1 files changed, 33 insertions, 8 deletions

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 2df6fb174983..7ff2290cf43d 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -387,8 +387,7 @@ static unsigned long global_dirtyable_memory(void)
  * Calculate @dtc->thresh and ->bg_thresh considering
  * vm_dirty_{bytes|ratio} and dirty_background_{bytes|ratio}.  The caller
  * must ensure that @dtc->avail is set before calling this function.  The
- * dirty limits will be lifted by 1/4 for PF_LESS_THROTTLE (ie. nfsd) and
- * real-time tasks.
+ * dirty limits will be lifted by 1/4 for real-time tasks.
  */
 static void domain_dirty_limits(struct dirty_throttle_control *dtc)
 {
@@ -436,7 +435,7 @@ static void domain_dirty_limits(struct dirty_throttle_control *dtc)
 	if (bg_thresh >= thresh)
 		bg_thresh = thresh / 2;
 	tsk = current;
-	if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk)) {
+	if (rt_task(tsk)) {
 		bg_thresh += bg_thresh / 4 + global_wb_domain.dirty_limit / 32;
 		thresh += thresh / 4 + global_wb_domain.dirty_limit / 32;
 	}
@@ -486,7 +485,7 @@ static unsigned long node_dirty_limit(struct pglist_data *pgdat)
 	else
 		dirty = vm_dirty_ratio * node_memory / 100;
 
-	if (tsk->flags & PF_LESS_THROTTLE || rt_task(tsk))
+	if (rt_task(tsk))
 		dirty += dirty / 4;
 
 	return dirty;
@@ -1653,8 +1652,12 @@ static void balance_dirty_pages(struct bdi_writeback *wb,
 		if (dirty <= dirty_freerun_ceiling(thresh, bg_thresh) &&
 		    (!mdtc ||
 		     m_dirty <= dirty_freerun_ceiling(m_thresh, m_bg_thresh))) {
-			unsigned long intv = dirty_poll_interval(dirty, thresh);
-			unsigned long m_intv = ULONG_MAX;
+			unsigned long intv;
+			unsigned long m_intv;
+
+free_running:
+			intv = dirty_poll_interval(dirty, thresh);
+			m_intv = ULONG_MAX;
 
 			current->dirty_paused_when = now;
 			current->nr_dirtied = 0;
@@ -1673,9 +1676,20 @@ static void balance_dirty_pages(struct bdi_writeback *wb,
 		 * Calculate global domain's pos_ratio and select the
 		 * global dtc by default.
 		 */
-		if (!strictlimit)
+		if (!strictlimit) {
 			wb_dirty_limits(gdtc);
 
+			if ((current->flags & PF_LOCAL_THROTTLE) &&
+			    gdtc->wb_dirty <
+			    dirty_freerun_ceiling(gdtc->wb_thresh,
+						  gdtc->wb_bg_thresh))
+				/*
+				 * LOCAL_THROTTLE tasks must not be throttled
+				 * when below the per-wb freerun ceiling.
+				 */
+				goto free_running;
+		}
+
 		dirty_exceeded = (gdtc->wb_dirty > gdtc->wb_thresh) &&
 			((gdtc->dirty > gdtc->thresh) || strictlimit);
 
@@ -1689,9 +1703,20 @@ static void balance_dirty_pages(struct bdi_writeback *wb,
 			 * both global and memcg domains.  Choose the one
 			 * w/ lower pos_ratio.
 			 */
-			if (!strictlimit)
+			if (!strictlimit) {
 				wb_dirty_limits(mdtc);
 
+				if ((current->flags & PF_LOCAL_THROTTLE) &&
+				    mdtc->wb_dirty <
+				    dirty_freerun_ceiling(mdtc->wb_thresh,
+							  mdtc->wb_bg_thresh))
+					/*
+					 * LOCAL_THROTTLE tasks must not be
+					 * throttled when below the per-wb
+					 * freerun ceiling.
+					 */
+					goto free_running;
+			}
 			dirty_exceeded |= (mdtc->wb_dirty > mdtc->wb_thresh) &&
 				((mdtc->dirty > mdtc->thresh) || strictlimit);