2 files changed, 21 insertions, 13 deletions

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 227ff12257f3..50445cf0b83a 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -30,15 +30,6 @@
 #include "internal.h"
 
 /*
- * The maximum number of pages to writeout in a single bdi flush/kupdate
- * operation.  We do this so we don't hold I_SYNC against an inode for
- * enormous amounts of time, which would block a userspace task which has
- * been forced to throttle against that inode.  Also, the code reevaluates
- * the dirty each time it has written this many pages.
- */
-#define MAX_WRITEBACK_PAGES     1024L
-
-/*
  * Passed into wb_writeback(), essentially a subset of writeback_control
  */
 struct wb_writeback_work {
@@ -515,7 +506,8 @@ static bool pin_sb_for_writeback(struct super_block *sb)
         return false;
 }
 
-static long writeback_chunk_size(struct wb_writeback_work *work)
+static long writeback_chunk_size(struct backing_dev_info *bdi,
+                                 struct wb_writeback_work *work)
 {
         long pages;
 
@@ -534,8 +526,13 @@ static long writeback_chunk_size(struct wb_writeback_work *work)
          */
         if (work->sync_mode == WB_SYNC_ALL || work->tagged_writepages)
                 pages = LONG_MAX;
-        else
-                pages = min(MAX_WRITEBACK_PAGES, work->nr_pages);
+        else {
+                pages = min(bdi->avg_write_bandwidth / 2,
+                            global_dirty_limit / DIRTY_SCOPE);
+                pages = min(pages, work->nr_pages);
+                pages = round_down(pages + MIN_WRITEBACK_PAGES,
+                                   MIN_WRITEBACK_PAGES);
+        }
 
         return pages;
 }
@@ -600,7 +597,7 @@ static long writeback_sb_inodes(struct super_block *sb,
                         continue;
                 }
                 __iget(inode);
-                write_chunk = writeback_chunk_size(work);
+                write_chunk = writeback_chunk_size(wb->bdi, work);
                 wbc.nr_to_write = write_chunk;
                 wbc.pages_skipped = 0;
 
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index b625073b80c8..f1bfa12ea246 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -8,6 +8,10 @@
 #include <linux/fs.h>
 
 /*
+ * The 1/4 region under the global dirty thresh is for smooth dirty throttling:
+ *
+ *      (thresh - thresh/DIRTY_FULL_SCOPE, thresh)
+ *
  * The 1/16 region above the global dirty limit will be put to maximum pauses:
  *
  *      (limit, limit + limit/DIRTY_MAXPAUSE_AREA)
@@ -25,9 +29,16 @@
  * knocks down the global dirty threshold quickly, in which case the global
  * dirty limit will follow down slowly to prevent livelocking all dirtier tasks.
  */
+#define DIRTY_SCOPE             8
+#define DIRTY_FULL_SCOPE        (DIRTY_SCOPE / 2)
 #define DIRTY_MAXPAUSE_AREA             16
 #define DIRTY_PASSGOOD_AREA             8
 
+/*
+ * 4MB minimal write chunk size
+ */
+#define MIN_WRITEBACK_PAGES     (4096UL >> (PAGE_CACHE_SHIFT - 10))
+
 struct backing_dev_info;
 
 /*