Why does u-boot always mark a locked block as bad?

I am developing a nand driver for u-boot. I think it works well, but the u-boot environment is not working as expected. Here's what I did for testing:

• Remove the whole nand phrase with a code that is itself encoded, these codes are not related to u-boot. And no bad blocks were found. (Is it possible for nand flash to not have bad blocks?). Here is the code

  void nand_erase(u32 addr)
  {   
      if (addr & (BLOCK_SIZE - 1))
      {
          printf("not block align\n");
          return;
      }
      u32 row = addr / 2048;
  
      nand_select_chip();
      nand_cmd(0x60);
  
      NFADDR = row & 0xFF;            
      NFADDR = (row >> 8) & 0xFF;
      NFADDR = (row >> 16) & 0x07;
  
      nand_cmd(0xD0);
      nand_wait_ready();
  
      nand_cmd(0x70);
      u8 status = nand_read();
      if (status & 0x01)
      {
          printf("block 0x%x is bad", addr);
      }
  
      nand_deselect_chip();
  }
  
        
  
          
          
          
        
  
      

• Run u-boot, it will suggest "bad CRC using default environment".

• Now I use "setenv test 100" and "printenv test", it works well and "saveenv", it also suggests "OK".

• And I use "nand bad", it doesn't show anything.

• Reboot the board and u-boot

• Now he says "readenv () failed using the default environment".

• And I "printenv test" it fails. Then I wrote "nand bad", it shows the bad block in "CONFIG_ENV_OFFSET"

• Then I changed CONFIG_ENV_OFFSET to a different value. and repeat step 1-7. It will show the bad block again in the new CONFIG_ENV_OFFSET file.

I checked my driver, write operation and read operation are good I think. Steps here:

• "nand dump 0" and it shows all 0xff

• "nand write 20000000 0 800" to write memory to nand flash.

• Then "nand dump 0" shows the same values ​​as "md 20000000 100".

So you can see that after saving, the block in CONFIG_ENV_OFFSET will be marked as bad, I really don't know why