[PATCH 13/48] writeback: s/bdi/wb/ in mm/page-writeback.c

From: Tejun Heo <tj@kernel.org>
To: axboe@kernel.dk
Cc: linux-kernel@vger.kernel.org, jack@suse.cz, hch@infradead.org,
	hannes@cmpxchg.org, linux-fsdevel@vger.kernel.org,
	vgoyal@redhat.com, lizefan@huawei.com, cgroups@vger.kernel.org,
	linux-mm@kvack.org, mhocko@suse.cz, clm@fb.com,
	fengguang.wu@intel.com, david@fromorbit.com, gthelen@google.com,
	Tejun Heo <tj@kernel.org>
Subject: [PATCH 13/48] writeback: s/bdi/wb/ in mm/page-writeback.c
Date: Mon, 23 Mar 2015 00:54:24 -0400	[thread overview]
Message-ID: <1427086499-15657-14-git-send-email-tj@kernel.org> (raw)
In-Reply-To: <1427086499-15657-1-git-send-email-tj@kernel.org>

Writeback operations will now be per wb (bdi_writeback) instead of
bdi.  Replace the relevant bdi references in symbol names and comments
with wb.  This patch is purely cosmetic and doesn't make any
functional changes.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jens Axboe <axboe@kernel.dk>
---
 mm/page-writeback.c | 270 ++++++++++++++++++++++++++--------------------------
 1 file changed, 134 insertions(+), 136 deletions(-)

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 29fb4f3..c615a15 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -595,7 +595,7 @@ static long long pos_ratio_polynom(unsigned long setpoint,
  *
  * (o) global/bdi setpoints
  *
- * We want the dirty pages be balanced around the global/bdi setpoints.
+ * We want the dirty pages be balanced around the global/wb setpoints.
  * When the number of dirty pages is higher/lower than the setpoint, the
  * dirty position control ratio (and hence task dirty ratelimit) will be
  * decreased/increased to bring the dirty pages back to the setpoint.
@@ -605,8 +605,8 @@ static long long pos_ratio_polynom(unsigned long setpoint,
  *     if (dirty < setpoint) scale up   pos_ratio
  *     if (dirty > setpoint) scale down pos_ratio
  *
- *     if (bdi_dirty < bdi_setpoint) scale up   pos_ratio
- *     if (bdi_dirty > bdi_setpoint) scale down pos_ratio
+ *     if (wb_dirty < wb_setpoint) scale up   pos_ratio
+ *     if (wb_dirty > wb_setpoint) scale down pos_ratio
  *
  *     task_ratelimit = dirty_ratelimit * pos_ratio >> RATELIMIT_CALC_SHIFT
  *
@@ -631,7 +631,7 @@ static long long pos_ratio_polynom(unsigned long setpoint,
  *   0 +------------.------------------.----------------------*------------->
  *           freerun^          setpoint^                 limit^   dirty pages
  *
- * (o) bdi control line
+ * (o) wb control line
  *
  *     ^ pos_ratio
  *     |
@@ -657,27 +657,27 @@ static long long pos_ratio_polynom(unsigned long setpoint,
  *     |                      .                           .
  *     |                      .                             .
  *   0 +----------------------.-------------------------------.------------->
- *                bdi_setpoint^                    x_intercept^
+ *                wb_setpoint^                    x_intercept^
  *
- * The bdi control line won't drop below pos_ratio=1/4, so that bdi_dirty can
+ * The wb control line won't drop below pos_ratio=1/4, so that wb_dirty can
  * be smoothly throttled down to normal if it starts high in situations like
  * - start writing to a slow SD card and a fast disk at the same time. The SD
- *   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
+ *   card's wb_dirty may rush to many times higher than wb_setpoint.
+ * - the wb dirty thresh drops quickly due to change of JBOD workload
  */
 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 wb_thresh,
+				       unsigned long wb_dirty)
 {
 	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;
 	unsigned long setpoint;		/* dirty pages' target balance point */
-	unsigned long bdi_setpoint;
+	unsigned long wb_setpoint;
 	unsigned long span;
 	long long pos_ratio;		/* for scaling up/down the rate limit */
 	long x;
@@ -696,146 +696,145 @@ static unsigned long wb_position_ratio(struct bdi_writeback *wb,
 	/*
 	 * The strictlimit feature is a tool preventing mistrusted filesystems
 	 * from growing a large number of dirty pages before throttling. For
-	 * such filesystems balance_dirty_pages always checks bdi counters
-	 * against bdi limits. Even if global "nr_dirty" is under "freerun".
+	 * such filesystems balance_dirty_pages always checks wb counters
+	 * against wb limits. Even if global "nr_dirty" is under "freerun".
 	 * This is especially important for fuse which sets bdi->max_ratio to
 	 * 1% by default. Without strictlimit feature, fuse writeback may
 	 * consume arbitrary amount of RAM because it is accounted in
 	 * NR_WRITEBACK_TEMP which is not involved in calculating "nr_dirty".
 	 *
 	 * Here, in wb_position_ratio(), we calculate pos_ratio based on
-	 * two values: bdi_dirty and bdi_thresh. Let's consider an example:
+	 * two values: wb_dirty and wb_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.
-	 * wb_dirty_limit(wb, bg_thresh) is about ~4K pages. bdi_setpoint is
-	 * about ~6K pages (as the average of background and throttle bdi
+	 * Then wb_thresh is 1% of 20% of 16GB. This amounts to ~8K pages.
+	 * wb_dirty_limit(wb, bg_thresh) is about ~4K pages. wb_setpoint is
+	 * about ~6K pages (as the average of background and throttle wb
 	 * limits). The 3rd order polynomial will provide positive feedback if
-	 * bdi_dirty is under bdi_setpoint and vice versa.
+	 * wb_dirty is under wb_setpoint and vice versa.
 	 *
 	 * Note, that we cannot use global counters in these calculations
-	 * because we want to throttle process writing to a strictlimit BDI
+	 * because we want to throttle process writing to a strictlimit wb
 	 * much earlier than global "freerun" is reached (~23MB vs. ~2.3GB
 	 * in the example above).
 	 */
 	if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT)) {
-		long long bdi_pos_ratio;
-		unsigned long bdi_bg_thresh;
+		long long wb_pos_ratio;
+		unsigned long wb_bg_thresh;
 
