f2fs: init dirty_secmap incorrectly

section is dirty, but dirty_secmap may not set
Reported-by: Jia Yang <jiayang5@huawei.com>
Fixes: da52f8ad ("f2fs: get the right gc victim section when section has several segments")
Cc: <stable@vger.kernel.org>
Signed-off-by: Jack Qiu <jack.qiu@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/segment.c

@@ -4551,7 +4551,7 @@ static void init_dirty_segmap(struct f2fs_sb_info *sbi)
 		return;
 
 	mutex_lock(&dirty_i->seglist_lock);
-	for (segno = 0; segno < MAIN_SECS(sbi); segno += blks_per_sec) {
+	for (segno = 0; segno < MAIN_SEGS(sbi); segno += sbi->segs_per_sec) {
 		valid_blocks = get_valid_blocks(sbi, segno, true);
 		secno = GET_SEC_FROM_SEG(sbi, segno);