linux-kernel - [PATCH 10/19] writeback: add dirty_throttle_control->wb

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Message-Id: <1432333416-6221-11-git-send-email-tj@kernel.org>
Date:	Fri, 22 May 2015 18:23:27 -0400
From:	Tejun Heo <tj@...nel.org>
To:	axboe@...nel.dk
Cc:	linux-kernel@...r.kernel.org, jack@...e.cz, hch@...radead.org,
	hannes@...xchg.org, linux-fsdevel@...r.kernel.org,
	vgoyal@...hat.com, lizefan@...wei.com, cgroups@...r.kernel.org,
	linux-mm@...ck.org, mhocko@...e.cz, clm@...com,
	fengguang.wu@...el.com, david@...morbit.com, gthelen@...gle.com,
	khlebnikov@...dex-team.ru, Tejun Heo <tj@...nel.org>
Subject: [PATCH 10/19] writeback: add dirty_throttle_control->wb_completions

wb->completions measures the wb's proportional write bandwidth in
global_wb_domain and thus naturally tied to the wb_domain.  This patch
adds dirty_throttle_control->wb_completions which is initialized to
wb->completions by GDTC_INIT() and updates __wb_dirty_limits() to use
it instead of dereferencing wb->completions directly.

This will allow dirty_throttle_control to represent different
wb_domains and the matching wb completions.

This patch doesn't introduce any behavioral changes.

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: Greg Thelen <gthelen@...gle.com>
---
 mm/page-writeback.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index fcebae7..5b439fc 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -127,6 +127,7 @@ struct wb_domain global_wb_domain;
 /* consolidated parameters for balance_dirty_pages() and its subroutines */
 struct dirty_throttle_control {
 	struct bdi_writeback	*wb;
+	struct fprop_local_percpu *wb_completions;
 
 	unsigned long		dirty;		/* file_dirty + write + nfs */
 	unsigned long		thresh;		/* dirty threshold */
@@ -139,7 +140,8 @@ struct dirty_throttle_control {
 	unsigned long		pos_ratio;
 };
 
-#define GDTC_INIT(__wb)		.wb = (__wb)
+#define GDTC_INIT(__wb)		.wb = (__wb),				\
+				.wb_completions = &(__wb)->completions
 
 /*
  * Length of period for aging writeout fractions of bdis. This is an
@@ -590,7 +592,7 @@ static unsigned long __wb_calc_thresh(struct dirty_throttle_control *dtc)
 	/*
 	 * Calculate this BDI's share of the thresh ratio.
 	 */
-	fprop_fraction_percpu(&dom->completions, &dtc->wb->completions,
+	fprop_fraction_percpu(&dom->completions, dtc->wb_completions,
 			      &numerator, &denominator);
 
 	wb_thresh = (thresh * (100 - bdi_min_ratio)) / 100;
-- 
2.4.0

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