Use FilesystemProxy in LevelDB ChromiumEnv

This rewrites ChromiumEnv to use the storage::FilesystemProxy
API for all filesystem access. By default it will use unrestricted
instances with direct filesystem access, effectively equivalent to
the status quo. No interesting behavioral or performance changes
are expected here.

This will allow a follow-up CL to implement sandboxing support for
LevelDB by constructing a ChromiumEnv instance over a restricted
FilesystemProxy instance.

Bug: 1052045
Change-Id: Ic23726b3f5abd3f1a322b49827e80dbf424c3de7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2080673
Commit-Queue: Ken Rockot <rockot@google.com>
Reviewed-by: Victor Costan <pwnall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#747584}

third_party/leveldatabase/BUILD.gn

@@ -127,6 +127,7 @@ component("leveldatabase") {
 
   deps = [
     "//base",
+    "//components/services/storage/public/cpp/filesystem",
     "//third_party/crc32c",
     "//third_party/re2",
     "//third_party/snappy",
@@ -162,6 +163,7 @@ static_library("leveldb_static") {
 
   deps = [
     "//base",
+    "//components/services/storage/public/cpp/filesystem",
     "//third_party/crc32c",
     "//third_party/re2",
     "//third_party/snappy",

third_party/leveldatabase/DEPS

@@ -7,4 +7,10 @@ include_rules = [
   '+leveldb',
   '+port',
   '+util',
-]
+]
\ No newline at end of file
+
+specific_include_rules = {
+  'env_chromium\.cc': [
+    '+components/services/storage/public/cpp/filesystem',
+  ],
+}

third_party/leveldatabase/env_chromium.h

@@ -35,6 +35,10 @@ class ProcessMemoryDump;
 }  // namespace trace_event
 }  // namespace base
 
+namespace storage {
+class FilesystemProxy;
+}
+
 namespace leveldb_env {
 
 // These entries map to values in tools/metrics/histograms/histograms.xml. New
@@ -157,11 +161,16 @@ class LEVELDB_EXPORT ChromiumEnv : public leveldb::Env,
                                    public UMALogger,
                                    public RetrierProvider {
  public:
+  using ScheduleFunc = void(void*);
+
+  // Constructs a ChromiumEnv instance with an unrestricted FilesystemProxy
+  // instance that performs direct filesystem access.
   ChromiumEnv();
 
-  typedef void(ScheduleFunc)(void*);
+  // Constructs a ChromiumEnv instance with a custom FilesystemProxy instance.
+  explicit ChromiumEnv(std::unique_ptr<storage::FilesystemProxy> filesystem);
 
-  virtual ~ChromiumEnv();
+  ~ChromiumEnv() override;
 
   bool FileExists(const std::string& fname) override;
   leveldb::Status GetChildren(const std::string& dir,
@@ -195,8 +204,14 @@ class LEVELDB_EXPORT ChromiumEnv : public leveldb::Env,
   void SetReadOnlyFileLimitForTesting(int max_open_files);
 
  protected:
+  // Constructs a ChromiumEnv instance with a local unrestricted FilesystemProxy
+  // instance that performs direct filesystem access.
   explicit ChromiumEnv(const std::string& name);
 
+  // Constructs a ChromiumEnv instance with a custom FilesystemProxy instance.
+  ChromiumEnv(const std::string& name,
+              std::unique_ptr<storage::FilesystemProxy> filesystem);
+
   static const char* FileErrorString(base::File::Error error);
 
  private:
@@ -207,23 +222,6 @@ class LEVELDB_EXPORT ChromiumEnv : public leveldb::Env,
   base::HistogramBase* GetOSErrorHistogram(MethodID method, int limit) const;
   void RemoveBackupFiles(const base::FilePath& dir);
 
-  // File locks may not be exclusive within a process (e.g. on POSIX). Track
-  // locks held by the ChromiumEnv to prevent access within the process.
-  class LockTable {
-   public:
-    bool Insert(const std::string& fname) {
-      leveldb::MutexLock l(&mu_);
-      return locked_files_.insert(fname).second;
-    }
-    bool Remove(const std::string& fname) {
-      leveldb::MutexLock l(&mu_);
-      return locked_files_.erase(fname) == 1;
-    }
-   private:
-    leveldb::port::Mutex mu_;
-    std::set<std::string> locked_files_;
-  };
-
   const int kMaxRetryTimeMillis;
   // BGThread() is the body of the background thread
   void BGThread();
@@ -239,6 +237,8 @@ class LEVELDB_EXPORT ChromiumEnv : public leveldb::Env,
   base::HistogramBase* GetRecoveredFromErrorHistogram(
       MethodID method) const override;
 
+  const std::unique_ptr<storage::FilesystemProxy> filesystem_;
+
   base::FilePath test_directory_;
 
   std::string name_;
@@ -255,7 +255,6 @@ class LEVELDB_EXPORT ChromiumEnv : public leveldb::Env,
   };
   using BGQueue = base::circular_deque<BGItem>;
   BGQueue queue_;
-  LockTable locks_;
   std::unique_ptr<leveldb::Cache> file_cache_;
 };