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..7db6fd15d3a3787530bc93b64c963a6a45c5fa00 100644
--- a/base/sys_info_posix.cc
+++ b/base/sys_info_posix.cc
@@ -28,6 +28,10 @@
 #include <sys/statvfs.h>
 #endif
 
+#if defined(OS_LINUX)
+#include <linux/magic.h>
+#endif
+
 namespace {
 
 #if !defined(OS_OPENBSD)
@@ -73,6 +77,15 @@ base::LazyInstance<
     base::internal::LazySysInfoValue<int64_t, AmountOfVirtualMemory>>::Leaky
     g_lazy_virtual_memory = LAZY_INSTANCE_INITIALIZER;
 
+#if defined(OS_LINUX)
+bool IsStatsZeroIfUnlimited(unsigned long int fsid) {
+  // On Linux, stats.f_blocks is 0 when memory based file system (like tmpfs,
+  // ramfs, or hugetlbfs), is mounted without any size limit (i.e. size set to
+  // 0).
+  return fsid == TMPFS_MAGIC || fsid == HUGETLBFS_MAGIC || fsid == RAMFS_MAGIC;
+}
+#endif
+
 bool GetDiskSpaceInfo(const base::FilePath& path,
                       int64_t* available_bytes,
                       int64_t* total_bytes) {
@@ -80,10 +93,26 @@ 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;
+#if defined(OS_LINUX)
+  const bool zero_size_means_unlimited =
+      stats.f_blocks == 0 && IsStatsZeroIfUnlimited(stats.f_fsid);

[Lei Zhang, 2016/08/01 21:30:55]

Are you sure f_fsid is the right field to check? Locally I ran this program:

#include <stdio.h>
#include <sys/statvfs.h>

int main() {
  struct statvfs stats;
  statvfs("/run/shm/foo", &stats);
  printf("%lu\n", stats.f_fsid);
  return 0;
}

and it returned 0, for a file foo that exists on /run/shm, which is tmpfs.

[Sriram, 2016/08/02 00:03:24]

You are right - I misunderstood the man page and f_fsid is not the same as
f_type and f_type is not exposed via statvfs() call. Switched to statfs() as all
values needed here is available.

+#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;
 }