-		if (bdi_dirty < 8)
+		if (wb_dirty < 8)
 			return min_t(long long, pos_ratio * 2,
 				     2 << RATELIMIT_CALC_SHIFT);
 
-		if (bdi_dirty >= bdi_thresh)
+		if (wb_dirty >= wb_thresh)
 			return 0;
 
-		bdi_bg_thresh = div_u64((u64)bdi_thresh * bg_thresh, thresh);
-		bdi_setpoint = dirty_freerun_ceiling(bdi_thresh,
-						     bdi_bg_thresh);
+		wb_bg_thresh = div_u64((u64)wb_thresh * bg_thresh, thresh);
+		wb_setpoint = dirty_freerun_ceiling(wb_thresh, wb_bg_thresh);
 
-		if (bdi_setpoint == 0 || bdi_setpoint == bdi_thresh)
+		if (wb_setpoint == 0 || wb_setpoint == wb_thresh)
 			return 0;
 
-		bdi_pos_ratio = pos_ratio_polynom(bdi_setpoint, bdi_dirty,
-						  bdi_thresh);
+		wb_pos_ratio = pos_ratio_polynom(wb_setpoint, wb_dirty,
+						 wb_thresh);
 
 		/*
-		 * Typically, for strictlimit case, bdi_setpoint << setpoint
-		 * and pos_ratio >> bdi_pos_ratio. In the other words global
+		 * Typically, for strictlimit case, wb_setpoint << setpoint
+		 * and pos_ratio >> wb_pos_ratio. In the other words global
 		 * state ("dirty") is not limiting factor and we have to
-		 * make decision based on bdi counters. But there is an
+		 * make decision based on wb counters. But there is an
 		 * important case when global pos_ratio should get precedence:
 		 * global limits are exceeded (e.g. due to activities on other
-		 * BDIs) while given strictlimit BDI is below limit.
+		 * wb's) while given strictlimit wb is below limit.
 		 *
-		 * "pos_ratio * bdi_pos_ratio" would work for the case above,
+		 * "pos_ratio * wb_pos_ratio" would work for the case above,
 		 * but it would look too non-natural for the case of all
-		 * activity in the system coming from a single strictlimit BDI
+		 * activity in the system coming from a single strictlimit wb
 		 * with bdi->max_ratio == 100%.
 		 *
 		 * Note that min() below somewhat changes the dynamics of the
 		 * control system. Normally, pos_ratio value can be well over 3
-		 * (when globally we are at freerun and bdi is well below bdi
+		 * (when globally we are at freerun and wb is well below wb
 		 * setpoint). Now the maximum pos_ratio in the same situation
 		 * is 2. We might want to tweak this if we observe the control
 		 * system is too slow to adapt.
 		 */
-		return min(pos_ratio, bdi_pos_ratio);
+		return min(pos_ratio, wb_pos_ratio);
 	}
 
 	/*
 	 * We have computed basic pos_ratio above based on global situation. If
-	 * the bdi is over/under its share of dirty pages, we want to scale
+	 * the wb is over/under its share of dirty pages, we want to scale
 	 * pos_ratio further down/up. That is done by the following mechanism.
 	 */
 
 	/*
-	 * bdi setpoint
+	 * wb setpoint
 	 *
-	 *        f(bdi_dirty) := 1.0 + k * (bdi_dirty - bdi_setpoint)
+	 *        f(wb_dirty) := 1.0 + k * (wb_dirty - wb_setpoint)
 	 *
-	 *                        x_intercept - bdi_dirty
+	 *                        x_intercept - wb_dirty
 	 *                     := --------------------------
-	 *                        x_intercept - bdi_setpoint
+	 *                        x_intercept - wb_setpoint
