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 55 matching lines @@
     NOTREACHED();
     return 0;
   }
   return limit.rlim_cur == RLIM_INFINITY ? 0 : limit.rlim_cur;
 }
 
 base::LazyInstance<
     base::internal::LazySysInfoValue<int64_t, AmountOfVirtualMemory>>::Leaky
     g_lazy_virtual_memory = LAZY_INSTANCE_INITIALIZER;
 
+}  // namespace

[Lei Zhang, 2016/07/19 23:45:10]

No, that's not what I meant.

namespace base {

namespace {

// all the existing anonymous bits now no longer needs base::

}  // namespace

// all the existing non-anoynymous bits

}  // namespace base

[Sriram, 2016/07/19 23:58:37]

Done.

+
+namespace base {
+
 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;
+#if defined(OS_LINUX)
+  // On Linux, stats.f_blocks is 0 when memory based file system like tmpfs,
+  // ramfs, or hugetlbfs (all memory file systems). the is mounted without any

[Lei Zhang, 2016/07/19 23:45:10]

So have you checked the ramfs / hugetlbfs behavior w.r.t. size == 0?

[Lei Zhang, 2016/07/19 23:45:10]

typo: "the is mounted"

[Sriram, 2016/07/19 23:58:37]

Yes, See Linux code for:
hugetlbfs - http://lxr.free-electrons.com/source/fs/hugetlbfs/inode.c#L869
/* If no limits set, just report 0 for max/free/used
 * blocks, like simple_statfs() */

For Ramfs: 
http://lxr.free-electrons.com/source/fs/libfs.c#L33
Which uses simple_statfs().

[Sriram, 2016/07/19 23:58:37]

Done.

+  // 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
+
+  if (available_bytes) {
+    *available_bytes = zero_size_means_unlimited ?
+        std::numeric_limits<int64_t>::max() :
+        static_cast<int64_t>(stats.f_bavail) * stats.f_frsize;
+  }
+
+  if (total_bytes) {
+      *total_bytes = zero_size_means_unlimited ?
+          std::numeric_limits<int64_t>::max() :
+          static_cast<int64_t>(stats.f_blocks) * stats.f_frsize;
+  }
   return true;
 }
 
-}  // namespace
-
-namespace base {
-
 #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 57 matching lines @@
   }
   return arch;
 }
 
 // static
 size_t SysInfo::VMAllocationGranularity() {
   return getpagesize();
 }
 
 }  // namespace base