diff --git a/common/dynamic_partition_control_interface.h b/common/dynamic_partition_control_interface.h
index a5be6e1..e6ebe6a 100644
--- a/common/dynamic_partition_control_interface.h
+++ b/common/dynamic_partition_control_interface.h
@@ -167,7 +167,7 @@
       bool is_append = false) = 0;
   // Open a general purpose FD capable to reading and writing to COW. Note that
   // writes must be block aligned.
-  virtual FileDescriptorPtr OpenCowFd(
+  virtual std::unique_ptr<FileDescriptor> OpenCowFd(
       const std::string& unsuffixed_partition_name,
       const std::optional<std::string>&,
       bool is_append = false) = 0;
diff --git a/common/dynamic_partition_control_stub.h b/common/dynamic_partition_control_stub.h
index 515ec7c..5aa4336 100644
--- a/common/dynamic_partition_control_stub.h
+++ b/common/dynamic_partition_control_stub.h
@@ -65,9 +65,10 @@
       const std::optional<std::string>&,
       bool is_append) override;
 
-  FileDescriptorPtr OpenCowFd(const std::string& unsuffixed_partition_name,
-                              const std::optional<std::string>&,
-                              bool is_append = false) override {
+  std::unique_ptr<FileDescriptor> OpenCowFd(
+      const std::string& unsuffixed_partition_name,
+      const std::optional<std::string>&,
+      bool is_append = false) override {
     return nullptr;
   }
 
diff --git a/common/mock_dynamic_partition_control.h b/common/mock_dynamic_partition_control.h
index c6b0b2d..f3a446a 100644
--- a/common/mock_dynamic_partition_control.h
+++ b/common/mock_dynamic_partition_control.h
@@ -36,7 +36,7 @@
   MOCK_METHOD(FeatureFlag, GetVirtualAbCompressionFeatureFlag, (), (override));
   MOCK_METHOD(FeatureFlag, GetVirtualAbFeatureFlag, (), (override));
   MOCK_METHOD(bool, FinishUpdate, (bool), (override));
-  MOCK_METHOD(FileDescriptorPtr,
+  MOCK_METHOD(std::unique_ptr<FileDescriptor>,
               OpenCowFd,
               (const std::string& unsuffixed_partition_name,
                const std::optional<std::string>& source_path,
diff --git a/common/utils.cc b/common/utils.cc
index aa6c6b3..794b832 100644
--- a/common/utils.cc
+++ b/common/utils.cc
@@ -181,7 +181,7 @@
   return true;
 }
 
-bool WriteAll(const FileDescriptorPtr& fd, const void* buf, size_t count) {
+bool WriteAll(FileDescriptor* fd, const void* buf, size_t count) {
   const char* c_buf = static_cast<const char*>(buf);
   ssize_t bytes_written = 0;
   while (bytes_written < static_cast<ssize_t>(count)) {
@@ -218,7 +218,7 @@
   return true;
 }
 
-bool ReadAll(const FileDescriptorPtr& fd,
+bool ReadAll(FileDescriptor* fd,
              void* buf,
              size_t count,
              off_t offset,
@@ -239,7 +239,7 @@
   return true;
 }
 
-bool PReadAll(const FileDescriptorPtr& fd,
+bool PReadAll(FileDescriptor* fd,
               void* buf,
               size_t count,
               off_t offset,
diff --git a/common/utils.h b/common/utils.h
index a33efb2..0f8da22 100644
--- a/common/utils.h
+++ b/common/utils.h
@@ -68,12 +68,15 @@
 bool WriteAll(int fd, const void* buf, size_t count);
 bool PWriteAll(int fd, const void* buf, size_t count, off_t offset);
 
-bool WriteAll(const FileDescriptorPtr& fd, const void* buf, size_t count);
+bool WriteAll(FileDescriptor* fd, const void* buf, size_t count);
+
+constexpr bool WriteAll(const FileDescriptorPtr& fd,
+                        const void* buf,
+                        size_t count) {
+  return WriteAll(fd.get(), buf, count);
+}
 // WriteAll writes data at specified offset, but it modifies file position.
-bool WriteAll(const FileDescriptorPtr& fd,
-              const void* buf,
-              size_t count,
-              off_t off);
+bool WriteAll(FileDescriptorPtr* fd, const void* buf, size_t count, off_t off);
 
 // https://man7.org/linux/man-pages/man2/pread.2.html
 // PWriteAll writes data at specified offset, but it DOES NOT modify file
@@ -97,21 +100,38 @@
     int fd, void* buf, size_t count, off_t offset, ssize_t* out_bytes_read);
 
 // Reads data at specified offset, this function does change file position.
-bool ReadAll(const FileDescriptorPtr& fd,
+
+bool ReadAll(FileDescriptor* fd,
              void* buf,
              size_t count,
              off_t offset,
              ssize_t* out_bytes_read);
 
+constexpr bool ReadAll(const FileDescriptorPtr& fd,
+                       void* buf,
+                       size_t count,
+                       off_t offset,
+                       ssize_t* out_bytes_read) {
+  return ReadAll(fd.get(), buf, count, offset, out_bytes_read);
+}
+
 // https://man7.org/linux/man-pages/man2/pread.2.html
 // Reads data at specified offset, this function DOES NOT change file position.
 // Behavior is similar to linux's pread syscall.
-bool PReadAll(const FileDescriptorPtr& fd,
+bool PReadAll(FileDescriptor* fd,
               void* buf,
               size_t count,
               off_t offset,
               ssize_t* out_bytes_read);
 
+constexpr bool PReadAll(const FileDescriptorPtr& fd,
+                        void* buf,
+                        size_t count,
+                        off_t offset,
+                        ssize_t* out_bytes_read) {
+  return PReadAll(fd.get(), buf, count, offset, out_bytes_read);
+}
+
 // Opens |path| for reading and appends its entire content to the container
 // pointed to by |out_p|. Returns true upon successfully reading all of the
 // file's content, false otherwise, in which case the state of the output