arangodb · jsteemann · Jun 11, 2021 · Jun 10, 2021
diff --git a/3rdParty/rocksdb/6.8/env/fs_posix.cc b/3rdParty/rocksdb/6.8/env/fs_posix.cc
@@ -832,7 +832,17 @@ class PosixFileSystem : public FileSystem {
       return IOError("While doing statvfs", fname, errno);
     }
 
-    *free_space = ((uint64_t)sbuf.f_bsize * sbuf.f_bfree);
+    // sbuf.bfree is total free space available to root
+    // sbuf.bavail is total free space available to unprivileged user
+    //  sbuf.bavail <= sbuf.bfree ... pick correct based upon effective user id
+    if (geteuid()) {
+      // non-zero user is unprivileged, or -1 if error.  take more conservative
+      // size
+      *free_space = ((uint64_t)sbuf.f_bsize * sbuf.f_bavail);
+    } else {
+      // root user can access all disk space
+      *free_space = ((uint64_t)sbuf.f_bsize * sbuf.f_bfree);
+    }
     return IOStatus::OK();
   }
 

diff --git a/CHANGELOG b/CHANGELOG
@@ -1,6 +1,11 @@
 devel
 -----
 
+* Backport bugfix from upstream rocksdb repository for calculating the
+  free disk space for the database directory. Before the bugfix, rocksdb
+  could overestimate the amount of free space when the arangod process
+  was run as non-privileged users.
+
 * Add soft coordinator shutdown: This is a new option `soft=true` for the
   DELETE /_admin/shutdown API. Has only meaning for coordinators, otherwise
   ignored. A number of things are allowed to finish but no new things are

diff --git a/arangod/RocksDBEngine/RocksDBEngine.cpp b/arangod/RocksDBEngine/RocksDBEngine.cpp
@@ -479,6 +479,17 @@ void RocksDBEngine::start() {
       FATAL_ERROR_EXIT();
     }
   }
+
+  uint64_t totalSpace;
+  uint64_t freeSpace;
+  if (TRI_GetDiskSpaceInfo(_path, totalSpace, freeSpace).ok() && totalSpace != 0) {
+    LOG_TOPIC("b71b9", DEBUG, arangodb::Logger::ENGINES)
+      << "total disk space for database directory mount: " 
+      << basics::StringUtils::formatSize(totalSpace)
+      << ", free disk space for database directory mount: " 
+      << basics::StringUtils::formatSize(freeSpace)
+      << " (" << (100.0 * double(freeSpace) / double(totalSpace)) << "% free)";
+  }
 
   // options imported set by RocksDBOptionFeature
   auto const& opts = server().getFeature<arangodb::RocksDBOptionFeature>();

diff --git a/lib/Basics/files.cpp b/lib/Basics/files.cpp
@@ -2643,8 +2643,18 @@ arangodb::Result TRI_GetDiskSpaceInfo(std::string const& path,
     TRI_set_errno(TRI_ERROR_SYS_ERROR);
     return {TRI_errno(), TRI_last_error()};
   }
-  totalSpace = static_cast<uint64_t>(stat.f_frsize) * static_cast<uint64_t>(stat.f_blocks);
-  freeSpace = static_cast<uint64_t>(stat.f_frsize) * static_cast<uint64_t>(stat.f_bfree);
+  totalSpace = static_cast<uint64_t>(stat.f_bsize) * static_cast<uint64_t>(stat.f_blocks);
+
+  // sbuf.bfree is total free space available to root
+  // sbuf.bavail is total free space available to unprivileged user
+  // sbuf.bavail <= sbuf.bfree ... pick correct based upon effective user id
+  if (geteuid()) {
+    // non-zero user is unprivileged, or -1 if error. take more conservative size
+    freeSpace = static_cast<uint64_t>(stat.f_bsize) * static_cast<uint64_t>(stat.f_bavail);
+  } else {
+    // root user can access all disk space
+    freeSpace = static_cast<uint64_t>(stat.f_bsize) * static_cast<uint64_t>(stat.f_bfree);
+  }
 #endif
   return {};
 }