_ceiling(thresh, bg_thresh);
    unsigned long limit = hard_dirty_limit(thresh);
    unsigned long setpoint = (freerun + limit) / 2;
    - unsigned long write_bw = bdi->avg_write_bandwidth;
    - unsigned long dirty_ratelimit = bdi->dirty_ratelimit;
    + unsigned long write_bw = wb->avg_write_bandwidth;
    + unsigned long dirty_ratelimit = wb->dirty_ratelimit;
    unsigned long dirty_rate;
    unsigned long task_ratelimit;
    unsigned long balanced_dirty_ratelimit;
    @@ -972,10 +973,10 @@ static void bdi_update_dirty_ratelimit(struct backing_dev_info *bdi,
    * The dirty rate will match the writeout rate in long term, except
    * when dirty pages are truncated by userspace or re-dirtied by FS.
    */
    - dirty_rate = (dirtied - bdi->dirtied_stamp) * HZ / elapsed;
    + dirty_rate = (dirtied - wb->dirtied_stamp) * HZ / elapsed;

    - pos_ratio = bdi_position_ratio(bdi, thresh, bg_thresh, dirty,
    - bdi_thresh, bdi_dirty);
    + pos_ratio = wb_position_ratio(wb, thresh, bg_thresh, dirty,
    + bdi_thresh, bdi_dirty);
    /*
    * task_ratelimit reflects each dd's dirty rate for the past 200ms.
    */
    @@ -1059,31 +1060,31 @@ static void bdi_update_dirty_ratelimit(struct backing_dev_info *bdi,

    /*
    * For strictlimit case, calculations above were based on bdi counters
    - * and limits (starting from pos_ratio = bdi_position_ratio() and up to
    + * and limits (starting from pos_ratio = wb_position_ratio() and up to
    * balanced_dirty_ratelimit = task_ratelimit * write_bw / dirty_rate).
    * Hence, to calculate "step" properly, we have to use bdi_dirty as
    * "dirty" and bdi_setpoint as "setpoint".
    *
    * We rampup dirty_ratelimit forcibly if bdi_dirty is low because
    * it's possible that bdi_thresh is close to zero due to inactivity
    - * of backing device (see the implementation of bdi_dirty_limit()).
    + * of backing device (see the implementation of wb_dirty_limit()).
    */
    - if (unlikely(bdi->capabilities & BDI_CAP_STRICTLIMIT)) {
    + if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT)) {
    dirty = bdi_dirty;
    if (bdi_dirty < 8)
    setpoint = bdi_dirty + 1;
    else
    setpoint = (bdi_thresh +
    - bdi_dirty_limit(bdi, bg_thresh)) / 2;
    + wb_dirty_limit(wb, bg_thresh)) / 2;
    }

    if (dirty < setpoint) {
    - x = min3(bdi->balanced_dirty_ratelimit,
    + x = min3(wb->balanced_dirty_ratelimit,
    balanced_dirty_ratelimit, task_ratelimit);
    if (dirty_ratelimit < x)
    step = x - dirty_ratelimit;
    } else {
    - x = max3(bdi->balanced_dirty_ratelimit,
    + x = max3(wb->balanced_dirty_ratelimit,
    balanced_dirty_ratelimit, task_ratelimit);
    if (dirty_ratelimit > x)
    step = dirty_ratelimit - x;
    @@ -1105,22 +1106,22 @@ static void bdi_update_dirty_ratelimit(struct backing_dev_info *bdi,
    else
    dirty_ratelimit -= step;

    - bdi->dirty_ratelimit = max(dirty_ratelimit, 1UL);
    - bdi->balanced_dirty_ratelimit = balanced_dirty_ratelimit;
    + wb->dirty_ratelimit = max(dirty_ratelimit, 1UL);
    + wb->balanced_dirty_ratelimit = balanced_dirty_ratelimit;

    - trace_bdi_dirty_ratelimit(bdi, dirty_rate, task_ratelimit);
    + trace_bdi_dirty_ratelimit(wb->bdi, dirty_rate, task_ratelimit);
    }

