writeback: introduce writeback_control.inodes_written
The flusher works on dirty inodes in batches, and may quit prematurely
if the batch of inodes happen to be metadata-only dirtied: in this case
wbc->nr_to_write won't be decreased at all, which stands for "no pages
written" but also mis-interpreted as "no progress".
So introduce writeback_control.inodes_written to count the inodes get
cleaned from VFS POV. A non-zero value means there are some progress on
writeback, in which case more writeback can be tried.
Acked-by: Jan Kara <jack@suse.cz>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index 3f6542c..7df9026 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -34,6 +34,7 @@
long nr_to_write; /* Write this many pages, and decrement
this for each page written */
long pages_skipped; /* Pages which were not written */
+ long inodes_written; /* # of inodes written (at least) */
/*
* For a_ops->writepages(): is start or end are non-zero then this is