ANDROID: Add kconfig to make dm-verity check_at_most_once default enabled

	  of the metadata contents are verified against the key included

	  in the system keyring. Upon success, the underlying verity

	  target is setup.

config DM_ANDROID_VERITY_AT_MOST_ONCE_DEFAULT_ENABLED

	bool "Verity will validate blocks at most once"

   depends on DM_VERITY

   ---help---

	  Default enables at_most_once option for dm-verity

	  Verify data blocks only the first time they are read from the

	  data device, rather than every time.  This reduces the overhead

	  of dm-verity so that it can be used on systems that are memory

	  and/or CPU constrained.  However, it provides a reduced level

	  of security because only offline tampering of the data device's

	  content will be detected, not online tampering.

	  Hash blocks are still verified each time they are read from the

	  hash device, since verification of hash blocks is less performance

	  critical than data blocks, and a hash block will not be verified

	  any more after all the data blocks it covers have been verified anyway.

	  If unsure, say N.

endif # MD

			goto bad;

	}

#ifdef CONFIG_DM_ANDROID_VERITY_AT_MOST_ONCE_DEFAULT_ENABLED

	if (!v->validated_blocks) {

		r = verity_alloc_most_once(v);

		if (r)

			goto bad;

	}

#endif

	v->hash_per_block_bits =

		__fls((1 << v->hash_dev_block_bits) / v->digest_size);