diff --git a/lib/files.cpp b/lib/files.cpp
index 4a9e11f..f1f0087 100644
--- a/lib/files.cpp
+++ b/lib/files.cpp
@@ -163,6 +163,20 @@ u_int64_t FilesOperation::create_new_inode(u_int64_t parent_inode_number, const
         return -1;
     }
 
+    // Check if file or directory already exists
+    char r_buffer[IO_BLOCK_SIZE] = {0};
+    for (u_int64_t idx=0; idx<inode.size; idx++) {
+        read_datablock(inode, idx, r_buffer);
+        DirectoryEntry ent;
+        for(int i=0;i<=IO_BLOCK_SIZE-64;i+=64){
+            ent.deserialize(r_buffer+i);
+            if (strcmp(ent.file_name, name)==0) {
+                printf("Already exists file or directory with name %s, cannot not create\n", name);
+                return -1;
+            }
+        }
+    }
+
     u_int64_t new_inode_number = 0;
 
     char rw_buffer[IO_BLOCK_SIZE] = {0};
diff --git a/test/layer2_API.cpp b/test/layer2_API.cpp
index 8282ae3..70eff32 100644
--- a/test/layer2_API.cpp
+++ b/test/layer2_API.cpp
@@ -29,7 +29,9 @@ int main(int argc, char *argv[]) {
     u_int64_t f1 = fsop.fischl_mkdir("foo/bar",0);
     u_int64_t f2 = fsop.fischl_mkdir("/doesnt_exist/bar",0);
     u_int64_t f3 = fsop.fischl_mkdir("/test/bar",0);
-    // TODO: guard against creating an existing file or diretory, such as fsop.fischl_mkdir("/test",0)
+    u_int64_t f4 =  fsop.fischl_mkdir("/test",0);
+    u_int64_t f5 =  fsop.fischl_mkdir("/foo/bar",0);
+    u_int64_t f6 =  fsop.fischl_mkdir("/foo/bar/..",0);
 
     // write to files (TODO: fischl_write)
     // read and write to indirect datablocks are not supported yet
@@ -102,4 +104,13 @@ int main(int argc, char *argv[]) {
         assert(inode_number == inode_numbers[i]);
     }
     fsop.printDirectory(file_pressure);
+    std::string newprefix = "/pressure/New";
+    for(int i=0;i<700;i+=2){
+        inode_numbers[i] = fsop.fischl_mkdir((newprefix+std::to_string(i)).c_str(), 0);
+    }
+    for(int i=0;i<700;i+=2){
+        u_int64_t inode_number = fsop.namei((newprefix+std::to_string(i)).c_str());
+        assert(inode_number == inode_numbers[i]);
+    }
+    fsop.printDirectory(file_pressure);
 }
\ No newline at end of file