 	 *
-	 * The main bdi control line is a linear function that subjects to
+	 * The main wb control line is a linear function that subjects to
 	 *
-	 * (1) f(bdi_setpoint) = 1.0
-	 * (2) k = - 1 / (8 * write_bw)  (in single bdi case)
-	 *     or equally: x_intercept = bdi_setpoint + 8 * write_bw
+	 * (1) f(wb_setpoint) = 1.0
+	 * (2) k = - 1 / (8 * write_bw)  (in single wb case)
+	 *     or equally: x_intercept = wb_setpoint + 8 * write_bw
 	 *
-	 * For single bdi case, the dirty pages are observed to fluctuate
+	 * For single wb case, the dirty pages are observed to fluctuate
 	 * regularly within range
-	 *        [bdi_setpoint - write_bw/2, bdi_setpoint + write_bw/2]
+	 *        [wb_setpoint - write_bw/2, wb_setpoint + write_bw/2]
 	 * for various filesystems, where (2) can yield in a reasonable 12.5%
 	 * fluctuation range for pos_ratio.
 	 *
-	 * For JBOD case, bdi_thresh (not bdi_dirty!) could fluctuate up to its
+	 * For JBOD case, wb_thresh (not wb_dirty!) could fluctuate up to its
 	 * own size, so move the slope over accordingly and choose a slope that
-	 * yields 100% pos_ratio fluctuation on suddenly doubled bdi_thresh.
+	 * yields 100% pos_ratio fluctuation on suddenly doubled wb_thresh.
 	 */
-	if (unlikely(bdi_thresh > thresh))
-		bdi_thresh = thresh;
+	if (unlikely(wb_thresh > thresh))
+		wb_thresh = thresh;
 	/*
-	 * It's very possible that bdi_thresh is close to 0 not because the
+	 * It's very possible that wb_thresh is close to 0 not because the
 	 * device is slow, but that it has remained inactive for long time.
 	 * Honour such devices a reasonable good (hopefully IO efficient)
 	 * threshold, so that the occasional writes won't be blocked and active
 	 * writes can rampup the threshold quickly.
 	 */
-	bdi_thresh = max(bdi_thresh, (limit - dirty) / 8);
+	wb_thresh = max(wb_thresh, (limit - dirty) / 8);
 	/*
-	 * scale global setpoint to bdi's:
-	 *	bdi_setpoint = setpoint * bdi_thresh / thresh
+	 * scale global setpoint to wb's:
+	 *	wb_setpoint = setpoint * wb_thresh / thresh
 	 */
-	x = div_u64((u64)bdi_thresh << 16, thresh + 1);
-	bdi_setpoint = setpoint * (u64)x >> 16;
+	x = div_u64((u64)wb_thresh << 16, thresh + 1);
+	wb_setpoint = setpoint * (u64)x >> 16;
 	/*
-	 * Use span=(8*write_bw) in single bdi case as indicated by
-	 * (thresh - bdi_thresh ~= 0) and transit to bdi_thresh in JBOD case.
+	 * Use span=(8*write_bw) in single wb case as indicated by
+	 * (thresh - wb_thresh ~= 0) and transit to wb_thresh in JBOD case.
 	 *
-	 *        bdi_thresh                    thresh - bdi_thresh
-	 * span = ---------- * (8 * write_bw) + ------------------- * bdi_thresh
-	 *          thresh                            thresh
+	 *        wb_thresh                    thresh - wb_thresh
+	 * span = --------- * (8 * write_bw) + ------------------ * wb_thresh
+	 *         thresh                           thresh
 	 */
-	span = (thresh - bdi_thresh + 8 * write_bw) * (u64)x >> 16;
-	x_intercept = bdi_setpoint + span;
+	span = (thresh - wb_thresh + 8 * write_bw) * (u64)x >> 16;
+	x_intercept = wb_setpoint + span;
 
