f2fs: stop issuing discard immediately if there is queued IO

For background discard policy, even if there is queued user IO, still
we will check max_requests times for next discard entry, it is unneeded,
let's just stop this round submission immediately.
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/segment.c

@@ -1188,7 +1188,7 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi,
 	struct list_head *pend_list;
 	struct discard_cmd *dc, *tmp;
 	struct blk_plug plug;
-	int i, iter = 0, issued = 0;
+	int i, issued = 0;
 	bool io_interrupted = false;
 
 	for (i = MAX_PLIST_NUM - 1; i >= 0; i--) {
@@ -1209,20 +1209,19 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi,
 			if (dpolicy->io_aware && i < dpolicy->io_aware_gran &&
 								!is_idle(sbi)) {
 				io_interrupted = true;
-				goto skip;
+				break;
 			}
 
 			__submit_discard_cmd(sbi, dpolicy, dc);
-			issued++;
-skip:
-			if (++iter >= dpolicy->max_requests)
+
+			if (++issued >= dpolicy->max_requests)
 				break;
 		}
 		blk_finish_plug(&plug);
 next:
 		mutex_unlock(&dcc->cmd_lock);
 
-		if (iter >= dpolicy->max_requests)
+		if (issued >= dpolicy->max_requests || io_interrupted)
 			break;
 	}