    -void __bdi_update_bandwidth(struct backing_dev_info *bdi,
    - unsigned long thresh,
    - unsigned long bg_thresh,
    - unsigned long dirty,
    - unsigned long bdi_thresh,
    - unsigned long bdi_dirty,
    - unsigned long start_time)
    +void __wb_update_bandwidth(struct bdi_writeback *wb,
    + unsigned long thresh,
    + unsigned long bg_thresh,
    + unsigned long dirty,
    + unsigned long bdi_thresh,
    + unsigned long bdi_dirty,
    + unsigned long start_time)
    {
    unsigned long now = jiffies;
    - unsigned long elapsed = now - bdi->bw_time_stamp;
    + unsigned long elapsed = now - wb->bw_time_stamp;
    unsigned long dirtied;
    unsigned long written;

    @@ -1130,44 +1131,44 @@ void __bdi_update_bandwidth(struct backing_dev_info *bdi,
    if (elapsed < BANDWIDTH_INTERVAL)
    return;

    - dirtied = percpu_counter_read(&bdi->wb.stat[WB_DIRTIED]);
    - written = percpu_counter_read(&bdi->wb.stat[WB_WRITTEN]);
    + dirtied = percpu_counter_read(&wb->stat[WB_DIRTIED]);
    + written = percpu_counter_read(&wb->stat[WB_WRITTEN]);

    /*
    * Skip quiet periods when disk bandwidth is under-utilized.
    * (at least 1s idle time between two flusher runs)
    */
    - if (elapsed > HZ && time_before(bdi->bw_time_stamp, start_time))
    + if (elapsed > HZ && time_before(wb->bw_time_stamp, start_time))
    goto snapshot;

    if (thresh) {
    global_update_bandwidth(thresh, dirty, now);
    - bdi_update_dirty_ratelimit(bdi, thresh, bg_thresh, dirty,
    - bdi_thresh, bdi_dirty,
    - dirtied, elapsed);
    + wb_update_dirty_ratelimit(wb, thresh, bg_thresh, dirty,
    + bdi_thresh, bdi_dirty,
    + dirtied, elapsed);
    }
    - bdi_update_write_bandwidth(bdi, elapsed, written);
    + wb_update_write_bandwidth(wb, elapsed, written);

    snapshot:
    - bdi->dirtied_stamp = dirtied;
    - bdi->written_stamp = written;
    - bdi->bw_time_stamp = now;
    + wb->dirtied_stamp = dirtied;
    + wb->written_stamp = written;
    + wb->bw_time_stamp = now;
    }

    -static void bdi_update_bandwidth(struct backing_dev_info *bdi,
    - unsigned long thresh,
    - unsigned long bg_thresh,
    - unsigned long dirty,
    - unsigned long bdi_thresh,
    - unsigned long bdi_dirty,
    - unsigned long start_time)
    +static void wb_update_bandwidth(struct bdi_writeback *wb,
    + unsigned long thresh,
    + unsigned long bg_thresh,
    + unsigned long dirty,
    + unsigned long bdi_thresh,
    + unsigned long bdi_dirty,
    + unsigned long start_time)
    {
    - if (time_is_after_eq_jiffies(bdi->bw_time_stamp + BANDWIDTH_INTERVAL))
    + if (time_is_after_eq_jiffies(wb->bw_time_stamp + BANDWIDTH_INTERVAL))
    return;
    - spin_lock(&bdi->wb.list_lock);
    - __bdi_update_bandwidth(bdi, thresh, bg_thresh, dirty,
    - bdi_thresh, bdi_dirty, start_time);
    - spin_unlock(&bdi->wb.list_lock);
    + spin_lock(&wb->list_lock);
    + __wb_update_bandwidth(wb, thresh, bg_thresh, dirty,
    + bdi_thresh, bdi_dirty, start_time);
    + spin_unlock(&wb->list_lock);
    }

    /*
    @@ -1187,10 +1188,10 @@ static unsigned long dirty_poll_interval(unsigned long dirty,
    return 1;
    }