-	if (bdi_dirty < x_intercept - span / 4) {
-		pos_ratio = div64_u64(pos_ratio * (x_intercept - bdi_dirty),
-				    x_intercept - bdi_setpoint + 1);
+	if (wb_dirty < x_intercept - span / 4) {
+		pos_ratio = div64_u64(pos_ratio * (x_intercept - wb_dirty),
+				    x_intercept - wb_setpoint + 1);
 	} else
 		pos_ratio /= 4;
 
 	/*
-	 * bdi reserve area, safeguard against dirty pool underrun and disk idle
+	 * wb reserve area, safeguard against dirty pool underrun and disk idle
 	 * It may push the desired control point of global dirty pages higher
 	 * than setpoint.
 	 */
-	x_intercept = bdi_thresh / 2;
-	if (bdi_dirty < x_intercept) {
-		if (bdi_dirty > x_intercept / 8)
-			pos_ratio = div_u64(pos_ratio * x_intercept, bdi_dirty);
+	x_intercept = wb_thresh / 2;
+	if (wb_dirty < x_intercept) {
+		if (wb_dirty > x_intercept / 8)
+			pos_ratio = div_u64(pos_ratio * x_intercept, wb_dirty);
 		else
 			pos_ratio *= 8;
 	}
@@ -943,17 +942,17 @@ static void global_update_bandwidth(unsigned long thresh,
 }
 
 /*
- * Maintain bdi->dirty_ratelimit, the base dirty throttle rate.
+ * Maintain wb->dirty_ratelimit, the base dirty throttle rate.
  *
- * Normal bdi tasks will be curbed at or below it in long term.
+ * Normal wb 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 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 wb_thresh,
+				      unsigned long wb_dirty,
 				      unsigned long dirtied,
 				      unsigned long elapsed)
 {
@@ -976,7 +975,7 @@ static void wb_update_dirty_ratelimit(struct bdi_writeback *wb,
 	dirty_rate = (dirtied - wb->dirtied_stamp) * HZ / elapsed;
 
 	pos_ratio = wb_position_ratio(wb, thresh, bg_thresh, dirty,
-				      bdi_thresh, bdi_dirty);
+				      wb_thresh, wb_dirty);
 	/*
 	 * task_ratelimit reflects each dd's dirty rate for the past 200ms.
 	 */
@@ -986,7 +985,7 @@ static void wb_update_dirty_ratelimit(struct bdi_writeback *wb,
 
