[PATCH] dirty_writeback_centisecs fixes

This /proc tunable sets the kupdate interval.  It has a couple of problems:

- No way to turn it off completely (userspace dirty memory management
  solutions require this).

- If it has been set to one hour and then the user resets it to five
  seconds, that resetting will not take effect for up to an hour.

Fix that up by providing a sysctl handler.  Setting the tunable to zero now
disables the kupdate function.

1 files changed, 4 insertions, 0 deletions

diff --git a/include/linux/writeback.h b/include/linux/writeback.h
index f316169bb1f7..cb7d5d6a75b0 100644
--- a/include/linux/writeback.h
+++ b/include/linux/writeback.h
@@ -78,6 +78,10 @@ extern int vm_dirty_ratio;
 extern int dirty_writeback_centisecs;
 extern int dirty_expire_centisecs;
 
+struct ctl_table;
+struct file;
+int dirty_writeback_centisecs_handler(struct ctl_table *, int, struct file *, 
+					  void *, size_t *);
 
 void page_writeback_init(void);
 void balance_dirty_pages(struct address_space *mapping);