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

@@ -173,7 +173,7 @@ static void migrateCASchema(SQLite& db, Path schemaPath, AutoCloseFD& lockFd, Ne
             txn.commit();
         }
 
-        writeFile(schemaPath, fmt("%d", nixCASchemaVersion), 0666, true);
+        writeFileAndSync(schemaPath, fmt("%d", nixCASchemaVersion), 0666);
         lockFile(lockFd.get(), ltRead);
     }
 }
@@ -315,7 +315,7 @@ 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) {
@@ -368,7 +368,7 @@ 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

@@ -359,25 +359,44 @@ Generator<Bytes> readFileSource(const Path & path)
 }
 
 
-void writeFile(const Path & path, std::string_view s, mode_t mode, bool sync)
+void writeFile(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);
+
+    /* Close explicitly to propagate the exceptions. */
+    fd.close();
+}
+
+void writeFile(AutoCloseFD & fd, std::string_view s, mode_t mode)
+{
+    assert(fd);
     try {
         writeFull(fd.get(), s);
     } 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 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)
 {
@@ -397,7 +416,7 @@ 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);
 
@@ -414,11 +433,11 @@ 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)
+writeFile(const Path & path, AsyncInputStream & source, mode_t mode)
 try {
     AutoCloseFD fd = openForWrite(path, mode);
 
@@ -436,7 +455,7 @@ 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

@@ -189,11 +189,18 @@ 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);
+void writeFile(const Path & path, std::string_view s, mode_t mode = 0666);
 
-void writeFile(const Path & path, Source & source, mode_t mode = 0666, bool sync = false);
+void writeFile(const Path & path, Source & source, mode_t mode = 0666);
+
+void writeFile(AutoCloseFD & fd, std::string_view s, mode_t mode = 0666);
 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