ext4: add a hint for block bitmap corrupt state in mb_groups

If one group is marked as block bitmap corrupted, its free blocks cannot
be used and its free count is also deducted from the global
sbi->s_freeclusters_counter. User might be confused about the absent
free space because we can't query the information about corrupted block
groups except unreliable error messages in syslog. So add a hint to show
block bitmap corrupted groups in mb_groups.
Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20240119061154.1525781-1-yi.zhang@huaweicloud.comSigned-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/mballoc.c

@@ -3059,7 +3059,10 @@ static int ext4_mb_seq_groups_show(struct seq_file *seq, void *v)
 	for (i = 0; i <= 13; i++)
 		seq_printf(seq, " %-5u", i <= blocksize_bits + 1 ?
 				sg.info.bb_counters[i] : 0);
-	seq_puts(seq, " ]\n");
+	seq_puts(seq, " ]");
+	if (EXT4_MB_GRP_BBITMAP_CORRUPT(&sg.info))
+		seq_puts(seq, " Block bitmap corrupted!");
+	seq_puts(seq, "\n");
 
 	return 0;
 }