Is rename() without fsync() safe?

Question

Is it safe to call rename(tmppath, path) without calling fsync(tmppath_fd) first?

I want the path to always point to a complete file. I car

Answer 1

If you only care about ext4 and not ext3 then I'd recommend using fsync on the new file before doing the rename. The fsync performance on ext4 seems to be much better than on ext3 without the very long delays. Or it might be the fact that writeback is the default mode (at least on my Linux system).

If you only care that the file is complete and not which file is named in the directory then you only need to fsync the new file. There's no need to fsync the directory too since it will point to either the new file with its complete data, or the old file.