f2fs: set ioprio of GC kthread to idle

GC should run conservatively as possible to reduce latency spikes to the user.

Setting ioprio to idle class will allow the kernel to schedule GC thread's I/O
to not affect any other processes' I/O requests.

Signed-off-by: Park Ju Hyung <qkrwngud825@gmail.com>
Signed-off-by: Danny Lin <danny@kdrag0n.dev>

fs/f2fs/gc.c

@@ -195,7 +195,9 @@ int f2fs_start_gc_thread(struct f2fs_sb_info *sbi)
 		sbi->gc_thread = NULL;
 		return err;
 	}
-
+	set_task_ioprio(sbi->gc_thread->f2fs_gc_task,
+			IOPRIO_PRIO_VALUE(IOPRIO_CLASS_IDLE, 0));
+			
 	return 0;
 }