f2fs: don't overwrite node block by SSR

This patch fixes that SSR can overwrite previous warm node block consisting of
a node chain since the last checkpoint.

Fixes: 5b6c6be2 ("f2fs: use SSR for warm node as well")
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/segment.c

@@ -1163,6 +1163,12 @@ static void update_sit_entry(struct f2fs_sb_info *sbi, block_t blkaddr, int del)
 		if (f2fs_discard_en(sbi) &&
 			!f2fs_test_and_set_bit(offset, se->discard_map))
 			sbi->discard_blks--;
+
+		/* don't overwrite by SSR to keep node chain */
+		if (se->type == CURSEG_WARM_NODE) {
+			if (!f2fs_test_and_set_bit(offset, se->ckpt_valid_map))
+				se->ckpt_valid_blocks++;
+		}
 	} else {
 		if (!f2fs_test_and_clear_bit(offset, se->cur_valid_map)) {
 #ifdef CONFIG_F2FS_CHECK_FS