writeback: introduce wbc.for_background
It will lower the flush priority for NFS, and maybe more in future.
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index 66ebddc..705f01f 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -49,6 +49,7 @@
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 */