[Bug 609258] Re: ext4 and xfs wrong data returned on read after write if file size was changed with ftruncate

[Chris Brown]

apport information

** Tags added: apport-collected

** Description changed:

  from: https://bugzilla.kernel.org/show_bug.cgi?id=16165 [^]
  
  > we use the direct async I/O API for file I/O in VirtualBox since 3.2 and got
  > some reports about corrupted guest filesystems. It turned out that only users
  > are affected which disk images are stored on a ext4 filesystem. I could create
  > a testcase which reproduces the error. Further investigation showed that the
  > data corruption happens if ftruncate is used, data is written to the so far
  > unallocated offset and immediately read back. The buffer holding the read data
  > contains only \0 afterwards. The data is there if the file is closed and
  > another program is used to view the file content (less for example). 
  > Everything works if ftruncate is not used.
  
  The test case is in the original bug report, which includes patches
  for ext4 and xfs.
  
  Reproducible: Always  
  Additional Information  This bug is preventing the usage of ext4 and xfs based filesystems with any
  software which uses aio and ftruncate. VirtualBox is is rendered unuseable with
  ext4 and XFS filesystems as a result of this bug.
+ --- 
+ AlsaDevices: Error: command ['ls', '-l', '/dev/snd/'] failed with exit code 2: ls: cannot access /dev/snd/: No such file or directory
+ AplayDevices: aplay: device_list:235: no soundcards found...
+ Architecture: amd64
+ ArecordDevices: arecord: device_list:235: no soundcards found...
+ DistroRelease: Ubuntu 10.10
+ InstallationMedia: Ubuntu 10.10 "Maverick Meerkat" - Alpha amd64 (20100726)
+ Lsusb:
+  Bus 002 Device 002: ID 80ee:0021  
+  Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
+  Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
+ MachineType: innotek GmbH VirtualBox
+ Package: linux (not installed)
+ PciMultimedia:
+  
+ ProcCmdLine: BOOT_IMAGE=/boot/vmlinuz-2.6.35-10-generic root=UUID=38221475-9c13-437f-8af4-3dd073def157 ro quiet splash
+ ProcEnviron:
+  LANG=en_US.utf8
+  SHELL=/bin/bash
+ ProcVersionSignature: Ubuntu 2.6.35-10.15-generic 2.6.35-rc5
+ Regression: No
+ Reproducible: Yes
+ Tags: maverick filesystem needs-upstream-testing
+ Uname: Linux 2.6.35-10-generic x86_64
+ UserGroups: adm admin cdrom dialout lpadmin plugdev sambashare
+ dmi.bios.date: 12/01/2006
+ dmi.bios.vendor: innotek GmbH
+ dmi.bios.version: VirtualBox
+ dmi.modalias: dmi:bvninnotekGmbH:bvrVirtualBox:bd12/01/2006:svninnotekGmbH:pnVirtualBox:pvr1.2:
+ dmi.product.name: VirtualBox
+ dmi.product.version: 1.2
+ dmi.sys.vendor: innotek GmbH

** Attachment added: "BootDmesg.txt"
   http://launchpadlibrarian.net/52568891/BootDmesg.txt

-- 
ext4 and xfs wrong data returned on read after write if file size was changed with ftruncate 
https://bugs.launchpad.net/bugs/609258
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