writeback: add bdi_dirty_limit() kernel-doc
Clarify the bdi_dirty_limit() comment.
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Jan Kara <jack@suse.cz>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 955fe35..b8be623 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -437,10 +437,17 @@
*pdirty = dirty;
}
-/*
+/**
* bdi_dirty_limit - @bdi's share of dirty throttling threshold
+ * @bdi: the backing_dev_info to query
+ * @dirty: global dirty limit in pages
*
- * Allocate high/low dirty limits to fast/slow devices, in order to prevent
+ * Returns @bdi's dirty limit in pages. The term "dirty" in the context of
+ * dirty balancing includes all PG_dirty, PG_writeback and NFS unstable pages.
+ * And the "limit" in the name is not seriously taken as hard limit in
+ * balance_dirty_pages().
+ *
+ * It allocates high/low dirty limits to fast/slow devices, in order to prevent
* - starving fast devices
* - piling up dirty pages (that will take long time to sync) on slow devices
*