Return correct disk free/available size when FS is mounted with size = 0

base/sys_info_posix.cc

 // Copyright (c) 2011 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 "base/sys_info.h"
 
 #include <errno.h>
 #include <stddef.h>
 #include <stdint.h>
 #include <string.h>
@@ skipping 62 matching lines @@
     base::internal::LazySysInfoValue<int64_t, AmountOfVirtualMemory>>::Leaky
     g_lazy_virtual_memory = LAZY_INSTANCE_INITIALIZER;
 
 bool GetDiskSpaceInfo(const base::FilePath& path,
                       int64_t* available_bytes,
                       int64_t* total_bytes) {
   struct statvfs stats;
   if (HANDLE_EINTR(statvfs(path.value().c_str(), &stats)) != 0)
     return false;
 
-  if (available_bytes)
-    *available_bytes = static_cast<int64_t>(stats.f_bavail) * stats.f_frsize;
-  if (total_bytes)
-    *total_bytes = static_cast<int64_t>(stats.f_blocks) * stats.f_frsize;
+  // f_blocks is 0 when tmpfs is mounted without any size limit (i.e. size set

[Lei Zhang, 2016/07/16 00:19:12]

You need to check that the file system is tmpfs. The f_blocks == 0 case may not
mean the same thing for other file systems. On Linux, you can use
GetFileSystemType(), but keep in mind the code here is cross-platform.

[Lei Zhang, 2016/07/18 19:05:07]

Basically something like the following, though it may not be 100% correct
because GetFileSystemType() can return FILE_SYSTEM_MEMORY for ramfs and
hugetlbfs as well, and I don't know if the 0 -> unlimited characteristic applies
to those file systems as well. Can you check on that? If not, you'll have just
to put in a specific check for tmpfs here instead.

With the const bool for non-Linux builds, hopefully the compiler can just
optimize it as though this CL never happened.

#if defined(OS_LINUX)
  // On Linux, stats.f_blocks is 0 when tmpfs is mounted without any size limit
  // (i.e. size set to 0).
  FileSystemType fs_type;
  const bool zero_size_means_unlimited = stats.f_blocks == 0 &&
                                         GetFileSystemType(path, &fs_type) &&
                                         fs_type == FILE_SYSTEM_MEMORY;
#else
  const bool zero_size_means_unlimited = false;
#endif

[Sriram, 2016/07/19 23:41:32]

Acknowledged.

[Sriram, 2016/07/19 23:41:32]

Done.

+  // to 0).
+  if (available_bytes) {
+    *available_bytes = (stats.f_blocks == 0) ?
+        std::numeric_limits<int64_t>::max() :
+        static_cast<int64_t>(stats.f_bavail) * stats.f_frsize;
+  }
+
+  if (total_bytes) {
+      *total_bytes = (stats.f_blocks == 0) ?
+          std::numeric_limits<int64_t>::max() :
+          static_cast<int64_t>(stats.f_blocks) * stats.f_frsize;
+  }
   return true;
 }
 
 }  // namespace
 
 namespace base {

[Lei Zhang, 2016/07/18 19:05:07]

If you can move this up to wrap the anonymous namespace, then you don't have to
use base:: to refer to GetFileSystemType().

[Sriram, 2016/07/19 23:41:32]

Done.

 
 #if !defined(OS_OPENBSD)
 int SysInfo::NumberOfProcessors() {
   return g_lazy_number_of_processors.Get().value();
 }
 #endif
 
 // static
 int64_t SysInfo::AmountOfVirtualMemory() {
   return g_lazy_virtual_memory.Get().value();
@@ skipping 58 matching lines @@
   }
   return arch;
 }
 
 // static
 size_t SysInfo::VMAllocationGranularity() {
   return getpagesize();
 }
 
 }  // namespace base