+ writeback-the-kupdate-expire-timestamp-should-be-a-moving-target.patch added to -mm tree

+ writeback-the-kupdate-expire-timestamp-should-be-a-moving-target.patch added to -mm tree

[akpm]

The patch titled
     writeback: the kupdate expire timestamp should be a moving target
has been added to the -mm tree.  Its filename is
     writeback-the-kupdate-expire-timestamp-should-be-a-moving-target.patch

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------------------------------------------------------
Subject: writeback: the kupdate expire timestamp should be a moving target
From: Wu Fengguang <fengguang.wu@intel.com>

Dynamically compute the dirty expire timestamp at queue_io() time.

writeback_control.older_than_this used to be determined at entrance to the
kupdate writeback work.  This _static_ timestamp may go stale if the
kupdate work runs on and on.  The flusher may then stuck with some old
busy inodes, never considering newly expired inodes thereafter.

This has two possible problems:

- It is unfair for a large dirty inode to delay (for a long time) the
  writeback of small dirty inodes.

- As time goes by, the large and busy dirty inode may contain only
  _freshly_ dirtied pages. Ignoring newly expired dirty inodes risks
  delaying the expired dirty pages to the end of LRU lists, triggering
  the evil pageout(). Nevertheless this patch merely addresses part
  of the problem.

v2: keep policy changes inside wb_writeback() and keep the
wbc.older_than_this visibility as suggested by Dave.

Signed-off-by: Itaru Kitayama <kitayama@cl.bb4u.ne.jp>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Cc: Dave Chinner <david@fromorbit.com>
Acked-by: Jan Kara <jack@suse.cz>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/fs-writeback.c |   11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff -puN fs/fs-writeback.c~writeback-the-kupdate-expire-timestamp-should-be-a-moving-target fs/fs-writeback.c
--- a/fs/fs-writeback.c~writeback-the-kupdate-expire-timestamp-should-be-a-moving-target
+++ a/fs/fs-writeback.c
@@ -661,11 +661,6 @@ static long wb_writeback(struct bdi_writ
 	long write_chunk;
 	struct inode *inode;
 
-	if (wbc.for_kupdate) {
-		wbc.older_than_this = &oldest_jif;
-		oldest_jif = jiffies -
-				msecs_to_jiffies(dirty_expire_interval * 10);
-	}
 	if (!wbc.range_cyclic) {
 		wbc.range_start = 0;
 		wbc.range_end = LLONG_MAX;
@@ -714,6 +709,12 @@ static long wb_writeback(struct bdi_writ
 		if (work->for_background && !over_bground_thresh())
 			break;
 
+		if (work->for_kupdate) {
+			oldest_jif = jiffies -
+				msecs_to_jiffies(dirty_expire_interval * 10);
+			wbc.older_than_this = &oldest_jif;
+		}
+
 		wbc.more_io = 0;
 		wbc.nr_to_write = write_chunk;
 		wbc.pages_skipped = 0;
_

Patches currently in -mm which might be from fengguang.wu@intel.com are

mm-per-node-vmstat-show-proper-vmstats.patch
mm-per-node-vmstat-show-proper-vmstats-fix.patch
writeback-pass-writeback_control-down-to-move_expired_inodes.patch
writeback-introduce-writeback_controlinodes_cleaned.patch
writeback-try-more-writeback-as-long-as-something-was-written.patch
writeback-the-kupdate-expire-timestamp-should-be-a-moving-target.patch
writeback-sync-expired-inodes-first-in-background-writeback.patch
writeback-sync-expired-inodes-first-in-background-writeback-fix.patch
writeback-refill-b_io-iff-empty.patch