f2fs: add undiscard blocks stat

This patch adds to account undiscard blocks.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
diff --git a/fs/f2fs/debug.c b/fs/f2fs/debug.c
index 692beff..6102737 100644
--- a/fs/f2fs/debug.c
+++ b/fs/f2fs/debug.c
@@ -69,6 +69,7 @@ static void update_general_status(struct f2fs_sb_info *sbi)
 			atomic_read(&SM_I(sbi)->dcc_info->issing_discard);
 		si->nr_discard_cmd =
 			atomic_read(&SM_I(sbi)->dcc_info->discard_cmd_cnt);
+		si->undiscard_blks = SM_I(sbi)->dcc_info->undiscard_blks;
 	}
 	si->total_count = (int)sbi->user_block_count / sbi->blocks_per_seg;
 	si->rsvd_segs = reserved_segments(sbi);
@@ -348,11 +349,11 @@ static int stat_show(struct seq_file *s, void *v)
 				si->ext_tree, si->zombie_tree, si->ext_node);
 		seq_puts(s, "\nBalancing F2FS Async:\n");
 		seq_printf(s, "  - IO (CP: %4d, Data: %4d, Flush: (%4d %4d), "
-			"Discard: (%4d %4d)) cmd: %4d\n",
+			"Discard: (%4d %4d)) cmd: %4d undiscard:%4u\n",
 			   si->nr_wb_cp_data, si->nr_wb_data,
 			   si->nr_flushing, si->nr_flushed,
 			   si->nr_discarding, si->nr_discarded,
-			   si->nr_discard_cmd);
+			   si->nr_discard_cmd, si->undiscard_blks);
 		seq_printf(s, "  - inmem: %4d, atomic IO: %4d (Max. %4d), "
 			"volatile IO: %4d (Max. %4d)\n",
 			   si->inmem_pages, si->aw_cnt, si->max_aw_cnt,