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Message-ID: <20141120155253.GH2330@quack.suse.cz>
Date: Thu, 20 Nov 2014 16:52:53 +0100
From: Jan Kara <jack@...e.cz>
To: Tejun Heo <tj@...nel.org>
Cc: axboe@...nel.dk, linux-kernel@...r.kernel.org, jack@...e.cz,
Wu Fengguang <fengguang.wu@...el.com>,
Jaegeuk Kim <jaegeuk@...nel.org>,
Steven Whitehouse <swhiteho@...hat.com>
Subject: Re: [PATCH 03/10] writeback: move bandwidth related fields from
backing_dev_info into bdi_writeback
On Tue 18-11-14 03:37:21, Tejun Heo wrote:
> 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_bgroup_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.
Ok, no problem with this patch but I wonder: When you are moving all the
dirty limiting logic to bdi_writeback, then how do you plan to interpret
min/max_ratio in presence of several bdi_writeback structures?
Honza
>
> Signed-off-by: Tejun Heo <tj@...nel.org>
> Cc: Jens Axboe <axboe@...nel.dk>
> Cc: Jan Kara <jack@...e.cz>
> Cc: Wu Fengguang <fengguang.wu@...el.com>
> Cc: Jaegeuk Kim <jaegeuk@...nel.org>
> Cc: Steven Whitehouse <swhiteho@...hat.com>
> ---
> fs/f2fs/node.c | 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 | 246 ++++++++++++++++++++-------------------
> 8 files changed, 177 insertions(+), 182 deletions(-)
>
> diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
> index 44b8afe..c53d94b 100644
> --- a/fs/f2fs/node.c
> +++ b/fs/f2fs/node.c
> @@ -43,7 +43,7 @@ bool available_free_memory(struct f2fs_sb_info *sbi, int type)
> mem_size = (nm_i->nat_cnt * sizeof(struct nat_entry)) >> 12;
> res = mem_size < ((val.totalram * 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 < ((val.totalram * nm_i->ram_thresh / 100) >> 1);
> diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
> index f5ca16e..daa91ae 100644
> --- a/fs/fs-writeback.c
> +++ b/fs/fs-writeback.c
> @@ -574,7 +574,7 @@ out:
> 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;
> @@ -595,7 +595,7 @@ 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,
> @@ -693,7 +693,7 @@ 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;
>
> @@ -780,7 +780,7 @@ 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;
>
> @@ -790,8 +790,7 @@ 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;
> @@ -804,7 +803,7 @@ 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);
> }
>
> /*
> @@ -856,7 +855,7 @@ 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;
>
> /*
> @@ -948,7 +947,7 @@ 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 a346f56..4566c89 100644
> --- a/fs/gfs2/super.c
> +++ b/fs/gfs2/super.c
> @@ -755,7 +755,7 @@ 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 92fed42..a077a8d 100644
> --- a/include/linux/backing-dev.h
> +++ b/include/linux/backing-dev.h
> @@ -59,16 +59,6 @@ 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;
> @@ -87,6 +77,16 @@ 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 a219be9..6887eb5 100644
> --- a/include/linux/writeback.h
> +++ b/include/linux/writeback.h
> @@ -152,16 +152,15 @@ 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 cee02d6..8622b5b 100644
> --- a/include/trace/events/writeback.h
> +++ b/include/trace/events/writeback.h
> @@ -373,13 +373,13 @@ 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 4b6f650..7b9b10e 100644
> --- a/mm/backing-dev.c
> +++ b/mm/backing-dev.c
> @@ -82,7 +82,7 @@ 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,
> @@ -106,7 +106,7 @@ 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,
> @@ -408,6 +408,11 @@ 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;
> @@ -422,11 +427,22 @@ 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;
> }
> }
> @@ -442,12 +458,9 @@ 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)
> {
> @@ -466,22 +479,6 @@ 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);
> @@ -514,8 +511,6 @@ void bdi_destroy(struct backing_dev_info *bdi)
>
> bdi_unregister(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 68fd72a..7c721b4 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: the 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
> @@ -528,24 +528,25 @@ 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)
> {
> + struct backing_dev_info *bdi = wb->bdi;
> u64 bdi_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;
> @@ -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;
>
> /*
> @@ -858,14 +859,14 @@ static void bdi_update_write_bandwidth(struct backing_dev_info *bdi,
> * write_bandwidth = ---------------------------------------------------
> * period
> */
> - bw = written - bdi->written_stamp;
> + bw = 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);
>
> /*
> @@ -878,8 +879,8 @@ 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;
> }
>
> /*
> @@ -944,20 +945,20 @@ 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;
> @@ -969,10 +970,10 @@ 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.
> */
> @@ -1056,31 +1057,31 @@ 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;
> @@ -1102,22 +1103,22 @@ 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;
>
> @@ -1127,44 +1128,44 @@ 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);
> }
>
> /*
> @@ -1184,10 +1185,10 @@ 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;
>
> /*
> @@ -1203,14 +1204,14 @@ 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 */
> @@ -1278,14 +1279,13 @@ 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;
>
> /*
> @@ -1298,10 +1298,10 @@ 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 *
> @@ -1351,6 +1351,7 @@ static void balance_dirty_pages(struct address_space *mapping,
> unsigned long dirty_ratelimit;
> unsigned long pos_ratio;
> struct backing_dev_info *bdi = mapping->backing_dev_info;
> + struct bdi_writeback *wb = &bdi->wb;
> bool strictlimit = bdi->capabilities & BDI_CAP_STRICTLIMIT;
> unsigned long start_time = jiffies;
>
> @@ -1375,8 +1376,8 @@ 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;
> @@ -1407,28 +1408,28 @@ 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;
> @@ -1512,15 +1513,15 @@ pause:
> * 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;
> @@ -1584,6 +1585,7 @@ DEFINE_PER_CPU(int, dirty_throttle_leaks) = 0;
> void balance_dirty_pages_ratelimited(struct address_space *mapping)
> {
> struct backing_dev_info *bdi = mapping->backing_dev_info;
> + struct bdi_writeback *wb = &bdi->wb;
> int ratelimit;
> int *p;
>
> @@ -1591,7 +1593,7 @@ 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();
> --
> 1.9.3
>
--
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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