Comment 12 for bug 817326

I am using LibreOffice 3.3.3 on Ubuntu 11.04 amd64 (distro-provided packages). Recently I was working on a document in LibreOffice while my battery was low and so I was frequently saving, which I thought would help me if I lost power. However, when I eventually did lose power and later rebooted, the document had become 0 bytes long. LibreOffice was not able to restore the auto-saved copy either. As a result, I have lost a whole week of notes for one of my courses.

After researching online, it seems that this is caused by the application not calling fsync() (or fdatasync()) when saving files. Due to delayed allocation in modern filesystems, there is no guarantee that the new file's data has actually been written to disk unless the application calls fsync. So if an app writes a new file and replaces the old one with it without fsync'ing the new one first then there is a window of opportunity during which a power failure will result in the loss of BOTH versions of the file. In ext4 this window is also much larger than in ext3.

Theodore Tso blogged about this at http://ldn.linuxfoundation.org/blog-entry/delayed-allocation-and-zero-length-file-problem and http://www.linuxfoundation.org/news-media/blogs/browse/2009/03/don%E2%80%99t-fear-fsync. He strongly recommends to call fsync in this situation.

Please update LibreOffice to fsync() saved files so that other users do not lose their data like I did.

Forwarding upstream from Ubuntu bug at https://bugs.launchpad.net/ubuntu/+source/libreoffice/+bug/817326

You can see evidence of more users encountering this at:
http://ubuntuforums.org/showthread.php?p=11215058
http://user.services.openoffice.org/en/forum/viewtopic.php?f=6&t=39666