    -static unsigned long bdi_max_pause(struct backing_dev_info *bdi,
    - unsigned long bdi_dirty)
    +static unsigned long wb_max_pause(struct bdi_writeback *wb,
    + unsigned long bdi_dirty)
    {
    - unsigned long bw = bdi->avg_write_bandwidth;
    + unsigned long bw = wb->avg_write_bandwidth;
    unsigned long t;

    /*
    @@ -1206,14 +1207,14 @@ static unsigned long bdi_max_pause(struct backing_dev_info *bdi,
    return min_t(unsigned long, t, MAX_PAUSE);
    }

    -static long bdi_min_pause(struct backing_dev_info *bdi,
    - long max_pause,
    - unsigned long task_ratelimit,
    - unsigned long dirty_ratelimit,
    - int *nr_dirtied_pause)
    +static long wb_min_pause(struct bdi_writeback *wb,
    + long max_pause,
    + unsigned long task_ratelimit,
    + unsigned long dirty_ratelimit,
    + int *nr_dirtied_pause)
    {
    - long hi = ilog2(bdi->avg_write_bandwidth);
    - long lo = ilog2(bdi->dirty_ratelimit);
    + long hi = ilog2(wb->avg_write_bandwidth);
    + long lo = ilog2(wb->dirty_ratelimit);
    long t; /* target pause */
    long pause; /* estimated next pause */
    int pages; /* target nr_dirtied_pause */
    @@ -1281,14 +1282,13 @@ static long bdi_min_pause(struct backing_dev_info *bdi,
    return pages >= DIRTY_POLL_THRESH ? 1 + t / 2 : t;
    }

    -static inline void bdi_dirty_limits(struct backing_dev_info *bdi,
    - unsigned long dirty_thresh,
    - unsigned long background_thresh,
    - unsigned long *bdi_dirty,
    - unsigned long *bdi_thresh,
    - unsigned long *bdi_bg_thresh)
    +static inline void wb_dirty_limits(struct bdi_writeback *wb,
    + unsigned long dirty_thresh,
    + unsigned long background_thresh,
    + unsigned long *bdi_dirty,
    + unsigned long *bdi_thresh,
    + unsigned long *bdi_bg_thresh)
    {
    - struct bdi_writeback *wb = &bdi->wb;
    unsigned long wb_reclaimable;

    /*
    @@ -1301,10 +1301,10 @@ static inline void bdi_dirty_limits(struct backing_dev_info *bdi,
    * In this case we don't want to hard throttle the USB key
    * dirtiers for 100 seconds until bdi_dirty drops under
    * bdi_thresh. Instead the auxiliary bdi control line in
    - * bdi_position_ratio() will let the dirtier task progress
    + * wb_position_ratio() will let the dirtier task progress
    * at some rate <= (write_bw / 2) for bringing down bdi_dirty.
    */
    - *bdi_thresh = bdi_dirty_limit(bdi, dirty_thresh);
    + *bdi_thresh = wb_dirty_limit(wb, dirty_thresh);

    if (bdi_bg_thresh)
    *bdi_bg_thresh = dirty_thresh ? div_u64((u64)*bdi_thresh *
    @@ -1354,6 +1354,7 @@ static void balance_dirty_pages(struct address_space *mapping,
    unsigned long dirty_ratelimit;
    unsigned long pos_ratio;
    struct backing_dev_info *bdi = inode_to_bdi(mapping->host);
    + struct bdi_writeback *wb = &bdi->wb;
    bool strictlimit = bdi->capabilities & BDI_CAP_STRICTLIMIT;
    unsigned long start_time = jiffies;

