writeback: remove unused macro DIRTY_FULL_SCOPE

It's introduced but never used. Remove it.

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Miaohe Lin <[email protected]>
Reviewed-by: Jan Kara <[email protected]>
Acked-by: Jens Axboe <[email protected]>
Cc: Bart Van Assche <[email protected]>
Cc: David Howells <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: NeilBrown <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: zhanglianjie <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

include/linux/writeback.h

@@ -17,20 +17,12 @@ struct bio;
 DECLARE_PER_CPU(int, dirty_throttle_leaks);
 
 /*
- * The 1/4 region under the global dirty thresh is for smooth dirty throttling:
- *
- *	(thresh - thresh/DIRTY_FULL_SCOPE, thresh)
- *
- * Further beyond, all dirtier tasks will enter a loop waiting (possibly long
- * time) for the dirty pages to drop, unless written enough pages.
- *
  * The global dirty threshold is normally equal to the global dirty limit,
  * except when the system suddenly allocates a lot of anonymous memory and
  * knocks down the global dirty threshold quickly, in which case the global
  * dirty limit will follow down slowly to prevent livelocking all dirtier tasks.
  */
 #define DIRTY_SCOPE		8
-#define DIRTY_FULL_SCOPE	(DIRTY_SCOPE / 2)
 
 struct backing_dev_info;