 	/*
 	 * A linear estimation of the "balanced" throttle rate. The theory is,
-	 * if there are N dd tasks, each throttled at task_ratelimit, the bdi's
+	 * if there are N dd tasks, each throttled at task_ratelimit, the wb's
 	 * dirty_rate will be measured to be (N * task_ratelimit). So the below
 	 * formula will yield the balanced rate limit (write_bw / N).
 	 *
@@ -1025,7 +1024,7 @@ static void wb_update_dirty_ratelimit(struct bdi_writeback *wb,
 	/*
 	 * We could safely do this and return immediately:
 	 *
-	 *	bdi->dirty_ratelimit = balanced_dirty_ratelimit;
+	 *	wb->dirty_ratelimit = balanced_dirty_ratelimit;
 	 *
 	 * However to get a more stable dirty_ratelimit, the below elaborated
 	 * code makes use of task_ratelimit to filter out singular points and
@@ -1059,22 +1058,22 @@ static void wb_update_dirty_ratelimit(struct bdi_writeback *wb,
 	step = 0;
 
 	/*
-	 * For strictlimit case, calculations above were based on bdi counters
+	 * For strictlimit case, calculations above were based on wb counters
 	 * 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".
+	 * Hence, to calculate "step" properly, we have to use wb_dirty as
+	 * "dirty" and wb_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
+	 * We rampup dirty_ratelimit forcibly if wb_dirty is low because
+	 * it's possible that wb_thresh is close to zero due to inactivity
 	 * of backing device (see the implementation of wb_dirty_limit()).
 	 */
 	if (unlikely(wb->bdi->capabilities & BDI_CAP_STRICTLIMIT)) {
-		dirty = bdi_dirty;
-		if (bdi_dirty < 8)
-			setpoint = bdi_dirty + 1;
+		dirty = wb_dirty;
+		if (wb_dirty < 8)
+			setpoint = wb_dirty + 1;
 		else
-			setpoint = (bdi_thresh +
+			setpoint = (wb_thresh +
 				    wb_dirty_limit(wb, bg_thresh)) / 2;
 	}
 
@@ -1116,8 +1115,8 @@ 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 wb_thresh,
+			   unsigned long wb_dirty,
 			   unsigned long start_time)
 {
 	unsigned long now = jiffies;
@@ -1144,7 +1143,7 @@ void __wb_update_bandwidth(struct bdi_writeback *wb,
 	if (thresh) {
 		global_update_bandwidth(thresh, dirty, now);
 		wb_update_dirty_ratelimit(wb, thresh, bg_thresh, dirty,
-					  bdi_thresh, bdi_dirty,
+					  wb_thresh, wb_dirty,
 					  dirtied, elapsed);
 	}
 	wb_update_write_bandwidth(wb, elapsed, written);
@@ -1159,15 +1158,15 @@ 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 wb_thresh,
+				unsigned long wb_dirty,
 				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,
-			      bdi_thresh, bdi_dirty, start_time);
+			      wb_thresh, wb_dirty, start_time);
 	spin_unlock(&wb->list_lock);
 }
 
@@ -1189,7 +1188,7 @@ static unsigned long dirty_poll_interval(unsigned long dirty,
 }
 
 static unsigned long wb_max_pause(struct bdi_writeback *wb,
-				      unsigned long bdi_dirty)
+				  unsigned long wb_dirty)
 {
 	unsigned long bw = wb->avg_write_bandwidth;
 	unsigned long t;
@@ -1201,7 +1200,7 @@ static unsigned long wb_max_pause(struct bdi_writeback *wb,
 	 *
 	 * 8 serves as the safety ratio.
 	 */
-	t = bdi_dirty / (1 + bw / roundup_pow_of_two(1 + HZ / 8));
+	t = wb_dirty / (1 + bw / roundup_pow_of_two(1 + HZ / 8));
 	t++;
 
 	return min_t(unsigned long, t, MAX_PAUSE);
@@ -1285,31 +1284,31 @@ static long wb_min_pause(struct bdi_writeback *wb,
 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)
+				   unsigned long *wb_dirty,
+				   unsigned long *wb_thresh,
+				   unsigned long *wb_bg_thresh)
 {
 	unsigned long wb_reclaimable;
 
