Corrupted data on shared folders

[Fran]

On a Windows XP host, I use a linux guest as local web server, where the /var/www directory is a shared folder (mounted with gid/uid to be accessible by apache). I handle version control with Mercurial.

All has been working fine, until I stumbled upon a bug in version 2.1.4 and 2.2.0 - data on the shared directory is corrupted, while read or written. I can reproduce this consistently, and I have found a minimal* text file that can trigger the bug. ( * if I split the file in two, both the parts will be read correctly )

    fran@inside:/var/www/test$ rm -f .hg
    fran@inside:/var/www/test$ hg init
    fran@inside:/var/www/test$ hg add minfail
    fran@inside:/var/www/test$ hg commit -m "Boom"
    fran@inside:/var/www/test$ hg verify
    checking changesets
    checking manifests
    crosschecking files in changesets and manifests
    checking files
    minfail@0: broken revlog! (index data/minfail.i unknown format 25920)
    warning: orphan revlog 'data/minfail.i'
    1 files, 1 changesets, 0 total revisions
    1 warnings encountered!
    1 integrity errors encountered!
    (first damaged changeset appears to be 0)
    fran@inside:/var/www/test$

The problem is not present if I run mercurial on the host machine, or I copy the files on the virtual machine hard drive. This made me think that Mercurial works fine, but VirtualBox has trouble writing on the shared folder.

The minfail file is just text, more or less 8kB. You can find here attached.

[Fran]

Text file that can be used to reproduce the bug