Commit 8a731799 authored by Tejun Heo's avatar Tejun Heo Committed by Jens Axboe
Browse files

writeback: reorganize [__]wb_update_bandwidth() 



__wb_update_bandwidth() is called from two places -
fs/fs-writeback.c::balance_dirty_pages() and
mm/page-writeback.c::wb_writeback().  The latter updates only the
write bandwidth while the former also deals with the dirty ratelimit.
The two callsites are distinguished by whether @thresh parameter is
zero or not, which is cryptic.  In addition, the two files define
their own different versions of wb_update_bandwidth() on top of
__wb_update_bandwidth(), which is confusing to say the least.  This
patch cleans up [__]wb_update_bandwidth() in the following ways.

* __wb_update_bandwidth() now takes explicit @update_ratelimit
  parameter to gate dirty ratelimit handling.

* mm/page-writeback.c::wb_update_bandwidth() is flattened into its
  caller - balance_dirty_pages().

* fs/fs-writeback.c::wb_update_bandwidth() is moved to
  mm/page-writeback.c and __wb_update_bandwidth() is made static.

* While at it, add a lockdep assertion to __wb_update_bandwidth().

Except for the lockdep addition, this is pure reorganization and
doesn't introduce any behavioral changes.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jan Kara <jack@suse.cz>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Greg Thelen <gthelen@google.com>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent 0d960a38

fs/fs-writeback.c

+0 −10
Original line number Diff line number Diff line
@@ -1087,16 +1087,6 @@ static bool over_bground_thresh(struct bdi_writeback *wb) 
	return false;

}



/*

 * Called under wb->list_lock. If there are multiple wb per bdi,

 * only the flusher working on the first wb should do it.

 */

static void wb_update_bandwidth(struct bdi_writeback *wb,

				unsigned long start_time)

{

	__wb_update_bandwidth(wb, 0, 0, 0, 0, 0, start_time);

}



/*

 * Explicit flushing or periodic writeback of "old" data.

 *

include/linux/writeback.h

+1 −8
Original line number Diff line number Diff line
@@ -157,14 +157,7 @@ int dirty_writeback_centisecs_handler(struct ctl_table *, int, 
void global_dirty_limits(unsigned long *pbackground, unsigned long *pdirty);

unsigned long wb_calc_thresh(struct bdi_writeback *wb, unsigned long thresh);



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 wb_update_bandwidth(struct bdi_writeback *wb, unsigned long start_time);

void page_writeback_init(void);

void balance_dirty_pages_ratelimited(struct address_space *mapping);

mm/page-writeback.c

+22 −23
Original line number Diff line number Diff line
@@ -1160,19 +1160,22 @@ static void wb_update_dirty_ratelimit(struct bdi_writeback *wb, 
	trace_bdi_dirty_ratelimit(wb->bdi, dirty_rate, task_ratelimit);

}



void __wb_update_bandwidth(struct bdi_writeback *wb,

static void __wb_update_bandwidth(struct bdi_writeback *wb,

				  unsigned long thresh,

				  unsigned long bg_thresh,

				  unsigned long dirty,

				  unsigned long wb_thresh,

				  unsigned long wb_dirty,

			   unsigned long start_time)

				  unsigned long start_time,

				  bool update_ratelimit)

{

	unsigned long now = jiffies;

	unsigned long elapsed = now - wb->bw_time_stamp;

	unsigned long dirtied;

	unsigned long written;



	lockdep_assert_held(&wb->list_lock);



	/*

	 * rate-limit, only update once every 200ms.

	 */
@@ -1189,7 +1192,7 @@ void __wb_update_bandwidth(struct bdi_writeback *wb, 
	if (elapsed > HZ && time_before(wb->bw_time_stamp, start_time))

		goto snapshot;



	if (thresh) {

	if (update_ratelimit) {

		global_update_bandwidth(thresh, dirty, now);

		wb_update_dirty_ratelimit(wb, thresh, bg_thresh, dirty,

					  wb_thresh, wb_dirty,
@@ -1203,20 +1206,9 @@ snapshot: 
	wb->bw_time_stamp = now;

}



static void wb_update_bandwidth(struct bdi_writeback *wb,

				unsigned long thresh,

				unsigned long bg_thresh,

				unsigned long dirty,

				unsigned long wb_thresh,

				unsigned long wb_dirty,

				unsigned long start_time)

void wb_update_bandwidth(struct bdi_writeback *wb, unsigned long start_time)

{

	if (time_is_after_eq_jiffies(wb->bw_time_stamp + BANDWIDTH_INTERVAL))

		return;

	spin_lock(&wb->list_lock);

	__wb_update_bandwidth(wb, thresh, bg_thresh, dirty,

			      wb_thresh, wb_dirty, start_time);

	spin_unlock(&wb->list_lock);

	__wb_update_bandwidth(wb, 0, 0, 0, 0, 0, start_time, false);

}



/*
@@ -1467,8 +1459,15 @@ static void balance_dirty_pages(struct address_space *mapping, 
		if (dirty_exceeded && !wb->dirty_exceeded)

			wb->dirty_exceeded = 1;



		wb_update_bandwidth(wb, dirty_thresh, background_thresh,

				    nr_dirty, wb_thresh, wb_dirty, start_time);

		if (time_is_before_jiffies(wb->bw_time_stamp +

					   BANDWIDTH_INTERVAL)) {

			spin_lock(&wb->list_lock);

			__wb_update_bandwidth(wb, dirty_thresh,

					      background_thresh, nr_dirty,

					      wb_thresh, wb_dirty, start_time,

					      true);

			spin_unlock(&wb->list_lock);

		}



		dirty_ratelimit = wb->dirty_ratelimit;

		pos_ratio = wb_position_ratio(wb, dirty_thresh,

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