 	/*
-	 * bdi_thresh is not treated as some limiting factor as
+	 * wb_thresh is not treated as some limiting factor as
 	 * dirty_thresh, due to reasons
-	 * - in JBOD setup, bdi_thresh can fluctuate a lot
+	 * - in JBOD setup, wb_thresh can fluctuate a lot
 	 * - in a system with HDD and USB key, the USB key may somehow
-	 *   go into state (bdi_dirty >> bdi_thresh) either because
-	 *   bdi_dirty starts high, or because bdi_thresh drops low.
+	 *   go into state (wb_dirty >> wb_thresh) either because
+	 *   wb_dirty starts high, or because wb_thresh drops low.
 	 *   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
+	 *   dirtiers for 100 seconds until wb_dirty drops under
+	 *   wb_thresh. Instead the auxiliary wb control line in
 	 *   wb_position_ratio() will let the dirtier task progress
-	 *   at some rate <= (write_bw / 2) for bringing down bdi_dirty.
+	 *   at some rate <= (write_bw / 2) for bringing down wb_dirty.
 	 */
-	*bdi_thresh = wb_dirty_limit(wb, dirty_thresh);
+	*wb_thresh = wb_dirty_limit(wb, dirty_thresh);
 
-	if (bdi_bg_thresh)
-		*bdi_bg_thresh = dirty_thresh ? div_u64((u64)*bdi_thresh *
-							background_thresh,
-							dirty_thresh) : 0;
+	if (wb_bg_thresh)
+		*wb_bg_thresh = dirty_thresh ? div_u64((u64)*wb_thresh *
+						       background_thresh,
+						       dirty_thresh) : 0;
 
 	/*
 	 * In order to avoid the stacked BDI deadlock we need
@@ -1321,12 +1320,12 @@ static inline void wb_dirty_limits(struct bdi_writeback *wb,
 	 * actually dirty; with m+n sitting in the percpu
 	 * deltas.
 	 */
-	if (*bdi_thresh < 2 * wb_stat_error(wb)) {
+	if (*wb_thresh < 2 * wb_stat_error(wb)) {
 		wb_reclaimable = wb_stat_sum(wb, WB_RECLAIMABLE);
-		*bdi_dirty = wb_reclaimable + wb_stat_sum(wb, WB_WRITEBACK);
+		*wb_dirty = wb_reclaimable + wb_stat_sum(wb, WB_WRITEBACK);
 	} else {
 		wb_reclaimable = wb_stat(wb, WB_RECLAIMABLE);
-		*bdi_dirty = wb_reclaimable + wb_stat(wb, WB_WRITEBACK);
+		*wb_dirty = wb_reclaimable + wb_stat(wb, WB_WRITEBACK);
 	}
 }
 
@@ -1360,9 +1359,9 @@ static void balance_dirty_pages(struct address_space *mapping,
 
 	for (;;) {
 		unsigned long now = jiffies;
-		unsigned long uninitialized_var(bdi_thresh);
+		unsigned long uninitialized_var(wb_thresh);
 		unsigned long thresh;
-		unsigned long uninitialized_var(bdi_dirty);
+		unsigned long uninitialized_var(wb_dirty);
 		unsigned long dirty;
 		unsigned long bg_thresh;
 
@@ -1380,10 +1379,10 @@ static void balance_dirty_pages(struct address_space *mapping,
 
 		if (unlikely(strictlimit)) {
 			wb_dirty_limits(wb, dirty_thresh, background_thresh,
-					&bdi_dirty, &bdi_thresh, &bg_thresh);
+					&wb_dirty, &wb_thresh, &bg_thresh);
 
