diff --git a/guest/authfs/src/common.rs b/guest/authfs/src/common.rs
index 6556fde..fc5af89 100644
--- a/guest/authfs/src/common.rs
+++ b/guest/authfs/src/common.rs
@@ -18,7 +18,7 @@
 pub const CHUNK_SIZE: u64 = 4096;
 
 pub fn divide_roundup(dividend: u64, divisor: u64) -> u64 {
-    (dividend + divisor - 1) / divisor
+    dividend.div_ceil(divisor)
 }
 
 /// Given `offset` and `length`, generates (offset, size) tuples that together form the same length,
diff --git a/guest/authfs/src/fsverity/metadata/metadata.rs b/guest/authfs/src/fsverity/metadata/metadata.rs
index 54d0145..2e78190 100644
--- a/guest/authfs/src/fsverity/metadata/metadata.rs
+++ b/guest/authfs/src/fsverity/metadata/metadata.rs
@@ -131,8 +131,7 @@
     };
 
     // merkle tree is at the next 4K boundary
-    let merkle_tree_offset =
-        (metadata_file.stream_position()? + CHUNK_SIZE - 1) / CHUNK_SIZE * CHUNK_SIZE;
+    let merkle_tree_offset = (metadata_file.stream_position()?).div_ceil(CHUNK_SIZE) * CHUNK_SIZE;
 
     Ok(Box::new(FSVerityMetadata { header, digest, signature, metadata_file, merkle_tree_offset }))
 }
diff --git a/guest/authfs/src/fusefs.rs b/guest/authfs/src/fusefs.rs
index fa4076d..9e49046 100644
--- a/guest/authfs/src/fusefs.rs
+++ b/guest/authfs/src/fusefs.rs
@@ -816,7 +816,7 @@
                     // FUSE ioctl is limited, thus we can't implement fs-verity ioctls without a
                     // kernel change (see b/196635431). Until it's possible, use
                     // xattr to expose what we need as an authfs specific API.
-                    if name != CStr::from_bytes_with_nul(b"authfs.fsverity.digest\0").unwrap() {
+                    if name != c"authfs.fsverity.digest" {
                         return Err(io::Error::from_raw_os_error(libc::ENODATA));
                     }