init: fsync() persistent properties directory after rename()
See the inline comment on why this is necessary.
Test: persistent properties work without errors
Change-Id: I820a193fb032a1845791a55a76390d396678f151
diff --git a/init/persistent_properties.cpp b/init/persistent_properties.cpp
index baa9ad4..3b5a41d 100644
--- a/init/persistent_properties.cpp
+++ b/init/persistent_properties.cpp
@@ -31,10 +31,11 @@
#include "util.h"
+using android::base::Dirname;
using android::base::ReadFdToString;
using android::base::StartsWith;
-using android::base::WriteStringToFd;
using android::base::unique_fd;
+using android::base::WriteStringToFd;
namespace android {
namespace init {
@@ -191,6 +192,18 @@
unlink(temp_filename.c_str());
return Error(saved_errno) << "Unable to rename persistent property file";
}
+
+ // rename() is atomic with regards to the kernel's filesystem buffers, but the parent
+ // directories must be fsync()'ed otherwise, the rename is not necessarily written to storage.
+ // Note in this case, that the source and destination directories are the same, so only one
+ // fsync() is required.
+ auto dir = Dirname(persistent_property_filename);
+ auto dir_fd = unique_fd{open(dir.c_str(), O_DIRECTORY | O_RDONLY)};
+ if (dir_fd < 0) {
+ return ErrnoError() << "Unable to open persistent properties directory for fsync()";
+ }
+ fsync(dir_fd);
+
return {};
}