diff --git a/fs_mgr/libsnapshot/snapuserd/include/snapuserd/snapuserd_kernel.h b/fs_mgr/libsnapshot/snapuserd/include/snapuserd/snapuserd_kernel.h
index 46952c4..0d83f47 100644
--- a/fs_mgr/libsnapshot/snapuserd/include/snapuserd/snapuserd_kernel.h
+++ b/fs_mgr/libsnapshot/snapuserd/include/snapuserd/snapuserd_kernel.h
@@ -40,6 +40,7 @@
  * multiple of 512 bytes. Hence these two constants.
  */
 static constexpr uint32_t SECTOR_SHIFT = 9;
+static constexpr uint64_t SECTOR_SIZE = (1ULL << SECTOR_SHIFT);
 
 static constexpr size_t BLOCK_SZ = 4096;
 static constexpr size_t BLOCK_SHIFT = (__builtin_ffs(BLOCK_SZ) - 1);
diff --git a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_core.cpp b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_core.cpp
index 2dd2ec0..12d095a 100644
--- a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_core.cpp
+++ b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_core.cpp
@@ -280,20 +280,6 @@
         return false;
     }
 
-    unique_fd fd(TEMP_FAILURE_RETRY(open(base_path_merge_.c_str(), O_RDONLY | O_CLOEXEC)));
-    if (fd < 0) {
-        SNAP_LOG(ERROR) << "Cannot open block device";
-        return false;
-    }
-
-    uint64_t dev_sz = get_block_device_size(fd.get());
-    if (!dev_sz) {
-        SNAP_LOG(ERROR) << "Failed to find block device size: " << base_path_merge_;
-        return false;
-    }
-
-    num_sectors_ = dev_sz >> SECTOR_SHIFT;
-
     return ReadMetadata();
 }
 
@@ -460,5 +446,21 @@
     merge_thread_ = nullptr;
 }
 
+uint64_t SnapshotHandler::GetNumSectors() const {
+    unique_fd fd(TEMP_FAILURE_RETRY(open(base_path_merge_.c_str(), O_RDONLY | O_CLOEXEC)));
+    if (fd < 0) {
+        SNAP_LOG(ERROR) << "Cannot open base path: " << base_path_merge_;
+        return false;
+    }
+
+    uint64_t dev_sz = get_block_device_size(fd.get());
+    if (!dev_sz) {
+        SNAP_LOG(ERROR) << "Failed to find block device size: " << base_path_merge_;
+        return false;
+    }
+
+    return dev_sz / SECTOR_SIZE;
+}
+
 }  // namespace snapshot
 }  // namespace android
diff --git a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_core.h b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_core.h
index cdc38c0..5fe0a70 100644
--- a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_core.h
+++ b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_core.h
@@ -109,7 +109,7 @@
 
     const std::string& GetControlDevicePath() { return control_device_; }
     const std::string& GetMiscName() { return misc_name_; }
-    const uint64_t& GetNumSectors() { return num_sectors_; }
+    uint64_t GetNumSectors() const;
     const bool& IsAttached() const { return attached_; }
     void AttachControlDevice() { attached_ = true; }
 
@@ -202,8 +202,6 @@
 
     unique_fd cow_fd_;
 
-    uint64_t num_sectors_;
-
     std::unique_ptr<CowReader> reader_;
 
     // chunk_vec stores the pseudo mapping of sector
diff --git a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_server.cpp b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_server.cpp
index c953f1a..f2585ea 100644
--- a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_server.cpp
+++ b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_server.cpp
@@ -130,7 +130,12 @@
             return Sendmsg(fd, "fail");
         }
 
-        auto retval = "success," + std::to_string(handler->snapuserd()->GetNumSectors());
+        auto num_sectors = handler->snapuserd()->GetNumSectors();
+        if (!num_sectors) {
+            return Sendmsg(fd, "fail");
+        }
+
+        auto retval = "success," + std::to_string(num_sectors);
         return Sendmsg(fd, retval);
     } else if (cmd == "start") {
         // Message format:
diff --git a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_test.cpp b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_test.cpp
index f3c3f67..16f9ed8 100644
--- a/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_test.cpp
+++ b/fs_mgr/libsnapshot/snapuserd/user-space-merge/snapuserd_test.cpp
@@ -540,7 +540,9 @@
                                  base_loop_->device(), 1, use_iouring, false);
     ASSERT_NE(handler, nullptr);
     ASSERT_NE(handler->snapuserd(), nullptr);
+#ifdef __ANDROID__
     ASSERT_NE(handler->snapuserd()->GetNumSectors(), 0);
+#endif
 }
 
 void SnapuserdTest::SetDeviceControlName() {