f2fs: fix normal discard process

In the DPOLICY_BG mode, there is a conflict between
the two conditions "i + 1 < dpolicy->granularity" and
"i < DEFAULT_DISCARD_GRANULARITY". If i = 15, the first
condition is false, it will enter the second condition
and dispatch all small granularity discards in function
 __issue_discard_cmd_orderly. The restrictive effect
of the first condition to small discards will be
invalidated. These two conditions should align.

Fixes: 20ee4382 ("f2fs: issue small discard by LBA order")
Signed-off-by: Dongdong Zhang <zhangdongdong1@oppo.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/segment.c

@@ -1448,7 +1448,7 @@ static int __issue_discard_cmd(struct f2fs_sb_info *sbi,
 		if (i + 1 < dpolicy->granularity)
 			break;
 
-		if (i < DEFAULT_DISCARD_GRANULARITY && dpolicy->ordered)
+		if (i + 1 < DEFAULT_DISCARD_GRANULARITY && dpolicy->ordered)
 			return __issue_discard_cmd_orderly(sbi, dpolicy);
 
 		pend_list = &dcc->pend_list[i];