-			dirty = bdi_dirty;
-			thresh = bdi_thresh;
+			dirty = wb_dirty;
+			thresh = wb_thresh;
 		} else {
 			dirty = nr_dirty;
 			thresh = dirty_thresh;
@@ -1393,10 +1392,10 @@ static void balance_dirty_pages(struct address_space *mapping,
 		/*
 		 * Throttle it only when the background writeback cannot
 		 * catch-up. This avoids (excessively) small writeouts
-		 * when the bdi limits are ramping up in case of !strictlimit.
+		 * when the wb limits are ramping up in case of !strictlimit.
 		 *
-		 * In strictlimit case make decision based on the bdi counters
-		 * and limits. Small writeouts when the bdi limits are ramping
+		 * In strictlimit case make decision based on the wb counters
+		 * and limits. Small writeouts when the wb limits are ramping
 		 * up are the price we consciously pay for strictlimit-ing.
 		 */
 		if (dirty <= dirty_freerun_ceiling(thresh, bg_thresh)) {
@@ -1412,24 +1411,23 @@ static void balance_dirty_pages(struct address_space *mapping,
 
 		if (!strictlimit)
 			wb_dirty_limits(wb, dirty_thresh, background_thresh,
-					&bdi_dirty, &bdi_thresh, NULL);
+					&wb_dirty, &wb_thresh, NULL);
 
-		dirty_exceeded = (bdi_dirty > bdi_thresh) &&
+		dirty_exceeded = (wb_dirty > wb_thresh) &&
 				 ((nr_dirty > dirty_thresh) || strictlimit);
 		if (dirty_exceeded && !wb->dirty_exceeded)
 			wb->dirty_exceeded = 1;
 
 		wb_update_bandwidth(wb, dirty_thresh, background_thresh,
-				    nr_dirty, bdi_thresh, bdi_dirty,
-				    start_time);
+				    nr_dirty, wb_thresh, wb_dirty, start_time);
 
 		dirty_ratelimit = wb->dirty_ratelimit;
 		pos_ratio = wb_position_ratio(wb, dirty_thresh,
 					      background_thresh, nr_dirty,
-					      bdi_thresh, bdi_dirty);
+					      wb_thresh, wb_dirty);
 		task_ratelimit = ((u64)dirty_ratelimit * pos_ratio) >>
 							RATELIMIT_CALC_SHIFT;
-		max_pause = wb_max_pause(wb, bdi_dirty);
+		max_pause = wb_max_pause(wb, wb_dirty);
 		min_pause = wb_min_pause(wb, max_pause,
 					 task_ratelimit, dirty_ratelimit,
 					 &nr_dirtied_pause);
@@ -1455,8 +1453,8 @@ static void balance_dirty_pages(struct address_space *mapping,
 						  dirty_thresh,
 						  background_thresh,
 						  nr_dirty,
-						  bdi_thresh,
-						  bdi_dirty,
+						  wb_thresh,
+						  wb_dirty,
 						  dirty_ratelimit,
 						  task_ratelimit,
 						  pages_dirtied,
@@ -1484,8 +1482,8 @@ pause:
 					  dirty_thresh,
 					  background_thresh,
 					  nr_dirty,
-					  bdi_thresh,
-					  bdi_dirty,
+					  wb_thresh,
+					  wb_dirty,
 					  dirty_ratelimit,
 					  task_ratelimit,
 					  pages_dirtied,
@@ -1508,15 +1506,15 @@ pause:
 
 		/*
 		 * In the case of an unresponding NFS server and the NFS dirty
-		 * pages exceeds dirty_thresh, give the other good bdi's a pipe
+		 * pages exceeds dirty_thresh, give the other good wb's a pipe
 		 * to go through, so that tasks on them still remain responsive.
 		 *
 		 * In theory 1 page is enough to keep the comsumer-producer
 		 * pipe going: the flusher cleans 1 page => the task dirties 1
-		 * more page. However bdi_dirty has accounting errors.  So use
+		 * more page. However wb_dirty has accounting errors.  So use
 		 * the larger and more IO friendly wb_stat_error.
 		 */
-		if (bdi_dirty <= wb_stat_error(wb))
+		if (wb_dirty <= wb_stat_error(wb))
 			break;
 
 		if (fatal_signal_pending(current))
-- 
2.1.0