    @@ -1378,8 +1379,8 @@ static void balance_dirty_pages(struct address_space *mapping,
    global_dirty_limits(&background_thresh, &dirty_thresh);

    if (unlikely(strictlimit)) {
    - bdi_dirty_limits(bdi, dirty_thresh, background_thresh,
    - &bdi_dirty, &bdi_thresh, &bg_thresh);
    + wb_dirty_limits(wb, dirty_thresh, background_thresh,
    + &bdi_dirty, &bdi_thresh, &bg_thresh);

    dirty = bdi_dirty;
    thresh = bdi_thresh;
    @@ -1410,28 +1411,28 @@ static void balance_dirty_pages(struct address_space *mapping,
    bdi_start_background_writeback(bdi);

    if (!strictlimit)
    - bdi_dirty_limits(bdi, dirty_thresh, background_thresh,
    - &bdi_dirty, &bdi_thresh, NULL);
    + wb_dirty_limits(wb, dirty_thresh, background_thresh,
    + &bdi_dirty, &bdi_thresh, NULL);

    dirty_exceeded = (bdi_dirty > bdi_thresh) &&
    ((nr_dirty > dirty_thresh) || strictlimit);
    - if (dirty_exceeded && !bdi->dirty_exceeded)
    - bdi->dirty_exceeded = 1;
    + if (dirty_exceeded && !wb->dirty_exceeded)
    + wb->dirty_exceeded = 1;

    - bdi_update_bandwidth(bdi, dirty_thresh, background_thresh,
    - nr_dirty, bdi_thresh, bdi_dirty,
    - start_time);
    + wb_update_bandwidth(wb, dirty_thresh, background_thresh,
    + nr_dirty, bdi_thresh, bdi_dirty,
    + start_time);

    - dirty_ratelimit = bdi->dirty_ratelimit;
    - pos_ratio = bdi_position_ratio(bdi, dirty_thresh,
    - background_thresh, nr_dirty,
    - bdi_thresh, bdi_dirty);
    + dirty_ratelimit = wb->dirty_ratelimit;
    + pos_ratio = wb_position_ratio(wb, dirty_thresh,
    + background_thresh, nr_dirty,
    + bdi_thresh, bdi_dirty);
    task_ratelimit = ((u64)dirty_ratelimit * pos_ratio) >>
    RATELIMIT_CALC_SHIFT;
    - max_pause = bdi_max_pause(bdi, bdi_dirty);
    - min_pause = bdi_min_pause(bdi, max_pause,
    - task_ratelimit, dirty_ratelimit,
    - &nr_dirtied_pause);
    + max_pause = wb_max_pause(wb, bdi_dirty);
    + min_pause = wb_min_pause(wb, max_pause,
    + task_ratelimit, dirty_ratelimit,
    + &nr_dirtied_pause);

    if (unlikely(task_ratelimit == 0)) {
    period = max_pause;
    @@ -1515,15 +1516,15 @@ static void balance_dirty_pages(struct address_space *mapping,
    * more page. However bdi_dirty has accounting errors. So use
    * the larger and more IO friendly wb_stat_error.
    */
    - if (bdi_dirty <= wb_stat_error(&bdi->wb))
    + if (bdi_dirty <= wb_stat_error(wb))
    break;

    if (fatal_signal_pending(current))
    break;
    }

    - if (!dirty_exceeded && bdi->dirty_exceeded)
    - bdi->dirty_exceeded = 0;
    + if (!dirty_exceeded && wb->dirty_exceeded)
    + wb->dirty_exceeded = 0;

    if (writeback_in_progress(bdi))
    return;
    @@ -1577,6 +1578,7 @@ DEFINE_PER_CPU(int, dirty_throttle_leaks) = 0;
    void balance_dirty_pages_ratelimited(struct address_space *mapping)
    {
    struct backing_dev_info *bdi = inode_to_bdi(mapping->host);
    + struct bdi_writeback *wb = &bdi->wb;
    int ratelimit;
    int *p;

    @@ -1584,7 +1586,7 @@ void balance_dirty_pages_ratelimited(struct address_space *mapping)
    return;

    ratelimit = current->nr_dirtied_pause;
    - if (bdi->dirty_exceeded)
    + if (wb->dirty_exceeded)
    ratelimit = min(ratelimit, 32 >> (PAGE_SHIFT - 10));

    preempt_disable();
    --
    2.4.0


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