writeback: remove unused macro DIRTY_FULL_SCOPE

It's introduced but never used. Remove it.

Link: https://lkml.kernel.org/r/20220909025711.32012-1-linmiaohe@huawei.com
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Jens Axboe <axboe@kernel.dk>
Cc: Bart Van Assche <bvanassche@acm.org>
Cc: David Howells <dhowells@redhat.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: NeilBrown <neilb@suse.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: zhanglianjie <zhanglianjie@uniontech.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

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;