f2fs: add GC_URGENT_LOW mode in gc_urgent

Added a new gc_urgent mode, GC_URGENT_LOW, in which mode
F2FS will lower the bar of checking idle in order to
process outstanding discard commands and GC a little bit
aggressively.

Signed-off-by: Daeho Jeong <daehojeong@google.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/gc.c

@@ -82,7 +82,7 @@ static int gc_thread_func(void *data)
 		 * invalidated soon after by user update or deletion.
 		 * So, I'd like to wait some time to collect dirty segments.
 		 */
-		if (sbi->gc_mode == GC_URGENT) {
+		if (sbi->gc_mode == GC_URGENT_HIGH) {
 			wait_ms = gc_th->urgent_sleep_time;
 			down_write(&sbi->gc_lock);
 			goto do_gc;
@@ -176,7 +176,7 @@ static int select_gc_type(struct f2fs_sb_info *sbi, int gc_type)
 		gc_mode = GC_CB;
 		break;
 	case GC_IDLE_GREEDY:
-	case GC_URGENT:
+	case GC_URGENT_HIGH:
 		gc_mode = GC_GREEDY;
 		break;
 	}
@@ -211,7 +211,7 @@ static void select_policy(struct f2fs_sb_info *sbi, int gc_type,
 	 * foreground GC and urgent GC cases.
 	 */
 	if (gc_type != FG_GC &&
-			(sbi->gc_mode != GC_URGENT) &&
+			(sbi->gc_mode != GC_URGENT_HIGH) &&
 			p->max_search > sbi->max_victim_search)
 		p->max_search = sbi->max_victim_search;