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

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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.

** Affects: linux (Ubuntu)
     Importance: Undecided
         Status: New

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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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