This is a tricky area. It is fine to ask people to call fsync like drunken sailors on ext4 or btrfs - the costs are low; however for ext3 systems an 'fsync' can take many seconds to complete (if one has not been run recently) during which the entire system is un-responsive to I/O and the user feels like everything has crashed/locked. There is a monster kernel I/O bug about this IIRC that never goes anywhere.
So - it is a nuanced issue. We should look at what sequence we are using to re-write that file. IIRC, if we use an atomic 'rename' then we should be guarenteed to get either the old or the new file, and not a zero length one; so prolly we should do that. Though of course this interacts nastily with the tangled locking code (no doubt). Anyhow, I'm sympathetic to the idea of an fsync; except for the still rather widely deployed ext3 world where it is a potential "LibreOffice wedges my machine when I save" problem that is a royal PITA. Of course, for ourselves, we could do the 'fsync' aynchronously; with some horrible 'fsync thread', but ... it's all rather a mess. We'd need to see if 'rename' will work at all with the locking semantics, and whatever odd-ball remote file-systems we're supposed to work with. -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to libreoffice in Ubuntu. https://bugs.launchpad.net/bugs/817326 Title: [Upstream] Previously-saved LibreOffice document lost by power outage (became 0 bytes long) - LibreOffice should call fsync Status in LibreOffice Productivity Suite: Confirmed Status in “libreoffice” package in Ubuntu: Confirmed Bug description: I was working on a document in LibreOffice today 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. ProblemType: Bug DistroRelease: Ubuntu 11.04 Package: libreoffice-core 1:3.3.2-1ubuntu5 ProcVersionSignature: Ubuntu 2.6.38-8.42-generic 2.6.38.2 Uname: Linux 2.6.38-8-generic x86_64 Architecture: amd64 Date: Wed Jul 27 21:37:02 2011 InstallationMedia: Ubuntu 10.04 LTS "Lucid Lynx" - Release amd64 (20100429) ProcEnviron: LANGUAGE=en_US:en LANG=en_US.UTF-8 SHELL=/bin/bash SourcePackage: libreoffice UpgradeStatus: Upgraded to natty on 2011-04-29 (89 days ago) To manage notifications about this bug go to: https://bugs.launchpad.net/df-libreoffice/+bug/817326/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp
