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

base/sys_info_posix.cc

Index: base/sys_info_posix.cc
diff --git a/base/sys_info_posix.cc b/base/sys_info_posix.cc
index 5d1c450139a575705c3c5046ed32c565e4b5e404..9f110c3cd6928477505232f304ce2ad216ac6d25 100644
--- a/base/sys_info_posix.cc
+++ b/base/sys_info_posix.cc
@@ -80,10 +80,19 @@ bool GetDiskSpaceInfo(const base::FilePath& path,
   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;
 }