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While the design of ext3 in the regard to this bug might be considered accidental, it would be wise to attempt to carry it over to ext4 in order to go 'above and beyond' POSIX in compatibility with previous behaviour. Specifically, truncation of a file needs to be made a regular write operation so that it would be cached with other write operations and flushed to disk in a regular batch. Given the following code: 1.a) open and read file ~/.kde/foo/bar/baz 1.b) fd = open("~/.kde/foo/bar/baz", O_WRONLY|O_TRUNC|O_CREAT) --- this truncates the file 1.c) write(fd, buf-of-new-contents-of-file, size-of-new-contents-of-file) 1.d) close(fd) Assuming that less than 30 seconds pass between 1.b and 1.c, these two operations must be executed at the same write cycle without allowing a significant window of opportunity for major data loss. 2.a) open and read file ~/.kde/foo/bar/baz 2.b) fd = open("~/.kde/foo/bar/baz.new", O_WRONLY|O_TRUNC|O_CREAT) 2.c) write(fd, buf-of-new-contents-of-file, size-of-new-contents-of-file) 2.d) close(fd) 2.e) rename("~/.kde/foo/bar/baz.new", "~/.kde/foo/bar/baz") It is even clearer here - why would the rename operation change the destination file before the previous operations are completed? It should not - the rename must be an atomic operation, even if POSIX does not demand it. This is an expected behaviour for extN filesystem and ext4 needs to document and honor that. I understand that a program can not be certain that data will reach the disk unless some sort of fsync() is called. But destroying old data and then delaying writing the new version _is_ an ext4 bug, regardless of what POSIX says. And as a sidenote - maybe programmers feel differently, but system administrators much prefer to have a bunch of small text files that we can edit with text editors and all kinds of scripts instead of SQL database stores for application configuration. Configuration registry is a cool principle, but a horrible practice even in bast implementations. -- Ext4 data loss https://bugs.launchpad.net/bugs/317781 You received this bug notification because you are a member of eCryptfs, which is subscribed to ecryptfs-utils in ubuntu. Status in “ecryptfs-utils” source package in Ubuntu: Invalid Status in “linux” source package in Ubuntu: Confirmed Status in ecryptfs-utils in Ubuntu Jaunty: Invalid Status in linux in Ubuntu Jaunty: Confirmed Bug description: I recently installed Kubuntu Jaunty on a new drive, using Ext4 for all my data. The first time i had this problem was a few days ago when after a power loss ktimetracker's config file was replaced by a 0 byte version . No idea if anything else was affected.. I just noticed ktimetracker right away. Today, I was experimenting with some BIOS settings that made the system crash right after loading the desktop. After a clean reboot pretty much any file written to by any application (during the previous boot) was 0 bytes. For example Plasma and some of the KDE core config files were reset. Also some of my MySQL databases were killed... My EXT4 partitions all use the default settings with no performance tweaks. Barriers on, extents on, ordered data mode.. I used Ext3 for 2 years and I never had any problems after power losses or system crashes. Jaunty has all the recent updates except for the kernel that i don't upgrade because of bug #315006 ProblemType: Bug Architecture: amd64 DistroRelease: Ubuntu 9.04 NonfreeKernelModules: nvidia Package: linux-image-2.6.28-4-generic 2.6.28-4.6 ProcCmdLine: root=UUID=81942248-db70-46ef-97df-836006aad399 ro rootfstype=ext4 vga=791 all_generic_ide elevator=anticipatory ProcEnviron: LANGUAGE= LANG=en_US.UTF-8 SHELL=/bin/bash ProcVersionSignature: Ubuntu 2.6.28-4.6-generic SourcePackage: linux
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