libutil: writeFile variant for file descriptors

`writeFile` lose its `sync` boolean flag to make things simpler.

A new `writeFileAndSync` function is created and all call sites are
converted to it.

Change-Id: Ib871a5283a9c047db1e4fe48a241506e4aab9192
Signed-off-by: Raito Bezarius <raito@lix.systems>

lix/libstore/local-store.cc

@@ -224,7 +224,7 @@ void LocalStore::initDB(DBState & state)
     else if (curSchema == 0) { /* new store */
         curSchema = nixSchemaVersion;
         openDB(state, true);
-        writeFile(schemaPath, fmt("%1%", nixSchemaVersion), 0666, true);
+        writeFileAndSync(schemaPath, fmt("%1%", nixSchemaVersion), 0666);
     }
 
     else if (curSchema < nixSchemaVersion) {
@@ -277,7 +277,7 @@ void LocalStore::initDB(DBState & state)
             txn.commit();
         }
 
-        writeFile(schemaPath, fmt("%1%", nixSchemaVersion), 0666, true);
+        writeFileAndSync(schemaPath, fmt("%1%", nixSchemaVersion), 0666);
 
         lockFile(globalLock.get(), ltRead, always_progresses);
     }

lix/libutil/file-system.cc

@@ -358,28 +358,49 @@ Generator<Bytes> readFileSource(const Path & path)
     }(std::move(fd));
 }
 
-void writeFile(const Path & path, std::string_view s, mode_t mode, bool sync, bool allowInterrupts)
+void writeFile(const Path & path, std::string_view s, mode_t mode, bool allowInterrupts)
 {
     AutoCloseFD fd{open(path.c_str(), O_WRONLY | O_TRUNC | O_CREAT | O_CLOEXEC, mode)};
     if (!fd)
         throw SysError("opening file '%1%'", path);
+
+    writeFile(fd, s, mode, allowInterrupts);
+
+    /* Close explicitly to propagate the exceptions. */
+    fd.close();
+}
+
+void writeFile(AutoCloseFD & fd, std::string_view s, mode_t mode, bool allowInterrupts)
+{
+    assert(fd);
     try {
         writeFull(fd.get(), s, allowInterrupts);
     } catch (Error & e) {
-        e.addTrace({}, "writing file '%1%'", path);
+        e.addTrace({}, "writing file '%1%'", fd.guessOrInventPath());
         throw;
     }
-    if (sync)
-        fd.fsync();
-    // Explicitly close to make sure exceptions are propagated.
-    fd.close();
-    if (sync)
-        syncParent(path);
 }
 
-void writeFileUninterruptible(const Path & path, std::string_view s, mode_t mode, bool sync)
+void writeFileUninterruptible(const Path & path, std::string_view s, mode_t mode)
 {
-    writeFile(path, s, mode, sync, false);
+    writeFile(path, s, mode, false);
+}
+
+void writeFileAndSync(const Path & path, std::string_view s, mode_t mode)
+{
+    {
+        AutoCloseFD fd{open(path.c_str(), O_WRONLY | O_TRUNC | O_CREAT | O_CLOEXEC, mode)};
+        if (!fd) {
+            throw SysError("opening file '%1%'", path);
+        }
+
+        writeFile(fd, s, mode);
+        fd.fsync();
+        /* Close explicitly to ensure that exceptions are propagated. */
+        fd.close();
+    }
+
+    syncParent(path);
 }
 
 static AutoCloseFD openForWrite(const Path & path, mode_t mode)
@@ -400,7 +421,7 @@ static void closeForWrite(const Path & path, AutoCloseFD & fd, bool sync)
         syncParent(path);
 }
 
-void writeFile(const Path & path, Source & source, mode_t mode, bool sync)
+void writeFile(const Path & path, Source & source, mode_t mode)
 {
     AutoCloseFD fd = openForWrite(path, mode);
 
@@ -417,11 +438,10 @@ void writeFile(const Path & path, Source & source, mode_t mode, bool sync)
         e.addTrace({}, "writing file '%1%'", path);
         throw;
     }
-    closeForWrite(path, fd, sync);
+    closeForWrite(path, fd, false);
 }
 
-kj::Promise<Result<void>>
-writeFile(const Path & path, AsyncInputStream & source, mode_t mode, bool sync)
+kj::Promise<Result<void>> writeFile(const Path & path, AsyncInputStream & source, mode_t mode)
 try {
     AutoCloseFD fd = openForWrite(path, mode);
 
@@ -439,7 +459,7 @@ try {
         e.addTrace({}, "writing file '%1%'", path);
         throw;
     }
-    closeForWrite(path, fd, sync);
+    closeForWrite(path, fd, false);
     co_return result::success();
 } catch (...) {
     co_return result::current_exception();

lix/libutil/file-system.hh

@@ -190,19 +190,21 @@ Generator<Bytes> readFileSource(const Path & path);
  * Write a string to a file.
  */
 void writeFile(
-    const Path & path,
-    std::string_view s,
-    mode_t mode = 0666,
-    bool sync = false,
-    bool allowInterrupts = true
-);
-void writeFileUninterruptible(
-    const Path & path, std::string_view s, mode_t mode = 0666, bool sync = false
+    const Path & path, std::string_view s, mode_t mode = 0666, bool allowInterrupts = true
 );
+void writeFileUninterruptible(const Path & path, std::string_view s, mode_t mode = 0666);
+void writeFile(const Path & path, Source & source, mode_t mode = 0666);
 
-void writeFile(const Path & path, Source & source, mode_t mode = 0666, bool sync = false);
+void writeFile(
+    AutoCloseFD & fd, std::string_view s, mode_t mode = 0666, bool allowInterrupts = true
+);
 kj::Promise<Result<void>>
-writeFile(const Path & path, AsyncInputStream & source, mode_t mode = 0666, bool sync = false);
+writeFile(const Path & path, AsyncInputStream & source, mode_t mode = 0666);
+
+/**
+ * Write a string to a file and flush the file and its parents direcotry to disk.
+ */
+void writeFileAndSync(const Path & path, std::string_view s, mode_t mode = 0666);
 
 /**
  * Flush a file's parent directory to disk