[NaCl SDK] Add some more logging to nacl_io.

native_client_sdk/src/libraries/nacl_io/kernel_object.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "nacl_io/kernel_object.h"
 
 #include <assert.h>
 #include <errno.h>
 #include <fcntl.h>
 #include <pthread.h>
 
 #include <algorithm>
 #include <map>
 #include <string>
 #include <vector>
 
 #include "nacl_io/filesystem.h"
 #include "nacl_io/kernel_handle.h"
+#include "nacl_io/log.h"
 #include "nacl_io/node.h"
 
 #include "sdk_util/auto_lock.h"
 #include "sdk_util/ref_object.h"
 #include "sdk_util/scoped_ref.h"
 
 namespace nacl_io {
 
 KernelObject::KernelObject() {
   cwd_ = "/";
 }
 
 KernelObject::~KernelObject() {};
 
 Error KernelObject::AttachFsAtPath(const ScopedFilesystem& fs,
                                    const std::string& path) {
   std::string abs_path = GetAbsParts(path).Join();
 
   AUTO_LOCK(fs_lock_);
-  if (filesystems_.find(abs_path) != filesystems_.end())
+  if (filesystems_.find(abs_path) != filesystems_.end()) {
+    LOG_ERROR("Can't mount at %s, it is already mounted.", path.c_str());
     return EBUSY;
+  }
 
   filesystems_[abs_path] = fs;
   return 0;
 }
 
 Error KernelObject::DetachFsAtPath(const std::string& path,
                                    ScopedFilesystem* out_fs) {
   std::string abs_path = GetAbsParts(path).Join();
 
   AUTO_LOCK(fs_lock_);
   FsMap_t::iterator it = filesystems_.find(abs_path);
-  if (filesystems_.end() == it)
+  if (filesystems_.end() == it) {
+    LOG_TRACE("Can't unmount at %s, nothing is mounted.", path.c_str());
     return EINVAL;
+  }
 
   // It is only legal to unmount if there are no open references
-  if (it->second->RefCount() != 1)
+  if (it->second->RefCount() != 1) {
+    LOG_TRACE("Can't unmount at %s, refcount is != 1.", path.c_str());
     return EBUSY;
+  }
 
   *out_fs = it->second;
 
   filesystems_.erase(it);
   return 0;
 }
 
 // Uses longest prefix to find the filesystem for the give path, then
 // acquires the filesystem and returns it with a relative path.
 Error KernelObject::AcquireFsAndRelPath(const std::string& path,
@@ skipping 180 matching lines @@
   AUTO_LOCK(handle_lock_);
 
   handle_map_[fd].handle.reset(NULL);
   free_fds_.push_back(fd);
 
   // Force lower numbered FD to be available first.
   std::push_heap(free_fds_.begin(), free_fds_.end(), std::greater<int>());
 }
 
 }  // namespace nacl_io