dm verity: use __ffs and __fls

This patch changes ffs() to __ffs() and fls() to __fls() which don't add
one to the result.

Signed-off-by: Mikulas Patocka <[e-mail]>
Signed-off-by: Alasdair G Kergon <[e-mail]>

drivers/md/dm-verity.c

···
 				goto no_prefetch_cluster;
 
 			if (unlikely(cluster & (cluster - 1)))
-				cluster = 1 << (fls(cluster) - 1);
+				cluster = 1 << __fls(cluster);
 
 			hash_block_start &= ~(sector_t)(cluster - 1);
 			hash_block_end |= cluster - 1;
···
 		r = -EINVAL;
 		goto bad;
 	}
-	v->data_dev_block_bits = ffs(num) - 1;
+	v->data_dev_block_bits = __ffs(num);
 
 	if (sscanf(argv[4], "%u%c", &num, &dummy) != 1 ||
 	    !num || (num & (num - 1)) ||
···
 		r = -EINVAL;
 		goto bad;
 	}
-	v->hash_dev_block_bits = ffs(num) - 1;
+	v->hash_dev_block_bits = __ffs(num);
 
 	if (sscanf(argv[5], "%llu%c", &num_ll, &dummy) != 1 ||
 	    (sector_t)(num_ll << (v->data_dev_block_bits - SECTOR_SHIFT))
···
 	}
 
 	v->hash_per_block_bits =
-		fls((1 << v->hash_dev_block_bits) / v->digest_size) - 1;
+		__fls((1 << v->hash_dev_block_bits) / v->digest_size);
 
 	v->levels = 0;
 	if (v->data_blocks)