[PATCH 6/6] writeback: introduce wbc.for_background

[Wu Fengguang]

It will lower the flush priority for NFS, and maybe more in future.

CC: Trond Myklebust <Trond.Myklebust@xxxxxxxxxx>
Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx>
---
 fs/fs-writeback.c         |    1 +
 fs/nfs/write.c            |    2 +-
 include/linux/writeback.h |    1 +
 3 files changed, 3 insertions(+), 1 deletion(-)

--- linux.orig/fs/fs-writeback.c	2009-11-27 18:55:11.000000000 +0800
+++ linux/fs/fs-writeback.c	2009-11-27 18:55:17.000000000 +0800
@@ -730,6 +730,7 @@ static long wb_writeback(struct bdi_writ
 		.sync_mode		= args->sync_mode,
 		.older_than_this	= NULL,
 		.for_kupdate		= args->for_kupdate,
+		.for_background		= args->for_background,
 		.range_cyclic		= args->range_cyclic,
 	};
 	unsigned long oldest_jif;
--- linux.orig/include/linux/writeback.h	2009-11-27 16:35:00.000000000 +0800
+++ linux/include/linux/writeback.h	2009-11-27 18:55:17.000000000 +0800
@@ -49,6 +49,7 @@ struct writeback_control {
 	unsigned nonblocking:1;		/* Don't get stuck on request queues */
 	unsigned encountered_congestion:1; /* An output: a queue is full */
 	unsigned for_kupdate:1;		/* A kupdate writeback */
+	unsigned for_background:1;	/* A background writeback */
 	unsigned for_reclaim:1;		/* Invoked from the page allocator */
 	unsigned range_cyclic:1;	/* range_start is cyclic */
 	unsigned more_io:1;		/* more io to be dispatched */
--- linux.orig/fs/nfs/write.c	2009-11-19 16:00:50.000000000 +0800
+++ linux/fs/nfs/write.c	2009-11-27 18:55:17.000000000 +0800
@@ -178,7 +178,7 @@ static int wb_priority(struct writeback_
 {
 	if (wbc->for_reclaim)
 		return FLUSH_HIGHPRI | FLUSH_STABLE;
-	if (wbc->for_kupdate)
+	if (wbc->for_kupdate || wbc->for_background)
 		return FLUSH_LOWPRI;
 	return 0;
 }


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